| Paper | Title | Other Keywords | Page | ||
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| MOPA009 | Global Decoupling on the RHIC Ramp | coupling, quadrupole, injection, optics | 659 | ||
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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). In the polarized proton run, the betatron tunes are required to keep almost constant on the ramp to avoid spin resonance line crossing and the beam polarization loss. Some possible correction schemes on the ramp, like three-ramp correction, the coupling amplitude modulation and the coupling phase modulaxtion, have been found. The principles of these schemes are shortly reviewed and compared. Operational results of their applications on the RHIC ramps are given. |
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| MOPC004 | Dynamics of a High Density Ion-Beam with Electron Cooling in HIMAC Synchrotron | ion, injection, beam-losses, electron | 416 | ||
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High density circulating-ion beam was obtained with electron-cooling and cool-stacking injection in HIMAC synchrotron. The ion density was saturated at 1.0e9/cm2. Coherent transverse instability was observed when ion- and electron-beam density was high. The dynamics of the cooled ion-beam are described in this report.
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| MOPC007 | Anisotropy-Driven Instability in Intense Charged Particle Beams | plasma, simulation, 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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| MPPE011 | Expected Emittance Growth and Beam Tail Repopulation from Errors at Injection into the LHC | emittance, injection, coupling, simulation | 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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| MPPE015 | Non-Linear Ring Model Calibration with Frequency Analysis of Betatron Oscillations | sextupole, lattice, resonance, target | 1452 | ||
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A precise model of an accelerator ring is crucial to achieve ultimate performance both in synchrotron light sources and high energy synchrotrons. Algorithms have been developed to calibrate the linear model of the ring. They have been successfully applied experimentally to determine and correct the linear optics of the machine. More recently the Frequency Map Analysis has been used to model also the non-linear optics. We propose here a technique based on the fit of non-linear spectral lines to recover the non-linear driving terms and to compensate the non-linear field errors around the ring.
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| MPPE038 | Synchrotron Sidebands of a Linear Differential Coupling Resonance | resonance, coupling, synchrotron, storage-ring | 2538 | ||
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Sidebands of a linear differential coupling resonance are observed in the tune survey of the SPring-8 storage ring. The vertical beam size and the Touschek beam lifetime blow up at a distance by synchrotron tune from the linear differential resonance. The synchrotron sidebands of a linear betatron coupling resonance are excited by the vertical dispersion at sextupole magnets. Although the vertical dispersion of the SPring-8 storage ring is well reduced to be small, order of 1 mm, the linear betatron coupling resonance is further suppressed. In addition, the sextupole magnets are relatively strong as well as other third generation light source facilities. Hence at the SPring-8 storage ring we can observe the synchrotron sidebands of the coupling resonance. By means of the tracking simulation based on the ring model obtained by the response matrix measurement we confirm the existence of the synchrotron sidebands of a linear differential coupling resonance. In order to incorporate synchrotron motion in the simulation, the 6-dimensional tracking code developed at SPring-8 is used.
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| MPPE062 | Measurement and Optimization of Local Coupling from RHIC BPM Data | coupling, injection, dipole, quadrupole | 3553 | ||
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Funding: U.S. Department of Energy. |
Global coupling in RHIC is routinely corrected by using three skew quadrupole families to minimize the tune split. In this paper we aim to re-optimize the coupling at top energy by minimizing resonance driving terms and the C-matrix in two steps: 1. Find the best configuration of the three skew quadrupole families and 2. Identify locations with coupling sources by inspection of the driving terms and the C-matrix around the ring. The measurements of resonance terms and C-matrix are presented. |
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| MPPE066 | Streak Camera Studies of Vertical Synchro-Betatron-Coupled Electron Beam Motion in the APS Storage Ring | electron, synchrotron, storage-ring, kicker | 3694 | ||
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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. |
We present experimental studies of synchro-betatron-coupled electron beam motion in the Advanced Photon Source storage ring. We used a vertical kicker to start the beam motion. When the vertical chromaticity is nonzero, electrons with different initial synchrotron phases have slightly different betatron frequencies from the synchronous particle, resulting in a dramatic progression of bunch-shape distortion. Depending on the chromaticity and the time following the kick, images ranging from a simple vertical tilt in the bunch to more complicated twists and bends are seen with a visible light streak camera. Turn-by-turn beam position monitor data were taken as well. We found that the experimental observations are well described by the synchro-betatron-coupled equations of motion. We are investigating the potential of using the tilted bunch to generate picosecond x-ray pulses. Also note that the fast increase in vertical beam size after the kick is dominated by the internal synchro-betatron-coupled motion of the electron bunch. Experimentally this increase could be easily confused with decoherence of vertical motion if the bunch is only imaged head-on. |
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| MPPP008 | Equilibrium Beam Invariants of an Electron Storage Ring with Linear x-y Coupling | resonance, damping, coupling, electron | 1111 | ||
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Funding: Work is supported by the U.S. Department of Energy under contract DE-AC02-76SF00515. |
In accelerator systems, it is very common that the motion of the horizontal plane is coupled to that of the vertical plane. Such coupling will induce tune shifts and can cause instabilities. The damping and diffusion rates are also changed, which in turn will lead to a change in the equilibrium invariants. Following the perturbative approach which we developed for synchrobetatron coupling,* we study the x-y coupled case in this paper. Starting from the one turn map, we give explicit formulae for the tune shifts, damping and diffusion rates, and the equilibrium invariants. We focus on the cases where the system is near the integer or half integer, and sum or difference resonances where small coupling can cause a large change in the beam distribution. *B. Nash, J. Wu, and A. Chao, work in progress. |
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| MPPP011 | Fermilab Recycler Damper Requirements and Design | impedance, kicker, damping, feedback | 1239 | ||
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The design of transverse dampers for the Fermilab Recycler storage ring is described. An observed instability and analysis of subsequent measurements are used to identify the requirements. The digital approach being mplemented is presented.
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| MPPP012 | First-Principles Simulation and Comparison with Beam Tests for Transverse Instabilities and Damper Performance in the Fermilab Main Injector | simulation, damping, dipole, injection | 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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| MPPP042 | Landau Damping of the Weak Head-Tail Instability at Tevatron | damping, octupole, proton, injection | 2714 | ||
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Landau damping of the head-tail modes in Tevatron beam with the help of octupole-generated betatron tune spreads permits to reduce chromaticity from 15-20 units to zero thus significantly improving the beam lifetime. The octupole strengths have been experimentally optimized at different stages of the Tevatron operation, from proton injection to collision. Predictions of the analytical Landau damping model are compared with the experimental results.
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| MPPP043 | Betatron Tune Spread Generation and Differential Chromaticity Control by Octupole at Tevatron | octupole, proton, antiproton, injection | 2756 | ||
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Application of octupoles for Landau damping of the unstable head-tail modes requires careful consideration at their combination into separate families to insure maximum effectiveness and avoid degradation of the dynamic aperture due to the non-linear magnetic fields. Existing octupolar magnets around the machine have been arranged into four functional families with individual power supplies. Two of these families generate betatron tune spreads in the vertical and horizontal planes whereas the other two control the differential chromaticity between the proton and antiproton helices. The calculated effect on tunes and chromaticity is compared with direct measurements. Analytical formulas for betatron tune spectral density functions are presented.
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| MPPP049 | Observations and Measurements of Anomalous Hollow Electron Beams in a Storage Ring | lattice, storage-ring, single-bunch, electron | 3082 | ||
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Funding: This work is supported by the U.S. AFOSR MFEL grant F49620-001-0370 and by U.S. DOE grant DE-FG05-91ER40665 (YW and JL). This work is also supported by U.S. DOE contract DE-AC02-76SF00515 (JW). |
This paper reports first observations and measurements of anomalous hollow electron beams in a storage ring. In a lattice with a negative chromaticity, hollow electron beams consisting of a solid core beam inside and a large ring beam outside have been created and studied in the Duke storage ring. We report the detailed measurements of the hollow beam phenomenon, including its distinct image pattern, spectrum signature, and its evolution with time. By capturing the post-instability bursting beam, the hollow beam is a unique model system for studying the transverse instabilities, in particular, the interplay of the wake field and the lattice nonlinearity. In addition, the hollow beam can be used as a powerful tool to study the linear and nonlinear particle dynamics in the storage ring. |
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| MPPT053 | Restoring the Skew Quadrupole Moment in Tevatron Dipoles | quadrupole, dipole, coupling | 3244 | ||
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Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-76CH03000. |
In early 2003 it was realized that mechanical changes in the Tevatron dipoles had led to a deterioration of the magnetic field quality that was hindering operation of the accelerator. After extensive study, a remediation program was started in late 2003 which will continue through 2005. The mechanical and magnetic effects are discussed. The readjustment process and experience are reported, along with other observations on aging magnets. |
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| TPAE034 | Developing a Multi-Timescale PIC Code for Plasma Accelerators | plasma, simulation, 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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| TPAE046 | Modeling Self-Ionized Plasma Wakefield Acceleration for Afterburner Parameters Using QuickPIC | simulation, plasma, electron, 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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| TPAP003 | Exploring a Nonlinear Collimation System for the LHC | sextupole, collimation, optics, insertion | 877 | ||
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We explore the adaptation of a nonlinear collimation system, as previously considered for linear colliders, to LHC betatron cleaning. A possible nonlinear system for LHC consists of a horizontal and vertical primary collimator located in between a pair of skew sextupoles. We discuss the modified LHC optics, the need for and optimum placement of secondary absorbers, and the simulated cleaning efficiency.
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| TPAP008 | Measurements of the LHC Collimator Impedance with Beam in the SPS | impedance, pick-up, collimation, vacuum | 1132 | ||
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The transverse impedance of the LHC collimators will likely dominate the overall transverse impedance in the LHC at high energies and potentially limit the maximum intensity. A prototype collimator was recently tested in the SPS. Small, but significant tune shifts depending on the collimator position have been observed using different independent high resolution tune measurement methods. In addition trapped modes predicted from numerical simulation at the ends of the collimator jaws have been identified by bench measurement techniques as well as with the beam. We present a description of the measurements and an analysis of the results.
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| TPAP028 | Observations of Strong Transverse Coupling in the Tevatron | quadrupole, coupling, dipole, collider | 2029 | ||
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Funding: United States Department of Energy under Contract No. DE-AC02-76CH03000. |
During the beginning of Run II of the Tevatron Collider it became apparent that a large skew quadrupole source, or sources, had developed in the superconducting synchrotron. Efforts to locate the current source of coupling were undertaken, with the eventual discovery that the main magnets had developed a systematic skew quadrupole moment over their lifetime. Over the past year, the magnets have been altered in place in an attempt to restore the systematic skew quadrupole moment to zero. Beam observations and their interpretations are presented, and remedial measures are discussed. |
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| TPAP033 | Tevatron Admittance Measurement | emittance, proton, antiproton, kicker | 2306 | ||
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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. |
We measured the Tevatron Beam Acceptance by the method of exciting the beam emittance growth with the beam tickling system with noise. The noise power was about 3Watt with 100Hz bandwidth and centered either in horizontal betatron frequency or vertical betatron frequency. We were able to blow the beam emittance fast while under control. From the point the beam emittance stop growing, we measured the beam acceptance of the Tevatron. |
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| TPAP044 | Observations of Snake Resonance in RHIC | resonance, polarization, injection, proton | 2839 | ||
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Funding: The work was performed under the auspices of the U.S. Department of Energy. |
Siberian snakes now become essential in the polarized proton acceleration. With proper configuration of Siberian snakes, the spin precession tune of the beam becomes $\frac{1}{2}$ which avoids all the spin depolarizing resonance. However, the enhancement of the perturbations on the spin motion can still occur when the betatron tune is near some low order fractional numbers, called snake resonances, and the beam can be depolarized when passing through the resonance. The snake resonances have been confirmed in the spin tracking calculations, and observed in RHIC with polarized proton beam. Equipped with two full Siberian snakes in each ring, RHIC provides us a perfect facility for snake resonance studies. This paper presents latest experimental results. New insights are also discussed. |
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| TPAP051 | Principle of Global Decoupling with Coupling Angle Modulation | coupling, quadrupole, simulation, injection | 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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| TPAT022 | Future Plans for the Small Isochronous Ring | space-charge, quadrupole, focusing, dipole | 1778 | ||
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Funding: Work supported by NSF Grant #PHY-0110253 and DOE Contract DE-AC05-84ER40150. |
The Small Isochronous Ring has been operational at Michigan State University since December 2003. It is used for experimental studies of the beam dynamics in high-intensity isochronous cyclotrons and synchrotrons at the transition energy. The operational experience with SIR has proven that the ring can be successfully used to study space charge effects in accelerators. The low velocity of beam particles in the ring allowed us to achieve a high accuracy of longitudinal profile measurements that is difficult to achieve in full-size accelerators. The experimental data obtained in the ring was used for validation of multi-particle, space-charge codes CYCO and WARP3D. Inspired by the solid performance of SIR in the isochronous regime, we consider options for expanding the scope of the beam physics studied in the ring. In this paper, we outline possible future experiments and discuss required modifications of the ring optics and hardware. |
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| TPAT084 | LIFETRAC Code for the Weak-Strong Simulation of the Beam-Beam Effect in Tevatron | simulation, 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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| TPAT086 | Enhanced Optical Cooling of Particle Beams in Storage Rings | undulator, kicker, pick-up, radiation | 4179 | ||
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In this scheme undulators are installed in straight sections of a storage ring at distances determined by a phase advance 2pπ+π between first and second undulators and 2π between next undulators, where p=1,2,3.. . UR emitted in the first undulator pass through an optical system with movable screens 1,2 in the image plane of the particle beam. If screens let pass the UR then the past UR is amplified and pass through the second and next undulators together with the particle. Every particle loses its energy in the overlapped fields of the amplified UR and these undulators. Motion of screens in the optical system leads to particle energy losses in second and following undulators similar to losses in moving targets T1,2 in the schemes of enhanced ion cooling.* Energy losses are accompanied by a decrease of both energy spread and amplitudes of betatron oscillations that is enhanced cooling if, at first, the moving screen 2 will produce conditions of the energy loss for higher energy particles. When the screen 2 will open image of all particles the system must be closed and then the cooling process can be repeated*.
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*physics/0404142. |
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| TOAD002 | Novel Tune Diagnostics for the Tevatron | antiproton, proton, pick-up, injection | 140 | ||
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The Tevatron collides protons and antiprotons in the same beam pipe. This poses a challenge in the measurement of tunes for both species simultanously because of the possibility of signal contamination from the other species. On top of this, since both beams are in the same beam pipe, tunes of individual bunches are also important because tune shifts from the beam-beam effect affects each bunch differently. Three different tune diagnostics used in the Tevatron will be discussed in this paper: 1.7GHz Schottky pickups, 21.4 MHz Schottky pickups and 27 kHz baseband pickups. These pickups look at the tune spectrum at different frequency bands and provide useful physics information for each frequency regime.
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| TOPC005 | Transverse Emittance Blow-Up Due to the Operation of Wire Scanners, Analytical Predictions and Measurements | emittance, scattering, simulation, proton | 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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| TPPP002 | Global-Beta Measurement and Correction at the KEKB Rings | optics, quadrupole, sextupole, closed-orbit | 802 | ||
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The global-beta correction is a part of the optics corrections which are performed to regularize the ring optics for the luminosity tunings. The global-beta measurement is performed by the reconstruction of the beta function from the set of the single kick orbits generated by the 6 kinds of the steering magnets. The distortion of the beta fucntion and the phase advance are corrected by the global beta correction using the fudge factors of power supplies of quadrupole magnets. These correction scheme are successfully working. In the typical case, the r.m.s. of the beta function beat and the betatron tune difference are corrected within 5% and 0.0005, respectively. In the luminosity run, we can operate the low energy ring(LER) with the horizontal betatron tune very close to half-integer(45.5050). In this paper, we will report in detail the global-beta measurement and correction techniques and its performance in the KEKB operation.
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| TPPP011 | Investigations of Injection Orbits at CESR Based on Turn-By-Turn BPM Measurements | injection, electron, positron, optics | 1228 | ||
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Funding: National Science Foundation. |
Development of a data acquisition permitting turn-by-turn orbit measurements has been employed at CESR to study the optics of the injected electron beam. An optimization algorithm uses these measurements to determine the effective lattice functions describing the behavior of the injected electrons. We present comparisons of these measurements to tracking calculations of injection acceptance envelopes which account for the parasitic beam-beam interactions with the stored positron beam. |
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| TPPP012 | A Study of the Effect of Beam-Beam Interactions on CESR Optics | electron, positron, quadrupole, lattice | 1275 | ||
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Funding: National Science Foundation. |
The CESR storage ring facility has begun operation in an energy region which allows high-statistics investigation of charm-quark bound states. Experience during the first year has shown that the effects of parasitic crossings in the pretzel orbits present an important factor in injection efficiency, in the beam lifetime and stored current limits. We compare the results of beam dynamics and tracking calculations which quantify the effects of these parasitic crossings on optics and dynamic aperture for the injected and stored trajectories to observations of beam behavior. |
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| TPPP014 | Ionization Cooling Using a Parametric Resonance | emittance, resonance, focusing, luminosity | 1374 | ||
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Funding: This work was supported in part by DOE SBIR grant DE-FG02-04ER84016. |
Muon collider luminosity depends on the number of muons in the storage ring and on the transverse size of the beams in collision. Ionization cooling as it is presently envisioned will not cool the beam sizes sufficiently well to provide adequate luminosity without large muon intensities. A new idea to combine ionization cooling with parametric resonances has been developed that will lead to beams with much smaller sizes so that high luminosity in a muon collider can be achieved with fewer muons. In the linear channel described here, 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. We discuss the theory of Parametric-resonance Ionization Cooling, including the sensitivity to aberrations and the need to start with a beam that has already been cooled adequately. |
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| TPPP023 | Simulation of PEP-II Accelerator Backgrounds Using TURTLE | scattering, background, collimation, electron | 1835 | ||
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We present studies of accelerator-induced backgrounds in the BaBar detector at the SLAC B-Factory, carried out using a modified version ofthe DECAY TURTLE simulation package. Lost-particle backgrounds in PEP-II are dominated by a combination of beam-gas bremstrahlung, beam-gas Coulomb scattering, radiative-Bhabha events and beam-beam blow-up. The radiation damage and detector occupancy caused by the associated electromagnetic shower debris can limit the usable luminosity. In order to understand and mitigate such backgrounds, we have performed a full programme of beam-gas and luminosity-background simulations, that include the effects of the detector solenoidal field, detailed modelling of limiting apertures in both collider rings, and optimization of the betatron collimation scheme in the presence of large transverse tails.
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| WOAC005 | Application of Independent Component Analysis for Beam Diagnosis | synchrotron, booster, lattice, injection | 489 | ||
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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 independent component analysis (ICA)* is applied to analyze simultaneous multiple turn-by-turn beam position monitor (BPM) data of synchrotrons. The sampled data are decomposed to physically independent source signals, such as betatron motion, synchrotron motion and other perturbation sources. The decomposition is based on simultaneous diagonalization of several unequal time covariance matrices, unlike the model independent analysis (MIA),** which uses equal-time covariance matrix only. Consequently the new method has advantage over MIA in isolating the independent modes and is more robust under the influence of contaminating signals of bad BPMs. The spatial pattern and temporal pattern of each resulting component (mode) can be used to identify and analyze the associated physical cause. Beam optics can be studied on the basis of the betatron modes. The method has been successfully applied to the Booster Synchrotron at Fermilab. *A. Belouchrani et al., IEEE Trans. on Signal Processing, {\bf 45}, 434-444, (1997). **J. Irwin, et al., Phys. Rev. Lett. {\bf 82}, 1684 (1999); Chun-xi Wang, et al., Phys. Rev. ST Accel. Beams} {\bf 6}, 104001 (2003). |
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| WOAC009 | Techniques for Measurement and Correction of the SNS Accumulator Ring Optics | quadrupole, SNS, optics, injection | 674 | ||
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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) Accumulator Ring will reach peak intensities of 1.5x1014 protons/pulse through multi-turn charge-exchange injection. Accumulation of these unprecedented beam intensities must be accomplished while maintaining extremely low losses (less than 1 W/m). It is anticipated that the control of the ring optics will be important for achieving these low loss rates. We describe our plans for measuring and correcting the optical functions of the accumulator ring lattice. |
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| ROAA002 | CESR-c: Performance of a Wiggler-Dominated Storage Ring | wiggler, resonance, luminosity, sextupole | 189 | ||
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Funding: Work supported by the U.S. National Science Foundation. |
CESR-c operates now as a Wiggler-Dominated Storage Ring extending the lowest operating energy to 1.5GeV/beam. To improve beam stability at low energy, 12 super-ferric wiggler magnets with total length of 15m and 2.1T maximum field were installed in the ring. They cause ~90% of total beam radiation lost and increase radiation damping rate by factor 10 from ~3 to 40 Hz. However, the field of the wiggler magnets not only initiates the radiation, but potentially affects beam dynamics. The latter was an issue of a great concern from the planning the CESR-c project. In this paper we describe general performance of CESR-c and report the results of an experimental study on some aspects of beam dynamics. Comparisons are made between the experimental data and the model prediction. We find that all parameters, which are critically dependent on wigglers, such as beam properties and ring nonlinearity, are in good agreement with those calculated from the model. This validates the ring and wiggler models and justifies our design and production technique of the magnets. The experience we obtained will be extremely useful in future work on linear collider damping rings. |
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| RPAE017 | Radially Polarized Ion Channel Laser | ion, bunching, radiation, electron | 1526 | ||
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Radially polarized radiation is amplified by a free electron laser (FEL) in which the undulator is an ion channel with uniform density. For long betatron wavelengths and low gain per pass, the gain at a given distance from the axis is three-eighths the gain of a periodic ion channel laser with the same wiggler parameter. For amplification of short wavelengths by an ultrarelativistic electron beam, a uniform-density ion channel requires a much higher ion density than a periodic ion channel laser.
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| RPAE029 | Analytical Considerations for Reducing the Effective Emittance with Variable Dipole Field Strengths | emittance, optics, dipole, damping | 2086 | ||
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The basic optics design scope in lepton rings is to match the sections in either side of the bending magnets in order to minimise the equilibrium emittance. A further important emittance reduction can be achieved by incorporating dipoles for which the deflecting field varies along the electron beam path in the magnet. The figure of merit for such lattices when used in a synchrotron light source is the minimization of the so-called effective emittance. The effective emittance is computed in the middle of the undulator straight section as the product of the rms size and divergence and therefore includes contributions from the betatron emittance and from the electron energy spread. In this paper, analytical formulas are obtained for the minimum betatron and effective emittance in arbitrary dipole fields and the associated optics function at the dipole entrance. Examples are given for specific dipole field functions and their properties with respect to the effective emittance minimisation. Finally, the effective emittance is parameterised with respect to standard cell optics properties, such as the phase advance, the maximum beta and dispersion functions and the focusing element strengths.
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| RPAE044 | Operation and Recent Developments of the Photon Factory Advanced Ring | injection, single-bunch, vacuum, emittance | 2845 | ||
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The Photon Factory Advanced Ring (PF-AR) is a synchrotron light source dedicated to X-ray research. The PF-AR is usually operated at a beam energy of 6.5 GeV, but a 5.0 GeV mode is also available for medical application. In 6.5 GeV mode the typical lifetime of 15 hrs and the beam current of 60 mA with a single-bunch have been archived. Almost full-time single-bunch operation for pulse X-ray characterize the PF-AR. However, single-bunch high-current caused several problems to be solved, including the temperature rise of the some of the vacuum component, a pressure increase in the ring, and a sudden drop in lifetime. In order to avoid these issues the developments of new methods have been continued. In this paper, the status and the recent developments of the PF-AR will be presented. It concerns: the successful operation with two-bunch high-current in 5.0 GeV mode; varying the vertical beam size for the medical application; modulating the RF acceleration phase in order to elongate the length of bunch; stabilizing temperature in the ring tunnel; the study for medium emittance operation with 160 nmrad; moving the RF cavities in order to install a new insertion device; an innovative injection scheme using a pulsed quadrupole magnet.
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| RPAE080 | Diagnostic Systems Plan for the Advanced Light Source Top-Off Upgrade | injection, kicker, diagnostics, monitoring | 4066 | ||
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Funding: This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Science Division, of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. |
The Advanced Light Source (ALS) will soon be upgraded to enable top-off operation,* in which electrons are quasi-continuously injected to produce constant stored beam current. We will upgrade our injector from 1.5GeV to full-energy 1.9GeV, and top-off operation will also require more precise injector beam characterization and control than we are capable of using our current diagnostics system. Therefore, a diagnostics upgrade will be crucial for the success of top-off, and our plan for it is described in this paper. Among the improvements will be the integration of all existing beam current monitors along the accelerator chain into an injection efficiency monitoring application. New booster ring diagnostics will include a tune kick and monitoring system, updated beam position monitor electronics, and a new scraper. Two new synchrotron light monitors and a beam stop will be added to the booster-to-storage ring transfer line, and a dedicated bunch purity monitoring system will be installed in the storage ring. Together, these important diagnostic upgrades will enable smooth commissioning of the full energy injector and a quick transition to high quality top-off operation at the ALS. *Please see the ALS Top-off Upgrade presentation at this conference. |
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| RPAT012 | A Hardware Transverse Beam Frequency Response Simulator | synchrotron, feedback, resonance | 1269 | ||
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Funding: Fermi National Accelerator Lab. |
We build an electronical instrument to get the frequency response close to the pattern of transverse beam frequency response. The method is to apply 1)a time delay circuit with ADC, FIFO RAM and DAC; 2)a phase shift circuit which is an all pass filter with adjustable phase shift in the frequency range of 25kHz to 30kHz; in a feedback loop of 3)a commutating filter which is a high Q band pass filter. We can dynamically adjust the center frequency, the side band distance during the testing. With this instrument, some beam instruments can be tested without using the real beam. |
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| ROPB007 | 3-D Parallel Simulation Model of Continuous Beam-Electron Cloud Interactions | simulation, electron, 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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| ROPB009 | Betatron Sidebands Due to Electron Clouds Under Colliding Beam Conditions | luminosity, electron, positron, feedback | 680 | ||
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Recently, we have observed vertical betatron sidebands in the transverse beam spectra of positron bunches at the KEKB LER which are associated with the presence of electron clouds. When the LER is operating in single-beam mode (no colliding bunches in the HER), these sidebands are sharply peaked. When the bunches are in collision for physics running, the sidebands are still present but are found to be smeared out. The bunch-by-bunch specific luminosity is lower for bunches with sidebands than for those without sidebands. In this paper, the behavior of the sidebands in collision and the effects on luminosity are discussed.
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| RPPT046 | Development and Application of Bunch-by-Bunch Measurement System of HLS | damping, synchrotron, single-bunch, pick-up | 2932 | ||
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This paper is intended to present the newly implemented wideband (100MHz) bunch oscillation measurement system, which is in nature a different method from the narrow-band (<5MHz) facilities employed before. Basic formalism and implementation details of the system is introduced to illustrate the function of observing coupled bunch instabilities in time and frequency domain. The designed function includes detecting of transverse oscillation, synchrotron phase oscillation, as well as bunch filling pattern. Some diagnostics results of machine instabilities and application of this system are also discussed.
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| RPPT050 | The Measurement of Tune and Phase Space at HLS | extraction, lattice, storage-ring, pick-up | 3114 | ||
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Tune and phase space online monitor at the electronic storage ring of Hefei Light Source (HLS) have been realized by using of turn-by-turn beam position data. In this paper, we have compared many methods to compute tune and discussed how to choose the best fitting method for our online tune computing. We can compute and display tune online, at the same time, beam tracks were obtained on the transverse phase space by using turn-by-turn beam position data at two differently-located beam-position-monitor electrodes. With these instruments we can precise and attractive study machine instabilities
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| RPPT052 | Analysis of Rapid Betatron Resonance Crossing | resonance, acceleration, lattice, linac | 3206 | ||
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Funding: TRIUMF receives federal funding via a contribution agreement through the National Research Council of Canada. |
The reduction of transverse and longitudinal cooling requirements, the increased number of beam circulations, and the reduce cost, as compared to RLAs, are arguments to adopt the linear-field FFAG as the acceleration stage of a Neutrino Factory. Because of the large range of central momenta, pm 50% delta p/p, and negative uncorrected chromaticity, the non-scaling FFAG will cross many integer and half-integer betatron resonances during the 10-20 turns acceleration. There is the expectation that if driving terms are small enough and crossing is fast enough, then there is insufficient time for the betatron amplitudes to grow. The conventional theory of resonance crossing is applied to slow acceleration, over 100s or 1000s of turns. This paper examines whether the rapid parameter changes encountered in the multi-GeV FFAGs, or few-MeV electron model, are compatible with simple theory. |
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| FOAC001 | High Intensity Muon Beam Facilities with FFAG | proton, luminosity, factory, simulation | 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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| FPAE013 | Calculation of the Orbit Length Change of the Recycler Due to Main Injector Ramp | closed-orbit, dipole, lattice, kicker | 1318 | ||
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Orbit length of beam in the Recycler changes during the Main Injector ramps. The unknown kicks from the effects generated by stray field are distributed around the ring. To estimate the changes, simulated virtual kicks are created around each lambson, C-magnet and bus cable of the Main Injector. The orbit lengths are calculated from measurements of evolution frequency and transverse beam positions. A BPM system distributed throughout the Recycler lattice in both Horizontal and vertical planes are used to take the closed orbit measurement during the ramps. The calculation method and the results of the orbit length changes and the strength of the simulated kicks are presented in this report.
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| FPAE025 | Study of Slow Beam Extraction Through the Third Order Resonance with Transverse Phase Space Manipulation by a Mono-Frequency RFKO | emittance, electron, sextupole, extraction | 1892 | ||
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An electron pulse-stretcher ring (STB ring) has a function which converts a pulse beam generated by RF linac into a quasi-continuous beam. Circulating beam in the ring is extracted by the third order resonance. Since there is no accelerating field in the ring, the beam approaches a transverse resonance condition due to synchrotron radiation loss with finite chromaticity. The extracted beam from the ring has some spread in time and space corresponding to injected beam from linac even if the injected beam is perfectly matched to the ring optics. However, the extracted beam emittance can be reduced by applying a phase space manipulation using an RF shaker. Under the influence of perturbation using an RF shaker driven by a mono-frequency, the betatron amplitude of circulating beam can be controlled in order to reduce the extracted beam emittance. The experimental results will be reported in this conference.
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| FPAP004 | Simulation Analysis of Head-Tail Motion Caused by Electron Cloud | electron, simulation, feedback, dipole | 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, simulation, feedback, 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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| FPAP012 | The Effect of Inhomogeneous Magnetic Field on Budker-Chirikov Instability | electron, ion, resonance, simulation | |||
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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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| FPAT005 | A Betatron Tune Fitting Package for the Tevatron 21.4 MHz Schottky | synchrotron, antiproton, collider, pick-up | 937 | ||
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Accurate control of the Betatron tunes and chromaticities is required to optimize the dynamical aperture of any large synchrotron. The Fermilab Tevatron is equipped with two independent Schottky monitors, one operating at 21.4 MHz and the other 1.7 GHz. While the latter one allows us to characterize individual bunches separated by 396 ns, the former one has a larger Q and can give precise tune measurements. A new front-end and related data acquisition for this 21.4 MHz resonator has been installed and commissioned during the FY04 Collider RunII. Output signal are digitized at 100 KHz. Frequency spectra are transfered to dedicated server nodes and fitted in real time. Such frequency spectra are quite complex, due to inherent noise, horizontal/vertical coupling and synchrotron motion. Sophisticated fitting strategies are required. Optimization of this fitting package on relatively powerful commodity computer allows us to report tune and chromaticity measurements at almost 1 Hz. The architecture of the data acquisition system and this fitting package are described and results taken during the FY04 and FY05 runs are presented.
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| FPAT022 | Performance of the CERN SPS Fast Extraction for the CNGS Facility | extraction, kicker, damping, feedback | 1757 | ||
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The SPS LSS4 fast extraction system will serve both the anti-clockwise ring of the LHC and the long baseline neutrino (CNGS) facility. For the latter two extractions spaced by 50 ms, each affecting half of the ring, are foreseen. During the shutdown 2003-2004 the performance of the fast extraction kickers was improved in order to match more closely the specifications for the kicker pulse shape required for the CNGS and LHC extractions. The rise and fall times were significantly reduced, as well as the post-pulse kick ripple. However, the latter remains outside specifications and oscillations are induced in the leading bunches of the batch remaining in the machine at the moment of the first extraction. While further improving the characteristics of the kicker pulse shape, the possibility of damping the beam oscillations using the transverse feedback system has been explored. We report on the recent pulse form improvements and results of beam tests.
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| FPAT081 | A New Version of SixTrack with Collimation and Aperture Interface | collimation, simulation, proton, 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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