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damping

       
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TUZH102 Ion Instability Issues in Electron Rings electron, ion, vacuum, undulator 79
 
  • T.-Y. Lee, J. Choi, H.-S. Kang
    PAL, Pohang, Kyungbuk
  The fast ion instability (FII) attracts interests recently for the International Linear Collider Project. FII was found by simulation in SLAC and later observed experimentally. Brief introduction and history of FII is given in this talk and a recent observation of FII in the PLS in-vacuum undulator is reported.  
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TUC3MA01 ILC DR Alternative Lattice Design lattice, dynamic-aperture, wiggler, emittance 94
 
  • Y. Sun, Z. Y. Guo
    PKU/IHIP, Beijing
  • J. Gao
    IHEP Beijing, Beijing
  The International Linear Collider (ILC) which is based on super-conducting RF acceleration technology requires the damping rings to provide beams with extremely small equilibrium emittances, and large acceptance to ensure good injection efficiency for high emittance, high energy spread beam from the positron source. In order to reduce the cost for ILC damping rings, an alternative lattice which is different from the baseline configuration design has been designed with modified FODO arc cells，and the total quadrupole number has been reduced by half. At the same time, to decrease the total cost involved in constructing access shafts needed to supply power, cryogenics etc. for the wigglers and other systems, the number of wiggler sections is decreased from 8 to 4, and further to 2. This new lattice has been optimised to have a good dynamic aperture. This alternative ILC damping ring lattice design will reduce the cost largely compared with the baseline design.  
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TUPMA005 Simulation Study on Bunch Lengthening electron, storage-ring, single-bunch, synchrotron 106
 
  • Y. Sun, Z. Y. Guo
    PKU/IHIP, Beijing
  • J. Gao
    IHEP Beijing, Beijing
  The bunch lengthening phenomenon is resulted from one of the most severe single bunch instabilities in electron storage rings. As for BEPCII, controlling the bunch length is the most critical task to fulfil the designed luminosity goal. A new code is developed to calculate the single bunch length and energy spread in storage rings using FORTRAN. In this code, the wake field is calculated using an analytical formula. The bunch length and energy spread under different bunch current are calculated for BEPCII. The tracking results clearly show that the microwave instability threshold is around 65 mA for BEPCII storage ring. The tracking results of this code are in good accordance with those from other codes.  
 
TUPMA099 Adiabatic Damping of the Bunch-length in the Induction Synchrotron acceleration, synchrotron, induction, beam-losses 244
 
  • T. S. Dixit
    GUAS/AS, Ibaraki
  • Y. Shimosaki, K. Takayama
    KEK, Ibaraki
  A fact that a bunch-length shrinks with the barrier-bucket acceleration in the induction synchrotron [1], where a single proton-bunch injected from the 500 MeV Booster was accelerated to 6 GeV in the KEK-PS, has been observed [2]. This has been supposed to be simply explained by a term of adiabatic damping. A technique to analytically deal with such an adiabatic dumping in a case of RF bucket acceleration is well-known; a WKB solution is employed for the small amplitude synchrotron oscillation. However, the simple WKB approach is not available for the present barrier-bucket acceleration, because the longitudinal motion always depends on the oscillation amplitude. A novel technique capable of quantitatively predicting the adiabatic phenomenon in the barrier-bucket acceleration has been newly developed. It turns out that the experimental result, numerical simulation, and analytic prediction have been in good agreement with each other. Theoretical approaches tell us that a bunch-length in the barrier-bucket acceleration never continues to shrink but achieves a constant value corresponding to the time duration between barrier voltages.

[1] K. Takayama and J. Kishiro, Nucl. Inst. Meth. A451/1, 304-317 (2000)[2] K. Takayama et al., “Experimental Demonstration of the Induction Synchrotron”, published soon.

 
 
WEPMA030 The Bunch Lengthening due to Electron Cloud in Positron Storage Ring electron, positron, simulation, storage-ring 366
 
  • Y. D. Liu
    IHEP Beijing, Beijing
  The electron cloud generates not only the transverse wake field but also the longitudinal wake field. The mechanism of the bunch lengthening due to longitudinal wake produced by the electron cloud in the positron storage ring is analyzed. The longitudinal field, which depends on the density of the electron cloud in the storage ring, arises from the accumulation of the electrons near to the center of the bunch during the bunch passage. Based on the longitudinal wake field, tracking method is used to simulate variation of the bunch longitudinal profile in different electron cloud density. According to simulation, the longitudinal action on the bunch from electron cloud is the similar as the potential-well distortion to shift the bunch distribution and give a rise to the bunch deformation. The result has been used to the simulation for BEPCII.  
 
THYMA01 Kickers for Injection and Extraction in Damping, Combiner and Storage Rings kicker, injection, impedance, extraction 539
 
  • F. Marcellini
    INFN/LNF, Frascati (Roma)
  Injection and extraction kickers play a fundamental role in all the projects of new major accelerators at present under study. The feasibility of these accelerators depends also on the possibility to realize kickers based on unconventional design and new technologies. This paper describes the R&D carried out at LNF on two different types of deflecting devices. The first are the kickers for the Damping Ring (DR) of the International Linear Collider (ILC) and the Storage Rings (SR) of colliders like DAFNE. They require very low impedance, good field uniformity in a wide region around the beam axis and very short pulse duration for limiting the length and consequently the cost of the DR and for reducing the perturbation of the stored bunches in SRs. The tests made on stripline prototypes, fast high voltage pulsers and vacuum feedthroughs are presented. The second are the RF kickers for the CLIC Test Facility 3 (CTF3) for which an original SW structure has been designed and realized for the Delay Loop (DL) while a more conventional TW deflector allows the multiplication of bunch current and frequency in the Combiner Ring (CR). Results of their performances are described.  
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THYMA02 Progress in Understanding the High-gradient Limitations of Accelerating Structures linear-collider, collider, emittance, linac 544
 
  • W. Wuensch
    CERN, Geneva
  CLIC main linac accelerating structures have extremely demanding high-gradient, high-power and wakefield performance requirements. The research program which has been put into place to develop such structures, as well as recent experimental and technological results are described. The current understanding of the effects which both limit the ultimate accelerating gradient and fix the practical operating gradient is presented.  
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THYMA04 Development of Quarter Wave Resonators linac, controls, coupling, vacuum 554
 
  • A. Roy
    IUAC, New Delhi
  The accelerating structure for the superconducting linac booster for the 15 UD Pelletron at IUAC is a Nb QWR cavity, designed and fabricated as a joint collaboration between IUAC and ANL, USA. Initial cavities required for the first linac module were fabricated at ANL. For fabrication of cavities required for future modules a Superconducting Resonator Fabrication Facility has been set up at IUAC. Three quarter wave resonator (QWR) cavities have been fabricated and fifteen more resonators for the second and third linac modules are in advanced stage of completion. This facility has allowed us to undertake repairs on some of the resonators which sprung leaks. First experiment with the accelerated Si beam through the first linac module having eight resonators along with a superconducting solenoid have been conducted recently.  
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THC2MA03 Design of L-band Superconducting Cavity for the Energy Recovery Linacs quadrupole, dipole, linac, simulation 570
 
  • K. Umemori, T. Furuya, S. Sakanaka, T. Suwada, T. Takahashi
    KEK, Ibaraki
  • H. Sakai, K. Shinoe
    ISSP/SRL, Chiba
  • M. Sawamura
    JAEA/ERL, Ibaraki
  The ERL project in Japan has been started with the cooperation of?KEK, JAEA, ISSP and other SR institutes. For the ERL, superconducting cavities are key components to achieve high energy, high current and low-emittance electron beams. One challenging task, required for the cavity, is a strong damping of the higher-order-modes (HOMs), since they could cause the beam-breakup instabilities and the significant heat load on the cryomodule. We are proceeding with the cavity design, which is optimized for ERLs, with concentrating our attention on HOM damping. A large diameter beam-pipe with microwave absorber is adopted as HOM damping scheme. It can extract the HOM power effectively. We have also investigated optimization of the cavity shape for further suppression of the HOMs. In this report, our cavity design and its HOM characteristics are presented.  
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THC3MA03 NSLS-II Design: A Novel Approach to Light Source Design emittance, lattice, dipole, wiggler 613
 
  • S. L. Kramer, J. Bengtsson, S. Krinsky, V. Litvinenko, S. Ozaki
    BNL, Upton, Long Island, New York
  The NSLS-II storage ring will be a replacement for the existing NSLS light source rings, which although innovative when proposed was rapidly overtaken by storage ring design capabilities. NSLS-II design[1] takes a new approach toward providing users with the brightest beams after commissioning and a strategy of evolving to higher brightness beams as more ID devices are installed during its operating period. This is achieved not by pushing the basic lattice to lower emittance, an approach that hits severe limits in the control of the dynamic aperture of an ever increasing non-linear lattice. Our approach is rather to provide the additional emittance reduction naturally with the installation of additional user undulator's or adding high power damping wigglers. Some of the damping wigglers will have variable gap and can be used to maintain a given emittance as the additional user undulators are installed. The details on the lattice design for the high brightness beams and the control of stability of these high power beams is presented.

*ozaki@bnl.gov

 
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THPMA039 300 kV/ 6 kW Power Supply System for Self-shielded Low Energy DC Accelerator at RRCAT Indore controls, power-supply, electron, cathode 679
 
  • R. Banwari, A. Kasliwal, S. Kotaiah, A. Kumar, T. G. Pandit, P. R. Peteti, A. Upadhyay
    RRCAT, Indore (M. P.)
  A compact, low energy, self-shielded dc accelerator for industrial applications requiring beam energy in the range of 100 to 300 keV is under development at RRCAT, Indore. The power supply and control system for this accelerator is discussed here in this paper. The high voltage source is a series fed cascade generator driven by a 30 kHz sine wave inverter. Two asymmetrical cascade generators are run in parallel to enhance the current capacity of the generator. A 15-0-15 kV, 30 kHz ferrite core transformer interfaces the cascade generators with IGBT based H-bridge inverter. A buck chopper controls the dc bus voltage of the inverter so as to control the terminal voltage of the high voltage generator. A low power high frequency inverter generates the filament power supply floating at terminal voltage of the accelerator through a capacitive isolation column. Control of the filament power supply is achieved by sensing the accelerator beam current and controlling the low power inverter in a closed loop. A PC based control system designed with Lab-view 7.0 software and ADUC812 Micro-converter cards monitors and displays the various parameters of the power supply and accelerator.  
 
THPMA084 A Mechanical Installation Prototype for the SSRF Storage Ring vacuum, storage-ring, dipole, quadrupole 755
 
  • L. Yin, H. W. Du, D. K. Jiang, X. Wang, Z. B. Yan, C. H. Yu, Q. G. Zhou
    SINAP, Shanghai
  The engineering design of the mechanical system for the SSRF storage ring was finished. The first group components in each system, such as the magnets, vacuum chambers, BPMs, girders and other hardware, were fabricated and tested, respectively. In order to check the overall design and the installation procedure, a lattice cell prototype was installed by using these components. Based on it, the related utility system was installed and checked. The dynamic properties of the magnet-girder assembly were also tested in this prototype. Most of the design was confirmed during the installation, but still some problems were found. The modification for the overall design and some components design has been made before their mass production. The detail design and installation of the cell installation prototype and the test results are described in this paper.  
 
FRXMA03 Achievement of ATF and its Future Plans emittance, kicker, coupling, extraction 837
 
  • J. Urakawa
    KEK, Ibaraki
  The ATF (Accelerator Test Facility at KEK) International collaboration has been launched formally under the MoU (Memorandum of Understanding) from August 1, 2005, so as to maximally contribute to the world design and development efforts in the areas of particle sources, damping rings, beam focusing and beam instrumentation towards the International Linear Collider (ILC) project. I will give a talk on the recent achievement at ATF and its future plans, especially ATF2 project.