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sextupole

      
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TUPLT076 Optimization of Sextupole Strengths in a Storage Ring for Top-up Operation injection, booster, laser, synchrotron 1330
 
  • H. Tanaka, T. Ohshima, K. Soutome, M. Takao, H. Takebe
    JASRI/SPring-8, Hyogo
  In top-up operation of a light source, electron or positron beams are frequently injected to keep the stored current constant. Closing an injection bump orbit is thus critically important not to disturb precise experiments. However, there are sextupole magnets inside the injection bump in the SPring-8 storage ring and the bump never closes all over the bump amplitude due to the sextupole nonlinearity. To solve the problem, we proposed a scheme based on minimum condition for the injection bump leakage. The scheme only restricts the sextupole strengths within the bump. Introduction of other sextupole families outside the bump can enlarge the dynamic aperture (DA) of the ring with keeping the minimum leakage. To find the best solution, we optimized the sextupole strengths changing the number of sextupole family as a parameter. The simulation shows that addition of two sextupole families sufficiently enlarges DA. Cabling of the sextupole magnets was partly changed in the summer 2003 and the effects of the strength optimization on the bump leakage, injection efficiency and beam lifetime has been investigated experimentally. We present the obtained results compared with the simulations.  
 
TUPLT077 R&D Status of the Fast Extraction Kicker Magnets for the KEK/JAERI 50 GeV Synchrotron extraction, injection, booster, proton 1333
 
  • Y. Shirakabe, Y. Arakaki, T. Kawakubo, Y. Mori, S. Murasugi, E. Nakamura, I. Sakai, M. Tomizawa
    KEK, Ibaraki
  The 50 GeV proton synchrotron composes the final stage of the high intensity proton accelerator complex now on construction at JAERI/Tokai site as a joint project by KEK and JAERI. In this ring, the proton beam is accelerated from 3 GeV to 50 GeV, and delivered to the experimental facilities through the fast and slow extraction lines. The distinctive feature of the fast extraction line is that the bipolar extraction function will be provided. In normal operations, the beam is extracted toward the inner side of the ring and transported to the facility for the long baseline neutrino oscillation experiment using the Super-Kamiokande detector. In case of emergency, for example, quenches of the superconducting magnets of the neutrino line or malfunctioning of the ring RF systems, the beam is extracted toward the outer side of the ring and sent directly to the abort line with a beam dump at the end. In the current kicker design, the bipolar function will be achieved by the Symmetric Blumlein PFN (SBPFN) system with two switches on both ends. The designed parameters of the fast extraction kicker magnets and the recent hardware R&D status will be described in this paper.  
 
TUPLT078 Study of Impedances and Instabilities in J-PARC extraction, injection, booster, laser 1336
 
  • T. Toyama, K. Ohmi
    KEK, Ibaraki
  • Y. Shobuda
    JAERI/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  J-PARC consists of two high intensity proton rings with energies of 3 GeV and 50 GeV. Longitudinal impedances and instabilities, which are caused by beam chamber, cavities, kicker magnets and others, are mainly discussed in this paper.  
 
TUPLT079 Opposite Field Septum Magnet System for the J-PARC 50GeV Ring Injection septum, injection, booster, laser 1339
 
  • I. Sakai, Y. Arakaki, K. Fan, Y. Mori, M. Muto, Y. Saitou, Y. Shirakabe, M. Tomizawa, M. Uota
    KEK, Ibaraki
  • K. Gotou, Y. Morigaki, A. Nishikawa, M. Takahashi
    IHI/Yokohama, Kanagawa
  • H. Mori, A. Tokuchi
    NICHICON, Shiga
  For the injection/extraction system of the high energy high intensity proton synchrotrons, high field wide aperture thin septum magnets are required. To solve these tight problems, new design concept of opposite-field septum magnet system has been invented. The same grade of opposite magnetic field is produced both inside and outside of the septum. The electromagnetic force and leakage flux around the septum conductor are cancelled out each other. The magnetic field of the circulating beam side is compensated by two sub-bending magnets set on the up-stream and down-stream of the opposite fields septum magnet. The beam-separation angle per magnet length is twice as large as normal septum magnet and the two sub-bending magnets also have a role to extend the injection/extraction angle. The newly developed method of the opposite field septum magnets system.is applied to the injection septum magnets for the J-PARC 50-GeV proton synchrotron to get the sufficient injection angle and clearance for low loss injection. The thin septum thickness and larger kick angle at the septum magnet can be obtained by the new system, which is applicable to many accelerators.  
 
TUPLT080 Design of the Beam Transportation Line from the Linac to the 3-GeV RCS for J-PARC septum, booster, linac, laser 1342
 
  • T. Ohkawa
    JAERI, Ibaraki-ken
  • M. Ikegami
    KEK, Ibaraki
  L3BT is beam transportation line from the linac to the 3-GeV RCS which is the part of the accelerators for the High-Intensity Proton Accelerator Facility Project, J-PARC. For the requirement of the beam loss minimization, the L3BT does not only connect the linac to the 3GeV RCS, but also modifies the linac beam to the acceptable shape for the 3-GeV RCS. The required beam parameters at the injection point of the RCS are momentum spread < ±0.1% (100%)and transverse emittance < 4pmm.mrad (99%). To achieve these beam qualities, the L3BT should have following functions: momentum compaction, halo scraping and beam diagnostics. In this paper, results of the design and beam simulation of the L3BT are presented.  
 
TUPLT081 Lattice Design of Large Acceptance FFAGs for the PRISM Project septum, booster, linac, laser 1345
 
  • A. Sato
    Osaka University, Osaka
  • S. Machida
    KEK, Ibaraki
  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.  
 
TUPLT082 Generation of a Femtosecond Electron Beam for Nanoscience and Nanotechnology septum, electron, gun, booster 1348
 
  • J. Yang, T. Kozawa, S. Tagawa, Y. Yoshida
    ISIR, Osaka
  A new S-band femtosecond electron linear accelerator was developed in Osaka University for the study of radiation-induced ultrafast physical and chemical reactions in femtosecond time regions. The femtosecond electron accelerator was constructed with a laser driven photocathode RF gun, a linear accelerator (linac) and a magnetic pulse compressor. The RF gun was driven by a mode-locked Nd:YLF picosecond laser. The electron beam produced by the RF gun was accelerated in the linac with energy modulattion by adjusted the RF phase. The magnetic pulse compression, which was constructed with two 45o-bending magnets and four quadrupole magnets, is a technique to longitudinally focus a charged beam by rotating the phase space distribution in a magnetic field. The picosecond electron pulse, which was generated in the RF gun and accelerated in the linac with energy modulation, was compressed into femtosecond by adjusted the quadrupole magnetic fields. The femtosecond electron pulse is expected for the studies of ultrafast reactions in nano-space.  
 
TUPLT085 J-PARC Construction and its Linac Commissioning septum, electron, gun, booster 1351
 
  • Y. Yamazaki
    JAERI/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  The J-PARC(Japan Proton Accelerator Research Complex) accelerator is under construction in JAERI Tokai site. The beam commissioning will be started there by the end of 2006. Prior to this, the front end of the linac was beam-commissioned in 2003 at KEK. The negative hydrogen beam with a peak current of 30 mA was accelerated up to 20 MeV by the first tank of three DTL's following the 3-MeV RFQ linac. The 324-MHz DTL contains the electro quadrupole magnets with water-cooling channels specially fabricated by means of electroforming and wire-cutting technologies. The construction status of the J-PARC accelerator is also presented.  
 
TUPLT086 A 40MeV Electron Source with a Photocathode for X-ray Generation through Laser-compton Scattering septum, gun, electron, booster 1354
 
  • F. Sakai, N. Nakajyo, Y. Okada, T. Yanagida, M. Yorozu
    SHI, Tokyo
  .3 keV femtosecond X-ray generation through laser-Compton scattering with 14MeV electron source and a TW Ti:sapphire laser was achieved. In order to increase the X-ray energy up to 15 keV for some applications, e.g. protein crystallography, we modified the system to increase electron energy. Electron beams emitted from a S-band RF photocathode are accelerated up to 40MeV with two 1.5m standing-wave linacs. The beams are bended at 90 degree using an achromatic bending system, then focused with a triplet quadrupole-magnet to be interacted with laser pulses. The characteristics of electron beams, emittance, energy and energy dispersion, will be described.  
 
TUPLT087 Deflection Element for S-LSR septum, gun, electron, booster 1357
 
  • M. Ikegami, H. Fadil, A. Noda, T. Shirai, M. Tanabe, H. Tongu
    Kyoto ICR, Uji, Kyoto
  • T. Fujimoto, K. Noda, H. Ogawa, S. Shibuya, T. Takeuchi
    NIRS, Chiba-shi
  • M. Grieser
    MPI-K, Heidelberg
  • H. Okamoto
    HU/AdSM, Higashi-Hiroshima
  Main lattice of the ion storage and cooler ring, S-LSR is composed of 6 dipole and 12 quadrupole magnets. The maximum magnetic field, the radius of curvature and gap height are 0.95 T, 1050 mm and 70 mm, respectively. The field measurement of the dipole magnets has been completed with use of Hall-probe position controlled by driving mechanism composed of stepping motors and ball-screws. In order to cancel out the momentum dispersion, the radial electric field is superposed with the magnetic field. The radial electric field is applied by the electrodes installed into the vacuum vessel set inside the rather limited gap of the dipole magnet. Good field quality is to be realized with use of intermediate electrodes. In the present paper, the results of the magnetic field measurements are presented together with the design of the superposed electric field.  
 
TUPLT088 Beam Cooling at S-LSR septum, gun, booster, ion 1360
 
  • A. Noda, H. Fadil, S. Fujimoto, M. Ikegami, T. Shirai, M. Tanabe, H. Tongu
    Kyoto ICR, Uji, Kyoto
  • M. Grieser
    MPI-K, Heidelberg
  • I.N. Meshkov, E. Syresin
    JINR, Dubna, Moscow Region
  • K. Noda, T. Takeuchi
    NIRS, Chiba-shi
  • H. Okamoto, Y. Yuri
    HU/AdSM, Higashi-Hiroshima
  S-LSR is an ion accumulation and cooler ring with the circumference and maximum magnetic rigidity of 22.589 m and 1.0T.m, respectively. Electron beam cooling will be applied for laser-produced hot ion beam after phase rotation. Electron cooler for S-LSR is now under construction and the beam simulation is also going on. Laser cooling of Mg ion with low energy (35 keV) is also planned in 3-dimensional way with use of Synchro-Betatron coupling.so as to realize ultra cold beam. Cancellation of shear force due to orbit-length difference in the dipole section is to be studied with use of overlapping of the radial electric field inversely proportional to the curvature radius with the uniform vertical magnetic field. Possible experiments to approach to ultra-cold beam is also to be studied by computer simulation  
 
TUPLT089 Status of PEFP 3MeV RFQ Development septum, gun, booster, ion 1363
 
  • Y.-S. Cho, B.-H. Choi, S.-H. Han, J.-H. Jang, Y.H. Kim, H.-J. Kwon, C.-B. Shim
    KAERI, Daejon
  In the PEFP (Proton Engineering Frontier Project), a 350MHz, 3MeV RFQ (Radio Frequency Quadrupole) has been developed and tested. The tuning results showed that the resonant frequency is somewhat higher than 350MHz and other methods in addition to slug tuners should be used to tune the cavity correctly. To check the cavity characteristics, high power RF test has been done. The required peak RF power is 600kW and pulse width, repetition rate for initial test are 100 micro-s, 10Hz respectively. To solve the problems in PEFP RFQ, the upgrade design of 3MeV RFQ has been decided. The main concept of this upgrade design is constant vane voltage profile with the same length of RFQ. The other parameters (350MHz, 3MeV, 20mA) are the same with the previous RFQ. With constant vane voltage profile, fabrication of RFQ can be easier, and with the same mechanical dimension, other parts such as vacuum pumping station can be re-used. In this paper, the test results of the PEFP RFQ, and the details of beam dynamics design/engineering design of upgrade RFQ will be presented.  
 
TUPLT090 Combined Beam Dynamics Study of the RFQ and DTL for PEFP septum, gun, booster, proton 1366
 
  • J.-H. Jang, Y.-S. Cho, H.-J. Kwon
    KAERI, Daejon
  One of the goals of the Proton Engineering Frontier Project (PEFP) is to get 20 MeV proton beams of 20 mA through a 3 MeV RFQ and a 20 MeV DTL. This work is related to the combined beam dynamics study of the low energy proton accelerators in order to test the validity of the connection of the independently designed structures as well as to study the MEBT for beam transportation.  
 
TUPLT091 Fabrication Status of the PEFP 20 MeV DTL septum, gun, booster, ion 1369
 
  • M.-Y. Park, Y.-S. Cho, J.-H. Jang, Y.H. Kim, H.-J. Kwon
    KAERI, Daejon
  The PEFP (Proton Engineering Frontier Project) 20 MeV DTL have been constructed in KAERI site. The fabrication of the first tank is finished and the DT installation is in the process. We choose the pool-type electromagnets as the focusing magnet and 50 DTs will be installed on first tank. We tested the winding schemes of copper coils on the iron core and measured the magnetic field saturation.In this paper, the results of the tank fabrication and quadrupole magnet test are presented.  
 
TUPLT092 Optics and Magnet Design for Proton Beam Transport Line at PEFP septum, proton, gun, booster 1372
 
  • H.-S. Kang, H.S. Han, S.H. Jeong, Y.G. Jung, D.E. Kim, M. Kim, H.G. Lee, T.-Y. Lee, H.S. Suh
    PAL, Pohang
  The PEFP proton linac is designed to have two proton beam extraction lines at the 20-MeV and 100-MeV end, respectively. Each extraction line has 5 to 6 beamlines for proton beam users. The proton beam transport system for users? experiments will be prepared for this purpose. At the beginning, the beam optics for the proton beam transport system is designed with the TRACE code. The optics should be designed so as to meet the users? various requirements which might be to control the beam size and intensity at the beam target, and the timing of the proton beam. The magnet to distribute the proton beam to many beamlines is an AC magnet which has an AC frequency of 15 Hz, and is powered with a programmable AC power supply. In this paper, the result of the optics design will be presented and the magnet design will be described.  
 
TUPLT093 Tune Survey of Dynamic Apertures for High-brilliance Optics of the Pohang Light Source septum, proton, gun, booster 1375
 
  • E.-S. Kim
    PAL, Pohang
  The PLS storage ring is a 2.5 GeV light source and the dynamic apertures in a lattice for the low emittance in the ring have been investigated by a simulation method. The dynamic apertures that include effects of machine errors and insertion devices were obtained by a tune survey in the simulation. It was also shown that how large are the dynamic aperture compensated after corrections of a CODs. The betatron tune for the operation of the high-brilliance lattice are investigated based on the view point of dynamic apertures obtained from a tune survey.  
 
TUPLT095 Precision Field Mapping System for Cyclotron Magnet septum, proton, gun, booster 1378
 
  • K.-H. Park, Y.G. Jung, D.E. Kim, L.W.W. Lee
    PAL, Pohang
  • J.-S. Chai, Y.S. Kim
    KIRAMS, Seoul
  • B.-K. Kang, S.H. Shin, M. Yoon
    POSTECH, Pohang
  A 13 MeV cyclotron has been developed by KIRAMS for radio-isotopes production such as F-18 and O-15 for positron emission tomography(PET). To characterize the cyclotron magnet precisely, a Hall probe mapping system with very high precise positioning mechanism in the Cartesian coordinate has been developed. Hall probe assembly was translated in two dimensions by two stepping motors at both sides of the Hall-probe-carrier to keep synchronously rotation sharing one step-pulse source for x-axis and one motor for y-axis. The data acquisition time had reduced to 60 minutes in full mapping by 'flying' mode. The accuracy of the measurement system is better than during the entire mapping process. In this paper the magnetic field measurement system for the cyclotron magnet is described, and measurement results are presented.  
 
TUPLT096 RFQ Low Level RF System for the PEFP 100MeV Proton Linac septum, gun, booster, optics 1381
 
  • I.H. Yu, M.-H. Chun, K.M. Ha, Y.J. Han, W.H. Hwang, M.H. Jeong, H.-S. Kang, D.T. Kim, S.-C. Kim, I.-S. Park, J.S. Yang
    PAL, Pohang
  • Y.-S. Cho, K.T. Seol
    KAERI, Daejon
  The 100MeV Proton linear accelerator (Linac) for the PEFP (Proton Engineering Frontier Project) will include a 3MeV, 350MHz RFQ(Radio-Frequency Quadrupole) Linac. The RFQ accelerates a 20mA proton beam from 50keV to 3MeV. The low level RF system for RFQ provides field control. In addition to field control, it provides cavity resonance control. An accelerator electric field stability of ± 1% in amplitude and ± 1° in phase is required for the RF system. The low level RF system has been designed and is now being fabricated.  
 
TUPLT098 Vertical Beam Motion in the AGOR Cyclotron septum, gun, booster, optics 1384
 
  • M.A. Hofstee, S. Brandenburg, H. Post, W.K. van Asselt
    KVI, Groningen
  Large-scale vertical excursions have been observed in the AGOR cyclotron for light ionbeams at energies close to the focussing limit (E/A =200 Q/A MeV per nucleon). With increasing radius the beam gradually moves down out of the geometrical median plane by several mm, leading to internal beamlosses. It was concluded that this effect is caused by a vertical alignment error of the coils combined with the weak vertical focussing for the beams concerned. Moving the main coils by a total of 0.37 mm has significantly improved the situation at large radii, but results in internal beamlosses for certain beams at small radii due to a large upward excursion. A systematic study of the vertical beam dynamics as a function of beam particle and energy will be presented. Possible causes and solutions will be discussed.  
 
TUPLT099 A Kicker Pulse Power Supply with Low Jitter septum, kicker, gun, booster 1387
 
  • C.-S. Fann, J.-P. Chiou, S.Y. Hsu, K.-B. Liu
    NSRRC, Hsinchu
  The performance of kicker pulse power supplies is the main parameter to increase injection efficiency of storage ring that is an important issue for laboratory of synchrotron radiation research. The output current waveform of a kicker pulse power supply with low timing jitter is our goal for years that must satisfy the Top-Up mode injection requirement of NSRRC. In the past years kicker pulse power supplies of storage ring of NSRRC are immersed in isolation oil to sustain high voltage operational environment that led difficult to maintain, electronic component degrading and uneasy to tune parameters. Air-cooling and air-isolation is adopted in the new design structure for kicker pulse power supply system and an pre-trigger unit MA2709A is installed to trigger thyratron tube CX1536A, a kicker pulse power supply with low timing jitter 1~2ns(p-p) is obtained and could satisfy for Top-Up mode injection and maintenance is more easier than before.  
 
WEPLT107 Nonlinear field Effects in the JPARC Main Ring radiation, antiproton, plasma, proton 2098
 
  • A.Y. Molodojentsev, S. Machida, Y. Mori
    KEK, Ibaraki
  Main Ring (MR) of the Japanese Particle Accelerator Research Complex (JPARC) should provide acceleration of the high-intensity proton beam from the energy of 3GeV to 50 GeV. The expected beam intensity is 3.3·1014 ppp and the repetition rate is about 0.3 Hz. The imaginary transition lattice of the ring was adopted, which has the natural linear chromaticity about (-30) for both transverse phase planes. The expected momentum spread of the captured particles before the acceleration is less than 0.007. Two independent families of the chromatic sextupole magnets are use to eliminate the linear chromatic tune shift. This chromatic sextupole field nonlinearity will excite the normal 'octupole' resonances and will lead to the amplitude dependent tune shifts in both transverse phase planes. Additional sextupole magnets are planed to excite the third-order horizontal resonance, which will be used for the slow extraction. Incoherent tune shift of the low-energy proton beam is about (-0.16) so that some particles could cross nearest low-order resonances. Optimization of the 'bare' working point of MR at the injection energy has been performed to minimize the influence of the linear coupling and high-order coupling resonances. Excitation of the linear coupling resonance has been introduced by the realistic misalignment errors adopted for MR. The 'bare' working point during the slow extraction has been analyzed. The influence of the normal sextupole resonances on the large amplitude particle behavior at the scraper location has been studied including random sextupole field component of the MR bending magnets. Realistic distortion of the ideal ring super-periodicity by the injection kicker magnets has been included in the tracking procedure for the on- and off-momentum particles. Finally, correction schemes have been considered for most dangerous resonances around the optimized 'bare' working point. The space-charge effects of the proton beam have not been included in this study.  
 
WEPLT108 Diffusion caused by Beam-beam Interactions with Couplings radiation, antiproton, plasma, proton 2101
 
  • K. Ohmi, S. Kamada, K. Oide, M. Tawada
    KEK, Ibaraki
  A system of colliding two beams is strong nonlinear in multi-dimension. In such a system, a symplectic diffusion called Arnold diffusion occurs, with the result that the beams are enlarged and the luminosity is degraded in circular colliders. We discuss the diffusion seen in beam-beam inetraction at a circular accelerator, especially finite crossing angle and/or x-y coupling errors enhance the diffusion.  
 
WEPLT109 Simulation of Ep Instability for a Coasting Proton Beam in Circular Accelerators radiation, antiproton, plasma, booster 2104
 
  • K. Ohmi, T. Toyama
    KEK, Ibaraki
  • G. Rumolo
    GSI, Darmstadt
  ep instability is discussed for a coasting beam operation of J-PARC 50 GeV Main Ring. Our previous study (PAC2003) was focussed only ionization electron. We now take into account electrons created at the chamber wall due to proton loss and secondary emission with higher yield than ionization.  
 
WEPLT110 Specific Beam Dynamics in Super-bunch Acceleration radiation, antiproton, plasma, booster 2107
 
  • Y. Shimosaki, E. Nakamura, K. Takayama, T. Toyama
    KEK, Ibaraki
  • K. Horioka, M. Nakajima
    TIT, Yokohama
  • K. Koseki
    GUAS/AS, Ibaraki
  • K. Torikai
    Kyushu University, Fukuoka
  • M. Watanabe
    RIKEN, Saitama
  Proof-of-principle experiments on the induction synchrotron concept using the KEK 12-GeV PS makes progress, in which RF bunches and a super-bunch will be accelerated with a long step voltage generated in the induction accelerating gaps. In order to give a guide for super-bunch acceleration, the beam stabilities against a droop and a fluctuation of the accelerating voltage have been examined by using a simulation. The droop voltage gives an additional focusing or defocusing force in the longitudinal direction, which leads the mismatching beyond the transition energy. Furthermore, the extremely slow fluctuation of the accelerating voltage causes a lowest-order resonance near the transition. These induce a serious emittance blow-up in the longitudinal, so that the compensating manners will be presented. Moreover, the other issues such as head-tail instability and intra beam scattering will be discussed.  
 
WEPLT113 Development of New Hydrostatic Levelling Equipment for Large Next Generation Accelerator radiation, antiproton, plasma, booster 2110
 
  • S. Takeda
    KEK, Ibaraki
  The Hydrostatic Levelling Systems (HLS) are installed and commissioned in many laboratories. We have developed a new type hydrostatic levelling equipment for the large future accelerator. The designing points are as followings: (1) use of half filled water level sensor instead of the usual full filled level sensor, (2) the capacitive sensor is supported by an invar rod and (3) use of digitized signal transfer system. These three points are very important factor to apply the leveling system to large next generation accelerator in order to obtain good temperature stability and being free from the environmental electronic noises. We have obtained a typical resolution of the equipment as 0.3 micron-meter, though usual HLS shows the value ten times as much. We are going to show a detailed report about the system including data obtained.  
 
WEPLT114 Field Measurements in the AGS Warm Snake radiation, antiproton, plasma, booster 2113
 
  • J. Takano, M. Okamura
    RIKEN, Saitama
  • R. Alforque, R. Belkin, G. Ganetis, A.K. Jain, W.W. MacKay, T. Roser, R. Thomas, J. Tuozzolo
    BNL, Upton, Long Island, New York
  • T. Hattori
    RLNR, Tokyo
  A new warm snake has been produced for avoiding the transverse coupling resonance in the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory (BNL). The warm snake is the world?s first normal conducting helical dipole partial snake which has a double pitch structure to allow spin rotation with no net beam offset or deflection with a single magnet. The warm snake is 2.6m long, and has a field of 1.5 Tesla for a 9 degrees spin rotation. The pitches, current density, and shims were optimized by using OPERA_3D / TOSCA. The magnetic field harmonics have been measured using a system of 51 mm long, 34 mm radius tangential coils. The axial variation of the dipole field angle agrees very well with the calculations, indicating no significant construction errors. However, the measured transfer function shows a discrepancy of 4% which may be caused by BH-curve differences, deformation of the iron and packing factor of the laminations. To correct the beam trajectory the operating current was adjusted and shims were installed on the end plates. These optimization studies, and comparison with measurements, will be shown.  
 
WEPLT115 A Study of Transverse Resonance Crossing in FFAG radiation, antiproton, plasma, resonance 2116
 
  • M. Aiba
    University of Tokyo, Tokyo
  • S. Machida, Y. Mori
    KEK, Ibaraki
  A study of "resonance crossing" in FFAG accelerator is described in this paper. A deviation of FFAG guiding field in actual magnet breaks zero chromaticity condition, and tunes cross resonance while acceleration. In order to avoid a critical beam loss or emittance growth, nominal tune should be chosen so as not to cross low-order resonances. However, crossing higher order resonance can be critical and that depends on the parameters such as crossing speed, excitation magnitude and initial beam emittance. We will present analytical model and simulation study in various parameter space.  
 
WEPLT116 Lattice Design and Cooling Simulation at S-LSR radiation, antiproton, plasma, resonance 2119
 
  • T. Shirai, H. Fadil, S. Fujimoto, M. Ikegami, A. Noda, M. Tanabe, H. Tongu
    Kyoto ICR, Uji, Kyoto
  • T. Fujimoto, H. Fujiwara, K. Noda, S. Shibuya, T. Takeuchi
    NIRS, Chiba-shi
  • M. Grieser
    MPI-K, Heidelberg
  • H. Okamoto, Y. Yuri
    HU/AdSM, Higashi-Hiroshima
  • E. Syresin
    JINR, Dubna, Moscow Region
  A compact ion cooler ring, S-LSR is under construction in Kyoto University. The circumference is 22.557 m and the maximum magnetic rigidity is 1 Tm. One of the important roles of S-LSR is a test bed to examine the lowest temperature limit of the ion beams using cooling techniques. The ultimate case is a crystalline one. The ring optics of S-LSR has a high super periodicity and a low phase advance to reduce the beam heating from the lattice structure. S-LSR has an electron beam cooling device and a laser cooling system for Mg. The simulation results show the possible limit of the ion beam temperature and the dependence on the operating betatron tunes.  
 
WEPLT117 Design of a Third Harmonic Superconducting RF System at PLS radiation, antiproton, plasma, resonance 2122
 
  • E.-S. Kim, M.-H. Chun, H.-G. Kim, K.-R. Kim, I.-S. Park, Y.-U. Sohn, J.S. Yang
    PAL, Pohang
  • J.-K. Ahn, J.-S. Cho
    Pusan National University, Pusan
  A superconducting third harmonic rf system has been designed in the PLS to raise beam lifetime. Expected beam lifetimes verse beam emittance and operational beam current are presented. A multibunch multiparticle tracking simulation is performed to investigate energy spread, bunch-lengthening and beam instabilities due to the rf cavities. The parameters of the designed rf cavity, designed cryogenic system and estimation of heat load are also presented.  
 
WEPLT118 Performance of the TU/e 2.6 Cell Rf-photogun in the 'Pancake' Regime radiation, antiproton, resonance, ion 2125
 
  • S.B. van der Geer, G.J.H. Brussaard, O.J. Luiten, M.J. Van der Wiel
    TUE, Eindhoven
  • G. Pöplau
    Rostock University, Faculty of Engineering, Rostock
  • M.J. de Loos
    PP, Soest
  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.  
 
WEPLT119 Beam Instabilitiy Studies of BEPC and BEPCII radiation, antiproton, resonance, ion 2128
 
  • J.Q. Wang, Z.Y. Guo, Y.D. Liu, Q. Qin, Z. Zhao, D.M. Zhou
    IHEP Beijing, Beijing
  BEPC has been well operated for more then 10 years, and it will be upgraded to a double ring electron positron collider using the existing tunnel, namely BEPCII. This paper describes the recent studies on beam instabilities in BEPC for the improvement of its performance as well as for BEPCII. The instabilities caused by impedance and two-stream effect are investigated. The experimental and simulation results are reported.  
 
WEPLT120 Control Environment for the Superconducting Insertion Devices at NSRRC radiation, insertion, antiproton, resonance 2131
 
  • J. Chen, C.-K. Chang, K.-T. Hsu, K.H. Hu, C.H. Kuo, C.-J. Wang
    NSRRC, Hsinchu
  To enhance hard X-ray capability in the 1.5 GeV storage ring of NSRRC to serve the rapidly growing X-ray user community in Taiwan, the storage ring was installed two superconducting insertion devices. Three more superconducting insertion devices are in planning. A 6 Tesla superconducting wavelength shifter was installed in mid-2002. A 3.2 Tesla superconducting multi-pole wiggler was installed in December of 2003. Control system and operation environment have been set up to support the operation of the superconducting insertion devices. The implementation and operation experiences will be summarized in this report.  
 
WEPLT121 Computer Simulation of Equilibrium Electron Beam Distribution in the Proximity of 4th Order Single Nonlinear Resonance radiation, insertion, antiproton, resonance 2134
 
  • T.-S. Ueng, C.-C. Kuo, H.-J. Tsai
    NSRRC, Hsinchu
  • A. Chao
    SLAC, Menlo Park, California
  The beam distribution of particles in an electron storage ring is distorted in the presence of nonlinear resonances. A computer simulation is used to study the equilibrium distribution of an electron beam in the presence of 4th order single nonlinear resonance. The results are compared with that obtained using an analytical approach by solving the Fokker-Planck equation to first order in the resonance strength. The effect of resonance on the quantum lifetime of electron beam is also compared and investigated.  
 
WEPLT122 Investigation of Microwave Instability on Electron Storage Ring TLS radiation, antiproton, resonance, ion 2137
 
  • M.-H. Wang
    NSRRC, Hsinchu
  • A. Chao
    SLAC, Menlo Park, California
  With the planned installation of a superconducting rf system, the new operation mode of TLS, the electron storage ring at NSRRC, is expected to double the beam intensity. Several accelerator physics topics need to be examined. One of these topics concerns the beam instability of single-bunch longitudinal microwave instability. We consider different approaches to measure the effective broad band impedance. We compare these measurement results with each other and to the old data [*]. The new measurements of effective broad band impedance are higher than the old measurement since between these two sets of measurements several narrow gap insertion devices were installed into the storage ring. We calculate the threshold current of microwave instability with a mode-mixing analysis code written by Dr. K. Oide of KEK [**]. We also develop a multi-particle tracking code to simulate the instability. The results of simulation and measurement are compared and discussed. We conclude that the doubling of beam current will not onset the microwave instability even without a Landau cavity to lengthen the bunch.

* M.H. Wang, et al.,"Longitudinal Beam Instability Observation with streak Camera at SRRC", proceeding of 1996 European Particle Accelerator Conference, pp. 1120** K. Oide, "Longitudinal Single-Bunch Instability in Electron Storage Rings", KEK Preprint 90-10

 
 
WEPLT123 Engineering Design of High-current 81.36 MHz RFQ with Elliptic Coupling Windows radiation, antiproton, resonance, target 2140
 
  • D. Kashinskiy, A. Kolomiets, S. Minaev, V. Pershin, B.Y. Sharkov, T. Tretyakova
    ITEP, Moscow
  Four-vane RFQ structure with elliptic coupling windows has been originally developed at ITEP for injection into ITEP-TWAC synchrotron/storage ring complex, being lately adapted for RIA project too. As the electrodynamics simulations show, this structure combines the high efficiency with the operating mode stability against asymmetric detuning and electrode misalignment. A considerable reduction of structure diameter due to coupling windows becomes important for low frequency range which is necessary for the heavy ion acceleration. At the same time, the electrode configuration allows the efficient cooling and high duty factor operation. A mechanical design of 81 MHz, 1.6 MeV/u, 6 m long heavy ion RFQ section is discussed. The outer tank is made of two layers, steel and copper, joined by using the thermal diffusion technology. Each electrode is supplied with the alignment mechanism and connected to the tank by the flexible conducting insert. The whole setup is in manufacturing now.  
 
WEPLT126 Beam Dynamics Simulation in High Energy Electron Cooler radiation, antiproton, resonance, electron 2143
 
  • A.V. Ivanov, V.M. Panasyuk, V.V. Parkhomchuk, V.B. Reva
    BINP SB RAS, Novosibirsk
  The article deals with electron beam dynamics in projected high energy electron cooler. Classical electrostatic scheme with several MeV electron energy is considered. The increase of transversal energy of electrons in an accelerating section, in bends and at the matching point of magnetic fields is calculated. In order to calculate beam behavior in bends with electrostatic compensation of centripetal drift new ELEC3D electro- and magnitostatic 3D code is developed. BEAM code is used for simulation of dynamics in an accelerating section. The methods of keeping low transversal energy are estimated.  
 
WEPLT128 Charge Particle Source for Industrial and Research Accelerators Operating at the Poor Vacuum Conditions radiation, antiproton, resonance, electron 2146
 
  • E.O. Popov, A.A. Pashkevich, S.O. Popov, A.V. Vitugov
    IOFFE, St. Petersburg
  We investigated the original method of fabrication of the great number of emitting tips by pulling liquid metal through the holes in track membrane under influence of electric field. The track membranes are produced by cyclotron of Physicotechnical Institute. This method enables to fabricate up to 1·108 emitting tips per square cm. Special test facility to investigate emitter parameters operating at different values of background residual gas pressure was designed and developed. The liquid metal multiple tip field emitters possess some unique characteristics which are attractive in accelerators for material irradiation: unlimited life expectancy, large current densities (about 100 mA per sq. cm), practically unlimited surface, stable emission in poor vacuum.  
 
WEPLT133 On Beam Dynamics Optimization radiation, antiproton, resonance, electron 2149
 
  • D.A. Ovsyannikov, S.V. Merkuryev
    St. Petersburg State University, St. Petersburg
  Mathematical optimization methods are widely used in designing and construction of charged particle accelerators. In this paper new approach to beam dynamics optimization is considered. Suggested approach to the problem is based on the analytical representation for variation of examined functionals via solutions of special partial differentional equations. The problem of optimization is considered as a problem of mutual optimization chosen synchronous particle motion and charged particles beam at whole. This approach was applied to the beam dynamics optimization for RFQ structures.  
 
WEPLT136 Lattice Studies For The MAX-IV Storage Rings antiproton, resonance, target, beamloading 2152
 
  • H. Tarawneh, M. Eriksson, L.-J. Lindgren, S. Werin
    MAX-lab, Lund
  • B. Anderberg
    AMACC, Uppsala
  • E.J. Wallén
    ESRF, Grenoble
  The lattice for the future MAX-IV storage rings at MAX-Lab has been studied, The MAX IV facility consists of two similar rings operated at 1.5 GeV and 3 GeV electron energies, The ring consists of 12 supercells each built up by 5 unit cells and matching sections. The high periodicity of the lattice combined with the high gradients in the small gap dipole magnets yield a small emittance of 1 nm.rad, good dynamic aperture and momentum acceptance. In the matching section, a soft end dipole magnet is introduced to reduce the synchrotron radiation power hitting the upstream straight section.  
 
WEPLT137 Higher Order Modes in the New 100 and 500 MHz Cavities at MAX-lab antiproton, resonance, target, beamloading 2155
 
  • H. Tarawneh, Å. Andersson, M. Bergqvist, M. Brandin, M. Eriksson, L. Malmgren
    MAX-lab, Lund
  The MAX-II electron storage ring operates exclusively in multi-bunch mode with all buckets filled. Damping of the longitudinal higher order mode (HOM) instabilities has successfully been provided by passive third harmonic 1.5 GHz cavities. With a new RF employing three 100 MHz capacity loaded cavities and a fifth harmonic Landau cavity installed, a study of the HOM impedances, and related threshold instability currents, is necessary. Measurements and calculations so far, are being presented.  
 
WEPLT138 Laser Cooling of Electron Bunches in Compton Storage Rings antiproton, laser, resonance, emittance 2158
 
  • E.V. Bulyak
    NSC/KIPT, Kharkov
  Self-consistent dynamics of a bunch circulating in the Compton storage ring has been studied analytically. Disturbances from both the synchrotron and Compton radiations were taken into account. The emittances in laser-dominated rings (where the synchrotron energy losses are much smaller then the Compton ones) were evaluated. The resultant emittances (synchrotrons plus Comptons) were compared with the synchrotrons. As were shown, the longitudinal degree of freedom is heated up due to Compton scattering. Almost the same conclusion is valid for the vertical uncoupled betatron emittance. Since it is impossible in principle to get zero dispersion in the banding magnets, the radial emittance almost always cooling down by laser. Therefore in practical cases of coupled transverse oscillations with the horizontal emittance determining the vertical one, the laser will cool down the transverse degrees of freedom.  
 
WEPLT140 New Abilities of Computer Code DeCA antiproton, laser, resonance, emittance 2161
 
  • P. Gladkikh, A.Y. Zelinsky
    NSC/KIPT, Kharkov
  In the paper the status and new abilities of computer code package DeCA (Design of Cyclic Acclerators) are described. The main effort of the code developers were made to creation of software capable to simulate intrabeam scattering effect and Compton scattering. In addition modules for calculation of the second order dispersion and momentum compaction factor were developed.  
 
WEPLT141 Beam-power Calibration System for Industrial Electron Accelerators antiproton, laser, resonance, emittance 2164
 
  • V.L. Uvarov, S.P. Karasyov, V.I. Nikiforov, R.I. Pomatsalyuk, V.A. Shevchenko, I.N. Shlyakhov, A.Eh. Tenishev
    NSC/KIPT, Kharkov
  Modern electron accelerators for industrial application provide particle energy of up to 10 MeV and beam power of up to 100 kW. Such a beam is ejected into an air using a scanning system. The measuring channel based on a total-absorption calorimeter of flow-type for a beam calibration with respect to energy flow is designed. The processes of beam interaction with the primary measuring converter (a water-cooled beam absorber of especial geometry) were previously studied using a computer simulation. The metering circuit of the channel is made as a stand-alone module with LCD display and control keypad. It performs the operations of temperature measurement at the input and output of the absorber, as well as a water flow-rate determination. The absorbed power is calculated from measured parameters and then is displayed and stored into channel memory using appropriate software. The process is carried out both in off-line mode and under control of the external PC via a serial interface of RS-232 type.  
 
WEPLT143 Simulation Calculations of Stochastic Cooling for Existing and Planned GSI Facilities laser, resonance, emittance, target 2167
 
  • I. Nesmiyan
    National Taras Shevchenko University of Kyiv, Radiophysical Faculty, Kiev
  • F. Nolden
    GSI, Darmstadt
  The process of longitudinal stochastic cooling is simulated using a Fokker-Planck model. The model includes the sensitivities of pick-up and kicker electrodes as calculated from field theoretical models. The effect of feedback through the beam is taken into account. Intra beam scattering is treated as an additional diffusive effect. The calculations cover the existing system of the ESR storage ring at GSI as well as the cooling system for secondary heavy ion and antiproton beams at the proposed new accelerator facility. The paper discusses the resulting cooling times. Requirements on the system layout as amplification factors and electrical power can be derived from the simulations.  
 
WEPLT144 New Characteristics of a Single-bunch Instability Observed in the APS Storage Ring laser, resonance, emittance, target 2170
 
  • C.-X. Wang
    ANL, Argonne, Illinois
  • K. Harkay
    ANL/APS, Argonne, Illinois
  In the Advanced Photon Source storage ring, a transverse single-bunch instability has long been observed that appears unique to this ring. Many of its features have been previously reported. New results have recently been obtained using beam centroid history measurements and analysis. These preliminary results provide more detailed information regarding the characteristics of this instability and could provide insight into the physics mechanism.  
 
WEPLT145 Beam Loss Studies in High-intensity Heavy-ion Linacs linac, laser, resonance, target 2173
 
  • P.N. Ostroumov, V.N. Aseev, E.S. Lessner, B. Mustapha
    ANL/Phys, Argonne, Illinois
  A low beam-loss budget is an essential requirement for high-intensity machines and represents one of their major design challenges. In a high-intensity heavy-ion machine, losses are required to be below 1 W/m for hands-on-maintenance. The driver linac of the Rare Isotope Accelerator (RIA) is designed to accelerate beams of any ion to energies from 400 MeV per nucleon for uranium up to 950 MeV for protons with a beam power of up to 400 kW. The high intensity of the heaviest ions is achieved by acceleration of multiple-charge-state beams, which requires a careful beam dynamics optimization to minimize effective emittance growth and beam halo formation. For beam loss simulation purposes, large number of particles must be tracked through the linac. Therefore the computer code TRACK [P.N. Ostroumov and K.W. Shepard, PRST AB 11, 030101 (2001)] has been parallelized and calculations is being performed on the JAZZ cluster [*] recently inaugurated at ANL. This paper discusses how this powerful tool is being used for simulations for the RIA project to help decide on the high-performance and cost-effective design of the driver linac.

* The Jazz Cluster, http://www.lcrc.anl.gov/jazz

 
 
WEPLT146 Mismatch Oscillations in High-current Accelerators linac, laser, resonance, target 2176
 
  • O.A. Anderson
    LBNL, Berkeley, California
  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.

* 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)

 
 
WEPLT147 Lattice Studies for CIRCE (Coherent InfraRed CEnter) at the ALS linac, laser, resonance, target 2179
 
  • H. Nishimura, D. Robin, F. Sannibale, W. Wan
    LBNL, Berkeley, California
  CIRCE (Coherent InfraRed Center) at the Advanced Light Source is a proposal for a new electron storage ring optimized for the generation of coherent synchrotron radiation (CSR) in the terahertz frequency range. One of the main requirement for this special mode of operation is the capability of the ring of operating at very small momentum compaction values. In this regime, the longitudinal dynamics becomes strongly nonlinear and an accurate control of the higher order energy dependent terms of the momentum compaction is necessary. The lattice for CIRCE allows controlling these terms up to the third order. The paper describes the lattice and presents the calculated performances in terms of momentum acceptance, dynamic aperture, lifetime and momentum compaction tune capabilities.  
 
WEPLT148 Dynamical Map for Combined Function Magnets with Solenoid, Dipole and Quadrupole Fields linac, laser, resonance, target 2182
 
  • A. Wolski, M. Venturini
    LBNL, Berkeley, California
  The interaction regions of colliders invariably include strong solenoid fields. Where quadrupoles and dipoles are embedded in the solenoid, the beam dynamics in the combined fields can be complicated to model using the traditional approach of interleaving slices of different fields. The complexity increases if the design trajectory is offset from the magnetic axis; this is the case, for example, in PEP-II. In this paper, we present maps for combined solenoid, dipole and quadrupole fields that provide a much simpler alternative to the traditional approach, and show that the deviation of the design trajectory from the magnetic axis can be handled in a straightforward manner. We illustrate the techniques presented by reference to the PEP-II interaction region.  
 
WEPLT149 Image-charge Effects on the Beam Halo Formation and Beam Loss in a Small-aperture Alternating-gradient Focusing System linac, laser, resonance, focusing 2185
 
  • J. Zhou, C. Chen
    MIT/PSFC, Cambridge, Massachusetts
  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.  
 
WEPLT151 Using the PBO LAB(TM) Optimization and Transport Modules to Gain an Improved Understanding of the LLUMC Proton Therapy Beamlines optics, linac, proton, laser 2188
 
  • G.H. Gillespie, O.V. Voronkova
    G.H. Gillespie Associates, Inc., Del Mar, California
  • G. Coutrakon, J. Hubbard, E. Sanders
    LLU/MC, Loma Linda, California
  The Particle Beam Optics Laboratory (PBO Lab) has an advanced Optimization Module that works in concert with beam optics codes (also modules in PBO Lab) to solve optimization and fitting problems that are difficult or impossible to address with optics code alone. The PBO Lab Optimization Module has been used in conjunction with the TRANSPORT Module to study the beamlines of the proton therapy center at the Loma Linda University Medical Center (LLUMC). The primary goal of the study was to establish a fast, efficient and reliable procedure for determining the parameters of the beam extracted from the synchrotron accelerator that best fit the extensive wire scanner profile data used to monitor the LLUMC proton therapy beamlines. This paper summarizes how the PBO Lab Optimization Module is applied to this problem and presents selected results from the LLUMC proton therapy beamline study.  
 
WEPLT152 Experimental Results of the Small Isochronous Ring optics, linac, proton, laser 2191
 
  • J.A. Rodriguez, F. Marti, R.C. York
    NSCL, East Lansing, Michigan
  • E. Pozdeyev
    Jefferson Lab, Newport News, Virginia
  The Small Isochronous Ring (SIR) has been in operation since December 2003. The main purpose of this ring, developed and built at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU), is to simulate the dynamics of intense beams in large accelerators. To observe the same effects, the beam power needed in SIR is orders of magnitude lower and the time scale is much longer than in the full scale machines. These differences simplify the design and operation of the accelerator. The ring measurements can be used to validate the results of space charge codes. After a variable number of turns, the injected hydrogen bunch (with energies up to 30 keV) is extracted and its longitudinal profile is measured using a fast Faraday cup. We present a summary of the design, the results of the first six months of operation and the comparison with selected space charge codes.  
 
WEPLT153 Multi-pass Beam-breakup: Theory and Calculation optics, proton, laser, resonance 2194
 
  • I. Bazarov
    Cornell University, Department of Physics, Ithaca, New York
  • G. Hoffstaetter
    Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
  Multi-pass, multi-bunch beam-breakup (BBU) has been long known to be a potential limiting factor for the current in linac-based recirculating accelerators. New understanding of theoretical and computational aspects of the phenomenon are presented here. We also describe a detailed simulation study of BBU in the proposed 5 GeV Energy Recovery Linac light source at Cornell University which is presented in a separate contribution to this conference.  
 
WEPLT154 UAL Implementation of String Space Charge Formalism optics, proton, laser, resonance 2197
 
  • R.M. Talman
    Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
  • N. Malitsky
    BNL, Upton, Long Island, New York
  By reformulating the force between point charges as the force on a point charge due to a co-moving line charge (or "string",) space charge calculations can be reformulated as intrabeam scattering, with no intermediate, particle-in-cell step required.[*] This approach is expected to be especially useful for calculating emittance dilution of ultrashort bunches in magnetic fields, where coherent radiative effects are important. This paper describes the partial implementation of this approach within UAL (Unified Accelerator Libraries.) The interparticle force is calculated and applied to the dynamics of a bunch represented by just two superparticles in an idealized lattice, with emphasis on the head-tail effect. Gridding of the interparticle force, as needed for realistic multiparticle simulation, is also described.

* R. Talman, "String Formulation of Space Charge Forces in a Deflected Bunch". Submitted to PRSTAB, January, 2004

 
 
WEPLT155 Effect of Dark Currents on the Accelerated Beam in an X-band Linac optics, proton, laser, resonance 2200
 
  • V.A. Dolgashev
    SLAC/ARDA, Menlo Park, California
  • K.L.F. Bane, G.V. Stupakov, J. Wu
    SLAC, Menlo Park, California
  • T.O. Raubenheimer
    SLAC/NLC, Menlo Park, California
  X-band accelerating structures operate at surface gradients up to 120-180 MV/m. At these gradients, electron currents are emitted spontaneously from the structure walls ("dark currents") and generate additional electromagnetic fields inside the structure. We estimate the effect of these fields on the accelerated beam in a linac using two methods: a particle-in-cell simulation code MAGIC and a particle tracking code. We use the Fowler-Nordheim dependence of the emitted current on surface electric field with field enhancement factor beta. In simulations we consider geometries of traveling wave structures that have actually been built for the Next Linear Collider project.  
 
WEPLT156 Suppression of Microbunching Instability in the Linac Coherent Light Source electron, optics, proton, resonance 2203
 
  • Z. Huang, P. Emma, C. Limborg-Deprey, G.V. Stupakov, J.J. Welch, J. Wu
    SLAC, Menlo Park, California
  • M. Borland
    ANL/APS, Argonne, Illinois
  A microbunching instability driven by longitudinal space charge, coherent synchrotron radiation and linac wakefields is studied for the linac coherent light source (LCLS) accelerator system. Since the uncorrelated (local) energy spread of electron beams generated from a photocathode rf gun is very small, the microbunching gain may be large enough to significantly amplify shot noise fluctuations of the electron beam. The uncorrelated energy spread can be increased by an order of magnitude without degrading the free-electron laser performance to provide strong Landau damping against the instability. We study different damping options in the LCLS and discuss an effective laser heater to minimize the impacts of the instability on the quality of the electron beam.  
 
WEPLT157 Single-bunch Electron Cloud Effects in the GLC/NLC, US-cold and TESLA Low Emittance Transport Lines electron, optics, proton, resonance 2206
 
  • M.T.F. Pivi, D. Bates, A. Chang, D. Chen, T.O. Raubenheimer
    SLAC, Menlo Park, California
  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.  
 
WEPLT158 Direct Measurement of the Resistive Wakefield in Tapered Collimators electron, optics, proton, wakefield 2209
 
  • P. Tenenbaum
    SLAC, Menlo Park, California
  • D. Onoprienko
    Brunel University, Middlesex
  The transverse wakefield component arising from surface resistivity is expected to play a major role in the beam dynamics of future linear colliders. We report on a series of experiments in which the resistive wakefield was measured in a series of tapered collimators, using the Collimator Wakefield beam test facility at SLAC. In order to separate the contributions of geometric and resistive wakefields, two sets of collimators with identical geometries but different resistivities were measured. The results are in agreement with the theoretical prediction for the high-resistivity (titanium) collimators, but in the case of low-resistivity (copper) collimators the resistive deflections appear to be substantially larger than predicted.  
 
WEPLT159 Linear Vlasov Analysis for Stability of a Bunched Beam electron, optics, proton, wakefield 2212
 
  • R.L. Warnock, G.V. Stupakov
    SLAC, Menlo Park, California
  • J.A. Ellison
    UNM, Albuquerque, New Mexico
  • M. Venturini
    LBNL, Berkeley, California
  We study the linearized Vlasov equation for a bunched beam subject to an arbitrary wake function. Following Oide and Yokoya, the equation is reduced to an integral equation expressed in angle-action coordinates of the distorted potential well. Numerical solution of the equation as a formal eigenvalue problem leads to difficulties, because of singular eigenmodes from the incoherent spectrum. We rephrase the equation so that it becomes non-singular in the sense of operator theory, and has only regular solutions for coherent modes. We report on a code that finds thresholds of instability by detecting zeros of the determinant of the system as they enter the upper-half frequency plane, upon increase of current. Results are compared with a time-domain integration of the nonlinear Vlasov equation, and with experiment, for a realistic wake function for the SLC damping rings.  
 
WEPLT167 A Cure for Multipass Beam Breakup in Recirculating Linacs electron, optics, proton, wakefield 2215
 
  • B.C. Yunn
    Jefferson Lab, Newport News, Virginia
  We investigate a method to control the multipass dipole beam breakup instability in a recirculating linac including energy recovery. Effectiveness of an external feedback system for such a goal is shown clearly in a simplified model. We also verify the theoretical result with a simulation study.  
 
WEPLT168 ORBIT Benchmark of Space-charge-induced Emittance Growth in the CERN PS electron, optics, proton, wakefield 2218
 
  • S.M. Cousineau, J.A. Holmes
    ORNL/SNS, Oak Ridge, Tennessee
  • E. Métral
    CERN, Geneva
  Particle tracking codes provide an invaluable tool in the design and operation of high intensity machines. An important task in the development of these codes is the validation of the space charge models through benchmark with experimental data. Presented here are benchmarks of the ORBIT particle tracking code with recent measurements of space-charge-induced transverse emittance growth in the CERN PS machine. Benchmarks of two experimental data sets are performed: Integer resonance crossing, and Montague resonance crossing.  
 
WEPLT169 Benchmark and Threshold Analysis of Longitudinal Microwave Instability in the PSR electron, optics, wakefield, collider 2221
 
  • S.M. Cousineau, J.A. Holmes
    ORNL/SNS, Oak Ridge, Tennessee
  • C. Beltran, R.J. Macek
    LANL/LANSCE, Los Alamos, New Mexico
  A set of inductive inserts used to provide passive longitudinal space charge compensation in the Los Alamos Proton Storage Ring cause a strong microwave instability in the beam when the inductors are at room temperature. We use the ORBIT code to perform benchmarks of the microwave instability dynamics, including the mode spectrum and the instability growth time. Additionally, we analyze the experimental instability intensity threshold and compare it with the simulated threshold. For all parameters benchmarked, results of simulations are in good agreement with the experimental data.  
 
WEPLT170 Injection Schemes for Self Consistent Space Charge Distributions electron, optics, wakefield, collider 2224
 
  • V.V. Danilov, S.M. Cousineau, S. Henderson, J.A. Holmes, M. Plum
    ORNL/SNS, Oak Ridge, Tennessee
  This paper is based on recently found sets of self-consistent 2D and 3D time-dependent space charge distributions. A subset of these distributions can be injection-painted into an accumulator ring, such as Spallation Neutron Source Ring, to produce periodic space charge conditions. The periodic condition guarantees zero space-charge-induced halo growth and beam loss during injection. Practical aspects of such schemes are discussed, and simulations of a few specific cases are presented.  
 
WEPLT171 Rotating Electromagnetic Field Trap for High Temperature Plasma and Charge Confinement electron, optics, wakefield, collider 2227
 
  • V.V. Danilov
    ORNL/SNS, Oak Ridge, Tennessee
  This paper demonstrates that there exists a special combination of oscillating electromagnetic fields capable of trapping ultra high charge densities. Trapped particles undergo stable motion when their frequencies of oscillation are much higher than that of the ocillating field. Contrary to conventional electromagnetic traps, the motion in this dynamic trap is stable for arbitrarily high electromagnetic field amplitudes. This, in turn, leads to the possibility of using enormous electric and magnetic fields from RF or laser sources to confine dense ultrahigh temperature plasmas and particle beams.  
 
WEPLT172 Design & Handling of High Activity Collimators &Ring Components on the SNS electron, optics, wakefield, collider 2230
 
  • G.R. Murdoch, D. Crisp, S. Henderson, M. Holding, K. Potter, T. Roseberry
    ORNL/SNS, Oak Ridge, Tennessee
  Design & Handling of High Activity Collimators on the SNS*G Murdoch,S Henderson, K Potter,T Roseberry,Oak Ridge National Laboratory, USA,H Ludewig, N Simos, Brookhaven National Laboratory, USAJ Hirst, Rutherford Appleton Laboratory,UK, The Spallation Neutron Source accelerator systems will provide a 1GeV, 1.44MW proton beam to a liquid mercury target for neutron production. The expected highest doses to components are in the collimator regions. This paper presents the mechanical engineering design of a typical collimator highlighting the design features incorporated to assist with removal once it is activated. These features include shielding and lifting fixtures but more importantly a double contained flexible water system incorporating remote water couplings.Also presented is a mechanism that allows axial removal of vacuum bellows and its associated vacuum clamps.*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.  
 
WEPLT174 Higher Order Hard Edge End Field Effects electron, optics, wakefield, collider 2233
 
  • J.S. Berg
    BNL, Upton, Long Island, New York
  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.  
 
WEPLT177 Analysis of Electron Cloud at RHIC optics, wakefield, electron, collider 2236
 
  • U. Iriso, M. Blaskiewicz, P. Cameron, K.A. Drees, W. Fischer, H.-C. Hseuh, R. Lee, S. Peggs, L. Smart, D. Trbojevic, S.Y. Zhang
    BNL, Upton, Long Island, New York
  • G. Rumolo
    GSI, Darmstadt
  Pressure rises with high intense beams are becoming the main luminosity limitation at RHIC. Observations during the latest runs show beam induced electron multipacting as one of the causes for these pressure rises. Experimental studies are carried out at RHIC using devoted instrumentation to understand the mechanism leading to electron clouds. Possible cures using NEG coated beam pipes and solenoids are experimentally tested. In the following, we report the experimental electron cloud data and analyzed the results using computer simulation codes.  
 
WEPLT181 Measurement of Multipole Strengths from RHIC BPM Data optics, wakefield, electron, collider 2239
 
  • R. Tomas, M. Bai, W. Fischer
    BNL, Upton, Long Island, New York
  • F. Franchi, G. Rumolo
    GSI, Darmstadt
  Recently resonance driving terms were successfully measured in the CERN SPS and the BNL RHIC from the Fourier spectrum of BPM data. Based on these measurements a new analysis has been derived to extract multipole strengths.In this paper we present experimental measurements of sextupolar and skew quadrupolar strengths carried out at RHIC. Also discussed is the possibility of a non-destructive measurement using an AC dipole.  
 
WEPLT182 Non-linear Modeling of the RHIC Interaction Regions optics, wakefield, electron, collider 2242
 
  • R. Tomas, W. Fischer, A.K. Jain, Y. Luo, F.C. Pilat
    BNL, Upton, Long Island, New York
  For RHIC's collision lattices the dominant sources of transverse non-linearities are located in the interaction regions. The field quality is available for most of the magnets in the interaction regions from the magnetic measurements, or from extrapolations of these measurements. We discuss the implementation of these measurements on the MADX models of the Blue and the Yellow rings and their impact on beam stability.  
 
WEPLT183 Clearing of Electron Cloud in SNS optics, wakefield, collider, beamloading 2245
 
  • L. Wang, Y.Y. Lee, D. Raparia, J. Wei, S.Y. Zhang
    BNL, Upton, Long Island, New York
  In this paper we describe a mechanism using the clearing electrodes to remove the electron cloud in the Spallation Neutron Source (SNS) accumulator ring, where strong multipacting could happen at median clearing fields. A similar phenomenon was reported in an experimental study at Los Alamos laboratory's Proton Synchrotron Ring (PSR). We also investigated the effectiveness of the solenoid's clearing mechanism in the SNS, which differs from the short bunch case, such as in B-factories.  
 
WEPLT184 Preliminary Estimation of the Electron Cloud in RHIC optics, wakefield, electron, collider 2248
 
  • L. Wang, P. He, J. Wei
    BNL, Upton, Long Island, New York
  Electron cloud due to beam induce multipacting is suspected to be one of the source of pressure rises in RHIC. This paper estimates the possible electron cloud in RHIC. Various parameters related electron multipacting has been investigated.  
 
THXCH01 Achieving Sub-micron Stability in Light Sources optics, wakefield, collider, beamloading 211
 
  • M. Böge
    PSI, Villigen
  One of the major goals for present and future light sources is to achieve sub-micron orbit stability of the electron beam at the photon beam source points over a large frequency range. This puts tight constraints on the design of the various accelerator components like girders, magnets, power supplies and diagnostic hardware. Fast orbit feedbacks systems based on high performance RF- and X-BPMs become essential to suppress residual orbit distortions. Furthermore the "top-up" operation mode which guaranties a constant electron beam current and thus a constant heat load in 3rd generation light sources is one of the key ingredients to reach sub-micron stability.  
Video of talk
Transparencies
 
THOACH01 SPEAR3 Commissioning wakefield, collider, beamloading, beamlosses 216
 
  • J.A. Safranek, S. Allison, P. Bellomo, W.J. Corbett, M. Cornacchia, E. Guerra, R.O. Hettel, D. Keeley, N. Kurita, D.J. Martin, P.A. McIntosh, H. Morales, G.J. Portmann, F.S. Rafael, H. Rarback, J.J. Sebek, T. Straumann, A. Terebilo, J. Wachter, C. Wermelskirchen, M. Widmeyer, R. Yotam
    SLAC/SSRL, Menlo Park, California
  • M.J. Boland, Y.E. Tan
    ASP, Melbourne
  • J.M. Byrd, D. Robin, T. Scarvie, C. Steier
    LBNL/ALS, Berkeley, California
  • M. Böge
    PSI, Villigen
  • H.-P. Chang, C.-C. Kuo, H.-J. Tsai
    NSRRC, Hsinchu
  • W. Decking
    DESY, Hamburg
  • M.G. Fedurin, P. Jines
    LSU/CAMD, Baton Rouge, Louisiana
  • K. Harkay, V. Sajaev
    ANL/APS, Argonne, Illinois
  • S. Krinsky, B. Podobedov
    BNL/NSLS, Upton, Long Island, New York
  • L.S. Nadolski
    SOLEIL, Gif-sur-Yvette
  • A. Ropert
    ESRF, Grenoble
  • M. Yoon
    POSTECH, Pohang, Kyungbuk
  Starting in April, 2003, the SPEAR2 storage ring was removed and replaced with a new 500 mA, 3 GeV light source, SPEAR3. The SPEAR2 storage ring had been in use for high energy physics, then synchrotron radiation since 1972. Commissioning of SPEAR3 started on December 8, 2003 and synchrotron radiation will be delivered to the first users on March 8, 2004. SPEAR3 commissioning will be reviewed, including discussion of diagnostics, orbit control, optics correction and high current studies.  
Video of talk
Transparencies
 
THOACH02 Commissioning of the 500 MeV Injector for MAX-lab wakefield, collider, beamloading, beamlosses 219
 
  • S. Werin, Å. Andersson, M. Bergqvist, M. Brandin, M. Demirkan, M. Eriksson, L.-J. Lindgren, L. Malmgren, H. Tarawneh, E.J. Wallén
    MAX-lab, Lund
  • B. Anderberg
    AMACC, Uppsala
  • G. Georgsson
    Danfysik A/S, Jyllinge
  • G. LeBlanc
    ASP, Melbourne
  A 500 MeV new injector system for the storage rings MAX I, II and III have been installed during the winter 2003-4 at MAX-lab. The system consists of two linacs at 125 MeV each, using SLED, and a recirculating system such that the electrons pass the linacs twice, thus reaching a final energy of 500 MeV. The system is injected by a thermionic RF-gun. The commissioning of the complete system will be performed in the spring 2004.  
Video of talk
Transparencies