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| MOPC002 | Benchmark of Space Charge Simulations and Comparison with Experimental Results for High Intensity, Low Energy Accelerators | space-charge, emittance, linac, SNS | 164 | ||
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge. |
Space charge effects are a major contributor to beam halo and emittance growth leading to beam loss in high intensity, low energy accelerators. As future accelerators strive towards unprecedented levels of beam intensity and beam loss control, a more comprehensive understanding of space charge effects is required. A wealth of simulation tools have been developed for modeling beams in linacs and rings, and with the growing availability of high-speed computing systems, computationally expensive problems that were inconceivable a decade ago are now being handled with relative ease. This has opened the field for realistic simulations of space charge effects, including detailed benchmarks with experimental data. A great deal of effort is being focused in this direction, and several recent benchmark studies have produced remarkably successful results. This paper reviews the achievements in space charge benchmarking in the last few years, and discusses the challenges that remain. |
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| MOPC003 | Benchmarking of Simulation Codes Based on the Montague Resonance in the CERN Proton Synchrotron | lattice, emittance, resonance, focusing | 330 | ||
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Experimental data on emittance exchange by the space charge driven ‘‘Montague resonance'' have been obtained at the CERN Proton Synchrotron in 2002-04 as a function of the working point. These data are used to advance the benchmarking of major simulation codes (ACCSIM, IMPACT, MICROMAP, ORBIT, SIMBAD, SIMPSONS, SYNERGIA) currently employed world-wide in the design or performance improvement of high intensity circular accelerators. In this paper we summarize the experimental findings and compare them with the first three steps of simulation results of the still progressing work.
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| MOPC005 | Chromaticity and Impedance Effect on the Transverse Motion of Longitudinal Bunch Slices in the Tevatron | synchrotron, impedance, damping, beam-losses | 455 | ||
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Funding: Operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the U.S. Department of Energy. |
The Transverse turn-by-turn evolution of a bunch slice are examined considering chromatic and impedence effects. A quasi-analytical approximation is developed using perturbative expansion of Hills equation with a wake field. This approximation is compared to turn-by-turn measurements taken in the Tevatron and from this linear and second order chomaticity, and Impedence are calculated as well as beam stability thresholds. |
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| MOPC006 | Simulations and Experiments of Beam-Beam Effects in e+e- Storage Rings | luminosity, positron, electron, damping | 520 | ||
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Funding: Work partially supported by the Department of Energy under Contract No. DE-AC02-76SF00515. |
Over the past decade, extensive simulations of beam-beam effects in positron-electron collliders, based on the particle-in-cell method, were developed to explain many complex experimental observations. Recently, such simulations were used to predict the future luminosity performance of e+e- colliders. Some predictions have been proven to be correct in the existing accelerators. In this paper, many effects such as dynamic beta, beam-beam limit, crossing angle, parasitic collisions, betatron spectrum, and beam-beam lifetime, will be reviewed from the viewpoints of both simulation and experiment. Whenever possible, direct comparisons between the predictions of the simulation and the corresponding experimental results will be provided. |
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| MOPC007 | Anisotropy-Driven Instability in Intense Charged Particle Beams | betatron, plasma, focusing, dipole | 558 | ||
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Funding: Research supported by the U.S. Department of Energy. |
In electrically neutral plasmas with strongly anisotropic distribution functions, free energy is available to drive different collective instabilities such as the electrostatic Harris instability and the transverse electromagnetic Weibel instability. Such anisotropies develop naturally in particle accelerators and may lead to a detoriation of beam quality. We have generalized the analysis of the classical Harris and Weibel instabilities to the case of a one-component intense charged particle beam with anisotropic temperature including the important effects of finite transverse geometry and beam space-charge. For a long costing beam, the delta-f particle-in-cell code BEST and the eighenmode code bEASt have been used to determine detailed 3D stability properties over a wide range of temperature anisotropy and beam intensity. A theoretical model is developed which describes the essential features of the linear stage of these instabilities. Both, the simulations and analytical theory, clearly show that moderately intense beams are linearly unstable to short-wavelength perturbations, provided the ratio of the longitudinal temperature to the transverse temperature is smaller than some threshold value. |
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| MOPC009 | Experiments on LHC Long-Range Beam-Beam Compensation and Crossing Schemes at the CERN SPS in 2004 | emittance, dynamic-aperture, resonance, hadron | 686 | ||
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Experiments with two prototype long-range beam-beam compensators (current-carrying wires) during the 2004 CERN SPS run explored the efficiency of a proposed long-range beam-beam compensation for the LHC. In addition, the SPS compensators were also used to 'simulate' the effect of different planes of crossing at two LHC interaction points. We present the experimental results and compare them with computer simulations.
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| MPPE002 | Beam Propagation in Misaligned Magnetic Elements: A MatLab Based Code | quadrupole, electron | 826 | ||
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Funding: Fundacao de Amparo a Pesquisa do Estado de Sao Paulo - FAPESP Conselho Nacional de Desenvolvimento Cientifico e Tecnologico - CNPq. |
We present a method to calculate kinematical parameters of a beam subject to a misaligned magnetic element. The procedure consists in transforming the kinematical parameters of the beam to the reference frame in which the magnetic element is aligned, propagating the beam through the element, and transforming back to the original frame. This is done using rotation matrices around the X-, Y-, and Z-axes. These matrices are not Lorentz invariant, so the rotations must be performed in a reference frame where the beam is at rest. We describe the transformation matrices, present a MatLab based code that uses this method to propagate up to 100 particles trough a misaligned quadrupole, and show some graphical outputs of the code. |
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| MPPE003 | Monte Carlo Simulations of Thin Internal Target Scattering In CELSIUS | target, scattering, electron, proton | |||
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In the practical operation of the storage ring CELSIUS with the hydrogen pellet target, we simetimes observe a cooling phenomenon in the longitudinal phase space, that is, the circulating beam's phase space gets shrunk instead of blown up. This phenomenon occurs independently on the electron cooling. In this paper, we aim to investigate and interpret this phenomenon as well as the beam lifetime in the presence of hydrogen pellet target with and without rf and with and without electron cooling in CELSIUS using Monte Carlo simulations.
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| MPPE004 | Evaluation of Nonlinear Effects in the 3GeV Rapid Cycling Synchrotron of J-PARC | resonance, dipole, sextupole, multipole | 916 | ||
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In order to accelerate an ultra-high intense beam with small particle losses, the 3GeV Rapid Cycling Synchrotron (RCS) of J-PARC, which is being constructed at JAERI, has a large acceptance. In this case the nonlinearity associated with the motion of particles at large amplitude and large momentum deviation plays a significant role. The sources of nonlinear magnetic fields in RCS are mainly connected with the fringe of the main dipole and quadrupole magnets and with the sextupole magnets used for the linear chromaticity correction. In this paper, we will present simulation results including such nonlinear effects. In addition, the possible correction scheme for the induced transverse resonances will be discussed.
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| MPPE007 | Problems of Conservative Integration in Beam Physics | 1087 | |||
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In this paper an approach to conservative integration methods development is discussed. This problem is very important for beam physics: from beam line synthesis up to long time evolution simulation. This approach is based on a Lie algebra technique. On the first step we find a special form of decomposition for a Lie map, describing the system under study. On the second step a researcher finds exact solutions for some classes of hamiltonians in symbolic forms. These steps allows forming an integration scheme, which have a desired symplectic property. The additional invariant and symmetry properties can be included using dynamical invariants conception.
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| MPPE008 | Synthesis of Beam Lines with Necessary Properties | quadrupole, focusing, target, octupole | 1096 | ||
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In this paper a new approach to the problem of synthesis of beam lines is discussed. Usually this problem can be overcome by the use of numerical simulation and optimal control theory methods. But this results in sufficiently great number of variable parameters and functions. Obviously, that this degrades quality of a modeling procedure. The suggested approach is demonstrated on a problem of a microprobe design problem. Essence of the problem is that necessary to design a high precision focusing system which satisfies some additional conditions. For solution of this problem we use an algebraic treatment based on Lie algebraic methods and computer algebra techniques. Using the symmetry ideology this approach allows rewriting beam properties to enough simple conditions for control parameters and functions. This leads a set of desired solutions and show results in some most suitable form. Moreover, this approach decreases the number of variable parameters.
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| MPPE009 | 2003-2004 Nonlinear Optics Measurements and Modeling for the CERN SPS | optics, dipole, multipole, quadrupole | 1171 | ||
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In 2003 and 2004 nonlinear chromaticity, amplitude detuning, chromatic phase advance, resonance driving terms and off-energy orbits were measured in the CERN SPS at 14 GeV/c and 26 GeV/c, respectively. From the nonlinear chromaticity, the SPS optics model has been updated, by adjusting the strength of nonlinear field errors in dipoles and quadrupoles. Furthermore, we have added to the model the effect of the displacement of all main bends and the voluntary misalignments of all the other elements of the machine. We compare the field errors with those founded in 2002, 2001 and 2000. The tune shifts with transverse amplitude, driving terms, etc., predicted by this nonlinear optics model are compared with direct measurements.
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| MPPE011 | Expected Emittance Growth and Beam Tail Repopulation from Errors at Injection into the LHC | emittance, injection, betatron, coupling | 1266 | ||
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The preservation of the transverse emittance of the proton beam at injection into the LHC is crucial for luminosity performance. The population of the beam tails is also important for beam losses and collimation. The transfer and injection process is particularly critical in this respect, and several effects can contribute to the expected emittance increase and tail repopulation, like optical and geometrical mismatch, injection offsets and coupling, etc. The various effects are described, together with the tolerance limits on the parameters, and the expected contributions evaluated analytically where possible. The emittance growth and tail distributions are also simulated numerically using realistic errors. The implications for the tolerances on the matching of the transfer lines are discussed.
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| MPPE013 | High Precision Measurement of Muon Beam Emittance Reduction in MICE | emittance, factory, background, scattering | 1330 | ||
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Muon ionization cooling, an essential ingredient of a neutrino factory, will be demonstrated for the first time by the MICE experiment. The central part of MICE consists of a short section of a neutrino factory cooling channel and the emittance reduction achieved in this experiment is quite modest, 10% to 15%. In order to extrapolate the performance of a full cooling channel from these values, it is crucial for MICE to achieve an emittance measurement accuracy of 10-3 absolute. So far, beam emittance has never been measured with such a high level of precision and normailzed emittance in its present definition is not even conserved to 10-3 in the absence of dissipative forces. We present an improved definition of beam emittance and the requirements and constraints on MICE beam optics and spectrometers that are necessary to achieve the 10-3 level of accuracy.
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| MPPE024 | Failure Modes Analysis for the MSU-RIA Driver Linac | linac, lattice, emittance, focusing | 1868 | ||
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Previous end-to-end beam dynamics simulation studies* using experimentally-based input beams including alignment and rf errors and variation in charge-stripping foil thickness have indicated that the Rare Isotope Accelerator (RIA) driver linac proposed by MSU has adequate transverse and longitudinal acceptances to accelerate light and heavy ions to final energies of at least 400 MeV/u with beam powers of 100 to 400 kW. During linac operation, equipment loss due to, for example, cavity contamination, availability of cryogens, or failure of rf or power supply systems, will lead to at least a temporary loss of some of the cavities and focusing elements. To achieve high facility availability, each segment of the linac should be capable of adequate performance even with failed elements. Beam dynamics studies were performed to evaluate the linac performance under various scenarios of failed cavities and focusing elements with proper correction schemes, in order to prove the flexibility and robustness of the driver linac lattice design. The result of these beam dynamics studies will be presented.
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*X. Wu, "End-to-End Beam Simulations for the MSU RIA Driver Linac," Proceedings of the XXII Linac Conference, Lubeck, Germany, August 2004. |
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| MPPE028 | Non Linear Error Analysis from Orbit Measurements in SPS and RHIC | sextupole, interaction-region, scattering, resonance | 2012 | ||
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Funding: U.S. Department of Energy and Colciencias. |
Recently, an "action and phase" analysis of SPS orbits measurements proved to be sensitive to sextupole components intentionally activated at specific locations in the ring. In this paper we attempt to determine the strenght of such sextupoles from the measured orbits and compare them with the set values. Action and phase analysis of orbit trayectories generated by RHIC models with non linearities will also be presented and compare with RHIC experiments. |
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| MPPE030 | Comparison of Off-Line IR Bump and Action-Angle Kick Minimization | sextupole, octupole, resonance, interaction-region | 2116 | ||
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Funding: Work supported by U.S. DOE under contract No. DE-AC02-98CH10886. |
The interaction region bump (IR bump) nonlinear correction method has been used for the sextupole and octupole field error on-line corrections in the Relativistic Heavy Ion Collider (RHIC). Some differences were found for the sextupole and octupole corrector strengths between the on-line IR bump correction and the predictions from the action-angle kick minimization. In this report we compare the corrector strengths from these two methods based on the RHIC Blue ring lattice with the IR nonlinear modeling. The comparison confirms the differences between resulting corrector strengths. And the reason for the differences is found and discussed. It is followed by a further discussion of the operational IR bump applications to the octupole, and skew sextupole and skew quadrupole field error corrections. |
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| MPPE031 | Simulation of Resonance Streaming at the eRHIC Electron Storage Ring | electron, damping, luminosity, background | 2215 | ||
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Funding: Work performed under the auspices of the U.S. Department of Energy. |
To estimate electron beam lifetime and detector background at the future electron-ion collider eRHIC, knowledge of the electron beam halo region is essential. Simulations have been performed to determine the deviation of the transverse beam profile from a Gaussian distribution. |
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| MPPE036 | Characterization of the Chaotic or Regular Nature of Dynamical Orbits: A New, Fast Method | 2449 | |||
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A new method of characterization of the regular or chaotic nature of dynamical orbits is introduced. It takes advantage of both morphological and dynamical properties of orbits, and can be applied to systems of all degrees of freedom. The new technique has been designed to analyze time-independent, time-dependent and N-body systems. It can provide straightforward information about the transition of orbits from regular to chaotic and vice versa, which can be found in time-dependent regimes. Equally important is the distinction it can make in time-independent regimes between sticky and wildly chaotic epochs during the evolution of chaotic orbits. Its most important advantage over the existing methods is, that it characterizes an orbit using information from a very small number of orbital periods. For these reasons the new method is extremely promising to be useful and effective in a broad spectrum of disciplines.
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| MPPE040 | Efficient Modeling of Nonlinear Beam Optics Using Parametric Model Independent Analysis | lattice, optics, quadrupole, beam-transport | |||
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Funding: Research supported by DOE grant number: DE-FG02-04ER86225. |
Based on precision beam orbit measurements, Model Independent Analysis(MIA) has been used successfully to build a computer model that matches the linear optics of the real accelerator. We report a parametric extension of MIA that will allow efficient modeling of the nonlinear beam optics to account for energy dispersions. A simulation study is presented where the nonlinear dependency of lattice parameters on beam energy is captured by constrained training of a universal nonlinear approximator. These parametric nonlinear models of beam optics are easy to construct, diagnose, and modify. They can be very useful for more accurate model predicted beam operation and control. |
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| MPPE043 | The Status of Optics Design and Beam Dynamics Study in J-PARC RCS | injection, beam-losses, extraction, space-charge | 2759 | ||
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The 3GeV RCS at J-PARC is designed to provide proton beam of 3GeV and a goal of output beam power is 1MW. The beam commissioning starts on May 2007. At present, more qualitative studies concerning beam dynamics are in progress: core beam handlings, halo beam handlings, instabilities and so on. In this paper, the RCS optics design and the present status of beam dynamics studies are summarized.
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| MPPE048 | Beam Based Alignment of the LHC Transfer Line Collimators | alignment, beam-losses, injection, proton | 3034 | ||
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At LHC injection energy the aperture available in the transfer lines and in the LHC is small and the intensities of the injected beams are an order of magnitude above the damage level. The setting of protection elements such as the transfer line collimators is therefore very critical; mechanical and optical tolerances must be taken into account to define the nominal setting. Being able to measure and control the collinearity of the collimator jaws with the beam relaxes the requirement on the settings considerably. A method to measure angular misalignment of the collimator jaws in the transfer line based on a transmission measurement is discussed. Simulations have been made and are compared with the results of an alignment test performed with beam during the 2004 commissioning of the transfer line TI 8.
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| MPPE051 | Phase Trombone Program Migration for the Recycler at Fermilab | quadrupole, power-supply | 3135 | ||
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In the Recycler Ring, a phase trombone is used to control tunes. 9 pairs of independently power supplied adjustable quadruples are located in RR-60 straight section. They are segmented into 5 families currently to maintain a symmetrical structure. By adjusting these circuits, a tune variation of up to ±0.5 units is attainable. These adjustments are coordinated in such a way that the Twiss parameters at the ends of the straight section keep unchanged. A new phase trombone program is written in C and is integrated into the data acquisition program in CNS. This program now gets rid of network communication, and does not need to run code MAD. In this report, a test program written in Mathematic is described, and several matching conditions for the Twiss parameters are compared. Test results for the setting and measured tune values using running program on console are presented.
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| MPPE052 | Study on Coupling Issues in the Recycler at Fermilab | coupling, injection, lattice, multipole | 3209 | ||
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We have been working and trying to answer the following questions: where are the coupling sources in the Recycler and is the existing correcting system working fine? In this paper, we report the analysis on the sources from both modeling by code MAD based on nonlinear lattice and real machine. From the first turn flesh orbit, we fit the off-plane orbits by third order polynomial, then separate 1st, 2nd and 3rd order coefficients to see different effects. On the other hand, we present the analysis from turn by turn data, which is to verify the phase of two skew quads families are more or less orthogonal, and to make sure the minimum tune split is small enough, and is consistent with the measurement.
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| MPPE055 | Fitting the Fully Coupled ORM for the Fermilab Booster | booster, lattice, focusing, quadrupole | 3322 | ||
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Funding: This work is supported in part by grants from DE-AC02-76CH03000, DOE DE-FG02-92ER40747 and NSF PHY-0244793. |
The orbit response matrix (ORM) method* is applied to model the Fermilab Booster with parameters such as the BPM gains and rolls, and parameters in the lattice model, including the gradient errors and magnets rolls. We found that the gradients and rolls of the adjacent combined-function magnets were deeply correlated, preventing full determination of the model parameters. Suitable constraints of the parameters were introduced to guarantee an unique, equivalent solution. Simulations show that such solution preserves proper combinations of the adjacent parameters. The result shows that the gradient errors of combined-function magnets are within design limits. *J. Safranek, Nucl. Instr and Meth. A, {\bf 388}, 27 (1997). |
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| MPPE056 | Studies to Increase the Anti-Proton Transmission from the Target to the Debuncher Ring | lattice, sextupole, antiproton, quadrupole | 3357 | ||
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Funding: This work was supported by the Director, Office of Science, High Energy Physics, U.S. Department of Energy under Contracts No. DE-AC03-76SF00098 and DE-AC02-76CH03000. |
The AP2 beamline at Fermilab transports anti-protons from the production target to the Debuncher ring. The measured admittance of the Debuncher ring and the theoretical aperture of the line are larger than the size of the transmitted beam. Extensive tracking studies were done using the Accelerator Toolbox (AT) to understand the sources of the difference. As simulations pointed to chromatic effects being a source of problems, measurements were done to study this. Several possible remedies were studied including adding sextupoles to the line to reduce the chromatic effects. |
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| MPPE063 | Optimization of Steering Elements in the RIA Driver Linac | linac, focusing, lattice, quadrupole | 3600 | ||
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Funding: Work supported by the U.S. Department of Energy under contract W-31-109-ENG-38. |
The driver linac of the projected RIA facility is a versatile accelerator, a 1.4-GV, CW superconducting linac designed to simultaneously accelerate several heavy-ion charge states, providing beams from protons at about 1 GeV to uranium at 400 MeV/u at power levels at a minimum of 100 kW and up to 400 kW for most beams. Acceleration of multiple-charge-state uranium beams places stringent requirements on the linac design. A steering algorithm was derived that fulfilled the driver’s real estate requirements, such as placement of steering dipole coils on SC solenoids and of beam position monitors outside cryostats, and beam-dynamics requirements, such as coupling effects induced by the focusing solenoids.* The algorithm has been fully integrated in the tracking code TRACK** and is used to study and optimize the number and position of steering elements that minimize the multiple-beam centroid oscillations and preserve the beam emittance under misalignments of accelerating and transverse focusing elements in the driver linac. *E.S. Lessner and P.N. Ostroumov, Proceedings of the 9-th European Particle Accelerator Conference, July 2005, pp.1476-1478. **V.N. Aseev, P.N. Ostroumov, E.S. Lessner, and B. Mustapha, these proceedings. |
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| MPPE067 | Refined Calculation of Beam Dynamics During UMER Injection | dipole, injection, quadrupole, electron | 3733 | ||
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Funding: This work is funded by U.S. Dept. of Energy under grants DE-FG02-94ER40855 and DE-FG02-92ER54178. |
The University of Maryland Electron Ring (UMER) is built as a low-cost testbed for intense beam physics for benefit of larger ion accelerators. The beam intensity is designed to be variable, spanning the entire range from low current operation to highly space-charge-dominated transport. The ring has recently been closed and multi-turn commissioning has begun. Although we have conducted many experiments at high space charge during UMER construction, lower-current beams have become quite useful in this commissioning stage for assisting us with beam steering, measurement of phase advance, etc. One of the biggest challenges of multi-turn operation of UMER is correctly operating the Y-shaped injection section, hence called the Y-section, which is specially designed for UMER multi-turn operation. It is a challenge because the system requires several quadrupoles and dipoles in a very stringent space, resulting in mechanical, electrical, and beam control complexities. This paper presents a simulation study of the beam centroid motion in the injection region. |
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| MPPE075 | Simulation of the Effect of an In-Vacuum Undulator on the Beam Dynamics of the ALS | undulator, dynamic-aperture, injection, lattice | 3949 | ||
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Funding: Work supported by the Director, Office of Energy Research, Office of Basic Energy Science, Material Sciences Division, U.S. Department of Energy, under Contract No. DE-AC03-76SF00098. |
The femtosecond slicing project at the Advanced Light Source (ALS) requires that a short period (3 cm) and narrow gap (5.5 mm) in vacuum undulator to be installed. The combination of the short period and the narrow gap raised concern of the impact on the beam dynamics. A 3D field model was established based on numerical data using 8 longitudinal and 4 transverse harmonics. At first fourth-order symplectic integrator was used. It was to our surprise that the dynamic aperture decreased by a fact of 3. To understand the cause of the drastic change in the dynamic aperture, the field model was implemented in a differential algebraic code and the Taylor map of the undulator was obtained. Tracking result using the Taylor map showed little change in the dynamic aperture, which was latter corroborated by that using the symplectic integrator with 150 slices per period (as opposed to 10 before). Yet it is simply too time consuming to use the symplectic integrator with such thin slices. For this case, Taylor proves to be a much faster alternative. |
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| MPPE081 | The Comparison of a New Beam-Tracking Code to the Acceleration Test | linac, acceleration, dipole, injection | 4072 | ||
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A new beam-tracking code using a 3D electro-magnetic field map of a linac is being developed. In this code, beam dynamics including non-linear and dipole effects can be easily estimated based on simulated field maps provided by commercial 3D analysis software. To verify the code, we manufactured an IH-linac and acceleration test of the linac was carried out with proton beam. The simulated results were compared with the tested acceleration performances.
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| MPPE082 | Non-Linear Beam Dynamics in High Resolution Multi-Pass Time of Flight Mass Separator | ion, extraction, resonance, ion-source | 4105 | ||
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Funding: This work was supported by the UNIRIB collaboration and Oak Ridge Associated Universities. |
A multi-pass time-of-flight (MTOF) mass separator is under development by the UNIRIB collaboration. The MTOF consists of two coaxial electrostatic mirrors, focusing lenses and auxiliary injection, extraction and separation elements. The injected ions having almost the same energy but different masses undergo hundreds or thousands of reflections between the mirrors. In the course of this periodic motion, the ions of different masses and hence velocities are spatially separated in longitudinal direction. The periodic motion in the MTOF has been investigated with a recently developed ray tracing program utilizing the canonical integration technique. Results of the performed numerical simulations are discussed. The simulations displayed nonlinear character of the ion’s behavior both in transverse and longitudinal phase spaces. The ion’s transverse stability and longitudinal isochronicity were the matters of primary attention. It is shown in particular that at transverse tunes of around q=0.75 the system can be adjusted to be isochronous up to at least the 3rd order of the ToF optical aberrations. |
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| MPPP009 | Linac Coherent Light Source Longitudinal Feedback Model | feedback, linac, gun, electron | 1156 | ||
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Funding: Work is supported by the US Department of Energy under contract DE-AC02-76SF00515. |
The Linac Coherent Light Source (LCLS) will be the world's first x-ray free-electron laser (FEL). To ensure the vitality of FEL lasing, it is critical to preserve the high quality of the electron beam during acceleration and compression. The peak current and final energy are very sensitive to system jitter. To minimize this sensitivity, a longitudinal feedback system on the bunch length and energy is required, together with other diagnostics and feedback systems (e.g., on transverse phase space). In this paper, we describe a simulation framework, which includes a realistic jitter model for the LCLS accelerator system, the RF acceleration, structure wakefield, and second order optics. Simulation results show that to meet the tight requirements set by the FEL, such a longitudinal feedback system is mandatory. |
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| MPPP010 | Feedback to Suppress Phase Noise at Aladdin | feedback, dipole, damping, synchrotron | 1180 | ||
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The performance of the Aladdin infrared beamline is adversely affected by a Robinson mode in which all bunches move in unison with a frequency of 3 kHz. To decrease these oscillations, feedback has been installed in the radiofrequency system to damp longitudinal motion of the bunch centroids. Simulations indicate that at frequencies around 3 kHz, the phase noise generated by Robinson modes may be reduced 20 dB by feedback with a damping time of 0.3 ms. This agrees with the measured performance of feedback circuitry. Since the feedback greatly improves operation of the infrared beamline, it is now incorporated into the standard operation of Aladdin.
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| MPPP012 | First-Principles Simulation and Comparison with Beam Tests for Transverse Instabilities and Damper Performance in the Fermilab Main Injector | damping, dipole, injection, betatron | 1300 | ||
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An end-to-end performance calculation and comparison with beam tests was performed for the bunch-by-bunch digital transverse damper in the Fermilab Main Injector. Time dependent magnetic wakefields responsible for "Resistive Wall" transverse instabilities in the Main Injector were calculated with OPERA-2D using the actual beam pipe and dipole magnet lamination geometry. The leading order dipole component was parameterized and used as input to a bunch-by-bunch simulation which included the filling pattern and injection errors experienced in high-intensity operation of the Main Injector. The instability growth times, and the spreading of the disturbance due to newly mis-injected batches was compared between simulations and beam data collected by the damper system. Further simulation models the effects of the damper system on the beam.
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| MPPP020 | RF Phase Modulation at the LNLS Electron Storage Ring | synchrotron, single-bunch, resonance, beam-loading | 1686 | ||
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Funding: FAPESP |
In the Brazilian Electron Storage Ring, we observed that modulating the phase of accelerating fields at twice the synchrotron frequency suppressed remarkably well a longitudinal coupled-bunch mode of the beam driven by one of the RF cavities. We present results of a set of systematic measurements, in single and multi-bunch mode, aimed at characterizing the effects of the modulation on the beam. We also compare those experiments with the results of tracking simulations. |
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| MPPP021 | Evolution of the Machine Impedance following the ESRF Upgrade to Low-Gap NEG Coated Aluminium Chambers | impedance, single-bunch, vacuum, insertion | 1712 | ||
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The installation of 5 meter-long, 8 mm vertical aperture insertion device (ID) aluminum chambers coated in house with non evaporable getter material is progressing at a rate of one chamber per shutdown. The evolution of the impedance with associated consequences on instability thresholds, following the installation of a number of low aperture insertion device chambers will be reported. In particular the impedance measurement using the local bump method allowed the identification and the replacement of the chambers of highest impedance. Correlation with the evolution of the single bunch instability thresholds and the theoretical prediction will be discussed. It could be observed that change in vertical aperture has a sensible effect on the single bunch horizontal threshold.
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| MPPP023 | Numerical Calculation of Coupling Impedances for Kicker Modules | impedance, coupling, kicker, extraction | 1820 | ||
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Funding: Work supported in part by DFG under contract GraKo 410 and GSI, Darmstadt. |
Maintaining the impedance budget is an important task in the planning of any new accelerator facility. While estimates from analytical computations and measurements play a central role in doing so, numerical calculations have become an important alternative today. On the basis of Finite Integration Theory, we have developed a simulation tool for the direct computation of coupling impedances in the frequency domain. After discussing the special features of our code as compared to commercial programs, we present our results for cases where coupling impedances have been obtained from another source, e.g. experiment. In particular, we consider the longitudinal and transverse impedances of the SNS extraction kicker and present investigations related to the injection/extraction system of the future heavy-ion synchrotron at GSI. |
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| MPPP027 | Suppression of the Longitudinal Coupled-Bunch Instabilities by the RF Phase Modulation in the Pohang Light Source | synchrotron, higher-order-mode, storage-ring, damping | 1970 | ||
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In the 2.5 GeV Pohang Light Source, we have investigated the suppression of the longitudinal coupled instabilities (CBI) caused by higher order modes (HOMs) of RF cavities. At higher beam current than 170 mA the 758 MHz or 1300 MHz HOMs occurred and the beam could be unstable. The longitudinal CBI could be suppressed by modulating the phase of an RF accelerating voltage at a frequency of 2 times the synchrotron oscillation frequency and by adjusting the water temperatures of the RF cavities. The longitudinal beam oscillations measured by streak camera in synchro-scan mode were shown. The experiment results were compared with the macro particle tracking simulation.
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| MPPT014 | Design Concept for AGS Injection Kicker Upgrade to 2 GeV | kicker, proton, injection, impedance | 1380 | ||
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Funding: Canada Foundation for Innovation, U.S. Dept of Energy. |
The present AGS injection kickers at A5 location were designed for 1.5 GeV proton injection. Recent high intensity runs have pushed the transfer kinetic energy to 1.94 GeV, but with an imperfect matching in transverse phase space. Space charge forces result in both fast and slow beam size growth and beam loss as the size exceeds the AGS aperture. A proposed increase in the AGS injection energy to 2 GeV with adequate kick strength would greatly reduce the beam losses making it possible to increase the intensity from 70 TP (70 * 1012 protons/s) to 100 TP. R&D studies are being undertaken by TRIUMF, in collaboration with BNL, to design two new kicker magnets for the AGS A10 location to provide an additional kick of 1.5 mrad to 2 GeV protons. TRIUMF has proposed a design for a 12.5 W transmission line kicker magnet with rise and fall times of 100 ns, 3% to 97% and field uniformity of ±3% over 90% of the aperture, powered by matched 12.5 W pulse-forming lines. This paper describes the present status of a prototype design including the results of detailed 2D and 3D electromagnetic modeling of a transmission line kicker magnet and PSpice time domain analysis of the magnetic kick strength. |
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| MPPT017 | Design of Switching Magnet for 20-MeV Beamlines at PEFP | vacuum, proton, extraction, multipole | 1575 | ||
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Funding: Ministry of Science and Technology. |
The PEFP(Proton Engineering Frontier Project) proton linac is designed to have two proton beam extraction lines at the 20-MeV and 100-MeV end. The 20-MeV extraction line is branched out into 5 beamlines by using the switching magnet. The magnet bends the proton beam by +20, +10, 0, -10, -20 degrees, respectively, and has an AC frequency of 5 Hz with a programmable ac power supply. It employs an H-shape, 0.45 T magnetic field, 0.5 m effective magnet length, 30x5 cm bore aperture. The pole shape is optimized for the field levels. Laminated steel of 0.5 mm is enough to suppress the eddy current effect in the yoke. This paper presents the magnet specification and primary design. |
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| MPPT027 | Three-Dimensional Design of a Non-Axisymmetric Periodic Permanent Magnet Focusing System | focusing, beam-transport, permanent-magnet, electron | 1964 | ||
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Funding: Work supported by the MIT Deshpande Center for Technological Innovation, the U.S. Department of Energy, High-Energy Physics Division, Grant No. DE-FG02-95ER40919, and the Air Force Office of Scientific Research, Grant No. F49620-03-1-0230. |
A three-dimensional (3D) design is presented of a non-axisymmetric periodic permanent magnet focusing system which will be used to focus a large-aspect-ratio, ellipse-shaped, space-charge-dominated electron beam. In this design, an analytic theory is used to specify the magnetic profile for beam transport. The OPERA3D code is used to compute and optimize a realizable magnet system. Results of the magnetic design are verified by two-dimensional particle-in-cell and three-dimensional trajectory simulations of beam propagation using PFB2D and OMNITRAK, respectively. Results of fabrication tolerance studies are discussed. |
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| MPPT057 | Design of a Magnet System for a Muon Cooling Ring | closed-orbit, lattice, dynamic-aperture, dipole | 3366 | ||
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Funding: This work was performed with the support of the U.S. DOE under Contract No. DE-AC02-98CH10886. |
A hydrogen gas filled muon cooling ring appears to be a promising approach to reducing the emittance of a muon beam for use in a neutrino factory or a muon collider. A small muon cooling ring is being studied to test the feasibility of cooling by this method. This paper describes the magnet system to circulate the muons. The magnet design is optimized to produce a large dynamic aperture to contain the muon beam with minimum losses. Muons are tracked through the field to verify the design. |
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| MPPT072 | 3D Simulation Studies of SNS Ring Doublet Magnets | SNS, quadrupole, multipole, dipole | 3865 | ||
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge. |
The accumulator ring of the Spallation Neutron Source (SNS) at ORNL employs in its straight sections closely packed quadrupole doublet magnets with large aperture of R=15.1 cm and relatively short iron-to-iron distance of 51.4 cm.* The magnetic interference among the magnets in the doublet assemblies is not avoidable due to the fringe fields. Though each magnet in the assemblies has been individually mapped to high accuracy of delta(B)/B~1x10-4, the experimental data including the magnet interference effect in the assemblies will not be available. We have performed 3D computer simulations on a quadrupole doublet model in order to assess the degree of the interference and to obtain relevant data which should be very useful for the SNS commissioning and operation. This paper reports our simulation results. *N. Tsoupas et al. "A Large-aperture Narrow Quadrupole for the SNS Accumulator Ring," Proc. EPAC 2002, p.1106, Paris, June 3-7, 2002. |
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| MPPT073 | Field Distribution of Injection Chicane Dipoles in SNS Ring | dipole, multipole, SNS, injection | 3907 | ||
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge. |
3D computing simulations have been performed to study the magnetic field distribution of the injection chicane dipoles in the SNS ring.* The simulation studies have yielded the performance characteristics of the magnets and generated the magnetic field data in three dimensional grids, which can be used for detailed investigation of beam dynamics. Based on the simulation data, a 3D multipole expansion of the chicane dipole field, consisting of generalized gradients and their derivatives, has been made. The harmonic and pseudo-harmonic components in the expansion give much insight into the magnet physics. The expansion is quasi-analytical by fitting numeric data into a few interpolation functions. A 5th-order representation of the field is generated, and the effects of even higher order terms on the field representation are discussed. *The injection chicane dipoles were designed at BNL by Y.Y. Lee, W. Meng, et al. See "Injection into the SNS Accumulator Ring: Minimizing Uncontrolled Losses and Dumping Stripped Electrons," D.T. Abell, Y.Y. Lee, W. Meng, EPAC 2000. |
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| MPPT084 | Dipole and Quadrupole Magnets for the Duke FEL Booster Injector | dipole, quadrupole, booster, lattice | 4147 | ||
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Funding: This work is supported by U.S. DOE grant # DE-FG02-01ER41175 and by AFOSR MFEL grant # F49620-001-0370. |
The full energy booster injector for the Duke FEL storage ring is presently under installation. The booster is designed to provide continuous injection into the Duke FEL storage ring in the top-off mode at the energy variable from 270 MeV to 1.2 GeV. The magnetic elements for the booster have been fabricated and magnetically measured in the Budker Institute of Nuclear Physics, Russia. The paper presents magnetic and mechanical design of the booster dipole and quadrupole magnets and results of their magnetic measurements. Results of simulation of the booster lattice taking into account residual field and non-linearity of the magnets are also presented. |
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| MPPT086 | Conventional Magnets Design for the Candle Storage Ring | quadrupole, sextupole, storage-ring, dipole | 4182 | ||
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The lattice of 216m long CANDLE storage ring (16 Double Bend Achromat cells) will contain 32 gradient dipole magnets, 80 quadrupole magnets of three types and two types of 64 sextupole magnets. Magnetic as well as mechanical design of those magnets has been performed relying on extensive world experience. Computer simulations and large volume of computations have been carried out to design magnets that conform to strict requirements.
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| MOPB003 | Progress with the 2Q-LEBT Facility for the RIA Project | ion, emittance, ion-source, rfq | 253 | ||
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Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. W-31-109-ENG-38. |
The Rare Isotope Accelerator (RIA) facility utilizes the concept of simultaneous acceleration of two charge states from the ion source. We are building a prototype two charge-state (2Q) injector of the RIA Driver Linac, which includes an ECR ion source originally built by Berkeley Ion Equipment Corporation, a LEBT and one-segment of the prototype RFQ. The reassembly and commissioning of the ECR source has been completed. During the commissioning process we modified and replaced several major components of the BIE-100 to increase the source performance. A new diagnostic station has been designed and built for accurate measurements of the output beam emittance. The paper will discuss detailed beam dynamics studies together with extensive emittance measurements of various ion beams. The status of the design and fabrication of 100 kV high voltage platform, achromatic bending system, multi-harmonic buncher, and a full power 57.5 MHz RFQ segment will be presented. |
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| MOPB010 | Simulations and Experiments of Electron Beams Pre-Modulated at the Photocathode | electron, laser, radiation, space-charge | 704 | ||
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Funding: Work is supported by the Office of Naval Research, the Joint Technology Office, and the Department of Energy. |
The University of Maryland and the Source Development Laboratory at Brookhaven National Laboratory have been collaborating on a project that explores the use of electron beam pre-modulation at the cathode to control the longitudinal structure of the electron beam. This technique could be applied to creating deliberate modulations which can lead to the generation of terahertz radiation, or creating a smooth profile in order to supress radiation. This paper focuses on simulations that explore some of the pre-modulated cases achieved experimentally. |
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| TOAC004 | Experimental Investigation of Beam Breakup in the Jefferson Laboratory 10 kW FEL Upgrade Driver | damping, optics, recirculation, quadrupole | 369 | ||
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Funding: This work supported by the Office of Naval Research, the Joint Technology Office, the Commonwealth of Virginia, the Air Force Research Laboratory, Cornell University and by DOE Contract DE-AC05-84ER40150. |
In recirculating accelerators, and in particular energy recovery linacs (ERLs), the maximum current has been limited by multipass, multibunch beam breakup (BBU), which occurs when the electron beam interacts with the higher-order modes (HOMs) of an accelerating cavity on the accelerating pass and again on the energy recovered pass. This effect is of particular concern in the design of modern high average current energy recovery accelerators utilizing superconducting technology. Experimental observations of the instability at the Jefferson Laboratory 10 kW Free-Electron Laser (FEL) are presented. Measurements of the threshold current for the instability are presented and compared to the predictions of several BBU simulation codes. To further characterize the instability, beam based measurements were made to determine the orientation of the dangerous HOMs. With BBU posing a threat to high current beam operation in the FEL, several suppression schemes were developed. These include direct damping of the dangerous HOMs and appropriately modifying the electron beam optics. Preliminary results of their effectiveness in raising the threshold current for stability are presented. |
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| TPAE002 | The Project PLASMONX for Plasma Acceleration Experiments and a Thomson X-Ray Source at SPARC | laser, plasma, electron, acceleration | 820 | ||
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We present the status of the activity on the project PLASMONX, which foresees the installation of a multi-TW Ti:Sa laser system at the CNR-ILIL laboratory to conduct plasma acceleration experiments and the construction of an additional beam line at SPARC to develop a Thomson X-ray source at INFN-LNF. After pursuing self-injection experiments at ILIL, when the electron beam at SPARC will be available the SPARC laser system will be upgraded to TW power level in order to conduct either external injection plasma acceleration experiments and ultra-bright X-ray pulse generation with the Thomson source. Results of numerical simulations modeling the interaction of the SPARC electron beam and the counter-propagating laser beam are presented with detailed discussion of the monochromatic X-ray beam spectra generated by Compton backscattering: X-ray energies are tunable in the range 20 to 1000 keV, with pulse duration from 30 fs to 20 ps. Preliminary simulations of plasma acceleration with self-injection are illustrated, as well as external injection of the SPARC electron beam. The proposed time schedule for this initiative is finally shown, which is tightly correlated with the progress of the SPARC project.
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| TPAE010 | Resonant Excitation of Selected Modes by a Train of Electron Bunches in a Rectangular Dielectric Wakefield Accelerator | electron, single-bunch, radiation, resonance | 1174 | ||
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Funding: This work was partly supported by CRDF award #UP2-2569-KH-04 |
The dielectric wake field accelerator is based on particle acceleration by wake fields excited in a dielectric waveguide by a regular sequence of electron bunches. Enhancement of the accelerating field can be achieved using two phenomena: coherent excitation by many bunches (multibunch effect) and constructive interference of many excited eigenmodes (multimode effect). It was believed that the latter is possible only for planar slab geometry in which the excited modes are equally spaced in frequency. By analysis and simulation, in this presentation the effect of wake field superposition to high amplitude is demonstrated for arbitrary rectangular geometry that is more realizable in experiment. We find this result using simultaneous multibunch and multimode operation providing the repetition frequency of the bunch sequence is equal to the frequency difference between selected modes, whereupon resonant oscillation takes place. Moreover, it is shown that for an appropriate choice of selected modes and bunch repetition frequency a "quasimonopolar” peaked wake field can be excited. |
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| TPAE017 | Progress on High Power Tests of Dielectric-Loaded Accelerating Structures | vacuum, impedance, acceleration, plasma | 1566 | ||
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Funding: This work was supported by the U.S. Dept of Energy, High Energy Physics Division and Office of Naval Research. |
This paper presents a progress report on a series of high-power rf experiments that were carried out to evaluate the potential of the Dielectric-Loaded Accelerating (DLA) structure for high-gradient accelerator operation. Since the last PAC meeting in 2003, we have tested DLA structures loaded with two different ceramic materials: Alumina (Al2O3) and MCT (MgxCa1-xTiO3). The alumina-based DLA experiments have concentrated on the effects of multipactor in the structures under high-power operation, and its suppression using TiN coatings, while the MCT experiments have investigated the dielectric joint breakdown observed in the structures due to local field enhancement. In both cases, physical models have been set up, and the potential engineering solutions are being investigated. |
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| TPAE022 | Analytical and Numerical Calculations of Two-Dimensional Dielectric Photonic Band Gap Structures and Cavities for Laser Acceleration | lattice, laser, acceleration, plasma | 1793 | ||
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Funding: Research supported in part by Department of Energy, Office of High Energy Physics, Grant No. DE-FG02-95ER40919 and in part by Department of Defense, Joint Technology Office, under a subcontract with University of Arizona. |
Dielectric photonic band gap (PBG) structures have many promising applications in laser acceleration. For these applications, accurate determination of fundamental and high order band gaps is critical. We present the results of our recent work on analytical calculations of two-dimensional (2D) PBG structures in rectangular geometry. We compare the analytical results with computer simulation results from the MIT Photonic Band Gap Structure Simulator (PBGSS) code, and discuss the convergence of the computer simulation results to the analytical results. Using the accurate analytical results, we design a mode-selective 2D dielectric cylindrical PBG cavity with the first global band gap in the frequency range of 8.8812 THz to 9.2654 THz. In this frequency range, the TM01-like mode is shown to be well confined. |
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| TPAE023 | 3D Metallic Lattices for Accelerator Applications | lattice, plasma, photon, vacuum | 1838 | ||
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Funding: DOE-HEP |
We present the results of research on 3D metallic lattices operating at microwave frequencies for application in (1) accelerator structures with higher order mode suppression, (2) Smith-Purcell radiation beam diagnostics, and (3) polaritonic materials for laser acceleration. Electromagnetic waves in a 3D simple cubic lattice formed by metal wires are calculated using HFSS. The bulk modes in the lattice are determined using single cell calculations with different phase advances in all three directions. The Brillouin diagram for the bulk modes is presented and indicates the absence of band gaps in simple lattices except the band below the cutoff. Lattices with thin wires as well as with thick wires have been analyzed. The Brillouin diagram also indicates the presence of low frequency 3D plasmon mode as well as the two degenerate photon modes analogous to those in a 2D lattice. Surface modes for a semi-infinite cubic lattice are modeled as a stack of cells with different phase advances in the two directions along the surface. The surface modes are found for both the thin and thick wire lattices in the band below the cutoff. They demonstrate that the lattice acts as a negative dielectric constant material. |
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| TPAE024 | Determination of Longitudinal Phase Space in SLAC Main Accelerator Beams | plasma, electron, acceleration, radiation | 1856 | ||
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In the E164 Experiment at that Stanford Linear Accelerator Center (SLAC), we seek to drive plasma wakes for electron acceleration using 28.5 GeV bunches from the main accelerator. These bunches can now be made with an RMS length of less than 20 microns, and direct measurement is not feasible. Instead, we use an indirect technique, measuring the energy spectrum at the end of the linac and comparing with detailed simulations of the entire machine. We simulate with LiTrack, a 2D code developed at SLAC which includes wakefields, synchrotron radiation and all second order optical aberrations. Understanding the longitudinal profile allows a better understanding of acceleration in the plasma wake, as well as investigation of possible destructive transverse effects. We present results from the July 2004 experimental run and show how this technique aids in data analysis. We also discuss accuracy and validation of phase space determinations.
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| TPAE027 | Calculations for Tera-Hertz (THz) Radiation Sources | radiation, electron, scattering, laser | 1994 | ||
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Funding: This work was supported by the U.S. Department of Energy under contract DE-2-76SF00515. |
We explore possibilities for THz sources from 0.3 - 30 THz. While still inaccessible, this broad gap is even wider for advanced acceleration schemes extending from X or, at most, W band RF at the low end up to CO2 lasers. While the physical implementations of these two approaches are quite different, both are proving difficult to develop so that even lower frequency, superconducting RF seems to be the currently preferred means. Similarly, the validity of modelling techniques varies greatly over this range of frequencies but generally mandates coupling Maxwell’s equations to the appropriate device transport physics for which there are many options. Here we calculate radiation from shaped transmission lines using finite-difference, time-domain (FDTD) simulations of Maxwell’s equations coupled to Monte-Carlo techniques for both the production and transport physics of short electron pulses. Examples of THz sources that demonstrate coherent interference effects will be discussed with the goal of optimizing on-chip THz radiators for different applications - ultimately including improved electron sources and accelerators. |
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| TPAE029 | High-Harmonic Inverse Free-Electron-Laser Interaction at 800 nm | electron, laser, undulator, resonance | 2113 | ||
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Funding: This work supported by Department of Energy contracts DE-AC03-76SF00515 (SLAC) and DE-FG03-97ER41043-II (Stanford). |
The inverse Free Electron Laser (IFEL) interaction has recently been proposed and used as a short wavelength modulator forμbunching of beams for laser acceleration experiments*,**. These experiments utilized the fundamental of the interaction between the laser field and electron bunch. In the current experiment, we explore the higher order resonances of the IFEL interaction from a 3 period, 1.8 centimeter wavelength undulator with a picosecond, 0.25 mJ/pulse laser at 800 nm. The resonances are observed by adjusting the gap of the undulator while keeping the beam energy constant. We will also discuss diagnostics for obtaining beam overlap and statistical techniques used to account for machine drifts and analyze the data. *W. D. Kimura, et. al., Phys. Rev. S.T. Acc. & Beams 4 101301 (2001). ** P. Musumeci, et. al., AAC 2004 Proceedings. Pg 170. |
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| TPAE031 | Simulations of Laser Pulse Coupling and Transmission Efficiency in Plasma Channels | laser, plasma, diagnostics, coupling | 2179 | ||
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Funding: Work supported by U.S. DOE under contracts DE-FG03-02ER83557, DE-FC02-01ER41178, DE-AC03-76SF00098, DE-FG03-95ER40926 and use of NERC supercomputer facilities. |
Optical guiding of the laser pulse in a laser wakefield accelerator (LWFA) via plasma channels can greatly increase the interaction length and, hence, the maximun energy of trapped electrons.* Energy efficient coupling of laser pulses from vacuum into plasma channels is very important for optimal LWFA performance. We present 2D particle-in-cell simulations of this problem using the VORPAL code.** Some of the mechanisms considered are enhanced leakage of laser energy transversely through the channel walls, enhanced refraction due to tunneling ionization of neutral gas on the periphery of the gas jet, ionization of neutral gas by transverse wings of the laser pulse and effect of the pulse being off axis of the channel. Using power spectral diagnostics,*** we are able to differentiate between pump depletion and leakage from the channel. The results from our simulations show that for short (≈λp) plasma ramp, very little leakage and pump depletion is seen. For narrow channel walls and long ramps, leakage increases significantly. *C. G. R. Gedes et al., Nature 431 (2004), p. 538. **C. Nieter and J. R. Cary, J. Comp. Phys. 196 (2004), p. 448.***D. A. Dimitrov et al., Proc. Advanced Accel. Concepts Workshop (2004). |
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| TPAE032 | Particle-in-Cell Simulations of Lower-Density CM-Scale Capillary Channels | laser, plasma, electron, vacuum | 2248 | ||
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Funding: This work is funded by DOE under contracts DE-FC02-01ER41178, DE-FG02-04ER84097, DE-AC03-76SF00098 and DE-FG03-95ER40926, including the SciDAC Accelerator Project and use of NERSC. |
Capillary channels of cm-length and at plasma density low compared to gas jets are promising setups for low noise laser wakefield acceleration. Computationally, however, the large discrepancy of the length scales of the plasma and the laser are a big challenge. Methods are therefore sought that relax the need to concurrently resolve both length scales. Moving windows allow to reduce the size of the computational box to a few plasma wave-lengths, which can already be a big gain compared to the full length of the capillary. On the other hand, average methods allow to relax the constraint to resolve the laser wavelength. These methods split the laser induced current into a fast varying part and a slowly varying envelope. The average over the fast timescales is performed in a semi analytic way, leaving the evolution of the envelope to be modeled. Such an envelope model is currently being incorporated into the VORPAL code.* Preliminary results show considerable time savings compared to fully resolved simulations. The status of this ongoing work will be presented. *C. Nieter and J. R. Cary, J. Comp. Phys. 196 (2004), p. 448. |
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| TPAE033 | Experimental and Numerical Studies of Particle Acceleration by an Active Microwave Medium | laser, acceleration, resonance, radiation | 2275 | ||
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There has been considerable theoretical work on the so-called PASER concept, in which a particle beam is accelerated directly by absorbing energy from an active medium, analogous to the amplification of an optical signal in a laser. Use of an active microwave (maser) medium would have the advantage of requiring relaxed beam quality (mm vs. nm characteristic beam dimensions). Recent work using electron paramagnetic resonance (EPR) techniques has demonstrated activity in the microwave regime (i.e. negative imaginary part of the magnetic susceptibility) for a class of organic compounds. A solution of fullerene (C60) in a liquid crystal solvent has been reported in the literature to possess a maser transition in the X-band region. An external DC magnetic field is required to obtain the effect; the frequency of the maser transition is adjustable by varying the magnetic field strength. We will report on the development of numerical and laboratory tools to evaluate the use of this material for accelerator applications, and evaluate the feasibility of an accelerating structure based on an active microwave medium.
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| TPAE034 | Developing a Multi-Timescale PIC Code for Plasma Accelerators | plasma, betatron, laser | 2324 | ||
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Funding: DOE: DE-FG02-92ER40745, DOE-SCIDAC: DE-FC02-01ER41192. |
An idea for advancing beam and plasma particles with different time scales in a full PIC model of plasma accelerators is proposed. Because beam particles usually respond much slower than plasma particles, large time steps can be used to update beam particles to save computation time. In this paper, we will describe how to apply this multi-timescale method in a particle-in-cell (PIC) [1] code OSIRIS [2]. Simulation results for SLAC E164 [3] experimental parameters are given and show a high degree of accuracy while gaining a factor of 4-6 in computing time. The limitations of this method are also studied. The maximum time saving is determined by driver beam energy and size of simulation box. |
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| TPAE041 | Modeling TeV Class Plasma Afterburners | plasma, acceleration, collider, emittance | 2666 | ||
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Funding: Work supported by DOE and NSF. |
Plasma wakefield acceleration can sustain acceleration gradients three orders of magnitude larger than conventional RF accelerator. In the recent E164X experiment, substantial energy gain of about 3Gev has been observed. Thus, a plasma afterburner, which has been proposed to double the incoming beam energy for a future linear collider, is now of great interest. In an afterburner, a particle beam drives a plasma wave and generates a strong wakefield which has a phase velocity equal to the velocity of the beam. This wakefield can then be used to accelerate part of the drive beam or a trailing beam. Several issues such as the efficient transfer of energy and the stable propagation of both the drive and trailing beams in the plasma are critical to the afterburner concept. We investigate the nonlinear beam-plasma interaction in such scenario using the 3D computer modeling code QuickPIC. We will report the latest simulation results of both 50 GeV and 1 TeV plasma afterburner stages for electrons including the beam-loading of a trailing beam. Analytic analysis of hosing instability in this regime will be presented. |
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| TPAE046 | Modeling Self-Ionized Plasma Wakefield Acceleration for Afterburner Parameters Using QuickPIC | plasma, electron, betatron, acceleration | 2905 | ||
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Funding: DOE |
A plasma wakefield accelerator (PWFA) has been proposed as a way to double the energy of a future linear collider. This afterburner concept will require meter long uniform plasmas. For the parameters envisaged in possible afterburner stages, the self-fields of the particle beam are intense enough to tunnel ionize some neutral gases such as lithium. Tunnel ionization has been investigated as a way for the beam itself to create the plasma.* Furthermore, tunnel ionization in a neutral or partially pre-ionized gas may create new plasma electrons and alter the plasma wake.*,** Unfortunately, it is not possible to model a PWFA with afterburner parameters using the models described in Bruhwiler et al. and Deng et al. Here we describe the addition of a tunnel ionization package using the ADK model into QuickPIC, a highly efficient quasi-static particle in cell (PIC) code which can model a PWFA with afterburner parameters. There is excellent agreement between QuickPIC and OSIRIS(a full PIC code) for pre-ionized plasmas. Effects of self-ionization on hosing instability –one of the most critical issues to overcome to make an afterburner a reality – for a bunch propagating in a plasma hundreds of betatron oscillations long will be discussed. *D. L. Bruhwiler et al., Phys. Plasmas 10 (2003), p. 2022. **S. Deng et al., Phys. Rev. E, 68, 047401 (2003). |
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| TPAE047 | Parameters Optimization for a Novel Vacuum Laser Acceleration Test at BNL-ATF | laser, electron, acceleration, vacuum | 2959 | ||
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Funding: U.S. DOE. |
This paper presents a new VLA theory model which has revealed that the injection electrons with low energy and small incident angle relative to the laser beam are captured and significantly accelerated in a strong laser field. For the further step for verifying the novel-VLA mechanics, we propose to use the BNL-ATF Terawatt CO2 laser and a high-brightness electron beam to carry out a proof-of-principle beam experiment. Experiment setup including the laser injection optics and electron extraction system and beam diagnostics is presented. Extensive optimized simulation results with ATF practical parameters are also presented, which shows that even when the laser intensity is not very high, the net energy gain still can be seen obviously. This could be prospect for a new revolution of vacuum laser acceleration. |
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| TPAE049 | The UCLA/SLAC Ultra-High Gradient Cerenkov Wakefield Accelerator Experiment | electron, radiation, laser, photon | 3067 | ||
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Funding: Work Supported by U.S. Dept. of Energy grant DE-FG03-92ER40693. |
An experiment is planned to study the performance of dielectric Cerenkov wakefield accelerating structures at extremely high gradients in the GV/m range. This new UCLA/SLAC collaboration will take advantage of the unique SLAC FFTB electron beam and its demonstrated ultra-short pulse lengths and high currents (e.g., sz = 20 μm at Q = 3 nC). The electron beam will be focused down and sent through varying lengths of fused silica capillary tubing with two different sizes: ID = 200 μm / OD = 325 μm and ID = 100 μm / OD = 325 μm. The pulse length of the electron beam will be varied in order to alter the accelerating gradient and probe the breakdown threshold of the dielectric structures. In addition to breakdown studies, we plan to collect and measure coherent Cerenkov radiation emitted from the capillary tube to gain information about the strength of the accelerating fields. Status and progress on the experiment are reported. |
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| TPAE051 | Designing Photonic Crystal Devices for Accelerators | lattice, coupling, electron, photon | 3164 | ||
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Funding: This work supported by U.S. Department of Energy grant DE-FG02-04ER41317. |
Photonic crystals (periodic dielectric structures with a lattice constant on the order of the wavelength of light) can have a wide range of properties. For instance, photonic crystals can be designed to be completely reflective within a certain bandwidth, thereby becoming a replacement for metal in accelerator structures such as waveguides and cavities. To see whether photonic crystals might find application in accelerators, and to design potential accelerator structures, we will need reliable computer simulations to predict fields and frequencies and other properties of photonic crystal structures. We propose to build photonic crystal structures in the microwave regime and test the validity of computer simulation against experiment. We can then explore more complex issues such as coupling to photonic crystal structures, higher-order mode rejection, and tunable photonic crystals. |
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| TPAE053 | Near-GeV Electron Beams from the Laser Wakefield Accelerator in the “Bubble” Regime | electron, laser, plasma, vacuum | |||
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Funding: This research was funded by the Korean Ministry Science and Technology through the Creative Research Initiative (CRI) Program. |
This Communication describes a 2D-PIC simulation of a laser wakefield accelerator in which an ultrashort, petawatt-class laser is focused and propagated through an underdense preformed plasma. We are looking at the phase-spaces of a large number of background plasma electrons that are accelerated to very high energies by the laser-induced plasma bubble. The result shows the possibility of generating a GeV-level electron beam in a few millimeters plasma size. As a future work, we will use a 500 TW laser system, that is under construction at APRI-GIST in Korea, for laser-plasma based accelerator researches to which the current simulation is relevant. |
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| TPAE054 | Ultraintense and Ultrashort Laser Pulses from Raman Amplification in Plasma for Laser-Plasma Accelerators | plasma, laser, electron, resonance | 3274 | ||
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Funding: Korea Electrotechnology Research Institute, Korea; Creative Research Initiatives, Korea. |
We present analysis and simulations of kinetic effects in the Raman pulse amplification in plasma. An ultraintense and ultrashort laser pulse is a very essential part in an advanced acceleration scheme using laser and plasma. To make strong pulses, a noble scheme of using Raman backscatter in plasma was proposed and has been studied intensively.* The Raman amplification in plasma does not have a restriction in material damage threshold. However, for the new amplifier to be a promising alternative of the CPA technique, more extensive studies on various issues are required. One of the fundamental issues is the electron kinetic effect such as particle trapping or wavebreaking. We present a theoretical analysis of the kinetic effect; a new kinetic term is derived to be added to the fluid model and the effect of the new term is verified by averaged-PIC (aPIC)** simulations. Various one dimensional and semi-two dimensional aPIC simulations of pulse amplification are presented. We discuss the future application of the Raman scheme to upgrading the laser pulse of the Center of Advanced Accelerator in KERI, which are currently 2 TW and 700 fs, into a few more TW and less than 100 fs. *V. M. Malkin, G. Shvets, and N. J. Fisch, Phys. Rev. Lett. vol. 82, 4448 (1999).**M. S. Hur, G. Penn, J. S. Wurtele, and R. Lindberg, Phys. Plasmas vol. 11, 5204 (2004). |
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| TPAE057 | A Multibunch Plasma Wakefield Accelerator | plasma, electron, laser, background | 3384 | ||
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We investigate a plasma wakefield acceleration scheme where a train of electron microbunches feeds into a high density plasma. When the microbunch train enters such a plasma that has a corresponding plasma wavelength equal to the microbunch separation distance, a strong wakefield is expected to be resonantly driven to an amplitude that is at least one order of magnitude higher than that using an unbunched beam. PIC simulations have been performed using the beamline parameters of the Brookhaven National Laboratory Accelerator Test Facility operating in the configuration of the STELLA inverse free electron laser (IFEL) experiment. A 65 MeV electron beam is modulated by a 10.6 um CO2 laser beam via an IFEL interaction. This produces a train of ~90 microbunches separated by the laser wavelength. In this paper, we present both a simple theoretical treatment and simulation results that demonstrate promising results for the multibunch technique as a plasma-based accelerator.
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| TPAE060 | Planned Enhanced Wakefield Transformer Ratio Experiment at Argonne Wakefield Accelerator | laser, electron, linac, pick-up | 3487 | ||
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Funding: U.S. Department of Energy. |
In this paper, we present a preliminary experimental study of a wakefield accelerating scheme that uses a carefully spaced and current ramped electron pulse train to produce wakefields that increases the transformer ratio much higher than 2. A dielectric structure was designed and fabricated to operate at 13.625 GHz with dielectric constant of 15.7. The structure will be initially excited by two beams with first and second beam charge ratio of 1:3. The expected transformer ratio is 3 and the setup can be easily extend to 4 pulses which leads to a transformer ratio of more than 6. The dielectric structure cold test results show the tube is within the specification. A set of laser splitters was also tested to produce ramped bunch train of 2 - 4 pulses. Overall design of the experiment and initial results will be presented. |
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| TPAP004 | Mechanical Design for Robustness of the LHC Collimators | injection, proton, collimation, beam-losses | 913 | ||
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The functional specification of the LHC Collimators requires, for the start-up of the machine and the initial luminosity runs (Phase 1), a collimation system with maximum robustness against abnormal beam operating conditions. The most severe cases to be considered in the mechanical design are the asynchronous beam dump at 7 TeV and the 450 GeV injection error. To ensure that the collimator jaws survive such accident scenarios, low-Z materials were chosen, driving the design towards Graphite or Carbon/Carbon composites. Furthermore, in-depth thermo-mechanical simulations, both static and dynamic, were necessary.This paper presents the results of the numerical analyses performed for the 450 GeV accident case, along with the experimental results of the tests conducted on a collimator prototype in Cern TT40 transfer line, impacted by a 450 GeV beam of 3.1·1013 protons, with impact parameters from 1 to 5 mm.
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| TPAP005 | Calculation of Residual Dose Rates and Intervention Scenarios for the LHC Beam Cleaning Insertions–Constraints and Optimization | insertion, radiation, radioactivity, quadrupole | 940 | ||
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Radiation protection of the personnel who will perform interventions in the LHC Beam Cleaning Insertions is mandatory and includes the design of equipment and the establishment of work procedures. Residual dose rates due to activated equipment are expected to reach significant values such that any maintenance has to be planned and optimized in advance. Three-dimensional maps of dose equivalent rates at different cooling times after operation of the LHC have been calculated with FLUKA. The simulations are based on an explicit calculation of induced radioactivity and of the transport of the radiation from the radioactive decay. The paper summarizes the results for the Beam Cleaning Insertions and discusses the estimation of individual and collective doses received by personnel during critical interventions, such as the exchange of a collimator or the installation of Phase 2. The given examples outline the potential and the need to optimize, in an iterative way, the design of components as well as the layout of the beam cleaning insertions. Furthermore, results of measurements and simulations of residual dose rates for a collimator test recently performed at the SPS are presented.
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| TPAP009 | Collimation in the Transfer Lines to the LHC | injection, septum, optics, collimation | 1135 | ||
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Injection intensities for the LHC are over an order of magnitude above damage level. The TI 2 and TI 8 transfer lines between the SPS and LHC are each about 2.5 km long and comprise many active elements running in pulsed mode. The collimation system in the transfer lines is designed to dilute the beam energy sufficiently in case of accidental beam loss or mis-steered beam. A system using three collimator families spaced by 60 degrees in phase advance, both in the horizontal and the vertical plane has been chosen. We discuss the reasons for this choice, the layout and, the expected performance of the system in terms of maximum amplitudes and energy deposition.
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| TPAP012 | Luminosity Limit from Bound-Free Pair Production in the LHC | ion, luminosity, dipole, proton | 1306 | ||
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The luminosity of the LHC as a lead-ion collider is known to be limited by the large cross-sections for electromagnetic processes in ultra-peripheral collisions. In particular, the process of bound-free e-e+ pair production creates secondary beams of Pb81+ ions emerging from the collision points and impinging on the vacuum envelope inside superconducting magnets. New Monte-Carlo simulations, exploiting recent implementations of the physics of ion interactions with matter, are helping us to quantify the relationships among luminosity, energy deposition in the magnet coils and signals on beam loss monitors with a view to predicting and alleviating the quench limit on luminosity.
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| TPAP013 | The Performance of the New TCDQ System in the LHC Beam Dumping Region | proton, secondary-beams, dumping, monitoring | 1324 | ||
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The superconducting quadrupole magnet Q4 in IR6 and other downstream LHC machine elements risk destruction in the event of a beam dump that is not synchronised with the abort gap. In order to protect these elements, a single sided mobile graphite diluter block TCDQ, in combination with a two-sided secondary collimator TCS and an iron shield TCDQM, will be installed in front of Q4. This protection system should also intercept spurious particles in the beam abort gap to prevent quenches from occurring during regular beam aborts, and must also intercept the particles from the secondary halo during low beam lifetime without provoking quenches. The conceptual design of the TCDQ system is briefly presented, with the load conditions and performance criteria. The FLUKA energy deposition simulations are described, and the results discussed in the context of the expected performance levels for LHC operation.
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| TPAP014 | Energy Deposition Studies for the Betatron Cleaning Insertion (IR7) of LHC | insertion, proton, collimation, quadrupole | 1386 | ||
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Two insertions (IR3, IR7) of the Large Hadron Collider (LHC) are dedicated to beam cleaning with the design goals of absorbing part of the primary beam halo and of the secondary radiation. The tertiary halo which escapes the collimation system in IR7 may heat the cold magnets at unacceptable levels, if no additional absorber is used. In order to assess the energy deposition in sensitive components, extensive simulations were run with the Monte Carlo cascade code FLUKA. The straight section and the dispersion suppressors of IR7 were fully implemented. A modular approach in the geometry definition and an extensive use of user-written programs allowed the implementation of all magnets and collimators with high precision, including flanges, steel supports and magnetic field. This paper provides the number and location of additional absorbers needed to keep the energy deposition in the coils of the magnets below the quenching limit.
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| TPAP019 | Aperture Studies of the SPS to LHC Transfer Lines | optics, dipole, injection, alignment | 1664 | ||
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The SPS to LHC transfer lines TI 2 and TI 8 are each several km in length and use magnets with small apertures. An aperture model for the lines has been developed in MAD-X format, with a full description of all installed vacuum elements and the possibility to interpolate at any length interval. This model has been used with tolerances and errors to simulate the expected line aperture available for the beam. The model features and simulation results are presented, with derived aperture limits. The results from aperture measurements made during the TI 8 line beam commissioning in 2004 are presented and compared to the expectations.
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| TPAP021 | A New Technique for Making Bright Proton Bunches using Barrier RF Systems | proton, emittance, collider, luminosity | 1745 | ||
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Funding: Work supported by the Universities Research Association, Inc., under contract DE-AC02-76CH03000 with the U.S. Department of Energy. |
I describe here very promising schemes for producing high intensity low longitudinal emittance proton bunches for pp and ppbar high energy colliders. These methods are based on the use of wide-band barrier rf systems in the up-stream circular accelerators. The beam dynamics simulations clearly suggest that these schemes allow a wide range of bunch intensities and longitudinal emittances. In this paper I present the principle of these methods and results of multi-particle beam dynamics simulations applied to the Fermilab Tevatron. The feasibility of these methods to LHC pp collider will also be discussed. I also review a few other schemes which have been adopted and investigated at collider facilities. |
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| TPAP022 | Mixed pbar Source Operation at the Fermilab Tevatron | injection, acceleration, collider, luminosity | 1763 | ||
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Funding: Work supported by the Universities Research Association, Inc., under contract DE-AC02-76CH03000 with the U.S. Department of Energy. |
Recently, we have adopted a scheme called "Mixed pbar Source Operation" to transfer 2.5 MHz pbar bunches from the Recycler and the Accumulator to the Fermilab Main Injector (MI). In this scheme, 2.5MHz pbar bunches are captured adiabatically in 53 MHz buckets at 8 GeV in the MI and accelerated to 150 GeV before bunch coalescing and transfer to the Tevatron collider stores. A special magnet ramp was needed in the MI to allow for pbar beam of slightly different 8 GeV energies from the Recycler and the Accumulator. Here we present the details of the scheme and its advantage over the method used for past several years. |
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| TPAP031 | Simulations of an Acceleration Scheme for Producing High Intensity and Low Emittance Antiproton Beam for Fermilab Collider Operation | emittance, beam-loading, acceleration, antiproton | 2164 | ||
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Funding: Operated by Universities Research Association, Inc. for the U.S. Department of Energy under contract DE-AC02-76CH03000. |
During Fermilab collider operation, the Main Injector (MI) provides high intensity and low emittance proton and antiproton beams for the Tevatron. The present coalescing scheme for antiprotons in the Main Injector yields about a factor of two increase in the longitudinal emittance and a factor of 5% to 20% decrease in intensity before injection to the Tevatron. In order to maximize the integrated luminosity delivered to the collider experiments, it is important to minimize the emittance growth and maximize the intensity of the MI beam. To this end, a new scheme* using a combination of 2.5 MHz and 53 MHz accelerations has been developed and tested. This paper describes the full simulation of the new acceleration scheme, taking account of space charge, 2.5 MHz and 53 MHz beam loading, and the effect of residual 53 MHz rf voltage during 2.5 MHz acceleration and rf manipulations. The simulations show the longitudinal emittance growth at the 10% level with no beam loss. The experimental test of the new scheme is reported in another PAC'05 paper. *G.P. Jackson, The Fermilab Recycler Ring Technical Design Report, FERMILAB-TM-1991, November 1996. |
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| TPAP040 | Feasibility Study of Beam-Beam Compensation in the Tevatron with Wires | antiproton, injection, beam-losses, lattice | 2645 | ||
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Funding: Dept. of Energy. |
At large distances the field profile of a current carrying wire matches the profile of the field of a round beam. We consider the practical applicability of this principle in compensating long-range beam-beam effects in the Tevatron. Changes in the helix and beam separation from injection energy to collision energy require that different wire configurations at these different energies. Due to the seventy or more long-range interactions, each set of wires must compensate several interactions. We first develop the principles of non-local compensation with a small set of wires. Next we use these principles in detailed simulation studies with beam-beam interactions and wire fields to determine the feasibility of the compensation in the Tevatron. |
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| TPAP043 | Electron Cooling of RHIC | electron, ion, emittance, linac | 2741 | ||
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We report progress on the R&D program for electron-cooling of the Relativistic Heavy Ion Collider (RHIC). This electron cooler is designed to cool 100 GeV/nucleon at storage energy using 54 MeV electrons. The electron source will be a superconducting RF photocathode gun. The accelerator will be a superconducting energy recovery linac. The frequency of the accelerator is set at 703.75 MHz. The maximum electron bunch frequency is 9.38 MHz, with bunch charge of 20 nC. The R&D program has the following components: The photoinjector and its photocathode, the superconducting linac cavity, start-to-end beam dynamics with magnetized electrons, electron cooling calculations including benchmarking experiments and development of a large superconducting solenoid. The photoinjector and linac cavity are being incorporated into an energy recovery linac aimed at demonstrating ampere class current at about 20 MeV. A Zeroth Order Design Report is in an advanced draft state, and can be found on the web at http://www.agsrhichome.bnl.gov/eCool/.
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Under contract with the U.S. Department of Energy, Contract Number DE-AC02-98CH10886. |
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| TPAP051 | Principle of Global Decoupling with Coupling Angle Modulation | coupling, quadrupole, injection, betatron | 3132 | ||
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Funding: Work supported by U.S. DOE under contract No. DE-AC02-98CH10886. |
The global betatron decoupling on the ramp is an important issue for the operation of the Relativistic Heavy Ion Collider (RHIC). A new scheme coupling phase modulation is found. It introduces a rotating extra coupling into the coupled machine to detect the residual coupling. The eigentune responses are measured with a high resolution phase lock loop (PLL) system. From the minimum and maximum tune splits, the correction strengths are given. The time period occupied by one coupling phase modulation is less than 10 seconds. So it is a very promising solution for the global decoupling on the ramp. In this article the principle of the coupling phase modulation is given. The simulation with the smooth accelerator model is also done. The practical issues concerning its applications are discussed. |
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| TPAP052 | Possible Phase Loop for the Global Decoupling | coupling, quadrupole, feedback, collider | 3182 | ||
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Funding: Work supported by U.S. DOE under contract No. DE-AC02-98CH10886. |
Besides two eigentunes Q1 and Q2 , two amplitude ratios r1 and r2 and two phase differences ∆ φ1 and ∆ φ2 are introduced for the global coupling observation. Simulations are carried out to check their behaviors in the process of the skew quadrupole strength scans. Some attractive features of the phase differences ∆ φ1,2 have been found, which are possibly useful for the global decoupling phase loop, or future global decoupling feedback. Analytical descriptions to these 6 quantities are described in the Twiss parameters through the linear coupling's action-angle parameterization, or in coupling coefficient through the linear coupling's Hamiltonian perturbation theory. Dedicated beam experiments are carried out at the Relativistic Heavy Ion Collider (RHIC) to check the global coupling observables from the phase lock loop (PLL) system. The six observables are measured under PLL driving oscillations during the 1-D and 2-D skew quadrupole scans. The experimental results are reported and discussions are given. |
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| TPAP056 | Electron Beam Stability Requirements for Linac-Ring Electron-Ion Colliders | electron, ion, emittance, luminosity | 3363 | ||
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Funding: Work performed under the auspices of the U.S. Department of Energy. |
In recent years, linac-ring electron-ion colliders have been proposed at a number of laboratories around the world. While the linac-ring approach overcomes the beam-beam tuneshift limitation on the electron beam, it also introduces noise into the ion beam, via the beam-beam interaction with electron bunches of slightly fluctuating intensity and transverse size. The effect of these fluctuations is studied using a linearized model of the beam-beam interaction. Upper limits for the rms jitter amplitudes of electron beam parameters for various linac-ring electron-ion colliders are presented. |
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| TPAP057 | Beam-Beam Simulations for the eRHIC Electron Ring | electron, luminosity, resonance, emittance | 3399 | ||
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Funding: Work performed under the auspices of the U.S. Department of Energy. |
To study collisions between polarized electrons and heavy ions or polarized protons at high energy, adding a 10 GeV electron storage ring to the existing RHIC facility is currently under consideration. To achieve high luminosities, vertical beam-beam tuneshift parameters of 0.08 are required for the electron beam. Simulation studies are being performed to study the feasibility of these high tuneshift parameters and to explore the potential for even higher tuneshifts. Recent results of these studies are presented. |
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| TPAP058 | Beam-Beam Simulations for Double-Gaussian Beams | emittance, luminosity, proton, electron | 3405 | ||
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Funding: Work performed under the auspices of the U.S. Department of Energy. |
Electron cooling together with intra-beam scattering results in a transverse distribution that can best be described by a sum of two Gaussians, one for the high-density core and one for the tails of the distribution. Simulation studies are being performed to understand the beam-beam interaction of these double-Gaussian beams. Here we report the effect of low-frequency random tune modulations on diffusion in double-Gaussian beams and compare the effects to those in beam-beam interactions with regular Gaussian beams and identical tuneshift parameters. |
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| TPAT002 | Three-Dimensional Simulation of Large-Aspect-Ratio Ellipse-Shaped Charged-Particle Beam Propagation | focusing, space-charge, vacuum, permanent-magnet | 823 | ||
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Funding: U.S. Department of Energy: Grant No. DE-FG02-95ER40919, Grant No. DE-FG02-01ER54662, Air Force Office of Scientific Research: Grant No. F49620-03-1-0230, and the MIT Deshpande Center for Technological Innovation. |
The three-dimensional trajectory code, OMNITRAK, is used to simulate a space-charge-dominated beam of large-aspect-ratio elliptic cross-section propagating in a non-axisymmetric periodic permanent magnet focusing field. The simulation results confirm theoretical predictions in the paraxial limit. A realistic magnetic field profile is applied, and the beam sensitivity to magnet nonlinearities and misalignments is studied. The image-charge effect of conductor walls is examined for a variety of beam tunnel sizes and geometries. |
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| TPAT003 | Cold-Fluid Equilibrium of a Large-Aspect-Ratio Ellipse-Shaped Charged-Particle Beam in a Non-Axisymmetric Periodic Permanent Magnet Focusing Field | focusing, vacuum, emittance, permanent-magnet | 853 | ||
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Funding: U.S. DOE, Grant: No. DE-FG02-95ER40919,Grant No. DE-FG02-01ER54662, Air Force Office of Scientific Research, Grant No. F49620-03-1-0230, and the MIT Deshpande Center for Technological Innovation. |
A new class of equilibrium is discovered for a large-aspect-ratio ellipse-shaped charged-particle beam in a non-axisymmetric periodic permanent magnet focusing field. A paraxial cold-fluid model is employed to derive the equilibrium flow properties and generalized envelope equations with negligibly small emittance. A periodic beam equilibrium solution is obtained numerically from the generalized envelope equations. It is shown that the beam edges are well confined in both transverse directions, and that the equilibrium beam exhibits a small-angle periodic wobble as it propagates. A two-dimensional particle-in-cell (PIC) code, PFB2D, is used to verify the theoretical predictions in the paraxial limit, and to establish validity under non-paraxial situations and the influence of the conductor walls of the beam tunnel. |
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| TPAT008 | Numerical Dispersion Error Reduction in EM Calculations for Accelerators | electromagnetic-fields, electron, single-bunch, linac | 1114 | ||
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Funding: Deutsches Elektronen-Synchrotron DESY |
In this contribution novel numerical algorithms with no dispersion along the beam axis are investigated. This property is of interest for the long-time calculation of electromagnetic fields in accelerators. Instead of increasing the spatial stencil of the Yee scheme the compared methods modify the time-stepping algorithm.The results are compared on several test examples. As a practical application the electromagnetic field of a very short bunch inside a cavity is calculated. |
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| TPAT014 | A Novel Technique for Multiturn Injection in a Circular Accelerator Using Stable Islands in Transverse Phase Space | injection, extraction, resonance, septum | 1377 | ||
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By applying a time-reversal to the multiturn extraction recently proposed a novel approach to perform multiturn injection is proposed. It is based on the use of stable islands of the horizontal phase space generated by means of sextupoles and octupoles. A particle beam can be injected into stable islands of phase space, and then a slow tune variation allows merging the beam trapped inside the islands. The results of numerical simulations will be presented and discussed in details, showing how to use the proposed approach to generate hollow bunches.
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| TPAT015 | Simulations of Error-Induced Beam Degradation in Fermilab's Booster Synchrotron | booster, emittance, space-charge, synchrotron | 1458 | ||
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Funding: Work supported by the University Research Association, Inc. under U.S. Department of Energy (DOE) contract No. DE-AC02-76-CH03000, and by DOE grant No. DE-FG02-04ER41323 to NIU, and by DOE grant No. DE-FG02-91ER40685 to University of Rochester. |
Individual particle orbits in a beam will respond to both external focusing and accelerating forces as well as internal space-charge forces. The external forces will reflect unavoidable systematic and random machine errors, or imperfections, such as jitter in magnet and radio-frequency power supplies, as well as magnet translation and rotation alignment errors. The beam responds in a self-consistent fashion to these errors; they continually do work on the beam and thereby act as a constant source of energy input. Consequently, halo formation and emittnace growth can be induced, resulting in beam degradation and loss. We have upgraded the ORBIT-FNAL package and used it to compute effects of machine errors on emittance dilution and halo formation in the existing FNAL-Booster synchrotron. This package can be applied to study other synchrotrons and storage rings, as well. |
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| TPAT019 | Discussions on the Cancellation Effect on a Curved Orbit | transverse-dynamics, emittance, space-charge, storage-ring | 1631 | ||
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Funding: Work supported by DOE Contract DE-AC05-84ER40150. |
The canonical formulation and the cancellation effect for bunch dynamics under collective interaction on a curved orbit were presented in Ref. [*]. Some possible controversial representations of the cancellation effect were later addressed by Geloni et al.** In this study, we discuss all the points raised in Ref. [**] based on our canonical treatment, and show how these points can be perceived from the view point of the cancellation picture. *R. Li and Ya. S. Derbenev, Jefferson Laboratory Report No. LJAB-TN-02-054, 2003. **G. Geloni et al., DESY Report No. DESY 03-165, 2003. |
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| TPAT023 | Tests of a 3D Self Magnetic Field Solver in the Finite Element Gun Code MICHELLE | gun, electron, beam-transport, accumulation | 1814 | ||
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Funding: Work supported by ONR. |
We have recently implemented a prototype 3d self magnetic field solver in the finite-element gun code MICHELLE. The new solver computes the magnetic vector potential on unstructured grids. The solver employs edge basis functions in the curl-curl formulation of the finite-element method. A novel current accumulation algorithm takes advantage of the unstructured grid particle tracker to produce a compatible source vector, for which the singular matrix equation is easily solved by the conjugate gradient method. We will present some test cases demonstrating the capabilities of the prototype 3d self magnetic field solver. One test case is self magnetic field in a square drift tube. Another is a relativistic axisymmetric beam freely expanding in a round pipe. |
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| TPAT026 | Synergia: An Advanced Object-Oriented Framework for Beam Dynamics Simultation | background, collective-effects, impedance, hadron | 1925 | ||
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Synergia is a 3-D, parallel, particle-in-cell beam dynamics simulation toolkit. At heart of the software development effort is the integration of two extant object-oriented accelerator modeling frameworks–Impact written in Fortran 90 and mxyptlk written in C++–so that they may be steered by a third, a more flexible human interface framework, written in Python. Recent efforts are focused on the refactoring of the Impact-Fortran 90 codes in order to expose more loosely-coupled interfaces to the Python interface framework.
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| TPAT028 | TRACK: The New Beam Dynamics Code | linac, space-charge, ion, multipole | 2053 | ||
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Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. W-31-109-ENG-38. |
The new ray-tracing code TRACK was developed* to fulfill the special requirements of the RIA accelerator systems. The RIA lattice includes an ECR ion source, a LEBT containing a MHB and a RFQ followed by three SC linac sections separated by two stripping stations with appropriate magnetic transport systems. No available beam dynamics code meet all the necessary requirements for an end-to-end simulation of the RIA driver linac. The latest version of TRACK was used for end-to-end simulations of the RIA driver including errors and beam loss analysis.** In addition to the standard capabilities, the code includes the following new features: i) multiple charge states ii) realistic stripper model; ii) static and dynamic errors iii) automatic steering to correct for misalignments iv) detailed beam-loss analysis; v) parallel computing to perform large scale simulations. Although primarily developed for simulations of the RIA machine, TRACK is a general beam dynamics code. Currently it is being used for the design and simulation of future proton and heavy-ion linacs at TRIUMF, Fermilab, JLAB and LBL. *P.N. Ostroumov and K.W. Shepard. Phys. Rev. ST. Accel. Beams 11, 030101 (2001). **P.N. Ostroumov, V. N. Aseev, B. Mustapha. Phys. Rev. ST. Accel. Beams, Volume 7, 090101 (2004). |
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| TPAT029 | RIA Beam Dynamics: Comparing TRACK to IMPACT | linac, lattice, injection, ion-source | 2095 | ||
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Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. W-31-109-ENG-38. |
In order to benchmark the newly developed beam dynamics code TRACK we have performed comparisons with well established existing codes. During code development, codes like TRANSPORT, COSY, GIOS and RAYTRACE were used to check TRACK's implementation of the different beam line elements. To benchmark the end-to-end simulation of the RIA driver linac, the simulation of the low-energy part (from the ion source to the entrance of the SC linac) was compared with PARMTEQ and found to agree well. For the simulation of the SC linac the code IMPACT is used. Prior to these simulations, the code IMPACT had to be updated to meet the special requirements of the RIA driver linac. Features such as multiple charge state acceleration, stripper simulation and beam collimation were added to the code. IMPACT was also modified to support new types of rf cavities and to include fringe fields for all the elements. This paper will present a comparison of the beam dynamics simulation in the RIA driver linac between the codes TRACK and IMPACT. A very good agreement was obtained which represents another validation of both codes. |
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| TPAT035 | Coherent Synchrotron Radiation from an Electron Beam in a Curved Waveguide | electron, radiation, emittance, synchrotron | 2390 | ||
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Funding: Research supported by the office of Naval Research and the Joint Technology Office. |
The radiation emitted by a pulsed electron beam as it travels on a circular trajectory inside a waveguide is calculated using a 3D simulation. Forward-propagating wave equations for the fields in the waveguide are calculated by a perturbation of the Maxwell equations where the radius of curvature is large compared to the dimensions of the waveguide. These are integrated self-consistently with the distribution of charge in the beam to provide the complete fields (electric and magnetic) for all times during the passage of the beam through the waveguide and therefore are applicable to sections of any length or combinations thereof. The distribution of electrons and their momentum are also modified self-consistently so that the results may be used to estimate the effect of the radiation on the beam quality (emittance and energy spread). |
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| TPAT037 | Simulating the Long-Distance Propagation of Intense Beams in the Paul Trap Simulator Experiment | plasma, ion, focusing, lattice | 2491 | ||
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Funding: Research supported by the U.S. Department of Energy. |
The Paul Trap Simulator Experiment (PTSX) makes use of a compact Paul trap configuration with quadrupolar oscillating wall voltages to simulate the propagation of intense charged particle beams over distances of many kilometers through magnetic alternating-gradient transport systems. The simulation is possible because of the similarity between the transverse dynamics of particles in the two systems. One-component pure cesium ion plasmas have been trapped that correspond to normalized intensity parameters s < 0.8, where s is the ratio of the square of the plasma frequency to twice the square of the average transverse focusing frequency. The PTSX device confines the plasma for hundreds of milliseconds, which is equivalent to beam propagation over tens of kilometers. Results are presented for experiments in which the amplitude of the oscillating confining voltage waveform has been modified as a function of time. A comparison is made between abrupt changes in amplitude and adiabatic changes in amplitude. The effects of varying the frequency are also discussed. A barium ion source and a laser system have been installed and initial measurements made with this system are presented. |
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| TPAT039 | Wavelet-Based Poisson Solver for Use in Particle-in-Cell Simulations | diagnostics, vacuum, plasma, electron | 2601 | ||
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Funding: Work of B.T., D.M. and C.L.B. is supported by Air Force contract FA9471-040C-0199. Work of I.V.P. is supported by the U.S. Department of Energy contract DE-AC03-76SF00098. |
We report on a successful implementation of a wavelet-based Poisson solver for use in 3D particle-in-cell simulations. One new aspect of our algorithm is its ability to treat the general (inhomogeneous) Dirichlet boundary conditions. The solver harnesses advantages afforded by the wavelet formulation, such as sparsity of operators and data sets, existence of effective preconditioners, and the ability simultaneously to remove numerical noise and further compress relevant data sets. Having tested our method as a stand-alone solver on two model problems, we merged it into IMPACT-T to obtain a fully functional serial PIC code. We present and discuss preliminary results of application of the new code to the modelling of the Fermilab/NICADD and AES/JLab photoinjectors. Corresponding author: B.T. (bterzic@nicadd.niu.edu) |
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| TPAT041 | On the Vlasov-Maxwell Equations | acceleration, focusing | 2654 | ||
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There are many interesting physical question which based on of the solution Vlasov-Maxwell Equation (VME). However, the procedure of solve is very difficult and hard. But it is often preferable, on physical grounds, to a common point of view. Such point of view maybe a structure of some solution. We define and discuss the notaion of structure for the distribution function and prove, the structure of the Lorentz force represent the structure of the one. At the time of the discovery of the integrable systems the question of VME integrability had been considered. Moreover, as example, we consider, by means of this approach, the relation integrability and dispersion with a spectra of Vlasov's operat.
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| TPAT047 | A Space Charge Compensation Study of Low Energy Hydrogen Ion Beams | space-charge, ion, electron, emittance | 2947 | ||
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Funding: Work supported by the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" programme (CARE, contract number RII3-CT-2003-506395). |
High-power accelerators are being studied for several projects including accelerator driven neutron or neutrino sources. The low energy part of these facilities has to be carefully optimized to match the beam requirements of the higher energy parts. The complexity of high intensity beam dynamics in the low energy line is essentially due to the non-linear space charge effects. The PIC code CARTAGO* has been developed in order to simulate the beam transport at low energy including the temporal evolution effects of the space charge compensation. This paper relates the structure and the numerical methods of a 2D (r,z) new version of the code. The effects of the longitudinal space charge, the image charge and external 2D (r,z) magnetic field were included. The results of H+ and H- beam transports using solenoid lenses are discussed. Space charge compensation degrees are given for each studied cases. *A. Ben Ismail et al., in Space Charge Compensation in Low Energy Proton Beams, proceeding of the International Linear Accelerator Conference, Lübeck, 2004. |
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| TPAT049 | Comparison of Beam Dynamic in Different Superconducting Options of Low Energy High Intense Linac | focusing, quadrupole, linac, space-charge | 3058 | ||
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Funding: We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" program (CARE, contract number RII3-CT-2003-506395). |
At present the superconducting proton linacs have obvious applications in energy range ~100-1000 MeV. For the lower energy the comprehensive investigations are required. In this article the various variants of superconducting options from 3MeV up to 100MeV are discussed. The considered variants include both the conventional combination of half-wave and spoke cavity with quadrupoles and new schemes. In conclusion the table of major parameters for different structures is given. |
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| TPAT050 | Beam Dynamics Design of the L3BT for J-PARC | injection, space-charge, linac, emittance | 3091 | ||
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L3BT is beam transportation line from the linac to the 3-GeV RCS which is the part of the accelerators for the High-Intensity Proton Accelerator Facility Project, J-PARC.In this paper, especially results of the beam simulation of the injection section of the L3BT are presented. And the matching of rms envelopes and dispersion function for space charge dominated beams are also discussed.
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| TPAT054 | Dispersion Matching of a Space Charge Dominated Beam at Injection into the CERN PS Booster | optics, space-charge, injection, booster | 3283 | ||
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In order to match the dispersion at injection into the CERN PS Booster, the optics of the injection line was simulated using two different codes (MAD and TRACE). The simulations were benchmarked versus experimental results. The model of the line was then used to re-match the dispersion. Experimental results are presented for different optics of the line. Measurements with varying beam current show the independence of the measured quantity of space-charge effects.
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| TPAT055 | On Start to End Simulation and Modeling Issues of the Megawatt Proton Beam Facility at PSI | space-charge, cyclotron, injection, proton | 3319 | ||
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At the Paul Scherrer Institut (PSI) we routinely extract a one megawatt (CW) proton beam out of our 590 MeV Ring Cyclotron. In the frame of the ongoing upgrade program, large scale simulations have been undertaken in order to provide a sound basis to assess the behaviour of very intense beams in cyclotrons. The challenges and attempts towards massive parallel three dimensional start-to- end simulations will be discussed. The used state of the art numerical tools (mapping techniques, time integration, parallel FFT and finite element based multigrid Poisson solver) and their parallel implementation will be discussed. Results will be presented in the area of: space charge dominated beam transport including neighbouring turns, eigenmode analysis to obtain accurate electromagnetic fields in large the rf cavities and higher order mode interaction between the electromagnetic fields and the particle beam. For the problems investigated so far a good agreement between theory i.e. calculations and measurements is obtained.
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| TPAT058 | Calculation of Electron Beam Potential Energy from RF Photocathode Gun | gun, electron, space-charge, acceleration | 3441 | ||
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Funding: U.S. Department of Energy. |
In this paper, we consider the contribution of potential energy to beam dynamics as simulated by PARMELA at low energies (10 - 30MeV). We have developed a routine to calculate the potential energy of the relativistic electron beam using the static coulomb potential in the rest frame (first order approximation as in PARMELA). We found that the potential energy contribution to the beam dynamics could be very significant, particularly with high charge beams generated by an RF photocathode gun. Our results show that when the potential energy is counted correctly and added to the kinetic energy from PARMELA, the total energy is conserved. Simulation results of potential and kinetic energies for short beams (~1 mm) at various charges (1 - 100 nC) generated by a high current RF photocathode gun are presented. |
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| TPAT059 | Space Charge Experiments and Simulation in the Fermilab Booster | booster, space-charge, injection, resonance | 3453 | ||
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Funding: Scientific Discovery through Advanced Computing project, "Advanced Computing for 21st Century Accelerator Science and Technology," U.S. DOE/SC Office of High Energy Physics and the Office of Advanced Scientific Computing Research. |
We have studied space charge effects in the Fermilab Booster. Our studies include investigation of coherent and incoherent tune shifts and halo formation. We compare experimental results with simulations using the 3-D space charge package Synergia. |
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| TPAT060 | Overview of the Synergia 3-D Multi-Particle Dynamics Modeling Framework | booster, space-charge, emittance, injection | 3490 | ||
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Funding: Scientific Discovery through Advanced Computing project, "Advanced Computing for 21st Century Accelerator Science and Technology," U.S. DOE/SC Office of High Energy Physics and the Office of Advanced Scientific Computing Research. |
High precision modeling of space-charge effects is essential for designing future accelerators as well as optimizing the performance of existing machines. Synergia is a high-fidelity parallel beam dynamics simulation package with fully three dimensional space-charge capabilities and a higher-order optics implementation. We describe the Synergia framework and model benchmarks we obtained by comparing to semi-analytic results and other codes. We also present Synergia simulations of the Fermilab Booster accelerator and comparisons with experiment. |
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| TPAT061 | Accurate Iterative Analysis of the K-V Equations | quadrupole, lattice, emittance, focusing | 3535 | ||
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Funding: Supported in part by the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. |
Previous solutions of the K-V equations have either yielded poor accuracy or have been complex and difficult to follow. We describe a new approach, simple in concept, easy to use, with accuracy substantially improved over previous treatments. The results are given in the same form as the smooth approximation but include a few correction terms obtained from the field gradient integrated along the axis of a quadrupole cell. The input quantities–quadrupole field, beam current, and emittance–yield the average beam radius, the maximum envelope excursion, and the depressed and undepressed tunes. For all values of the input parameters, the results are much closer to the exact values from simulations than are results from the smooth approximation. For example, with the parameters adjusted for an exact phase advance of 83.4 degrees and 50% tune depression, both tunes are in error by less than 0.5%–over 22 times better than the smooth approximation. The error in maximum radius is 0.04%, improved by a factor of 80. The new method and its application to a wide range of cases will be presented. |
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| TPAT062 | Uncorrelated Energy Spread and Longitudinal Emittance for a Photoinjector Beam | space-charge, gun, emittance, electron | 3570 | ||
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Longitudinal phase space properties of a photoinjector beam are important in many areas of high-brightness beam applications such as bunch compression, transverse-to-longitudinal emittance exchange, and high-gain free-electron lasers. In this paper, we discuss both the rf and the space charge contributions to the uncorrelated energy spread of the beam generated from a laser-driven rf gun. We compare analytical expressions for the uncorrelated energy spread and the longitudinal emittance with numerical simulations and recent experimental results.
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| TPAT065 | Damping Transverse Instabilities in the Tevatron Using AC Chromaticity | proton, synchrotron, sextupole, damping | 3665 | ||
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Funding: Operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the U.S. Department of Energy. |
Several papers*,** have suggested possibility of using varying chromaticity to damp the head-tail instability. We test this by cycling the chromaticity sextupole magnets in the Tevatron near the synchrotron frequency to see if the head-tail stability threshold is increased. Further we compare the turn-by-turn evolution of a bunch slice in the presence of varying chromaticity to a model previously developed. *W.-H. Cheng, A. M. Sessler, and J. S. Wurtele, Phys. Rev. Lett. 78, 4565 (1997). **T. Nakamura in Proceedings of the 1995 IEEE Particle Accelerator Conference (IEEE, Dallas, 1995), Vol. 5, p. 3100. |
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| TPAT066 | Significance of Space Charge and the Earth Magnetic Field on the Dispersive Characteristics of a Low Energy Electron Beam | space-charge, emittance, lattice, electron | 3691 | ||
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Funding: This work is funded by U.S. Dept. of Energy grant numbers DE-FG02-94ER40855 and DE-FG02-92ER54178. |
The combination of energy spread and space charge provides a rich domain for interesting beam dynamics that are currently not well understood. The University of Maryland Electron Ring (UMER) [1] is a small scaled ring designed to probe the little-known regions of higher beam intensities using low-energy electrons. As such, design, commissioning and operation of UMER present many challenges, some quite novel. For example the UMER beam energy of 10 keV makes the beam very sensitive to the Earth magnetic field, which we can fortunately use to assist in bending the beam. This paper presents a systematic simulation study of the interaction of space charge and energy spread, with and without the earth magnetic field. *"Commissioning of the University of Maryland Electron Ring (UMER)," S. Bernal, et al., this conference. |
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| TPAT067 | Study of Longitudinal Space-Charge Wave Dynamics in Space-Charge Dominated Beams | space-charge, gun, electron, ion | 3712 | ||
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Funding: Work supported by the U.S. Department of Energy, Office of Science. |
Understanding the dynamics of longitudinal space- charge waves is very important for advanced accelerator research. Although analytical solutions of space-charge wave equations based on the cold fluid model exist in one dimension, there are few results for two-dimensional wave evolution. One-dimensional theory predicts two eigen solutions, given an initial perturbation. One is called the fast wave, which moves toward the beam head in the beam frame and the other is termed the slow wave, which moves backward in the beam frame. In this paper, we report experimental results of space charge wave studies conducted on a 2.3 meter long straight beam line at the University of Maryland. An energy analyzer is used to directly measure the energy of space-charge waves at the end of the transport line, which demonstrates the decomposition of an initial current perturbation into a slow wave and a fast wave. A PIC code, WARP [1], is used to simulate this experiment and the behavior of longitudinal waves in space-charge dominated beams in an R-Z geometry. Simulations shown here also demonstrate if the initial current and velocity perturbation strengths are chosen properly, only fast or slow waves could be selectively generated. |
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| TPAT068 | A Fast Faraday Cup for the Neutralized Drift Compression Experiment | ion, plasma, electron, target | 3765 | ||
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Funding: Research supported by the U.S. Department of Energy. |
Heavy ion drivers for high energy density physics applications and inertial fusion energy use space-charge-dominated beams which require longitudinal bunch compression in order to achieve sufficiently high beam intensity at the target. The Neutralized Drift Compression Experiment-1A (NDCX-1A) at Lawrence Berkeley National Laboratory (LBNL) is used to determine the effective limits of neutralized drift compression. NDCX-1A investigates the physics of longitudinal drift compression of an intense ion beam, achieved by imposing an initial velocity tilt on the drifting beam and neutralizing the beam's space-charge with background plasma. Accurately measuring the longitudinal compression of the beam pulse with high resolution is critical for NDCX-1A, and an understanding of the accessible parameter space is modeled using the LSP particle-in-cell (PIC) code. The design and preliminary experimental results for an ion beam probe which measures the total beam current at the focal plane as a function of time are summarized. |
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| TPAT069 | Numerical Studies of Electromagnetic Instabilities in Intense Charged Particle Beams with Large Energy Anisotropy | plasma, focusing, heavy-ion, vacuum | 3780 | ||
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Funding: Research supported by the U.S. Department of Energy. |
In intense charged particle beams with large energy anisotropy, free energy is available to drive transverse electromagnetic Weibel-type instabilities. Such slow-wave transverse electromagnetic instabilities can be described by the so-called Darwin model, which neglects the fast-wave portion of the displacement current. The Weibel instability may also lead to an increase in the longitudinal velocity spread, which would make the focusing of the beam difficult and impose a limit on the minimum spot size achievable in heavy ion fusion experiments. This paper reports the results of recent numerical studies of the Weibel instability using the Beam Eigenmode And Spectra (bEASt) code for space-charge-dominated, low-emittance beams with large tune depression. To study the nonlinear stage of the instability, the Darwin model is being developed and incorporated into the Beam Equilibrium Stability and Transport(BEST) code. |
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| TPAT072 | Long-Term Simulation of Beam-Beam Effects in the Tevatron at Collision Energy | lattice, coupling, antiproton, beam-beam-effects | 3871 | ||
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The weak-strong beam-beam effect is expected substantially to contribute to the degradation of beam lifetimes in the Tevatron at collision energy. We have expanded an existing multi-processor code (which previously was applied to the Tevatron at injection energy* to include chromatic and non-linear lattice effects as well as a fully-coupled treatment of the lattice in different approximations.** We obtain lifetime predictions by doing temporal statistics on the tracking results of a weighted macroparticle distribution and fitting it to a class of solutions for the diffusion equation. We present typical results of parameter scans.
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*A. Kabel, Y. Cai, B. Erdelyi, T. Sen, M. Xiao; Proceedings of PAC03. **A. Kabel, this Conference. |
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| TPAT076 | Measurement of the Luminous-Region Profile at the PEP-II IP, and Application to e± Bunch-Length Determination | luminosity, monitoring, collider, optics | 3973 | ||
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The three-dimensional luminosity distribution at the interaction point (IP) of the SLAC B-Factory is measured continuously, using e+e- –> e+e- and e+e –> mu+mu- events reconstructed online in the silicon tracker of the BaBar detector. The centroid of the transverse luminosity profile provides a very precise and reliable monitor of medium- and long-term orbit drifts at the IP. The longitudinal centroid is sensitive to variations in the relative RF phase of the colliding beams, both over time and differentially along the bunch train. The measured horizontal r.m.s. width of the distribution is consistent with a sizeable dynamic-beta effect; it is also useful as a benchmark of strong-strong beam-beam simulations. The longitudinal luminosity distribution depends on the e± bunch lengths and vertical IP beta-functions, which can be different in the high- and low-energy rings. Using independent estimates of the beta-functions, we analyze the longitudinal shape of the luminosity distribution in the presence of controlled variations in accelerating RF voltage and/or beam current, to extract separate measurements of the e+ and e- bunch lengths.
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| TPAT077 | Beam-Beam Study on the Upgrade of Beijing Electron Positron Collider | luminosity, collider, injection, positron | 4000 | ||
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It is an important issue to study the beam-beam interaction in the design and performance of such a high luminosity collider as BEPCII, the upgrade of Beijing Electron Positron Collider. The weak-strong simulation is generally used during the design of a collider. For performance a large scale tune scan, the weak-strong simulation studies on beam-beam interaction were done, and the geometry effects were taken into account The strong-strong simulation studies were done for investigating the luminosity goal and the dependence of the luminosity on the beam parameters.
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| TPAT078 | Coherent Beam-Beam Modes in the CERN Large Hadron Collider (LHC) for Multiple Bunches, Different Collisions Schemes and Machine Symmetries | damping, coupling, emittance, dipole | 4030 | ||
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In the LHC almost 3000 bunches in each beam will collide near several experimental regions and experience head-on as well as long range beam-beam interactions. In addition to single bunch phenomena, coherent bunch oscillations can be excited. Due to the irregular filling pattern and the unsymmetric collision scheme, a large number of possible modes must be expected, with possible consequences for beam measurements. To study these effects, a simulation program was developped which allows to evaluate the interaction of many bunches. It is flexible enough to easily implement any possible bunch configuration and collision schedule and also to study the effect of machine imperfections such as optical asymmetries. First results will be presented and future developments are discussed.
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| TPAT079 | Importance of the Linear Coupling and Multipole Compensation of Long-Range Beam-Beam Interactions In Tevatron | emittance, multipole, coupling, beam-beam-effects | 4039 | ||
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Funding: The US Department of Energy under Grant No. DE-FG02-04ER41288. |
In Tevatron, serious long-range beam-beam effects are due to many parasitic collisions that are distributed around the ring. Because of this non-localized nature of long-range beam-beam interactions, the multipole compensation with one-turn or sectional maps aims a global compensation of long-range beam-beam interactions. Since nonlinear beam dynamics in a storage ring can usually be described by a one-turn map that contains all global information of system nonlinearities, by minimizing nonlinear terms of the maps order-by-order with a few groups of multipole correctors, one could reduce the nonlinearity globally. Since a large beam separation is typical at parasitic points, in the phase-space region that is relevant to the beam, long-range beam-beam interactions can be expanded into a Taylor series around the beam separation and be included into the one-turn map for the global compensation. To examine the effect of this multipole compensation scheme, the emittance growth of both p and pbar beam in Tevatron were studied with a beam-beam simulation. The result showed that the multipole compensation can significantly reduces the emittance growth of the pbar beam due to long-range beam-beam interactions. |
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| TPAT083 | Computational Study of the Beam-Beam Effect in Tevatron Using the LIFETRAC Code | luminosity, emittance, optics, antiproton | 4117 | ||
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Funding: Work supported by the Universities Research Assos., Inc., under contract DE-AC02-76CH03000 with the U.S. Dept. of Energy. |
Results of a comprehensive numerical study of the beam-beam effect in the Tevatron are presented including the dependence of the luminosity lifetime on the tunes, chromaticity and optics errors. These results help to understand the antiproton emittance blow-up routinely observed in the Tevatron after the beams are brought into collision. To predict a long term luminosity evolution, the diffusion rates are increased to represent long operation time (~day) by using a small number of simulated turns. To justify this approach, a special simulation study of interplay between nonlinear beam-beam resonances and diffusion has been conducted. A number of ways to mitigate the beam-beam effects are discussed, such as increasing bunch spacing, separation between the beams and beam-beam compensation with electron lenses. |
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| TPAT084 | LIFETRAC Code for the Weak-Strong Simulation of the Beam-Beam Effect in Tevatron | betatron, optics, antiproton, quadrupole | 4138 | ||
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Funding: Work supported by the Universities Research Assos., Inc., under contract DE-AC02-76CH03000 with the U.S. Dept. of Energy. |
A package of programs for weak-strong simulation of beam-beam effects in hadron colliders is described. Accelerator optics parameters relevant to the simulation are derived from beam measurements and calculations are made using OptiM optics code. The key part of the package is the upgraded version of the LIFETRAC code which now includes 2D coupled optics, chromatic modulation of beta-functions, non-Gaussian shape of the strong bunches and non-linear elements for beam-beam compensation. Parallel computations are used and in the case of the Tevatron (2 main IPs + 70 parasitic IPs) the code has a productivity of ~1·1010 particles*turns/day on a 32-node cluster of Pentium IV 1.8 GHz processors. |
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| TPAT085 | Development of a Beam-Beam Simulation Code for e+e- Colliders | luminosity, synchrotron, beam-beam-effects, positron | 4176 | ||
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Funding: Chinese National Foundation of Natural Sciences, contract 10275079 JSPS Core University Program |
BEPC will be upgraded into BEPCII, and the luminosity will be about 100 times higher. We developed a three dimensional strong-strong PIC code to study the beam-beam effects in BEPCII. The transportation through the arc is the same as that in Hirata's weak-strong code. The beam-beam force is computed directly by solving the Poisson equation using the FACR method, and the boundary potential is computed by circular convolution. The finite bunch length effect is included by longitudinal slices. An interpolation scheme is used to reduce the required slice number in simulations. The standard message passing interface (MPI) is used to parallelize the code. The computing time increases linearly with (n+1), where n is the slice number. The calculated luminosity of BEPCII at the design operating point is less than the design value. The best area in the tune space is near (0.505,0.57) according to the survey, where the degradation of luminosity can be improved. |
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| TPAT087 | The Effect of Magnetic Field Errors on Dynamical Friction in Electron Coolers | electron, ion, positron, luminosity | 4206 | ||
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Funding: Work supported by US DOE grants DE-FG03-01ER83313 and DE-FG03-95ER40926. |
A proposed luminosity upgrade to the Relativistic Heavy Ion Collider (RHIC) includes a novel electron cooling section,* which would use ~55 MeV electrons to cool fully-ionized 100 GeV/nucleon gold ions. A strong (1-5 T) solenoidal field will be used to magnetize the electrons and thus enhance the dynamical friction force on the ions. The physics of magnetized friction is being simulated for RHIC parameters, using the VORPAL code.** Most theoretical treatments for magnetized dynamical friction do not consider the effect of magnetic field errors, except in a parametric fashion.*** However, field errors can in some cases dramatically reduce the velocity drag and corresponding cooling rate. We present a simple analytical model for the magnetic field errors, which must be Lorentz transformed into the beam frame for use in our simulations. The simulated dynamical friction for the case of a perfect solenoidal field will be compared with results from this new model, for parameters relevant to RHIC. *Fedotov et al., Proc. 33rd ICFA Adv. Beam Dynamics Workshop (2004). **Nieter & Cary, J. Comp. Phys. 196 (2004). ***Parkhomchuk, Nucl. Instr. Meth. Phys. Res. A 441 (2000). |
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| TPAT089 | Cooling Dynamics Studies and Scenarios for the RHIC Cooler | electron, ion, luminosity, emittance | 4236 | ||
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Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-98CH10886 |
In this paper, we discuss various cooling dynamics studies for RHIC, such as an equilibrium process between intra-beam scattering within ion bunch and electron cooling, critical number of electrons needed, magnetized cooling logarithm and resulting requirements on parameters of electron beam, effects of solenoid errors, etc. We also present simulations of various possibilities of using electron cooling at RHIC, which includes cooling at the top energy, pre-cooling at low energy, aspects of transverse and longitudinal cooling and their impact on the luminosity. Electron cooling at various collision energies both for heavy ions and protons is also discussed. |
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| TPAT090 | Simulations of High-Energy Electron Cooling | electron, ion, luminosity, emittance | 4251 | ||
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Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-98CH10886. |
High-energy electron cooling of RHIC presents many unique features and challenges. An accurate estimate of the cooling times requires a detailed calculation of the cooling process, which takes place simultaneously with various diffusive mechanisms in RHIC. In addition, many unexplored effects of high-energy cooling in a collider complicate the task of getting very accurate estimates of cooling times. To address these high-energy cooling issues, a detailed study of cooling dynamics based on computer codes is underway at Brookhaven National Laboratory. In this paper, we present an update on code development and its application to the high-energy cooling dynamics studies for RHIC. |
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| TPAT091 | IBS for Ion Distribution Under Electron Cooling | lattice, ion, luminosity, emittance | 4263 | ||
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Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-98CH10886. |
Standard models of the intra-beam scattering (IBS) are based on the growth of the rms beam parameters for a Gaussian beam distribution. As a result of electron cooling, the core of beam distribution is cooled much faster than the tails, producing a denser core. Formation of such a core is an important feature since it plays dominant role in the luminosity increase. A simple use of standard rms-based IBS approach may significantly underestimate IBS for the beam core. A detailed treatment of IBS, which depends on individual particle amplitudes, was recently proposed by Burov,* with an analytic formulation done for a Gaussian distribution. However, during the cooling process the beam distribution quickly deviates from a Gaussian profile. To understand the extent of the dense core formation in the ion distribution, the "core-tail" model for IBS, based on the diffusion coefficients for bi-Gaussian distributions, was employed in cooling studies for RHIC. In addition, the standard IBS theory was recently reformulated for rms parameters growth of a bi-Gaussian distribution by Parzen.** In this paper, we compare various approaches to IBS treatment for such distribution. Its impact on the luminosity is also discussed. *A. Burov, FERMILAB-TM-2213 (2003). **G. Parzen, Tech Note C-AD/AP/150 (2004). |
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| TPAT092 | Numerical Studies of the Friction Force for the RHIC Electron Cooler | electron, ion, plasma, space-charge | 4278 | ||
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Funding: Work performed under the auspices of the U.S. Department of Energy. |
Accurate calculation of electron cooling times requires an accurate description of the dynamical friction force. The proposed RHIC cooler will require ~55 MeV electrons, which must be obtained from an RF linac, leading to very high transverse electron temperatures. A strong solenoid will be used to magnetize the electrons and suppress the transverse temperature, but the achievable magnetized cooling logarithm will not be large. Available formulas for magnetized dynamical friction are derived in the logarithmic approximation, which is questionable in this regime. In this paper, we explore the magnetized friction force for parameters of the RHIC cooler, using the VORPAL code.* VORPAL can simulate dynamical friction and diffusion coefficients directly from first principles.** Various aspects of the friction force, such as dependence on magnetic field, scaling with ion charge number and others, are addressed for the problem of high-energy electron cooling in the RHIC regime. *C. Nieter & J.R. Cary, J. Comp. Phys. 196 (2004), p. 448. **D.L. Bruhwiler et al., Proc. 33rd ICFA Advanced Beam Dynamics Workshop (2004). |
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| TOAB009 | Generation of Short X-Ray Pulses Using Crab Cavities at the Advanced Photon Source | optics, radiation, emittance, sextupole | 668 | ||
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Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. |
There is growing interest within the user community to utilize the pulsed nature of synchrotron radiation from storage ring sources. Conventional third-generation light sources can provide pulses on the order of 100 ps but typically cannot provide pulses of about 1 ps that some users now require to advance their research programs. However, it was recently proposed by A. Zholents et al. to use rf orbit deflection to generate subpicosecond X-ray pulses.* In this scheme, two crab cavities are used to deliver a longitudinally dependent vertical kick to the beam, thus exciting longitudinally correlated vertical motion of the electrons. This makes it possible to spatially separate the radiation coming from different longitudinal parts of the beam. An optical slit can then be used to slice out a short part of the radiation pulse, or an asymetrically cut crystal can be used to compress the radiation in time. In this paper, we present a feasibility study of this method applied to the Advanced Photon Source. We find that the pulse length can be decreased down to a few-picosecond range using superconducting crab cavities. *A. Zholents et al., NIM A 425, 385 (1999). |
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| TOPC005 | Transverse Emittance Blow-Up Due to the Operation of Wire Scanners, Analytical Predictions and Measurements | emittance, scattering, proton, betatron | 437 | ||
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Wire Scanner monitors are used in the CERN accelerators to measure the transverse beam size. In the SPS and the LHC they will serve as calibration devices for other emittance monitors. The PSB, PS and SPS are equipped with scanners which move through the beam a 30 um wire, with a speed that can vary between 0.4 to 20 m/s. During each scan, the beam suffers an emittance blow up, due to multiple Coulomb scattering of the beam protons on the lattice nuclei of the wire material. The effect depends on the particles' energy, the betatron function at the monitor location and on the wire characteristics (material, diameter and speed). In this paper we will present a comparison of the analytically predicted emittance increase caused by the instruments and a number of experimental measurements. For the small LHC beams the relative emittance blow-up can exceed a few 10e-2.
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| TPPE010 | A Parallel 3D Model for the Multi-Species Low Energy Beam Transport System of the RIA Prototype ECR Ion Source VENUS | ion, ion-source, beam-transport, extraction | 1183 | ||
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Funding: This work was supported by the Director, Office of Energy Research, Office of High Energy and Nuclear Physics, Nuclear Physics Division of the U.S. DOE under Contract DE AC03-76SF00098. |
The driver linac of the proposed Rare Isotope Accelerator (RIA) requires a great variety of high intensity, high charge state ion beams. In order to design and optimize the low energy beam line optics of the RIA front end, we have developed a new parallel three-dimensional model to simulate the low energy, multi-species beam transport from the ECR ion source extraction region to the focal plane of the analyzing magnet. A multi-section overlapped computational domain has been used to break the original transport system into a number of independent subsystems. Within each subsystem, macro-particle tracking is used to obtain the charge density distribution in this subdomain. The three-dimensional Poisson equation is solved within the subdomain and particle tracking is repeated until the solution converges. Two new Poisson solvers based on a combination of the spectral method and the multigrid method have been developed to solve the Poisson equation in cylindrical coordinates for the beam extraction region and in the Frenet-Serret coordinates for the bending magnet region. Some test examples and initial applications will also be presented. |
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| TPPE013 | Simulations of Solenoid and Electrostatic Quadrupole Focusing of High Intensity Beams from ECR Ion Source at NSCL | focusing, quadrupole, space-charge, emittance | 1336 | ||
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Solenoidal focusing has been widely used to focus beams at various injectors for its axisymmetric focusing with reasonable effectiveness. Experiments and simulations have shown that space charge effects can significantly deteriorate the beam quality when solenoidal focusing is used in a multi-component beam. This is due to the magnetic focusing strength dependence on the beam charge-to-mass ratio. Electrostatic quadrupole focusing has been explored as an alternate option at NSCL for the injection line of the superconducting cyclotron. We present in this paper the results of simulations for both systems. The electrostatic quadrupoles have been optimized to reduce the radial dependent aberrations and to increase the transmission efficiency.
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| TPPE021 | Simulation Studies of Diffusion-Release and Effusive-Flow of Short-Lived Radioactive Isotopes | target, ion, ion-source, vacuum | 1739 | ||
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Funding: Research supported by the U.S. DOE under contract DE-AC05-00OR22725 with UT-Battelle, LLC. |
Delay times associated with diffusion release from targets and effusive-flow transport of radioactive isotopes to ion sources are principal intensity limiters at ISOL-based radioactive ion beam facilities, and simulation studies with computer models are cost effective methods for designing targets and vapor transport systems with minimum delay times to avoid excessive decay losses of short lived ion species. A finite difference code, Diffuse II, was recently developed at the Oak Ridge National Laboratory to study diffusion-release of short-lived species from three principal target geometries. Simulation results are in close agreement with analytical solutions to Fick’s second equation. Complementary to the development of Diffuse II, the Monte-Carlo code, Effusion, was developed to address issues related to the design of fast vapor transport systems. Results, derived by using Effusion, are also found to closely agree with experimental measurements. In this presentation, the codes will be used in concert to make realistic estimations of intensities of a number of short-lived isotopes that are candidates for use in future nuclear physics and nuclear astrophysics experiments at the HRIBF. |
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| TPPE023 | Development and Performance of a Proton and Deuteron ECR Ion Source | proton, ion-source, ion, emittance | |||
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A 5mA proton and deuteron rf source is under development at ACCEL. This source will provide the front end of our superconducting proton/deuteron linear accelerator. The design of the source is based on the proven AECL design of a 100 mA proton source. The paper will describe the design of the source and the layout of the test bench currently set up at ACCEL to characterize the source. Results of the beam dynamic simulations performed to optimize the source geometry based on KOBRA 3D will be presented and compared with first measurement results.
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| TPPE029 | Measurements of Ion Selective Containment on the RF Charge Breeder Device BRIC | ion, electron, extraction, vacuum | 2065 | ||
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Funding: Istituto Nazionale Fisica Nucleare. |
The "charge state breeder" BRIC (BReeding Ion Charge) is based on an EBIS source and it is designed to accept Radioactive Ion Beam (RIB) with charge +1, in a slow injection mode, to increase their charge state up to +n. BRIC has been developed at the INFN section of Bari (Italy) during these last 3 years with very limited funds. Now, it has been assembled at the LNL (Italy) where are in progress the first tests as stand alone source. The new feature of BRIC, with respect to the classical EBIS, is given by the insertion, in the ion drift chamber, of a Radio Frequency (RF) Quadrupole aiming to filtering the unwanted elements and then making a more efficient containment of the wanted ions. In this contribution, the measurements of the selective effect on the ion charge state containement of the RF quadrupole field, applied on the ion chamber, will be reported and discussed. The ion charge state analisys of the ions trapped in BRIC seem confirm, as foreseen by simulation results carried out previously, that the selective containment can be obtained. A modification of the collector part to improve the ion extraction of BRIC will be also presented and shortly discussed. |
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| TPPE032 | Particle-in-Cell Simulations of the VENUS Ion Beam Transport System | ion, extraction, ion-source, beam-transport | 2236 | ||
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Funding: This work was supported by the Director, Office of Energy Research, Office of High Energy and Nuclear Physics, Nuclear Physics Division of the U.S. DOE under Contract DE AC03-76SF00098 |
The next-generation superconducting ECR ion source VENUS serves as the prototype injector ion source for the linac driver of the proposed Rare Isotope Accelerator (RIA). The high-intensity heavy ion beams required by the RIA driver linac present significant challenges for the design and simulation of an ECR extraction and low energy ion beam transport system. Extraction and beam formation take place in a strong (up to 3T) axial magnetic field, which leads to significantly different focusing properties for the different ion masses and charge states of the extracted beam. Typically, beam simulations must take into account the contributions of up to 30 different charge states and ion masses. Two three-dimensional, particle-in-cell codes developed for other purposes, IMPACT and WARP, have been adapted in order to model intense, multi-species DC beams. A discussion of the differences of these codes and the advantages of each in the simulation of the low energy beam transport system of an ECR ion source is given. Direct comparisons of results from these two codes as well as with experimental results from VENUS are presented. |
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| TPPE035 | Efficiency of the Fermilab Electron Cooler’s Collector | electron, cathode, permanent-magnet, gun | 2387 | ||
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Funding: Operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the United States Department of Energy. |
The newly installed high-energy Recycler Electron Cooling system (REC) at Fermilab will work at an electron energy of 4.34 MeV and a DC beam current of 0.5 A in an energy recovery scheme. For reliable operation of the system, the relative beam current loss must be maintained to levels < 3.e-5. Experiments have shown that the loss is determined by the performance of the electron beam collector, which must retain secondary electrons generated by the primary beam hitting its walls. As a part of the Electron cooling project, the efficiency of the collector for the REC was optimized, both with dedicated test bench experiments and on two versions of the cooler prototype. We find that to achieve the required relative current loss, an axially-symmetric collector must be immersed in a transverse magnetic field with certain strength and gradient prescriptions. Collector efficiencies in various magnetic field configurations, including without a transverse field on the collector, are presented and discussed |
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| TPPE038 | Thermal Hydraulic Design of PWT Accelerating Structures | electron, feedback, linear-collider, collider | 2524 | ||
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Funding: Work supported by DOE SBIR Grant No. DE-FG02-03ER83846. |
Microwave power losses on the surfaces of accelerating structures will transform to heat which will deform the structures if it is not removed in time. Thermal hydraulic design of the disk and cooling rods of a Plane Wave Transformer (PWT) structure is presented. Experiments to measure the hydraulic (pressure vs flow rate) and cooling (heat removed vs flow rate) properties of the PWT disk are performed, and results compared with simulations using Mathcad models and the COSMOSM code. Both experimental and simulation results showed that the heat deposited on the structure could be removed effectively using specially designed water-cooling circuits and the temperature of the structure could be controlled within the range required. |
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| TPPE039 | Development of Advanced Models for 3D Photocathode PIC Simulations | electron, laser, cathode, gun | 2583 | ||
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Funding: This work is supported by the U.S. DOE, use of NERSC supercomputer facilities, and the Joint Technology office (JTO). |
Codes for simulating photocathode electron guns invariably assume the emission of an idealized electron distribution from the cathode, regardless of the particular particle emission model that is implemented. The output of such simulations, a relatively clean and smooth distribution with very little variation as a function of the azimuthal angle, is inconsistent with the highly irregular and asymmetric electron bunches seen in experimental diagnostics. To address this problem, we have implemented a recently proposed theoretical model* that takes into account detailed solid-state physics of photocathode materials in the VORPAL particle-in-cell code.** Initial results from 3D simulations with this model and future research directions will be presented and discussed. *K.L. Jensen, D.W. Feldman, M. Virgo, and P.G. O'Shea, Phys. Rev. ST Accel. Beams, 6:083501, 2003. **C. Nieter and J.R. Cary, J. Comp. Phys. 196 (2004), p. 448. |
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| TPPE045 | Normal-Conducting High Current RF Photoinjector for High Power CW FEL | vacuum, coupling, emittance, rfq | 2866 | ||
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An RF photoinjector capable of producing high average current with low emittance and energy spread is a key enabling technology for high power CW FEL. The design of a 2.5-cell, pi-mode, 700-MHz normal-conducting RF photoinjector cavity with magnetic emittance compensation is completed. With average gradients of 7, 7, and 5 MV/m in its three accelerating cells, the photoinjector will produce a 2.5-MeV electron beam with 3-nC charge per bunch and transverse rms emittance below 7 mm-mrad. Electromagnetic modeling has been used extensively to optimize ridge-loaded tapered waveguides and RF couplers, and led to a new, improved coupler iris design. The results, combined with a thermal and stress analysis, show that the challenging problem of cavity cooling can be successfully solved. Fabrication of a demo 100-mA (at 35 MHz bunch repetition rate) photoinjector is underway. The design is scalable to higher average currents by increasing the electron bunch repetition rate, and provides a path to a MW-class FEL. This paper presents the cavity design and details of RF coupler modeling.
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| TPPE046 | Computer Simulation of the UMER Gridded Gun | cathode, gun, electron, space-charge | 2908 | ||
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Funding: This work is supported by the U.S. DOE under contract Nos. DE-FG02-02ER54672 and DE-FG02-94ER40855 at the UMD, and DE-AC03-76SF00098 at LBNL and W-7405-ENG-48 at LLNL. |
The electron source in the University of Maryland Electron Ring (UMER) injector employs a grid 0.15 mm from the cathode to control the current waveform. Under nominal operating conditions, the grid voltage during the current pulse is sufficiently positive relative to the cathode potential to form a virtual cathode downstream of the grid. Three-dimensional computer simulations have been performed that use the mesh refinement capability of the WARP particle-in-cell code to examine a small region near the beam center in order to illustrate some of the complexity that can result from such a gridded structure. These simulations have been found to reproduce the hollowed velocity space that is observed experimentally. The simulations also predict a complicated time-dependent response to the waveform applied to the grid during the current turn-on. This complex temporal behavior appears to result directly from the dynamics of the virtual cathode formation and may therefore be representative of the expected behavior in other sources, such as some photoinjectors, that are characterized by a rapid turn-on of the beam current. |
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| TPPE051 | The Optimization of the Electron Injector Resonance System Based on the Evanescent Oscillations | electron, bunching, emittance, space-charge | 3170 | ||
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The report presents the results of the bunching system optimization and electrons motion simulation in the compact S – band injector. The injector consists of the low-voltage diode electron gun and optimized bunching system based on the resonant system with the evanescent oscillations. The amplitude of RF electrical field is increased along the axis of the bunching system. The resonance system optimization allows to obtain electron bunches with the phase length less than 10° (for 70 % particles) at the injector exit.
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| TPPE056 | Emittance Measurement with Upgraded RF Gun System at SPring-8 | emittance, quadrupole, laser, gun | 3348 | ||
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A single cell S-band RFgun has been developed at the SPring-8 since 1996. The minimum normalized beam emittance, measured with double slits' scanning method in 2002, was 2.3 pi mm mrad at the exit of the gun cavity with charge of 0.1 nC/bunch. In 2004, we installed a following accelerator structure to investigate beam behavior of the whole injector system. In this paper, we report emittance measurement results of upgraded system, using variable quadrupole magnet method. The minimum emittance of 2.0 pi mm mrad with a net charge of 0.14 nC/bunch were able to be measured.
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| TPPE059 | New Electron Gun System for BEPCII | gun, electron, emittance, linac | |||
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The new electron gun system for BEPCII has been put into operation since Nov. 2004. The article describes the design, experiment and operation of this new system. The design current of the gun is 10 A for the pulse lengths of 1 ns, 2.5 ns and 1 μs with repetition rate of 50 Hz. The gun is operated with a pulsed high voltage power supply which can provide up to 200 kV high voltage. Computer simulations have been carried out in the design stage, including simulation of the gun geometry and beam transportation. Some important relation curves are obtained during the experiment. Two-bunch operation is available and some elementary tests have been performed. New scheme of the gun control system based on EPICS is also presented. The real operation shows that the design and manufacturing is basically successful.
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| TPPE060 | Simulation Study of a Thermionic RF Gun for High Brightness and Short Pulse Beam | gun, electron, cathode, extraction | 3499 | ||
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Characteristics of thermionic RF guns are not understood completely. In particular, measured intense beam emittances extracted from thermionic RF guns do not agree well with simulated values so far. Most of simulation codes solve the equation of electron motion in an intrinsic mode of the RF field calculated by a separated code. The way of such simulation codes is not self-consistent completely. That is probably a major reason for the discrepancy between the experiments and the simulations. One of the other way for a self-consistent simulation codes is to use an FDTD (Finite Difference Time Domain) method. Since the FDTD method can take into account the microwave propagation including the space charge effect and the beam loading self-consistently, we have developed an FDTD code as 3-D Maxwell's equation solver and applied for a study of beam dynamics in a thermionic RF gun. The main purpose of simulaiton study is to obtain overall properties of the beam dynamics at the time. The goal of this simulation study of the thermionic RF gun is to understand correct characteristics of the thermionic RF gun for producing high brightness and short pulse beam.
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| TPPE064 | Space-Charge Effects Near a Cathode | cathode, electron, space-charge, laser | 3629 | ||
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Funding: This work was supported by the Director, Office of Science of the U.S. DOE under Contract No. DE-AC03-76SF00098. |
RF photocathode guns are excellent sources of high brightness electron bunches. In the limit of high-current short bunches the electron are complicated space-charge fields. To mitigate space charge effect downstream of the gun it is often desirable to produce electorn bunches with uniform distribution. Our goal is to understand to what extent the non-uniformity of the laser pulse intensity is responsible for a non-uniform electron distribution and to what extent this is due to the electron beam dynamics near to the cathode. We investigate these effects with particle-in-cell simulations and simple theory. These studies are focused on the regime where the peak current as well as the temporal current profile are influenced by the self-fields of the bunch. The simulation code XOOPIC has been employed. The critical current limitation for virtual cathode formation and current density profile at the exit of the injector have been found. |
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| TPPE065 | Calculating of Coupling Factor of Microwave Electron Gun | coupling, gun, electron, cathode | 3656 | ||
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To design the coupler of a designing microwave electron gun, we use the "energy method" proposed by Derun Li, et al. The intrinsic Q of the electron gun cavity is very high: about 20000. The method calculates the intrinsic and external Q values of a cavity coupled to a waveguide using MAFIA code in time domain. The comparisons between simulation and experimental results are given for a set of different coupling iris apertures and height. The result shows that "energy method" works efficiently for high Q cavities.
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| TPPE066 | Geometry Optimization of DC/RF Photoelectron Gun | gun, cathode, electron, emittance | 3679 | ||
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Funding: *Work supported by DOE SBIR Grant No. DE-FG02-03ER83878. |
Pre-acceleration of photoelectrons in a pulsed, high voltage, short, dc gap and its subsequent injection into an rf gun is a promising method to improve electron beam emittance in rf accelerators. Simulation work has been performed in order to optimize the geometric shapes of a dc/rf gun and improve electron beam properties. Variations were made on cathode and anode shapes, dc gap distance, and inlet shape of the rf cavity. Simulations showed that significant improvement on the normalized emittance (< 1 mm-mrad), compared to a dc gun with flat cathode, could be obtained after the geometric shapes of the gun were optimized. |
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| TPPP004 | Study of the Beam-Beam Effect for Crab Crossing in KEKB and Super KEKB | luminosity, coupling, damping, radiation | 925 | ||
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Luminosity upgrade using crab cavities is planned at KEK-B factory (KEKB)in 2006. The crab crossing is expected to increase the beam-beam parameter >0.1, which is twice of present value, for KEKB. We discuss torelances of crab cavities and lattice to get the high beam-beam parameter.
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| TPPP006 | Beam-Beam Simulation Study with Parasitic Crossing Effect at KEKB | luminosity, target, damping, beam-beam-effects | 1033 | ||
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KEKB is an asymmetric-energy, two-ring, electron-positron collider for B physics. Two beams collide at one interaction point with a finite crossing angle of 22 mrad. The bunch spacing has chosen to be 4 buckets (8 nsec) in most physics run of KEKB. While the shorter bunch spacing is necessary for a higher luminosity, the degradation of the specific luminosity by unknown reason is observed in 4 or 6 nsec spacing. In order to investigate whether parasitic crossing effect degrades a beam-beam performance, we have performed strong-strong beam-beam simulation with parasitic long-range beam-beam force. In this paper we present and discuss our simulation results.
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| TPPP013 | Simulations of Parametric Resonance Ionization Cooling of Muon Beams | synchrotron, resonance, focusing, lattice | 1321 | ||
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Funding: This work was supported in part by DOE SBIR grants DE-FG02-03ER83722, and 04ER84016. |
The technique of using a parametric resonance to allow better ionization cooling is being developed to create small beams so that high collider luminosity can be achieved with fewer muons. In the linear channel that is studied in this effort, a half integer resonance is induced such that the normal elliptical motion of particles in x-x' phase space becomes hyperbolic, with particles moving to smaller x and larger x' as they pass down the channel. Thin absorbers placed at the focal points of the channel then cool the angular divergence of the beam by the usual ionization cooling mechanism where each absorber is followed by RF cavities. Thus the phase space of the beam is compressed in transverse position by the dynamics of the resonance and its angular divergence is compressed by the ionization cooling mechanism. We report the first results of simulations of this process, including comparisons to theoretical cooling rates and studies of sensitivity to variations in absorber thickness and initial beam conditions. |
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| TPPP017 | Beam-Beam Effects in the Ring-Ring Version of eRHIC | resonance, emittance, beam-beam-effects, luminosity | 1520 | ||
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Funding: The U.S. Department of Energy under Grant No. DE-FG02-04ER41288. |
The eRHIC is a proposed electron ring at the RHIC that will provide collisions between a polarized 5-10 GeV electron beam and an ion beam from one of the RHIC rings. In order to achieve proposed high luminosity, large bunch current and small beta-functions at the IP has to be employed. Such measures result in large beam-beam parameters, 0.029 and 0.08 for the electron beam and 0.0065 and 0.0033 for the proton beam in the horizontal and vertical plane, respectively, in the current ZDR design. The beam-beam effect especially the coherent beam-beam effect is therefore one of important issues to the eRHIC. Moreover, the proposed configuration of unequal circumferences of the electron and proton rings could further enhance the coherent beam-beam effect. The beam-beam effect of eRHIC has therefore been studied with a self-consistent beam-beam simulation by using the particle-in-cell method. Beam-beam limits of the electron and proton beam were examined as thresholds of the onset of coherent beam-beam instability. For the proposed luminosity, the electron and proton bunch currents optimized with the consideration of the beam-beam effect will be discussed. |
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| TPPP024 | Experimental Study of Crossing-Angle and Parasitic-Crossing Effects at the PEP-II e+e- Collider | luminosity, electron, optics, quadrupole | 1874 | ||
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In a series of dedicated accelerator experiments, we have measured the dependence of the PEP-II luminosity performance on small horizontal crossing angles and on the horizontal separation at the first parasitic crossing. The experiment was carried out by varying the IP angle of one of the beams in two different bunch patterns, one with and one without parasitic crossings. The experimental measurements show satisfactory agreement with three-dimensional beam-beam simulations.
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| TPPP028 | Simulation of HOM Leakage in the PEP-II Bellows | vacuum, damping, coupling, higher-order-mode | 2050 | ||
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Funding: Work supported by U.S. DOE contract, DE-AC02-76SF00515. |
An important factor that limits the PEP-II from operating at higher currents is higher-order-mode (HOM) heating of the bellows. One source of HOM heating is the formation of trapped modes at the bellows as a result of geometry variation in the vacuum chamber, for example, the masking near the central vertex chamber. Another source comes from HOMs generated upstream that leak through the gaps between the bellows fingers. Modeling the fine details of the bellows and the surrounding geometry requires the resolution and accuracy only possible with a large number of mesh points on an unstructured grid. We use the parallel finite element eigensolver Omega3P for trapped mode calculations, and the S-matrix solver S3P for transmission analysis. The damping of the HOMs by the use of absorbers inside the bellows will be investigated. |
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| TPPP039 | Geant Simulation of Six-Dimensional Cooling of a Muon Beams in a Ring Coolers | emittance, dipole, focusing, beam-losses | 2580 | ||
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The reduction of the phase-space volume of the beam (cooling) is essential for both muon colliders and neutrino factories. In a muon collider, in particular, the six-dimensional (6D) emittance must be reduced by six orders of magnitude. Cooling the beam in all phase space dimensions can be done through emittance exchange, where the beam loses energy passing through wedge-shaped absorbers in a dispersive magnetic field, designed in a way that fast muons go through more absorber material than slow ones and lose more energy. The longitudinal momentum is then regained using RF cavities. We simulate ring coolers, in which the beam undergoes 6-dimensional cooling through emittance exchange while rotating several times in the ring. The simulation software is a Geant3-based package, specially designed this purpose, with changing electric fields in RF cavities treated correctly. Magnetic fields are read from external maps. Some ring cooler designs and cooling simulation results are presented.
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| TPPP040 | Front-End Design Studies for a Muon Collider | collider, target, proton, dipole | 2610 | ||
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Funding: Work supported by U.S. Department of Energy. |
Using muons instead of electrons is a promising approach to designing a lepton-lepton collider with energies beyond that available at the proposed ILC. At this time a self-consistent design of a high-luminosity muon collider has not been completed. However, a lot of progress has been made in simulating cooling and parts of other systems that could play a role in an eventual collider design. In this paper we look at front-end system designs that begin with a single pion bunch produced from a high power mercury target. We present ICOOL simulation results for phase rotation, charge separation, and pre-cooling of the muon beams. A design is presented for a single-frequency phase rotation system that can transmit 0.47 muons per incident proton on the target. A bent solenoid can be used for high-efficiency separation of the positive and negative muon beams. |
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| TPPP041 | Recent Developments on the Muon-Facility Design Code ICOOL | multipole, emittance, focusing, factory | 2651 | ||
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Funding: Work supported by U.S. Department of Energy. |
Current ideas for designing neutrino factories and muon colliders require unique configurations of fields and materials to prepare the muon beam for acceleration. We have continued the development of the 3D tracking code ICOOL for examining possible system configurations. Development of the ICOOL code began in 1996 in order to simulate the process of ionization cooling. This required tracking in magnetic focusing lattices, together with interactions in shaped materials that must be placed in the beam path.* The most important particle interactions that had to be simulated were energy loss and straggling. Since the optimum way of designing a cooling channel was not known, the code had to have a flexible procedure for specifying field and material geometries. Eventually the early linear cooling channels evolved into cooling rings. In addition the designs require many other novel beam manipulations besides ionization cooling, such as pion collection in a high field solenoid, rf phase rotation, and acceleration in FFAG rings. We describe new features that have been incorporated in ICOOL for handling these new requirements. A suite of auxilliary codes have also been developed for pre-processing, post-processing, and optimization. *R.C. Fernow, ICOOL: a simulation code for ionization cooling of muon beams, Proc. 1999 Part. Accel. Conf., New York, p. 3020. |
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| TPPP048 | A Compact 6D Muon Cooling Ring | emittance, closed-orbit, dipole, lattice | 3025 | ||
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Funding: U.S. Department of Energy. |
We discuss a conceptual design for a compact muon cooling system based on a weak-focusing ring loaded with high-pressure Hydrogen gas. We demonstrate that such a ring will be capable of cooling a circulating muon beam in each of the three spatial dimensions so that 6d cooling of the muon beam phase space is achieved. |
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| TPPP050 | Novel Muon Cooling Channels Using Hydrogen Refrigeration and High Temperature Superconductor | beam-cooling, quadrupole, superconducting-magnet, dipole | 3126 | ||
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Funding: This work was supported in part by DOE STTR grant DE-FG02-04ER86191. |
Ionization cooling, a method for shrinking the size of a muon beam, requires a low Z energy absorber, high-field magnets, and high gradient RF. It is proposed to use one gaseous hydrogen system to provide ionization energy loss for muon beam cooling, breakdown suppression for pressurized high-gradient RF cavities, and refrigeration for superconducting magnets and cold RF cavities. We report progress on the design of a cryostat and refrigeration system that circulates hydrogen through magnetic coils, RF cavities, and the absorber volume to achieve a safe, robust means to enable exceptionally bright muon beams. We find that the design can be greatly simplified if a high temperature superconductor can be used that has the capability to carry adequate current in fields above 10 T at a temperature above 33 K, the critical temperature of hydrogen. |
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| TPPP051 | A Muon Cooling Ring with Curved Lithium Lenses | emittance, scattering, factory, collider | 3167 | ||
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We design a muon cooling ring with curved Lithium lenses for the 6 dimensional muon phase space cooling. The cooling ring can be the final muon phase space cooling ring for a Higgs Factory, a low energy muon collider.Tracking simulation shows promising muon cooling with simplified magneti element models.
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| TPPP052 | Simulations of a Gas-Filled Helical Muon Beam Cooling Channel | emittance, quadrupole, focusing, beam-cooling | 3215 | ||
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Funding: This work was supported in part by DOE STTR/SBIR grants DE-FG02-02ER86145 and 03ER83722. |
A helical cooling channel (HCC) has been proposed to quickly reduce the six-dimensional phase space of muon beams for muon colliders, neutrino factories, and intense muon sources. The HCC is composed of a series of RF cavities filled with dense hydrogen gas that acts as the energy absorber for ionization cooling and suppresses RF breakdown in the cavities. Magnetic solenoidal, helical dipole, and helical quadrupole coils outside of the RF cavities provide the focusing and dispersion needed for the emittance exchange for the beam as it follows a helical equilibrium orbit down the HCC. In the work presented here, two Monte Carlo programs have been developed to simulate a HCC to compare with the analytic predictions and to begin the process of optimizing practical designs that could be built in the near future. We discuss the programs, the comparisons with the analytical theory, and the prospects for a HCC design with the capability to reduce the six-dimensional phase space emittance of a muon beam by a factor of over five orders of magnitude in a linear channel less than 100 meters long. |
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| TPPP055 | Simultaneous Bunching and Precooling Muon Beams with Gas-Filled RF Cavities | target, emittance, factory, collider | 3295 | ||
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Funding: This work was supported in part by DOE SBIR grant DE-FG02-03ER83722. |
High-gradient, pressurized RF cavities are investigated as a means to improve the capture efficiency, to effect phase rotation to reduce momentum spread, and to reduce the angular divergence of a muon beam. Starting close to the pion production target to take advantage of the short incident proton bunch, a series of pressurized RF cavities imbedded in a strong solenoidal field is used to capture, cool, and bunch the muon beam. We discuss the anticipated improvements from this approach to the first stage of a muon cooling channel as well as the requirements of the RF cavities needed to provide high gradients while operating in intense magnetic and radiation fields. |
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| TPPT004 | A 175 MHz RFQ Design for IFMIF Project | rfq, insertion, linac, quadrupole | 904 | ||
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International Fusion Materials Irradiation Facility (IFMIF) is an accelerator-based neutron irradiation facility employing the D-Li stripping reaction, to produce the neutron field similar to the D-T Fusion reactor (2MW/m2,20 dpa/year for Fe). The required beam current of 250 mA is realized by two beam lines of 125mA, and the output energies at injector,RFQ and DTL were designed to be 0.1, 5 and 40 MeV,respectively. The operation frequency of 175MHz was selected to accelerate the large current of 125mA. After an intensive beam simulation, the RFQ with a total length of 12m was designed to keep the minimum emittance growth with the RF injection power of 2.3MW CW. For such a 175MHz RFQ, a design for RF input coupler with loop antenna and co-axial window, supplying RF power shared by 3 x 4 ports, was conducted by using the 3-D electromagnetic code of MW-Studio. In order to withstand the voltage exceeding 200kW CW per one loop antenna, the co-axial line of 4 1/16” diameter is necessary, and it is found that the electric field distortion factor less than 1% can be achieved in beam bore only by employing the 4-loop antenna configuration providing the same power for each quadrants.
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| TPPT006 | Development of RF Input Coupler with a Coaxial Line TiN-Coated Against Multipactoring | vacuum, electron, coupling, linac | 1006 | ||
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In one of the normal-conducting RF cavities used in the KEKB operation, we observed an unexpected rise of the vacuum pressure at certain input-power levels with and without a beam current. From the simulation study, we identify the pressure rises as an effect of the multipactoring discharge in the coaxial line of the input coupler. According to the simulation results, we have decided to make TiN coating on the inner surface of the outer conductor to suppress the multipactoring. In this paper, the status of the development of the TiN-coated input coupler is reported including the recent results of the high-power tests.
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| TPPT015 | Coupler Matching Techniques for C-Band Accelerating Section | target, linac, resonance, coupling | 1431 | ||
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Research and development of the c-band accelerating section has proceeded since 2002. This paper reports the development of the second prototype accelerating section. The coupler iris with a 4 mm thick is thicker than the first prototype because of preventing the rf breakdown at the iris edge. The coupler has a single port and the coupler cell is the same length as the waveguide(WR-187). The coupler cavity diameter and the coupling iris were optimized by using the iteration of the rf measurement which is the nordal shift method.
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| TPPT018 | Tuning of 20MeV PEFP DTL | target, proton, insertion, klystron | 1598 | ||
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Funding: This work is supported by the 21C Frontier R&D program in the Ministry of Science and Technology of the Korean government. |
The PEFP (Proton Engineering Frontier Project) 20 MeV DTL have been constructing in KAERI site. The tuning goals for PEFP DTL are achieving the tank frequency as ± 5 kHz of designed resonant frequency and 1% of field profile through a tank. To tune the tank frequency 8 low power slug tuners per tank are fabricated and the tuning range is ±125 kHz per a tuner. Post couplers with tap to stabilize the field against the perturbation also are fabricated and will be installed every 3rd (1st tank) and 2nd (2,3,4th tank) drift tubes. We set up the bead perturbation measurement equipment as measuring the phase shift of a tank using network analyzer and LabView program. We are finalizing the tuning procedures and also the data calculation program. In this presentation we will show the overall features of the PEFP DTL tuning and discuss the measurement results. |
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| TPPT019 | Numerical Study of Coupling Slot Effects on Beam Dynamics in Industrial Accelerator Prototype | coupling, quadrupole, electron, injection | 1622 | ||
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Funding: The work is supported by ISTC grant #2550. |
At Budker INP, the work is in progress on development of high-efficiency, high-power electron accelerator named ILU-12. The accelerator has a modular structure and consists of a chain of accelerating cavities connected by on-axis coupling cavities with coupling slots in the common walls (the coupling constant is about 0.08). Main parameters of the accelerator are: operating frequency of 176 MHz, electron energy of up to 5 MeV, average beam power of 300 kW. The paper presents results of 3D electromagnetic field numerical simulations for ILU-12 accelerating structure with recovery of quadrupole filed disturbance because of large coupling holes. The results show that accelerating cell geometry chosen eliminates coupling slot influence on the beam dynamics. |
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| TPPT028 | Design of a New Main Injector Cavity for the Fermilab Proton Driver Era | proton, coupling, acceleration, impedance | 2015 | ||
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Funding: Operated by Universities Research Association, Inc. for the U.S. Department of Energy under contract DE-AC02-76CH03000. |
In the design report of the Fermilab Proton Driver [1],* the Main Injector (MI) needs to be upgraded to a 2 MW machine. For the Main Injector radiofrequency (rf) upgrade, R&D efforts are launched to design and build a new rf system. This paper presents the new cavity design study for the rf system. The cavity is simulated with the design code Mafia [2].** **Proton Driver Study II, FERMILAB-TM-2169, May 2002, edited by G.W. Foster, W. Chou and E. Malamud. **Computer Simulation Technology, MAFIA 4, December 1996. |
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| TPPT033 | Simulations Using the VORPAL Code of Electron Impact Ionization Effects in Waveguide Breakdown Processes | electron, ion, plasma, space-charge | 2298 | ||
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Funding: Supported by Department of Energy SBIR Grant No. DE-FG03-02ER83554. |
We present results of three-dimensional simulations using the VORPAL code of power absorbtion by stray electrons in X-band waveguides. These simulations include field emission from the waveguide surfaces, impact ionization of background gas, and secondary emission from the walls. We discuss the algorithms used for each of these electron effects. We show the power abosrbed as a function of background gas density. Finally, we present scaling results for running these simulations on Linux Clusters. |
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| TPPT036 | Higher-Order-Mode Damper Testing and Installation in the Advanced Photon Source 352-MHz Single-Cell RF Cavities | storage-ring, vacuum, photon, insertion | 2443 | ||
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Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. |
Higher-order-mode dampers were recently installed in the storage ring rf cavities at the Advanced Photon Source to eliminate longitudinal coupled-bunch instability. It was discovered that the 540-MHz cavity dipole mode created beam instability at beam currents in excess of 85 mA causing horizontal emittance blowup. Methods of compensating for the instability by detuning the cavities and adjusting the cavity water temperature were becoming more difficult at higher beam currents as tests were performed to prepare for eventual 300-mA beam current operation. Electric field passive dampers located on the median plane of each cavity were determined to be the most promising solution. Simulation models were created and verified with low-power testing of the dampers. High-power testing of the dampers as well as conditioning of the damper ceramic load were also performed at the APS 352-MHz rf test stand and compared with simulation results. Preliminary test results will be discussed. |
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| TPPT038 | Development of C-Band Accelerator Structure with Smooth Shape Couplers | target, linac, positron, acceleration | 2530 | ||
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The first C-band accelerator structure for the SuperKEKB injector linac has been operated in the beam line of e+/e- injector linac for KEKB/PF/PF-AR since September, 2003. A new accelerator structure will locate upstream of the first structure. The upstream structure is exposed to higher RF field than that of downstream structure. For the case of first structure, most of an RF breakdown occurs in an input coupler. In order to reduce a frequency of the breakdown, improvement of a coupler is required. In order to suppress a thermionic emission around the coupler iris, thick and smooth iris is adopted for the upstream structure. The development status of this type of upstream structure is described.
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| TPPT040 | X-Band Dipole Mode Deflecting Cavity for the UCLA Neptune Beamline | diagnostics, resonance, dipole, vacuum | 2627 | ||
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Funding: This work was funded by the Department of Energy under Grant No. DE-FG03-92ER40693. |
We report progress on the design and construction of a nine-cell dipole (TM 110 mode) cavity for use as a temporal diagnostic of the 14 MeV 300 pC electron bunches generated at the UCLA Neptune Laboratory linear accelerator, with an anticipated temporal resolution of 150 fs at a peak input power of 50 kW. The cavity is a center-fed standing-wave pi-mode structure, operating at 9.6 GHz, and incorporating a knife-edge and gasket assembly which minimizes the need for brazing or welding. Results of initial RF tests are discussed and compared with simulation results obtained using the commercial code HFSS. |
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| TPPT042 | The Simulation Calculations and Dielectric Characteristics Investigation of an X-Band Hybrid Dielectric-Iris-Loaded Traveling Accelerating Structure | acceleration, resonance, synchrotron, synchrotron-radiation | 2720 | ||
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Funding: This work is supported by the National Natural Science Foundation of China(No.10375060,10205014)and the Project of Knowledge Innovation Program of the Chinese Academy of Sciences. |
Mafia code has been used to calculate the RF properties versus the geometric parameters and dielectric permittivity for the X-band (f=9.37GHz) hybrid dielectric-iris-loaded traveling accelerating structure. The simulation results show that when the range of the permittivity is about 5-9, the new structure may have lower ratio (about 1) of peak surface electric field at the iris to axial accelerating electric field by optimizing the geometric parameters, while r, Q, r/Q of the new structure being comparable to iris-loaded accelerating structure. The experimental investigations of the permittivity of the ceramics have been made at the X-band by using the cavity perturbation technique. The measured results are in good agreement with the simulation results of Microwave Studio. Furthermore, the stability of the ceramics is examined. A number of experimental results show that the certain ceramic with permittivity of 5.78 is applied to the design of the new accelerating structure. |
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| TPPT043 | The Studies of Hybrid Dielectric-Iris-Loaded Accelerating Structure | acceleration, synchrotron, synchrotron-radiation, impedance | 2747 | ||
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Funding: This work is supported by the National Natural Science Foundation of China(No.10375060,10205014) and the Project of Knowledge Innovation Program of the Chinese Academy of Sciences. |
The dispersion property and the propagation characteristics of the accelerating mode (TM01 mode) and higher-order-modes about a new hybrid dielectric-iris-loaded accelerating structure have been analysed and discussed by the field matching method. Mafia code has been used to calculate the RF properties versus the geometric parameters and dielectric permittivity for the X-band (f=9.37GHz) hybrid dielectric-iris-loaded traveling accelerating structure. Some model cavities have been developed, and experimental investigations have been carried on. The above results will provided some beneficial datum for the design and manufacture of X-band hybrid dielectric-iris-loaded traveling-wave accelerating structure. |
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| TPPT053 | Low-Beta SC Quarter-Wave Resonator and Cryomodule for SPIRAL 2 | linac, alignment, vacuum, injection | 3238 | ||
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In the framework of the SPIRAL 2 project to be built in GANIL, we studied a complete cryomodule for the low beta (0.07) superconducting linac. The 88 MHz quarter wave resonators were optimised for RF, mechanical and thermal considerations. A prototype resonator, which differs from the final resonator by the Helium tank and the removable end-plate geometry and material, has been built. We present the equipments developped for the preparation of this prototype as well as the results of the RF tests. We also detail the mechanical calculation and measurements of the tuning system, and the main aspects of the cryomodule designed to save longitudinal space.
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| TPPT054 | CW Operation of the TTF-III Input Coupler | vacuum, klystron, linac, beam-loading | 3292 | ||
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Many newly proposed light sources, operating in the CW regime, are based on superconducting TESLA technology. Since this was originally developed for pulsed, 1-% duty-factor operation, it is important to determine the limitations of the TESLA cryomodule and its components when operated CW. Among the critical components is the RF input coupler. Two tests have been performed to determine the average power limit of the TTF-III system. First, room temperature tests up to 4 kW were performed at the Forschungszentrum Rossendorf. These permitted the calibration of computer codes developed to calculate the temperature distribution in the coupler. The programs then were used to make predictions for the (normal) cold operation of the coupler. At BESSY, the coupler test stand was assembled inside the HoBiCaT horizontal cryostat test facility to operate the coupler in an environment close to that of a real accelerator. The results of the two tests are presented here.
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| TPPT058 | First Tests of the Superconducting CH-Structure | pick-up, resonance, coupling, proton | 3414 | ||
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Funding: GSI, BMBF contr. No. 06F134I, EU contr. No. EFDA/99-507ERB5005, CT990061 and RII3-CT-2003-506395. |
The Crossbar-H-type CH-structure is a new H-mode drift tube-structure operating in the H11-mode. Due to its mechanical rigidity room temperature as well as superconducting cavities can be realized. The superconducting CH-structure has been developed at the IAP in Frankfurt, Germany. To prove the promising results obtained by simulations a 19-cell, 352 MHz (beta=0.1) prototype cavity has been designed and built. This is the first superconducting low energy multi-cell cavity. We present the first cold tests of the cavity which have been performed in the cryogenic laboratory in Frankfurt. |
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| TPPT063 | Higher-Order-Mode Damping of L-Band Superconducting Cavity using a Radial-Line HOM Damper | damping, linac, dipole, quadrupole | 3606 | ||
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For the energy recovery linacs, strong damping of higher-order-modes (HOMs) is indispensable to avoid beam breakup instabilities. We studied a new HOM damping scheme using a radial-line HOM damper with a choke structure. Both models of the radial-line damper and the TESLA-type 9-cell cavity were prepared and the HOM characteristics of this scheme were experimentally investigated. Measurement results showed a promising performance of the radial-line HOM damper.
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| TPPT067 | High Power Coupler Studies for the ERLP | vacuum, coupling, linac, booster | 3736 | ||
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Funding: ASTeC, CCLRC Daresbury Laboratory. |
Two Superconducting RF modules of the ELBE type have been ordered from Accel Instruments GmbH for use on the Energy Recovery Linac Prototype (ERLP) being built at Daresbury Laboratory. One structure is to be used as a booster module, with an energy gain of 8 MeV, and the other is to act as an energy recovery linac operating at electron beam energy of up to 35 MeV. High power couplers capable of handling up to 10 kW CW are required to provide successful operation of the ERLP. Once received from Accel four couplers including RF windows will be conditioned and tested at FZR Dresden; this paper describes the test procedure anticipated. |
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| TPPT070 | Development of the Superconducting 3.9 GHz Accelerating Cavity at Fermilab | higher-order-mode, damping, vacuum, resonance | 3825 | ||
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Funding: U.S. Department of Energy. |
A superconducting third harmonic accelerating cavity (3.9 GHz) was proposed to improve beam quality in the TTF-like photoinjector. Fermilab has developed, built and tested several prototypes, including two copper 9-cell cavities, and niobium 3-cell and 9-cell cavities. The helium vessel and frequency tuner for the 9-cell cavity was built and tested as well. In cold tests, we achieved a peak surface magnetic field of ~120mT, well above the 70mT specification. The accelerating gradient was limited by thermal breakdown. Studies of the higher order modes in the cavity revealed that the existing cavity design with two HOM couplers will provide sufficient damping of these modes. In this paper we discuss the cavity design, results of the studies and plans for further development. |
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| TPPT074 | Simulation Study of Electronic Damping of Microphonic Vibrations in Superconducting Cavities | feedback, damping, coupling, resonance | 3916 | ||
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Funding: This work was supported by the Department of Energy under contract DE-AC05-84ER-40150. |
Electronic damping of microphonic vibrations in superconducting rf cavities involves an active modulation of the cavity field amplitude in order to induce ponderomotive forces that counteract the effect of ambient vibrations on the cavity frequency. In lightly beam loaded cavities, a reduction of the microphonics-induced frequency excursions leads directly to a reduction of the rf power required for phase and amplitude stabilization. Jefferson Lab is investigating such an electronic damping scheme that could be applied to the JLab 12 GeV upgrade, the RIA driver, and possibly to energy-recovering superconducting linacs. This paper discusses a model and presents simulation results for electronic damping of microphonic vibrations. |
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| TPPT081 | Fabrication and Testing of the SRF Cavities for the CEBAF 12 GeV Upgrade Prototype Cryomodule Renascence | damping, coupling, dipole, impedance | 4081 | ||
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Funding: This manuscript has been authorized by SURA, Inc. under Contract No. DE-AC05-84ER-40150 with the U.S. Department of Energy. |
Twelve seven-cell niobium cavities for the CEBAF 12 GeV upgrade prototype cryomodule Renascence have been fabricated at JLab and tested individually. This set includes four of the "Low Loss" (LL) design and eight of the "High Gradient" (HG) design. The fabrication strategy was an efficient mix of batch job-shop component machining and in-house EBW, chemistry, and final-step machining to meet mechanical tolerances. Process highlights will be presented. The cavities have been tested at 2.07 K, the intended CEBAF operating temperature. Performance exceeded the tentative design requirement of 19.2 MV/m cw with less than 31 W dynamic heat dissipation. These results, as well as the HOM damping performance will be presented. |
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| TPPT082 | High Thermal Conductivity Cryogenic RF Feedthroughs for Higher Order Mode Couplers | damping, pick-up, higher-order-mode, SNS | 4108 | ||
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Funding: This manuscript has been authorized by SURA, Inc. under Contract No. DE-AC05-84ER-40150 with the U.S. Department of Energy. |
The use of higher-order-mode (HOM) pickup probes in the presence of significant fundamental rf fields can present a thermal challenge for cw or high average power SRF cavity applications. The electric field probes on the HOM-damping couplers on the JLab "High Gradient" and "Low Loss" seven-cell cavities for the CEBAF upgrade are exposed to approximately 10% of the peak magnetic field in the cavity. To avoid significant dissipative losses, these probes must remain superconducting during operation. Typical cryogenic rf feedthroughs provide a poor thermal conduction path for the probes, and provide inadequate stabilization. We have developed solutions that meet the requirements, providing a direct thermal path from the niobium probe, thorough single-crystal sapphire, to bulk copper which can be thermally stationed (or heat sunk). Designs, electromagnetic and thermal analyses, and performance data will be presented. |
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| TPPT098 | VORPAL as a Tool for Three-Dimensional Simulations of Multipacting in Superconducting RF Cavities | electron, plasma, radio-frequency, resonance | 4332 | ||
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Considerable resources are required to run three dimensional simulations of multipacting in superconducting rf cavities. Three dimensional simulations are needed to understand the possible roles of non-axisymmetric features such as the power couplers. Such simulations require the ability to run in parallel. We consider the versatile plasma simulation code VORPAL* as a possible platform to study such effects. VORPAL has a general 3D domain decomposition and can run in any physical dimension. VORPAL uses the CMEE library** to model the secondary emission of electrons from metal surfaces. We will present a three dimensional simulation of a simple pillbox rf cavity to demonstrate the potential of VORPAL to be a major simulation tool for superconducting rf cavities.
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*C. Nieter and J.R. Cary, J. Comp. Phys. 196 (2004), p. 448. **P.H. Stoltz, ICFA electron cloud work shop, Napa, CA (2004). |
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| TOPA001 | Mono Energetic Beams from Laser Plasma Interactions | laser, electron, plasma, injection | 69 | ||
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Funding: Supported by U.S. Dept. of Energy contracts DE-AC03-76SF00098, DE-FG03-95ER40926, DE-FG02-01ER41178, DE-FG02-03ER83857, SciDAC, and NSF 0113907. C. Geddes is also supported by the Hertz foundation. |
A laser driven wakefield accelerator has been tuned to produce high energy electron bunches with low emittance and energy spread by extending the interaction length using a plasma channel. Wakefield accelerators support gradients thousands of times those achievable in RF accelerators, but short acceleration distance, limited by diffraction, has resulted in low energy beams with 100% electron energy spread. In the present experiments on the L’OASIS laser,* the relativistically intense drive pulse was guided over 10 diffraction ranges by a plasma channel. At a drive pulse power of 9 TW, electrons were trapped from the plasma and beams of percent energy spread containing >200pC charge above 80 MeV and with normalized emittance estimated at < 2 pi -mm-mrad were produced.** Data and simulations (VORPAL***) show the high quality bunch was formed when beam loading turned off injection after initial trapping, and when the particles were extracted as they dephased from the wake. Up to 4TW was guided without trapping, potentially providing a platform for controlled injection. The plasma channel technique forms the basis of a new class of accelerators, with high gradients and high beam quality. *W.P. Leemans et al., Phys. Plasmas 5, 1615-23 (1998). **C.G.R. Geddes et al., Nature 431, 538-41 (2004). ***C. Nieter et al., J. Comp. Phys. 196, 448-73 (2004). |
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| TOPA006 | High Energy Gain IFEL at UCLA Neptune Laboratory | laser, undulator, electron, acceleration | 500 | ||
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We report the observation of energy gain in excess of 20 MeV at the Inverse Free Electron Laser Accelerator experiment at the Neptune Laboratory at UCLA. A 14.5 MeV electron beam is injected in an undulator strongly tapered in period and field amplitude. The IFEL driver is a CO2 10.6 mkm laser with power larger than 400 GW. The Rayleigh range of the laser, ~ 1.8 cm, is much shorter than the undulator length so that the interaction is diffraction dominated. A few per cent of the injected particles are trapped in a stable accelerating bucket. Electrons with energies up to 35 MeV are measured by a magnetic spectrometer. Simulations, in good agreement with the experimental data, show that most of the energy gain occurs in the first half of the undulator at a gradient of 70 MeV/m and that the structure in the measured energy spectrum arises because of higher harmonic IFEL interaction in the second half of the undulator.
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| TOPA010 | Photonic Crystal Laser-Driven Accelerator Structures | lattice, focusing, laser, dynamic-aperture | 731 | ||
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Funding: Work supported by Department of Energy contract DE-AC03-76SF00515 (SLAC). |
We discuss simulated photonic crystal structure designs, including two- and three-dimensional planar structures and fibers. The discussion of 2D structures demonstrates guiding of a speed-of-light accelerating mode by a defect in a photonic crystal lattice and reveals design considerations and trade-offs. With a three-dimensional lattice, we introduce a candidate geometry and discuss beam dynamics, coupling, and manufacturing techniques for that structure. In addition we discuss W-band scale tests of photonic crystal structures. The computational methods are also discussed. |
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| WPAE008 | Redesign of a Low Energy Probe Head | emittance, proton, injection, cyclotron | 1105 | ||
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The present situation of the low energy probe L·102 in TRIUMF cyctron is that the thickness of finger 5 is uniform in the radial direction and its weight which amounts to ~447 g is affecting its re-circulating ball mechanism and causing it to fall below the median plane over its range of movement (13.890 to 161.515 inch). We first made simulations to determine the optimum thickness of the probe head vs the radial length so as to reduce its weight. And then, we compared the simulation results with experimental measurements made. Finally, we calculated the temperature rise caused by the beam power dumped on the probe, and figured out the maximum beam current that can be dumped on the finger.
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| WPAE010 | Neutron Flux and Activation Calculations for a High Current Deuteron Accelerator | ion, vacuum, target, ion-source | 1192 | ||
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Neutron analysis of the first Neutral Beam (NB) for the International Thermonuclear Experimental Reactor (ITER) was performed to provide the basis for the study of the following main aspects: personnel safety during normal operation and maintenance, radiation shielding design, transportability of the NB components in the European countries. The first ITER NB is a medium energy light particle accelerator. In the scenario considered for the calculation the accelerated particles are negative deuterium ions with maximum energy of 1 MeV. The average beam current is 13.3 A. To assess neutron transport in the ITER NB structure a mathematical model of the components geometry was implemented into MCNP computer code (MCNP version 4c2. "Monte Carlo N-Particle Transport Code System." RSICC Computer Code Collection. June 2001). The neutron source definition was outlined considering both D-D and D-T neutron production. FISPACT code (R.A. Forrest, FISPACT-2003. EURATOM/UKAEA Fusion, December 2002) was used to assess neutron activation in the material of the system components. Radioactive inventory and contact dose rate were assessed considering the potential operative scenarios.
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| WPAE014 | Conceptual Design of a Longitudinal Halo Collimator for J-PARC Linac | linac, collimation, emittance, optics | 1413 | ||
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In a high-intensity proton accelerator, avoidance of excess beam loss is essentially important to enable hands-on maintenance. To reduce the uncontrolled beam loss in the following ring, we plan to install a longitudinal halo collimator system in a beam transport line after the injector linac. The collimator system is supposed to have two main roles: One is the elimination of longitudinal tail or halo particles destined to be lost in the following ring, and the other is the removal of anomalous beams which can be resulted from, for example, RF discharge of an accelerating cavity. We plan to adopt a "periodic collimation scheme" in the collimator system taking advantage of the three-fold symmetry of the arc section. The momentum aperture of the collimator system is expected to be reduced by the factor of two adopting periodic collimation. In this paper, conceptual design of the collimator system is presented together with the results of particle simulations.
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| WPAE018 | Performance Tests of Survey Instruments Used in Radiation Fields Around High-Energy Accelerators | radiation, shielding, photon, target | 1595 | ||
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Measurements of ambient dose equivalent in stray radiation fields behind the shielding of high-energy accelerators are a challenging task. Several radiation components (photons, neutrons, charged particles), spanning a wide range of energies, contribute to the total dose equivalent. In routine-measurements, the total dose equivalent is obtained by the combination of several radiation detectors. Ionisation chambers, which are sensitive to all radiation components, are employed together with so-called REM counters, which are responding mainly to neutrons. The total dose equivalent is correctly assessed provided that the response is interpreted carefully by using appropriate corrections and calibration factors. For this reason measurements were carried out in a high-energy reference field at CERN, which allows one to study the response of the different detectors in a mixed radiation field under controlled conditions. In addition, the field was simulated by Monte Carlo simulations. The outcome of these studies serves on one hand as a basis for quality assurance and improves on the other hand the knowledge of the instrument’s response for future applications at the LHC.
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| WPAE020 | A Large Diameter Entrance Window for the LHC Beam Dump Line | vacuum, proton, shielding, dumping | 1698 | ||
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The graphite LHC beam dump block TDE has to absorb the full LHC beam intensity at 7 TeV. The TDE vessel will be filled with inert gas at atmospheric pressure, and requires a large diameter entrance window for vacuum separation from the beam dumping transfer line. The swept LHC beam must traverse this window without damage for regular operation of the beam dump dilution system. For dilution failures, the entrance window must survive most of the accident cases, and must not fail catastrophically in the event of damage. The conceptual design of the entrance window is presented, together with the load conditions and performance criteria. The FLUKA energy deposition simulations and ANSYS stress calculations are described, and the results discussed.
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| WPAE030 | Thermal Analysis of the Al Window for a New CESR-c Luminosity Monitor | photon, luminosity, positron, vacuum | 2137 | ||
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Funding: Work supported by the U.S. National Science Foundation. |
A luminosity monitor using photons from radiative bhabha events at the CLEO interaction point (IP) has been installed in the Cornell Electron Storage Ring (CESR). A key vacuum and detector component is the photon window/converter whose uniformity and thickness are critical for determining the resolution of the total energy deposited in the segmented luminosity monitor. The window design must accommodate the operational requirements of the new monitor at CLEO-c beam energies of 1.5-2.5 GeV and also provide sufficient safety margin for operation at 5.3 GeV beam energies for Cornell High Energy Synchrotron Source (CHESS) running. During 5.3 GeV operation, intense stripes of synchrotron radiation from the interaction region superconducting quadrupole magnets as well as nearby bending magnets strike the window. During the course of window development, several materials and designs were evaluated. Thermal stresses were calculated using the finite element code ANSYS for various beam conditions to guide the cooling design. A window using aluminum alloy (6061-T6) was ultimately chosen to provide optimal performance for both CLEO-c and CHESS running conditions. The window has been in successful operation since September 2004. |
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| WPAE038 | Resonance Control Cooling System Performance and Developments | resonance, SNS, linac, Spallation-Neutron-Source | 2541 | ||
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge. |
The Spallation Neutron Source (SNS) is an accelerator-based neutron source being built at Oak Ridge National Laboratory. The warm linac portion, designed by Los Alamos, has been installed and commissioned. The warm linac is comprised of six Drift Tube Linac (DTL) tanks and four Coupled Cavity Linac (CCL) modules. For commissioning purposes the accelerating systems have been operated at less than the design 6% duty factor. During lower power operation there is less RF cavity heating. This decrease in heat load causes operational stability issues for the associated Resonance Control Cooling Systems (RCCSs) which were designed for full duty factor operation. To understand this effect operational results have been analyzed and tests have been performed. External system factors have been explored and the resulting impacts defined. Dynamic modeling of the systems has been done via a collaboration with the Institute for Nuclear Research (INR), Moscow, Russia. New RCCS operation code has been implemented. Increases in system performance achieved and solutions employed will be presented. |
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| WPAE040 | Comparison of Techniques for Longitudinal Tuning of the SNS Drift Tube Linac | linac, SNS, Spallation-Neutron-Source, target | 2616 | ||
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge. |
It is important to bring the cavity field amplitude and phase to the design values for a high intensity linac such as the Spallation Neutron Source (SNS)linac. A few techniques are available, such as the longitudinal acceptance scan and phase scan. During SNS linac commissioning, tuning of cavities was conducted using the acceptance scan and phase scan technique based on multiparticle simulations. The two techniques are compared. |
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| WPAE050 | First Calibrations of Alanine and Radio-Photo-Luminescence Dosemeters to a Hadronic Radiation Environment | proton, radiation, photon, hadron | 3097 | ||
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Alanine and Radio-Photo-Luminescence (RPL) dosimeters are used to monitor radiation doses occurring inside the tunnels of all CERN accelerators including the Large Hadron Collider (LHC). They are placed close to radiation sensitive machine components like cables or insulation of magnet coils to predict their remaining lifetime. The dosimeters are exposed to mixed high-energy radiation fields. However, up to now both dosimeter types are calibrated to 60Co-photons only. In order to study the response of RPL and alanine dosimeters to mixed particle fields like those occurring at CERN’s accelerators, an irradiation campaign at the CERN-EC High-Energy Reference field Facility (CERF-field) was performed. Moreover, the dosimeters were first time calibrated to a proton radiation field of a constant momentum of 24 GeV/c. In addition to the experiment FLUKA Monte Carlo simulations were carried out, which provide information concerning the energy deposition and the radiation field at the dosimeter locations.
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| WPAE054 | Irradiation Effects on RIA Fragmentation Cu Beam Dump | ion, heavy-ion, radiation, target | 3265 | ||
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Funding: U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. |
Within the scope of conceptual R&D activities in support of the Rare-Isotope Accelerator (RIA) facility, high priority is given to the development of high-power fragmentation beam dumps. A pre-study was made of a static water-cooled Cu beam dump that can meet requirements for a 400 MeV/u uranium beam. The issue of beam sputtering was addressed and found to be not a significant issue. Preliminary radiation transport simulations show significant damage (dpa) in the vicinity of the Bragg peak of uranium ions. Experimental data show that defects in Cu following neutron or high-energy particle irradiation tend to saturate at doses between 1 and 5 dpa, and this saturation in defect density also results in saturation of mechanical property degradation. However, effects of swift heavy ion irradiation and the production of gaseous and solid transmutant elements still need to be addressed. Initial calculations indicate that He concentrations on the order of 100 appm are produced in the beam dump after several weeks of continuous operation and He embrittlement should be a concern. Recommendations are made for further investigation of Cu irradiation effects RIA-relevant conditions. |
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| WPAE056 | Geant4-Based Simulation Study of PEP-II Beam Backgrounds in the BaBar Detector at the SLAC B-Factory | vacuum, luminosity, scattering, background | 3351 | ||
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To improve the understanding of accelerator-induced backgrounds at the SLAC B-Factory and validate the proposed PEP-II luminosity upgrade, we simulate lost-particle backgrounds in the BaBar detector originating from beam-gas interactions and radiative-Bhabha scatters. To perform this study, we have extended the GEANT4-based BaBar detector simulation to include PEP-II beam-line components and magnetic fields up to 10m away from the interaction point. We first describe the simulation model and then compare predicted background levels with measurements from dedicated single-and colliding-beam experiments. Finally, we compare the simulated background levels in the current and the proposed luminosity-upgrade configurations.
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| WPAE058 | High Voltage Measurements on Nine PFNs for the LHC Injection Kicker Systems | kicker, injection, collider, power-supply | 3402 | ||
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Funding: National Research Council of Canada |
Each of the two LHC injection kicker magnet systems must produce a kick of 1.3 T.m with a flattop duration variable up to 7.86 microseconds, and rise and fall times of less than 900 ns and 3 microseconds, respectively. A kicker magnet system consists of four 5 Ohm transmission line magnets with matching terminating resistors, four 5 Ohm Pulse Forming Networks (PFN) and two Resonant Charging Power Supplies (RCPS). Nine PFNs, together with associated switch tanks, and dump switch terminating resistors have been built at TRIUMF and all have been tested at high voltage (54 kV) to ensure that the performance is within specification. This paper describes the HV measurements, compares these results with low voltage measurements and analyses the pulse performance of the PFNs. The measurements are compared with results from PSpice simulations and small discrepancies between the predictions and measurements are explained. |
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| WPAE060 | Programmable Power Supply for AC Switching Magnet of Proton Accelerator | power-supply, proton, extraction, linac | 3508 | ||
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Funding: Ministry of Science and Technology. |
The 100-MeV PEFP proton linac has two proton beam extraction lines for user’ experiment. Each extraction line has 5 beamlines and has 5 Hz operating frequency. An AC switching magnet is used to distribute the proton beam to the 5 beamlines, An AC switching magnet is powered by PWM-controlled bipolar switching-mode converters. This converter is designed to operate at ±350A, 5 Hz programmable step output. The power supply is employed IGBT module and has controlled by a DSP (Digital Signal Process). This paper describes the design and test results of the power supply. |
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| WPAE061 | LC Filter for High Accuracy and Stability Digital MPS at PLS | power-supply, feedback, damping, alignment | 3550 | ||
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Funding: Work supported by the Ministry of Science and Technology, Korea. |
High accuracy and stability digital power supply for magnet is developed at PLS. This power supply has three sections. The first section is digital controller including DSP&FPGA and precision ADC, the second consists of IGBT driver and four quad IGBT switch, and the third is LC output section. AC input voltage of power supply is 3-phase 21V, output current is 0 ~ 150 A dc. Switching frequency of IGBT is 25 kHz. The output current of power supply has very high accuracy of 100 mA step resolution at full range and the stability of ± 1.5 ppm for short term and ± 5 ppm for long term. This paper describes characteristics of filter and output current performance improvement after LC output filter at four quad digital power supplies. |
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| WPAP004 | Dark Current and Multipacting in the Photocathode RF Guns at PITZ | cathode, electron, gun, laser | 895 | ||
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For photocathode rf guns, the amount of dark current depends on the cavity surface and the photocathodes. Smooth conditioning reduces the amount of dark current. Mechanical damages of the cathodes induce high dark current and chemical pollution changes emission properties of the cathode. Multipacting in the gun cavity changes the surface status of the cathodes and sometimes makes the gun operation impossible due to vacuum interlocks. In this paper, dark current and multipacting features of the rf gun are presented including experimental and simulation studies.
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| WPAP008 | Simulation for a New Polarized Electron Injector (SPIN) for the S-DALINAC | electron, gun, cathode, vacuum | 1117 | ||
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Funding: Work supported in part by DFG under contract SFB 634 and DESY, Hamburg. |
The Superconducting DArmstädter LINear ACcelerator (S-DALINAC) is a 130 MeV recirculating electron accelerator serving several nuclear and radiation physics experiments. For future tasks, the 250 keV thermal electron source should be completed by a 100 keV polarized electron source. Therefore a new low energy injection concept for the S-DALINAC has to be designed. The main components of the injector are a polarized electron source, an alpha magnet, a Wien filter spin-rotator and a Mott polarimeter. In this paper we report over the first simulation and design results. For our simulations we used the TS2 and TS3 modules of the CST MAFIA (TM) programme which are PIC codes for two and three dimensions and the CST PARTICLE STUDIO (TM). |
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| WPAP009 | Optimization of RF Compressor in the SPARX Injector | emittance, brightness, gun, bunching | 1144 | ||
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The SPARX photoinjector consists in a rf gun injecting into three SLAC accelerating sections, the first one operating in the RF compressor configuration in order to achieve higher peak current. A systematic study based on PARMELA simulations has been done in order to optimize the parameters that influence the compression also in view of the application of this system as injector of the so called SPARXINO 3-5 nm FEL test facility. The results of computations show that peak currents at the injector exit up to kA level are achievable with a good control of the transverse and longitudinal emittance by means of a short SW section operating at 11424 MHz placed before the first accelerating section. Some working points in different compression regimes suitable for FEL experiments have been selected. The stability of these points and the sensitivity to various types of random errors are discussed.
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| WPAP011 | SPARC Working Point Optimization for a Bunch with Gaussian Temporal Profile | emittance, radiation, electron, undulator | 1248 | ||
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We present the optimization of the working point for the SPARC photoinjector with a Gaussian temporal profile. The implications of a Gaussian temporal profile are discussed here for the standard working conditions and for the RF compressor case in comparison with the nominal working point performances of a 10ps flat top pulse with rise time of 1ps. Comparisons with the upgraded version of the HOMDYN code including arbitrary bunch temporal profiles are also reported. Advantages and drawbacks of the Gaussian and flat top pulse shapes are discussed. For the standard working point, it is shown that the two cases provide the same saturation length and average power, but the higher current in the beam core of the Gaussian pulse gives a higher peak radiation power. As the laser pulse shape could be Gaussian at the first stage of the SPARC operation, it is clear the importance of these simulation results.
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| WPAP012 | Preliminary Results on Beam Dynamics of Laser Pulse Shaping Effects in SPARC | emittance, laser, electron, target | 1315 | ||
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In a photoinjector system the role played by the laser pulse shaping in achieving high quality electron beam is crucial, as it determines the distribution dependent space charge effects in the early stages of the acceleration. A dedicated code to simulate pulse shaping in a laser system and able to generate the corresponding initial electron beam distribution has been developed. Realistic deviations from the ideal flat top pulse give for example a ramp or multi-peaks shape with a raletive rise time, plateau deformation and ripples. The beam dynamics of electron beams with different initial temporal pulse characteristics along the SPARC photoinjector has also been studied with the code PARMELA. More exotic pulse shaping are also discussed. The study presented here gives some indications on the tolerances of the laser beam characteristics for the electron beam quality preservation.
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| WPAP035 | Emittance Compensation in Flat Beam Production in an RF Gun Linac | emittance, space-charge, electron, gun | 2399 | ||
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Funding: This research is supported by the U.S. Department of Energy under contract DE-FG02-92ER40747 and the National Science Foundation under contract NSF PHY-0244793. |
Ya. Derbenev Proposed a flat beam production method in RF gun Linac, which passes the electron beam through a matched skew quadrupole channel and transform the initially transversely round beam into a flat beam. Fermilab/NICADD Photoinjector Laboratory has performed a lot of experiments, a ratio of 50 of the transverse emittances in x and y plane has been achieved and the ratio of 100 and higher is underway of research. In this paper, the S-shaped flat beam, found both in experiments and simulations, is investigated. The nonlinear transverse force from the RF field when the beam passes the superconducting cavity is found to be one of the sources which produce the transverse S-shape distribution and increase the emittance. An extra solenoid located before the superconducting cavity is proposed to be added to adjust the beam transverse size when the beam passes through the cavity. The resulted transverse nonlinear space-charge force is used to counter-act against the nonlinear transverse force from the RF field. PARMELA simulations have shown that, with proper setup of the extra solenoid, the emittance ratio can be enhanced by a factor of 2 and the S-shaped transverse distribution can also be eliminated. |
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| WPAP042 | Progress on Using NEA Cathodes in an RF Gun | gun, ion, electron, cathode | 2708 | ||
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Funding: This work was supported by Universities Research Association Inc. under contract DE-AC02-76CH00300 with the U.S. DOE and by NICADD. AES personnel were supported under DOE SBIR contract #DE-FG02-04ER838. |
RF guns have proven useful in multiple accelerator applications, and are an attractive electron source for the ILC. Using a NEA GaAs photocathode in such a gun allows for the production of polarized electron beams. However the lifetime of a NEA cathode in this environment is reduced by ion and electron bombardment and residual gas oxidation. We report progress made with studies to produce a RF gun using a NEA GaAs photocathode to produce polarized electron beams. Attempts to reduce the residual gas pressure in the gun are discussed. Initial measurements of ion flux through the cathode port are compared with simulations of ion bombardment. Future directions are also discussed. |
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| WPAP043 | Production of Transverse Controllable Laser Density Distribution in Fermilab/NICADD Photoinjector | laser, electron, emittance, space-charge | 2783 | ||
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The Fermilab/NICADD photoinjector laboratory consist of a photoemission electron source based on an L band rf-gun. The CsTe photocathode is illuminated by an ultrashort UV laser. The transport line from the laser to the photocathode was recently upgraded to allow imaging of an object plane located ~20 m from the photocathode. This upgrade allows the generation of transverse laser distributions with controlled nonuniformity, yielding the production of an electron beam with various transverse densities patterns. Measuring the evolution of the artificial pattern on the electron bunch provides information that can be used to benchmark numerical simulations and investigate the impact of space charge. Preliminary data on these investigations are presented in the present paper.
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| WPAP046 | Injection Options for 12 GeV CEBAF Upgrade | gun, recirculation, injection, electron | 2911 | ||
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Funding: Work supported by DOE Contract DE-AC05-84ER40150. |
Jefferson Lab is planning to upgrade the CEBAF accelerator from 6 to 12 GeV. In order to achieve this, the beam energy at injection into the main accelerator needs to increase from 67 MeV to either 123 or 134 MeV depending on the location of the new experimental hall relative to the accelerator. The present 100 keV electron source and beam formation to 5 MeV will remain unchanged; however, the present accelerating cryomodules in the injector cannot reach the higher injection energies. Consequently, two options for attaining these energies are considered: (1) replacing the present injector cryomodules with new, higher gradient cryomodules, or (2) re-circulating the beam through the existing cryomodules to achieve the necessary energy gain in two passes. In this paper we present simulation results and list the advantages and disadvantages of these two options. |
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| WPAP055 | A 3D Parallel Beam Dynamics Code for Modeling High Brightness Beams in Photoinjectors | space-charge, emittance, cathode, brightness | 3316 | ||
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Funding: This work was supported by a SciDAC project in accelerator physics which is supported by the U.S. DOE/SC Office of High Energy Physics and the Office of Advanced Scientific Computing Research. |
In this paper we report on IMPACT-T, a 3D beam dynamics code for modeling high brightness beams in photoinjectors and rf linacs. IMPACT-T is one of the few codes used in the photoinjector community that has a parallel implementation, making it very useful for high statistics simulations of beam halos and beam diagnostics. It has a comprehensive set of beamline elements, and furthermore allows arbitrary overlap of their fields. It is unique in its use of space-charge solvers based on an integrated Green function to efficiently and accurately treat beams with large aspect ratio, and a shifted Green function to efficiently treat image charge effects of a cathode. It is also unique in its inclusion of energy binning in the space-charge calculation to model beams with large energy spread. Together, all these features make IMPACT-T a powerful and versatile tool for modeling beams in photoinjectors and other systems. In this paper we describe the code features and present results of IMPACT-T simulations of the LCLS and LUX photoinjectors. We also include a comparison of IMPACT-T and PARMELA results, and a comparison of IMPACT-T and ASTRA results. |
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| WPAP057 | Three-Dimensional Theory and Simulation of an Ellipse-Shaped Charged-Particle Beam Gun | emittance, electron, vacuum, focusing | 3372 | ||
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Funding: U.S. DOE: Grant No. DE-FG02-95ER40919, Grant No. DE-FG02-01ER54662, Air Force Office of Scientific Research: Grant No. F49620-03-1-0230, and the MIT Deshpande Center for Technological Innovation. |
A three-dimensional (3D) theory of non-relativistic, laminar, space-charge-limited, ellipse-shaped, charged-particle beam formation has been developed recently (Bhatt and Chen, PR:ST-AB, submitted Dec. 2004), whereby charged particles (electrons or ions) are accelerated across a diode by a static voltage differential and focused transversely by Pierce-type external electrodes placed along analytically specified surfaces. The treatment is extended to consider the perturbative effects of anode hole lensing, thermal isolation of the emitter, finiteness and nonuniformities of beam-forming electrodes, and an initial thermal spread. Analytic and semi-analytic results are presented along with 3D simulations utilizing the 3D trajectory code, OMNITRAK. Considerations with regard to beam matching into a periodic magnetic focusing lattice are discussed. |
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| WPAT001 | HFSS Simulation of Vacuum Tube RF Power Amplifiers | cyclotron, booster, vacuum, insertion | 767 | ||
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Funding: TRIUMF receives funding via a contribution agreement through the National Research Council of Canada. |
Development and upgrade of rf power amplifiers require comprehensive calculations to predict and optimize various parameters of the system before hardware modifications are applied. ANSOFT HFSS code provides a powerful tool for 3D EM simulation of the amplifier output resonator comprising a vacuum tube as a passive element. Two examples of this kind of simulation applied for upgrade of the TRIUMF Cyclotron rf system are presented in this paper. |
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| WPAT004 | Coupling Methods for Superconducting CH-Cavities | coupling, linac, vacuum | 922 | ||
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Funding: GSI, BMBF contr. No. 06F134I, EU. |
The cross-bar H-type (CH) cavity is a multi-gap drift tube structure based on the H-210 mode currently under development at IAP Frankfurt and in collaboration with GSI. Numerical simulations and rf model measurements showed that the CH-type cavity is an excellent candidate to realize Room Temperature and Superconducting multi-cell structures with a frequency range from about 150 MHz up to 800 MHz. For coupling into such a complex structure, we compare two coupling methods, one with capacitive and the other with inductive couplers. This paper will present detailed MicroWave Studio simulations and measurements for these different coupling methods for Room Temperature and Superconducting CH-Cavities. For coupling into a Superconducting CH-Cavity we prefer a capacitive coupler. We will also present an optimized Superconducting CH-Cavity for capacitive couplers. |
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| WPAT023 | Combining Cavity for RF Power Sources: Higher Power Testing and Further Simulation | 1823 | |||
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Funding: ASTeC, CCLRC Daresbury Laboratory. |
A combining cavity for RF power sources has been investigated previously reported in EPAC’04 using computer simulations in CSTs’ Microwave Studio© and by building a low power model out of aluminium. The model has now been tested at higher power in a number different configurations and compared with earlier results. This paper discusses the results of the higher power test and options for a combiner that can be used at the high power required for particle accelerators. It discusses further design and future modelling. |
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| WPAT038 | Instability of the RF Control Loop in the Presence of a High-Q Passive Superconducting Cavity | feedback, resonance, superconducting-RF, luminosity | 2553 | ||
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Funding: Work is supported by the National Science Foundation. |
An instability of the active RF cavity field control loop was observed during experiments with beam-driven (passive) superconducting cavities in CESR when the cavity external Q factor was raised to a value above 1x107. A computer model was developed and further experiments have been performed to study this instability and find a way to cure it. The results of simulations are presented alongside the experimental results. |
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| WPAT051 | Development of Toshiba L-Band Multi-Beam Klystron for European XFEL Project | cathode, klystron, gun, electron | 3153 | ||
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A 10MW L-band multi-beam klystron (MBK)is under develpment at Toshiba, Japan for DESY X-FEL and a future linear collider projects. The design goals are to have 10MW peak power with 65% efficiency at 1.5 ms pulse length at 10Hz repetition rates. The Toshiba MBK has six low-perveance beams operated at low voltage of 115kV (for 10MW) to enable a higher efficiency than a single-beam klystron for a similar power. The prototyp·10-0 has been built and is now under testing. At the first step, it was tested without RF and operates stably at the cathode voltage of 115KV at 1.7ms pulse length at 10Hz repetition rate with beam transmission of better than 99%. No spurious oscillation was observed. The testing is now progressed with RF on. Up to date of November 10, 2004, The output power of 10.3MW has been demonstrated at the beam voltage of 115kV with efficinecy of 68.4% at the RF pulse length of 1ms at 10Hz. The testing is under way to increase the RF pulse length to the goal value of 1.5ms. This paper summarizes the design and the testing results.
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| WPAT069 | Development of a Solid State RF Amplifier in the kW Regime for Application with Low Beta Superconducting RF Cavities | ion, booster, insertion, monitoring | |||
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Projects based on the use of low beta superconducting cavities for ions are under operation or development at several labs worldwide. Often these cavities are individually driven by RF power sources in the kW regime. For an ongoing project a modular 2 kW, 176 MHz unconditionally stable RF amplifier for CW and pulsed operation was designed, built, and tested. Extended thermal analysis was used to develop a water cooling system in order to optimize the performance of the power transistors and other thermally loaded components. The paper will outline the design concept of the amplifier and present first results on the test of the amplifier with a superconducting cavity.
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| WPAT083 | Steering and Focusing Effects in TESLA Cavity Due to High Order Mode and Input Couplers | focusing, coupling, electromagnetic-fields, linac | 4135 | ||
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Funding: This work was supported by Universities Research Association Inc. under contract DE-AC02-76CH00300 with the U.S. Department of Energy, and by NICADD. |
Many state-of-art electron accelerator proposals incorporate TESLA-type superconducting standing wave cavities. These cavities include input coupler (to feed the RF power into the cavity) and a pairs of high order mode couplers (HOM) to absorb the energy associated to HOM field excited as the bunch passes through the cavity. In the present paper we investigate, using numerical simulations, the impact of the input and HOM couplers on the beam dynamics. We show the overall effects are: a dipole kick (zeroth order) and normal and skew quadrupole-type focusing (first order). We present parametric studies of the strength of these effect for various operating gradients and incoming beam energies. We finally study the impact of this non-asymmetric field on the beam dynamics, taking as an example the low energy section of the European X-FEL injector. |
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| WPAT086 | Superconducting RF Cavity Frequency and Field Distribution Sensitivity Simulation | SNS, radiation, superconducting-RF, resonance | 4194 | ||
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Funding: Under contract DE-AC05-00OR22725 for the U.S. Department of Energy. |
Frequency and electromagnetic field distribution sensitivity of a superconducting RF (SRF) cavity due to cavity’s small deformation are the fundamental phyical paramethers in cavity and tuner design. At low temperature, the frequency sensitivity can be obtained by measuring prototype cavity, but it is not easy to test the filed distribution sensitivity. This paper presents and describes a simulation method combining ANSYS and SUPERFISH to calculate the cavity frequency and field distribution variation due to cavity’s small deformation caused by mechanical force, radiation force, thermal expansion etc.. As an example, the simulation results of the frequency and field flatness sensitivity on the SNS cavities were confirmed by their test results. sun_ancn@yahoo.com |
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| WPAT093 | A Three-Cell Superconducting Deflecting Cavity Design for the ALS at LBNL | impedance, damping, dipole, coupling | 4287 | ||
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Deflecting RF cavities can be used to generate sub-pico-second x-rays by creating correlations between longitudinal and transverse phase space of electron bunches in radiation devices. Up to 2-MV defecting voltage at 1.5-GHz is required for 1.9-GeV electron beam at the Advanced Light Source (ALS) at LBNL. We present a conceptual design for a 1.5-GHz three-cell superconducting RF cavity and its coupler. The cavity geometry and deflecting shunt impedance are optimized using MAFIA code. The cavity impedance from lower and higher order modes (LOM and HOM) are computed. Possible schemes for damping most harmful LOM and HOM modes are discussed and simulated.
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| WPAT094 | Traveling Wave Accelerating Structure for a Superconducting Accelerator | feedback, acceleration, superconductivity, linear-collider | 4296 | ||
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We are presenting a superconducting traveling wave accelerating structure (STWA) concept, which may prove to be of crucial importance to the International Linear Collider. Compared to the existing design of a TESLA cavity, the traveling wave structure can provide ~20-40% higher accelerating gradient for the same aperture and the same peak surface magnetic RF field. The recently achieved SC structure gradient of 35 MV/m can be increased up to ~50 MV/m with the new STWA structure design. The STWA structure is supposed to be installed into the superconducting resonance ring and is fed by the two couplers with appropriate phase advance to excite a traveling wave inside the structure. The system requires two independent tuners to be able to adjust the cavity and feedback waveguide frequencies and hence to reduce the unwanted backward wave. In this presentation we discuss the structure design, optimization of the parameters, tuning requirements and plans for further development.
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| WOAB010 | BUNCH TRACING BY BUNCH BY BUNCH MEASUREMENT SYSTEM IN HLS | injection, wiggler, feedback, storage-ring | 719 | ||
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Funding: Supported by National Natural Science Project (10175063) |
In this paper, we introduce a bunch tracing system which is based on a bunch-by-bunch (BxB) measurement system in Hefei Light Source (HLS), and present the analysis of the experiment results. Using an in-phase gate signal and a double balance mixer to control an external trigger of ADC, we test the reliability of the BxB system. By this system, we can trace all marked bunches in a set time slot or in manual burst mode. We can record all bunches’ data during the injection, ramping, wiggler excitation and normal operation, and provide a powerful facility for machine study. |
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| WOPA002 | Experimental Results from the Small Isochronous Ring | space-charge, cyclotron, electron, focusing | 159 | ||
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Funding: Work supported by NSF Grant # PHY-0110253 and DOE Contract DE-AC05-84ER40150. |
The Small Isochronous Ring (SIR) is a compact, low-energy storage ring designed to investigate the beam dynamics of high-intensity isochronous cyclotrons and synchrotrons at the transition energy. The ring was developed at Michigan State University and has been operational since December 2003. It stores 20 keV hydrogen beams with a peak current of 10-20 microamps for up to 200 turns. The transverse and longitudinal profiles of extracted bunches are measured with an accuracy of approximately 1 mm. The high accuracy of the measurements makes the experimental data attractive for validation of multi-particle space charge codes. The results obtained in the ring show a fast growth of the energy spread induced by the space charge forces. The energy spread growth is accompanied by a breakup of the beam bunches into separated clusters that are involved in the vortex motion specific to the isochronous regime. The experimental results presented in the paper show a remarkable agreement with simulations performed with the code CYCO. In this paper, we discuss specifics of space charge effects in the isochronous regime, present results of experiments in SIR, and conduct a detailed comparison of the experimental data with results of simulations. |
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| ROAA005 | Recent Innovations in Muon Beam Cooling and Prospects for Muon Colliders | emittance, collider, beam-cooling, resonance | 419 | ||
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Funding: This work was supported in part by DOE SBIR/STTR grants DE-FG02-02ER86145, 03ER83722, 04ER84015, 04ER86191, and 04ER84016. |
A six-dimensional(6D)cooling channel based on helical magnets surrounding RF cavities filled with dense hydrogen gas* is used to achieve the small transverse emittances demanded by a high-luminosity muon collider. This helical cooling channel**(HCC) has solenoidal, helical dipole, and helical quadrupole magnetic fields to generate emittance exchange. Simulations verify the analytic predictions and have shown a 6D emittance reduction of over 3 orders of magnitude in a 100 m HCC segment. Using three such sequential HCC segments, where the RF frequencies are increased and transverse dimensions reduced as the beams become cooler, implies a 6D emittance reduction of almost six orders of magnitude. After this, two new post-cooling ideas can be employed to reduce transverse emittances to one or two mm-mr, which allows high luminosity with fewer muons than previously imagined. In this report we discuss the status of and the plans for the HCC simulation and engineering efforts. We also describe the new post-cooling ideas and comment on the prospects for a Higgs factory or energy frontier muon collider using existing laboratory infrastructure. *R. P. Johnson et al. LINAC2004, www.muonsinc.com/TU203.pdf. **Y. Derbenev and R.P. Johnson, Submitted to PRSTAB, http://www-mucool.fnal.gov/mcnotes/public/pdf/muc0284/muc0284.pdf. |
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| ROAC007 | RF Breakdown in Normal Conducting Single-cell Structures | electron, vacuum, ion, linear-collider | 595 | ||
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Funding: Work supported by the U.S. Department of Energy contract DE-AC02-76SF00515. |
Operating accelerating gradient in normal conducting accelerating structures is often limited by rf breakdown. The limit depends on multiple parameters, including input rf power, rf circuit, cavity shape and material. Experimental and theoretical study of the effects of these parameters on the breakdown limit in full scale structures is difficult and costly. We use 11.4 GHz single-cell traveling wave and standing wave accelerating structures for experiments and modeling of rf breakdown behavior. These test structures are designed so that the electromagnetic fields in one cell mimic the fields in prototype multicell structures for the X-band linear collider. Fields elsewhere in the test structures are significantly lower than that of the single cell. The setup uses matched mode converters that launch the circular TM01 mode into short test structures. The test structures are connected to the mode launchers with vacuum rf flanges. This setup allows economic testing of different cell geometries, cell materials and preparation techniques with short turn-around time. Simple 2D geometry of the test structures simplifies modeling of the breakdown currents and their thermal effects. |
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| ROAC010 | Development of Ultra-Fast Silicon Switches for Active X-Band High Power RF Compression Systems | power-supply, insertion, extraction, vacuum | 701 | ||
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Funding: DOE |
In this paper, we present the recent results of our research on the high power ultra-fast silicon RF switches. This switch is composed of a group of PIN diodes on a high purity SOI (silicon on oxide) wafer. The wafer is inserted into a cylindrical waveguide under T·1001 mode, performing switching by injecting carriers into the bulk silicon. Our current design is using a CMOS compatible process and the fabrication is accomplished at SNF (Stanford Nanofabrication Facility). This design is able to achieve sub-100ns switching time, while the switching speed can be improved further with 3-D device structure and faster circuit. Power handling capacity of the switch is at the level of 10MW. The switch was designed for active X-band RF pulse compression systems - especially for NLC, but it is also possible to be modified for other applications and other frequencies such as L-band. |
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| RPAE002 | Coupling Correction of a Circularly Polarizing Undulator at the Advanced Photon Source | quadrupole, coupling, octupole, undulator | 805 | ||
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Funding: This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. |
The electromagnetic Circularly Polarizing Undulator (CPU) installed at the Advanced Photon Source (APS) storage ring produces skew quadrupole field errors, which were initially corrected by a small skew quadrupole magnet at one end of the device. Because the storage ring is operated at 1% coupling or less, a correction not located at the source inside the CPU is insufficient, as we have confirmed in simulation. Adding a skew coil at the other end of the CPU allows us to make a complete correction of the coupling source in the undulator. Correction setpoints are determined by APS's general optimizing software with the vertical beam size of a x-ray pinhole image as a readback. |
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| RPAE045 | Production of Short Electron Bunches by Slow and Fast Excitations of Longitudinal Bunch-Shape Oscillations | synchrotron, radiation, storage-ring, damping | 2887 | ||
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In the Brookhaven Alternating Gradient Synchrotron (AGS), adiabatic excitation of longitudinal bunch-shape oscillations has been successfully used for extracting shortened proton bunches.* We applied this technique to the electron storage ring. In case of electron machines, growth time of bunch-shape oscillations should be shorter than the radiation damping time for preventing radiation excitation. We demonstrated in the 2.5-GeV Photon Factory storage ring that electron bunches could be shortened by a factor of about two from its natural length using this technique. We show that non-adiabatic excitation of oscillations is also very useful for obtaining shorter bunches.
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*M. Bai et al., Phys. Rev. ST Accel. Beams 3, 064001 (2000). |
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| RPAE053 | Transient Generation of Short Pulses in the APS Storage Ring | synchrotron, storage-ring, single-bunch, photon | 3247 | ||
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Funding: This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. |
A method for obtaining very short pulses using modulation of the accelerating voltage gradient is described and simulation results given. The idea is to operate the two rf stations with a phase separation adjusted so that the synchronous particle resides on the crest of one of the sources. Phase modulation of the on-crest system at twice the synchrotron frequency induces a longitudinal bunch shape oscillation with significantly reduced bunch length occurring twice each synchrotron period. Pulsed and steady-state operation will be discussed using various accelerator parameters. |
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| RPAE060 | Simulation and Automation of the EEBI Test at ALS | target, vacuum, monitoring, synchrotron | 3485 | ||
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Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. |
The Errant Electron Beam Interlock (EEBI) is a system that protects the vacuum chamber of the Advanced Light Source (ALS) from synchrotron light damage should the orbit, through a superconducting bend magnet (superbend), become distorted. The EEBI system monitors the vertical beam position on two BPMs, one upstream and the other downstream, of the superbend and dumps the stored beam if the orbit exceeds preset limits in either offset or angle. Discussed are the modeling studies carried out to determine how to create a large vertical bump, both for performing the test and implementing the automated test software. |
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| RPAE061 | Beam Loss Simulation Studies for ALS Top-Off Operation | injection, radiation, electron, storage-ring | 3532 | ||
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Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. |
The ALS is planning to operate with top-off injection at higher beam currents and smaller vertical beam size. As part of a radiation safety study for top-off, we carried out two kinds of tracking studies: (1) to confirm that the injected beam cannot go into users’ photon beam lines, and (2) to control the location of beam dump when the storage ring RF is tripped. (1) is done by tracking electrons from a photon beam line to the injection sector inversely by including the magnetic field profiles, varying the field strength with geometric aperture limits to conclude that it is impossible. (2) is done by tracking an electron with radiation in the 6-dim space for different combinations of vertical scrapers for the realistic lattice with errors. |
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| RPAE067 | Investigations, Experiments, and Implications for Using Existing Pulse Magnets for 'topoff' Operation at the Advanced Light Source | septum, booster, storage-ring, injection | 3727 | ||
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Funding: This work was supported by the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. |
ALS top-off mode of operation will require injection of the electron beam from the Booster Ring into the Storage Ring at the full ALS energy level of 1.9GeV. Currently the Booster delivers a beam at 1.5GeV to the Storage Ring where it is then ramped to the full energy and stored for the user operation. The higher Booster beam energy will require the pulse magnets in the Booster and Storage Rings to operate at proportionally higher magnetic gap fields. Our group studied and tested the possible design and installation modifications required to operate the magnets and drivers at "top-off" levels. Our results and experiments show that with minor electrical modifications all the existing pulse magnet systems can be used at the higher energy levels, and the increased operational stresses should have a negligible impact on magnet reliability. Furthermore, simple electrical modifications to the storage ring thick septum will greatly reduce the present level of septum stray leakage fields into the storage ring beam. |
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| RPAE071 | Touschek Lifetime and Undulator Damage in the Advanced Photon Source | scattering, injection, radiation, lattice | 3835 | ||
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Funding: Work supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. |
The Advanced Photon Source (APS) has two insertion devices (IDs) with small-aperture vacuum chambers. The full vertical aperture in these chambers is 5 mm, while the inboard horizontal aperture is 15 mm. These devices suffer significant radiation damage, requiring frequent retuning. We recently hypothesized that the damage resulted from loss of Touschek-scattered particles on the horizontal aperture of the chambers. This results partly from the smallness of the aperture and partly from the pattern of the dispersion and beta functions in the low-emittance APS lattice. The horizontal scrapers were originally at a high-dispersion location, but, in the low-emittance lattice, they are at a fairly low-dispersion location. Similarly, the dispersion at the IDs was originally zero but is now close to the maximum for the lattice. In this paper, we summarize simulations and experiments that support our hypothesis and discuss plans to remedy the problem. |
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| RPAE073 | Generating Picosecond X-Ray Pulses with Beam Manipulation in Synchrotron Light Sources | synchrotron, photon, coupling, electron | 3898 | ||
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Funding: Work supported by U. S. Department of Energy, Office of Basic Energy Sciences under Contract No. W-31-109-ENG-38. |
The length of x-ray pulses generated by storage ring light sources is usually tens of picoseconds. For example, the value is 40 ps rms at the Advanced Photon Source (APS). Methods of x-ray pulse compression are of great interest at the APS. One possible method, per Zholents et al., is to tilt the electron bunch with deflecting rf cavities.* Alternately, we found that the electron bunch can develop a tilt after application of a vertical kick in the presence of nonzero chromaticity. After slicing, the x-ray pulse length is determined by the tilt angle and the vertical beam size. In principal, sub-picosecond pulses can be obtained at APS. To date we have observed 6 ps rms visible light pulses with a streak camera. Efforts are underway to attempt further compression of the x-ray pulse and to increase the brilliance. This method can be easily applied to any storage ring light sources to generate x-ray pulses up to two orders of magnitude shorter than the electron bunch length. In this paper, we will present the theory of bunch tilt, particularly the synchrobetatron coupling and decoherence beam dynamics, and the simulation and the experimental results will also be shown as verification. *A. Zholents et al., NIM A 425, 385(1999). |
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| RPAP002 | A CW RFQ Accelerator for Deuterons | rfq, alignment, vacuum, injection | 794 | ||
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Funding: BMBF |
A four-rod RFQ accelerator is being built to accelerate deuterons from 20 keV to 3 MeV. At an operating frequency of 176 MHz the length is 3.8 m and the power consumption 250 kW, the beam current 5 mA. A special feature is the CW-mode operation. The status of the project and properties of the RFQ will be discussed. |
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| RPAP004 | Simulations for the Frankfurt Funneling Experiment | rfq, beam-transport, ion, linac | 901 | ||
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Funding: BMBF |
Beam simulations for the Frankfurt Funneling Experiment are done with RFQSim and FUSIONS. RFQSim is a particle dynamic program to compute macro particle bunches in the 6D phase space through a RFQ accelerator. Behind the RFQ the simulation software FUSIONS calculates both beam lines through a r.f. funneling deflector. To optimise beam transport of existing and new funneling deflector structures FUSIONS is presently being developed. The status of the development of FUSIONS and the results will be presented. |
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| RPAP012 | Dual Energy X-Ray CT by Compton Scattering Hard X-Ray Source | scattering, electron, linac, photon | 1291 | ||
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We have developed a compact Compton scattering hard X-ray source at Nuclear Engineering Research Laboratory, University of Tokyo. The compact hard X-ray source can produce tunable monochromatic hard X-rays. The monochromatic hard X-rays are required in large field of medical and biological applications. We are planning to perform dual-energy X-ray CT, which enables us to measure atomic number Z distribution and electron density re distribution in a material. The hard X-ray source has an advantage to perform dual-energy X-ray CT. The X-ray energy can be changed quickly by introducing a fundamental frequency and a second harmonic frequency lasers. This quick energy change is indispensable to medical imaging and very difficult in a large SR light source and others. The information on the atomic number and electron density will be used for treatment plan in radiotherapy as well as for identification of materials in a nondestructive test. We examined applicability of the dual-energy X-ray CT for atomic number measurement for low to medium Z elements (Z=30) by considering the X-ray profile generated by Compton scattering. Details of the numerical simulations and plans of the dual-energy X-ray CT will be reported in the conference.
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| RPAP013 | Characteristic Experimentations of Degrader and Scatterer at MC-50 Cyclotron | proton, cyclotron, target, monitoring | 1356 | ||
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Funding: This work is a part of the "Proton Engineering Frontier Project" which is sponsored by the Ministry of Science and Technology of Korea under "21C Frontier R&D Program." |
Building proton beam user facilities, especially deciding beam energy level, depends on the attached proton accelerator and users' needs. To adjust beam energy level, two methods are generally used. One is to directly adjust the beam in the accelerator. The other is to adjust beam energy after extracting from the accelerator. Degrader/Scatterer System has been installed in the MC-50 Cyclotron to adjust energy level of the beam used for various application fields. Its degrader and scatterer are made of Al foils and Au foils, respectively. Al thickness are 2, 1, 0.5, 0.3, 0.2, 0.1, 0.05, 0.03, 0.02, 0.01mm and Au thickness are 0.2, 0.1, 0.05, 0.03, 0.02, 0.01mm, respectively. In this study, suitable beam condition was adjusted through overlapping Al/Au foils of various thickness through simulation results. After that, LET(Linear Energy Transfer) value was indirectly acquired by measuring the bragg peak of the external beam through PMMA plastic Phantom and profile was measured by film dosimetry. |
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| RPAP014 | Uniform Irradiation Systems Using a Rotatable Stage for Test Facilities of PEFP | target, proton, dipole, cyclotron | 1383 | ||
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Funding: This work is a part of the "Proton Engineering Frontier Project" which is sponsored by the Ministry of Science and Technology of Korea under '21C Frontier R&D Program." |
A new irradiation facility has been developed using not only electric magnets but also a rotatable stage. Generally, the scanning method using magnet has been widely used in most of facilities. However, in this study another new methods have been developed: Three scanning method using rotatable stage have been proved to make uniform irradiation-as large as 20 cm in diameter with more than 90% uniformity. The mechanical wobbler system makes the same effect as the wobbler system. And the beam is swept along the spiral path with a fixed and variable angular frequency during the scanning in two spiral scanning systems, respectively. |
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| RPAP015 | Modeling of Internal Injection and Beam Dynamics for High Power RF Accelerator | electron, cathode, injection, focusing | 1419 | ||
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Funding: The work is supported by ISTC grant #2550. |
A new high power electron accelerator for industrial applications is developed in Novosibirsk. Main parameters of the accelerator are: operating frequency of 176 MHz, energy of electrons of 5 MeV, average beam power up to 300 kW. The accelerator consists of a chain of accelerating cavities, connected by the on-axis coupling cavities with coupling slots in the walls. A triode RF gun on the base of grid-cathode unit placed on the wall of the first accelerating cavity is used for internal injection of electrons. The paper presents the results of modeling and optimization of the accelerating structure, internal injection, and beam dynamics. |
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| RPAT001 | Experimental Results of a Non-Destructive Emittance Measurement Device for H- Beams | ion, emittance, laser, dipole | 782 | ||
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For the diagnostic of high power ion beams, non-destructive measurement devices should not only provide minimum influence on the beam itself, but also avoid various problems that occur when the high power density of the beam penetrates surfaces like slit- or pinhole plates. On the other hand, measurements of resolution should be comperable with destructive methods. Beams of negative ions offer the use of a non-destructive Emittance Measurement Instrument (EMI) based on the principle of photo detachment. Interaction of laser photons with the negative ions causes electron detachment. Due to moving the postion of the well collimated laser beam acros the ion beam the produced neutral atoms are well suited to detect the transverse beam emittance like a classical slit-grid device. After separation in a magnetic dipole, the neutrals can be viewed on a scintillator screen with a CCD camera. To investigate the use of such a photo detachment EMI and to study the transport of negative ions an experiment consisting of H minus ion source, electrostatic LEBT and EMI was constructed. The paper will present the setup of the experimental hardware and first results of measurements.
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| RPAT038 | Diagnostic for Electron Clouds Trapped in Quadrupoles | electron, quadrupole, diagnostics, proton | 2547 | ||
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Funding: Work supported by a DOE SBIR Phase I grant DE-FG02-04ER84105. |
Simulations have indicated that electron clouds generated by beam-induced multipactor can be trapped in the mirror-like fields of magnetic quadrupoles and thereby contribute significantly to the electron cloud buildup in high intensity accelerators and storage rings. This could be the most important source of electrons driving the two-stream (e-p) instability at the Los Alamos PSR and may also play a significant role in electron cloud effects at some of the new high intensity accelerator projects. We will describe the physics design and optimization of an electron-sweeping detector designed to measure the trapped electrons at various times after the beam pulse has passed. The instrument can also serve as an electro-magnetically shielded detector providing a signal obtained from electrons striking the wall during the passage of beam bunches. |
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| RPAT039 | Feasibility Study of Using an Electron Beam for Profile Measurements in the SNS Accumulator Ring | electron, proton, SNS, vacuum | 2586 | ||
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. |
The design goal for the SNS ring is to accumulate 2·1014 protons per 1ms pulse at a 60Hz repetition rate. Achieving the design beam intensity with acceptable losses is a challenging task, which could be tackled more easily if reliable measurements of the beam profile in the ring are available. The high power density of the beam precludes the use of conventional wire scanners or harps and therefore non-interceptive types of profiles measurements are required. The electron beam probe method was suggested for measuring profiles in high power beams. In this method, deflection of a low energy electron beam by the collective field of the high intensity beam is measured. The charge density in the high intensity beam can be restored under certain conditions or estimated by various mathematical techniques. We studied the feasibility of using the electron beam probe for the SNS accumulator ring using computer simulations of the diagnostic setup. A realistic electron gun model and realistic proton beam distributions were used in the simulations. Several profile calculation techniques were explored and the results are reported in this paper. |
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| RPAT040 | Matching BPM Stripline Electrodes to Cables and Electronics | impedance, SNS, dipole, linac | 2607 | ||
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Funding: This work was supported by SNS through UT-Batelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE. The SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge. |
The Spallation Neutron Source (SNS) is an accelerator-based neutron source being built at Oak Ridge National Laboratory. The 805-MHz coupled-cavity linac (CCL) accelerates an H- beam from 86 to 186 MeV, while the 805 MHz superconducting-cavity linac (SCL) accelerates the beam to its final energy of 1 GeV. The SNS beam position monitors (BPMs) which are used to measure both position and phase of the beam relative to the master oscillator, have the dual-planed design with four one-end-shorted stripline electrodes. We argue that the BPMs are optimally broadband matched to the cabling and electronics when the geometrical mean of the sum-mode and quadrupole-mode impedances is equal to the external-line impedance, 50 Ohms. The analytical results, MAFIA and HFSS simulations, wire measurements, and beam measurements that support this statement are presented. |
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| RPAT049 | Numerical Studies on the Electro-Optic Sampling of Relativistic Electron Bunches | laser, electron, resonance, lattice | 3070 | ||
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Ultraviolet and X ray free electron lasers require sub-picosecond electron bunches of high charge density. Electro-optic sampling (EOS) is a suitable diagnostic tool for resolving the time structure of these ultrashort bunches. The transient electric field of the relativistic bunch induces a polarization anisotropy in a nonlinear crystal which is sampled by femtosecond laser pulses. In this paper, the EOS process is studied in detailed numerical calculations. The THz and the laser pulses are treated as wave packets which are propagated through the zinc telluride resp. gallium phosphide crystals. The effects of signal broadening and distortion are taken into account. The time resolution is limited by the lowest lattice oscillation frequency which amounts to 5.3 THz in ZnTe and 11 THz in GaP. The shortest bunch length which can be resolved with moderate distortion is about 200 fs (FWHM) in ZnTe and 100 fs in GaP.
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| RPAT051 | Measurement of Dynamic Beam-Beam Effects on Horizontal Beam Size at KEKB Using SR Interferometer Equipped with Retrofocus Optics | optics, emittance, beam-beam-effects, positron | 3150 | ||
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Transverse beam-size enlargement due to dynamic beta and beam-beam effects has been observed in the KEKB Low Energy Ring (LER) and High Energy Ring (HER). In order to observe these effects, a retrofocus optics system has been developed and installed in the horizontal SR interferometers at the HER and LER. This system allows us to vary the apparent beam size to match the dynamic range of the interferometer. We report on the retrofocus optics system and measurement results, and compare the measured effects with those expected from dynamic beta simulations.
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| RPAT070 | Mechanical and Thermal Design of the CEBAF Hall A Beam Calorimeter | radiation, vacuum, electron, target | 3819 | ||
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Funding: DOE. |
A calorimeter has been proposed to provide 0.5% - 1.0% absolute measurements of beam current in the Hall A end station of the Thomas Jefferson National Accelerator Facility (JLab) CEBAF machine. Silver and copper calorimeters built in the 1960’s achieved precisions of about 1%. Modern powder metallurgy processes have produced high density, high thermal conductivity tungsten-copper composite materials that will minimize beam loss while maintaining a rapid thermal response time. Heat leaks will be minimized by mounting the mass in vacuum on glass ceramic mounts. A conduction cooling scheme utilizes an advanced carbon fiber compliant thermal interface material. Transient finite difference and finite element models were developed to estimate heat leaks and thermal response times. |
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| RPAT072 | The General ElectroN Induced Emission (GENIE) System | electron, dipole, beam-transport, emittance | 3877 | ||
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A real time beam diagnostic system is proposed for the Jefferson Lab injector region. The General ElectroN Induced Emission System (GENIE) is a package that includes both hardware (beam monitoring devices) and software (for 3D or 4D visualization of the beam transport). This beam diagnostic tool relies primarily on the use of (very small) scintillating fibers placed in different planes to extract the beam profile, beam position, beam current and beam emittance in real time. Accuracies in position and angle could be at the sub- μm and μrad levels, respectively. The beam current could be reconstructed within a few percent. A combined Geant4/Parmela simulation will be developed for beam optic studies. While Parmela offers the power of beam transport with phase matching capabilities (among others), Geant4 provides the power for tracking secondary particles, as well as 3D & 4D visualization. A phase I investigation of GENIE using a 100 keV beam line is discussed in this document.
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| RPAT083 | Beam Profile Measurements and Simulations of the PETRA Laser-Wire | laser, electron, photon, collider | 4123 | ||
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The laser-wire will be an essential diagnostic tool at the International Linear Collider and advanced light sources. It uses a finely focussed laser beam to measure the transverse profile of electron bunches by detecting the Compton-scattered photons (or electrons) downstream of where the laser beam intersects the electron beam. Such a system has been installed at the PETRA storage ring at DESY, which uses a piezo-driven mirror to scan the laser light across the electron beam. Latest experimental results are presented and compared to detailed simulations using Geant4.
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| RPAT084 | Design of the APS RF BPM Data Acquisition Upgrade | feedback, storage-ring, instrumentation, shielding | 4156 | ||
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Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. |
The Advanced Photon Source (APS) is a third-generation synchrotron light source in its tenth year of operation. The storage ring employs three different types of beam position monitor (BPM) systems to measure and control beam motion. The monopulse radio frequency (rf) BPM is a broadband (10 MHz) system, which is considered to be the backbone of orbit control. The rf BPM system was designed to measure single-turn and multi-turn beam positions. The rf BPMs are presently suffering from an aging data acquisition system. By replacing only the data acquisition we will revitalize this system for another decade and demonstrate a cost-effective approach to improved beam stability, reliability, and enhanced postmortem capabilities. In this paper we present the design of an eight-channel ADC/digitizer VXI board with a sampling rate of 88 MHz (per channel) and 14-bit resolution coupled with a field-programmable gate array and embedded central processing. We will discuss the upgrade system specifications, design, and prototype test results. |
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| RPAT089 | Advances in Optical Transition and Diffraction Radiation Emittance Diagnostics | emittance, electron, optics, diagnostics | 4224 | ||
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Funding: Office of Naval Research and the DOD Joint Technology Office. |
We have performed a series of experiments using Optical Transition Radiation and Optical Diffraction Radiation Interferometry to measure the two orthogonal (x,y) rms divergences of the Brookhaven National Laboratory’s Advanced Test Facility electron beam operating at an energy of 50 MeV. Measurement of the rms divergences at the (x,y) beam waist conditions, together with corresponding measurements of the rms beam sizes allows a determination of the rms x and y emittances. A comparison of the results using OTRI and ODTRI are presented. |
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| RPAT091 | Longitudinal Electron Bunch Diagnostics Using Coherent Transition Radiation | electron, radiation, laser, linac | 4254 | ||
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The longitudinal charge distribution of electron bunches in the Fermilab A0 photo-injector was determined by using the coherent transition radiation produced by electrons passing through a thin metallic foil. The auto-correlation of the transition radiation signal was measured with a Michelson type interferometer. The response function of the interferometer was determined from measured and simulated power spectra for low electron bunch charge and maximum longitudinal compression. Kramers-Kroning technique was used to determine longitudinal charge distribution. Measurements were performed for electron bunch lengths in the range from 0.3 to 2 ps (rms).
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| ROAB004 | Ion Effects in the DARHT-II Downstream Transport | ion, septum, target, ion-effects | 375 | ||
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Funding: Work supported by US NNSA/DOE. |
The DARHT-II accelerator produces an 18-MeV, 2-kA, 2-μs electron beam pulse. After the accelerator, the pulse is delivered to the final focus on an x-ray producing target via a beam transport section called the Downstream Transport. Ions produced due to beam ionization of residual gases in the Downstream Transport can affect the beam dynamics. Ions generated by the head of the pulse will cause modification of space-charge forces at the tail of the pulse so that the beam head and tail will have different beam envelopes. They may also induce ion-hose instability at the tail of the pulse. If these effects are significant, the focusing requirements of beam head and tail at the final focus will become very different. The focusing of the complete beam pulse will be time dependent and difficult to achieve, leading to less efficient x-ray production. In this paper, we will describe the results of our calculations of these ion effects at different residual-gas pressure levels. Our goal is to determine the maximum residual-gas pressure allowable in DARHT-II Downstream Transport such that the required final beam focus is achievable over the entire beam pulse under these deleterious ion effects. |
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| ROPB001 | Suppressing Electron Cloud in Future Linear Colliders | electron, damping, vacuum, collider | 24 | ||
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Funding: Work supported by the U.S. DOE under contract DE-AC02- 76SF00515. |
Any accelerator circulating positively charged beams can suffer from a build-up of an electron cloud in the beam pipe. The cloud develops through ionization of residual gases, synchrotron radiation and secondary electron emission and, when severe, can cause instability, emittance blow-up or loss of the circulating beam. The electron cloud is potentially a limiting effect for both the Large Hadron Collider (LHC) and the International Linear Collider (ILC). For the ILC positron damping ring, the development of the electron cloud must be suppressed. This paper presents the various effects of the electron cloud and evaluates their significance. It also discusses the state-of-the-art of the ongoing international R&D program to study potential remedies to reduce the secondary electron yield to acceptably low levels. |
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| ROPB002 | Experiments Studying Desorbed Gas and Electron Clouds in Ion Accelerators | electron, ion, quadrupole, diagnostics | 194 | ||
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Funding: This work was performed under the auspices of the U.S. Department of Energy by University of California, LLNL under contract No. W-7405-Eng-48, and by LBNL under Contract DE-AC03-76F00098. |
Electron clouds and gas pressure rise limit the performance of many major accelerator rings. We are studying these issues experimentally with ~1 MeV heavy-ion beams, coordinated with significant efforts in self-consistent simulation and theory.* The experiments use multiple diagnostics, within and between quadrupole magnets, to measure the sources and accumulation of electrons and gas. In support of these studies, we have measured gas desorption and electron emission coefficients for potassium ions impinging on stainless steel targets at angles near grazing incidence.** Our goal is to measure the electron particle balance for each source – ionization of gas, emission from beam tubes, and emission from an end wall – determine the electron effects on the ion beam and apply the increased understanding to mitigation. *J-L. Vay, Invited paper, session TICP; R. H. Cohen et al., PRST-AB 7, 124201 (2004). **M. Kireeff Covo, this conference; A. W. Molvik et al., PRST-AB 7, 093202 (2004). |
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| ROPB004 | Effect of Lattice and Electron Distribution in Electron-Cloud Instability Simulations for the CERN SPS and LHC | electron, emittance, lattice, dipole | 387 | ||
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Several simulation codes have been adapted so as to model the single-bunch electron-cloud instability including a realistic variation of the optical functions with longitudinal position. In addition, the electron cloud is typically not uniformly distributed around the ring, as frequently assumed, but it is mainly concentrated in certain regions with specific features, e.g., regions which give rise to strong multipacting or suffer from large synchrotron radiation flux. Particularly, electrons in a dipole magnet are forced to follow the vertical field lines and, depending on the bunch intensity, they may populate two vertical stripes, symmetrically located on either side of the beam. In this paper, we present simulation results for the CERN SPS and LHC, which can be compared with measurements or analytical predictions.
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| ROPB005 | Recent Experiment Results on Fast Ion Instability at 2.5 GeV PLS | vacuum, ion, storage-ring, damping | 466 | ||
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We present recent experiment results on the fast ion instability that were performed at the PLS storage ring. With higher vacuum pressures of three orders of magnitude than nominal one by He gas injection into the ring, increases of a factor of around three in the vertical beam size were observed by interferometer system. From the various measurement results, we estimated growth times for the instability as a funcion of vacuum pressure and beam current. We also compared the results with those of the computer simulations and analytical calculations.
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| ROPB006 | Filling in the Roadmap for Self-Consistent Electron Cloud and Gas Modeling | electron, ion, quadrupole, heavy-ion | 525 | ||
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Funding: This work was performed under the auspices of the U.S. Department of Energy by University of California, LLNL and LBNL under contracts W-7405-Eng-48, and DE-AC03-76F00098. |
Electron clouds and gas pressure rise limit the performance of many major accelerators. A multi-laboratory effort to understand the underlying physics via the combined application of experiment,* theory, and simulation is underway. We present here the status of the simulation capability development, based on a merge of the three-dimensional parallel Particle-In-Cell accelerator code WARP and the electron cloud code POSINST, with additional functionalities.** The development of the new capability follows a "roadmap" describing the different functional modules, and their inter-relationships, that are ultimately needed to reach self-consistency. Newly developed functionalities include a novel particle mover bridging the time scales between electrons and ions motion.*** Samples of applications of the new capability to the modeling of intense charge dominated beams**** and LHC beams***** will be shown as available. *A.W. Molvik, these proceedings. **J.-L. Vay, Proc. "ECLOUD04," Napa (California), 2004. ***R.H. Cohen, these proceedings. ****P.A. Seidl, these proceedings. *****M.A. Furman, these proceedings. |
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| ROPB007 | 3-D Parallel Simulation Model of Continuous Beam-Electron Cloud Interactions | electron, betatron, emittance, synchrotron | 549 | ||
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A 3D Particle-In-Cell model for continuous modeling of beam and electron cloud interaction in a circular accelerator is presented. A simple model for lattice structure, mainly the Quadruple and dipole magnets and chromaticity have been added to a plasma PIC code, QuickPIC, used extensively to model plasma wakefield acceleration concept. The code utilizes parallel processing techniques with domain decomposition in both longitudinal and transverse domains to overcome the massive computational costs of continuously modeling the beam-cloud interaction. Through parallel modeling, we have been able to simulate long-term beam propagation in the presence of electron cloud in many existing and future circular machines around the world. The exact dipole lattice structure has been added to the code and the simulation results for CERN-SPS and LHC with the new lattice structure have been studied. Also the simulation results are compared to the results from the two macro-particle modeling for strong head-tail instability. It is shown that the simple two macro-particle model can capture some of the physics involved in the beam- electron cloud interaction qualitatively.
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| ROPB008 | Halo Mitigation Using Nonlinear Lattices | focusing, collimation, damping, space-charge | 620 | ||
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This work shows that halos in beams with space charge effects can be controlled by combining nonlinear focusing and collimation. The study relies on Particle-in-Cell (PIC) simulations for a one dimensional, continuous focusing model. The PIC simulation results show that nonlinear focusing leads to damping of the beam oscillations thereby reducing the mismatch. It is well established that reduced mismatch leads to reduced halo formation. However, the nonlinear damping is accompanied by emittance growth causing the beam to spread in phase space. As a result, inducing nonlinear damping alone cannot help mitigate the halo. To compensate for this expansion in phase space, the beam is collimated in the simulation and further evolution of the beam shows that the halo is not regenerated. The focusing model used in the PIC is analysed using the Lie Transform perturbation theory showing that by averaging over a lattice period, one can reuduce the focusing force to a form that is identical to that used in the PIC simulation.
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| ROPB010 | Self-Consistent Electron-Cloud Simulation for Long Proton Bunches | proton, electron, lattice, dipole | 722 | ||
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge. |
The results of numerical electron-cloud simulations for long-bunch proton beams in accumulator rings are presented and compared with data from the Proton Storage Ring at LANL. The frequency spectra and growth rate of proton-bunch transverse instabilities are studied as functions of the RF cavity voltage, external magnetic fields, beam pipe surface properties, and other factors. We used the recently developed electron-cloud module in the ORBIT code. The model includes a fully self-consistent coupled treatment of the "proton bunch – electron-cloud" dynamics and the multipacting process with a realistic secondary emission surface model. Realistic lattices and proton bunch distributions are used. The efficiency of electron-cloud instability suppression has also been studied using a new ORBIT model. |
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| RPPE006 | Air Temperature Analysis and Control Improvement for the Storage Ring Tunnel | storage-ring, synchrotron, synchrotron-radiation, lattice | 1027 | ||
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The stability of the electron beam orbit had been observed to be sensitive to the utility conditions. The stability of air temperature in the storage ring tunnel is one of the most critical factors. Accordingly, a series of air conditioning system upgrade studies and projects have been conducted at the Taiwan Light Source (TLS). Computational fluid dynamics (CFD) is applied to simulate the flow field and the spatial temperature distribution in the storage ring tunnel. The circumference and the height of the storage tunnel are 120m and 2.8m, respectively. The temperature data and the flow rates at different locations around the storage ring tunnel are collected as the boundary conditions. The k-epsilon turbulence model is applied to simulate the flow field in the three dimensional space. The global air temperature variation related to time in the storage ring tunnel is currently controlled within ±0.1 degree C. However, the temperature difference between two different locations is as high as 2 degree C. Some measures improving the temperature uniformity will be taken according to the CFD simulation results.
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| RPPE009 | Extremely High Current, High-Brightness Energy Recovery Linac | electron, gun, linac, emittance | 1150 | ||
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Funding: Under contract with the U.S. Department of Energy, U.S. DOD Office of Naval Research and Joint Technology Office. |
Next generation ERL light-sources, high-energy electron coolers, high-power Free-Electron Lasers, powerful Compton X-ray sources and many other accelerators were made possible by the emerging technology of high-power, high-brightness electron beams. In order to get the anticipated performance level of ampere-class currents, many technological barriers are yet to be broken. BNL’s Collider-Accelerator Department is pursuing some of these technologies for its electron cooling of RHIC application, as well as a possible future electron-hadron collider. We will describe work on CW, high-current and high-brightness electron beams. This will include a description of a superconducting, laser-photocathode RF gun and an accelerator cavity capable of producing low emittance (about 1 micron rms normalized) one nano-Coulomb bunches at currents of the order of one ampere average. |
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| RPPE014 | Temperature Regulation of the Accelerating Section in CANDLE Linac | feedback, linac, resonance, radio-frequency | 1416 | ||
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The temperature of the CANDLE S-Band Linac high-power RF components will be regulated by stand-alone closed loop (SACL) water system. The RF components are made of oxygen-free high conductivity copper and respond quickly to temperature changes. Temperature stabilization better than ± 0.1 C is required to achieve a good RF phase and energy stability. The temperature regulation and control philosophy along with the simulation results are discussed.
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| RPPE016 | Protection Level During Extraction, Transfer and Injection into the LHC | injection, extraction, septum, kicker | 1505 | ||
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Failures during the LHC transfer and injection process cannot be excluded and beam loss with the foreseen intensities and energies, which are an order of magnitude above the damage limit, could cause serious equipment damage. Consequences of equipment failures such as kicker erratics, power converter faults, etc. are investigated by means of a Monte Carlo based on MAD-X tracking with a full aperture model of the transfer line and the injection region. Geometrical and optical mismatch, orbit tolerances, mechanical tolerances for settings of protection elements, power converter ripples, misalignment of elements, etc. are all taken into account. The required performance of the protection system is discussed. The overall protection level for the LHC and the transfer lines during injection is presented.
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| RPPE018 | Material Damage Test with 450 GeV LHC-Type Beam | target, proton, hadron, injection | 1607 | ||
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The design of LHC protection elements is based on assumptions on damage levels, which are derived from simulations. A dedicated experiment was prepared and carried out to cross-check the validity of this approach by trying to damage material in a controlled way with beam. The impact of a 450 GeV beam extracted from the SPS on a specially designed high-Z target with a simple geometry, comprising several typical materials used for LHC equipment, was simulated. The beam intensities for the test were chosen to exceed the damage limits of parts of the target. Results of the simulations are presented and compared with test results.
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| RPPE031 | Target and Horn Cooling for the Very Long Baseline Neutrino Experiment | target, proton, radiation, focusing | 2209 | ||
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Funding: This work is performed under the auspices of the US DOE. |
Thermodynamic studies have been performed for the beam target and focusing horn system to be used in a very long baseline neutrino oscillation experiment. A 2mm rms beam spot with power deposition of over 18 KW presents challenging material and engineering solutions to this project. Given that the amount of heat transferred by radiation alone from the target to the horn is quite small, the primary mechanism is heat removal by forced convection in the annular space between the target and the horn. The key elements are the operating temperature of the target, the temperature of the cooling fluid and the heat generation rate in the volume of the target that needs to be removed. These working parameters establish the mass flow rate and velocity of the coolant necessary to remove the generated heat. Several cooling options were explored using a carbon-carbon target and aluminum horn. Detailed analysis, trade studies and simulations were performed for cooling the horn and target with gaseous helium as well as water. |
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| RPPE043 | Ultrathin Polyimide-Stainless Steel Heater for Vacuum System Bake-Out | radiation, vacuum, insertion, synchrotron | 2744 | ||
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Space constraints in several normal conducting magnets of the LHC required the development of a dedicated permanent heater for vacuum chamber bake-out. The new heater consists of stainless steel bands inside layers of polyimide. The overall heater thickness is about 0.3 mm. The low magnetic permeability is suitable for applications in magnetic fields. The material combination allows for temperatures high enough to activate a NEG coating. Fabrication is performed in consecutive steps of tape wrapping. Automation makes high volume production at low costs possible. About 800 m of warm vacuum system of the long straight sections of the LHC will be equipped with the new heater. This paper covers experience gained at CERN from studies up to industrialization.
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| RPPE057 | Resistive Wall Wakefield in the LCLS Undulator | undulator, impedance, electron, resonance | 3390 | ||
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Funding: Work supported by the U.S. Department of Energy, contract DE-AC03-76SF00515. |
In the Linac Coherent Light Source (LCLS), a short, intense bunch (rms length 20 microns, bunch charge 1 nC) will pass through a small, long undulator beam pipe (radius 2.5 mm, length 130 m). The wakefields in the undulator, particularly the resistive wall wake of the beam pipe, will induce an energy variation along the bunch, a variation that needs to be kept to within a few times the Pierce parameter for all beam particles to continue to lase. Earlier calculations included the short-range resistive wall wake, but did not include the frequency dependence of conductivity (ac conductivity) of the beam pipe walls. We show that for copper and for the LCLS bunch structure, including the ac conductivity results in a very large effect. We show that the effect can be ameliorated by choosing aluminum and also by taking a flat, rather than round, beam pipe chamber (if the vertical aperture is fixed). The effect of the (high frequency) anomalous skin effect is also considered. |
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| RPPP005 | Simulation Study of a Dogbone Damping Ring | wiggler, space-charge, damping, emittance | 928 | ||
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Damping ring is one of the major issues in the future linear collider (ILC). We discuss the design of the dogbone damping ring and the performance that includes dynamic apertures, space charge effects, and optics corrections.
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| RPPP009 | Luminosity Tuning Bumps in the CLIC Main Linac | luminosity, emittance, linac, quadrupole | 1141 | ||
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Funding: We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" programme (CARE, contract number RII3-CT-2003-506395). |
Preservation of beam emittance in the CLIC main linac is a challenging task. This requires not only beam-based alignment of the beam line components but also the use of emittance tuning bumps. In this paper the potential use of luminosity tuning bumps is explored and compared to emittance tuning bumps. |
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| RPPP010 | Considerations on the Design of the Decelerator of the CLIC Test Facility (CTF3) | damping, linac, beam-losses, quadrupole | 1177 | ||
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Funding: We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" programme (CARE, contract number RII3-CT-2003-506395). |
One of the main aims of the CLIC Test Facility (CTF3) is to study the beam stability in the drive beam decelerator and to bench mark the performance against beam simulation codes. Particular challenges come from the large drive beam energy spread, the strong wakefields and potential beam losses. The development towards a decelerator design and the required instrumentation is described in this paper. |
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| RPPP014 | Multi-Bunch Simulations of the ILC for Luminosity Performance Studies | luminosity, feedback, ground-motion, linac | 1368 | ||
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Funding: This work is supported by the Commission of the European Communities under the 6th Framework Programme "Structuring the European Research Area", contract number RIDS-011899. |
To study the luminosity performance of the International Linear Collider (ILC) with different design parameters, a simulation was constructed that tracks a multi-bunch representation of the beam from the Damping Ring extraction through to the Interaction Point. The simulation code PLACET is used to simulate the LINAC, MatMerlin is used to track through the Beam Delivery System and GUINEA-PIG for the beam-beam interaction. Included in the simulation are ground motion and wakefield effects, intra-train fast feedback and luminosity-based feedback systems. To efficiently study multiple parameters/multiple seeds, the simulation is deployed on the Queen Mary High-Throughput computing cluster at Queen Mary, University of London, where 100 simultaneous simulation seeds can be run. |
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| RPPP015 | Reconstruction of IP Beam Parameters at the ILC from Beamstraahlung | photon, radiation, luminosity, electron | 1446 | ||
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Funding: This work is supported by the Commission of the European Communities under the 6th Framework Programme "Structuring the European Research Area", contract number RIDS-011899. |
The luminosity performance of the ILC will be very sensitive to the parameters of the colliding bunches. Only some of these parameters can be measured using planned instrumentation. This analysis aims to access some of the colliding beam parameters not available by other means and to improve on the resolution of those that are. GUINEA-PIG is used to simulate the beam-beam interactions and produce beamstrahlung radiation (e+/e- pairs and photons). These are tracked to a simulation of the low-angle Beam Calorimeter and a photon detector and event shapes are produced. A Taylor map is produced to transform from the event shapes to the simulated beam parameters. This paper reports on the progress of this analysis, examining the usefulness of the proposed fitting technique. |
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| RPPP026 | Linear Accelerator Simulations with BMAD | linac, emittance, lattice, longitudinal-dynamics | 1937 | ||
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Funding: Work supported by the U.S. DOE. |
BMAD is a subroutine library for simulating relativistic charged-particle dynamics. It has been used extensively as a diagnostic tool at the Cornell Electron Storage Ring (CESR). The BMAD libraries have recently been extended to include modeling of the dynamics of linear accelerators. Calculations of emittance dilution due to orbit offsets and misalignments have been compared with LIAR, Merlin and PLACET, and good agreement is found with both particle and macroparticle tracking through the NLC and Tesla lattices for the bunch compressor, main linac and final focus regions. |
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| RPPP028 | Simulation of Wake Field Effects on High Energy Particle Beams | collimation, linear-collider, collider, optics | 2018 | ||
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We discuss the wake fields that are liable to arise in the Beam Delivery System of a Future Linear Collider, and we present studies made using the MERLIN simulation program of the effects such fields would have on the bunch shape and hence the luminosity of the proposed design.
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| RPPP042 | Emittance Dilution Due to Dipole Mode Rotation and Coupling in the Main Linacs of the ILC | emittance, linac, coupling, dipole | 2723 | ||
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Funding: This work is supported by Department of Energy grant number DE-AC02-76SF00515. |
The progress of multiple bunches of charged particles down the main L-band linacs of the ILC (International Linear Collider) can be disrupted by wakefields. These wakefields correspond to the electromagnetic fields excited in the accelerating cavities and have both long-range and short-range components. Here we investigate the impact of the long-range wakefields on the trailing bunches caused by the leading bunches. In general, the dipole mode degeneracy will be removed both because of manufacturing errors and because the higher order mode couplers are dipole asymmetric and lie neither in the horizontal nor vertical plane. This creates 2 dipole eigenmodes which are rotated with respect to the horizontal and vertical axes and which may have slightly different frequencies. These eigenmodes can couple the horizontal and vertical dipole excitations. We simulate the progress of the ILC beam down the collider under the influence of these wakefields. In particular, we investigate the consequences on the final emittance dilution of the beam of coupling of the horizontal to the vertical motion of the beam. |
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| RPPP043 | Emittance Dilution Due to Many-Band Long-Range Dipole Wakefields in the International Linear Collider Main Linacs | emittance, linac, dipole, linear-collider | 2792 | ||
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Funding: This work is supported by Department of Energy grant number DE-AC02-76SF00515. |
We investigate the emittance dilution that occurs due to long range wakefields in the ILC L-band linacs. The largest kick factors (proportional to the transverse fields which transversely kick the beam off axis) from the first six bands are included in our simulations. These higher order dipole modes are damped by carefully orientating higher order mode couplers at both ends of each cavity. We investigate the dilution in the emittance of a beam with a random misalignment of cavities down the complete linac. In particular, the impact of a poorly damped dipole mode, on the overall emittance dilution down the complete linac is focused upon. The transverse alignment tolerances imposed on the cavities due to these wakefields are also discussed. |
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| RPPP045 | Single-Bunch Instability Driven by the Electron Cloud Effect in the Positron Damping Ring of the International Linear Collider | electron, dipole, single-bunch, damping | 2884 | ||
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Funding: Work supported by the U.S. DOE under contracts DE-AC02-76SF00515. |
With the recommendation that the future International Linear Collider (ILC) should be based on superconducting technology, there is considerable interest in exploring alternate designs for the damping rings (DR). The TESLA design was 17 km in circumference with a "dog-bone" configuration. Two other smaller designs have been proposed that are 6 km and 3 km in length. In the smaller rings, collective effects may impose the main limitations. In particular for the positron damping ring, an electron cloud may be produced by ionization of residual gas or photoelectrons and increase through the secondary emission process. The build-up and development of an electron cloud is more severe with the higher average beam current in the shorter designs. In this paper, we present recent computer simulation results for the electron cloud build-up and instability thresholds for the various DR configurations. |
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| RPPP046 | An L-Band Polarized Electron PWT Photoinjector for the International Linear Collider (ILC) | electron, cathode, vacuum, emittance | 2902 | ||
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Funding: Work supported by DOE SBIR Grant No. DE-FG02-03ER83846. |
A multi-cell, standing-wave, L-band, p-mode, plane-wave-transformer (PWT) photoinjector with an integrated photocathode in a novel linac structure is proposed by DULY Research Inc. as a polarized electron source. The PWT photoinjector is capable of operation in ultra high vacuum and moderate field gradient. Expected performance of an L-band polarized electron PWT injector operating under the parameters for the International Linear Collider is presented. The projected normalized transverse rms emittance is an order of magnitude lower than that produced with a polarized electron dc gun followed by subharmonic bunchers. |
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| RPPP053 | Simulations of Resistive-Wall Instability in the ILC Damping Rings | damping, feedback, pick-up, radiation | 3241 | ||
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Funding: Work supported by U.S. Department of Energy, Director, Office of Science, Contract No. DE-AC03-76SF00098. |
Options being considered for the ILC Damping Rings include lattices with circumferences up to 17 km. The circumference, beam current and beam energy place the damping rings in a regime where resistive-wall instability is a concern, particularly as there are very demanding tolerances on the bunch-to-bunch jitter. Generally, it is possible to make good analytical estimates of the coupled-bunch growth rates in a storage ring, but particular features of the damping rings (including the fill pattern, large variations of the lattice functions and beam-pipe cross-section in different parts of the ring, and transverse beam coupling in the long straight sections) make it desirable to study the coupled-bunch instabilities using simulations. Here, we present the results of simulations of the transverse instabilities using a detailed lattice model. A bunch-by-bunch feedback system will be needed to suppress the instabilities, and a model for an appropriate feedback system is included in the simulations. |
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| RPPT001 | The BESSY Soft X-Ray FEL User Facility | photon, electron, undulator, linac | 746 | ||
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Funding: Funded by Zukunftsfonds Berlin. |
The user requests for an optimized 2nd generation FEL facility in the VUV to soft X-ray range demand for ultra short photon pulses (t = 20 fs) at a peak power of several GW. A high shot to shot reproducibility of the pulse shape and pulse power allowing for fs-synchronization for pump-probe experiments is feasible in a seeded FEL approach. Free selectable photon polarization and wavelength tuning is essential for any 2nd generation FEL source like the proposed BESSY-Soft X-ray FEL user facility. Freely selectable pulse repetition rates and freely selectable pulse patterns, including fast switching to different parallel operating FEL-Lines are necessary ingredients, feasible with a suitable injector in combination with a CW-superconducting linac. The status of the BESSY HGHG-FEL project will be reviewed. |
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| RPPT002 | Harmonic Content of the BESSY FEL Radiation | radiation, undulator, bunching, electron | 829 | ||
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Funding: Funded by Zukunftsfonds Berlin. |
BESSY proposes a linac-based cascaded High-Gain Harmonic-Generation (HGHG) free electron laser (FEL) multi-user facility. The BESSY soft X-ray FEL will consist of three undulator lines. The associated tunable lasers will cover the spectral range of 230nm to 460nm. Two to four HGHG stages reduce the seed wavelength to the desired radiation range of 1.24nm < λ < 51nm. The harmonic content of the high-intensity radiator output can be used to reduce the number of necessary HGHG stages. Moreover the higher harmonic content of the final output extends the offered spectral range and thus is of high interest for the user community. In this paper, the higher harmonic content of the final output as well as of the output of several radiators are investigated. The main parameters such as output power, pulse duration and bandwidth as well as their suitability for seeding are discussed. |
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| RPPT005 | Establishing a Collaborative Planning Procedure for the XFEL | site, civil-engineering | 961 | ||
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Building a new accelerator requires a consistent common design of the entire complex, including machine, tunnels, buildings and infrastructure. The efforts involve experts from many disciplines. Complication arises as different expert groups are contributing at different project phases: buildings and technical infrastructure are constructed first, thus their design has to be fixed early in the project and is then imposing constraints e.g. on the machine layout while accelerator R&D is still being continued. In view of these challenges, a dedicated planning and design procedure has to be established which provides “just-enough” details where needed while preserving maximum flexibility for other subsystems, and which can also manage later changes if they become necessary. The poster presents experience from planning the XFEL. Expert groups can create and maintain separate design models of their components, which at the same time can be combined into a common overall design model. The planning procedure relies on commercial tools used in industry (specification database, engineering data management and 3D CAD systems) which are being adapted to the culture and organization of HEP collaborations.
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| RPPT006 | Commissioning of TTF2 Bunch Compressor for the Femtosecond (FS) FEL Mode Operation | emittance, linac, gun, single-bunch | 991 | ||
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Funding: For the TESLA Test Facility FEL team. |
To get lasing at TTF2, we should supply high quality electron beams with a high peak current, a low slice emittance, and a low slice energy spread. To supply a high peak current, we compress bunch length with two bunch compressors. During TTF2 lasing period, there was no available special bunch length diagnostic tool such as LOLA cavity or streak camera. However we could optimize TTF2 bunch compressors by monitoring pyro-electric detector signal, by measuring emittance, and by monitoring beam images at chicane center and dump region, and by comparing operational machine conditions with simulation results. In this paper, we describe our various commissioning experiences of TTF2 bunch compressor to generate a femtosecond-long spike with a high peak current. |
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| RPPT015 | Start To End Simulation for the SPARX Project | linac, emittance, brightness, undulator | 1455 | ||
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The first phase of the SPARX project now funded by Government Agencies, is an R&D activity focused on developing techniques and critical components for future X-ray facilities. The aim is the generation of electron beams with the ultra-high peak brightness required to drive FEL experiments. The FEL source realization will develop along two lines: (a) the use of the SPARC high brightness photoinjector to test RF compression techniques and the emittance degradation in magnetic compressors due to CSR, (b) the production of radiation in the range of 3-5 nm, both in SASE and SEEDED FEL configurations, in the so called SPARXINO test facility, upgrading the existing Frascati 800 MeV LINAC. In this paper we present and discuss the preliminary start to end simulations results.
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| RPPT019 | Start to End Simulations of the ERL Prototype at Daresbury Laboratory | linac, electron, wiggler, booster | 1643 | ||
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Daresbury Laboratory is currently building an Energy Recovery Linac Prototype (ERLP) that will serve as a research and development facility for the study of beam dynamics and accelerator technology important to the design and construction of the proposed 4th Generation Light Source (4GLS) project. Two major objectives of the ERLP are the demonstration of energy recovery and of energy recovery from a beam disrupted by an FEL interaction as supplied by an infrared oscillator system. In this paper we present start-to-end simulations of the ERLP including such an FEL interaction. The beam dynamics in the high-brightness injector, which consists of a DC photocathode gun and a superconducting booster, have been modelled using the particle tracking code ASTRA. After the booster the particles have been tracked with the code GPT which includes space charge in the injector line at 8.3 MeV. The 3D code GENESIS 1.3 was used to model the FEL interaction with the electron beam at 35 MeV.
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| RPPT028 | Free Electron Lasers with Slowly Varying Beam and Undulator Parameters | undulator, electron, vacuum, radiation | 2059 | ||
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The performance of a free electron lasers (FEL) is affected when the electron beam energy varies alone the undulator as would be caused by vacuum pipe wakefields and/or when the undulator strength parameter is tapered in the small signal regime until FEL saturation. In this paper, we present a self-consistent theory of FELs with slowly-varying beam and undulator parameters. A general method is developed to apply the WKB approximation to the beam-radiation system by employing the adjoint eigenvector that is orthogonal to the eigenfunctions of the coupled Maxwell-Vlasov equations. This method may be useful for other slowly varying processes in beam dynamics.
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| RPPT031 | Recent Results from and Future Plans for the VISA II SASE FEL | radiation, electron, diagnostics, undulator | 2167 | ||
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As the promise of X-ray Free Electron Lasers (FEL) comes close to realization, the creation and diagnosis of ultra-short pulses is of great relevance in the SASE FEL (Self-Amplified Spontaneous Emission) community. The VISA II (Visible to Infrared SASE Amplifier) experiment entails the use of a chirped electron beam to drive a high gain SASE FEL at the Accelerator Test Facility (ATF) in Brookhaven National Labs (BNL). The resulting ultra-short pulses will be diagnosed using an advanced FROG (Frequency Resolved Optical Gating) technique, as well as a double differential spectrum (angle/wavelength) diagnostic. Implementation of sextupole corrections to the longitudinal aberrations affecting the high energy-spread chirped beam during transport to the VISA undulator is studied. Start-to-end simulations, including radiation diagnostics, are discussed. Initial experimental results involving a highly chirped beam transported without sextupole correction, the resulting high gain lasing, and computational analysis are briefly reported.
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| RPPT034 | High-Resolution Undulator Measurements using Angle-Integrated Sponteneous Radiation | undulator, electron, photon, radiation | 2342 | ||
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Funding: Work supported by U. S. Department of Energy, Office of Basic Energy Sciences under Contract No. W-31-109-ENG-38. |
The Linac Coherent Light Source (LCLS) is a fourth-generation light. Its proper operation requires a stringently controlled undulator field. The tolerance for the field parameter K is less than 1.5 × 10-4 for all thirty-three undulator segments totaling 112 meters. Even with the high quality of the LCLS electron beam (x- and y-emittance ~ 44 pm, energy spread ~0.03%), the fluctuation of the electron energy (~0.05%) presents a serious challenge to measurement techniques based on electron or x-ray beams. We propose a differential measurement technique that makes use of the angle-integrated spontaneous radiation intensities from two undulator segments. When the x-ray beams emitted from the two undulator segments are separated but allowed to pass through the same monochromator, the two beam intensities will change almost identically with the change of electron beam energy. As a result, the intensity difference becomes a very sensitive and reliable measure of the difference of the two undulators’ K-parameters. Results of comprehensive numerical simulations show that differences in the range of delta-K/K ~ 10-5 can be resolved, well within the tolerance for the LCLS operation. |
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| RPPT035 | Optimization of the LCLS X-Rray FEL Output Performance in the Presence of Strong Undulator Wakefields | undulator, electron, vacuum, radiation | 2396 | ||
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Funding: The work was supported by the DOE Contract No. DE-AC02-76SF00515. |
The Linac Coherent Light Source (LCLS) Free-Electron Laser will operate in the wavelength range of 1.5 to 15 Angstroms. Energy loss due to wakefields within the long undulator can degrade the FEL process by detuning the resonant FEL frequency. The wakefields arise from the vacuum chamber wall resistivity, its surface roughness, and abrupt changes in its aperture. For LCLS parameters, the resistive component is the most critical and depends upon the chamber material (e.g. Cu) and its radius. To study the expected performance in the presence of these wakefields, we make a series of "start-to-end" simulations with tracking codes PARMELA and ELEGANT and time-dependent FEL simulation codes Genesis 1.3 and Ginger. We discuss the impact of the wakefield on output energy, spectral bandwidth, and temporal envelope of the output FEL pulse, as well as the benefits of a partial compensation obtained with a slight z dependent taper in the undulator field. We compare these results to those obtained by decreasing the bunch charge or increasing the vacuum chamber radius. We also compare our results to those predicted in concurrent analytical work. |
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| RPPT045 | A Method to Calibrate Beam Position Monitor at HLS 200 MeV LINAC | linac, pick-up, impedance, injection | 2896 | ||
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In order to improve injection efficiency of HLS 200Mev LINAC, we redesign a new strip line beam position monitor system, which is consisted of a strip line structure and a signal processing system. We decide on an online calibration method based on beam to find out the geometry centre displacement and relative gain offset. Before the BPM testing bench has been prepared, we make a simulation based on the model accounted for all factors influencing signal amplitudes and get the calibrating results. At last, we analyze the nonlinearity effect on the calibration results.
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| RPPT047 | Development of Measurement and Transverse Feedback System at HLS | feedback, single-bunch, storage-ring, pick-up | 2974 | ||
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In order to observe and cure coupled bunch (CB) instabilities caused by the high order modes (HOMs) of the RF cavity and the resistive wall impedance of the Ring vacuum chamber, which were ineluctable during the operation of the accelerator, an observer system characterized by bunch by bunch measurement of transverse ßoscillation and longitudinal synchrotron phase oscillation has been constructed and commissioned at Hefei Light Source (HLS); meanwhile a transverse bunch-by-bunch feedback system is under construction. The design and development of the systems, as well as diagnostics results of machine instabilities will be presented in this paper.
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| RPPT059 | Spectrum from the Proposed BNL Very Long Baseline Neutrino Facility | target, proton, alignment, background | 3476 | ||
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Funding: The work was performed with the support of the U.S. DOE under Contract No. DE-AC02-98CH10886. |
This paper calculates the neutrino flux that would be seen at the far detector location from the proposed BNL Very Long Baseline Neutrino Facility. The far detector is assumed to be located at an underground facility in South Dakota 2540 km from BNL. The neutrino beam facility uses a 1 MW upgraded AGS to provide an intense proton beam on the target and a magnetic horn to focus the secondary pion beam. The paper will examine the sensitivity of the neutrino flux at the far detector to the positioning of the horn and target so as to establish alignment tolerances for the neutrino system. |
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| RPPT061 | Linear Quadrupole Cooling Channel for a Neutrino Factory | quadrupole, emittance, factory, acceleration | 3526 | ||
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Funding: Work supported by the U.S. Dept. of Energy under contract no. DE-AC02-76CH03000. |
The staging and optimization in the design of a Neutrino Factory are critically dependent on the choice and format of accelerator. Possibly the simplest, lowest-cost scenario is a nonscaling FFAG machine coupled to a linear (no bending) transverse cooling channel constructed from the simplest quadrupole lens system, a FODO cell. In such a scenario, transverse cooling demands are reduced by a factor of 4 and no longitudinal cooling is required relative to acceleration using a Recirculating Linac (RLA). Detailed simulations further show that a quadrupole-based channel cools efficiently and over a momentum range which is well-matched to FFAG acceleration. Details and cooling performance for a quadrupole channel are summarized in this work. |
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| RPPT062 | Radiation Simulations for the Proposed ISOL Stations for RIA | target, shielding, radiation, ion | 3561 | ||
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Funding: This work is supported in part by Michigan State University, the U.S. Department of Energy, and the National Research Council of Canada. |
The Department of Energy's Office of Nuclear Physics, within the Office of Science (SC), has given high priority to consider and analyze design concepts for the target areas for the production of rare isotopes via the ISOL technique at the Rare-Isotope Accelerator (RIA) Facility. Key criteria are the maximum primary beam power of 400 kW, minimizing target change-out time, good radiological protection, flexibility with respect to implementing new target concepts, and the analysis and minimization of hazards associated with the operation of the facility. We will present examples of on-going work on simulations of radiation heating of targets, surrounding components and shielding, component activation, and levels of radiation dose, using the simulation codes MARS, MCNPX, and PHITS. These results are important to make decisions that may have a major impact on the layout, operational efficiency and cost of the facility, hazard analysis, shielding design, civil construction, component design, and material selection, overall layout, and remote handling concepts. |
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| RPPT063 | Radiation Simulations and Development of Concepts for High Power Beam Dumps, Catchers and Pre-separator Area Layouts for the Fragment Separators for RIA | radiation, target, quadrupole, ion | 3594 | ||
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Funding: This work is supported in part by Michigan State University, the US DOE, and the Gesellschaft für Schwerionenforschung, Germany. |
The development of high-power beam dumps and catchers, and pre-separator layouts for proposed fragment separators of the Rare-Isotope Accelerator (RIA) facility are important in realizing how to handle the 400 kW in the primary beam. We will present examples of pre-conceptual designs of beam dumps, fragment catchers, and the pre-separator layout. We will also present examples of ongoing work on radiation simulations using the heavy-ion-transport code PHITS, characterizing the secondary radiation produced by the high-power ion beams interacting with these devices. Results on radiation heating of targets, magnet coils, associated hardware and shielding, component activation, and levels of radiation dose will be presented. These initial studies will yield insight into the impact of the high-power dissipation on fragment separator design, remote handling concepts, nuclear safety and potential facility hazard classification, shielding design, civil construction design, component design, and material choices. Furthermore, they will provide guidance on detailed radiation analyses as designs mature. |
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| RPPT068 | Pion-Muon Concentrating System for Detectors of Highly Enriched Uranium | target, antiproton, focusing, shielding | 3757 | ||
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One of many possible applications of low-energy antiprotons collected in a Penning trap can be a portable muon source. Released antiprotons annihilate on impact with normal matter producing on average about 3 charged pions per antiproton, which in turn decay into muons. Existence of such negative-muon sources of sufficient intensity would bring into play, for example, detectors of highly enriched uranium based on muonic X-rays. We explore options of collecting and focusing pions and resulting muons to enhance the muon flux toward the detector. Simulations with MARS and MAFIA are used to choose the target material and parameters of the magnetic system consisting of a few solenoids.
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| ROPA006 | Terascale Beam-Beam Simulations for Tevatron, RHIC and LHC | emittance, antiproton, proton, injection | 535 | ||
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Funding: This work was supported by a SciDAC project in accelerator physics which is supported by the US DOE/SC Office of High Energy Physics and the Office of Advanced Scientific Computing Research. |
In this paper, we report on recent advances in terascale simulations of the beam-beam effects in Tevatron, RHIC and LHC. Computational methods for self-consistent calculation of the beam-beam forces are reviewed. Applications to the studies of the multiple bunch beam-beam interactions in the Tevatron and the RHIC will be presented. The study of emittance growth due to the beam-beam interactions in the LHC will also be presented. |
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| ROPA007 | Vlasov Simulations of Beams and Halo | focusing, lattice, hadron, brightness | 581 | ||
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Even though PIC simulations have proven an efficient tool for beam simulations for many years, they are subject to numerical noise which only decreases slowly when the number of particles is increased. Therefore other methods might be preferable, when one is interested in accurate simulations of high intensity beams especially in the low density part of phase space. We have been developing new methods based on the direct resolution of the Vlasov equation on a grid of phase space. In order for these methods to be efficient special care needs to be taken to optimize the number of necessary grid points. We shall describe two different approaches that are used to this aim: moving grid methods and wavelet based automatic grid refinement. Beam simulations in different configurations using direct Vlasov methods will be presented.
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| ROPC006 | Commissioning of Fermilab's Electron Cooling System for 8-GeV Antiprotons | electron, antiproton, vacuum, beam-losses | 540 | ||
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A 4.3-MeV electron cooling system has been installed at Fermilab in the Recycler antiproton storage ring and is being currently commissioned. The cooling system is designed to assist accumulation of 8.9-GeV/c antiprotons for the Tevatron collider operations. This paper will report on the progress of the electron beam commissioning effort as well as on detailed plans of demonstrating the cooling of antiprotons.
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| ROPC009 | First Acceleration with Superconducting RF Cavities at ISAC-II | acceleration, diagnostics, ion, vacuum | 662 | ||
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We have demonstrated the first acceleration of ions with superconducting rf at TRIUMF/ISAC. Alpha particles from a radioactive source were accelerated from 2.8MeV through the ISAC-II medium beta cryomodule to a maximum energy of 9.4 MeV. The four 106 MHz quarter wave cavities (beta_o=7%) were set to the ISAC-II specified gradient of 6 MV/m (Leff=18cm, Ep=30MV/m and Veff=1.08MV) with a cavity power of about 6W per cavity. The final particle energy spectra was measured with a silicon detector. The initial alpha energy corresponds to a velocity of beta=3.9% giving an expected T/To efficiency of 0.48, 0.76, 0.92 and 0.99 for the four cavities respectively and an expected final energy of 9.6MeV. The experimental set-up including details of the source and diagnostic boxes and the detector electronics are described. Beam simulations of the unbunched, uncollimated beam indicate a unique spectral fingerprint that can be used to unambiguously determine each cavity voltage.
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| FOAC001 | High Intensity Muon Beam Facilities with FFAG | betatron, proton, luminosity, factory | 29 | ||
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A new highly intense muon source with narrow beam energy spread and high purity, based on a FFAG ring, is under development in Japan. It is called the PRISM project, which stands for Phase Rotated Intense Slow Muon source. The aimed beam intensity is about 1011-1012 muons per year, which is about 1000 or 1000 times that presently available. The muon beam energy is low, of 20 MeV in kinetic energy, for stopped muon experiments. In particular, high luminosity would be important, and narrow beam spread can be achieved by phase (bunch) rotation in the FFAG ring. It is expected to compress the beam energy spread from about 30% down to about 3 %. At Osaka university, the PRISM-FFAG ring is now under construction. The special requirements for the PRISM-FFAG ring, compared to other FFAG rings so far developed, is to have large acceptance dedicated for a muon beam, and high-gradient RF to complete phase rotation within a muon lifetime. In this presentation the present designs of PRISM and status of construction will be presented.
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| FOAC002 | Status of Neutrino Factory Design and R&D | factory, target, proton, collider | 209 | ||
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Funding: Work supported by the US Department of Energy under contract No. DE-AC0376SF00098 |
Neutrino physics has become increasingly interesting to the high-energy physics community, as it may provide clues to new physics beyond the standard model. The physics potential of a Neutrino Factory–a facility to produce high-energy, high-intensity, high-brightness neutrino beams from decays of muons stored in a muon storage ring–is thus very high. There has been a global R&D effort aimed at a Neutrino Factory design that meets the physics requirements and addresses the key technologies, such as targetry, muon ionization cooling and acceleration. Tremendous progress has been made in the past few years in many aspects of accelerator technology. In this paper, we will review recent worldwide progress toward a cost-effective Neutrino Factory design, with emphasis on the associated R&D programs under the auspices of the U.S. Neutrino Factory and Muon Collider Collaboration. |
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| FOAC005 | Reliability and Availability Studies in the RIA Linac Driver | linac, controls, site, power-supply | 443 | ||
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Funding: Work supported by the U. S. Department of Energy under contract W-31-109-ENG-38. |
The RIA facility will include various complex systems and must provide radioactive beams to many users simultaneously. The availability of radioactive beams for most experiments at the fully-commissioned facility should be as high as possible within design cost limitations. To make a realistic estimate of the achievable reliability a detailed analysis is required. The RIA driver linac is a complex machine containing a large number of SC resonators and capable of accelerating multiple-charge-state beams. At the pre-CDR stage of the design it is essential to identify critical facility subsystem failures that can prevent the driver linac from operating. The reliability and availability of the driver linac are studied using expert information and data from operating machines such as ATLAS, APS, JLab, and LANL. Availability studies are performed with a Monte-Carlo simulation code previously applied to availability assessments of the NLC facility [http://www.slac.stanford.edu/xorg/accelops/Full/LCoptsfull] and the results used to identify subsystem failures that affect most the availability and reliability of the RIA driver, and guide design iterations and component specifications to address identified problems. *J.A. Nolen, Nucl. Phys. A. 734 (2004) 661. |
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| FPAE004 | Optical Matching of Slowly Extracted Beam with Transport System at HIMAC | extraction, emittance, optics, heavy-ion | 910 | ||
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The optical matching between the ring and the transport line plays important role in order to control the beam size and profile after the transport. At HIMAC, thus, we have studied the optical matching of the slowly extracted beam. As a result, it was verified that the beam size of the slowly extracted beam were controlled owing to the optical matching. It was also found that small deviation of quadrupole strength in the ring brings orbit distortion at the transport system.
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| FPAE005 | Characteristics of Injected Beam at HIMAC Synchrotron | injection, resonance, survey, synchrotron | 952 | ||
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At the HIMAC synchrotron, we have carried out the tune survey with the lifetime measurement in order to obtain the high intensity. Under the relatively high intensity, it was observed that a part of the circulating beam was lost due to the coherent oscillation in both the horizontal and the vertical direction. Taking account of the tune shift and spreads, the working point was optimized so as to avoid resonance line. We will describe the experimental result.
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| FPAE006 | Optimization of AGS Polarized Proton Operation with the Warm Helical Snake | proton, extraction, resonance, dipole | 1003 | ||
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Funding: US DOE and RIKEN Japan. |
A normal conducting helical dipole partial Siberian snake (Warm Snake) has been installed in the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory (BNL) for overcoming all of imperfection depolarizing resonances and reducing the transverse coupling resonances caused by the solenoidal Siberian snake which had been operated in AGS before the last polarized run. The polarized proton beam has been accelerated successfully with the warm snake and the polarization at extraction of the AGS was increased to 50% as opposed to 40% with the solenoidal snake. The magnetic field and beam trajectory in the warm snake was calculated by using the OPERA-3D/TOSCA software. We present optimization of the warm snake with beam during RUN5. |
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| FPAE008 | Iso-Adiabatic Merging of pbar Stacks in the Recycler | emittance, antiproton, collider, hadron | 1093 | ||
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Funding: Work supported by the Universities Research Association, Inc., under contract DE-AC02-76CH03000 with the U.S. Department of Energy. |
Here, I have proposed an efficient scheme to merge two stacks of pbars in the Recycler* with emittance dilution <15%. First I discuss a method to match energy spreads of the two stacks and subsequently merging them. The scheme is illustrated with multiparticle dynamics simulations and beam measurements in the Recycler. *G. Jackson, Fermilab-TM-1991, November, 1996. |
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| FPAE023 | Direct Antiproton Deceleration in the Fermilab Proton Driver | antiproton, proton, synchrotron, H-minus | 1817 | ||
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The Fermilab Proton Driver is an 8 GeV kinetic energy H- linear accelerator proposed as a new source of high brightness protons for the Main Injector. The Recycler ring is an 8 GeV antiproton storage ring that resides in the same tunnel as the Main Injector. This paper describes a scenario wherein the current Main Injector proton injection kickers and Lambertson magnet are moved vertically into the Recycler ring to enable antiproton extraction toward the Proton Driver. By employing a pair of intermediate vertical bends at the appropriate vertical betatron phase advance, the vertical dispersion into the Proton Driver can be eliminated and direct antiproton deceleration made possible. Because the H- and antiproton beams have the same charge but opposite direction, matching of the Recycler lattice to the Proton Driver is required to accommodate the reversed effect of the focusing and defocusing quadrupoles.
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| FPAE035 | Steps Towards a 3 mA, 1.8 MW Proton Beam at the PSI Cyclotron Facility | cyclotron, target, injection, space-charge | 2405 | ||
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The PSI Cyclotron Facility produces routinely a 1.8-1.9 mA proton beam at 590 MeV. The beam power reaches 1.1 MW at the the pion production targets and 0.7 MW at the neutron spallation target SINQ. The accelerator complex will be analysed in respect to his potential for future improvements. The ongoing developments aiming to increase the beam intensity to 3 mA and hence the beam power to 1.8 MW will be discussed. Smooth extrapolations of the observed machine parameters as well as recent advances in the theoretical treatment of space charge dominated beams show that this goal can be achieved with available technologies. IA new RF-cavity operated at a voltage in excess of 1 MV has been successfully tested and installed in the Ring Cyclotron. Bunchers for the low energy and the medium energy transfer lines are in the design phase. A conceptual study of new accelerating cavities to replace the obsolete flattop-cavities of the Injector Cyclotron has been performed. While the upgrade of the Ring Cyclotron with four new cavities will be completed in 2008, it is still an open question whether this accelerator will be operated in the "round beam" mode like the Injector Cyclotron or with an upgraded flattopping system.
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| FPAE036 | Lattice Modification of a 1.2 GeV STB Ring for Generation of High Energy Gamma-Rays Using Internal Target Wire | electron, target, lattice, scattering | 2458 | ||
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A 1.2 GeV Stretcher-Booster Ring (STB ring) has been routinely operated at Laboratory of Nuclear Science (LNS), Tohoku University. The STB ring has functions of a pulse-beam stretcher and a booster-storage ring. In the booster-storage operation, high energy gamma-ray beam generated via bremsstrahlung from internal target wire is utilized for experiments of nuclear physics. Some fractions of circulating electrons are also deflected in the target wire due to Coulomb scattering without significant loss of the energy. The scattered electrons that are not getting out of the dynamic aperture once can circulate in the ring. Such electrons, however, would hit the chamber walls and supports of the target wire during further turns, because they have very large betatron amplitude. Consequently the Coulomb scattered electrons must be a source of significant background and may cause a degradation of gamma-ray beam quality. The quality of the gamma-ray beam has been improved by modifying the lattice functions of the ring, and we report the improvement in this conference.
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| FPAE042 | Beam Commissioning of the Superconducting RFQs of the New LNL Injector PIAVE | rfq, ion, linac, emittance | 2696 | ||
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PIAVE is the new injector of the LNL superconducting heavy ion linac ALPI; the injector is able to accelerate ions up to U (Q/q=8.5) with a final energy of more than 1 MeV/u. During the last two months of 2004 the superconducting RFQ, composed by two Nb structures operating at 80 MHz, has been commissioned using the O+3 and Xe+18 beams produced by the ECRIS ALICE. The beam has been accelerated up to 587 keV/u reaching the main design parameters (energy, longitudinal and transverse emittance, transmission) and demonstrating a stable and reproducible operation. This is the first operational beam accelerated by a superconducting RFQ.
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| FPAE049 | Development and Implementation of ?T Procedure for the SNS Linac | linac, SNS, monitoring, beam-loading | 3064 | ||
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. |
The ?t procedure is a time of flight technique for setting the phases and amplitudes of accelerating fields in a multi-cavity linac. It was initially proposed and developed for the LAMPF linac in the early seventies and since then has been used in several accelerators. The SNS linac includes four CCL modules (Side Coupled Structure) operating at 805 MHz for the energy range from 86.8 MeV up to 185.6 MeV. The ?t procedure has been implemented for the SNS CCL linac and was used for its initial beam commissioning. Brief theory of the procedure, the results of the design parameter calculations and the experimental results of phase and amplitude setpoints are presented and discussed. |
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| FPAE056 | Review of a Spoke-Cavity Design Option for the RIA Driver Linac | linac, beam-losses, proton, acceleration | 3360 | ||
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Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. W-31-109-ENG-38. |
A design option for the 1.4 GV, multiple-charge-state driver linac required for the U.S. Rare Isotope Accelerator Project based on 345 MHz, 3-cell spoke-loaded cavities has been previously discussed.* This paper updates consideration of design options for the RIA driver, including recent results from numerically-modeling the multi-charge-state beam dynamics and also cold test results for prototype superconducting niobium 3-cell spoke-loaded cavities. *"High-energy ion linacs based on superconducting spoke cavities," K.W. Shepard, P.N. Ostroumov, and J.R. Delayen, Phys. Rev. ST Accel. Beams 6, 080101 (2003). |
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| FPAE057 | Beam Dynamics Studies and Beam Quality in the SNS Normal-Conducting Linac | emittance, linac, ion-source, ion | 3381 | ||
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos and Oak Ridge. |
The Spallation Neutron Source accelerator systems will provide a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron production. The accelerator complex consists of an H- injector capable of producing 38 mA peak current, a 1 GeV linear accelerator, an accumulator ring and associated transport lines. The linear accelerator consists of a Drift Tube Linac, a Coupled-Cavity Linac and a Superconducting Linac which provide 1.5 mA average current to the accumulator ring. The staged beam commissioning of the accelerator complex is proceeding as component installation progresses. Recently, the normal-conducting linear accelerator was beam commissioned. A number of beam dynamics and beam quality measurements will be reported, including the measurement of transverse emittances in the H- injector, and the evolution of halo and emittance along the linac. |
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| FPAE058 | Spallation Neutron Source Superconducting Linac Commissioning Algorithms | linac, SNS, Spallation-Neutron-Source, resonance | 3423 | ||
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos and Oak Ridge. |
We describe the techniques which will be employed for establishing RF and quadrupole setpoints in the SNS superconducting linac. The longitudinal tuneup will be accomplished using phase-scan methods, as well as a technique that makes use of the beam induced field in the unpowered cavity.* The scheme for managing the RF and quadrupole setpoints to achieve a given energy profile will be described. *L. Young, Proc. PAC 2001, p. 572. |
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| FPAE062 | Beam Parameters of a Two-Sectional Electron Linac with the Injector Based on a Resonance System with Evanescent Oscillations | linac, emittance, electron, resonance | 3567 | ||
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The S-band electron linac has been designed at NSC KIPT to cover an energy range from 30 to about of 100 MeV. The linac consists of a couple of the four-meter long piecewise homogeneous accelerating sections. Each section is supplied with RF power from a separate klystron. The peculiarity of the linac is using of the injector based on evanescent oscillations. The report presents both simulation results of self-consistent particle dynamics in the linac and results of measurement of beam parameters.
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| FPAE066 | The IFUSP Microtron New Configuration | microtron, booster, injection, extraction | 3703 | ||
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Funding: Fundacao de Amparo a Pesquisa do Estado de Sao Paulo - FAPESP Conselho Nacional de Desenvolvimento Cientifico e Tecnologico - CNPq. |
In this work we present a new design for the IFUSP main microtron accelerator. The new configuration improves the maximum output energy and eases the operation of the machine. The accelerator will be able to deliver 38 MeV after 43 turns. The input energy was reduced from 4.9 to 2.5 MeV, so that the first microtron stage, the booster, could be eliminated, reducing the number of synchronous stages and easing the operation. We present results for the energy, energy gain and phase slip per turn, and the beam ellipses. We also discuss the design of the insertion and extraction lines. |
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| FPAE071 | Initial Results on Neutralized Drift Compression Experiments (NDCX-IA) for High Intensity Ion Beam | plasma, ion, diagnostics, induction | 3856 | ||
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Funding: This work was supported by the Director, Office of Science, Office of Fusion Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. |
Ion beam neutralization and compression experiments are designed to determine the feasibility of using compressed high intensity ion beams for high energy density physics (HEDP) experiments and for inertial fusion power. To quantitatively ascertain the various mechanisms and methods for beam compression, the Neutralized Drift Compression Experiment (NDCX) facility is being constructed at Lawrence Berkeley National Laboratory (LBNL). In the first compression experiment, a 260 KeV, 25 mA, K+ ion beam of centimeters size is radially compressed to a mm size spot by neutralization in a meter-long plasma column and beam peak current is longitudinally compressed by an induction velocity tilt core. Instrumentation, preliminary results of the experiments, and practical limits of compression are presented. These include parameters such as emittance, degree of neutralization, velocity tilt time profile, and accuracy of measurements (fast and spatially high resolution diagnostic) are discussed. |
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| FPAE075 | Radiation Damage to the Elements of the SIS300 Dipoles | ion, dipole, extraction, radiation | 3943 | ||
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Funding: Supported by the grant of the GSI-INTAS Project #03-54-3588. |
Radiation damage to various elements of the cosine-theta type dipoles of the SIS300 synchrotron of the FAIR Project was calculated. Among the elements under consideration were the superconducting cable, insulating materials, and high-current by-pass protection diodes. The Monte-Carlo particle transport codes MARS and SHIELD were used to simulate propagation of the lost ions and protons, together with the products of nuclear interactions in the material of the elements. It was found that the lifetime of the protection diodes under irradiation is a more restrictive limit for the tolerable level of beam losses than the occurrence of magnet quenches. |
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| FPAE077 | LSP Simulations of the Neutralized Drift Compression Experiment | ion, focusing, plasma, emittance | 4006 | ||
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Funding: Work supported by the VNL for HIF through PPPL and LBNL. |
The Neutralized Drift Compression Experiment (NDCX) at Lawrence Berkeley National Laboratory involves the longitudinal compression of a singly-stripped K ion beam with a mean energy of 250 keV in a meter long plasma. We present simulation results of compression of the NDCX beam using the PIC code LSP. The NDCX beam encounters an acceleration gap with a time-dependent voltage that decelerates the front and accelerates the tail of a 500 ns pulse which is to be compressed 110 cm downstream. The simulations model both ideal and experimental voltage waveforms. Results show good longitudinal compression without significant emittance growth. |
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| FPAP001 | Electron Cloud Build-Up Study for DAFNE | positron, electron, vacuum, wiggler | 779 | ||
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After the first experimental observations compatible with the presence of the electron cloud effect in the DAFNE positron ring, a more systematic study has been performed regarding the e-cloud build-up and related instability. The measured field map of the magnetic field has been taken into account in the simulation for elements present in the four 10 m long bending sections, representing 40% of the whole positron ring. The simulation results obtained with different codes are presented and compared with the recent experimental observations performed on the beam instabilities and the vacuum behavior of the positron ring.
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| FPAP002 | Experimental Determination of E-Cloud Simulation Input Parameters for DAFNE | electron, photon, vacuum, radiation | 817 | ||
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After the first experimental observations compatible with the presence of the electron-cloud effect in the DAFNE positron ring, an experimental campaign has been started to measure realistic parameters to be used in the simulation codes. Here we present a synchrotron radiation experiment on the photon reflectivity from the actual Al vacuum chamber of DAFNE (same material, roughness and surface cleaning as the one used to manufacture the ring) in the same energy range of photons produced by the accelerator itself. The derived experimental parameter has than been included in the e-cloud simulation codes and the obtained results confirm the relevance of the detailed knowledge of the input parameter to obtain reliable e-cloud simulations.
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| FPAP003 | Simulation Study of the Electron Cloud Instability in SuperKEKB | electron, positron, vacuum, synchrotron | 868 | ||
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The electron-cloud instability (ECI), especially a beam blowup caused by the single-bunch instability, is one of the most important issues faced at existing B factories. In SuperKEKB which is an upgrade plan of the KEK B factory, a positron beam will be stored in the high energy ring after LINAC upgrade to mitigate the ECI and ante-chambers will be effective to reduce the number of electrons. Nevertheless the ECI might be an issue of SuperKEKB because a large beam current of 4.1A will be stored with a short bunch spacing of 2ns. We performed a simulation of the cloud buildup by a program CLOUDLAND. The average electron density and the electron density at the center of a chamber were calculated both in drift space and in various magnetic fields. The result shows that a solenoid field is very effective for reducing the electron density. The simulated electron density will be compared with a threshold electron density of the strong head-tail instability.
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| FPAP004 | Simulation Analysis of Head-Tail Motion Caused by Electron Cloud | electron, feedback, dipole, betatron | 907 | ||
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Synchro-beta side band caused by electron cloud instability has been observed at KEK-B factory. The side-band appears between $νβ+νs$ and $νβ+2νs$ above the threshold of beam size blow up and disappear by applying solenoid field. The side-band is an evidence of strong head-tail instability caused by electron cloud. The side-band is characterized by positive shift, $+1-2νs$, while general strong head-tail instabilities give frequency with negative shift $νbeta-ν_s$. We study the synchro-beta spectrum using a code, PEHTS, which simulates single bunch electron cloud instability.
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| FPAP005 | Coupled Bunch Instability Caused by Electron Cloud | electron, feedback, betatron, positron | 943 | ||
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Coupled bunch instability caused by electron cloud has been observed in some positron storage ring. We discuss the mode spectrum of the coupled bunch instability due to electrons moving in drift space, weak solenoid field and strong bending field. The mode spectrum of the instability is reflected by the electron motion: that is, we understand global characteristics of elecron motion from the mode spectrum.
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| FPAP007 | Measurement of the Electron Cloud Density Around the Beam | electron, positron, storage-ring, vacuum | 1054 | ||
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Under the present operating condition of KEKB LER, most high energy electrons in the electron cloud that hit the chamber wall are produced near the circulating bunch by the single kick. By separating the high energy component of the electron current monitored at a pump port of a vacuum chamber, the density of the electron cloud near the beam is estimated. The estimated density is close to the order of magnitude expected from simulation. At present there still remains an ambiguity that comes from the detector efficiency in the measurement and the assumed secondary electron yield in the simulation.
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| FPAP012 | The Effect of Inhomogeneous Magnetic Field on Budker-Chirikov Instability | electron, ion, resonance, betatron | |||
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The two-beams electron - ion system consists of a nonrelativistic ion beam propagating co-axially with a high-current relativistic electron beam in a longitudinal inhomogeneous magnetic field. The effect of the longitudinal inhomogeneous magnetic field on instability Budker-Chirikov (BCI) in the system is investigated by the method of a numerical simulation in terms of the kinetic description of both beams. The investigations are development of investigations in*,**. Is shown, when the inhomogeneity magnetic field results in the decreasing of an increment of instability Budker-Chirikov and the increasing of length of propagation of a electron beam. Also is shown, when take place the opposite result.
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*Yu.Ya. Golub, N.E.Rozanov, Nuclear Instruments and Methods in Physics Research, A358 (1995) 479. **Yu.Ya. Golub, Proceedings of EPAC 2002, Paris, France, p. 1497. |
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| FPAP013 | Emittance Growth Caused by Electron Cloud Below the “Fast TMCI” Threshold: Numerical Noise or True Physics? | electron, emittance, proton, synchrotron | 1344 | ||
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Simulations show a persisting slow emittance growth for electron cloud densities below the threshold of the fast Transverse Mode Coupling type instability, which could prove important for proton beams with negligible radiation damping, such as in the LHC. We report on a variety of studies performed to quantify the contributions to the simulated emittance growth from numerical noise in the PIC module and from an artificial resonance excitation due to the finite number of kicks per turn applied for modeling the cloud-bunch interaction.
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| FPAP014 | Electron Cloud Measurements in the SPS in 2004 | electron, vacuum, proton, space-charge | 1371 | ||
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Novel measurements of the electron cloud have been performed in the SPS in 2004. In this machine the beam consists of a number of short bunch trains. By varying the distance between these trains it is possible to witness the survival of the electrons after the bunch passage. In this paper, results from simulations and experiments are compared.
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| FPAP016 | Initial Self-Consistent 3-D Electron-Cloud Simulations of LHC Beam with the Code WARP+POSINST | electron, ion, proton, heavy-ion | 1479 | ||
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Funding: This work was performed under the auspices of the U.S. Department of Energy by University of California, LLNL and LBNL under contracts W-7405-Eng-48, and DE-AC03-76F00098. |
We present initial results from the self-consistent beam-cloud dynamics simulations of a sample LHC beam, using a newly developed set of modeling capability based on a merger of the three-dimensional parallel Particle-In-Cell accelerator code WARP and the electron cloud code POSINST.*,** Although the storage ring model we use as a test bed to contain the beam is much simpler and shorter than the LHC, its lattice elements are realistically modeled, as is the beam and the electron cloud dynamics. The simulated mechanisms for generation and absorption of the electrons at the walls are based on previously validated models available in POSINST.*** *J.-L. Vay, these proceedings. **J.-L. Vay, Proc. "ECLOUD04," Napa (California), 2004. ***M.T.F. Pivi and M.A. Furman, Phys. Rev. STAB, PRSTAB/v6/i3/e034201. |
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| FPAP017 | Luminosity Optimization With Offset, Crossing Angle, and Distortion | luminosity, electron, positron, linear-collider | 1541 | ||
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Funding: Work is supported by the U.S. Department of Energy under contract DE-AC02-76SF00515. |
In a linear collider, sources of beam jitter due to kicker noise, quadrupole vibration and long-range transverse wakefields will lead to beam offsets and tilts at the Intersection Point (IP). In addition, sources of emittance dilution such as short-range transverse wakefields or dispersive errors will lead to internal beam distortions. When the IP disruption parameter is large, these beam imperfections will be amplified by a single bunch kink instability which will lead to luminosity loss. In this paper, we study the luminosity loss and then the optimization required to cancel the luminosity loss first analytically and then with simulation. |
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| FPAP018 | Luminosity Loss Due to Beam Distortion and the Beam-Beam Instability | luminosity, resonance, emittance, electron | 1586 | ||
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Funding: Work is supported by the U.S. Department of Energy under contract DE-AC02-76SF00515. |
In a linear collider, sources of emittance dilution such as transverse wakefields or dispersive errors will couple the vertical phase space to the longitudinal position within the beam (the so-called ‘banana effect'). When the Intersection Point (IP) disruption parameter is large, these beam distortions will be amplified by a single bunch kink instability which will lead to luminosity loss. We study this phenomena both analytically using linear theory and via numerical simulation. In particular, we examine the dependence of the luminosity loss on the wavelength of the beam distortions and the disruption parameter. This analysis may prove useful when optimizing the vertical disruption parameter for luminosity operation with given beam distortions. |
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| FPAP020 | Close-Coupling R-Matrix Approach to Simulating Ion-Atom Collisions for Accelerator Applications | electron, target, coupling, background | 1685 | ||
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Funding: Funded by DOE under grant # DE-FG02-02ER83553. |
We have implemented an R-matrix close coupling approach to calculate capture, ionization, stripping and excitation cross-sections for 0.5 to 8.0 MeV K+ incident on Ar. This is relevant to the High Current Experiment at Lawrence Berkley National Laboratory. These cross sections are used to model accelerator particle dynamics where background gasses can interfere with beam quality. This code is a semi-classical approach that uses quantum mechanics to describe the particle interactions and uses classical mechanics to describe the nuclei trajectories. We compare a hydrogenic approximation for K+ with a pseudo-potential approach. Further we are developing a variational approach to quickly determine the best pseudo-potential parameters. Since many R-Matrix computationalists use this pseudo-potential approach, this approach will be useful for helping generate cross sections for any collision system. |
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| FPAP021 | A Cross-Platform Numerical Model of Ion-Wall Collisions | ion, electron, heavy-ion, vacuum | 1707 | ||
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Ion collisions with beam-pipe walls is a significant source of secondary electron clouds and desorbed neutral gasses in particle accelerators. Ions may reflect from beam-pipe walls and undergo further collisions downstream. These effects can cause beam degradation and are expected to be problematic in the design of heavy ion accelerators. The well-known SRIM code provides physically-based monte carlo simulations of ion-wall collisions. However, it is difficult to interface SRIM with high-performance simulation codes. We present details on the development of a package of Python modules which integrate the simulation of ion-wall interactions at grazing incidences with the high-performance particle-in-cell and electron cloud codes WARP and POSINST. This software package, called GriPY, calculates reflected angles and energies of ions which strike beam-pipe walls at grazing incidences, based upon interpolation of monte carlo statistics generated by benchmark simulations run in SRIM for a variety of relevant incident angles and energies. We present here solutions for 1.8 MeV K+ ions and 1 Gev protons incident on stainless steel.
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| FPAP022 | Long Time Simulation of LHC Beam Propagation in Electron Clouds | space-charge, electron, emittance, injection | 1769 | ||
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In this report we show the simulation results of single-bunch instabilities caused by interaction of a proton beam with an electron cloud for the Large Hadron Collider (LHC) using the code QuickPIC [1]. We describe three new results: 1) We test the effect of the space charge of the beam on itself; 2) we add the effect of dispersion in the equation of motion in the x direction, and 3) we extend previous modeling by an order of magnitude (from 50ms to 500ms) of beam circulation time. The effect of including space charge is to change the emittance growth by less than a few percent. Including dispersion changes the plane of instability but keeps the total emittance approximately the same. The longer runs indicate that the long term growth of electron cloud instability of the LHC beam cannot be obtained by extrapolating the results of short runs.
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| FPAP024 | Electron Cloud in the Collimator- and Injection- Region of the Spallation Neutron Source's Accumulator Ring | electron, beam-losses, injection, SNS | 1865 | ||
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge. |
The beam loss along the Spallation Neutron Source’s (SNS’s) accumulator ring is mainly located at the collimator region. From the ORBIT simulation, the peak power deposition at the three collimators is about 500, 350 and 240 W/m, respectively. Therefore, a sizeable number of electrons may be accumulated at this region due to the great beam loss. This paper simulated the electron cloud at the collimator region and the possible remedy. |
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| FPAP029 | Nonlinear Delta-f Particle Simulations of Collective Effects in High-Intensity Bunched Beams | space-charge, coupling, collective-effects, focusing | 2107 | ||
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Funding: Research supported by the U.S. Department of Energy. |
The collective effects in high-intensity 3D bunched beams are described self-consistently by the nonlinear Vlasov-Maxwell equations.* The nonlinear delta-f method,** a particle simulation method for solving the nonlinear Vlasov-Maxwell equations, is being used to study the collective effects in high-intensity 3D bunched beams. The delta-f method, as a nonlinear perturbative scheme, splits the distribution function into equilibrium and perturbed parts. The perturbed distribution function is represented as a weighted summation over discrete particles, where the particle orbits are advanced by equations of motion in the focusing field and self-consistent fields, and the particle weights are advanced by the coupling between the perturbed fields and the zero-order distribution function. The nonlinear delta-f method exhibits minimal noise and accuracy problems in comparison with standard particle-in-cell simulations. A self-consistent 3D kinetic equilibrium is first established for high intensity bunched beams. Then, the collective excitations of the equilibrium are systematically investigated using the nonlinear delta-f method implemented in the Beam Equilibrium Stability and Transport (BEST) code. *R.C. Davidson and H. Qin, Physics of Intense Charged Particle Beams in High Energy Accelerators (World Scientific, 2001). **H. Qin, Physics of Plasmas 10, 2078 (2003). |
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| FPAP034 | Space-Charge Transport Limits in Periodic Channels | lattice, resonance, focusing, space-charge | 2348 | ||
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Funding: Research performed under the auspices of the US DOE by the University of California at LLNL and LBNL under contract Nos. W-7405-Eng-48 and DE-AC03-76SF00098. |
It has been observed in both experiment and particle in cell simulations that space-charge-dominated beams suffer strong emittance growth in alternating gradient quadrupole transport channels when the undepressed phase advance σ0 increases beyond about 80 degrees per lattice period. Transport systems have long been designed to respect this phase advance limit but no theory has been proposed to date to explain the the cause of the limit. Here we propose a mechanism to parametrically explain the transport limit as being due to classes of halo particle orbits moving close to the beam edge in phase-space when σ0 increases beyond 80 degrees. A finite beam edge and/or perturbation acting on an edge particle can then act to move edge particles to large amplitude and lead to large increases in beam phase space area, lost particles, and degraded transport. A core particle model for a uniform density elliptical beam in a periodic focusing lattice was written and is applied to parametrically analyze this process for both periodic alternating gradient quadrupole and solenoidal transport lattices. Self-consistent particle in cell simulations are also carried out to support results. |
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| FPAP036 | Beam Transport in a Compact Dielectric Wall Induction Accelerator System for Pulsed Radiography | emittance, cathode, beam-transport, induction | 2437 | ||
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Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. |
Using dielectric wall accelerator technology, we are developing a compact induction accelerator system primarily intended for pulsed radiography. The accelerator would provide a 2-kA beam with an energy of 8 MeV, for a 20-30 ns flat-top. The design goal is to generate a 2-mm diameter, 10-rad x-ray source. We have a physics design of the system from the injector to the x-ray converter. We will present the results of injector modeling and PIC simulations of beam transport. We will also discuss the predicted time integrated spot and the on-axis x-ray dose. |
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| FPAT002 | Automatic Steering for the CTF3 Linear Accelerator | linac, dipole, focusing, lattice | 814 | ||
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Funding: We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" programme (CARE, contract number RII3-CT-2003-506395) |
A system for automatic beam steering has been implemented at the CTF3 linear accelerator. Beam position readings are logged while corrector magnet strengths are scanned over a given range, thus giving a steering response measurement. Assuming linearity, a response matrix is constructed and used to automatically optimize the beam trajectory along the linac. Using a simple BPM-reading minimization for trajectory correction, this system has been tested in the 2004 CTF3 summer run. Although not in routine operation, it has already proved useful as a tool for the machine setup and operation. In this paper, the automatic steering system for the CTF3 linac is introduced, trajectory correction results are presented, and the agreement with a computer model of the machine is discussed. |
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| FPAT003 | Joining the RHIC Online and Offline Models | lattice, optics, insertion, luminosity | 880 | ||
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Funding: Work performed under the auspices of the U.S. Department of Energy. |
The paper presents an interface encompassing the RHIC online ramp model and the UAL offline simulation framework. The resulting consolidated facility aims to minimize the gap between design and operational data, and to facilitate analysis of RHIC performance and future upgrades in an operational context. The interface is based on the Accelerator Description Exchange Format (ADXF), and represents a snapshot of the RHIC online model which is in turn driven by machine setpoints. This approach is also considered as an intermediate step towards integrating the AGS and RHIC modeling environments to produce a unified online and offline AGS model for operations. |
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| FPAT010 | Automated Beam Steering Using Optimal Control | target, controls, quadrupole, lattice | 1213 | ||
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Funding: Work supported by the U.S. Department of Energy. |
We present an optimal control strategy for beam steering where the operator can specify a variety of optimality conditions by selecting a parameter set describing an optimally steered beam. Novel approaches here include the ability to base optimality on the beam state throughout the entire beamline, rather than just at BPM locations. Moreover, we also may use the trajectory slope to base our optimality criteria. To achieve this feature we must introduce model dependency. Specifically, we predict the state of the beam from BPM measurements, the set-point of the steering magnets, and a model of beam behavior. The predictions are then used to calculate the optimum setting for steering magnets. The optimal control problem has rich mathematical structure that can be exploited and we cover some topics as they apply to accelerator systems. ckallen@lanl.gov |
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| FPAT021 | Experience with Kicker Beam Coupling Reduction Techniques | kicker, impedance, extraction, vacuum | 1742 | ||
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SPS beam impedance is still one of the worries for operation with nominal LHC beam over longer periods once the final configuration will be installed in 2006. Several CERN SPS kickers suffer from significant beam induced ferrite heating. In specific cases, for instance beam scrubbing, the temperature of certain ferrite yokes went beyond the Curie point. Several retrofit impedance reduction techniques have been investigated theoretically and with practical tests. We report on experience gained during the 2004 SPS operation with restively coated ceramic inserts in terms of kicker heating, pulse rise time, operating voltage, and vacuum behavior. For another technique using interleaved metallic strips we observed significant improvements in bench measurements. Advantages and drawbacks of both methods and potential combinations of them are discussed and simulation as well as measured data are shown. Prospects for further improvements beyond 2006 are briefly outlined.
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| FPAT025 | Electron Dynamics of the Rod-Pinch Diode in the Cygnus Experiment at Los Alamos | electron, cathode, ion, plasma | 1901 | ||
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In this work, two-dimensional particle-in-cell simulations are used to examine the electron physics in the rod-pinch diode, a device that can be used to produce a relatively low-energy (a few MeV) radiographic electron source. It is found that with diode parameters for which the electrons' dominant dynamics are approximated well as a magnetized fluid, the diode produces an electron source with a desired small spot size as the electrons drift to and impinge on the anode tip. However, for a large cathode-to-anode radius ratio, a population of electrons that consists predominantly of electrons emitted from the downstream surface of the cathode is found to propagate in the upstream direction and the diode may perform anomalously as a consequence. A method is proposed for improving the quality of the electron source by suppressing electron emission from the downstream cathode surface to reduce the presence of unmagnetized electrons.
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| FPAT026 | The Dynamic Aperture of an Electrostatic Quadrupole Lattice | lattice, quadrupole, beam-losses, focusing | 1946 | ||
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Funding: Work supported by the U.S. DOE, under contract numbers DE-AC03-76SF00098 and W-7405-Eng-48. |
In heavy-ion-driven inertial fusion accelerator concepts, dynamic aperture is important to the cost of the accelerator, most especially for designs which envision multibeam linacs, where extra clearance for each beam greatly enlarges the transverse scale of the machine. In many designs the low-energy end of such an accelerator uses electrostatic quadrupole focusing. The dynamic aperture of such a lattice has been investigated for intense, space-charge-dominated ion beams using the 2-D transverse slice version of the 3-D particle-in-cell simulation code WARP. The representation of the focusing field used is a 3-D solution of the Laplace equation for the biased focusing elements, as opposed to previous calculations which used a less-accurate multipole approximation. 80% radial filling of the aperture is found to be possible. Results from the simulations, as well as corroborating data from the High Current Experiment at LBNL, will be presented. |
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| FPAT028 | Extraction Compression and Acceleration of High Line Charge Density Ion Beams | ion, acceleration, space-charge, heavy-ion | 2032 | ||
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Funding: This work was supported by the Director, Office of Science, Office of Fusion Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. |
HEDP applications require high line charge density ion beams. An efficient method to obtain this type of beams is to extract a long pulse, high current beam from a gun at high energy, and let the beam pass through a decelerating field to compress it. The low energy beam bunch is loaded into a solenoid and matched to a Brillouin flow. The Brillouin equilibrium is independent of the energy if the relationship between the beam size (a), solenoid magnetic field strength (B) and line charge density is such that (Ba)2 is proportional to the line charge density. Thus it is possible to accelerate a matched beam at constant line charge density. An experiment, NDCX-1c is being designed to test the feasibility of this type of injectors, where we will extract a 1 microsecond, 100 mA, potassium beam at 160 keV, decelerate it to 55 keV (density ~0.2 microC/m), and load it into a 2.5 T solenoid where it will be accelerated to 100–150 keV (head to tail) at constant line charge density. The head-to-tail velocity tilt can be used to increase bunch compression and to control longitudinal beam expansion. We will present the physics design and numerical simulations of the proposed experiment |
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| FPAT030 | Parametric Studies of Image-Charge Effects in Small-Aperture Alternating-Gradient Focusing Systems | beam-losses, vacuum, focusing, quadrupole | 2128 | ||
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Funding: The U.S. Department of Energy, Office of High-Energy Physics, Grant No. DE-FG02-95ER40919, Office of Fusion Energy Science, Grant No. DE-FG02-01ER54662, and in part by Air Force Office of Scientific Research, Grant No. F49620-03-1-0230. |
Image charges have important effects on an intense charged-particle beam propagating through an alternating-gradient (AG) focusing channel with a small circular aperture. This is especially true with regard to chaotic particle motion, halo formation, and beam loss.* In this paper, we examine the dependence of these effects on system parameters such as the filling factor of the AG focusing field, the vacuum phase advance, the beam perveance, and the ratio of the beam size to the aperture. We calculate the percentage of beam loss to the conductor wall as a function of propagating distance and aperture, and compare theoretical results with simulation results from the particle-in-cell (PIC) code PFB2D. *Zhou, Qian and Chen, Phys. Plasmas 10, 4203 (2003). |
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| FPAT031 | High Energy Pulsed Power System for AGS Super Neutrino Focusing Horn | target, power-supply, proton, pulsed-power | 2191 | ||
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Funding: Work performed under the auspices of the U.S. Department of Energy. |
This paper present a preliminary design of a 300 kA, 2.5 Hz pulsed power system. This system will drive the focusing horn of proposed Brookhaven AGS Neutrino Super Beam Facility for Very Long Baseline Neutrino Oscillation Experiment. The peak output power of the horn pulsed power system will reach giga-watts, and the upgraded AGS will be capable of delivering 1 MW in beam power. |
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| FPAT033 | Numerical Model of the DARHT Accelerating Cell | electron, pulsed-power | 2269 | ||
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Funding: NNSA/DOE |
The DARHT-2 facility at Los Alamos National Laboratory accelerates a 2 microsecond electron beam using a series of inductive accelerating cells. The cell inductance is provided by large Metglas cores, which are driven by a pulse-forming network. The original cell design was susceptible to electrical breakdown near the outer radius of the cores. We developed a numerical model for the magnetic properties of Metglas over the range of dB/dt (magnetization rate) relevant to DARHT. The model was implemented in a radially-resolved circuit code, and in the LSP* electromagnetic code. LSP simulations showed that the field stress distribution across the outer radius of the cores was highly nonuniform. This was subsequently confirmed in experiments at LBNL. The calculated temporal evolution of the electric field stress inside the cores approximately matches experimental measurements. The cells have been redesigned to greatly reduce the field stresses along the outer radius. *LSP is a software product of ATK Mission Research (www.lspsuite.net). |
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| FPAT035 | Transverse Beam Instability in a Compact Dielectric Wall Induction Accelerator | impedance, induction, resonance, acceleration | 2378 | ||
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Funding: This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. |
Using the dielectric wall accelerator technology, we are developing of a compact induction accelerator system primarily intended for pulsed radiography. Unlike the typical induction accelerator cell that is long comparing with its accelerating gap width, the proposed dielectric wall induction accelerator cell is short and its accelerating gap width is comparable with the cell length. In this geometry, the rf modes may be coupled from one cell to the next. We will present recent results of rf modeling of the cells and prediction of transverse beam instability on a 2-kA, 8-MeV beam. |
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| FPAT037 | Electromagnetic Simulations of Helical-Based Ion Acceleration Structures | ion, coupling, injection, pulsed-power | 2485 | ||
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Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. |
Helix structures have been proposed* for accelerating low energy ion beams using MV/m fields in order to increase the coupling effeciency of the pulsed power system and to tailor the electromagnetic wave propagation speed with the particle beam speed as the beam gains energy. Calculations presented here show the electromagnetic field as it propagates along the helix structure, field stresses around the helix structure (for voltage breakdown determination), optimizations to the helix and driving pulsed power waveform, and simulations showing test particles interacting with the simulated time varying fields. *"Helical Pulseline Structures for Ion Acceleration," Briggs, Reginato, Waldron, this conference. |
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| FPAT038 | Electromagnetic Simulations of Dielectric Wall Accelerator Structures for Electron Beam Acceleration | impedance, acceleration, coupling, monitoring | 2550 | ||
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Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. |
Dielectric Wall Accelerator (DWA) technology incorporates the energy storage mechanism, the switching mechanism, and the acceleration mechanism for electron beams. Electromagnetic simulations of DWA structures includes these effects and also details of the switch configuration and how that switch time affects the electric field pulse which accelerates the particle beam. DWA structures include both bi-linear and bi-spiral configurations with field gradients on the order of 20MV/m and the simulations include the effects of the beampipe, the beampipe walls, the DWA High Gradient Insulator (HGI) insulating stack, wakefield impedance calculations, and test particle trajectories with low emittance gain. Design trade-offs include the transmission line impedance (typically a few ohms), equilibration ring optimization, driving switch inductances, and a layer-to-layer coupling analysis and its affect on the pulse rise time. |
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| FPAT040 | Advanced Electric and Magnetic Material Models for FDTD Electromagnetic Codes | induction, acceleration | 2639 | ||
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Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. |
The modeling of dielectric and magnetic materials in the time domain is required for pulse power applications, pulsed induction accelerators, and advanced transmission lines. For example, most induction accelerator modules require the use of magnetic materials to provide adequate Volt-sec during the acceleration pulse. These models require hysteresis and saturation to simulate the saturation wavefront in a multipulse environment. In high voltage transmission line applications such as shock or soliton lines the dielectric is operating in a highly nonlinear regime, which requires nonlinear models. Simple 1-D models are developed for fast parameterization of transmission line structures. In the case of nonlinear dielectrics, a simple analytic model describing the permittivity in terms of electric field is used in a 3-D finite difference time domain code (FDTD). In the case of magnetic materials, both rate independent and rate dependent Hodgdon magnetic material models have been implemented into 3-D FDTD codes and 1-D codes. |
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| FPAT041 | Design and Simulation of an Anode Stalk Support Insulator | vacuum, alignment, radiation, power-supply | 2663 | ||
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Funding: This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. |
An anode stalk support insulator in a magnetically insulated transmission line was designed and modeled. One of the important design criteria is that within space constraints, the electric field along the insulator surface has to be minimized in order to prevent a surface flashover. In order to further reduce the field on the insulator surface, metal rings between insulator layers were also specially shaped. To facilitate the design process, electric field simulations were performed to determine the maximum field stress on the insulator surfaces and the transmission line chamber. |
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| FPAT047 | Control System of 3 GeV Rapid Cycling Synchrotron at J-PARC | linac, power-supply, beam-losses, monitoring | 2968 | ||
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Funding: Japan Society for the Promotion of Science (JSPS). |
Since the 3GeV RCS produces huge beam power of 1 MW, extreme cares must be taken to design the control system in order to minimize radiation due to beam loss. Another complexity appears in the control system, because each beam bunch of 25 Hz is required to be injected either into the MLF* or into the 50GeV MR.** Therefore, each bunch of 25 Hz must be operated separately, and the data acquisition system must collect synchronized data within each pulse. To achieve these goals, a control system via reflective memory and wave endless recorders has been developed. EPICS is adopted in the control system. Since the number of devices is huge, the management of EPICS records and their configurations require huge amount of time and man power. To reduce this work significantly, a RDB*** for static machine information has been developed. This RDB stores (1) EPICS related information of devices, interfaces, and IOC's**** with a capability to generate EPICS records automatically, and (2) machine geometrical information with a capability to generate lattice files for various simulation applications. The status of the control system focusing on the data acquisition system and the RDB will be presented. *Material and Life Science Facility. **Main Ring. ***Relational Database. ****Input Output Controller. |
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| FPAT058 | Creating EPICS Soft Channels the Easy Way with sddspcas: Features and Applications | quadrupole, emittance, lattice, photon | 3429 | ||
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Funding: This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. |
Using sddspcas, a portable channel access server that is configured by SDDS input files, it is relatively simple to create process variables (PVs). It can be run in a standalone mode or it can be run so that the PVs are checked to ensure that they don’t conflict with other IOCs or portable channel access servers. It can also be run using the Run Control facility to prevent additional instances of the same sddspcas from being run. The SDDS configuration file provides the PV names, upper and lower limits, units, element counts if the PVs are waveforms, and the types of PVs. Valid types include various precision floats and integers as well as strings. One simple application of this program is that software developers can quickly test their code without requiring the coordination needed to update an IOC database to create PVs. Further details of the features, configuration, and applications of sddspcas will be discussed. |
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| FPAT077 | An Accelerator Control Middle Layer Using Matlab | lattice, alignment, photon, feedback | 4009 | ||
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Funding: U.S. Department of Energy under Contract No. DEAC03-76SF00098. |
Matlab is a matrix manipulation language originally developed to be a convenient language for using the LINPACK and EISPACK libraries. What makes Matlab so appealing for accelerator physics is the combination of a matrix oriented programming language, an active workspace for system variables, powerful graphics capability, built-in math libraries, and platform independence. A number of software toolboxes for accelerators have been written in Matlab – the Accelerator Toolbox (AT) for machine simulations, LOCO for accelerator calibration, Matlab Channel Access Toolbox (MCA) for EPICS connections, and the Middle Layer. This paper will describe the MiddleLayer software toolbox that resides between the high-level control applications and the low-level accelerator control system. This software was a collaborative effort between ALS and Spear but was written to easily port. Five accelerators presently use this software – Spear, ALS, CLS, and the X-ray and VUV rings at Brookhaven. The Middle Layer functionality includes energy ramp, configuration control, global orbit correction, local beam steering, insertion device compensation, beam-based alignment, tune correction, response matrices, and script-based physics studies. |
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| FPAT079 | Data Base Extension for the Ensemble Model Using a Flexible Implementation | multipole, quadrupole, sextupole, space-charge | 4036 | ||
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Funding: Work supported by DESY, Hamburg. |
To guarantee an adequate design and a proper functionality of various machine components it is of great importance to perform detailed studies of charged particle transport. However, it is often not necessary to initiate individual kinetic simulations. When the evolution of integral quantities is of research interest, it is worth treating an investigated particle ensemble as a whole and applying a macroscopic formulation. Using a collision-less kinetic approach, the simplified model is derived from the well-known Vlasov equation. Instead of solving directly this equation, one can use moments of the density function obtained by means of an averaging process. This formalism had been implemented into the beam dynamics simulation program V-Code and a fundamental database of various beam line elements like cavities, drift spaces, solenoids, quadrupoles and steerers was set up. A flexible realization of the C++ code representing the cavities and the drift spaces can be automatically used for an arbitrary order of moments applying a symbolic algebra program. A useful extension to the remaining beam line elements together with appropriate simulation results is presented in the paper. |
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| FPAT080 | Simulations of Beam Injection and Extraction into Ion Sources | ion, injection, plasma, background | 4069 | ||
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Funding: INFN-LNL |
Charge breeding, consistiting of injecting singly charged ion into ECRIS(Electron Cyclotron Resonance Ion Sources) to extract an highly charged ion beam, is a promising technique for rare or radioactive ion beam. Efficiency and extracted beam temperature are dominated by the strong collisional diffusion of charged ion inside source. A computer code, named BEAM2ECR, written to simulate details of the injection, ionization, collision and extraction processes is described.* A model of injection plasma sheath and of source fringe field were recently added. Neutral injection is also supported, for comparison with other techniques, like gas feeding or metal vapor injection. Results, clearly favouring near axis injection for most cases are described. Code is written in C-language and possibility of concurrent execution over a Linux cluster was recently added. *M. Cavenago, O. Kester, T. Lamy and P. Sortais, Rev. Sci. Instrum. 73, 537 (2002). |
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| FPAT081 | A New Version of SixTrack with Collimation and Aperture Interface | collimation, proton, betatron, scattering | 4084 | ||
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Simulations of collimation and beam cleaning were so far often performed with simplified computer models. However, the increase in available CPU power has opened the possibility for far more realistic simulations. For large accelerators like LHC it is now possible to track millions of particles, element by element over hundreds of turns. The well established SixTrack code treats the full six-dimensional phase space and considers the non-linear magnet components up to very high order. This code is being used for all LHC tracking simulations and has well developed linear and non-linear error models. SixTrack was extended for tracking of large ensembles of halo particles, taking into account halo interaction with arbitrarily placed collimators. An interface to a program for aperture analysis allows obtaining beam loss maps in the machine aperture. A standardized and portable SixTrack version is now available, providing all functionality of the old SixTrack, as well as the newly added support for halo tracking, collimation and aperture loss maps.
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| FPAT082 | From Visualisation to Data Mining with Large Data Sets | electron, proton, synchrotron, synchrotron-radiation | 4114 | ||
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In 3D particle simulations, the generated 6D phase space data are can be very large due to the need for accurate statistics, sufficient noise attenuation in the field solver and tracking of many turns in ring machines or accelerators. There is a need for distributed applications that allow users to peruse these extremely large remotely located datasets with the same ease as locally downloaded data. This paper will show concepts and a prototype tool to extract useful physical information out of 6D raw phase space data. ParViT allows the user to project 6D data into 3D space by selecting which dimensions will be represented spatially and which dimensions are represented as particle attributes, and the construction of complex transfer functions for representing the particle attributes. It also allows management of time-series data. An HDF5-based parallel-I/O library, with C++, C and Fortran bindings simplifies the interface with a variety of codes. A number of hooks in ParVit will allow it to connect with a parallel back-end that is able to provide remote file access, progressive streaming, and even parallel rendering of particle sets in excess of 1Billion particles.
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| FPAT083 | H5Part: A Portable High Performance Parallel Data Interface for Particle Simulations | alignment | 4129 | ||
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Largest parallel particle simulations, in six dimensional phase space generate wast amont of data. It is also desirable to share data and data analysis tools such as ParViT (Particle Visualization Toolkit) among other groups who are working on particle-based accelerator simulations. We define a very simple file schema built on top of HDF5 (Hierarchical Data Format version 5) as well as an API that simplifies the reading/writing of the data to the HDF5 file format. HDF5 offers a self-describing machine-independent binary file format that supports scalable parallel I/O performance for MPI codes on a variety of supercomputing systems and works equally well on laptop computers. The API is available for C, C++, and Fortran codes. The file format will enable disparate research groups with very different simulation implementations to share data transparently and share data analysis tools. For instance, the common file format will enable groups that depend on completely different simulation implementations to share custom data analysis tools like ParViT without modification. We will show examples and benchmak data for various platforms.
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| FPAT085 | The TAO Accelerator Simulation Program | quadrupole, linac, damping, lattice | 4159 | ||
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Funding: NSF and DOE. |
A new accelerator design and analysis simulation environment based on the BMAD relativistic charged particle dynamics library is in development at Cornell University. Called TAO (Tool for Accelerator Optimization), it is a machine independent program that implements the essential ingredients needed to solve simulation problems. This includes the ability to: 1. Design lattices subject to constraints, 2. Simulate errors and changes in machine parameters, and 3. Simulate machine commissioning including simulating data measurement and correction. TAO is designed to be easily customizable so that extending it to solve new and different problems is straight forward. The capability to simultaneously model multiple accelerator lattices, both linacs and storage rings, and injection from one lattice to another allows for the design and commissioning of large multi stage accelerators. It can also simultaneously model multiple configurations of a single lattice. Single particle, particle beam and macroparticle tracking is implemented. Use of TAO with both the International Linear Collider and the Cornell Energy Recovery Linac are provided as examples. |
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| FPAT086 | Lucretia: A Matlab-Based Toolbox for the Modeling and Simulation of Single-Pass Electron Beam Transport Systems | lattice, linac, klystron, electron | 4197 | ||
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We report on Lucretia, a new simulation tool for the study of single-pass electron beam transport systems. Lucretia supports a combination of analytic and tracking techniques to model the tuning and operation of bunch compressors, linear accelerators, and beam delivery systems of linear colliders and linac-driven Free Electron Laser (FEL) facilities. Extensive use of Matlab scripting, graphics, and numerical capabilities maximize the flexibility of the system, and emphasis has been placed on representing and preserving the fixed relationships between elements (common girders, power supplies, etc.) which must be respected in the design of tuning algorithms. An overview of the code organization, some simple examples, and plans for future development are discussed.
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| FPAT087 | elegantRingAnalysis: An Interface for High-Throughput Analysis of Storage Ring Lattices Using elegant | lattice, dynamic-aperture, storage-ring, sextupole | 4200 | ||
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Funding: Work supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. |
The code {\tt elegant} is widely used for simulation of linacs for drivers for free-electron lasers. Less well known is that elegant is also a very capable code for simulation of storage rings. In this paper, we show a newly-developed graphical user interface that allows the user to easily take advantage of these capabilities. The interface is designed for use on a Linux cluster, providing very high throughput. It can also be used on a single computer. Among the features it gives access to are basic calculations (Twiss parameters, radiation integrals), phase-space tracking, nonlinear dispersion, dynamic aperture (on- and off-momentum), frequency map analysis, and collective effects (IBS, bunch-lengthening). Using a cluster, it is easy to get highly detailed dynamic aperture and frequency map results in a surprisingly short time. |
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| FPAT088 | Advanced Beam-Dynamics Simulation Tools for RIA | linac, rfq, beam-losses, acceleration | 4218 | ||
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Funding: U.S. Department of Energy Contract W-7405-ENG-36. |
We are developing multuparticle beam-dynamics simulation codes for RIA driver linac simulations extending from the low-energy beam transport line to the end of the linac. These codes run on the NERSC parallel supercomputing platforms at LBNL, which allow us to run simulations with large numbers of macroparticles. The codes have physics capabilities needed for RIA, including transport and acceleration of multiple-charge-state beams, beam-line elements such as high-voltage platforms within the linac, interdigital accelerating structures, charge-stripper foils, and capabilities for handling the effects of machine errors and other off-normal conditions. In this paper we present the status of the work, describe some recent additions to the codes, and show preliminary end-to-end simulation results for a representative driver-linac design. |
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| FPAT092 | Optimized Beam Matching Using Extremum Seeking | target, focusing, beam-transport, feedback | 4269 | ||
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The transport and matching problem for a low energy transport system is approached from a control theoretical viewpoint. The beam dynamics and transport section is modeled using the KV envelope equations. Principles of optimal control are applied to this model to formulate techniques which aid in the design of the transport and matching section. Multi-Parameter Extremum Seeking, a real-time non-model based optimization technique, is considered in this work for the lens tuning. Numerical simulations illustrate the effectiveness of this approach.
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| FOAA001 | New Technology in Hydrogen Absorbers for Muon Cooling Channels | emittance, linac, proton, scattering | 84 | ||
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Funding: National Science Foundation. |
Ionization cooling is the only technique fast enough to cool and focus muons for neutrino factories and muon colliders, and hydrogen is the optimal material for maximum cooling and minimal multiple scattering. Liquid hydrogen absorber R & D for the Muon Colloboration has proceeded on parallel and complementary fronts. The continuing LH2 absorber engineering and technical developments by the MuCool group conducted by ICAR* institutions (NIU, IIT and UIUC), the University of Mississippi and Oxford University, in cooperation with Fermilab, will be summarized, including results from the first hydrogen absorber tests at the newly constructed FNAL Mucool Test Area (MTA). The program includes designs for the high-powered test of an absorber prototype (external heat exchange) at the MTA which are nearing completion to be installed by summer 2005, an alternative absorber design (internal heat exchange) being finalized for the approved cooling experiment (MICE) at Rutherford-Appleton Laboratory, and a novel idea for gaseous hydrogen absorbers being developed at Fermilab for a high powered test at the MTA in 2006. *Illinois Consortium for Accelerator Research. |
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| FOAB005 | Technology for Fissionable Materials Detection by Use of 100 MeV Variable Linac | photon, electron, linac, background | 446 | ||
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Funding: This project is funded by CRDF FSTM UKE2-5023-KH-04. |
A new concept for a two-step facility to increase the accuracy/reliability of detecting heavily shielded fissionable materials (FM) in marine containers is presented. The facility will detect FM in two steps. An existing dual-view; dual-energy X-ray scanner, which is based on 7 MeV electron accelerator, will select the suspicious places inside container. The linac with variable energy (up to 100 MeV) will be used for the second step. The technology will detect fissionable nuclei by gamma induced fission reactions and delayed neutron registration. A little-known Ukrainian experimental data obtained in Chernobil’ clean-up program will be presented to ground proposed concept. The theoretical calculations of neutron fluxes scale these results to marine container size. Modified GEANT code for electron/gamma penetration and authors’ own software for neutron yield/penetration are used for these calculations. Available facilities (X-ray scanners; linac; detectors), which will be used for concept proof, are described. The results of the first experiments by use variable energy linac are cited. |
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| FOAD002 | Ultra-High Density Electron Beams for Beam Radiation and Beam Plasma Interaction | electron, emittance, focusing, plasma | 145 | ||
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Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48. |
Current and future applications of high brightness electron beams, which include advanced accelerators such as the plasma wake-field accelerator (PWFA) and beam-radiation interactions such as inverse-Compton scattering (ICS), require both transverse and longitudinal beam sizes on the order of tens of microns. Ultra-high density beams may be produced at moderate energy (50 MeV) by compression and subsequent strong focusing of low emittance, photoinjector sources. We describe the implementation of this method used at LLNL’s PLEIADES ICS x-ray source in which the photoinjector-generated beam has been compressed to 300 fsec duration using the velocity bunching technique and focused to 20 μm rms size using an extremely high gradient, permanent magnet quadrupole (PMQ) focusing system. |
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