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Paper Title Other Keywords Page
MOPA001 Advances in the Understanding and Operations of Superconducting Colliders dipole, sextupole, injection, multipole 54
  • P. Bauer, G. Annala, M.A. Martens, V.D. Shiltsev, G. Velev
    Fermilab, Batavia, Illinois
  • L. Bottura, N.J. Sammut
    CERN, Geneva
  Chromaticity drift is a well-known and more or less understood phenomenon in superconducting colliders such as the Tevatron. Less known is the effect of tune and coupling drift, also observed in the Tevatron during injection. Recently, in the context of the Tevatron collider run II, extensive studies of chromaticity, tune and coupling drifts were conducted to improve Tevatron performance. The studies included not only beam studies but also extensive off-line magnetic measurements on spare Tevatron dipoles. Some of these measurements were conducted in collaboration with Cern. Cern’s interest in multipole drifts is related to the future LHC, which will have similar issues. The following will report on the results of these studies. A new result, which will be presented here also, is related to fast drifts occurring in the first few seconds of the injection porch. These fast drifts were observed first in the Tevatron and efforts are underway to explain them. The author will also attempt to broaden the discussion to include the discussion of drift effects in the accelerating fields of superconducting linear accelerators.  
MOPA009 Global Decoupling on the RHIC Ramp quadrupole, betatron, injection, optics 659
  • Y. Luo, P. Cameron, A. Della Penna, W. Fischer, J.S. Laster, A. Marusic, F.C. Pilat, T. Roser, D. Trbojevic
    BNL, Upton, Long Island, New York
  Funding: Work supported by U.S. DOE under contract No. DE-AC02-98CH10886.

The global betatron decoupling on the ramp is an important issue for the operation of the Relativistic Heavy Ion Collider (RHIC). In the polarized proton run, the betatron tunes are required to keep almost constant on the ramp to avoid spin resonance line crossing and the beam polarization loss. Some possible correction schemes on the ramp, like three-ramp correction, the coupling amplitude modulation and the coupling phase modulaxtion, have been found. The principles of these schemes are shortly reviewed and compared. Operational results of their applications on the RHIC ramps are given.

MOPA010 Studies of the Chromaticity, Tune, and Coupling Drift in the Tevatron injection, dipole, sextupole, collider 725
  • M.A. Martens, J. Annala, P. Bauer, V.D. Shiltsev, G. Velev
    Fermilab, Batavia, Illinois
  Chromaticity drift is a well-known and more or less well-understood phenomenon in superconducting colliders such as the Tevatron. Less known is the effect of tune and coupling drift, also observed in the Tevatron during injection. These effects are caused by field drifts in the superconducting magnets. Understanding of the behavior of the tune, coupling, and chromaticity at the start of the ramp is an important part of understanding the observed 5-10% loss in beam intensity at the start of the Tevatron ramp. In addition modifications in the Tevatron shot set-up procedure are being implemented to allow for a gain in integrated luminosity. In this context we conducted several beam-studies, during the period of April to August 2004, in which we measured the drift in the Tevatron chromaticity, tune and coupling during the injection porch. In some case we also measured the snapback at the start of the ramp. We will present the results of these studies data and put them into context of the results of off-line magnetic measurements conducted in spare Tevatron dipoles at the same time. Finally we will propose optimized feed-forward algorithms that successfully compensate for the drift effects in the Tevatron.  
MPPE011 Expected Emittance Growth and Beam Tail Repopulation from Errors at Injection into the LHC emittance, injection, betatron, simulation 1266
  • B. Goddard, H. Burkhardt, V. Kain, T. Risselada
    CERN, Geneva
  The preservation of the transverse emittance of the proton beam at injection into the LHC is crucial for luminosity performance. The population of the beam tails is also important for beam losses and collimation. The transfer and injection process is particularly critical in this respect, and several effects can contribute to the expected emittance increase and tail repopulation, like optical and geometrical mismatch, injection offsets and coupling, etc. The various effects are described, together with the tolerance limits on the parameters, and the expected contributions evaluated analytically where possible. The emittance growth and tail distributions are also simulated numerically using realistic errors. The implications for the tolerances on the matching of the transfer lines are discussed.  
MPPE014 Non-Linear Beam Dynamics Studies of the Diamond Storage Ring resonance, lattice, storage-ring, vacuum 1410
  • R. Bartolini, A.I. Baldwin, M. Belgroune, I.P.S. Martin, J.H. Rowland, B. Singh
    Diamond, Oxfordshire
  • J.K. Jones
    CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire
  The non-linear beam dynamics have been investigated for the non-zero dispersion lattice of the Diamond storage ring. Effects in realistic lattice configurations such as the introduction of coupling errors, beta beating, closed orbit correction, quadrupole fringe field and in-vacuum and helical insertion devices have been studied in the presence of realistic physical aperture limitations. Frequency map analysis together with 6D tracking allows identification of the limiting resonances as well as the loss locations and calculation of the influence of non-linear longitudinal motion on the Touschek lifetime. The sensitivity of the lattice to some of these effects leads to the identification of a better working point for the machine.  
MPPE038 Synchrotron Sidebands of a Linear Differential Coupling Resonance resonance, synchrotron, betatron, storage-ring 2538
  • M. Takao, M. Masaki, J. Schimizu, K. Soutome, S. Takano, H. Tanaka
    JASRI/SPring-8, Hyogo
  Sidebands of a linear differential coupling resonance are observed in the tune survey of the SPring-8 storage ring. The vertical beam size and the Touschek beam lifetime blow up at a distance by synchrotron tune from the linear differential resonance. The synchrotron sidebands of a linear betatron coupling resonance are excited by the vertical dispersion at sextupole magnets. Although the vertical dispersion of the SPring-8 storage ring is well reduced to be small, order of 1 mm, the linear betatron coupling resonance is further suppressed. In addition, the sextupole magnets are relatively strong as well as other third generation light source facilities. Hence at the SPring-8 storage ring we can observe the synchrotron sidebands of the coupling resonance. By means of the tracking simulation based on the ring model obtained by the response matrix measurement we confirm the existence of the synchrotron sidebands of a linear differential coupling resonance. In order to incorporate synchrotron motion in the simulation, the 6-dimensional tracking code developed at SPring-8 is used.  
MPPE052 Study on Coupling Issues in the Recycler at Fermilab injection, simulation, lattice, multipole 3209
  • M. Xiao, Y. Alexahin, D.E. Johnson, M.-J. Yang
    Fermilab, Batavia, Illinois
  We have been working and trying to answer the following questions: where are the coupling sources in the Recycler and is the existing correcting system working fine? In this paper, we report the analysis on the sources from both modeling by code MAD based on nonlinear lattice and real machine. From the first turn flesh orbit, we fit the off-plane orbits by third order polynomial, then separate 1st, 2nd and 3rd order coefficients to see different effects. On the other hand, we present the analysis from turn by turn data, which is to verify the phase of two skew quads families are more or less orthogonal, and to make sure the minimum tune split is small enough, and is consistent with the measurement.  
MPPE058 Virtual Accelerator for Accelerator Optics Improvement optics, quadrupole, lattice, luminosity 3426
  • Y.T. Yan, Y. Cai, F.-J. Decker, S. Ecklund, J. Irwin, J. Seeman, M.K. Sullivan, J.L. Turner, U. Wienands
    SLAC, Menlo Park, California
  Funding: Work supported by Department of Energy contract DE-AC02-76SF00515.

Through determination of all quadrupole strengths and sextupole feed-downs by fitting quantities derivable from precision orbit measurement, one can establish a virtual accelerator that matches the real accelerator optics. These quantities (the phase advances, the Green's functions, and the coupling eigen-plane ellipses tilt angles and axis ratios) are obtained by analyzing turn-by-turn Beam Position Monitor (BPM) data with a model-independent analysis (MIA). Instead of trying to identify magnet errors, a limited number of quadrupoles are chosen for optimized strength adjustment to improve the virtual accelerator optics and then applied to the real accelerator accordingly. These processes have been successfully applied to PEP-II rings for beta beating fixes, phase and working tune adjustments, and linear coupling reduction to improve PEP-II luminosity.

MPPE059 Precision Measurement of Coupling Ellipses Parameters in a Storage Ring lattice, resonance, storage-ring, optics 3459
  • Y.T. Yan, Y. Cai
    SLAC, Menlo Park, California
  Funding: Work supported by Department of Energy contract DE-AC02-76SF00515.

Eigen-mode coupling ellipses' tilt angles and axis ratios can be precisely measured with a Model-Independent Analysis (MIA) of the turn-by-turn BPM data from resonance excitation of the betatron motion. For each BPM location one can measure 4 parameters from the two resonance excitation, which completely describe the linear coupling of the location. Results from application to PEP-II storage rings are presented.

MPPE062 Measurement and Optimization of Local Coupling from RHIC BPM Data injection, dipole, quadrupole, betatron 3553
  • R. Calaga, S. Abeytunge, M. Bai, W. Fischer
    BNL, Upton, Long Island, New York
  • F. Franchi
    GSI, Darmstadt
  • R. Tomas
    CELLS, Bellaterra (Cerdanyola del Vallès)
  Funding: U.S. Department of Energy.

Global coupling in RHIC is routinely corrected by using three skew quadrupole families to minimize the tune split. In this paper we aim to re-optimize the coupling at top energy by minimizing resonance driving terms and the C-matrix in two steps: 1. Find the best configuration of the three skew quadrupole families and 2. Identify locations with coupling sources by inspection of the driving terms and the C-matrix around the ring. The measurements of resonance terms and C-matrix are presented.

MPPE064 Dynamic Aperture Study and Lifetime Improvement at the Advanced Photon Source dynamic-aperture, sextupole, resonance, injection 3632
  • V. Sajaev, L. Emery
    ANL, Argonne, Illinois
  Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38.

Over past few years, the optics of the Advanced Photon Source storage ring was optimized to provide lower natural emittance. Presently, APS operates at 2.5 nm-rad emittance. The optimization was done at the expense of stronger sextupoles and shorter lifetime. Here we present our work on measurement and understanding the dynamic aperture of APS in low-emittance mode. We found good agreement between the dynamic aperture measurements and that of the model derived from the response matrix analysis. Based on the model, we were able to increase the lifetime significantly by optimizing sextupoles, correcting optics, moving working point, and adjusting rf voltage. The higher lifetime allowed us to decrease operating coupling from 2.5% to 1%.

MPPE065 Fully Coupled Analysis of Orbit Response Matrices at the FNAL Tevatron quadrupole, optics, storage-ring, luminosity 3662
  • V. Sajaev
    ANL, Argonne, Illinois
  • V. Lebedev, V. Nagaslaev, A. Valishev
    Fermilab, Batavia, Illinois
  Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38, and by the Universities Research Association, Inc., under contract DE-AC02-76CH03000 with the U.S. Dept. of Energy.

Optics measurements have played an important role in improving the performance of the FNAL Tevatron collider. Initial optics measurements were performed using a small number of differential orbits, which allowed us to carry out the first round of optics corrections. However, because of insufficient accuracy, it was decided to apply the response matrix analysis method for further optics improvements. The response matrix program developed at ANL has been expanded to include coupling – the essential feature required to describe the Tevatron optics. The results of the optics calibration are presented and compared to local beta function measurements.

MPPE074 Commissioning of a Locally Isochronous Lattice at ALS lattice, quadrupole, sextupole, injection 3922
  • W. Wan, W.E. Byrne, H. Nishimura, G.J. Portmann, D. Robin, F. Sannibale, A. Zholents
    LBNL, Berkeley, California
  Funding: Work supported by the Director, Office of Energy Research, Office of Basic Energy Science, Material Sciences Division, U.S. Department of Energy, under Contract No. DE-AC03-76SF00098.

With the advance of ultrafast science, manipulating electron beam at the sub-micron and nanometer scale has been actively pursued. A special lattice of the ALS storage ring was conceived to studythe sub-micron longitudinal structure of the beam. It contains sections that are isochronous to the firstorder. Due to the practical constraints of the accelerator, sextupoles have to be off and the dispersion at the injection point is 60 cm, which make commissioning a highly nontrivial task. After a few months of tuning, we have been able to store at 30 mA of beam at the life time of 2 hours. After a brief introduction to the motivation of the experiment and the design of the lattice, the process and more detailed results of the commissioning will be presented. Future plan will also be discussed.

MPPE083 Harmonic Decomposition of Orbit Data for Multipole Analysis multipole, extraction, dipole, sextupole 4120
  • M.-J. Yang
    Fermilab, Batavia, Illinois
  The unprecedented position resolution provided by the newly commissioned Recycer BPM system is opening up a new chapter of beam based multipole analysis at Fermilab. The closed orbit data, taken with circulating beam and averaged over many consecutive turns, has been shown to have the resolution of a few microns. The result of polynomial fit to BPM position data, as a function of dipole kick sizes, is used to separate orbit data into first, second, and third order. Combining both the in-plane and cross-plane orbit data it is possible to determine the multipole content within each half cell. This paper presents the algorithm behind the procedure, the data collected from the Fermilab Recycler Ring, and the final analysis result.  
MPPE084 Multipole error Analysis Using Local 3-Bump Orbit Data in Fermilab Recycler multipole, quadrupole, dipole, closed-orbit 4144
  • M.-J. Yang, M. Xiao
    Fermilab, Batavia, Illinois
  The magnetic harmonic errors of the Fermilab Recycler ring were examined using circulating beam data taken with closed local orbit bumps. Data was first parsed into harmonic orbits of first, second, and third order. Each of which was analyzed for sources of magnetic errors of corresponding order. This study was made possible only with the incredible resolution of a new BPM system that was commissioned after June of 2003.  
MPPP002 Stochastic Cooling Electrodes for a Wide Velocity Range in the CR impedance, kicker, pick-up, antiproton 799
  • F. Nolden, B.  Franzke, C. Peschke
    GSI, Darmstadt
  • M.C. Balk, R. Schuhmann, T. Weiland
    TEMF, Darmstadt
  • F. Caspers, L. Thorndahl
    CERN, Geneva
  The CR storage ring is part of the FAIR project at GSI. It serves as a first stage of stochastic cooling for secondary rare isotopes at v/c=0.83 as well as for antiprotons at v/c=0.97. To avoid the installation of dedicated structures for each kind of beam, electrodes have been developed which are usable for both beams. They are based on slotline structures mounted perpendicular to the beam. They are shorted at the ends, and their signal is extracted by two striplines on the rear side, placed a quarter wavelength away from the open ends. The width of the structures can be adjusted to the initial betatron oscillation amplitudes. Their length is 24 mm, and the signal from many of these structures mounted in a row can be combined. The signal combination can be matched to the different beam velocities. The paper shows results from field calculations, prototype tests, and estimates of the signal combination efficiency. The beam impedance of the novel structures is compared with the superelectrodes applied in the former CERN AC and with the slow-wave structures currently installed in the FNAL Debuncher.  
MPPP005 A New Kicker for the TLS Longitudinal Feedback System impedance, kicker, storage-ring, feedback 949
  • W.K. Lau, L.-H. Chang, C.W. Chen, H.Y. Chen, P.J. Chou, K.-T. Hsu, S.Y. Hsu, T.-T. Yang
    NSRRC, Hsinchu
  • M. Dehler
    PSI, Villigen
  A new longitudinal kicker that is modified from the Swiss Light Source (SLS) design to fit into the TLS storage ring. It will be served as the actuator in the longitudinal multi-bunch feedback control loop. Beam coupling impedance has been calculated by Gdfidl with a PC cluster. Previous to the installation of this new kicker, bench measurement has been performed in the laboratory to characterize this new kicker. The experimental setups for bandwidth and coaxial wire measurement of longitudinal coupling impedance and their corresponding test results will be reported. As a cross check, bead-pull measurement has also been done to verify the beam coupling measurement by coaxial wire method at the kicker center frequency. Longitudinal field profile of the accelerating mode along the beam path has also been mapped. High order cavity modes of the kicker have also been observed and their effects on the beam are evaluated.  
MPPP008 Equilibrium Beam Invariants of an Electron Storage Ring with Linear x-y Coupling resonance, damping, betatron, electron 1111
  • J. Wu, A. Chao, B. Nash
    SLAC, Menlo Park, California
  Funding: Work is supported by the U.S. Department of Energy under contract DE-AC02-76SF00515.

In accelerator systems, it is very common that the motion of the horizontal plane is coupled to that of the vertical plane. Such coupling will induce tune shifts and can cause instabilities. The damping and diffusion rates are also changed, which in turn will lead to a change in the equilibrium invariants. Following the perturbative approach which we developed for synchrobetatron coupling,* we study the x-y coupled case in this paper. Starting from the one turn map, we give explicit formulae for the tune shifts, damping and diffusion rates, and the equilibrium invariants. We focus on the cases where the system is near the integer or half integer, and sum or difference resonances where small coupling can cause a large change in the beam distribution.

*B. Nash, J. Wu, and A. Chao, work in progress.

MPPP023 Numerical Calculation of Coupling Impedances for Kicker Modules impedance, kicker, simulation, extraction 1820
  • B. Doliwa, H. De Gersem, T. Weiland
    TEMF, Darmstadt
  Funding: Work supported in part by DFG under contract GraKo 410 and GSI, Darmstadt.

Maintaining the impedance budget is an important task in the planning of any new accelerator facility. While estimates from analytical computations and measurements play a central role in doing so, numerical calculations have become an important alternative today. On the basis of Finite Integration Theory, we have developed a simulation tool for the direct computation of coupling impedances in the frequency domain. After discussing the special features of our code as compared to commercial programs, we present our results for cases where coupling impedances have been obtained from another source, e.g. experiment. In particular, we consider the longitudinal and transverse impedances of the SNS extraction kicker and present investigations related to the injection/extraction system of the future heavy-ion synchrotron at GSI.

MPPP026 Development of Longitudinal Coupling Impedance Measurement Platform for BEPCII impedance, insertion, storage-ring, controls 1940
  • G. Huang, W.-H. Huang, S. Zheng
    Tsinghua University, Beijing
  • J.Q. Wang, D.M. Zhou
    IHEP Beijing, Beijing
  Funding: Supported by NSFC 10375035.

A coaxial line impedance measurement platform is developed for BEPCII. A pair of gradual change impedance matching section is designed and fabricated by numerical control milling machine. The special designed RF connector is applied to strengthen the inner conductor. The algorithm of TRL calibration is applied in the system to avoid the usage of a reference pipe for each device under test. The measurement is accomplished by a VNA under the control of the software written in LabView.

MPPP030 Analytic Evaluation of the Series over Azimuthal Harmonics at the Analysis of the Stability of Bunched Beams Coherent Oscillations impedance, multipole, synchrotron, RF-structure 2149
  • N. Mityanina
    BINP SB RAS, Novosibirsk
  At the analysis of the stability of coherent motion of multibunch beams including counterrotating beams) one should deal with expressions analogous to the effective impedance - the serieses over harmonics of revolution frequency of the RF structure impedance at the side frequencies to these harmonics, with certain factors depending on the harmonic number, such as the bunch line density spectrum, the phase factor and the factor describing the order of multipole synchrotron oscillations. In this paper, we present the method for analytic summation of these serieses for resonant impedance, which seems not to be made before in the common case including all mentioned factors. Comparison of obtained expressions with formulae used in previous papers shows the limits of validity of simpler approaches. The obtained expressions are used in the computer codes MBIM1 and MBIM2 presented at this conference, which calculate coherent oscillations stability for arbitrary multibunch beams.  
MPPT040 The LHC Magnetic Field Model injection, dipole, sextupole, superconducting-magnet 2648
  • N.J. Sammut, L. Bottura
    CERN, Geneva
  • J. Micallef
    University of Malta, Faculty of Engineering, Msida
  The compensation of the dynamic field changes during the proton and ion beam injection and acceleration in the LHC requires an accurate forecast and an active control of the magnetic field in the accelerator. The LHC Magnetic Field Model is the core of this magnetic prediction system. This open loop control scheme will provide the desired field components at a given time, magnet operating current, magnet ramp-rate, magnet temperature and magnet powering history to the required precision. The model is based on the identification and physical decomposition of the effects that contribute to the total field in the magnet aperture of the LHC dipoles. By using data obtained from series measurements, these components are then quantified theoretically or empirically depending on the complexity of the physical phenomena involved. This paper presents the developments of the newly fine-tuned magnetic field model and evaluates its accuracy, reproducibility and predicting capabilities.  
MPPT053 Restoring the Skew Quadrupole Moment in Tevatron Dipoles quadrupole, dipole, betatron 3244
  • D.J. Harding, P. Bauer, J.N. Blowers, J. DiMarco, H.D. Glass, R. Hanft, J.A. John, W.F. Robotham, M. Tartaglia, J. Tompkins, G. Velev
    Fermilab, Batavia, Illinois
  Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-76CH03000.

In early 2003 it was realized that mechanical changes in the Tevatron dipoles had led to a deterioration of the magnetic field quality that was hindering operation of the accelerator. After extensive study, a remediation program was started in late 2003 which will continue through 2005. The mechanical and magnetic effects are discussed. The readjustment process and experience are reported, along with other observations on aging magnets.

MPPT058 Progress on the Focus Coils for the MICE Channel focusing, vacuum, emittance, power-supply 3417
  • M.A. Green
    LBNL, Berkeley, California
  • Y. Ivanyushenkov
    CCLRC/RAL, Chilton, Didcot, Oxon
  • W. Lau, R. Senanayake, S.Q. Yang
    OXFORDphysics, Oxford, Oxon
  Funding: This work was supported by the Office of Science, U.S. Department of Energy under DOE contract number DE-AC03-76SF00098.

This report describes the progress on the magnet part of the absorber focus coil module for the international Muon Ionization Cooling Experiment (MICE). MICE consists of two cells of a SFOFO cooling channel that is similar to that studied in the level 2 study of a neutrino factory. The MICE absorber focus coil module consists of a pair of superconducting solenoids, mounted on an aluminum mandrel. The coil package that is in its own vacuum vessel surrounds an absorber, which does the ionization cooling of the muons. Either a liquid or solid absorber is within a separate vacuum vessel that is within the warm bore of the superconducting magnet. The superconducting focus coils may either be run in the solenoid mode (with the two coils at the same polarity) or in the flip mode (with the coil at opposite polarity causing the field direction to flip within the magnet bore). The superconducting coils will be cooled using a pair of small 4 K coolers. This report discusses the progress on the MICE focusing magnets, the magnet cooling system and the magnet current supply system.

MPPT059 Progress on the Coupling Coil for the MICE Channel focusing, vacuum, power-supply, superconductivity 3468
  • M.A. Green, D. Li, S.P. Virostek, M.S. Zisman
    LBNL, Berkeley, California
  • Y. Ivanyushenkov
    CCLRC/RAL, Chilton, Didcot, Oxon
  • W. Lau, A. E. White, H. Witte, S.Q. Yang
    OXFORDphysics, Oxford, Oxon
  Funding: This work was supported by the Office of Science, U.S. Department of Energy under DOE contract number DE-AC03-76SF00098.

This report describes the progress on the coupling coil module for the international Muon Ionization Cooling Experiment (MICE). MICE consists of two cells of a SFOFO cooling channel that is similar to that studied in the level 2 study of a neutrino factory. The MICE RF coupling coil module consists of a superconducting solenoid, mounted around four cells of conventional 201.25 MHz closed RF cavities. This report discusses the progress that has been made on the superconducting coupling coil that is around the center of the RF coupling module. This report also describes the process one would use to cool the coupling coil using a single small 4 K cooler. The coupling magnet power system and quench protections system is also described.

TOAC001 Overview of Impedance and Single-Beam Instability Mechanisms impedance, synchrotron, damping, octupole 14
  • E. Métral
    CERN, Geneva
  Single-bunch and coupled-bunch instability mechanisms will be reviewed in both longitudinal and transverse planes. The resistive-wall impedance will be discussed in the particular case of the LHC collimators, which reveal a new physical regime. Stabilization by Landau damping, feedbacks, or linear coupling between the transverse planes will also be treated. Benchmarking of analytical predictions with some instability codes will be shown as well as several experimental results.  
TOAA009 Recent Test Results of the Fast-Pulsed 4 T COSO Dipole GSI 001 dipole, sextupole, synchrotron, injection 683
  • G. Moritz, J. Kaugerts
    GSI, Darmstadt
  • B. Auchmann, S. Russenschuck, R. de Maria
    CERN, Geneva
  • J. Escallier, G. Ganetis, A.K. Jain, A. Marone, J.F. Muratore, R.A. Thomas, P. Wanderer
    BNL, Upton, Long Island, New York
  • M. Wilson
    Oxford Instruments, Accelerator Technology Group, Oxford, Oxon
  For the FAIR-project at GSI a model dipole was built at BNL with the nominal field of 4 T and a nominal ramp rate of 1 T/s. The magnet design was similar to the RHIC dipole with some changes for loss reduction and better cooling. The magnet was already successfully tested in a vertical cryostat with good training behaviour. Cryogenic losses were measured and first results of field harmonics were published. However, for a better understanding of the cooling process quench currents at several ramp rates were investigated. Detailed measurements of the field harmonics at different ramp rates and at several cycles were performed. To separate the effects of the coil and the iron yoke the magnet was disassembled and tested as collared coil only. Recent test results will be presented.  
TPAE013 Rectangular Dielectric-Lined Two-Beam Wakefield Accelerator Structure acceleration, radiation, vacuum, extraction 1333
  • C. Wang, V.P. Yakovlev
    Omega-P, Inc., New Haven, Connecticut
  • J.L. Hirshfield
    Yale University, Physics Department, New Haven, CT
  • T.C. Marshall
    Columbia University, New York
  Funding: Work supported by U.S. DOE.

A novel dielectric structure is described for a two-beam wake field accelerator (WFA), which consists of three or four rectangular dielectric slabs positioned within a rectangular conducting pipe. This structure can be thought of as equivalent to two symmetric dielectric-lined three-zone rectangular waveguides, joined side-by-side. The design mode in the two-beam structure is the LSM-31 mode, a combination of two symmetric LSM-11 modes of the two three-zone waveguides. This two-channel mode can be employed to decelerate drive particles in one channel and accelerate test particles in the other. It is possible to find structure parameters that give a high ratio of acceleration gradient for the test beam, to deceleration gradient for the drive beam, of the order of 100.

TPAE030 Distributed Bragg Coupler for Optical All-Dielectric Electron Accelerator laser, electron, vacuum, radiation 2125
  • Z. Zhang, R.D. Ruth, S.G. Tantawi
    SLAC, Menlo Park, California
  Funding: Department of Energy.

A Bragg waveguide consisting of multiple dielectric layers with alternating index of refraction becomes an excellent option to form electron accelerating structure powered by high power laser sources. It provides confinement of a synchronous speed-of-light mode with extremely low loss. However, laser field can not be coupled into the structure collinearly with the electron beam. There are three requirements in designing input coupler for a Bragg electron accelerator: side-coupling, selective mode excitation, and high coupling efficiency. We present a side coupling scheme using a Bragg-grating-assisted input coupler to inject the laser into the waveguide. Side coupling is achieved by a second order Bragg grating with a period on the order of an optical wavelength. The phase matching condition results in resonance coupling thus providing selective mode excitation capability. The coupling efficiency is limited by profile mismatch between the outgoing beam and the incoming beam, which has normally, a Gaussian profile. We demonstrate a non-uniform distributed grating structure generating an outgoing beam with a Gaussian profile, therefore, increasing the coupling efficiency.

TPAE031 Simulations of Laser Pulse Coupling and Transmission Efficiency in Plasma Channels laser, plasma, simulation, diagnostics 2179
  • R. Giacone, D.L. Bruhwiler, J.R. Cary, D.A. Dimitrov, P. Messmer
    Tech-X, Boulder, Colorado
  • E. Esarey, C.G.R. Geddes, W. Leemans
    LBNL, Berkeley, California
  Funding: Work supported by U.S. DOE under contracts DE-FG03-02ER83557, DE-FC02-01ER41178, DE-AC03-76SF00098, DE-FG03-95ER40926 and use of NERC supercomputer facilities.

Optical guiding of the laser pulse in a laser wakefield accelerator (LWFA) via plasma channels can greatly increase the interaction length and, hence, the maximun energy of trapped electrons.* Energy efficient coupling of laser pulses from vacuum into plasma channels is very important for optimal LWFA performance. We present 2D particle-in-cell simulations of this problem using the VORPAL code.** Some of the mechanisms considered are enhanced leakage of laser energy transversely through the channel walls, enhanced refraction due to tunneling ionization of neutral gas on the periphery of the gas jet, ionization of neutral gas by transverse wings of the laser pulse and effect of the pulse being off axis of the channel. Using power spectral diagnostics,*** we are able to differentiate between pump depletion and leakage from the channel. The results from our simulations show that for short (≈λp) plasma ramp, very little leakage and pump depletion is seen. For narrow channel walls and long ramps, leakage increases significantly.

*C. G. R. Gedes et al., Nature 431 (2004), p. 538. **C. Nieter and J. R. Cary, J. Comp. Phys. 196 (2004), p. 448.***D. A. Dimitrov et al., Proc. Advanced Accel. Concepts Workshop (2004).

TPAE051 Designing Photonic Crystal Devices for Accelerators lattice, simulation, electron, photon 3164
  • G.R. Werner
    CIPS, Boulder, Colorado
  • J.R. Cary
    Tech-X, Boulder, Colorado
  Funding: This work supported by U.S. Department of Energy grant DE-FG02-04ER41317.

Photonic crystals (periodic dielectric structures with a lattice constant on the order of the wavelength of light) can have a wide range of properties. For instance, photonic crystals can be designed to be completely reflective within a certain bandwidth, thereby becoming a replacement for metal in accelerator structures such as waveguides and cavities. To see whether photonic crystals might find application in accelerators, and to design potential accelerator structures, we will need reliable computer simulations to predict fields and frequencies and other properties of photonic crystal structures. We propose to build photonic crystal structures in the microwave regime and test the validity of computer simulation against experiment. We can then explore more complex issues such as coupling to photonic crystal structures, higher-order mode rejection, and tunable photonic crystals.

TPAP018 Optics Studies of the LHC Beam Transfer Line TI8 optics, quadrupole, extraction, emittance 1578
  • J. Wenninger, G. Arduini, B. Goddard, D. Jacquet, V. Kain, M. Lamont, V. Mertens, J.A. Uythoven
    CERN, Geneva
  • Y.-C. Chao
    Jefferson Lab, Newport News, Virginia
  The optics of the newly commissioned LHC beam transfer line TI 8 was studied with beam trajectories, dispersion and profile measurements. Steering magnet response measurements were used to analyze the quality of the steering magnets and of the beam position monitors. A simultaneous fit of the quadrupole strengths was used to search for setting or calibration errors. Residual coupling between the planes was evaluated using high statistics samples of trajectories. Initial conditions for the optics at the entrance of the transfer line were reconstructed from beam profile measurements with Optical Transition Radiation monitors. The paper presents the various analysis methods and their errors. The expected emittance growth arising from optical mismatch into the LHC is evaluated.  
TPAP020 Tests of a Roman Pot Prototype for the TOTEM Experiment impedance, insertion, vacuum, scattering 1701
  • M. Deile, E. Alagoz, G.M. Anelli, G.A. Antchev, M. Ayache, F. Caspers, E. Dimovasili, R. Dinapoli, F.D. Drouhin, K. Eggert, L. Escourrou, O. Fochler, K. Gill, R. Grabit, F. Haug, P. Jarron, J. Kaplon, T. Kroyer, T. Luntama, D. Macina, E. Mattelon, L. Mirabito, H. Niewiadomski, E.P. Noschis, M. Oriunno, A. Park, A.-L. Perrot, O. Pirotte, J.M. Quetsch, F. Regnier, G. Ruggiero, S. Saramad, P. Siegrist, W. Snoeys, T. Souissi, R. Szczygiel, J. Troska, F. Vasey, A. Verdier
    CERN, Geneva
  • V. Avati, M. Järvinen, M. Kalliokoski, J. Kalliopuska, K. Kurvinen, R. Lauhakangas, F. Oljemark, R. Orava, V. Palmieri, H. Saarikko, A. Soininen, K. Österberg
    Helsinki University, Department of Physics, University of Helsinki
  • V. Berardi, M.G. Catanesi, E. Radicioni
    INFN-Bari, Bari
  • V. Boccone, M. Bozzo, A. Buzzo, S. Cuneo, F. Ferro, M. Macri, S. Minutoli, A. Morelli, P. Musico, M. Negri, A. Santroni, G. Sette, A. Sobol
    INFN Genova, Genova
  • C. Da Vià, J. Hasi, A. Kok, S. Watts
    Brunel University, Middlesex
  • J. Kasper, V. Kundrât, M. V. Lokajicek, J. Smotlacha
    FZU, Prague
  The TOTEM collaboration has developed and tested the first prototype of its Roman Pots to be operated in the LHC.* TOTEM Roman Pots contain stacks of 10 silicon detectors with strips oriented in two orthogonal directions. To measure proton scattering angles of a few microradians, the detectors will approach the beam centre to a distance of 10 σ + 0.5 mm (= 1.3 mm). Dead space near the detector edge is minimised by using two novel "edgeless" detector technologies. The silicon detectors are used both for precise track reconstruction and for triggering. The first full-sized prototypes of both detector technologies as well as their read-out electronics have been developed, built and operated. The tests took place first in a fixed-target muon beam at CERN's SPS, and then in the proton beam-line of the SPS accelerator ring. We present the test beam results demonstrating the successful functionality of the system despite slight technical shortcomings to be improved in the near future.

TOTEM, Technical Design Report, CERN-LHCC-2004-002.

TPAP027 Deterioration of the Skew Quadrupole Moment in Tevatron Dipoles Over Time quadrupole, dipole, alignment, monitoring 1967
  • M.J. Syphers, D.J. Harding
    Fermilab, Batavia, Illinois
  Funding: United States Department of Energy under Contract No. DE-AC02-76CH03000.

During the 20 years since it was first commissioned, the Fermilab Tevatron has developed strong coupling between the two transverse degrees of freedom. A circuit of skew quadrupole magnets is used to correct for coupling and, though capable, its required strength has increased since 1983 by more than an order of magnitude. In more recent years changes to the Tevatron for colliding beams operation have altered the skew quadrupole corrector distribution and strong local coupling become evident, often encumbering routine operation during the present physics run. Detailed magnet measurements were performed on each individual magnet during construction, and in early 2003 it was realized that measurements could be performed on the magnets in situ which could determine coil movements within the iron yoke since the early 1980's. It was discovered that the superconducting coils had become vertically displaced relative to their yokes since their construction. The ensuing systematic skew quadrupole field introduced by this displacement accounts for the required corrector settings and observed beam behavior. An historical account of the events leading to this discovery and progress toward its remedy are presented.

TPAP028 Observations of Strong Transverse Coupling in the Tevatron quadrupole, dipole, betatron, collider 2029
  • M.J. Syphers, G. Annala, D.A. Edwards, N.M. Gelfand, J.A. Johnstone, M.A. Martens, T. Sen
    Fermilab, Batavia, Illinois
  Funding: United States Department of Energy under Contract No. DE-AC02-76CH03000.

During the beginning of Run II of the Tevatron Collider it became apparent that a large skew quadrupole source, or sources, had developed in the superconducting synchrotron. Efforts to locate the current source of coupling were undertaken, with the eventual discovery that the main magnets had developed a systematic skew quadrupole moment over their lifetime. Over the past year, the magnets have been altered in place in an attempt to restore the systematic skew quadrupole moment to zero. Beam observations and their interpretations are presented, and remedial measures are discussed.

TPAP051 Principle of Global Decoupling with Coupling Angle Modulation quadrupole, simulation, injection, betatron 3132
  • Y. Luo, S. Peggs, F.C. Pilat, T. Roser, D. Trbojevic
    BNL, Upton, Long Island, New York
  Funding: Work supported by U.S. DOE under contract No. DE-AC02-98CH10886.

The global betatron decoupling on the ramp is an important issue for the operation of the Relativistic Heavy Ion Collider (RHIC). A new scheme coupling phase modulation is found. It introduces a rotating extra coupling into the coupled machine to detect the residual coupling. The eigentune responses are measured with a high resolution phase lock loop (PLL) system. From the minimum and maximum tune splits, the correction strengths are given. The time period occupied by one coupling phase modulation is less than 10 seconds. So it is a very promising solution for the global decoupling on the ramp. In this article the principle of the coupling phase modulation is given. The simulation with the smooth accelerator model is also done. The practical issues concerning its applications are discussed.

TPAP052 Possible Phase Loop for the Global Decoupling quadrupole, feedback, simulation, collider 3182
  • Y. Luo, P. Cameron, A. Della Penna, A. Marusic, S. Peggs, T. Roser, D. Trbojevic
    BNL, Upton, Long Island, New York
  • O.R. Jones
    CERN, Geneva
  Funding: Work supported by U.S. DOE under contract No. DE-AC02-98CH10886.

Besides two eigentunes Q1 and Q2 , two amplitude ratios r1 and r2 and two phase differences ∆ φ1 and ∆ φ2 are introduced for the global coupling observation. Simulations are carried out to check their behaviors in the process of the skew quadrupole strength scans. Some attractive features of the phase differences ∆ φ1,2 have been found, which are possibly useful for the global decoupling phase loop, or future global decoupling feedback. Analytical descriptions to these 6 quantities are described in the Twiss parameters through the linear coupling's action-angle parameterization, or in coupling coefficient through the linear coupling's Hamiltonian perturbation theory. Dedicated beam experiments are carried out at the Relativistic Heavy Ion Collider (RHIC) to check the global coupling observables from the phase lock loop (PLL) system. The six observables are measured under PLL driving oscillations during the 1-D and 2-D skew quadrupole scans. The experimental results are reported and discussions are given.

TPAP053 IR Optics Measurement with Linear Coupling's Action-Angle Parameterization optics, dipole, background, heavy-ion 3218
  • Y. Luo, M. Bai, F.C. Pilat, T. Satogata, D. Trbojevic
    BNL, Upton, Long Island, New York
  Funding: Work supported by U.S. DOE under contract No. DE-AC02-98CH10886.

The interaction region (IP) optics are measured with the two DX/BPMs close to the IPs at the Relativistic Heavy Ion Collider (RHIC). The beta functions at IP are measured with the two eigenmodes' phase advances between the two BPMs. And the beta waists are also determined through the beta functions at the two BPMs. The coupling parameters at the IPs are also given through the linear coupling's action-angle parameterization. All the experimental data are taken during the driving oscillations with the AC dipole. The methods to do these measurements are discussed. And the measurement results during the beta* squeezings are also presented.

TPAP055 Fast IR orbit feedback at RHIC feedback, power-supply, luminosity, emittance 3298
  • C. Montag, A. Marusic, R.J. Michnoff, T. Roser, T. Satogata, C. Schultheiss
    BNL, Upton, Long Island, New York
  Funding: Work performed under the auspices of the US Department of Energy

Mechanical low-beta triplet vibrations lead to horizontal jitter of RHIC beams at frequencies around 10 Hz. The resulting beam offsets at the interaction points are considered detrimental to RHIC luminosity performance. To stabilize beam orbits at the interaction points, installation of a fast orbit feedback is foreseen. A prototype of this system is being developed and tested. Recent results are presented.

TPAT046 Nonlinear Stability of Intense Mismatched Beams in a Uniform Focusing Field focusing, space-charge, emittance, beam-losses 2941
  • R. Pakter, F.B. Rizzato, W. Simeoni
    IF-UFRGS, Porto Alegre
  Funding: Work supported by Brazilian agencies CNPq, CAPES, and FAPERGS.

We investigate the nonlinear coupling between axisymmetric and elliptic oscillations in the dynamics of intense beams propagating in a uniform magnetic focusing field. It is shown that finite amplitude mismatched oscillations of an initially round beam may destabilize elliptic oscillations, heavily affecting stability and the shape of the beam. This is a potential mechanics for beam particle loss in such systems. Self consistent simulations are performed to verify the findings.

TPAT072 Long-Term Simulation of Beam-Beam Effects in the Tevatron at Collision Energy simulation, lattice, antiproton, beam-beam-effects 3871
  • A.C. Kabel, Y. Cai
    SLAC, Menlo Park, California
  • T. Sen
    Fermilab, Batavia, Illinois
  The weak-strong beam-beam effect is expected substantially to contribute to the degradation of beam lifetimes in the Tevatron at collision energy. We have expanded an existing multi-processor code (which previously was applied to the Tevatron at injection energy* to include chromatic and non-linear lattice effects as well as a fully-coupled treatment of the lattice in different approximations.** We obtain lifetime predictions by doing temporal statistics on the tracking results of a weighted macroparticle distribution and fitting it to a class of solutions for the diffusion equation. We present typical results of parameter scans.

*A. Kabel, Y. Cai, B. Erdelyi, T. Sen, M. Xiao; Proceedings of PAC03. **A. Kabel, this Conference.

TPAT078 Coherent Beam-Beam Modes in the CERN Large Hadron Collider (LHC) for Multiple Bunches, Different Collisions Schemes and Machine Symmetries simulation, damping, emittance, dipole 4030
  • T. Pieloni, W. Herr
    CERN, Geneva
  In the LHC almost 3000 bunches in each beam will collide near several experimental regions and experience head-on as well as long range beam-beam interactions. In addition to single bunch phenomena, coherent bunch oscillations can be excited. Due to the irregular filling pattern and the unsymmetric collision scheme, a large number of possible modes must be expected, with possible consequences for beam measurements. To study these effects, a simulation program was developped which allows to evaluate the interaction of many bunches. It is flexible enough to easily implement any possible bunch configuration and collision schedule and also to study the effect of machine imperfections such as optical asymmetries. First results will be presented and future developments are discussed.  
TPAT079 Importance of the Linear Coupling and Multipole Compensation of Long-Range Beam-Beam Interactions In Tevatron emittance, multipole, beam-beam-effects, simulation 4039
  • J. Shi, B. Anhalt
    KU, Lawrence, Kansas
  Funding: The US Department of Energy under Grant No. DE-FG02-04ER41288.

In Tevatron, serious long-range beam-beam effects are due to many parasitic collisions that are distributed around the ring. Because of this non-localized nature of long-range beam-beam interactions, the multipole compensation with one-turn or sectional maps aims a global compensation of long-range beam-beam interactions. Since nonlinear beam dynamics in a storage ring can usually be described by a one-turn map that contains all global information of system nonlinearities, by minimizing nonlinear terms of the maps order-by-order with a few groups of multipole correctors, one could reduce the nonlinearity globally. Since a large beam separation is typical at parasitic points, in the phase-space region that is relevant to the beam, long-range beam-beam interactions can be expanded into a Taylor series around the beam separation and be included into the one-turn map for the global compensation. To examine the effect of this multipole compensation scheme, the emittance growth of both p and pbar beam in Tevatron were studied with a beam-beam simulation. The result showed that the multipole compensation can significantly reduces the emittance growth of the pbar beam due to long-range beam-beam interactions.

TPAT082 Phonon Modes and the Maintenance Condition of a Crystalline Beam lattice, resonance, focusing, emittance 4111
  • J. Wei
    BNL, Upton, Long Island, New York
  • H. Enokizono, H. Okamoto, Y. Yuri
    HU/AdSM, Higashi-Hiroshima
  • X.-P. Li
    Skyworks Solutions, Inc., Newbury Park. California
  • A. Sessler
    LBNL, Berkeley, California
  Funding: * Work performed under the auspices of the U.S. Department of Energy.

Previously it has been shown that the maintenance condition for a crystalline beam requires that there not be a resonance between the crystal phonon frequencies and the frequency associated with a beam moving through a lattice of N periods. This resonance can be avoided provided the phonon frequencies are all below half of the lattice frequency. Here we make a detailed study of the phonon modes of a crystalline beam. Analytic results obtained in a “smooth approximation” using the ground-state crystalline beam structure is compared with numerical evaluation employing Fourier transform of Molecular Dynamic (MD) modes. The MD also determines when a crystalline beam is stable. The maintenance condition, when combined with either the simple analytic theory or the numerical evaluation of phonon modes, is shown to be in excellent agreement with the MD calculations of crystal stability.

[1] X-P. Li, A. M. Sessler, J. Wei, EPAC (1994) p. 1379 - 1381. ‘Necessary Conditions for Attaining a Crystalline Beam''}[2] J. Wei, H. Okamoto, A.M. Sessler, Phys. Rev. Lett., Vol. 80, p. 2606-2609 (1998).

TOPC002 Residual-Gas-Ionization Beam Profile Monitors in RHIC emittance, electron, background, heavy-ion 230
  • R. Connolly, R.J. Michnoff, S. Tepikian
    BNL, Upton, Long Island, New York
  Funding: Work performed under Contract #DE-AC02-98CH10886 under the auspices of the U.S. Department of Energy.

Four ionization profile monitors (IPMs) are in RHIC to measure vertical and horizontal beam profiles in the two rings. These work by measuring the distribution of electrons produced by beam ionization of residual gas. During the last two years both the collection accuracy and signal/noise ratio have been improved. An electron source is mounted across the beam pipe from the collector to monitor microchannel plate (MCP) aging and the signal electrons are gated to reduce MCP aging and to allow charge replenishment between single-turn measurements. Software changes permit simultaneous measurements of any number of individual bunches in the ring. This has been used to measure emittance growth rates on six bunches of varying intensities in a single store. Also the software supports FFT analysis of turn-by-turn profiles of a single bunch at injection to detect dipole and quadrupole oscillations.

TPPE040 RF and Magnetic Measurements on the SPARC Photoinjector and Solenoid at UCLA gun, emittance, cathode, linac 2624
  • J.B. Rosenzweig, A.M. Cook, M.P. Dunning, P. Frigola, G. Travish
    UCLA, Los Angeles, California
  • D.T. Palmer
    SLAC, Menlo Park, California
  • C. Sanelli, F. Tazzioli
    INFN/LNF, Frascati (Roma)
  Funding: This work is supported by U.S. Dept. of Energy grant DE-FG03-92ER40693.

The rf photocathode gun and the solenoid for the SPARC project at INFN-LNF (Frascati) have been fabricated and undergone initial testing at UCLA. The advanced aspects of the design of these devices are detailed. Final diagnosis of the tuning of the RF gun performance, including operating mode frequency and field balance, is described. The emittance compensating solenoid magnet, which is designed to be tuned in longitudinal position by differential excitation of the coils, has been measured using Hall probe scans for field profiling, and pulsed wire methods to determine the field center.

TPPE045 Normal-Conducting High Current RF Photoinjector for High Power CW FEL vacuum, emittance, rfq, simulation 2866
  • S.S. Kurennoy, D.C. Nguyen, D.L. Schrage, R.L. Wood
    LANL, Los Alamos, New Mexico
  • V. Christina, J. Rathke, T. Schultheiss
    AES, Medford, NY
  • L.M. Young
    TechSource, Santa Fe, New Mexico
  An RF photoinjector capable of producing high average current with low emittance and energy spread is a key enabling technology for high power CW FEL. The design of a 2.5-cell, pi-mode, 700-MHz normal-conducting RF photoinjector cavity with magnetic emittance compensation is completed. With average gradients of 7, 7, and 5 MV/m in its three accelerating cells, the photoinjector will produce a 2.5-MeV electron beam with 3-nC charge per bunch and transverse rms emittance below 7 mm-mrad. Electromagnetic modeling has been used extensively to optimize ridge-loaded tapered waveguides and RF couplers, and led to a new, improved coupler iris design. The results, combined with a thermal and stress analysis, show that the challenging problem of cavity cooling can be successfully solved. Fabrication of a demo 100-mA (at 35 MHz bunch repetition rate) photoinjector is underway. The design is scalable to higher average currents by increasing the electron bunch repetition rate, and provides a path to a MW-class FEL. This paper presents the cavity design and details of RF coupler modeling.  
TPPE058 Dual Feed RF Gun Design for the LCLS gun, quadrupole, laser, dipole 3432
  • L. Xiao, R.F. Boyce, D. Dowell, Z. Li, C. Limborg-Deprey, J.F. Schmerge
    SLAC, Menlo Park, California
  Funding: Work supported by the U.S. DOE under contract DE-AC03-76SF00515.

In order to remove the dipole field introduced by the coupler in existing S-band BNL/SLAC/UCLA 1.6 cell rf gun, a dual feed design for the LCLS RF gun is proposed together with several significant changes. The improvements include adopting Z-coupling instead of ?-coupling for easier machining and reducing heating, increasing the 0-and ?-mode separation from 3.4 to 15 MHz to reduce the amplitude of the 0 mode, incorporating race-track cavity shape to minimize the quadruple fields, increased cooling for operation at 120Hz and other small changes to improve performance and diagnostic capabilities. The new design has been modeled with the parallel finite element eigenmode solver Omega3P to provide the desired RF parameters and to generate the gun cavity dimensions needed for fabrication.

TPPE061 RF Design and Operating Performance of the BNL/AES 1.3 GHz Single Cell Superconducting RF Photocathode Electron Gun gun, cathode, electron, superconducting-RF 3514
  • M.D. Cole
    AES, Medford, NY
  • I. Ben-Zvi, A. Burrill, H. Hahn, T. Rao, Y. Zhao
    BNL, Upton, Long Island, New York
  • P. Kneisel
    Jefferson Lab, Newport News, Virginia
  Over the past several years Advanced Energy Systems and BNL have been collaborating on the development and testing of a fully superconducting photocathode electron gun. Over the past year we have begun to realize significant results which have been published elsewhere.* This paper will review the RF design of the gun under test and present results of its performance under various operating conditions. Results for cavity quality factor will be presented for various operating temperatures and cavity field gradients. We will discuss various methods of determining the cavity fields and the extent of agreement between them. We will also discuss future plans for testing using this gun.

*Photoemission studies on BNL/AES all niobium, Superconducting RF injector, T. Rao, these proceedings.

TPPE065 Calculating of Coupling Factor of Microwave Electron Gun simulation, gun, electron, cathode 3656
  • X. Bian, H. Chen, S. Zheng
    TUB, Beijing
  • D. Li
    LBNL, Berkeley, California
  To design the coupler of a designing microwave electron gun, we use the "energy method" proposed by Derun Li, et al. The intrinsic Q of the electron gun cavity is very high: about 20000. The method calculates the intrinsic and external Q values of a cavity coupled to a waveguide using MAFIA code in time domain. The comparisons between simulation and experimental results are given for a set of different coupling iris apertures and height. The result shows that "energy method" works efficiently for high Q cavities.  
TPPP003 Lattice Upgrade Plan for Crab Crossing at the KEKB Rings lattice, quadrupole, luminosity, optics 865
  • A. Morita, K. Egawa, K. Hosoyama, H. Koiso, T. Kubo, M. Masuzawa, K. Ohmi, K. Oide, R. Sugahara, M. Yoshida
    KEK, Ibaraki
  We plan to install two superconducting crab cavities into the rings at Janyary, 2006. In our plan, we will install one crab cavity per one ring into the NIKKO straight section where the cryogenic infrastructure is already operated for the superconducting accelerating cavities. In order to obtain the correct crabbing angle at the interaction point(IP), we have to enlarge the horizontal beta function(200m for HER) and have to adjust the horizontal phase advance between the IP and the cavity installation point. In this paper, we will report the lattice modified for the crab crossing and the study results about the single beam dynamics.  
TPPP004 Study of the Beam-Beam Effect for Crab Crossing in KEKB and Super KEKB luminosity, damping, radiation, simulation 925
  • K. Ohmi, Y. Funakoshi, M. Tawada
    KEK, Ibaraki
  Luminosity upgrade using crab cavities is planned at KEK-B factory (KEKB)in 2006. The crab crossing is expected to increase the beam-beam parameter >0.1, which is twice of present value, for KEKB. We discuss torelances of crab cavities and lattice to get the high beam-beam parameter.  
TPPP028 Simulation of HOM Leakage in the PEP-II Bellows vacuum, damping, simulation, higher-order-mode 2050
  • C.-K. Ng, N.T. Folwell, L. Ge, J. Langton, L. Lee, A. Novokhatski
    SLAC, Menlo Park, California
  Funding: Work supported by U.S. DOE contract, DE-AC02-76SF00515.

An important factor that limits the PEP-II from operating at higher currents is higher-order-mode (HOM) heating of the bellows. One source of HOM heating is the formation of trapped modes at the bellows as a result of geometry variation in the vacuum chamber, for example, the masking near the central vertex chamber. Another source comes from HOMs generated upstream that leak through the gaps between the bellows fingers. Modeling the fine details of the bellows and the surrounding geometry requires the resolution and accuracy only possible with a large number of mesh points on an unstructured grid. We use the parallel finite element eigensolver Omega3P for trapped mode calculations, and the S-matrix solver S3P for transmission analysis. The damping of the HOMs by the use of absorbers inside the bellows will be investigated.

TPPT006 Development of RF Input Coupler with a Coaxial Line TiN-Coated Against Multipactoring vacuum, simulation, electron, linac 1006
  • T. Abe, T. Kageyama, H. Sakai, Y. Takeuchi
    KEK, Ibaraki
  In one of the normal-conducting RF cavities used in the KEKB operation, we observed an unexpected rise of the vacuum pressure at certain input-power levels with and without a beam current. From the simulation study, we identify the pressure rises as an effect of the multipactoring discharge in the coaxial line of the input coupler. According to the simulation results, we have decided to make TiN coating on the inner surface of the outer conductor to suppress the multipactoring. In this paper, the status of the development of the TiN-coated input coupler is reported including the recent results of the high-power tests.  
TPPT007 Application of Highly-Pure Copper Lining to Normal-Conducting RF Cavities for an Electron-Positron Super B Factory factory, target, resonance, linac 1051
  • T. Abe, T. Kageyama
    KEK, Ibaraki
  • Z. Kabeya, T. Kawasumi
    MHI, Nagoya
  • T. Nakamura, K. Tsujimoto
    Asahi Kinzoku Co., Ltd., Gifu
  • K. Tajiri
    Churyo Engineering Co., Ltd., Nagoya
  We apply a new copper lining with a high purity and a high electric conductivity to normal-conducting RF cavities for an electron-positron super B factory, in which four-times more beam current is required to be stored than in the present KEK B factory (KEKB). The lining is produced first by electroplating in an acid copper sulfate bath without brightener nor other organic additives, where the current is periodically reversed (‘‘PR process''). Its electric conductivity is so high as to be comparable to that of the highest-class oxygen-free copper. Then the copper surface is electropolished to make it smoother. There are two differences between our application and the previous one to the accelerator components for J-Parc. The first one is the lining thickness; our target of 120um is much thinner. The second one is that we have no mechanical polishing on the electroplated surface before electropolishing. In this paper, results of the quantitative estimations of the quality factor on the electroplated pillbox test cavity are reported together with microscale investigations of the copper surfaces.  
TPPT008 New Design of Crab Cavity for SuperKEKB damping, impedance, polarization, feedback 1129
  • K. Akai, Y. Morita
    KEK, Ibaraki
  Crab-crossing scheme has been adopted as a baseline design for SuperKEKB, which is planned as an upgrade of KEKB. For the design of crab cavities for SuperKEKB, a very high beam current of 10A with a short bunch length of 3mm must be taken into account. Much heavier damping of any parasitic mode as well as smaller loss factor are required, compared with those of KEKB crab cavities. We propose new design of crab cavities for SuperKEKB. It has a high kick voltage, sufficiently low coupling impedance to any parasitic modes including the fundamental mode, and a considerably low loss factor. The new crab cavity meets the requirements for SuperKEKB.  
TPPT010 HOM Damping of ARES Cavity System for SuperKEKB klystron, dipole, damping, luminosity 1186
  • T. Kageyama, T. Abe, H. Sakai, Y. Takeuchi
    KEK, Ibaraki
  The ARES cavity scheme is a decisive edge for KEKB to stably accelerate high-current electron and positron beams. The RF structure is a coupled-cavity system where a HOM-damped accelerating cavity is coupled with a large cylindrical energy storage cavity via a coupling cavity between. The HOM-damped structure is designed to be smoothly embedded into the whole coupled-cavity scheme without any structural or electromagnetic incompatibility. Currently, the total HOM power dissipated in the RF absorbers per cavity is about 5 kW according to calorimetric measurements in the KEKB LER with a beam current of 1.6 A. On the other hand, for SuperKEKB aiming at luminosity frontiers over 1035 cm-2 s-1, the total HOM power per cavity is estimated about 100 kW for the LER with the design beam current of 9.4 A. In this article, a new HOM-damped structure of the ARES cavity system designed for the SuperKEKB LER is reported together with the recent activities and future plans for upgrading the HOM absorbers.  
TPPT011 R&D Status of C-Band Accelerating Section for SuperKEKB linac, positron, klystron, luminosity 1233
  • T. Kamitani, N. Delerue, M. Ikeda, K. Kakihara, S. Ohsawa, T. Oogoe, T. Sugimura, T. T. Takatomi, S. Yamaguchi, K. Yokoyama
    KEK, Ibaraki
  • Y. Hozumi
    GUAS/AS, Ibaraki
  For future energy upgrade of the KEKB injector linac, C-band accelerating section has been developed. First prototype 1-m long section has been installed in the linac and has achieved the accelerating field gradient of 42 MV/m. Developments of second prototype which has thicker coupler iris and third prototype which has smooth surface of the iris are in progress for less frequent breakdown. This paper reports on the recent R and D status of these C-band accelerating sections.  
TPPT012 High Power Testing of Input Couplers for SuperKEKB vacuum, electron, monitoring, positron 1294
  • H. Sakai, T. Abe, T. Kageyama, Y. Takeuchi
    KEK, Ibaraki
  In KEKB, 32 ARES cavities have been successfully operated to stably accelerate high-current electron and positron beams. Currently, each ARES cavity is fed with RF power (frequency = 509 MHz) of about 300 kW through an input coupler, which has a ceramic disk window at the coaxial line section following the doorknob transformer section with a capacitive iris at the rectangular waveguide entrance. For SuperKEKB, which is a challenging project to boost the luminosity frontier beyond 1035 cm-2 s-1, the power capability of the input coupler needs to be upgraded to more than 900 kW, while the design power capability for KEKB is 400 kW. Recently, we have constructed a new test stand in order to simulate the actual operating condition for the input coupler to drive the ARES cavity with the maximum beam loading of 9.4 A expected for the SuperKEKB LER. In this article, the key features of the new test stand are described together with the recent results of high-power tests.  
TPPT013 Effect of HOM Couplers on the Accelerating Mode in the Damped Cavity at the Photon Factory Storage Ring electromagnetic-fields, storage-ring, factory, photon 1339
  • T. Takahashi, M. Izawa, S. Sakanaka, K. Umemori
    KEK, Ibaraki
  • T. Koseki
    RIKEN/RARF/CC, Saitama
  Four damped cavities have been working very stably in the Photon Factory storage ring since 1997. The damped cavity has several trapped higher order modes (HOMs) with high Q values. Each frequency of these HOMs is detuned so as not to induce coupled-bunch instabilities. However, the frequency detuning method becomes less effective for a ring with a lower revolution frequency. Therefore, we have developed a HOM coupler that can reduce Q values of these trapped HOMs. The HOM coupler is a rod antenna type and located in the cylindrical wall of the cavity. Two or Three HOM couplers will be used for the cavity. The affect of these HOM couplers on the accelerating mode is investigated using MAFIA and the result is presented in this paper.  
TPPT015 Coupler Matching Techniques for C-Band Accelerating Section target, linac, resonance, simulation 1431
  • K. Yokoyama, M. Ikeda, K. Kakihara, T. Kamitani, S. Ohsawa, T. Sugimura, T. T. Takatomi
    KEK, Ibaraki
  Research and development of the c-band accelerating section has proceeded since 2002. This paper reports the development of the second prototype accelerating section. The coupler iris with a 4 mm thick is thicker than the first prototype because of preventing the rf breakdown at the iris edge. The coupler has a single port and the coupler cell is the same length as the waveguide(WR-187). The coupler cavity diameter and the coupling iris were optimized by using the iteration of the rf measurement which is the nordal shift method.  
TPPT019 Numerical Study of Coupling Slot Effects on Beam Dynamics in Industrial Accelerator Prototype quadrupole, simulation, electron, injection 1622
  • V.V. Tarnetsky, V. Auslender, I. Makarov, M.A. Tiunov
    BINP SB RAS, Novosibirsk
  Funding: The work is supported by ISTC grant #2550.

At Budker INP, the work is in progress on development of high-efficiency, high-power electron accelerator named ILU-12. The accelerator has a modular structure and consists of a chain of accelerating cavities connected by on-axis coupling cavities with coupling slots in the common walls (the coupling constant is about 0.08). Main parameters of the accelerator are: operating frequency of 176 MHz, electron energy of up to 5 MeV, average beam power of 300 kW. The paper presents results of 3D electromagnetic field numerical simulations for ILU-12 accelerating structure with recovery of quadrupole filed disturbance because of large coupling holes. The results show that accelerating cell geometry chosen eliminates coupling slot influence on the beam dynamics.

TPPT021 Characterization and Tuning of a Microwave Gun Cavity gun, cathode, electron, linac 1748
  • W.K. Lau, J. Chan, L.-H. Chang, C.W. Chen, H.Y. Chen, K.-T. Hsu, S.Y. Hsu, J.-Y. Hwang, Y.C. Wang, T.-T. Yang
    NSRRC, Hsinchu
  The SSRL rf gun cavity is electromagnetic structure with a half-cell at the cathode end and a full cell at the other end. Instead of coupling through beam pipe to produce the desired pi-mode for beam acceleration, these two cells are coupled through a frequency tunable side-coupled cell. Therefore, the strucuture is actually 3-cell cavity and the pi/2-mode will be used. This paper reports the characterization of these resonant modes at various side-coupled cell tuning conditions. And the behavior of this cavity will also be analytically examined.  
TPPT028 Design of a New Main Injector Cavity for the Fermilab Proton Driver Era proton, simulation, acceleration, impedance 2015
  • V. Wu, A.Z. Chen, Z. Qian, D. Wildman
    Fermilab, Batavia, Illinois
  Funding: Operated by Universities Research Association, Inc. for the U.S. Department of Energy under contract DE-AC02-76CH03000.

In the design report of the Fermilab Proton Driver [1],* the Main Injector (MI) needs to be upgraded to a 2 MW machine. For the Main Injector radiofrequency (rf) upgrade, R&D efforts are launched to design and build a new rf system. This paper presents the new cavity design study for the rf system. The cavity is simulated with the design code Mafia [2].**

**Proton Driver Study II, FERMILAB-TM-2169, May 2002, edited by G.W. Foster, W. Chou and E. Malamud. **Computer Simulation Technology, MAFIA 4, December 1996.

TPPT035 High-Power RF Testing of a 352-MHz Fast-Ferrite RF Cavity Tuner at the Advanced Photon Source resonance, photon, klystron, RF-structure 2407
  • D. Horan, E.E. Cherbak
    ANL, Argonne, Illinois
  Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under contract No. W-31-109-ENG-38.

A 352-MHz fast-ferrite rf cavity tuner, manufactured by Advanced Ferrite Technology, was high-power tested on a single-cell copper rf cavity at the Advanced Photon Source. These tests measured the fast-ferrite tuner performance in terms of power handling capability, tuning bandwidth, tuning speed, stability, and rf losses. The test system comprises a single-cell copper rf cavity fitted with two identical coupling loops, one for input rf power and the other for coupling the fast-ferrite tuner to the cavity fields. The fast-ferrite tuner rf circuit consists of a cavity coupling loop, a 6-1/8” EIA coaxial line system with directional couplers, and an adjustable 360° mechanical phase shifter in series with the fast-ferrite tuner. A bipolar DC bias supply, controlled by a low-level rf cavity tuning loop consisting of an rf phase detector and a PID amplifier, is used to provide a variable bias current to the tuner ferrite material to maintain the test cavity at resonance. Losses in the fast-ferrite tuner are calculated from cooling water calorimetry. Test data will be presented.

TPPT041 RF Tuning and Fabrication Status of the First Module for J-PARC ACS linac, pick-up, factory, vacuum 2684
  • H. Ao, T. Morishita, A. Ueno
    JAERI/LINAC, Ibaraki-ken
  • K. Hasegawa
    JAERI, Ibaraki-ken
  • M. Ikegami
    KEK, Ibaraki
  • V.V. Paramonov
    RAS/INR, Moscow
  • Y. Yamazaki
    JAERI/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  J-PARC Linac starts with 180-MeV SDTL temporary, and it is upgraded to 400-MeV with 21 ACS (Annular Coupled Structure) modules and two ACS bunchers and two debunchers. First buncher module is under fabrication, and second buncher and a few accelerating modules are also planed until FY2006. The first ACS module consists of two 5-cells ACS tanks and a 5-cells bridge cavity for the buncher module. Three RF tuners are installed to the bridge cavity for fine RF tuning. An operating frequency should be tuned to 972 MHz within the fine-tuning range before a brazing process in a factory. The tuning procedure has been studied with RF simulation analysis and cold-model measurements for ACS and bridge cells. This paper describes RF tuning results, fabrication status and related development items.  
TPPT049 Design and Cold Model Test of 500MHz Damped Cavity for ASP Storage Ring RF System impedance, damping, synchrotron, storage-ring 3076
  • J. Watanabe, K. Nakayama, K. S. Sato, H. Suzuki
    Toshiba, Yokohama
  • M. Izawa
    KEK, Ibaraki
  • A. Jackson, G. LeBlanc, K. Zingre
    ASP, Clayton, Victoria
  • T. Koseki
    RIKEN/RARF/CC, Saitama
  • N. Nakamura, H. Sakai, H. Takaki
    ISSP/SRL, Chiba
  TOSHIBA is constructing the storage ring RF system for the Australian Synchrotron Project(ASP). Two pairs of the 500MHz Higher Order Mode(HOM) damped cavities will be applied for this system. The cavities are modified KEK-PF type with silicon-carbide(SiC) microwave absorber and added three HOM anttenas for damping the longitudinal HOM impedance less than 20kOhm/GHz to meet requirement of ASP specification. The shunt impedance has been improved more than 5% in comparison with the original design by reducing the beam bore diameter without degrading HOM damping capability. The design of the cavity and the test results of an Al cold model are described.  
TPPT050 Rod-Loaded and PBG Multi-Beam Klystron Cavities klystron, dipole, lattice, cathode 3094
  • A. Smirnov, D. Yu
    DULY Research Inc., Rancho Palos Verdes, California
  Funding: Work supported by DOE SBIR Grant No. DE-FG02-03ER83845.

Performance of PBG-like structures was studied for multi-defect and single-defect metal cavities. Conceptual designs of a 6-beam, X-band, multi-beam klystron (MBK) demonstrate feasibility of high power generation with efficiency ~63% in a compact structure. Sheet-beam and annular-beam rod-loaded configurations were also investigated.

TPPT051 High Power Coupler for the TESLA Superstructure Cavities vacuum, electron, insertion, SNS 3141
  • Q.S. Shu, G. Cheng, J. T. Susta
    AMAC, Newport News, Virginia
  • S.J. Einarson
    CPI/BMD, Beverley, Massachusetts
  • T. Garvey
    LAL, Orsay
  • W.-D. Müller, D. Proch
    DESY, Hamburg
  • T.A. Treado
    CPI, Beverley, Massachusetts
  Funding: U.S. Department of Energy Grant No. DE-FG02-00ER86102.

More and more accelerators are built with superconducting cavities operating at cryogenic temperatures, and the probability of a ceramic window failure presents increasing problems because of the resulting contamination of the cavities surfaces and the resulting accelerating electric field degradation. A cost effective design and fabrication method for the TESLA cavities has been developed in the framework of a DOE STTR grant. This new design replaces the present TESLA cylindrical ceramic windows with two planar disc windows separated by a vacuum space and is optimized for RF input power, vacuum characteristics, and thermal properties. This novel coupler will reduce the costs of fabrication and improve the RF performance of the coupler, the vacuum between the two windows, and the cleaning procedure. Two couplers with this design have been fabricated and are presently being conditioned for testing at DESY, Germany, and LAL, France, on the RF high power testing stand and on a test cryomodule.

TPPT052 Cryogenic, Magnetic and RF Performance of the ISAC-II Medium Beta Cryomodule at TRIUMF alignment, acceleration, target, ion 3191
  • R.E. Laxdal, K. Fong, A.K. Mitra, T.C. Ries, I. Sekachev, G. Stanford, V. Zviagintsev
    TRIUMF, Vancouver
  The medium beta section of the ISAC-II Heavy Ion Accelerator consists of five cryomodules each containing four quarter wave resonators and one superconducting solenoid. The first cryomodule has been designed, assembled and cold tested at TRIUMF. The cryomodule vacuum space shares the cavity vacuum and contains a mu-metal shield, an LN2 cooled, copper thermal shield, plus the cold mass and support system. The bulk niobium cavities are fitted with an LN2 cooled coupling loop fed in series from the side thermal shield and a tuner plate coupled to an out-of-vacuum linear servo motor. All cavities have been locked at the ISAC-II frequency and gradient for extended periods. This paper will report the cryogenic and rf test results from the three cold tests. Of note are measurements of the magnetic field in the cryomodule and estimations of changes in the magnetic field during the test due to trapped flux in the solenoid and magnetization of the environment.  
TPPT058 First Tests of the Superconducting CH-Structure simulation, pick-up, resonance, proton 3414
  • H. Podlech, H. Deitinghoff, H. Klein, H. Liebermann, U. Ratzinger, A.C. Sauer, R. Tiede
    IAP, Frankfurt-am-Main
  Funding: GSI, BMBF contr. No. 06F134I, EU contr. No. EFDA/99-507ERB5005, CT990061 and RII3-CT-2003-506395.

The Crossbar-H-type CH-structure is a new H-mode drift tube-structure operating in the H11-mode. Due to its mechanical rigidity room temperature as well as superconducting cavities can be realized. The superconducting CH-structure has been developed at the IAP in Frankfurt, Germany. To prove the promising results obtained by simulations a 19-cell, 352 MHz (beta=0.1) prototype cavity has been designed and built. This is the first superconducting low energy multi-cell cavity. We present the first cold tests of the cavity which have been performed in the cryogenic laboratory in Frankfurt.

TPPT060 Design of a Multi-Cell, HOM Damped Superconducting Cavity for the Strong RF Focusing Experiment at DAFNE synchrotron, focusing, factory, feedback 3505
  • A. Gallo, D. Alesini, C. Biscari, R. Boni, F. Marcellini, M. Zobov
    INFN/LNF, Frascati (Roma)
  • C. Pagani
    DESY, Hamburg
  A strong RF focusing experiment to be performed at the DAFNE Phi-factory has been proposed to create and observe a bunch length modulation along the ring. The very large RF gradient required to reach the strong focusing regime can only be obtained by using a multi-cell superconducting cavity. Moreover, in order to demonstrate the feasibility of a high luminosity collider based on this principle, a total multibunch current of the order of 1A has to be stored under stable conditions in this regime. A 1.3 GHz 7-cells cavity has been designed for this purpose, based on the TESLA geometry with small modifications of the basic cell to comply with the DAFNE revolution frequency. The number of cells has been changed from 9 to 7 to reduce the number of the cavity HOMs, while the beam tubes have been enlarged to let most of the HOMs propagate and be damped by room-temperature ferrite rings. The modes of the first longitudinal band, which include the accelerating TM010_pi, do not propagate in the beam tubes and have been studied with special care to prevent the overlap with the bunch revolution harmonics and to cure the effects of coupling to the synchrotron tune sidebands.  
TPPT067 High Power Coupler Studies for the ERLP vacuum, linac, simulation, booster 3736
  • J.H.P. Rogers, C.D. Beard, P.A. Corlett
    CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire
  Funding: ASTeC, CCLRC Daresbury Laboratory.

Two Superconducting RF modules of the ELBE type have been ordered from Accel Instruments GmbH for use on the Energy Recovery Linac Prototype (ERLP) being built at Daresbury Laboratory. One structure is to be used as a booster module, with an energy gain of 8 MeV, and the other is to act as an energy recovery linac operating at electron beam energy of up to 35 MeV. High power couplers capable of handling up to 10 kW CW are required to provide successful operation of the ERLP. Once received from Accel four couplers including RF windows will be conditioned and tested at FZR Dresden; this paper describes the test procedure anticipated.

TPPT068 Optimized Shape of Cavity Cells for Apertures Smaller than in TESLA Geometry acceleration, linear-collider, collider, superconductivity 3748
  • V.D. Shemelin
    Cornell University, Ithaca, New York
  The accelerating rate (Eacc) of TESLA cavities can be increased for the same iris aperture if 1) some increase of Epk/Eacc is permitted so that the value of Hpk/Eacc can be lowered in comparison with the original cells (Epk and Hpk are maximal surface electric and magnetic fields); 2) shape of the cells is described by two elliptic arcs; 3) the reentrant cells obtained as a result of consecutive optimization with this geometry are treated as a possible version of cells in spite of some complications for fabrication. Not only the value of Hpk/Eacc can be improved but also values of cell-to-cell coupling and the geometry constants R/Q and G grow with the transition to the reentrant shapes. And these are not all benefits of this shape. The increased coupling prompts that the aperture of the original cell is big enough to be decreased without loss of field flatness in comparison with the original design. This decrease will lead to further increase of the Eacc for the same Hpk also as to improvement of others important parameters. Here, results of calculations for the original and for smaller apertures are presented and proposals for a better choice of TESLA cavity cells are derived.

Cornell University

TPPT071 Preliminary Results on the Simultaneous Excitation of the TM010 and TE011 Modes in a Single Cell Niobium Cavity focusing, emittance, superconducting-RF, pick-up 3844
  • G. Ciovati, P. Kneisel
    Jefferson Lab, Newport News, Virginia
  Funding: Work supported by the U.S. DOE Contract No DE-AC05-84ER40150.

Simultaneous excitation of both TM010 and TE011 modes has been proposed recently for superconducting photoinjector applications to take advantage of the accelerating field of the TM mode, combined with the focusing magnetic field of the TE mode. Simultaneous excitation of both modes has been carried out on a CEBAF single cell cavity. The cavity has two beam pipe side-ports for each mode for input and pick-up couplers. Coupling to the TE011 mode is done by magnetic loop couplers while for the TM010 mode coaxial antennas are used. The TE011 mode has the property of having zero surface electric field, surface magnetic field orthogonal to the one in the TM010 mode and concentrated in the iris/wall regions of the cavity. The presence of both modes in the cavity at the same time can also be used to investigate the so-called high field Q-drop in the TM010 mode. This paper will present some preliminary result on the test of the single cell cavity at 2K.

TPPT072 Effects of Electric and Magnetic Fields on the Performance of a Superconducting Cavity feedback, electron, vacuum, superconductivity 3874
  • G. Ciovati, P. Kneisel
    Jefferson Lab, Newport News, Virginia
  • J.S. Sekutowicz, W. Singer
    DESY, Hamburg
  Funding: Work supported by the U.S. DOE Contract No DE-AC05-84ER40150.

A special two-cell cavity was designed to obtain surface field distributions suitable for investigation of electric and magnetic field effects on cavity performance. The cavity design and preliminary results were presented in a previous contribution. The bulk niobium cavity was heat-treated in a vacuum furnace at 1250C to improve the thermal conductivity. Three seamless hydroformed NbCu cavities of the same design were fabricated to investigate the role of the electron beam welds located in high field areas.

TPPT073 Testing of the New Tuner Design for the CEBAF 12 GeV Upgrade SRF Cavities vacuum, SNS, radiation, higher-order-mode 3910
  • E. Daly, G.K. Davis, W.R. Hicks
    Jefferson Lab, Newport News, Virginia
  Funding: This manuscript has been authorized by SURA, Inc. under Contract No. DE-AC05-84ER-40150 with the U.S. Department of Energy.

The new tuner design for the 12 GeV Upgrade SRF cavities consists of a coarse mechanical tuner and a fine piezoelectric tuner. The mechanism provides a 30:1 mechanical advantage, is pre-loaded at room temperature and tunes the cavities in tension only. All of the components are located in the insulating vacuum space and attached to the helium vessel, including the motor, harmonic drive and piezoelectric actuators. The requirements and detailed design are presented. Measurements of range and resolution of the coarse tuner are presented and discussed.

TPPT074 Simulation Study of Electronic Damping of Microphonic Vibrations in Superconducting Cavities feedback, damping, simulation, resonance 3916
  • A.S. Hofler, J.R. Delayen
    Jefferson Lab, Newport News, Virginia
  Funding: This work was supported by the Department of Energy under contract DE-AC05-84ER-40150.

Electronic damping of microphonic vibrations in superconducting rf cavities involves an active modulation of the cavity field amplitude in order to induce ponderomotive forces that counteract the effect of ambient vibrations on the cavity frequency. In lightly beam loaded cavities, a reduction of the microphonics-induced frequency excursions leads directly to a reduction of the rf power required for phase and amplitude stabilization. Jefferson Lab is investigating such an electronic damping scheme that could be applied to the JLab 12 GeV upgrade, the RIA driver, and possibly to energy-recovering superconducting linacs. This paper discusses a model and presents simulation results for electronic damping of microphonic vibrations.

TPPT075 Influence of Ta Content in High Purity Niobium on Cavity Performance vacuum, electron, linac, SNS 3955
  • P. Kneisel, G. Ciovati, G. Myneni
    Jefferson Lab, Newport News, Virginia
  • T. Carneiro
    Reference Metals, Bridgeville, Pennsylvania
  • D. Proch, W. Singer, X. Singer
    DESY, Hamburg
  Funding: Work supported by the U.S. DOE Contract No DE-AC05-84ER40150.

In a previous paper* we have reported about initial tests of single cell 1500 MHz cavities made from high purity niobium with three different Ta contents of 160 ppm, ~600 ppm and ~1400 ppm. These cavities had been treated by buffered chemical polishing several times and 100 mm, 200 mm and 300 mm of material had been removed from the surfaces. This contribution reports about subsequent tests following post purification heat treatments with Ti and “in situ” baking. As a result, all cavities exhibited increased quench fields due to the improved thermal conductivity after the heat treatment. After the "in situ" baking at 120C for ~40 hrs the always present Q-drop at high fields disappeared and further improvements in accelerating gradient could be realized. Gradients as high as Eacc = 35 MV/m were achieved and there were no clear indications that the cavity performance was influenced by the Ta content in the material. A multi-cell cavity from the high Ta content material is being fabricated and results will be presented at this conference.

*P. Kneisel et al., Linac 2004.

TPPT076 Preliminary Results from Single Crystal and Very Large Crystal Niobium Cavities electron, superconductivity, vacuum, SNS 3991
  • P. Kneisel, G. Ciovati, G. Myneni
    Jefferson Lab, Newport News, Virginia
  • T. Carneiro
    Reference Metals, Bridgeville, Pennsylvania
  • J.S. Sekutowicz
    DESY, Hamburg
  Funding: Work supported by the U.S. DOE Contract No DE-AC05-84ER40150.

We have fabricated and tested several single cell cavities using material from very large grain niobium ingots. In one case the central grain exceeded 7" in diameter and this was used for a 2 GHz cavity. This activity had a dual purpose: to investigate the influence of grain boundaries on the often observed Q-drop at gradients Eacc > 20 MV/m in the absence of field emission, and to study the possibility of using ingot material for cavity fabrication without going through the expensive process of sheet fabrication. The sheets for these cavities were cut from the ingot by wire electro-discharge machining (EDM) and subsequently formed into half–cells by deep drawing. The following fabrication steps were standard: machining of weld recesses, electron beam welding of beam pipes onto the half cells and final equator weld to join both half cell/beam pipe subunits.The cavities showed heavy Q–disease caused by the EDM; after hydrogen degassing at 800C for 3 hrs in UHV the cavities showed promising results, however, a Q-drop above Eacc ~ 20 MV/m was still present. Testing of the cavities is still ongoing – so far accelerating gradients of 30 MV/m have been achieved.

TPPT077 Testing of HOM Coupler Designs on a Single Cell Niobium Cavity pick-up, superconductivity, vacuum, SNS 4012
  • P. Kneisel, G. Ciovati, G. Myneni, G. Wu
    Jefferson Lab, Newport News, Virginia
  • J.S. Sekutowicz
    DESY, Hamburg
  Funding: Work supported by the U.S. DOE Contract No DE-AC05-84ER40150.

Coaxial higher order mode (HOM) couplers were developed initially for PETRA cavitiesand subsequently for TESLA cavities. They were adopted later for SNS and Jlab upgrade cavities. The principle of operation is the rejection of the fundamental mode by the tunable filter configuration of the coupler and the transmission of the HOMs. It has been recognized recently that, in high average power applications, the pick-up probe of the HOM coupler must be superconducting in order to avoid substantial heat dissipation by the fundamental mode fields and deterioration of the cavity Q. In addition, the thermal conduction of existing rf feedthrough designs is only marginally sufficient to keep even the niobium probe tip superconducting in cw operation. We have equipped a single-cell niobium cavity with different HOM coupler configurations and tested the different designs by measuring Q vs Eacc behavior at 2 K for different feedthroughs and probe tipmaterials

TPPT081 Fabrication and Testing of the SRF Cavities for the CEBAF 12 GeV Upgrade Prototype Cryomodule Renascence damping, dipole, simulation, impedance 4081
  • C.E. Reece, E. Daly, S. Manning, R. Manus, S. Morgan, J.P. Ozelis, L. Turlington
    Jefferson Lab, Newport News, Virginia
  Funding: This manuscript has been authorized by SURA, Inc. under Contract No. DE-AC05-84ER-40150 with the U.S. Department of Energy.

Twelve seven-cell niobium cavities for the CEBAF 12 GeV upgrade prototype cryomodule Renascence have been fabricated at JLab and tested individually. This set includes four of the "Low Loss" (LL) design and eight of the "High Gradient" (HG) design. The fabrication strategy was an efficient mix of batch job-shop component machining and in-house EBW, chemistry, and final-step machining to meet mechanical tolerances. Process highlights will be presented. The cavities have been tested at 2.07 K, the intended CEBAF operating temperature. Performance exceeded the tentative design requirement of 19.2 MV/m cw with less than 31 W dynamic heat dissipation. These results, as well as the HOM damping performance will be presented.

TPPT090 Progress of 2-Cell Cavity Fabrication for Cornell ERL Injector emittance, vacuum, linac, superconductivity 4248
  • R.L. Geng, P. Barnes, M. Liepe, V. Medjidzade, H. Padamsee, A.K. Seaman, J. Sears, V.D. Shemelin, N. Sherwood
    Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
  Five 1300 MHz superconducting niobium cavities are to be used for the injector of Cornell ERL. The beam power requirement (100 kW each cavity) and the need to minimize emittance dilution due to the cavity structure have important impacts to the design and fabrication of these cavities. We plan to use Conflat stainless-steel flanges brazed to niobium tubes of niobium cavities. The first copper prototy cavity has been built and measured. Most parts for the first niobium cavity have been manufactured also. In this report, we will present the progress of the prototyping copper as well as niobium cavities.  
TPPT099 Prototype Superconducting Triple-Spoke Cavity for Beta = 0.63 linac, vacuum, superconductivity, electron 4338
  • K.W. Shepard, Z.A. Conway, J.D. Fuerst, M. Kedzie, M.P. Kelly
    ANL, Argonne, Illinois
  Funding: This work was supported by the U.S. Department of Energy under contract no. W-31109ENG_38.

This paper reports the development status of a 345 MHz, three-spoke-loaded, TEM-class superconducting cavity with a transit-time factor peaked at beta = v/c = 0.62. The cavity has a 4 cm diameter beam aperture, a transverse diameter of 45.8 cm, and an effective (interior) length of 85 cm. The cavity is the second of two three-spoke loaded cavities being developed for the RIA driver linac and other high-intensity ion linac applications. Construction of a prototype niobium cavity has been completed and the cavity has been chemically processed. Results of initial cold tests will be discussed

TPPT100 Superconducting Triple-Spoke Cavity for Beta = 0.5 Ions linac, ion, superconductivity, vacuum 4344
  • K.W. Shepard, Z.A. Conway, J.D. Fuerst, M. Kedzie, M.P. Kelly
    ANL, Argonne, Illinois
  Funding: This work was supported by the U.S. Department of Energy under contract no. W-31-109-ENG-38.

This paper reports results of cold tests of a 345 MHz, three-spoke-loaded TEM-class superconducting niobium cavity being developed for the RIA driver linac and for other high-intensity ion linac applications. The cavity has a beam aperture of 4 cm diameter, an interior length of 67 cm, and the transit-time factor peaks at beta = v/c = 0.5. In tests at 4.2 K, the cavity could be operated cw above the nominal design accelerating gradient of 9.3 MV/m, which corresponds to peak surface fields of 27.5 MV/m electric and 826 gauss magnetic. At this gradient the cavity provides more than 6 MV of accelerating potential. The cavity Q at 9.3 MV/m exceeded the nominal performance goal of 7.3E8. Operation at the design gradient at 4.2 K causes substantial boiling and two-phase flow in the liquid helium coolant, with the potential for microphonic-induced fluctuations of the rf frequency. Total microphonic eigenfrequency fluctuations were measured to be less than 1 Hz RMS in cw operation at 9.7 MV/m at 4.2 K.

TOPE003 Results from DR and Instrumentation Test Facilities damping, emittance, laser, quadrupole 305
  • J.U. Urakawa
    KEK, Ibaraki
  The KEK Accelerator Test Facility (ATF) is a 1.3GeV storage ring capable of producing ultra-low emittance electron beams and has a beam extraction line for ILC R&D. The ATF has proven to be an ideal place for researches with small, stable beams. 2x1010 single bunch and low current 20 bunch-train with 2.8nsec bunch spacing have been extracted to develop Nano-Cavity BPM’s, FONT, Nano Beam Orbit handling (FEATHER), Optical Diffraction Radiation (ODR) monitor, a precision multi-bunch laser-based beam profile monitor and polarized positron beam generation via backward-Compton scattering by the international collaboration. A set of three cavity BPM's is installed in the ATF extraction line on a set of extremely stiff supports. The KEK group installed another set of three BPM's, with their own support mechanism. The full set of 6 will prove extremely useful. In the DR (Damping Ring), we are researching the fast ion instability, micro-wave instability with four sets of damping wiggler and developing pulsed laser wire monitor, X-ray SR monitor, very fast kicker with about 1nsec rise/fall time to make ILC beam. I will report the recent results on above R&D’s.  
WOAA002 Progress and Plans for R&D and the Conceptual Design of the ILC Main Linacs linac, luminosity, klystron, collider 199
  • H. Hayano
    KEK, Ibaraki
  The International Linear Collider Main Linacs are based on superconducting accelerator structures operating at 1.3 GHz. The basis for this design has been developed and tested at DESY and R&D is progressing at many laboratories around the world including DESY, Orsay, KEK, FNAL, SLAC, Cornell, and JLAB. The status of the TESLA-style cavities and rf system will be reviewed and parameters for the ILC linac will be described. The role of the different linac test facilities will discussed and the critical items and R&D program to support a Conceptual Design and Technical Design will be outlined.  
WPAE045 Progress on RF Coupling Coil Module Design for the MICE Channel vacuum, emittance, factory, superconductivity 2869
  • D. Li, M.A. Green, S.P. Virostek, M.S. Zisman
    LBNL, Berkeley, California
  • W. Lau, A. E. White, S.Q. Yang
    OXFORDphysics, Oxford, Oxon
  Funding: This research work is supported by the US Department of Energy, under Contract No. DE-AC03-76SF00098.

We describe the progress on the design of the RF coupling coil (RFCC) module for the international Muon Ionization Cooling Experiment (MICE) at Rutherford Appleton Laboratory (RAL) in the UK. The MICE cooling channel design consists of two SFOFO cells that is similar to that of the US Study-II of a neutrino factory. The MICE RFCC module comprises a superconducting solenoid, mounted around four normal conducting 201.25-MHz RF cavities. Each cavity has a pair of thin curved beryllium windows to close the conventional open beam irises, so thatnecessitating separate power feeds for each of the four cavities has to be separately powered. The coil package that surrounds the RF cavities sits is mounted on a vacuum vessel. The RF vacuum is shared between the cavities and the vacuum vessel around the cavities such that. Therefore there is no differential pressure on the thin beryllium windows. This paper discusses the design progress of the RFCC module, the fabrication progress of a prototype 201.25-MHz cavity, and the superconducting coupling coil that will be cooled using a single, small 4 K cooler.

WPAP049 A High-Gradient CW RF Photo-Cathode Electron Gun for High Current Injectors cathode, gun, ion, emittance 3049
  • R.A. Rimmer
    Jefferson Lab, Newport News, Virginia
  Funding: This manuscript has been authored by SURA, Inc. under Contract No. DE-AC05-84ER-40150 with the U.S. Department of Energy.

The paper describes the analysis and preliminary design of a high-gradient photo-cathode RF gun optimized for high current CW operation. The gun cell shape is optimized to provide maximum acceleration for the newly emitted beam while minimizing wall losses in the structure. The design is intended for use in future high-current high-power CW FELs but the shape optimization for low wall losses may be advantageous for other applications such as XFELs or Linear Colliders using high peak power low duty factor guns where pulse heating is a limitation. The concept allows for DC bias on the photocathode in order to repel ions and improve cathode lifetime.

WPAT004 Coupling Methods for Superconducting CH-Cavities linac, simulation, vacuum 922
  • H. Liebermann, H. Podlech, U. Ratzinger, A.C. Sauer
    IAP, Frankfurt-am-Main
  Funding: GSI, BMBF contr. No. 06F134I, EU.

The cross-bar H-type (CH) cavity is a multi-gap drift tube structure based on the H-210 mode currently under development at IAP Frankfurt and in collaboration with GSI. Numerical simulations and rf model measurements showed that the CH-type cavity is an excellent candidate to realize Room Temperature and Superconducting multi-cell structures with a frequency range from about 150 MHz up to 800 MHz. For coupling into such a complex structure, we compare two coupling methods, one with capacitive and the other with inductive couplers. This paper will present detailed MicroWave Studio simulations and measurements for these different coupling methods for Room Temperature and Superconducting CH-Cavities. For coupling into a Superconducting CH-Cavity we prefer a capacitive coupler. We will also present an optimized Superconducting CH-Cavity for capacitive couplers.

WPAT005 A New Tuning Module for Resonant Coupling Structures linac, proton, klystron, booster 973
  • V.G. Vaccaro
    Naples University Federico II, Mathematical, Physical and Natural Sciences Faculty, Napoli
  • T. Clauser, A. Rainò, V. Variale
    INFN-Bari, Bari
  • A. D'Elia
    Naples University Federico II and INFN, Napoli
  • C. De Martinis, D. Giove
    INFN-Milano, Milano
  • M.R. Masullo
    INFN-Napoli, Napoli
  • M. Mauri
    INFN/LASA, Segrate (MI)
  In order to have efficient particle acceleration it is fundamental that the particles experience, in the accelerating gap, field amplitudes as uniform and as high as possible from gap to gap. Because of the unavoidable fabrication errors, an accelerating structure, when assembled, exhibits field values lower than the nominal ones and/or not uniform. All the usual procedures developed in order to adjust the parameter deviations responsible of the malfunction of these structures, are based on field amplitude measurements, by using the bead pull technique, which is a very invasive technique. In this paper the philosophy is reversed: it is assumed that all the information can be got by Sounding the Modes of the whole System (SMS) and correct the deviation of each frequency mode from its nominal value by means of an appropriate tuning of the cavities: resorting to a perturbative technique applied to a circuit model representing this kind of structures, it is possible to calculate the amount of tuning to give to the cavities. It will be shown that a very good equalization and maximization of the fields in the cavities can be achieved by using this technique.  
WPAT009 Status of the RF System for the 6.5 GeV Synchrotron Light Source PF-AR synchrotron, vacuum, synchrotron-radiation, radiation 1168
  • S. Sakanaka, K. Ebihara, S. Isagawa, M. Izawa, T. Kageyama, T. Kasuga, H. Nakanishi, M. Ono, H. Sakai, T. Takahashi, K. Umemori, S.I. Yoshimoto
    KEK, Ibaraki
  The Photon Factory Advanced Ring (PF-AR) is a 6.5-GeV synchrotron light source at KEK. An rf system comprises two 1.2-MW klystrons, six alternating-periodic-structure (APS) cavities, and other components. It supplies an rf voltage of about 15 MV with a beam current of 60 mA. The system has been working well, except for a trouble (frequent trips with beams) in one of the cavities. We found that the trips were triggered by an irradiation of synchrotron radiation to the cavity wall. In the summer of 2004, we reorganized the rf system, which allows us to install two insertion devices in a part of the rf sections. We replaced the troubled cavity at a time. We report both the operation status and the modification of the rf system.  
WPAT011 Application of TRL Calibration in Longitudinal Coupling Impedance Measurement Platform for BEPCII impedance, vacuum, insertion, feedback 1225
  • G. Huang, W.-H. Huang, S. Zheng
    Tsinghua University, Beijing
  • D.M. Zhou
    IHEP Beijing, Beijing
  Funding: Supported by NSFC 10375035.

TRL calibration is one of the standard calibration methods for RF measurement. Applying the TRL calibration method into the longitudinal coupling impedance platform makes it possible to eliminate the error matrix of the matching section and the RF connector. By using TRL calibration in the platform, the reference pipe of each device under test no longer required. The formula of the calibration is discussed in this paper and the software based on it is introduced.

WPAT018 The LEIR RF System impedance, ion, resonance, acceleration 1619
  • M.M. Paoluzzi, R. Garoby, M. Haase, P. Maesen, C. Rossi
    CERN, Geneva
  • C. Ohmori
    KEK, Ibaraki
  The lead-lead physics program of LHC relies on major changes of the CERN ion injector chain. In this framework, the conversion of LEAR (low energy antiproton ring) into the Low Energy Ion Ring (LEIR) is central and implies a new accelerating system covering a wide frequency range (0.35 - 5 MHz,) with a moderate voltage (4 kV). For this purpose two new wide-bandwidth cavities, loaded with Finemet® magnetic alloy cores, have been built in collaboration with KEK. Two 60 kW RF power amplifiers have also been built and the RF systems are now installed in the LEIR ring. They individually cover the whole frequency range without tuning and allow multi-harmonic operation. The design has been guided by need of safety margins, reliability and ease of maintenance. Some design aspects are presented as well as the performance achieved.  
WPAT028 High Power Ferrolelectric Switches at Centimeter and Millimeter Wavelengths resonance, extraction, vacuum, linear-collider 2056
  • V.P. Yakovlev, O.A. Nezhevenko
    Omega-P, Inc., New Haven, Connecticut
  • J.L. Hirshfield
    Yale University, Physics Department, New Haven, CT
  Funding: Research supported by the Department of Energy, Division of High Energy Physics.

High-power ultra-fast, electrically-controlled switches based on ferroelectric elements for accelerator applications in the centimeter and millimeter wavelength ranges are discussed. Examples of fast switches and phase shifters for pulse compression and power distribution systems at X– and Ka- band are presented. It is shown that such proposed switch designs based on modern ferroelectric materials allow the generation of pulsed power of hundreds of MW’s in both the centimeter and millimeter wave ranges.

WPAT036 A 700 MHZ, 1 MW CW RF System for a FEL 100mA RF Photoinjector klystron, power-supply, cathode, vacuum 2413
  • W. Roybal, D.C. Nguyen, W. Reass, D. Rees, P.J. Tallerico, P.A. Torrez
    LANL, Los Alamos, New Mexico
  Funding: U.S. Department of Energy.

This paper describes a 700 MHz, 1 Megawatt CW, high efficiency klystron RF system utilized for a Free Electron Laser (FEL) high-brightness electron photoinjector (PI). The E2V klystron is mod-anode tube that operates with a beam voltage of 95 kV. This tube, operating with a 65% efficiency, requires ~96 watts of input power to produce in excess of 1 MW of output power. This output drives the 3rd cell of a 2½-cell, p-mode PI cavity through a pair of planar waveguide windows. Coupling is via a ridge-loaded tapered waveguide section and "dog-bone" iris. This paper will present the design of the RF, RF transport, coupling, and monitoring/protection systems that are required to support CW operations of the 100 mA cesiated, semi-porous SiC photoinjector.

WPAT065 HLS RF System Improvement in NSRL Phase II Project vacuum, storage-ring, controls, electron 3653
  • K. Jin, Y. An, L. Feng, G. Huang, G. Liu, G. Wang, X. Zeng
    USTC/NSRL, Hefei, Anhui
  Hefei Light Source (HLS) is mainly composed of an 800 MeV electron storage ring and a 200 MeV Linac functioning as its injector. The RF system has been improved successfully for HLS storage-ring in NSRL Phase II Project. In this paper, the improvement of generator and power transmission system, the development of a new RF cavity and the perfection of RF controls are described in detail. The results and some analyses are presented.  
WPAT071 R&D Status of the 700 MHz, 1MW Klystron for PEFP klystron, cathode, gun, proton 3850
  • S.-H. Kim, B.H. Chung, K.-H. Chung, J.-S. Hong, J.-H. Jeon, sk. Ko, K. Lee, sj. Noh
    KAPRA, Cheorwon
  Funding: This study is supported by Proton Engineering Frontier Project at Korea Atomic Energy Research Institute.

KAPRA (Korea Accelerator and Plasma Research Association) are undertaking the first phase R&D for the 1 MW, CW 700 MHz klystron, which is targeting the future stage of the PEFP (Proton Engineering Frontier Project) accelerator at KAERI (Korea Atomic Energy Research Institute). The objectives of the first phase R&D are 1) setting up all infra structures/procedures for the design and fabrication, 2) developing a prototype klystron for proofs of principles, and 3) making a performance test of the prototype at a reduced duty. The second phase R&D is supposed to cover full power, CW operation and reliability issues. In this paper, a summary of R&D Status during the first phase for PEFP 1 MW, 700 MHz klystron is reported.

WPAT083 Steering and Focusing Effects in TESLA Cavity Due to High Order Mode and Input Couplers focusing, simulation, electromagnetic-fields, linac 4135
  • P. Piot
    Fermilab, Batavia, Illinois
  • M. Dohlus, K. Floettmann, M. Marx, S.G. Wipf
    DESY, Hamburg
  Funding: This work was supported by Universities Research Association Inc. under contract DE-AC02-76CH00300 with the U.S. Department of Energy, and by NICADD.

Many state-of-art electron accelerator proposals incorporate TESLA-type superconducting standing wave cavities. These cavities include input coupler (to feed the RF power into the cavity) and a pairs of high order mode couplers (HOM) to absorb the energy associated to HOM field excited as the bunch passes through the cavity. In the present paper we investigate, using numerical simulations, the impact of the input and HOM couplers on the beam dynamics. We show the overall effects are: a dipole kick (zeroth order) and normal and skew quadrupole-type focusing (first order). We present parametric studies of the strength of these effect for various operating gradients and incoming beam energies. We finally study the impact of this non-asymmetric field on the beam dynamics, taking as an example the low energy section of the European X-FEL injector.

WPAT084 A NEW DESIGN FOR A SUPER-CONDUCTING CAVITY INPUT COUPLER electron, vacuum, resonance, linac 4141
  • H. Matsumoto, S. Kazakov, K. Saito
    KEK, Ibaraki
  Funding: Toshiba Electron Tube & Devices Co. Ltd., Tochigi, Otawa, Japan.

An attractive structure using capacitive coupling has been found for the input coupler for the 45 MV/m versions of the International Linear Collider (ILC) project. The coupler supports an electrical field gradient of ~1 kV/m around the rf window ceramic with 500 kW through power, a VSWR of 1.1 and a frequency bandwidth of 460 MHz. No unwanted resonances were found in the rf window near the first and second harmonics of the operation frequency.

WPAT089 Test Bed for Superconducting Materials superconducting-RF, superconductivity, vacuum, resonance 4227
  • C.D. Nantista, V.A. Dolgashev, R. Siemann, S.G. Tantawi, J. Weisend
    SLAC, Menlo Park, California
  • I.E. Campisi
    ORNL, Oak Ridge, Tennessee
  Funding: Work supported by the U.S. Department of Energy under contract DE-AC03-76SF00515.

Superconducting rf cavities are increasingly used in accelerators. Gradient is a parameter of particular importance for the ILC. Much progress in gradient has been made over the past decade, overcoming problems of multipacting, field emission, and breakdown triggered by surface impurities. However, the quenching limit of the surface magnetic field for niobium remains a hard limitation on cavity fields sustainable with this technology. Further exploration of materials and preparation may offer a path to surpassing the current limit. For this purpose, we have designed a resonant test cavity. One wall of the cavity is formed by a flat sample of superconducting material; the rest of the cavity is copper or niobium. The H field on the sample wall is 74% higher than on any other surface. Multipacting is avoided by use of a mode with no surface electric field. The cavity will be resonated through a coupling iris with high-power rf at superconducting temperature until the sample wall quenches, as detected by a change in the quality factor. This experiment will allow us to measure critical magnetic fields up to well above that of niobium with minimal cost and effort.

WPAT093 A Three-Cell Superconducting Deflecting Cavity Design for the ALS at LBNL impedance, simulation, damping, dipole 4287
  • J. Shi, H. Chen, S. Zheng
    TUB, Beijing
  • J.M. Byrd, D. Li
    LBNL, Berkeley, California
  Deflecting RF cavities can be used to generate sub-pico-second x-rays by creating correlations between longitudinal and transverse phase space of electron bunches in radiation devices. Up to 2-MV defecting voltage at 1.5-GHz is required for 1.9-GeV electron beam at the Advanced Light Source (ALS) at LBNL. We present a conceptual design for a 1.5-GHz three-cell superconducting RF cavity and its coupler. The cavity geometry and deflecting shunt impedance are optimized using MAFIA code. The cavity impedance from lower and higher order modes (LOM and HOM) are computed. Possible schemes for damping most harmful LOM and HOM modes are discussed and simulated.  
WPAT095 Low-Loss Ferroelectric for Accelerator Application vacuum, resonance, linear-collider, collider 4305
  • A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio
  • A. Dedyk, S.F. Karmanenko
    Eltech University, St. Petersburg
  • E. Nenasheva
    Ceramics Ltd., St. Petersburg
  • V.P. Yakovlev
    Omega-P, Inc., New Haven, Connecticut
  Funding: U.S. Department of Energy.

Ferroelectric ceramics have an electric field-dependent dielectric permittivity that can be altered by applying a bias voltage. Ferroelectrics have unique intrinsic properties that makes them attractive for high-energy accelerator applications: very small response time of ~ 10-11 sec, considerably high breakdown limit of more than 100 kV/cm, good vacuum properties. Because of these features, bulk ferroelectrics may be used as active elements of tunable accelerator structures,* or in fast, electrically - controlled switches and phase shifters in pulse compressors or power distribution circuits of future linear colliders.** One of the most critical requirements for ferroelectric ceramic in these applications is the dielectric loss factor. In this paper, the new bulk ferroelectric ceramic is presented. The new composition shows a loss tangent of 4× 10-3 at 35 GHz. The ceramics have high tunability factor: the bias voltage of 50 kV/cm was enough to reduce the permittivity from 500 to 400. The material chemical compound, features of the technology process, and mechanical and electrical properties are discussed. The ways of BST ferrolectric parameters further improvement are discussed as well.

*A. Kanareykin, W. Gai, J. Power, E. Sheinman, and A. Altmark, AIP Conf. Proc. 647, Melville, N.Y., 2002, p. 565. **V.P. Yakovlev, O.A. Nezhevenko, J.L. Hirshfield, and A.D. Kanareykin, AIP Conf. Proc. 691, Melville, N.Y., 2003, p.187.

WOAC007 Beam-Based Nonlinear Optics Corrections in Colliders sextupole, octupole, multipole, resonance 601
  • F.C. Pilat, Y. Luo, N. Malitsky, V. Ptitsyn
    BNL, Upton, Long Island, New York
  Funding: Work performed under the auspices of the US Department of Energy

A method has been developed to measure and correct operationally the non-linear effects of the final focusing magnets in colliders, which gives access to the effects of multi-pole errors by applying closed orbit bumps, and analyzing the resulting tune and orbit shifts. This technique has been tested and used during 3 years of RHIC (the Relativistic Heavy Ion Collider at BNL) operations. I will discuss here the theoretical basis of the method, the experimental set-up, the correction results, the present understanding of the machine model, the potential and limitations of the method itself as compared with other non linear correction techniques.

WOAC008 Measuring and Understanding the Momentum Aperture in a Storage Ring resonance, scattering, synchrotron, storage-ring 645
  • C. Steier, D. Robin
    LBNL, Berkeley, California
  • W. Decking
    DESY, Hamburg
  • J. Laskar
    IMCCE, Paris
  • L.S.N. Nadolski
    SOLEIL, Gif-sur-Yvette
  • Y.K. Wu
    DU/FEL, Durham, North Carolina
  Funding: This work was supported by the U.S. Department of Energy, under Contract No. DE-AC03-76SF00098.

The momentum aperture of a storage ring is a very important parameter that strongly influences the performance, especially the beam lifetime. For the special case of synchrotron light sources with small emittance like the Advanced Light Source (ALS), the momentum aperture depends strongly on the transverse dynamics. It is very sensitive to machine conditions such as the tunes, chromaticities, lattice symmetry, and spurious coupling, since depending on those conditions the Touschek scattered particles explore different resonance regions in the phase space. In light sources, the momentum aperture usually also depends strongly on the vertical physical aperture. Applying frequency analysis techniques in simulations and for turn-by-turn orbit measurement data provides a very powerful tool to measure and understand limitations of the dynamic momentum aperture. The techniques presented are applicable to other light sources, as well as damping rings and many types of colliders.

WOPB002 Symmetries and Einstein vacuum, background, focusing, survey 217
  • M. Kobayashi
    KEK, Ibaraki
  After brief survey of influence of Einstein on current particle physics, fundamental symmetry between particles and antipaticles will be discussed. Existence of antiparticles is an important outcome of special relativity and quantum mechanics and disappearance of antiparticles from the present universe is one of the mysteries in Big Bang cosmology based on the Einstein equation. Remarkable progress has been made recently in the studies on the violation of symmetry between particles and antiparticles with the use of a new type of accelerator. Some of their achievements will be reported.  
ROAA001 DAFNE Operation and Plans for DAFNE2 luminosity, injection, factory, damping 112
  • M. Zobov, D. Alesini, G. Benedetti, M.E. Biagini, C. Biscari, R. Boni, M. Boscolo, A. Clozza, G.O. Delle Monache, G. Di Pirro, A. Drago, A. Gallo, A. Ghigo, S. Guiducci, M. Incurvati, C. Ligi, F. Marcellini, G. Mazzitelli, C. Milardi, L. Pellegrino, M.A. Preger, P. Raimondi, R. Ricci, C. Sanelli, M. Serio, F. Sgamma, B. Spataro, A. Stecchi, A. Stella, C. Vaccarezza, M. Vescovi
    INFN/LNF, Frascati (Roma)
  • J.D. Fox, D. Teytelman
    SLAC, Menlo Park, California
  • E. Levichev, P.A. Piminov, D.N. Shatilov
    BINP SB RAS, Novosibirsk
  The e+e- collider DAFNE, a 1.02 Gev c.m. Phi-factory, has exceeded 1.2 1032 cm-2s-1 peak luminosity with 7.5 pb-1 maximum daily integrated luminosity. At the present performance the physics program of the three main experiments DEAR, FINUDA and KLOE will be completed by mid 2007. In this paper we describe the steps which have led to the luminosity improvement and present proposals for the upgrade of the collider towards higher energy and/or luminosity. The main accelerator issues on which we are planning to rely for this purpose, such as lattices with negative momentum compaction, strong RF focusing, design of high field magnets and Linac upgrade, are discussed in detail.  
ROAA004 MICE: The International Muon Ionisation Cooling Experiment emittance, instrumentation, synchrotron, optics 398
  • P. Drumm
    CCLRC/RAL, Chilton, Didcot, Oxon
  Muon storage rings have been proposed for use as sources of intense high-energy neutrino beams and as the basis for multi-TeV lepton-antilepton colliding beam facilities. To optimise the performance of such facilities is likely to require the phase-space compression (cooling) of the muon beam prior to acceleration and storage. The short muon-lifetime makes it impossible to employ traditional techniques to cool the beam while maintaining the muon-beam intensity. Ionisation cooling, a process in which the muon beam is passed through a series of liquid hydrogen absorbers followed by accelerating RF-cavities, is the technique proposed to cool the muon beam. The international Muon Ionisation Cooling Experiment (MICE) collaboration has been formed to carry out a muon-cooling demonstration experiment, and its proposal to Rutherford Appleton Laboratory has been approved. The MICE cooling channel, the instrumentation and the implementation at the Rutherford Appleton Laboratory is described together with the predicted performance of the channel and the measurements that will be made.  
ROAC009 World Record Accelerating Gradient Achieved in a Superconducting Niobium RF Cavity superconductivity, vacuum, electron 653
  • R.L. Geng, A.K. Seaman, V.D. Shemelin
    Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
  • H. Padamsee
    Cornell University, Ithaca, New York
  Funding: Work supported by NSF.

On November 16, 2004, an accelerating gradient of 46 MV/m was achieved (CW) in a superconducting niobium cavity with an unloaded quality factor (Q0) over 1·1010 at a temperature of 1.9 K. This represents a world record gradient in a niobium RF resonator. At a reduced temperature of 1.5-1.6 K, an enhanced Q0 was measured, ranging from 7·1010 at 5 MV/m to 2·1010 at 45 MV/m. The 1.3 GHz single-cell cavity has a reduced ratio of Hpk/Eacc, ensured by a reentrant geometry. The maximum peak surface electric and magnetic field exceeded 100 MV/m and 1750 Oe respectively. A soft multipacting barrier (predicted by calculations) was observed near 25 MV/m gradient and was easily processed through. Field emission in the cavity was negligibly small, and the highest field was limited by thermal breakdown. The cavity was built, processed, and tested with LEPP facilities at Cornell University. New techniques included half-cell heat treatment with yttrium for post-purification to RRR = 500, and vertical electropolishing the finished cavity.

RPAE002 Coupling Correction of a Circularly Polarizing Undulator at the Advanced Photon Source quadrupole, octupole, simulation, undulator 805
  • L. Emery
    ANL, Argonne, Illinois
  Funding: This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38.

The electromagnetic Circularly Polarizing Undulator (CPU) installed at the Advanced Photon Source (APS) storage ring produces skew quadrupole field errors, which were initially corrected by a small skew quadrupole magnet at one end of the device. Because the storage ring is operated at 1% coupling or less, a correction not located at the source inside the CPU is insufficient, as we have confirmed in simulation. Adding a skew coil at the other end of the CPU allows us to make a complete correction of the coupling source in the undulator. Correction setpoints are determined by APS's general optimizing software with the vertical beam size of a x-ray pinhole image as a readback.

RPAE016 Smith-Purcell Radiation from a Charge Moving Above a Finite-Length Grating radiation, resonance, electron, diagnostics 1496
  • A.S. Kesar, S.E. Korbly, R.J. Temkin
    MIT/PSFC, Cambridge, Massachusetts
  • M. Hess
    IUCF, Bloomington, Indiana
  Funding: This work was supported by the Department of Energy, High Energy Physics, under contract DE-FG02-91ER40648.

Smith-Purcell radiation (SPR), emitted when a bunch is passing above a periodic structure, is characterized by a broadband radiation spectrum in which the wavelength depends on the observation angle. While various theoretical models agree on this dependence, a significant difference is introduced for the calculated radiated energy by the different approaches. We present two theoretical calculations of the SPR from a 2D bunch of relativistic electrons passing above a finite length grating. The first one uses the finite-difference time-domain approach and the second one uses an electric-field integral equation (EFIE) method. Good agreement is obtained between these two calculations. The results of these calculations are then compared with a formalism based on an infinite length grating in which a periodic boundary condition is rigorously applied. For gratings with less than approximately 50 periods, a significant error in the strength of the radiated field is introduced by the infinite grating approximation. This error disappears asymptotically as the number of periods increases. We are currently working on extending the EFIE model to the case of a three dimensional bunch moving above a finite-length grating.

RPAE062 Estimation of the Effective Magnet Misalignments of the ALS Storage Ring lattice, storage-ring, closed-orbit, quadrupole 3559
  • H. Nishimura, T. Scarvie
    LBNL, Berkeley, California
  Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC03-76SF00098

New storage ring lattices have traditionally been commissioned using a trial-and-error approach, where the number of turns circulated is slowly built up until enough beam is stored to correct the orbit. We have found that by combining the calculated response matrix of magnet misalignments from a linear model of a new lattice with the measured steering magnet response matrix used during normal operations, it is possible to make an educated guess for the steering magnet settings that will immediately allow beam circulation in the new lattice. “Effective” magnet misalignments are simply those that are sufficiently close to the real misalignments to make the first guess good enough to circulate beam; the relationship between effective and real magnet misalignments is also discussed in the paper. This predictive steering method makes the process of establishing enough circulating beam for SVD-based orbit correction in a new lattice very efficient.

RPAE073 Generating Picosecond X-Ray Pulses with Beam Manipulation in Synchrotron Light Sources synchrotron, photon, simulation, electron 3898
  • W. Guo, M. Borland, K.C. Harkay, V. Sajaev, B.X. Yang
    ANL, Argonne, Illinois
  Funding: Work supported by U. S. Department of Energy, Office of Basic Energy Sciences under Contract No. W-31-109-ENG-38.

The length of x-ray pulses generated by storage ring light sources is usually tens of picoseconds. For example, the value is 40 ps rms at the Advanced Photon Source (APS). Methods of x-ray pulse compression are of great interest at the APS. One possible method, per Zholents et al., is to tilt the electron bunch with deflecting rf cavities.* Alternately, we found that the electron bunch can develop a tilt after application of a vertical kick in the presence of nonzero chromaticity. After slicing, the x-ray pulse length is determined by the tilt angle and the vertical beam size. In principal, sub-picosecond pulses can be obtained at APS. To date we have observed 6 ps rms visible light pulses with a streak camera. Efforts are underway to attempt further compression of the x-ray pulse and to increase the brilliance. This method can be easily applied to any storage ring light sources to generate x-ray pulses up to two orders of magnitude shorter than the electron bunch length. In this paper, we will present the theory of bunch tilt, particularly the synchrobetatron coupling and decoherence beam dynamics, and the simulation and the experimental results will also be shown as verification.

*A. Zholents et al., NIM A 425, 385(1999).

RPAP027 Portable X-Band Linear Electron Accelerators for Radiographic Applications radiation, linac, electron, injection 1985
  • A.J. Saverskiy, H. Deruyter, M. Hernandez, A.V. Mishin, D. Skowbo
    AS&E, Billerica, Massachusetts
  The MINAC series portable linear electron accelerator systems designed and manufactured at American Science and Engineering, Inc. High Energy Systems Division (AS&E HESD) are discussed in this paper. Each system can be configured as either an X-ray or electron beam source. The powerful 4 MeV and 6 MeV linacs powered by a 1,5 MW magnetron permit operation in a dose rate range from 100 R/min at 80 cm to 600 R/min at 80 cm. Each MINAC is a self-contained source with radiation leakage outside of the X-ray head less than 0,1% of the maximum dose. Along with these systems a 1 MeV ultra compact MINAC has been successfully tested. The unit is available with radiation leakage less then 0.01% and permits producing X-ray beam in an energy range (1…2) MeV at a high output dose rate. Design and experimental parameters are presented. The common and system specific features are also discussed.  
RPAP037 Study of the Dynamics in a Linac Booster for Proton Therapy in the 30-62 MeV Energy Range linac, proton, cyclotron, booster 2494
  • V.G. Vaccaro
    Naples University Federico II and INFN, Napoli
  • T. Clauser, A. Rainò
    Bari University, Science Faculty, Bari
  • C. De Martinis, D. Giove, M. Mauri
    INFN/LASA, Segrate (MI)
  • S. Lanzone
    Naples University Federico II, Napoli
  • M.R. Masullo
    INFN-Napoli, Napoli
  • V. Variale
    INFN-Bari, Bari
  Funding: Istituto Nazionale di Fisica Nucleare (Naples, Milan and Bari).

Recent results in accelerator physics have shown the feasibility of a coupling scheme between a cyclotron and a linac for proton acceleration. Cyclotrons with energies up to 30 MeV, mainly devoted to radioisotopes production, are available in a large number of medical centres. These two evidences have suggested the idea to study and design a linac booster able to increase the initial proton energy up to the values required for the treatment of tumors, like the ocular ones. Among the challenges in such a project one of the main ones is related to meet the requirement of having sufficient mean current for therapy from a given injection current coming from the cyclotron. In this paper we will review the rationale of the project in order to optimize the transmittance and to minimize the duty-cycle. In this frame we will discuss the basic design of a compact 3GHz linac with a new approach to the cavities used in a SCL (Side Coupled Linac) structure.

RPAT033 Beta Function Measurement in the Tevatron Using Quadrupole Gradient Modulation quadrupole, lattice, emittance, dipole 2272
  • A. Jansson, P. Lebrun, J.T. Volk
    Fermilab, Batavia, Illinois
  Funding: Work supported by the U.S. Department of Energy.

Early in Run2, there was an effort to compare the different emittance measurements in the Tevatron (flying wires and synchtotron light) and understand the origin of the observed differences. To measure the beta function at a few key locations near the instruments, air-core quadrupoles were installed. By modulating the gradient of these magents and measuring the effect on the tune, the lattice parameters can be extracted. Initially, the results seem to disagree with with other methods. At the time, the lattice was strongly coupled due to a skew component in the main dipoles, caused by sagging of the cryostat. After a large fraction of the superconducting magnets were shimmed to remove a strong skew quadrupole component, the results now agree with expectations, confirming that the beta function is not the major error source of discrepancy in the emittance measurement.

RPAT074 PEP-II Transverse Feedback Electronics Upgrade feedback, diagnostics, pick-up, kicker 3928
  • J.M. Weber, M.J. Chin, L.R. Doolittle
    LBNL, Berkeley, California
  • R. Akre
    SLAC, Menlo Park, California
  Funding: Supported by the U.S. Department of Energy under contract No. DE-AC03-76SF00098 (LBNL) and DE-AC03-76SF00515 (SLAC).

The PEP-II B Factory at the Stanford Linear Accelerator Center (SLAC) requires an upgrade of the transverse feedback system electronics. The new electronics require 12-bit resolution and a minimum sampling rate of 238 Msps. A Field Programmable Gate Array (FPGA) is used to implement the feedback algorithm. The FPGA also contains an embedded PowerPC 405 (PPC-405) processor to run control system interface software for data retrieval, diagnostics, and system monitoring. The design of this system is based on the Xilinx® ML300 Development Platform, a circuit board set containing an FPGA with an embedded processor, a large memory bank, and other peripherals. This paper discusses the design of a digital feedback system based on an FPGA with an embedded processor. Discussion will include specifications, component selection, and integration with the ML300 design.

RPAT080 The SPEAR 3 Diagnostic Beamlines radiation, synchrotron, emittance, optics 4057
  • W.J. Corbett, C. Limborg-Deprey, W.Y. Mok, A. Ringwall
    SLAC, Menlo Park, California
  Funding: Work supported in part by DOE contract DE-AC03-76SF00515 and Office of Basic Energy Sciences, Division of Chemical Sciences.

SPEAR 3 is equipped with an x-ray pinhole camera and a visible/UV beam line to evaluate electron beam properties. The pinhole camera has a 30 x 25 micron Ta aperture and 60% image demagnification on a phosphor screen. The image is captured by a National Instruments frame-grabber on a remote computer with a parallel video signal for control room monitoring. The visible/UV beam line features a horizontal ± 0.3 mrad ‘cold finger’ to remove the x-ray core of the beam. The remaining visible/UV light is deflected 18 degrees onto an optical bench where it is focused via refractive Cassegrain optics. The beam is then split into parallel optics for gated- and streak camera measurements. This paper describes the experimental set up and preliminary measurements obtained with both systems.

RPAT096 High-Precision Resonant Cavity Beam Position, Emittance and Third-Moment Monitors quadrupole, dipole, impedance, sextupole 4311
  • N. Barov, J.S. Kim, A.W. Weidemann
    Far-Tech, Inc., San Diego, California
  • R.H. Miller, C.D. Nantista
    SLAC, Menlo Park, California
  Funding: Work supported by the U.S. Dept. of Energy.

Linear colliders and FEL facilities need fast, nondestructive beam position and profile monitors to facilitate machine tune-up, and for use with feedback control. FAR-TECH, Inc. is developing a resonant cavity diagnostic to simultaneously measure the dipole, quadrupole and sextupole moments of the beam distribution. Measurements of dipole and quadrupole moments at multiple locations yield information about beam orbit and emittance. The sextupole moment can reveal information about beam asymmetry which is useful in diagnosing beam tail deflections caused by short range dipole wakefields. In addition to the resonance enhancement of a single-cell cavity, use of a multi-cell standign-wave structure further enhances signal strength and improves the resolution of the device. An estimated rms beam size resolution is sub micro-meters and beam position is sub nano-meter.

ROAB002 Advances of Transmission Line Kicker Magnets kicker, injection, impedance, extraction 235
  • L. Ducimetière
    CERN, Geneva
  Fast pulsed magnets or kickers are widely used in circular accelerators for injection, fast extraction and beam excitation. As from the early 60’s transmission line type kicker magnets have been employed to produce rectangular field pulses with good rise time. Over some 40 years this technology has evolved with the rising requirements. Whilst the necessary kick strength has increased with the particle beam energies the strive for efficiency has pushed developments towards lower impedance systems and/or short circuited magnets. The flat top ripple is constrained by the maximally tolerable beam oscillation. The beam intensity can impose a screening of the magnet yoke. The most advanced features implemented in recent transmission line kicker magnets are reviewed and illustrated with examples from different laboratories. Ongoing and potential future developments are briefly discussed.  
ROAB005 Helical Pulseline Structures for Ion Acceleration ion, acceleration, vacuum, induction 440
  • R.J. Briggs
    SAIC, Alamo, California
  • L. R. Reginato, W. Waldron
    LBNL, Berkeley, California
  Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Berkeley National Laboratory, Contract DE-AC03-76SF00098.

The basic concept of the "Pulseline Ion Accelerator" involves launching a ramped high voltage pulse on a broad band traveling wave (slow-wave) structure. An applied voltage pulse at the input end with a segment rising linearly in time becomes a linear voltage ramp in space that propagates down the line, corresponding to a (moving) region of constant axial accelerating electric field. The ions can "surf" on this traveling wave, experiencing a total energy gain that can greatly exceed the peak of the applied voltage. The applied voltage waveform can also be shaped to longitudinally confine the beam against its own space charge forces, and (in the final stage) to impart an inward compression to the beam for neutralized drift compression in heavy ion HEDP applications. In the first stages of a heavy ion accelerator, the pulseline velocity needs to be the order of 1% of the speed of light and the line must be sufficiently non-dispersive for the broad band voltage pulse propagating down the line to have minimal distortion. Experimental characterization of the dispersion and pulse propagation at low voltage on several helix models will be presented, and compared with theoretical predictions.*

*Caporaso, et al, "Dispersion Analysis of the Pulseline Accelerator," this conference.

ROAB009 NuMI Proton Kicker Extraction System kicker, extraction, injection, magnet-design 692
  • C.C. Jensen, G. E. Krafczyk
    Fermilab, Batavia, Illinois
  Funding: Fermilab is operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the U.S. Department of Energy.

This system extracts up to 9.6 us of 120 GeV beam every 1.87 seconds for the NuMI beamline neutrino experiments. A pulse forming network consisting of two continuous wound coils and 68 capacitors was designed and built to drive three kicker magnets. The field stability requirement is better than ± 1% with a field rise time of 1.6 us. New kicker magnets were built based on the successful traveling wave magnets built for the Main Injector. Two of these magnets, which have a propagation time of 550 ns, are in series making the risetime of the pulser a serious constraint. A forced cooling system using Fluorinert® was designed for the magnet termination resistors to maintain the field flatness and amplitude stability. The system has been commissioned and early results will be presented.

RPPE007 High Precision Temperature Control and Analysis of RF Deionized Cooling Water System synchrotron, synchrotron-radiation, radiation, instrumentation 1057
  • Z.-D. Tsai, J.-C. Chang, C.-Y. Liu
    NSRRC, Hsinchu
  • J.-R. Chen
    NTHU, Hsinchu
  Previously, the Taiwan Light Source (TLS) has proven the good beam quality mainly depends on the utility system stability. A serial of efforts were devoted to these studies. Further, a high precision temperature control of the RF deionized cooling water system will be achieved to meet the more critical stability requirement. The paper investigates the mixing mechanism through thermal and flow analysis and verifies the practical influences. A flow mixing mechanism and control philosophy is studied and processed to optimize temperature variation which has been reduced from ±0.1? to ±0.01?. Also, the improvement of correlation between RF performance and water cooling stability will be presented.  
RPPE008 Water Induced Vibration in the NSRRC quadrupole, damping, storage-ring, vacuum 1102
  • D.-J. Wang, H.C. Ho, Z.-D. Tsai, J. Wang
    NSRRC, Hsinchu
  Water flow related vibrations were found on the spectrum of electron beam position monitor in the NSRRC. They were associated with the vibrations of quadrupole magnets. One major vibration source was from a pump in the cooling water system. Most amount of vibration coupled through water pipe and water flow and propagated to the magnets. A small water flow station was set up to study the effect about coupling, propagating and excitation. Some damping schemes tested in the ring to improve the vibration are also included..  
RPPE058 Successful RF and Cryogenic Tests of the SOLEIL Cryomodule electron, insertion, insertion-device, synchrotron 3438
  • P. Marchand, M. Louvet, M. Louvet-Monsanglant, K. Tavakoli, C. Thomas-Madec
    SOLEIL, Gif-sur-Yvette
  • L. Arnaudon, O. Brunner, R. Losito, P. Maesen, E. Montesinos, G. Pechaud, M.P. Prax
    CERN, Geneva
  • P. Bosland, P. Bredy, S. Chel, G. Devanz
    CEA/DSM/DAPNIA, Gif-sur-Yvette
  In the Storage Ring (SR) of the Synchrotron SOLEIL light source, two cryomodules will provide the maximum power of 600 kW required at the nominal energy of 2.75 GeV with the full beam current of 500 mA and all the insertion devices. A cryomodule prototype, housing two 352 MHz superconducting single-cell cavities with strong damping of the Higher Order Modes has been built and successfully tested in the ESRF. Even though the achieved performance (3 MV and 380 kW) does meet the SOLEIL requirement for the first year of operation, it was decided to upgrade the cryomodule prototype before its implementation in the SR. Modifications of the internal cryogenic system as well as the input power and dipolar HOM couplers required complete disassembling, reassembling and testing of the cryomodule, which were carried out at CERN. This refurbishment program, which was achieved in the framework of a collaboration between SOLEIL, CEA and CERN, is reported in this paper. A second cryomodule, similar to the modified prototype, is under manufacturing and will be implemented in the SR by the end of 2006.  
RPPE059 Measurements of Epsilon and Mu of Lossy Materials for the Cryogenic HOM Load damping, resonance, insertion, superconductivity 3462
  • V.D. Shemelin, H. Padamsee
    Cornell University, Ithaca, New York
  • M. Liepe
    Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
  Funding: Supported by Cornell University

In high current storage rings with superconducting cavities strong broadband HOM damping has been achieved by using beam-pipe ferrite loads, located at room temperature. Adopting the same damping concept for the ERL with RF absorbers between the cavities in a cavity string will require operating the absorbers at a temperature of about 80 K. This temperature is high enough to intercept HOM power with good cryogenic efficiency, and is low enough to simplify the thermal transition to the cavities at 2 K. However the electromagetic properties of possible absorber materials were not well known at cryogenic temperatures. We performed a measurement program at Cornell to find possible absorbers for HOMs in the ERL. Measurements were done for 10 different materials in the range from 1 to 40 GHz.

RPPP006 The PITZ Booster Cavity–A Prototype for the ILC Positron Injector Cavities booster, positron, linac, emittance 1030
  • V.V. Paramonov, L.V. Kravchuk
    RAS/INR, Moscow
  • K. Floettmann
    DESY, Hamburg
  • M. Krasilnikov, F. Stephan
    DESY Zeuthen, Zeuthen
  A critical issue of the design of the Positron Pre-Accelerator (PPA) for the future International Linear Collider (ILC) is the operational reliability of the normal conducting, high accelerating gradient L-band cavities. Now a booster cavity, intended for increasing the beam energy at the Photo Injector Test Facility in Zeuthen (PITZ), and developed by a joined INR-DESY group, is under construction at DESY, Hamburg. With the PITZ requirements (accelerating gradient up to 14 MV/m, rf pulse length up to 900 mks, repetition rate up to 5 Hz) this cavity, which is based on the Cut Disk Structure (CDS), is a full scale, high rf power prototype of the cavities proposed for the PPA. The booster cavity operation will allow us to confirm the main design ideas for the high gradient PPA cavities. A detailed technical study was performed during the booster cavity design, resulting in some modifications for the PPA cavities, which are described in this paper. We also propose a program of rf experiments with the PITZ booster cavity for further improvements of the PPA structures.  
RPPP042 Emittance Dilution Due to Dipole Mode Rotation and Coupling in the Main Linacs of the ILC emittance, linac, simulation, dipole 2723
  • R.M. Jones, R.H. Miller
    SLAC, Menlo Park, California
  Funding: This work is supported by Department of Energy grant number DE-AC02-76SF00515.

The progress of multiple bunches of charged particles down the main L-band linacs of the ILC (International Linear Collider) can be disrupted by wakefields. These wakefields correspond to the electromagnetic fields excited in the accelerating cavities and have both long-range and short-range components. Here we investigate the impact of the long-range wakefields on the trailing bunches caused by the leading bunches. In general, the dipole mode degeneracy will be removed both because of manufacturing errors and because the higher order mode couplers are dipole asymmetric and lie neither in the horizontal nor vertical plane. This creates 2 dipole eigenmodes which are rotated with respect to the horizontal and vertical axes and which may have slightly different frequencies. These eigenmodes can couple the horizontal and vertical dipole excitations. We simulate the progress of the ILC beam down the collider under the influence of these wakefields. In particular, we investigate the consequences on the final emittance dilution of the beam of coupling of the horizontal to the vertical motion of the beam.

RPPP044 Studies of Room Temperature Accelerator Structures for the ILC Positron Source positron, acceleration, impedance, linear-collider 2827
  • J.W. Wang, C. Adolphsen, V. Bharadwaj, G.B. Bowden, V.A. Dolgashev, R.M. Jones, E.N. Jongewaard, J.R. Lewandowski, Z. Li, R.H. Miller
    SLAC, Menlo Park, California
  Funding: Work supported by U.S. Department of Energy, contract DE-AC02-76F00515.

There are many challenges in the design of the normal-conducting portion of ILC positron injector system such as achieving adequate cooling with the high rf and particle loss heating, and sustaining high accelerator gradients during millisecond-long pulses in a strong magnetic field. The proposed design for the positron injector contains both standing-wave and traveling-wave L-band accelerator structures for high RF efficiency, low cost and ease of fabrication. This paper presents results from studies of particle energy deposition for both undulator based and conventional positron sources, cooling system design, accelerator structure optimization, RF pulse heating, cavity frequency stabilization, and RF feed system design.

RPPT014 Design and Measurements of an X-Band Accelerating Cavity for SPARC resonance, linac, scattering, higher-order-mode 1407
  • D. Alesini, M. Ferrario, B. Spataro
    INFN/LNF, Frascati (Roma)
  • A. Bacci
    INFN/LASA, Segrate (MI)
  • A. Falone, M.  Migliorati, A. Mostacci, F. Palpini, L. Palumbo
    Rome University La Sapienza, Roma
  The paper presents the design of an X-band accelerating section for linearizing the longitudinal phase space in the Frascati Linac Coherent Light Source (SPARC). The structure, operating on the pi standing wave mode, is a 9 cells structure feeded by a central waveguide coupler and has been designed to obtain a 5 MV accelerating voltage. The 2D profile has been obtained using the e.m. codes SUPERFISH and OSCARD2D while the coupler has been designed using HFSS. Bead-pull measurement made on a copper prototype are illustrated and compared with the numerical results. Mechanical details of the realized prototype and RF properties of the structure as a function of the assembly characteristics are also discussed.  
FPAE043 Transverse Tuning Scheme for J-PARC Linac linac, quadrupole, monitoring, emittance 2750
  • M. Ikegami, Z. Igarashi, S. Lee
    KEK, Ibaraki
  • H. Akikawa, K. Hasegawa, Y. Kondo, T. Ohkawa
    JAERI, Ibaraki-ken
  • H. Ao, S. Sato, T. Tomisawa, A. Ueno
    JAERI/LINAC, Ibaraki-ken
  In a high-intensity linac, precise transverse matching is essential for beam halo mitigation. In this paper, we present the supposed transverse tuning scheme for J-PARC linac and the planned beam diagnostic layout for it. Relevantly, we briefly touch upon the tuning scenario for the arc section and the transverse halo collimator system which are located between the linac and the succeeding ring.  
FPAE044 Test Results of the PEFP 3MeV RFQ Upgrade rfq, proton, klystron, dipole 2842
  • Y.-S. Cho, S.-H. Han, J.-H. Jang, H.-S. Kim, Y.-H. Kim, H.-J. Kwon, M.-Y. Park, K.T. Seol
    KAERI, Daejon
  Funding: This work is supported by the 21C Frontier R&D program in the Ministry of Science and Technology of the Korean government.

A 3MeV RFQ upgrade for 100MeV proton accelerator has been fabricated at PEFP (Proton Engineering Frontier Project). The tuning of the cavity was carried out before and after the brazing to meet the condition that the quadrupole field profile is within 1% of design value and dipole component is less than 1% of quadrupole one. The ancillary system such as high power RF including klystron power supply and cooling system were already tested up to operating level. Therefore, the main issues of the tests were cavity conditioning up to full power level and low duty beam test. After the completion of the beam test of RFQ itself, the 20MeV DTL which has been tested independently will be carried out. In this paper, the test results of the PEFP 3MeV RFQ upgrade including high power conditioning and low duty beam acceleration are presented.

FPAE048 Fabrication of the PEFP 3MeV RFQ Upgrade rfq, proton, vacuum, quadrupole 3010
  • H.-J. Kwon, Y.-S. Cho, J.-H. Jang, H.-S. Kim, Y.-H. Kim
    KAERI, Daejon
  Funding: This work is supported by the 21C Frontier R&D program in the Ministry of Science and Technology of the Korean government.

A 100MeV proton accelerator has been developed at PEFP (Proton Engineering Frontier Project) as a 21C Frontier Project. The goal of the first stage of the project is to develop a 20MeV accelerator. The 20MeV accelerator consists of ion source, LEBT, 3MeV RFQ and 20MeV DTL. The 3MeV RFQ was already installed and being tested. During preliminary test, some problems, such as the resonant frequency and field profile tuning, sharp edge in the vane end, inadequate RF seals have been found out. Therefore, it was decided to fabricate another RFQ. The RFQ upgrade includes some characteristics such as constant voltage profile, adoption of transition cell which are different from present one. In this paper, the fabrication of the PEFP 3MeV RFQ upgrade are presented.

FPAP020 Close-Coupling R-Matrix Approach to Simulating Ion-Atom Collisions for Accelerator Applications electron, target, background, simulation 1685
  • P. Stoltz, A. Prideaux
    Tech-X, Boulder, Colorado
  Funding: Funded by DOE under grant # DE-FG02-02ER83553.

We have implemented an R-matrix close coupling approach to calculate capture, ionization, stripping and excitation cross-sections for 0.5 to 8.0 MeV K+ incident on Ar. This is relevant to the High Current Experiment at Lawrence Berkley National Laboratory. These cross sections are used to model accelerator particle dynamics where background gasses can interfere with beam quality. This code is a semi-classical approach that uses quantum mechanics to describe the particle interactions and uses classical mechanics to describe the nuclei trajectories. We compare a hydrogenic approximation for K+ with a pseudo-potential approach. Further we are developing a variational approach to quickly determine the best pseudo-potential parameters. Since many R-Matrix computationalists use this pseudo-potential approach, this approach will be useful for helping generate cross sections for any collision system.

FPAP029 Nonlinear Delta-f Particle Simulations of Collective Effects in High-Intensity Bunched Beams simulation, space-charge, collective-effects, focusing 2107
  • H. Qin, R.C. Davidson, S.R. Hudson, E. Startsev
    PPPL, Princeton, New Jersey
  Funding: Research supported by the U.S. Department of Energy.

The collective effects in high-intensity 3D bunched beams are described self-consistently by the nonlinear Vlasov-Maxwell equations.* The nonlinear delta-f method,** a particle simulation method for solving the nonlinear Vlasov-Maxwell equations, is being used to study the collective effects in high-intensity 3D bunched beams. The delta-f method, as a nonlinear perturbative scheme, splits the distribution function into equilibrium and perturbed parts. The perturbed distribution function is represented as a weighted summation over discrete particles, where the particle orbits are advanced by equations of motion in the focusing field and self-consistent fields, and the particle weights are advanced by the coupling between the perturbed fields and the zero-order distribution function. The nonlinear delta-f method exhibits minimal noise and accuracy problems in comparison with standard particle-in-cell simulations. A self-consistent 3D kinetic equilibrium is first established for high intensity bunched beams. Then, the collective excitations of the equilibrium are systematically investigated using the nonlinear delta-f method implemented in the Beam Equilibrium Stability and Transport (BEST) code.

*R.C. Davidson and H. Qin, Physics of Intense Charged Particle Beams in High Energy Accelerators (World Scientific, 2001). **H. Qin, Physics of Plasmas 10, 2078 (2003).

FPAT007 The Fermilab Lattice Information Repository lattice, optics, antiproton, collider 1066
  • J.-F. Ostiguy, M. Kriss, M. McCusker-Whiting, L. Michelotti
    Fermilab, Batavia, Illinois
  Funding: Fermilab is operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the United States Department of Energy.

Fermilab is a large accelerator complex with six rings and sixteen transfer beamlines operating in various modes and configurations, subject to modifications, improvements and occasional major redesign. Over the years, it became increasingly obvious that a centralized lattice repository with the ability to track revisions would be of great value. To that end, we evaluated potentially suitable revision systems, either freely available or commercial, and decided that expecting infrequent users to become fully conversant with complex revision system software was neither realistic nor practical. In this paper, we discuss technical aspects of the recently introduced FNAL Accelerator Division's Lattice Repository, whose fully web-based interface hides the complexity of Subversion, a comprehensive open source revision system. In particular we emphasize how the architecture of Subversion was a key ingredient in the technical success of the repository's implementation.

FPAT011 Fast Automated Decoupling at RHIC quadrupole, monitoring, resonance, instrumentation 1254
  • J. Beebe-Wang
    BNL, Upton, Long Island, New York
  Funding: Work performed under the auspices of the U.S. DOE.

Coupling correction is essential for the operational performance of RHIC. The independence of the transverse degrees of freedom makes diagnostics and tune control easier, and it is advantageous to operate an accelerator close to the coupling resonance to minimize nearby nonlinear sidebands. An automated decoupling application has been developed at RHIC for coupling correction during routine operations. The application decouples RHIC globally by minimizing the tune separation through finding the optimal settings of two orthogonal skew quadrupole families. The program provides options of automatic, semi-automatic and manual decoupling operations. It accesses tune information from all RHIC tune measurement systems: the PLL (Phase Lock Loop), the high frequency Schottky system, and the tune meter. It also supplies tune and skew quadrupole scans, finding the minimum tune separation, display the real time results and interface with the RHIC control system. We summarize the capabilities of the decoupling application, and discuss the operational protections incorporated in the program. We also report the decoupling performances with the application during the RHIC 2005 run.

FPAT029 High Voltage Operation of Helical Pulseline Structures for Ion Acceleration ion, impedance, acceleration, vacuum 2092
  • W. Waldron, L. R. Reginato
    LBNL, Berkeley, California
  • R.J. Briggs
    SAIC, Alamo, California
  Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Berkeley National Laboratory, Contract # DE-AC03-76SF00098.

The basic concept for the acceleration of heavy ions using a helical pulseline requires the launching of a high voltage traveling wave with a waveform determined by the beam transport physics in order to maintain stability and acceleration.* This waveform is applied to the front of the helix, creating over the region of the ion bunch a constant axial acceleration electric field that travels down the line in synchronism with the ions. Several methods of driving the helix have been considered. Presently, the best method of generating the waveform and also maintaining the high voltage integrity appears to be a transformer primary loosely coupled to the front of the helix, generating the desired waveform and achieving a voltage step-up from primary to secondary (the helix). This can reduce the drive voltage that must be brought into the helix enclosure through the feedthroughs by factors of 5 or more. The accelerating gradient is limited by the voltage holding of the vacuum insulator, and the material and helix geometry must be chosen appropriately. The helix must also be terminated into its characteristic impedance, and designs of terminations incorporated into the helix internal enclosure are presented in the paper.

*Briggs, et al, "Helical Pulseline Structures for Ion Acceleration," this conference.

FPAT037 Electromagnetic Simulations of Helical-Based Ion Acceleration Structures ion, simulation, injection, pulsed-power 2485
  • S.D. Nelson, G.J. Caporaso, A. Friedman, B.R. Poole
    LLNL, Livermore, California
  • R.J. Briggs
    SAIC, Alamo, California
  • W. Waldron
    LBNL, Berkeley, California
  Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

Helix structures have been proposed* for accelerating low energy ion beams using MV/m fields in order to increase the coupling effeciency of the pulsed power system and to tailor the electromagnetic wave propagation speed with the particle beam speed as the beam gains energy. Calculations presented here show the electromagnetic field as it propagates along the helix structure, field stresses around the helix structure (for voltage breakdown determination), optimizations to the helix and driving pulsed power waveform, and simulations showing test particles interacting with the simulated time varying fields.

*"Helical Pulseline Structures for Ion Acceleration," Briggs, Reginato, Waldron, this conference.

FPAT038 Electromagnetic Simulations of Dielectric Wall Accelerator Structures for Electron Beam Acceleration simulation, impedance, acceleration, monitoring 2550
  • S.D. Nelson, B.R. Poole
    LLNL, Livermore, California
  Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

Dielectric Wall Accelerator (DWA) technology incorporates the energy storage mechanism, the switching mechanism, and the acceleration mechanism for electron beams. Electromagnetic simulations of DWA structures includes these effects and also details of the switch configuration and how that switch time affects the electric field pulse which accelerates the particle beam. DWA structures include both bi-linear and bi-spiral configurations with field gradients on the order of 20MV/m and the simulations include the effects of the beampipe, the beampipe walls, the DWA High Gradient Insulator (HGI) insulating stack, wakefield impedance calculations, and test particle trajectories with low emittance gain. Design trade-offs include the transmission line impedance (typically a few ohms), equilibration ring optimization, driving switch inductances, and a layer-to-layer coupling analysis and its affect on the pulse rise time.

FOAA008 Superconducting RF Development at Nuclear Science Centre linac, vacuum, electron, ion 625
  • A. Roy
    NSC, New Delhi
  Funding: Nuclear Science Centre, New Delhi, India.

A Superconducting Linac is being installed as a booster for the 15 UD Pelletron accelerator at Nuclear Science Centre (NSC). The accelerating structure for this linac is a Nb QWR cavity, designed and fabricated as a joint collaboration between NSC 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 NSC. Three quarter wave resonator (QWR) cavities have been fabricated using the in-house facility. This facility has been used for repairs on the resonators which sprung leaks. Fabrication of fifteen resonators for the second and third linac modules is under progress. Eight resonators along with a superconducting solenoid has been installed in the first linac cryostat and tested for energy gain with a pulsed beam of 90 MeV Si from the Pelletron. Acceleration of the ions to 96 MeV was measured downstream and beam transmission through the linac was measured to be ~ 100%.