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| MOPKF009 | Photoinjector Studies for the BESSY Soft X-ray FEL | gun, emittance, linac, electron | 315 | ||
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A linac driven soft X-Ray FEL facility has been proposed at BESSY with the aim to produce high brilliance photon beams within the energy range of 20eV to 1keV. The driver linac is based on superconducting (sc) L-Band rf-technolgy to enable cw operation of the FEL. As the electron beam emittance directly influence the photon beam characteristics, transverse slice emittances of 1.5pimmmrad are envisaged as a target goal. This demands for a high brilliance laser driven photoinjector rf-gun as electron source. For the first years of operation it is intended to use well known normal conducting (nc) L-Band rf-gun technology thereby restricting the macropulse repetition rate to 1 kHz to cope with the thermal power dissipation. At a later stage the nc rf-gun shall be replaced by a sc rf-gun, which is favoured conceptually as it allows to generate outmost flexible bunch patterns according to the needs of the experiments by fully exploiting the capabilities of the sc linac. This paper details the design considerations for a high power nc rf-gun complemented by results of beam dynamic studies up to the exit of the booster linac using ASTRA. Perspectives for the use of a sc photoinjector gun cavity are addressed.
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| MOPKF060 | Space Charge Effects for the ERL Prototype at Daresbury Laboratory | emittance, space-charge, linac, quadrupole | 446 | ||
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Daresbury Laboratory is currently building an Energy Recovery Linac Prototype (ERLP) that will operate at a beam energy of 35 MeV. In this paper we examine the Space Charge effects on the beam dynamics in the ERLP injector line. This is done in two distinct ways. The first is based on an analytic formula derived by Vinokurov through the envelope equations and a Kapchinsky-Vladimirsky (KV) distribution. This formula gives a rough estimate of the space charge effects in the case that no quadrupoles or dipoles are present in the injector line. The second estimate is given by the multi-particle tracking code ASTRA for the whole injector line both with and without quadrupoles. Both methods are compared and are found to be in good agreement. Typical examples of injector lines are given together with specific calculations for the ERLP.
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| MOPKF066 | Magnetic Design of a Focusing Undulator for ALPHA-X | undulator, electron, permanent-magnet, quadrupole | 464 | ||
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ALPHA-X is a four-year project shared between several research groups in the UK to build a laser-plasma accelerator and produce coherent short-wavelength radiation in an FEL. The FEL undulator will be a 1.5m long, 100 period permanent magnet device with a minimum gap of 3.5mm and a peak field of 0.7T. To focus the beam inside the undulator, several schemes were examined. In the scheme that was selected, the magnet blocks are designed so that the pole face is an approximation of a parabola. This focuses the beam horizontally and vertically. The magnetic design of the undulator is complete; design of the support structure is well under way. Test pieces have been built to ensure that the clamping arrangement is strong enough to cope with the magnetic forces involved. The complete undulator will be built in late 2004 at Daresbury Laboratory, and tested on-site in the new magnet test facility.
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| MOPKF071 | Study of Row Phase Dependent Skew Quadrupole Fields in Apple-II type EPUs at the ALS | quadrupole, polarization, undulator, lattice | 479 | ||
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Since about 5 years, Apple-II type Elliptically Polarizing Undulators (EPU) have been used very successfully at the ALS to generate high brightness photon beams with arbitrary polarization. However, both EPUs installed so far cause significant changes of the vertical beamsize, especially when the row phase is changed to change the polarization of the photons emitted. The effect has been measured in detail and turned out to be caused by a row phase dependent skew quadrupole term in the EPUs. Magnetic measurements revealed the same effect for the third EPU to be installed later this year. All measurements to identify and quantify the effect with beam will be presented, as well as results of magnetic bench measurements and numeric field simulations.
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| MOPLT047 | Lattice Design Study for HESR | quadrupole, lattice, sextupole, target | 653 | ||
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The important feature of High Energy Storage Ring is the combination of phase space cooled beams with internal targets, which allows to reach high luminosities up to 2*1032cm-2s-1. However, the requirement to have the strongly focused beam on the target causes the high chromaticity value on the target straight section and as in result to the squeezing of dynamic aperture after sextupole correction of the chromaticity. Simultaneously, the momentum-compaction factor is one of the most important characteristics of an accelerator, which defines the collective instability threshold. Therefore, the HESR lattice has to have the following features: low or negative momentum compaction factor, dispersion free straight sections, convenient method to correct the chromaticity by the sextupoles, sufficiently large dynamic aperture. In this work we develop lattice, which meets all these requirements for HESR.
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| MOPLT056 | Feasibility Study for a Very High Luminosity Phi-factory | luminosity, lattice, betatron, radiation | 680 | ||
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Particle factories are facing their future by looking at the possibility of upgrading the luminosity by orders of magnitude. The upgrade challenges are more stringent at lower energies. Double symmetric rings, enhanced radiation damping, negative momentum compaction and very short bunches at the collision point are the main features of a phi-factory feasibility study presented in this paper. The bunch length of few millimeters at the crossing point of the beams is obtained by applying the Strong RF Focusing principle which provides a modulation of the bunch length along the ring by means of a large momentum compaction factor together with a very high RF gradient. The collider design fits the existing DAFNE infrastructures with completely rebuilt rings and upgraded injection system.
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| MOPLT057 | Proposal of a Strong RF Focusing Experiment at DAFNE | lattice, luminosity, synchrotron, dipole | 683 | ||
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The strong RF focusing is a recently proposed technique to obtain short bunches at the interaction point in the next generation colliders. A large momentum compaction factor together with a very high RF gradient across the bunch provide a modulation of the bunch length along the ring, which can be minimized at the Interaction Point (IP). No storage ring has been so far operated in such a regime, since it requires uncommonly high synchrotron tune values. In this paper we present the proposal of creating the experimental conditions to study the strong RF focusing in DAFNE. The proposed machine lattice providing the required high momentum compaction value, the upgrade of the RF system including the installation of a multi-cell superconducting cavity, the upgrade of the cryogenic plant and a list of the possible beam experiments are illustrated and discussed.
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| MOPLT081 | Low Energy Ion Beam Dynamics in Axisymmetric RF Undulator Linac | linac, ion, undulator, acceleration | 731 | ||
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The ion beam focusing and acceleration in an axisymmetric periodic RF undulator structure is considered. There is suggested that RF field has no a synchronous wave and accelerating force is to be driven by a combination of two non-synchronous waves. The influence of non-synchronous harmonics on ion beam dynamics is studied by means of a smooth approximation. Choice and optimization of RF field harmonics are made to obtain maximal transmission coefficient. The result is verified by a numerical simulation. The comparison with a conventional RF linac, where a synchronous harmonic accelerates a beam and non-synchronous one is focusing a beam, is described. This comparison is suitable for demonstration of the capabilities of an undulator linac.
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| MOPLT142 | Analysis of KEK-ATF Optics and Coupling Using LOCO | coupling, quadrupole, emittance, sextupole | 872 | ||
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LOCO is a computer code for analysis of the linear optics in a storage ring based on the closed orbit response to steering magnets. The analysis provides information on focusing errors, BPM gain and rotation errors, and local coupling. Here, we discuss the details of the LOCO implementation at the KEK-ATF Damping Ring, and report the initial results. Some of the information obtained, for example on the BPM gain and coupling errors, has not previously been determined. We discuss the possibility of using the data provided by the LOCO analysis to reduce the vertical emittance of the ATF beam.
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| MOPLT171 | A Pratical Demonstration of the CRFQ Storage Ring | rfq, proton, injection, storage-ring | 926 | ||
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The Circular Radiofrequency Quadrupole (CRFQ) is a new concept of a storage and accelerator ring for intense beams of light and heavy ions, protons and electrons. It is basically a Linear Radio-Frequency Quadrupole completely bent on a circle. The advantages are expected to be equivalent to those of a Linear RFQ, namely higher beam intensity and smaller beam dimensions. Moreover, it is a more compact device when compared to conventional accelerators. A collaboration was created between Brookhaven National Laboratory, the University of Naples, the University of Sannio, and the INFN-Section of Naples (Italy) for the purpose of developing a proof of principle (PoP) of the CRFQ. During the initial stage the main goal is the demonstration of the curvature effect of the quadrupolar RFQ field. At that purpose, the project is actually conceived of three phases: (i) develop an adequate 30 keV proton source, (ii) design, manufacture and test a linear RFQ section, and (iii) design, manufacture and test a curved RFQ section, both operating at 200 MHz. The linear section acts as a matching with the ion source at one end, and the curved section at the other. The paper discusses mechanical and RF considerations during the design and experiment. The final goal of the collaboration is eventually to build enough curved sections to complete the storage ring where to demonstrate storage of 30 keV protons over long periods of time.
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| MOPLT175 | A Method to Measure the Focusing Properties (R_Matrix) of a Magnet | ion, heavy-ion, dipole, multipole | 935 | ||
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We discuss a method that may be used to measure the focusing properties of a magnet. This method may prove valuable when applied to non-conventional magnets that deviate from the usual dipole magnets or other multipole magnets which are commonly used in a synchrotron. In this category of non-conventional magnets, fall special magnets, which come under the name Snakes. Such magnets are being used in synchrotron accelerators[*,**] to introduce artificial spin resonances to help overcome the intrinsic and/or imperfection spin resonances. This method of measuring the focusing properties of a magnet requires the use of low energy and high rigidity heavy-ions which may be obtained from the BNL Tandem accelerator.In brief the method consists on, injecting low emittance beamlets of lightly stripped heavy ions into a magnet and measuring the coordinates, of these narrowbeamlets, at the entrance and exit of the magnet.From the measurement of these coordinates of the narrowbeamlets we can deduce information on the R matrix and higher order matrix elements that define the focusing properties of the magnet.
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* T. Roser, AIP Conf. Proc. 187 (1988) 1221** H.Huang, et. al. Phys. Rev. Lett. 73 (1994) 2982 |
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| TUPKF017 | Electrons Beam Dynamics of the 100 MeV Preinjector Helios for the SOLEIL Synchrotron | gun, linac, emittance, electron | 997 | ||
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A 100 MeV electron linac is under construction, in order to inject into the booster synchrotron of SOLEIL. The linac is designed to work according to two operation modes : a short pulse mode (2 ns - 0,5 nC) and a long pulse mode (300 ns - 8 nC). Calculation of the beam dynamics, using our selfmade code PRODYN, has been carried out from the gun to the end of the linac. Special care has been taken on the gun design to avoid an overfocusing outcoming beam in order to obtain a final low emittance. Calculations results are given.
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| TUPKF063 | Current Status of the Next Linear Collider X-band Klystron Development Program | klystron, gun, vacuum, collider | 1090 | ||
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Klystrons capable of driving accelerator sections in the Next Linear Collider have been developed at SLAC during the last decade. In addition to fourteen 50 MW solenoid-focused devices and a 50 MW Periodic Permanent Magnet focused (PPM) klystron, a 500 kV 75 MW PPM klystron was tested in 1999 to 80 MW with 3-microsecond pulses, but very low duty. Subsequent 75 MW prototypes aimed for low-cost manufacture by employing reusable focusing structures external to the vacuum, similar to a solenoid electromagnet. During the PPM klystron development, several partners (CPI, EEV and Toshiba) have participated by constructing partial or complete PPM klystrons. After early failures during testing of the first two devices, SLAC has recently tested this design (XP3-3) to the full NLC specifications of 75 MW, 1.6 microseconds pulse length, and 120 Hz. This 14.4 kW operation came with a tube efficiency of 50%. The XP3 3 average and peak output power, together with the focusing method, arguably makes it the most advanced high power klystron ever built anywhere in the world. Design considerations and the latest testing results for these latest prototypes will be presented.
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| TUPKF077 | Test Results for a 10-MW, L-band, Multiple-beam Klystron for TESLA | klystron, electron, cathode, gun | 1117 | ||
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The VKL-8301 high-efficiency, multiple-beam klystron (MBK), has been developed for the DESY Tera Electron volt Superconducting Linear Accelerator (TESLA) in Hamburg, Germany. The first prototype is built and will be tested in March of 2004. The prototype has been designed for long-life operation by utilizing the benefits inherent in higher-order mode (HM) MBKs. The primary benefit of HM-MBKs is their ability to widely separate individual cathodes. One of the major obstacles to the success of this approach is the design of the off-axis electron beam focusing system, particularly when confined-flow focusing is desired. We will show simulated and measured data which demonstrates a solution to this problem. High power test results will also be shown.
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| TUPLT028 | Development of Finger Drift Tube Linacs | booster, quadrupole, rfq, multipole | 1204 | ||
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At higher particle energies the efficiency of RFQs decreases and DTL structures in combination with magnetic quadrupoles are used. One approach at IAP is the combination of RFQ and DTL. To compensate the defocusing effects of a DTL structure, the accelerating gaps of a spiral loaded cavity were equiped with small focusing fingers. These fingers arranged in a quadrupole symmetry provide an additional focusing field component. The beam dynamics of such a cavity has been studied with PARMTEQ. Simulations of the rf properties have been done using microwave studio. A prototype of a spiral loaded cavity with finger drift tubes has been built and low power measurement were made. Results of the calculations as well as low level and bead pertubation measurements are presented in this contribution.
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| TUPLT034 | Beam Dynamics Studies for the Low Energy Section at MAFF | rfq, emittance, quadrupole, ion | 1219 | ||
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For the LINAC of the Munich accelerator for fission fragments (MAFF) a new scheme for the low energy section has been proposed in order to fulfill new experimental requirements, such as time spacing between bunches and low longitudinal emittance. The proposed solution consists in a combination of an external multi-harmonic buncher with a "traditional" RFQ with a shaper and an adiabatic bunching section included where the employment of the external buncher is upon request from the experiment. The matching section downstream the RFQ has been re-designed in order to allow room for the installation of a beam cleaning section and to a proper injection into the following DTL. Details about the optics and beam dynamics studies of the low energy section are presented in this paper.
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| TUPLT039 | An Electrostatic Quadrupole Doublet with an Integrated Steerer | quadrupole, storage-ring, ion, coupling | 1234 | ||
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Electrostatic storage rings have proven to be a valuable tool for atomic and molecular physics Due to the mass independence of the fields in the bending and focusing elements, different kinds of ions with the same charge/energy ratio from light protons to very heavy biomolecules, can be stored with the same field setup. The transverse dimensions of the circulating beam are controlled by electrostatic quadrupole doublets or triplets. It is essential that the fields in these lenses can be adjusted independently one from another to allow an exact control of the stored ions. In this paper, first an overview of the principle of electrostatic lenses is given. After a short discussion of fringe field effects, the results of field calculations are presented and the final layout of an electrostatic quadrupole doublet with an integrated steerer as it will be used in future electrostatic storage rings in Frankfurt and Heidelberg is discussed.
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| TUPLT066 | Study of a High-current 176 MHz RFQ as a Deuteron Injector for the SPES Project | rfq, quadrupole, dipole, simulation | 1306 | ||
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The SPES project, aimed at the construction of a RIB facility at LNL, is initially based on the use of a primary proton beam, but it foresees a future development based on the usage of deuterons and light ions. In this article we report about the preliminary study of a 176 MHz RFQ to be used as an injector for such kind of beams. The structure explored foresees a ?four ladder? symmetric resonator, built in brazed copper. In particular beam dynamics, electrodynamics design and preliminary thermo-structural analysis of the cavity is presented.
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| TUPLT071 | A 5 MeV Electron Linac for Radiation Processing | electron, radiation, cathode, linac | 1315 | ||
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In recent years, radiation processing is rapidly growing in various field of industrial treatments and scientific research as a safe, reliable and economic technique. To match the requirements of several applications, a 5 MeV, 1 kW electron linac has been developed at the Dipartimento di Fisica (Università di Messina), in collaboration with the ENEA Accelerators Group (Frascati- Rome). This self- containing standing wave accelerator, driven by a 3 GHz, 2.5 MW Magnetron, has been designed, by means of the SUPERFISH and PARMELA codes, in such a way as to obtain an autofocusing structure, that will be used to develop a transportable system for 'in-situ' industrial radiography and X-ray digital tomography. For this accelerator, compact pulse forming circuits have been properly developed for the magnetron and the cathode, and pulse frequency can be varied ranging from 1 to 300 Hz, thus allowing the study of several applications of radiation processing. Main features of the accelerating structure, as well as beam spot dimensions, surface dose distribution and electron beam energy range will be described.
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| TUPLT081 | Lattice Design of Large Acceptance FFAGs for the PRISM Project | optics, emittance, lattice, synchrotron | 1345 | ||
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In order to realize a super muon beam that combines high-intensity, low-energy, narrow energy-spread and high purity, the PRISM project has been proposed. In this project, a FFAG ring is used as a phase rotator. In this paper, a method of designing the PRISM-FFAG lattice will be described. The PRISM-FFAG has to have both of large transverse acceptance and large momentum acceptance to achieve high intensity. Furthermore, long straight sections to install RF cavities are required to obtain a high surviving ratio of the muon. Therefore, the PRISM-FFAG requires its magnets to have large aperture and small opening angle. In such magnets, not only nonlinear effects but also magnetic fringing field are important to study the beam dynamics of FFAGs. Although using realistic 3D magnetic field maps made with programs such as TOSCA is the best solution to study the FFAG dynamics, it takes long time to make such field maps. On a design process of the PRISM-FFAG, quasi-realistic 3D magnetic field maps, which are calculated applying spline interpolation to POISSON 2D field, were used to study the beam dynamics. A program based on GEANT3.21 was used for particle tracking.
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| TUPLT111 | RF Focusing of Low-Charge-to-Mass-Ratio Heavy-Ions in a Superconducting Linac | linac, ion, emittance, superconducting-RF | 1405 | ||
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A post-accelerator of radioactive ions (RIB linac) must produce high-quality beams over the full mass range, including uranium, with high transmission and efficiency (P.N. Ostroumov and et al., Proc. of the PAC2001, p. 4080.). The initial section of the RIB linac is a low-charge-to-mass-ratio superconducting RF linac which will accelerate any ion with q/A>=1/66 to ~900 keV/u or higher. This section of the linac consists of many interdigital cavities operating at –20 degree synchronous phase and focusing can be provided by SC solenoids following each cavity. For the charge-to-mass ratio q/A=1/66 a proper focusing can be reached with the help of strong SC solenoid lenses with magnetic fields up to 15 T. These state-of-the-art solenoids are expensive. A possible lower cost alternative focusing method based on the combination of low-field SC solenoids and RF focusing is proposed and discussed in this paper.
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| TUPLT147 | Multiple-charge-state Beam Steering in High-intensity Heavy-ion Linacs | linac, emittance, heavy-ion, beam-losses | 1476 | ||
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An algorithm suitable for correction to steering of multiple-charge-state beams in heavy-ion linacs operating at high currents has been developed [*]. It follows a four-dimensional minimization procedure that includes coupling of the transverse beam motions. A major requirement is that it obeys the restricted lattice design imposed by the acceleration of multiple-charge-state heavy-ion beams [**]. We study the algorithm efficiency in controlling the beam effective emittance growth in the presence of random misalignments of cavities and focusing elements. Limits on misalignments are determined by quantifying beam losses and effective steering requirements are selected by examining several correcting schemes within the real-state constraints. The algorithm is used to perform statistically significant simulations to study beam losses under realistic steering.
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* E. S. Lessner and P. N. Ostroumov, Proc. Part. Accel. Conf. (2003)** P. N. Ostroumov, Phys. Rev. STAB Vol. 5, 0030101 (2002) |
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| TUPLT156 | Progress in Ideal High-intensity Unbunched Beams in Alternating Gradient Focusing Systems | electron, quadrupole, emittance, simulation | 1494 | ||
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A persistent challenge in high-intensity accelerator design is the optimization of matching conditions between a beam injector and a focusing system in order to minimize non-laminar flows, envelope oscillations, emittance growth, and halo production. It has been shown [*] that the fluid motion of a thin space-charge dominated beam propagating through a linear magnetic focusing channel consisting of any combination of uniform or periodic solenoidal fields and alternating gradient quadrupole fields can be solved by a general class of corkscrewing elliptic beam equilibria. The present work extends this discussion to asymmetric PPM focusing and derives conditions under which a uniform density elliptical beam can be matched to such a focusing channel by considering the fluid equilibrium in the paraxial limit. Methods of constructing such a beam are also discussed, with particular attention devoted to analytic electrode design for Pierce-type gun diodes of elliptical cross-section. Several applications are discussed, including heavy-ion fusion and a high-efficiency ribbon beam microwave amplifier for accelerator applications.
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* C. Chen, R. Pakter, R. Davidson, "Ideal Matching of Heavy Ion Beams," Nucl. Inst. And Methods, A 464 (2001) p. 518-523 |
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| WEPKF030 | The Storage Ring Magnets of the Australian Synchrotron | quadrupole, sextupole, dipole, storage-ring | 1666 | ||
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A 3 GeV Synchrotron Radiation Source is being built up in Melbourne, Australia. The storage ring has a circumference of 216 m and has a 14 fold DBA structure. For the storage ring the following magnets are required: 28 gradient dipoles, with B = 1.3 T, B’ = 3.35 T/m, 56 quadrupoles with a gradient of B’ = 18 T/m, 28 quadrupoles with a gradient of 9 T/m, 56 sextupoles with d2B/dr2 = 320 T/m2 and 42 with 150 T/m2. The design of pole faces was done by scaling the SPEAR III pole face to the required gap and bore of the ASP storage ring magnets. The sextupoles will be equipped with coils for horizontal and vertical correction and for a skew quadrupole. The design of the magnets and the calculated magnetic properties will be presented.
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| WEPKF060 | Bending Magnets for the SAGA Storage Ring: Manufacturing and Magnetic Measurements | dipole, storage-ring, multipole, electron | 1738 | ||
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The paper describes the design, the manufacture and the magnetic measurement of the dipole bending magnets (BM) for SR Source storage ring (prefecture SAGA, Japan) carried out in BINP, Novosibirsk, Russia. The requirement was to create the laminated C-shape BMs with the 3.2 m radius and parallel edges. The magnetic field homogeneity must be not worth than ±2? 10-4 inside the working area: H = 30+40mm and V = ±20mm at 0.26T (250 MeV), and H = ± 28mm and V = ±20mm at 1.46 T (1.4GeV). The BMs were designed on the basis of the 2-D 3-D modeling taking into account the laminated core. The BMs yokes were produced with the help of the technology of the high temperature gluing. The computer simulations are in a good agreement with the magnetic measurements. The main parameters of the magnetic fields satisfy to the requirements and are presented. The features of the design, manufacturing and precise magnetic measurements of SAGA BMs are discussed.
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| WEPKF070 | Design Issues for the Superconducting Magnet that goes around the Liquid Hydrogen Absorber for the Muon Ionization Cooling Experiment (MICE) | vacuum, magnet-design, superconducting-magnet, radiation | 1765 | ||
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This report describes the design issues that are associated with a superconducting focusing solenoid that goes around a liquid hydrogen absorber for the Muon Ionization Cooling Experiment (MICE) proposed for the Rutherford Appleton Laboratory. The solenoid consists of two superconducting coils that may operated at the same polarity or at opposite polarities. As a result, the coils and their support structure must be designed to carry a 300 ton inter-coil force that is forcing the coils apart along their axis. The basic design parameters for the focusing magnet are discussed. The magnet and its cryostat are designed so that the absorber can be assembled and tested before installation into the pre-tested focusing solenoid. A safety requirements for MICE dictate that the insulating vacuum for the superconducting magnet be separated from the insulating vacuum for the absorber and that both vacuum be separated from the experiment vacuum and the vacuum within adjacent RF cavities. The safety issues associated with the arrangement of the various vacuums in the MICE focusing modules are presented. The effect of magnet operation and magnet quench on the liquid hydrogen absorber is also discussed.
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| WEPLT005 | Building Truncated Taylor Maps with Mathematica and Applications to FFAG | closed-orbit, quadrupole, lattice, dipole | 1822 | ||
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Lie algebra tools coded directly in Mathematica have been used to compute the off-momentum closed orbit, orbit length and horizontal tune of Fixed Field Alternating Gradient (FFAG) lattices proposed for muon acceleration. The sample FFAG cell considered consists of quadrupoles and alternating gradient magnets. A high order Taylor map is needed, valid over a wide momentum range. We describe the algorithm and Mathematica operators needed to create and concatenate individual element maps (presented as Lie exponential operators) and compare our results with those obtained with a high-order differential algebra code – COSY. The speed achieved is inferior to the differential algebra method.
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| WEPLT009 | Dynamics of the Electron Pinch and Incoherent Tune Shift Induced by Electron Cloud | electron, simulation, proton, injection | 1834 | ||
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When a proton bunch passes through an electron cloud, the cloud electrons are attracted by the beam electric field; their density strongly increases near the beam centre. This gives rise to an incoherent proton tune shift, which depends on the longitudinal and radial position within the bunch. We present an analytical description of the 'electron pinch' and the resulting proton tune shift, for a circular symmetry and a Gaussian cloud. Benchmarking and extending the results by computer simulations, we explore the effects of different longitudinal beam profiles and of the nonlinear transverse force.
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| WEPLT046 | Localizing Impedance Sources from Betatron-phase Beating in the CERN SPS | impedance, quadrupole, betatron, optics | 1939 | ||
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Multi-turn beam-position data recorded after beam excitation can be used to extract the betatron-phase advance between adjacent beam position monitors (BPMs) by a harmonic analysis. Performing this treatment for different beam intensities yields the change in phase advance with current. A local impedance contributes to the average tune shift with current, but, more importantly, it also causes a mismatch and phase beating. We describe an attempt to determine the localized impedance around the SPS ring by fitting the measured betatron phase shift with current at all BPMs to the expected impedance response matrix.
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| WEPLT047 | A Test Suite of Space-charge Problems for Code Benchmarking | simulation, space-charge, proton, quadrupole | 1942 | ||
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A set of problems is presented for benchmarking beam dynamics codes with space charge. As examples, we show comparisons using the IMPACT, MaryLie/IMPACT, and MAD9P codes. The accuracy and convergence of the solutions as a function of solver algorithms, simulations parameters such as number of macro particles, grid size, etc. are studied.
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| WEPLT067 | Space Charge Problem in Low Energy Super-conducting Accelerator | space-charge, linac, resonance, simulation | 2002 | ||
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At present the super-conducting option of linear accelerators is considered for low energy, and new type of RF cavities is considered for this purpose. However, together with electrodynamics problems we should solve the transverse stability problem, since in structures with external focusing elements the focusing period is longer, and in higher accelerating field the defocusing factor increases as well. In this paper we consider the transverse stability problem, taking into account the non-linear space charge problem. The fundamental mechanism of hallo creation in super-conducting linear accelerators is investigated to minimize the particle losses. The theoretical results are supported by numerical simulation.
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| WEPLT071 | Longitudinal Resonances and Emittance Growth Using QWR/HWR in a Linac | linac, resonance, emittance, transverse-dynamics | 2014 | ||
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In the frame of the SPIRAL II project at GANIL, we present an analytical approach allowing us to understand in a simple way the longitudinal behaviour of a beam , transmitted in bunching mode or accelerated in a Linac designed with QWR or HWR cavities. In particular, we make appear the strong relationship with the Henon map properties.
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| WEPLT079 | Non Linear Beam Dynamics and Lifetime on the SOLEIL Storage Ring | resonance, undulator, insertion, insertion-device | 2035 | ||
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The incidence of several non-linear effects on the energy acceptance and beam lifetime has been investigated, using the BETA and TRACY II tracking codes. The effect of all magnets multipolar components has been checked on the working point (18.20; 10.30), especially the decapolar component induced by the H-corrector. The dipolar field, which is created by additional coils in the sextupoles, generates a significant decapolar component which, associated to the distributed dispersion, can reduce significantly the dynamic acceptance at large energy deviations. This effect depends on the natural closed orbit to be corrected: corrector strengths and cross talk between the different decapolar components. Moreover, the sensitivity to the number of correctors, used for correction, has been evaluated. The effect of insertions devices has also been studied, integrating field maps generated by the RADIA code into the tracking codes. With undulators, such as an in-vacuum U20 and an Apple II type HU80 (with different polarization modes), it was shown that the transverse field in-homogeneity and the focusing effects generating beta-beat can affect severely the energy acceptance and the beam lifetime because of resonance excitation.
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| WEPLT080 | Study of Resistive-wall Effects on SOLEIL | impedance, single-bunch, vacuum, synchrotron | 2038 | ||
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The presence of low-gap chambers for insertion devices, along with a relatively small vertical gap of 25 mm chosen for the standard vacuum chambers, implies a significant influence of the resistive-wall on the beam in the future SOLEIL storage ring. A systematic approach was taken to quantify the net contribution by taking into account all local variations of the non-circular chamber cross-sections as well as beta functions. Low multibunch instability thresholds were found in both transverse planes, indicating the necessity of cures, by means of transverse feedback and/or chromaticity shifts. An effort was made to evaluate the effect of metallic coating, particularly that of NEG, which was adopted in all straight sections. The dependence on both resistivity and thickness of NEG was followed. It is found that, the NEG coating nearly doubles the reactive part of the impedance in the frequency range seen by the beam. Implication on the reduction of the transverse mode-coupling instability threshold is discussed. Incoherent tune shifts arising from the non-circular chamber cross-section were also evaluated, including a non-negligible NEG contribution in the short-range wakes.
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| WEPLT118 | Performance of the TU/e 2.6 Cell Rf-photogun in the 'Pancake' Regime | plasma, simulation, space-charge, acceleration | 2128 | ||
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The 2.6 cell rf-photogun currently in operation at Eindhoven University of Technology has been designed as a booster for a 2 MeV semi-DC accelerator with a field of 1 GV/m. In this paper we present GPT simulation results of the TU/e gun, operated without its pre-accelerator, in the low-charge short-pulse regime. The main part of the paper describes detailed calculations of bunch lengthening due to path-length differences and space-charge effects, making use of high-precision field-maps and the newly developed 3D mesh-based space-charge model of GPT. It is shown that with the present set-up bunches can be produced that are well suited for injection into a planned experiment for controlled acceleration in a plasma-wakefield accelerator.
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| WEPLT146 | Mismatch Oscillations in High-current Accelerators | quadrupole, emittance, ion, vacuum | 2179 | ||
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Strong space charge challenges the designers of modern accelerators such as those used in Heavy Ion Inertial Fusion. Simple, accurate design tools are useful for predicting beam behavior, such as phase advances and envelope oscillation periods, given the beam emittance and charge and the lattice parameters. Along with the KV beam model, the smooth approximation [*] is often used. It is simple but not very accurate in many cases. Although Struckmieir and Reiser [**] showed that the stable envelope oscillations of unbalanced beams could be obtained accurately, they used a hybrid approach where the phase advances σ0 and σ were already known precisely. When starting instead with basic quantities–quadrupole dimensions, field strength, beam line charge and emittance–the smooth approximation formulas give substantial errors (10% or more). We previously described an integration method [***] for matched beams that yields fairly simple third-order formulas for σ0, σ, beam radius and ripple. Here we extend the method to include small-amplitude mismatch oscillations. We derive a simple modification of the smooth approximation formulas and show that it improves the accuracy of the predicted envelope frequencies significantly–for example, by a factor of five when σ0 is 83 degrees.
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* M. Reiser, Particle Accelerators 8, 167 (1978) ** J. Struckmeier and M. Reiser, Particle Accelerators 14, 227 (1984)*** O. A. Anderson, Particle Accelerators 52, 133 (1996) |
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| WEPLT149 | Image-charge Effects on the Beam Halo Formation and Beam Loss in a Small-aperture Alternating-gradient Focusing System | beam-losses, lattice, quadrupole, heavy-ion | 2188 | ||
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The image-charge effects on an intense charged-particle beam propagating through an alternating-gradient focusing channel with a small aperture, circular, perfectly conducting pipe are studied using a test-particle model. For a well-matched elliptical beam with the Kapchinskij-Vladimirskij (KV) distribution, it is found that halo formation and beam loss is induced by nonlinear fields due to image charges on the wall. The halo formation and chaotic particle motion dependent sensitively on the system parameters: filling factor of the quadrupole focusing field, vacuum phase advance, beam perveance, and the ratio of the beam size to the aperture. Furthermore, the percentage of beam loss to the conductor wall is calculated as a function of propagating distance and aperture. The theoretical results are compared with PIC code simulation results.
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| WEPLT157 | Single-bunch Electron Cloud Effects in the GLC/NLC, US-cold and TESLA Low Emittance Transport Lines | electron, emittance, positron, collider | 2209 | ||
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In the beam pipe of the Beam Delivery System (BDS) and Bunch Compressor system (BCS) of a linear collider, ionization of residual gasses and secondary emission may lead to amplification of an initial electron signal during the bunch train passage and ultimately give rise to an electron-cloud. A positron beam passing through the linear collider beam delivery may experience unwanted additional focusing due to interaction with the electron cloud. This typically leads to an increase in the beam size at the interaction point (IP) when the cloud density is high. Interaction with the electron cloud in the bunch compressor could also potentially cause an instability. This paper examines the severity of the electron cloud effects in the BCS and BDS of both the GLC/NLC and US-Cold linear collider design through the use of specially developed simulation codes. An estimate of the critical cloud density is given for the BDS and BCS of both designs.
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| WEPLT174 | Higher Order Hard Edge End Field Effects | multipole, lattice, chromatic-effects, dynamic-aperture | 2236 | ||
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In most cases, nonlinearities from magnets must be properly included in tracking and analysis to properly compute quantities of interest, in particular chromatic properties and dynamic aperture. One source of nonlinearities in magnets that is often important and cannot be avoided is the nonlinearity arising at the end of a magnet due to the longitudinal variation of the field at the end of the magnet. Part of this effect is independent of the shape of the end. It is lowest order in the body field of the magnet, and is the result of taking a limit as the length over which the field at the end varies approaches zero. This is referred to as a hard edge" end field. This effect has been computed previously to lowest order in the transverse variables. This paper describes a method to compute this effect to arbitrary order in the transverse variables, under certain constraints. The results of using this hard edge model are compared with performing the computation with finite-length end fields, as well as to the lowest-order hard-edge end field model.
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| THPKF052 | The Project of Accelerator Mass-Spectrometer at BINP | ion, ion-source, target, tandem-accelerator | 2389 | ||
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The project of creation of first Russian accelerator mass-spectrometer at BINP is described. The scheme of spectrometer includes two types of ion sources (sputter and gaseous ones), low energy beam line with analysers, electrostatic tandem accelerator with accelerating voltage up to 2 MV and magnesium vapours stripper and also includes the high energy beam line with analysers. The results of first experiments with ion sources are given also.
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| THPLT037 | Investigation of Numerical Noise in PIC-Codes | simulation, space-charge, accumulation, emittance | 2562 | ||
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For a detailed analysis of the dynamics of space charge dominated beams a combination of Particle-in-Cell methods with efficient FDTD schemes is widely used. Besides the calculation of the forces acting on the particles the interaction of the beam itself with the surrounding geometries is taken into account. A drawback of this method is its sensitivity to numerical noise in the spectral range nearby the grid cutoff frequency. In this paper we will present results of detailed studies of the impact of the bunch shape on the level of the numerical noise. Furthermore an a priori scheme for efficient noise suppression is derived which does not affect the FDTD update algorithm.
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| THPLT050 | End to End Simulations of the RX2 Beam Transport | target, simulation, linac, cathode | 2595 | ||
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RX2 is a project aiming to produce a high flux of X-rays for radiography purpose. We proposed an RF linac using a DC photo-injector producing 20 bunches with 100nC each at 352 MHz. The beam is then injected in 4 RF superconducting cavities and accelerated to 40 MeV. It is then focused on a target producing X-rays. Here is presented the design, the specificities, and the beam simulations from the cathode to the target by coupling 2 multiparticle codes : PARMELA and PARTRAN.
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| THPLT054 | Emittance Diluition due to 3D Perturbations in RF Photoinjectors. | emittance, cathode, space-charge, extraction | 2607 | ||
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The predictions from different simulation codes are compared to investigate the effects of non axis-symmetric conditions, fluctuations in cathode's quantum efficiency and other sources of dishomogeneities in the performances of a typical RF photoinjector. The layout includes a RF gun and a focusing solenoid in a configuration aimed at minimizing the emittance growth due to space charge effects.
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| THPLT062 | Alternating-phase-focused Linac for an Injector of Medical Synchrotrons | linac, rfq, emittance, medical-accelerators | 2631 | ||
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Tumor therapy using Heavy Ion Medical Accelerator in Chiba (HIMAC) has been made over ten years at National Institute of Radiological Sciences (NIRS). Due to the successful clinical results, the project on developing compact medical accelerators for the tumor therapy has been started. To design these compact facilities, the size of a linac as well as the construction and operation costs is important. To satisfy these requirements, we propose Alternating-Phase-Focused (APF) linac using an Interdigital H-mode cavity. Since the axial and radial focusing of beam is made just with the acceleration rf field, no additional focusing elements is needed for the APF linac. This feature would make the costs lower than those of conventional linacs. The practical design of the APF linac will be presented.
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| THPLT079 | The Study of APF-IH Linac | linac, ion, acceleration, proton | 2679 | ||
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We have manufactured the IH linac with Alternating Phase Focus as the test machine of medical accelerator injection. It will accelerate C4+ ion up to 2MeV/u from 40 keV/u, the tank length is around 1.5m, operation frequency is 100MHz. Furthermore, We have succeeded the acceleration test using proton with simple acceleration system consist of P.I.G. ion source, bending magnets and focus lenses, less than 5m long. Otherwise, We have been making the program of beam dynamics with the results of the electro-magnetic simulation soft (Micro-Wave-Studio,OPERA-3D), it has the merit of easily to calculate the 3D- beam dynamics in the tank. We will report the some results of the test and the beam simulation and the comparisons.
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| THPLT089 | MATLAB Based TPSA Toolbox for the Particle Mapping Through Three-dimensional Magnetic Fields | insertion, insertion-device, storage-ring, quadrupole | 2703 | ||
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Based on the object-oriented programming of MATLAB, a truncated power series algebra (TPSA) toolbox has been developed. The TPSA toolbox as a differential algebra has been applied to realize the algorithm of particle mapping through three-dimensional magnetic field configurations. The capability of symbolic calculation by using this MATLAB-based TPSA toolbox can be used for the theoretical simulation and modeling in accelerator physics. Associated with the use of MATLAB in the control of machines, one can derive the real machine with a virtual machine model built in MATLAB. In this paper, the method of symplectic mapping of three-dimensional magnetic fields is introduced and the structure of TPSA toolbox is presented. Applications of TPSA toolbox in the symplectic mapping of three-dimensional magnetic fields are demonstrated as well.
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| THPLT110 | Modelling of Accelerating Structures with Finite-difference Time-domain Method | simulation, acceleration, electromagnetic-fields | 2742 | ||
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A finite-difference time-domain (FDTD) method is very popular for electromagnetic field modeling. The practical interest in the method is the ability to calculate fields in time domain at any time point in the accelerating structure. That is to say the FDTD method is able to model transient process taking into account the peculiarity of RF power input device. A FDTD approach for modeling of alternate phase focusing structure is presented in this paper. The modeling of lossy metals is a problem in classical formulation of FDTD method. This matter is investigated and one of the solutions is presented in this paper. There are some problems of signal processing when using time-domain method for resonant structure modeling. The matters of mode determination are also investigated and presented in this paper. The simulation results are compared with experimental data.
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