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Paper Title Other Keywords Page
MOPA006 Theory and Reality of Beam-Beam Effects at Hadron Colliders antiproton, proton, beam-beam-effects, emittance 544
  • Y. Alexahin
    Fermilab, Batavia, Illinois
  The beam-beam phenomena in hadron colliders is just as rich as in e+e- machines: orbit and focusing perturbations, excitation of nonlinear resonances, coherent tuneshifts. Moreover, the absence of radiation damping and long duration of a store permit even high-order (and correspondingly weak) resonances to manifest themselves presenting a major challenge for both theoretical analysis and machine operation. The recent progress in understanding of and coping with the beam-beam effects at hadron colliders, primarily at the Tevatron, is discussed.  
MOPC001 Final Results from the Novel Multiturn Extraction Studies at CERN Proton Synchrotron extraction, octupole, proton, septum 117
  • M. Giovannozzi, R. Cappi, S.S. Gilardoni, M. Martini, E. Métral, R.R. Steerenberg
    CERN, Geneva
  • A.-S. Müller
    FZK, Karlsruhe
  Recently a novel approach to perform multi-turn extraction was proposed based on beam splitting in the transverse phase space by means of trapping inside stable islands. An experimental campaign was launched since the year 2002 to assess the feasibility of such an extraction scheme at the CERN Proton Synchrotron. During the year 2004 run, a high-intensity single-bunch beam was successfully split and the generated beamlets separated without any measurable losses. The latest experimental results are presented and discussed in details in this paper. These achievements represent a substantial step forward with respect to what achieved in previous years, as only a low-intensity bunch could be split without losses. Furthermore, this opens the possibility of using such a technique for routine operation with the high-intensity proton beams required for the planned CERN Neutrino to Gran Sasso Project.  
MOPC003 Benchmarking of Simulation Codes Based on the Montague Resonance in the CERN Proton Synchrotron simulation, lattice, emittance, focusing 330
  • I. Hofmann, G. Franchetti
    GSI, Darmstadt
  • J.F. Amundson, P. Spentzouris
    Fermilab, Batavia, Illinois
  • S.M. Cousineau, J.A. Holmes
    ORNL, Oak Ridge, Tennessee
  • M. Giovannozzi, E. Métral
    CERN, Geneva
  • F.W. Jones
    TRIUMF, Vancouver
  • A.U. Luccio
    BNL, Upton, Long Island, New York
  • S. Machida
    KEK, Ibaraki
  • J. Qiang, R.D. Ryne
    LBNL, Berkeley, California
  Experimental data on emittance exchange by the space charge driven ‘‘Montague resonance'' have been obtained at the CERN Proton Synchrotron in 2002-04 as a function of the working point. These data are used to advance the benchmarking of major simulation codes (ACCSIM, IMPACT, MICROMAP, ORBIT, SIMBAD, SIMPSONS, SYNERGIA) currently employed world-wide in the design or performance improvement of high intensity circular accelerators. In this paper we summarize the experimental findings and compare them with the first three steps of simulation results of the still progressing work.  
MOPC009 Experiments on LHC Long-Range Beam-Beam Compensation and Crossing Schemes at the CERN SPS in 2004 emittance, simulation, dynamic-aperture, hadron 686
  • F. Zimmermann, J.-P. Koutchouk, F. Roncarolo, J. Wenninger
    CERN, Geneva
  • Y. Papaphilippou
    ESRF, Grenoble
  • T. Sen, V.D. Shiltsev
    Fermilab, Batavia, Illinois
  Experiments with two prototype long-range beam-beam compensators (current-carrying wires) during the 2004 CERN SPS run explored the efficiency of a proposed long-range beam-beam compensation for the LHC. In addition, the SPS compensators were also used to 'simulate' the effect of different planes of crossing at two LHC interaction points. We present the experimental results and compare them with computer simulations.  
MPPE004 Evaluation of Nonlinear Effects in the 3GeV Rapid Cycling Synchrotron of J-PARC dipole, sextupole, simulation, multipole 916
  • H. Hotchi, F. Noda, N. Tani
    JAERI/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • J. Kishiro, S. Machida, A.Y. Molodojentsev
    KEK, Ibaraki
  In order to accelerate an ultra-high intense beam with small particle losses, the 3GeV Rapid Cycling Synchrotron (RCS) of J-PARC, which is being constructed at JAERI, has a large acceptance. In this case the nonlinearity associated with the motion of particles at large amplitude and large momentum deviation plays a significant role. The sources of nonlinear magnetic fields in RCS are mainly connected with the fringe of the main dipole and quadrupole magnets and with the sextupole magnets used for the linear chromaticity correction. In this paper, we will present simulation results including such nonlinear effects. In addition, the possible correction scheme for the induced transverse resonances will be discussed.  
MPPE005 Dynamic Aperture and Resonance Correction for JPARC-RCS sextupole, injection, dynamic-aperture, quadrupole 979
  • A.Y. Molodojentsev, E. Forest, S. Machida
    KEK, Ibaraki
  • H. Hotchi, F. Noda, M.J. Shirakata, Y. Shobuda, H. Suzuki, K. Yamamoto
    JAERI/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • Y. Ishi
    Mitsubishi Electric Corp, Energy & Public Infrastructure Systems Center, Kobe
  Main intrinsic field nonlinearities, which are common for synchrotrons with large aperture, are the nonlinear field of the bending magnets, the fringing field of the magnets and the sextupole field nonlinearity, used for the chromaticity correction. The particle motion in the ring bending magnets has been analyzed by two methods: (1) by direct integration of the particle motion equations in the 3D magnetic field (Tosca output), based on the 4th order Runge-Kutta integrator and (2) by determination the transfer 8th order map of the bending magnet by using the Gaussian wavelet in the 3D space. The second technique allows us to use powerful tools such as the normal form analysis, to define the resonance driving terms, which can be used for the resonance correction. As the result of this study it was shown that the main limitation of the RCS dynamic aperture can be caused by the structure normal sextupole-order resonance and the normal octupole-order resonance. Other high-order resonances have smaller effects on the particles motion than the resonances mentioned above. The correction scheme to improve the dynamic aperture near the normal sextupole-order resonance has been analyzed.  
MPPE014 Non-Linear Beam Dynamics Studies of the Diamond Storage Ring coupling, 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.  
MPPE015 Non-Linear Ring Model Calibration with Frequency Analysis of Betatron Oscillations sextupole, lattice, target, betatron 1452
  • R. Bartolini
    Diamond, Oxfordshire
  • F. Schmidt
    CERN, Geneva
  A precise model of an accelerator ring is crucial to achieve ultimate performance both in synchrotron light sources and high energy synchrotrons. Algorithms have been developed to calibrate the linear model of the ring. They have been successfully applied experimentally to determine and correct the linear optics of the machine. More recently the Frequency Map Analysis has been used to model also the non-linear optics. We propose here a technique based on the fit of non-linear spectral lines to recover the non-linear driving terms and to compensate the non-linear field errors around the ring.  
MPPE025 Dynamical Effects Due to Fringe Field of the Magnets in Circular Accelerators quadrupole, dynamic-aperture, dipole, multipole 1907
  • Y. Cai, Y. Nosochkov
    SLAC, Menlo Park, California
  Funding: Work supported by the Department of Energy under Contract No. DE-AC02-76SF00515.

The leading Lie generators, including the chromatic effects, due to hard edge fringe field of single multipole and solenoid are derived from the vector potentials within a Halmitonian system. These nonlinear generators are applied to the interaction region of PEP-II to analyze the linear errors due to the feed-down from the off-centered quadrupoles and solenoid. The nonlinear effects of tune shifts at large amplitude, the synchro-betatron sidebands near half integer and their impacts on the dynamic aperture are studied in the paper.

MPPE028 Non Linear Error Analysis from Orbit Measurements in SPS and RHIC sextupole, simulation, interaction-region, scattering 2012
  • J.F. Cardona
    UNAL, Bogota D.C
  • R. Tomas
    BNL, Upton, Long Island, New York
  Funding: U.S. Department of Energy and Colciencias.

Recently, an "action and phase" analysis of SPS orbits measurements proved to be sensitive to sextupole components intentionally activated at specific locations in the ring. In this paper we attempt to determine the strenght of such sextupoles from the measured orbits and compare them with the set values. Action and phase analysis of orbit trayectories generated by RHIC models with non linearities will also be presented and compare with RHIC experiments.

MPPE030 Comparison of Off-Line IR Bump and Action-Angle Kick Minimization sextupole, octupole, simulation, interaction-region 2116
  • Y. Luo, F.C. Pilat, V. Ptitsyn, D. Trbojevic, J. Wei
    BNL, Upton, Long Island, New York
  Funding: Work supported by U.S. DOE under contract No. DE-AC02-98CH10886.

The interaction region bump (IR bump) nonlinear correction method has been used for the sextupole and octupole field error on-line corrections in the Relativistic Heavy Ion Collider (RHIC). Some differences were found for the sextupole and octupole corrector strengths between the on-line IR bump correction and the predictions from the action-angle kick minimization. In this report we compare the corrector strengths from these two methods based on the RHIC Blue ring lattice with the IR nonlinear modeling. The comparison confirms the differences between resulting corrector strengths. And the reason for the differences is found and discussed. It is followed by a further discussion of the operational IR bump applications to the octupole, and skew sextupole and skew quadrupole field error corrections.

MPPE038 Synchrotron Sidebands of a Linear Differential Coupling Resonance coupling, 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.  
MPPE042 6-D BEAM DYNAMICS IN AN ISOCHRONOUS FFAG RING acceleration, factory, closed-orbit, injection 2693
  • F. Meot
    CEA/DSM/DAPNIA, Gif-sur-Yvette
  • F. Lemuet
    CERN, Geneva
  • G. Rees
    CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon
  Funding: CEA/DAPNIA and CERN.

Numerical ray-tracing tools for 6-D tracking in FFAG accelerators have been developed. They are applied to the simulation of muon acceleration in the newly introduced isochronous type of FFAG ring designed for 16-turn, 8 to 20~GeV muon acceleration in the Neutrino Factory.

MPPE059 Precision Measurement of Coupling Ellipses Parameters in a Storage Ring coupling, lattice, 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.

MPPE064 Dynamic Aperture Study and Lifetime Improvement at the Advanced Photon Source dynamic-aperture, sextupole, coupling, 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%.

MPPE082 Non-Linear Beam Dynamics in High Resolution Multi-Pass Time of Flight Mass Separator ion, simulation, extraction, ion-source 4105
  • V.A. Shchepunov
    ORAU, Oak Ridge, Tennessee
  • H. Wollnik
    JIHIR, Oak Ridge, Tennessee
  Funding: This work was supported by the UNIRIB collaboration and Oak Ridge Associated Universities.

A multi-pass time-of-flight (MTOF) mass separator is under development by the UNIRIB collaboration. The MTOF consists of two coaxial electrostatic mirrors, focusing lenses and auxiliary injection, extraction and separation elements. The injected ions having almost the same energy but different masses undergo hundreds or thousands of reflections between the mirrors. In the course of this periodic motion, the ions of different masses and hence velocities are spatially separated in longitudinal direction. The periodic motion in the MTOF has been investigated with a recently developed ray tracing program utilizing the canonical integration technique. Results of the performed numerical simulations are discussed. The simulations displayed nonlinear character of the ion’s behavior both in transverse and longitudinal phase spaces. The ion’s transverse stability and longitudinal isochronicity were the matters of primary attention. It is shown in particular that at transverse tunes of around q=0.75 the system can be adjusted to be isochronous up to at least the 3rd order of the ToF optical aberrations.

MPPP008 Equilibrium Beam Invariants of an Electron Storage Ring with Linear x-y Coupling damping, coupling, 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.

MPPP013 Stabilizing Low Frequency Beam Motion in the Tevatron optics, damping, quadrupole, feedback 1353
  • V.H. Ranjbar
    Fermilab, Batavia, Illinois
  Funding: Operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the United States Department of Energy.

A feed back orbit stabilization system has been developed using a set of BPMS and existing Tevatron corrector magnets to stabilize beam motion up to 50 microns below 25 Hz. The construction of this system is described and the stability limits and magnitude of beam motion reduction is explored.

MPPP020 RF Phase Modulation at the LNLS Electron Storage Ring simulation, synchrotron, single-bunch, beam-loading 1686
  • N.P. Abreu, N.P. Abreu
    UNICAMP, Campinas, São Paulo
  • R.H.A. Farias, P.F. Tavares
    LNLS, Campinas
  Funding: FAPESP

In the Brazilian Electron Storage Ring, we observed that modulating the phase of accelerating fields at twice the synchrotron frequency suppressed remarkably well a longitudinal coupled-bunch mode of the beam driven by one of the RF cavities. We present results of a set of systematic measurements, in single and multi-bunch mode, aimed at characterizing the effects of the modulation on the beam. We also compare those experiments with the results of tracking simulations.

MPPP031 The CERN-SPS Experiment on Microwave Transmission Through the Beam Pipe electron, cyclotron, injection, dipole 2212
  • T. Kroyer, T. Kroyer
    TU Vienna, Vienna
  • F. Caspers, E. Mahner
    CERN, Geneva
  Funding: Ministry for Education, Science and Culture, Austria.

In the CERN SPS microwave transmission measurements through beampipe sections with a length of 30 m and 7 m meter respectively have been carried out in the frequency range 2-4 GHz since spring 2003. Here we report on new results obtained with improved measurement techniques during the 2004 run. Observation techniques include a fast real time scope, spectrum analyser IF and video output signal registration and baseband signal observation using a PC soundcard. The unexpected beam induced amplitude modulation has been confirmed on all kinds of available beams including single bunches. It was found that there is a correlation between the amount of beam induced signal attenuation and the beam losses registered by external scintillators. Potential theoretical models are discussed.

MPPP037 A Model Study of Transverse Mode Coupling Instability at NSLS-II. impedance, vacuum, undulator, damping 2500
  • A. Blednykh, J.-M. Wang
    BNL, Upton, Long Island, New York
  The vertical impedances of the preliminary designs of NSLS-II MGUs are calculated by means of GdfidL code. The TMCI thresholds corresponding to these impedances are estimated using an analytically solvable model.  
MPPP044 Impedance Calculation for Ferrite Inserts impedance, space-charge, beam-losses, vacuum 2818
  • S.-Y. Lee, S. Breitzmann
    IUCF, Bloomington, Indiana
  • K.Y. Ng
    Fermilab, Batavia, Illinois
  Funding: NSF PHY-0244793; DOE DE-FG02-92ER40747.

Passive ferrite inserts were used to compensate the space charge impedance in high intensity space charge dominated accelerators. We study the narrowband longitudinal impedance of these ferrite inserts. We find that the shunt impedance and the quality factor for ferrite inserts are inversely proportional to the imaginary part of the permeability of ferrite materials. We also provide a receipe for truly passive space charge impedance compensation and, at the same time, avoiding the narrowband microwave instabilities.

MPPT028 An Air Bearing Rotating Coil Magnetic Measurement System quadrupole, multipole, dipole, permanent-magnet 2038
  • S.C. Gottschalk, K.W. Kangas, D.J. Taylor, W.J. Thayer
    STI, Washington
  This paper describes a rotating coil magnetic measurement system supported on air bearings. The design is optimized for measurements of 0.1micron magnetic centerline changes on long, small aperture quadrupoles. Graphite impregnated epoxy resin is used for the coil holder and coil winding forms. Coil holder diameter is 11 mm with a length between supports of 750mm. A pair of coils is used to permit quadrupole bucking during centerline measurements. Coil length is 616mm, inner radius 1.82mm, outer radius 4.74mm. The key features of the mechanical system are simplicity; air bearings for accurate, repeatable measurements without needing warm up time and a vibration isolated stand that uses a steel-topped Newport optical table with air suspension. Coil rotation is achieved by a low noise servo motor controlled by a standalone Ethernet servo board running custom servo software. Coil calibration procedures that correct wire placement errors, tests for mechanical resonances, and other system checks will also be discussed.  
MPPT046 Superconducting Helical Snake Magnet for the AGS dipole, magnet-design, proton, acceleration 2935
  • E. Willen, M. Anerella, J. Escallier, G. Ganetis, A. Ghosh, R.C. Gupta, M. Harrison, A.K. Jain, A.U. Luccio, W.W. MacKay, A. Marone, J.F. Muratore, S.R. Plate, T. Roser, N. Tsoupas, P. Wanderer
    BNL, Upton, Long Island, New York
  • M. Okamura
    RIKEN, Saitama
  Funding: DOE

A superconducting helical magnet has been built for polarized proton acceleration in the Brookhaven AGS. This "partial Snake" magnet will help to reduce the loss of polarization of the beam due to machine resonances. It is a 3 T magnet some 1940 mm in magnetic length in which the dipole field rotates with a pitch of 0.2053 degrees/mm for 1154 mm in the center and a pitch of 0.3920 degrees/mm for 393 mm in each end. The coil cross-section is made of two slotted cylinders containing superconductor. In order to minimize residual offsets and deflections of the beam on its orbit through the Snake, a careful balancing of the coil parameters was necessary. In addition to the main helical coils, a solenoid winding was built on the cold bore tube inside the main coils to compensate for the axial component of the field that is experienced by the beam when it is off-axis in this helical magnet. Also, two dipole corrector magnets were placed on the same tube with the solenoid. A low heat leak cryostat was built so that the magnet can operate in the AGS cooled by several cryocoolers. The design, construction and performance of this unique magnet will be summarized.

TPAE010 Resonant Excitation of Selected Modes by a Train of Electron Bunches in a Rectangular Dielectric Wakefield Accelerator electron, single-bunch, radiation, simulation 1174
  • I.N. Onishchenko, N. Onishchenko, G. Sotnikov
    NSC/KIPT, Kharkov
  • T.C. Marshall
    Yale University, Physics Department, New Haven, CT
  Funding: This work was partly supported by CRDF award #UP2-2569-KH-04

The dielectric wake field accelerator is based on particle acceleration by wake fields excited in a dielectric waveguide by a regular sequence of electron bunches. Enhancement of the accelerating field can be achieved using two phenomena: coherent excitation by many bunches (multibunch effect) and constructive interference of many excited eigenmodes (multimode effect). It was believed that the latter is possible only for planar slab geometry in which the excited modes are equally spaced in frequency. By analysis and simulation, in this presentation the effect of wake field superposition to high amplitude is demonstrated for arbitrary rectangular geometry that is more realizable in experiment. We find this result using simultaneous multibunch and multimode operation providing the repetition frequency of the bunch sequence is equal to the frequency difference between selected modes, whereupon resonant oscillation takes place. Moreover, it is shown that for an appropriate choice of selected modes and bunch repetition frequency a "quasimonopolar” peaked wake field can be excited.

TPAE026 Wakefields in a Dielectric Tube with Frequency Dependent Dielectric Constant impedance, plasma, laser, damping 1916
  • R. Siemann, A. Chao
    SLAC, Menlo Park, California
  Funding: U.S. Department of Energy.

Dielectric laser driven accelerators could operate at a fundamental mode frequency where consideration must be given to the frequency dependence of the dielectric constant when calculating wakefields. Wakefields are calculated for a frequency dependence that arises from a single atomic resonance. Causality is considered, and the effect on the short range wakefield is calculated.

TPAE029 High-Harmonic Inverse Free-Electron-Laser Interaction at 800 nm electron, laser, simulation, undulator 2113
  • C.M.S. Sears, E.R. Colby, B.M. Cowan, R. Siemann, J.E. Spencer
    SLAC, Menlo Park, California
  • R.L. Byer, T. Plettner
    Stanford University, Stanford, Califormia
  Funding: This work supported by Department of Energy contracts DE-AC03-76SF00515 (SLAC) and DE-FG03-97ER41043-II (Stanford).

The inverse Free Electron Laser (IFEL) interaction has recently been proposed and used as a short wavelength modulator forμbunching of beams for laser acceleration experiments*,**. These experiments utilized the fundamental of the interaction between the laser field and electron bunch. In the current experiment, we explore the higher order resonances of the IFEL interaction from a 3 period, 1.8 centimeter wavelength undulator with a picosecond, 0.25 mJ/pulse laser at 800 nm. The resonances are observed by adjusting the gap of the undulator while keeping the beam energy constant. We will also discuss diagnostics for obtaining beam overlap and statistical techniques used to account for machine drifts and analyze the data.

*W. D. Kimura, et. al., Phys. Rev. S.T. Acc. & Beams 4 101301 (2001). ** P. Musumeci, et. al., AAC 2004 Proceedings. Pg 170.

TPAE033 Experimental and Numerical Studies of Particle Acceleration by an Active Microwave Medium laser, acceleration, simulation, radiation 2275
  • P. Schoessow
    Tech-X, Boulder, Colorado
  • A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio
  There has been considerable theoretical work on the so-called PASER concept, in which a particle beam is accelerated directly by absorbing energy from an active medium, analogous to the amplification of an optical signal in a laser. Use of an active microwave (maser) medium would have the advantage of requiring relaxed beam quality (mm vs. nm characteristic beam dimensions). Recent work using electron paramagnetic resonance (EPR) techniques has demonstrated activity in the microwave regime (i.e. negative imaginary part of the magnetic susceptibility) for a class of organic compounds. A solution of fullerene (C60) in a liquid crystal solvent has been reported in the literature to possess a maser transition in the X-band region. An external DC magnetic field is required to obtain the effect; the frequency of the maser transition is adjustable by varying the magnetic field strength. We will report on the development of numerical and laboratory tools to evaluate the use of this material for accelerator applications, and evaluate the feasibility of an accelerating structure based on an active microwave medium.  
TPAE054 Ultraintense and Ultrashort Laser Pulses from Raman Amplification in Plasma for Laser-Plasma Accelerators simulation, plasma, laser, electron 3274
  • M.S. Hur, G.-H. Kim, H. Suk
    KERI, Changwon
  • A.E. Charman, R.R. Lindberg, J.S. Wurtele
    LBNL, Berkeley, California
  Funding: Korea Electrotechnology Research Institute, Korea; Creative Research Initiatives, Korea.

We present analysis and simulations of kinetic effects in the Raman pulse amplification in plasma. An ultraintense and ultrashort laser pulse is a very essential part in an advanced acceleration scheme using laser and plasma. To make strong pulses, a noble scheme of using Raman backscatter in plasma was proposed and has been studied intensively.* The Raman amplification in plasma does not have a restriction in material damage threshold. However, for the new amplifier to be a promising alternative of the CPA technique, more extensive studies on various issues are required. One of the fundamental issues is the electron kinetic effect such as particle trapping or wavebreaking. We present a theoretical analysis of the kinetic effect; a new kinetic term is derived to be added to the fluid model and the effect of the new term is verified by averaged-PIC (aPIC)** simulations. Various one dimensional and semi-two dimensional aPIC simulations of pulse amplification are presented. We discuss the future application of the Raman scheme to upgrading the laser pulse of the Center of Advanced Accelerator in KERI, which are currently 2 TW and 700 fs, into a few more TW and less than 100 fs.

*V. M. Malkin, G. Shvets, and N. J. Fisch, Phys. Rev. Lett. vol. 82, 4448 (1999).**M. S. Hur, G. Penn, J. S. Wurtele, and R. Lindberg, Phys. Plasmas vol. 11, 5204 (2004).

TPAE061 Experimental Investigation of an X-Band Tunable Dielectric Accelerating Structure vacuum, acceleration, polarization, electron 3529
  • A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio
  • W. Gai, J.G. Power
    ANL, Argonne, Illinois
  • S.F. Karmanenko, A. Semenov
    Eltech University, St. Petersburg
  • E. Nenasheva
    Ceramics Ltd., St. Petersburg
  • P. Schoessow
    Tech-X, Boulder, Colorado
  Funding: U.S. Department of Energy.

Experimental study of a new scheme to tune the resonant frequency for dielectric based accelerating structure (driven either by the wakefield of a beam or an external rf source) is underway. The structure consists of a single layer of conventional dielectric surrounded by a very thin layer of ferroelectric material situated on the outside. Carefully designed electrodes are attached to a thin layer of ferroelectric material. A DC bias can be applied to the electrodes to change the permittivity of the ferroelectric layer and therefore, the dielectric overall resonant frequency can be tuned. In this paper, we present the test results for an 11.424 GHz rectangular DLA prototype structure that the ferroelectric material's dielectric constant of 500 and show that a frequency tuning range of 2% can be achieved. If successful, this scheme would compensate for structure errors caused by ceramic waveguide machining tolerances and dielectric constant heterogeneity.

TPAE066 Robust Autoresonant Excitation in the Plasma Beat-Wave Accelerator: A Theoretical Study plasma, laser, electron, beat-wave 3688
  • A.E. Charman, R.R. Lindberg, J.S. Wurtele
    UCB, Berkeley, California
  • L. Friedland
    The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem
  Funding: Division of High Energy Physics, U.S. Department of Energy, DARPA, U.S. Department of Defense.

A modified version of the Plasma Beat-Wave Accelerator scheme is introduced and analyzed, which is based on autoresonant phase-locking of the nonlinear Langmuir wave to the slowly chirped beat frequency of the driving lasers via adiabatic passage through resonance. This new scheme is designed to overcome some of the limitations of previous approaches, namely relativistic detuning and nonlinear modulations in the driven Langmuir wave amplitude, and sensitivity to frequency mismatch from density fluctuations. As in previous schemes, instabilities of the ionic background ultimately limit the useful interaction time, but nevertheless peak electric fields approaching the wave-breaking limit seem readily attainable. Compared to traditional approaches, the autoresonant scheme achieves larger accelerating electric fields for given laser intensity; the plasma wave excitation is more robust to variations in plasma density; it is largely insensitive to the choice of chirp rate, provided that chirping is sufficiently slow; and the quality and uniformity of the resulting plasma wave and its suitability for accelerator applications may be superior.

TPAP044 Observations of Snake Resonance in RHIC polarization, betatron, injection, proton 2839
  • M. Bai, H. Huang, W. Mac Kay, V. Ptitsyn, T. Roser, S. Tepikian
    BNL, Upton, Long Island, New York
  • S.-Y. Lee, F. Lin
    IUCF, Bloomington, Indiana
  Funding: The work was performed under the auspices of the U.S. Department of Energy.

Siberian snakes now become essential in the polarized proton acceleration. With proper configuration of Siberian snakes, the spin precession tune of the beam becomes $\frac{1}{2}$ which avoids all the spin depolarizing resonance. However, the enhancement of the perturbations on the spin motion can still occur when the betatron tune is near some low order fractional numbers, called snake resonances, and the beam can be depolarized when passing through the resonance. The snake resonances have been confirmed in the spin tracking calculations, and observed in RHIC with polarized proton beam. Equipped with two full Siberian snakes in each ring, RHIC provides us a perfect facility for snake resonance studies. This paper presents latest experimental results. New insights are also discussed.

TPAP048 Optimization of the Phase Advance Between RHIC Interaction Points quadrupole, lattice, proton, luminosity 3031
  • R. Tomas
    CELLS, Bellaterra (Cerdanyola del Vallès)
  • W. Fischer
    BNL, Upton, Long Island, New York
  Funding: U.S. department of Energy.

We consider the scenario of having two identical Interaction Points (IPs) in the Relativistic Heavy Ion Collider (RHIC). The strengths of beam-beam resonances strongly depend on the phase advance between these two IPs and therefore certain phase advances could improve beam lifetime and luminosity. We compute the dynamic aperture as function of the phase advance between these IPs to find the optimum settings. The beam-beam interaction is treated in the weak-strong approximation and a complete non-linear model of the lattice is used. For the current RHIC proton working point (0.69,0.685) the design lattice is found to have the optimum phase advance. However this is not the case for other working points.

TPAP057 Beam-Beam Simulations for the eRHIC Electron Ring electron, luminosity, simulation, emittance 3399
  • C. Montag
    BNL, Upton, Long Island, New York
  Funding: Work performed under the auspices of the U.S. Department of Energy.

To study collisions between polarized electrons and heavy ions or polarized protons at high energy, adding a 10 GeV electron storage ring to the existing RHIC facility is currently under consideration. To achieve high luminosities, vertical beam-beam tuneshift parameters of 0.08 are required for the electron beam. Simulation studies are being performed to study the feasibility of these high tuneshift parameters and to explore the potential for even higher tuneshifts. Recent results of these studies are presented.

TPAT014 A Novel Technique for Multiturn Injection in a Circular Accelerator Using Stable Islands in Transverse Phase Space injection, extraction, simulation, septum 1377
  • M. Giovannozzi, J. Morel
    CERN, Geneva
  By applying a time-reversal to the multiturn extraction recently proposed a novel approach to perform multiturn injection is proposed. It is based on the use of stable islands of the horizontal phase space generated by means of sextupoles and octupoles. A particle beam can be injected into stable islands of phase space, and then a slow tune variation allows merging the beam trapped inside the islands. The results of numerical simulations will be presented and discussed in details, showing how to use the proposed approach to generate hollow bunches.  
TPAT017 Transverse Impedance of Elliptical Tapers impedance, vacuum, synchrotron, undulator 1535
  • B. Podobedov, S. Krinsky
    BNL, Upton, Long Island, New York
  Funding: Work supported by the U.S. DOE.

The geometric impedance of small-gap undulator chambers is of paramount importance for modern light sources because it may drive transverse single bunch instabilities. Analytical expressions are derived for the transverse impedance assuming a slowly tapered vacuum chamber with a confocal elliptical cross-section. The analytical results are confirmed by numerical simulations with the GdfidL Electromagnetic Field simulator and they yield the correct asymptotic limits for both round and flat chambers.

TPAT018 Stability of Barrier Buckets with Short or Zero Barrier Separations synchrotron, quadrupole, dipole, beam-losses 1589
  • K.Y. Ng
    Fermilab, Batavia, Illinois
  A barrier bucket with small separation between the rf barriers (relative to the barrier widths) or even zero separation has its synchrotron tune decreasing rather slowly towards the boundary of the bucket. As a result, large area at the bucket edges can become unstable under the modulation of rf voltage and rf phase. Application is made to those barrier buckets used in the process of momentum mining on the issues of bunch-distribution distortion and particle loss.  
TPAT048 The Transverse Nonlinear Tune Shift as Stabilising Factor in Halo Creation in Space Charge Dominated Beam space-charge, focusing, linac, quadrupole 3004
  • N.E. Vasyukhin, Y. Senichev, R. Tölle
    FZJ, Jülich
  Funding: We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" program (CARE, contract number RII3-CT-2003-506395).

One of the most important problems for space charge dominated beam in the low energy part of superconducting linac is halo creation. Many authors show one of the key effects in halo creatiation is parametric resonance due to the mismatched beta-function oscillation (between core and particle). To estimate parametric resonance conditions the nonlinear tune shift for binomial distributed beam is described theoretically in this article. Simultaneously the beam dynamics simulation 3D PIC code was developed. The transverse oscillation frequencies compared with parametric resonance criteria. As a result the recommendation for space charge shift is concluded to minimize halo creation.

TPAT059 Space Charge Experiments and Simulation in the Fermilab Booster booster, simulation, space-charge, injection 3453
  • J.F. Amundson, P. Spentzouris
    Fermilab, Batavia, Illinois
  Funding: Scientific Discovery through Advanced Computing project, "Advanced Computing for 21st Century Accelerator Science and Technology," U.S. DOE/SC Office of High Energy Physics and the Office of Advanced Scientific Computing Research.

We have studied space charge effects in the Fermilab Booster. Our studies include investigation of coherent and incoherent tune shifts and halo formation. We compare experimental results with simulations using the 3-D space charge package Synergia.

TPAT070 Intensity and Bunch-Shape Dependent Beam Loss Simulation for the SIS100 beam-losses, ion, space-charge, lattice 3807
  • G. Franchetti, I. Hofmann, A. Orzhekovskaya, P.J. Spiller
    GSI, Darmstadt
  We have studied the combined influence of magnet nonlinearities, space charge and bunch shapes consistent with different RF scenarios on the long-term loss in the planned SIS100 synchrotron of the FAIR project. The simulation is a 3D tracking with "frozen-in" space charge calculation employing the MICROMAP code. Comparing a one-harmonic RF scenario with an alternative double-harmonic scenario we find that for the same absolute beam loss roughly twice the number of particles can be stored in the double-RF system. Moreover, a barrier bucket RF scenario is found to be loss free. This is due to the fact that loss is caused here by space-charge induced periodic resonance crossing, which is absent for the strictly flat bunch profile of the barrier case.  
TPAT082 Phonon Modes and the Maintenance Condition of a Crystalline Beam lattice, focusing, coupling, 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).

TPPP009 Precise Energy Measurements in Experiments on VEPP-4M Collider polarization, electron, photon, energy-calibration 1138
  • A. Bogomyagkov, V.E. Blinov, V.P. Cherepanov, V. Kiselev, E. Levichev, S.I. Mishnev, N.Yu. Muchnoi, S.A. Nikitin, I.B. Nikolaev, D.M. Nikolenko, A.G. Shamov, E. Shubin, A.N. Skrinsky, Yu.A. Tikhonov, D.K. Toporkov, G.M. Tumaikin
    BINP SB RAS, Novosibirsk
  The series of experiments on mass measurements of J/Psi, Psi', X and D mesons have been done on VEPP4-M collider. The accuracy of obtained masses values for psi mesons exceeded world value more than 3 times. Experiment on mass measuremnt of tau lepton is in progress. All these experiments require absolute energy calibration of the beams. Resonant depolarization technique has been used for most accurate energy measurement with relative accuracy of 1 ppm (10-6). Compton backscattering effect is used in developing facility for fast energy measurements. Moller scattering of the beam on polarized gas jet target has been used for beam polarization measurements.  
TPPP013 Simulations of Parametric Resonance Ionization Cooling of Muon Beams synchrotron, simulation, focusing, lattice 1321
  • K. Beard, S.A. Bogacz, Y.S. Derbenev
    Jefferson Lab, Newport News, Virginia
  • R.P. Johnson, K. Paul, T.J. Roberts
    Muons, Inc, Batavia
  • K. Yonehara
    Illinois Institute of Technology, Chicago, Illinois
  Funding: This work was supported in part by DOE SBIR grants DE-FG02-03ER83722, and 04ER84016.

The technique of using a parametric resonance to allow better ionization cooling is being developed to create small beams so that high collider luminosity can be achieved with fewer muons. In the linear channel that is studied in this effort, a half integer resonance is induced such that the normal elliptical motion of particles in x-x' phase space becomes hyperbolic, with particles moving to smaller x and larger x' as they pass down the channel. Thin absorbers placed at the focal points of the channel then cool the angular divergence of the beam by the usual ionization cooling mechanism where each absorber is followed by RF cavities. Thus the phase space of the beam is compressed in transverse position by the dynamics of the resonance and its angular divergence is compressed by the ionization cooling mechanism. We report the first results of simulations of this process, including comparisons to theoretical cooling rates and studies of sensitivity to variations in absorber thickness and initial beam conditions.

TPPP014 Ionization Cooling Using a Parametric Resonance emittance, focusing, betatron, luminosity 1374
  • Y.S. Derbenev
    Jefferson Lab, Newport News, Virginia
  • R.P. Johnson
    Muons, Inc, Batavia
  Funding: This work was supported in part by DOE SBIR grant DE-FG02-04ER84016.

Muon collider luminosity depends on the number of muons in the storage ring and on the transverse size of the beams in collision. Ionization cooling as it is presently envisioned will not cool the beam sizes sufficiently well to provide adequate luminosity without large muon intensities. A new idea to combine ionization cooling with parametric resonances has been developed that will lead to beams with much smaller sizes so that high luminosity in a muon collider can be achieved with fewer muons. In the linear channel described here, a half integer resonance is induced such that the normal elliptical motion of particles in x-x' phase space becomes hyperbolic, with particles moving to smaller x and larger x' as they pass down the channel. Thin absorbers placed at the focal points of the channel then cool the angular divergence of the beam by the usual ionization cooling mechanism where each absorber is followed by RF cavities. We discuss the theory of Parametric-resonance Ionization Cooling, including the sensitivity to aberrations and the need to start with a beam that has already been cooled adequately.

TPPP017 Beam-Beam Effects in the Ring-Ring Version of eRHIC emittance, beam-beam-effects, luminosity, simulation 1520
  • J. Shi, L. Jin
    KU, Lawrence, Kansas
  • D. Wang, F. Wang
    MIT, Middleton, Massachusetts
  Funding: The U.S. Department of Energy under Grant No. DE-FG02-04ER41288.

The eRHIC is a proposed electron ring at the RHIC that will provide collisions between a polarized 5-10 GeV electron beam and an ion beam from one of the RHIC rings. In order to achieve proposed high luminosity, large bunch current and small beta-functions at the IP has to be employed. Such measures result in large beam-beam parameters, 0.029 and 0.08 for the electron beam and 0.0065 and 0.0033 for the proton beam in the horizontal and vertical plane, respectively, in the current ZDR design. The beam-beam effect especially the coherent beam-beam effect is therefore one of important issues to the eRHIC. Moreover, the proposed configuration of unequal circumferences of the electron and proton rings could further enhance the coherent beam-beam effect. The beam-beam effect of eRHIC has therefore been studied with a self-consistent beam-beam simulation by using the particle-in-cell method. Beam-beam limits of the electron and proton beam were examined as thresholds of the onset of coherent beam-beam instability. For the proposed luminosity, the electron and proton bunch currents optimized with the consideration of the beam-beam effect will be discussed.

TPPP054 Studies of RF Breakdown of Metals in Dense Gases collider, klystron, hadron, vacuum 3259
  • P.M. Hanlet, M. Alsharo'a, R.P. Johnson, M. Kuchnir, K. Paul
    Muons, Inc, Batavia
  • C.M. Ankenbrandt, A. Moretti, M. Popovic, V. Yarba
    Fermilab, Batavia, Illinois
  • D.M. Kaplan, K. Yonehara
    Illinois Institute of Technology, Chicago, Illinois
  Funding: This work was supported in part by DOE STTR grant DE-FG02-02ER86145.

A study of RF breakdown of metals in gases has begun as part of a program to develop RF cavities filled with dense hydrogen gas to be used for muon ionization cooling. A pressurized 800 MHz test cell has been used at Fermilab to compare the conditioning and breakdown behavior of copper, molybdenum, chromium, and beryllium electrodes as functions of hydrogen and helium gas density. These results are compared to the predicted or known RF breakdown behavior of these metals in vacuum.

TPPT007 Application of Highly-Pure Copper Lining to Normal-Conducting RF Cavities for an Electron-Positron Super B Factory factory, target, linac, coupling 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.  
TPPT015 Coupler Matching Techniques for C-Band Accelerating Section target, linac, coupling, 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.  
TPPT035 High-Power RF Testing of a 352-MHz Fast-Ferrite RF Cavity Tuner at the Advanced Photon Source coupling, 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.

TPPT039 Installation and Testing for Commissioning of Normal Conducting RF Linac Segment in the SNS linac, SNS, rfq, klystron 2571
  • Y.W. Kang, A.V. Aleksandrov, D.E. Anderson, M.M. Champion, M. Champion, M.T. Crofford, C. Deibele, G.W. Dodson, R.E. Fuja, P.E. Gibson, P.A. Gurd, T.W. Hardek, G.A. Johnson, P. Ladd, H. Ma, M.P. McCarthy, M.F. Piller, J.Y. Tang, A.V. Vassioutchenko, D.C. Williams
    ORNL, Oak Ridge, Tennessee
  • J.A. Billen, J.T. Bradley, D. Rees, W. Roybal, J. Stovall, K.A. Young, L.M. Young
    LANL, Los Alamos, New Mexico
  The Spallation Neutron Source (SNS) linac employs both normal conducting and superconducting linac cavities that will inject a 1.0 GeV proton beam into its accumulator ring. The normal conducting segment of this linac accelerates the beam to 185 MeV and employs one RFQ and six DTL cavities powered by seven 2.5 MW, 402.5 MHz klystrons and four CCL modules powered by four 5.0 MW, 805 MHz klystrons. Installation and RF conditioning of the RF equipment for normal conducting linac segment have been completed at ORNL with the support of LANL experts. After conditioning the accelerating structures, the linac has been successfully commissioned with beam. This paper reviews the experience in installation, RF conditioning, and commissioning of the normal conducting linac accelerating structures and RF subsystems. Checkout and operation of the RF systems and structures including conditioning procedure establishment and test results compared to the RF design specifications will be discussed.

SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge.

TPPT040 X-Band Dipole Mode Deflecting Cavity for the UCLA Neptune Beamline diagnostics, dipole, vacuum, simulation 2627
  • R.J. England, B. O'Shea, J.B. Rosenzweig, G. Travish
    UCLA, Los Angeles, California
  • D. Alesini
    INFN/LNF, Frascati (Roma)
  Funding: This work was funded by the Department of Energy under Grant No. DE-FG03-92ER40693.

We report progress on the design and construction of a nine-cell dipole (TM 110 mode) cavity for use as a temporal diagnostic of the 14 MeV 300 pC electron bunches generated at the UCLA Neptune Laboratory linear accelerator, with an anticipated temporal resolution of 150 fs at a peak input power of 50 kW. The cavity is a center-fed standing-wave pi-mode structure, operating at 9.6 GHz, and incorporating a knife-edge and gasket assembly which minimizes the need for brazing or welding. Results of initial RF tests are discussed and compared with simulation results obtained using the commercial code HFSS.

TPPT042 The Simulation Calculations and Dielectric Characteristics Investigation of an X-Band Hybrid Dielectric-Iris-Loaded Traveling Accelerating Structure simulation, acceleration, synchrotron, synchrotron-radiation 2720
  • C.-F. Wu, S. Dong, S. Hongbing, D. Jia, H. Lin, L. Wang
    USTC/NSRL, Hefei, Anhui
  Funding: This work is supported by the National Natural Science Foundation of China(No.10375060,10205014)and the Project of Knowledge Innovation Program of the Chinese Academy of Sciences.

Mafia code has been used to calculate the RF properties versus the geometric parameters and dielectric permittivity for the X-band (f=9.37GHz) hybrid dielectric-iris-loaded traveling accelerating structure. The simulation results show that when the range of the permittivity is about 5-9, the new structure may have lower ratio (about 1) of peak surface electric field at the iris to axial accelerating electric field by optimizing the geometric parameters, while r, Q, r/Q of the new structure being comparable to iris-loaded accelerating structure. The experimental investigations of the permittivity of the ceramics have been made at the X-band by using the cavity perturbation technique. The measured results are in good agreement with the simulation results of Microwave Studio. Furthermore, the stability of the ceramics is examined. A number of experimental results show that the certain ceramic with permittivity of 5.78 is applied to the design of the new accelerating structure.

TPPT058 First Tests of the Superconducting CH-Structure simulation, pick-up, coupling, 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.

TPPT069 Design Considerations for the Mechanical Tuner of the RHIC Electron Cooler SRF Cavity vacuum, controls, damping, cryogenics 3786
  • J. Rank, I. Ben-Zvi, M. Blaskiewicz, H. Hahn, G.T. McIntyre
    BNL, Upton, Long Island, New York
  Funding: Work is supported by the DOD Joint Technology Office and by the U.S. Department of Energy.

The ECX Project, Brookhaven Lab's predecessor to the RHIC e-Cooler, includes a prototype RF tuner mechanism capable of both coarse and fine tuning of the superconducting RF cavity. This tuner is adapted originally from a DESY design concept but with a longer stroke and significantly higher loads due to our very stiff cavity shape. Structural design, kinematics, controls, thermal and RF issues are discussed and certain improvements are proposed.

TPPT070 Development of the Superconducting 3.9 GHz Accelerating Cavity at Fermilab higher-order-mode, simulation, damping, vacuum 3825
  • N. Solyak, T.T. Arkan, P. Bauer, L. Bellantoni, C. Boffo, E. Borissov, H. Carter, H. Edwards, M. Foley, I.G. Gonin, T.K. Khabiboulline, S.C. Mishra, D.V. Mitchell, V. Poloubotko, A.M. Rowe, I. Terechkine
    Fermilab, Batavia, Illinois
  Funding: U.S. Department of Energy.

A superconducting third harmonic accelerating cavity (3.9 GHz) was proposed to improve beam quality in the TTF-like photoinjector. Fermilab has developed, built and tested several prototypes, including two copper 9-cell cavities, and niobium 3-cell and 9-cell cavities. The helium vessel and frequency tuner for the 9-cell cavity was built and tested as well. In cold tests, we achieved a peak surface magnetic field of ~120mT, well above the 70mT specification. The accelerating gradient was limited by thermal breakdown. Studies of the higher order modes in the cavity revealed that the existing cavity design with two HOM couplers will provide sufficient damping of these modes. In this paper we discuss the cavity design, results of the studies and plans for further development.

TPPT074 Simulation Study of Electronic Damping of Microphonic Vibrations in Superconducting Cavities feedback, damping, simulation, coupling 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.

TPPT086 Elliptical Cavity Shape Optimization for Acceleration and HOM Damping laser, damping, single-bunch, impedance 4191
  • H. Wang, R.A. Rimmer, G. Wu
    Jefferson Lab, Newport News, Virginia
  Funding: Supported by the Office of Naval Research, the Joint Technology Office, the Commonwealth of Virginia, the Air Force Research Laboratory, and by DOE Contract DE-AC05-84ER40150.

A normal design process for a superconducting cavity shape is to maximize the R/Q (shunt impedance/intrinsic quality factor) and geometry factor G for a given RF field limit of Bpeak/Eacc or Epeak/Eacc. For the application of an Ampere-class, high current energy recovery linac or storage ring, heavy HOM damping is required. This paper reports on a survey of single cell shapes developed for multi-cell cavities for different projects. Using a set of normalized parameters, we compare the designs for different frequencies and ß structures for the fundamental mode. Using dispersion curve (frequency verse phase advance) calculated by MAFIA for a single cell, we explore further how to optimize the cavity shape to avoid a light cone line crossing at the dangerous resonance frequencies determined by the beam bunch structure or the dangerous (trapped or high R/Q) modes with a low group velocity. We expect such a formulation to inform our development of a 5-cell, optimized cavity shape, with good real estate accelerating gradient and strong HOM damping waveguide structure for the JLab 1MW ERL-FEL project.

TPPT098 VORPAL as a Tool for Three-Dimensional Simulations of Multipacting in Superconducting RF Cavities electron, simulation, plasma, radio-frequency 4332
  • C. Nieter, J.R. Cary, P. Stoltz
    Tech-X, Boulder, Colorado
  • G.R. Werner
    CIPS, Boulder, Colorado
  Considerable resources are required to run three dimensional simulations of multipacting in superconducting rf cavities. Three dimensional simulations are needed to understand the possible roles of non-axisymmetric features such as the power couplers. Such simulations require the ability to run in parallel. We consider the versatile plasma simulation code VORPAL* as a possible platform to study such effects. VORPAL has a general 3D domain decomposition and can run in any physical dimension. VORPAL uses the CMEE library** to model the secondary emission of electrons from metal surfaces. We will present a three dimensional simulation of a simple pillbox rf cavity to demonstrate the potential of VORPAL to be a major simulation tool for superconducting rf cavities.

*C. Nieter and J.R. Cary, J. Comp. Phys. 196 (2004), p. 448. **P.H. Stoltz, ICFA electron cloud work shop, Napa, CA (2004).

WPAE038 Resonance Control Cooling System Performance and Developments SNS, linac, simulation, Spallation-Neutron-Source 2541
  • P.E. Gibson, A.V. Aleksandrov, M.M. Champion, G.W. Dodson, J.P. Schubert, J.Y. Tang
    ORNL, Oak Ridge, Tennessee
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge.

The Spallation Neutron Source (SNS) is an accelerator-based neutron source being built at Oak Ridge National Laboratory. The warm linac portion, designed by Los Alamos, has been installed and commissioned. The warm linac is comprised of six Drift Tube Linac (DTL) tanks and four Coupled Cavity Linac (CCL) modules. For commissioning purposes the accelerating systems have been operated at less than the design 6% duty factor. During lower power operation there is less RF cavity heating. This decrease in heat load causes operational stability issues for the associated Resonance Control Cooling Systems (RCCSs) which were designed for full duty factor operation. To understand this effect operational results have been analyzed and tests have been performed. External system factors have been explored and the resulting impacts defined. Dynamic modeling of the systems has been done via a collaboration with the Institute for Nuclear Research (INR), Moscow, Russia. New RCCS operation code has been implemented. Increases in system performance achieved and solutions employed will be presented.

WPAT003 Glycol-Substitute for High Power RF Water Loads impedance, klystron 841
  • M. Ebert, F.-R. Ullrich
    DESY, Hamburg
  In water loads for high power rf applications, power is dissipated directly into the coolant. Loads for frequencies below approx. 1GHz are ordinarily using an ethylene glycol-water mixture as coolant. The rf systems at DESY utilize about 100 glycol water loads with powers ranging up to 600kW. Due to the increased ecological awareness, the use of glycol is now considered to be problematic. In EU it is forbidden to discharge glycol into the waste water system. In case of cooling system leakages one has to make sure that no glycol is lost. Since it is nearly impossible to avoid any glycol loss in large rf systems, a glycol-substitute was searched for and found. The found sodium-molybdate based substitute is actually a additive for corrosion protection in water systems. Sodium-molybdate is ecologically harmless; for instance, it is also used as fertilizer in agriculture. A homoeopathic dose of 0.4% mixed into deionised water gives better rf absorption characteristics than a 30% glycol mixture. The rf coolant features of this substitute were investigated and tested. The glycol coolant of all rf systems at DESY was substituted. The results of the investigations and tests are presented.  
WPAT015 The Digital Feedback RF Control System of the RFQ and DTL1 for 100 MeV Proton Linac of PEFP feedback, proton, rfq, linac 1443
  • I.H. Yu, Y.J. Han, H.-S. Kang, D.T. Kim, S.-C. Kim, I.-S. Park, J.C. Yoon
    PAL, Pohang, Kyungbuk
  • Y.-S. Cho, H.-J. Kwon, K.T. Seol
    KAERI, Daejon
  Funding: Work supported by the PEFP (Proton Engineering Frontier Project), Korea

The 100 MeV Proton linear accelerator (Linac) for the PEFP (Proton Engineering Frontier Project) will include 1 RFQ and 1 DTL1 at 350 MHz as well as 7 DTL2 cavities at 700 MHz. The low level RF system with the digital feedback RF control provides the field control to accelerate a 20mA proton beam from 50 keV to 20 MeV with a RFQ and a DTL1 at 350M Hz. The FPGA-based digital feedback RF control system has been built and is used to control cavity field amplitude within ± 1% and relative phase within ± 1°. The fast digital processing is networked to the EPICS-based control system with an embedded processor (Blackfin). In this paper, the detailed description of the digital feedback RF control system will be described with the performance test results.

WPAT018 The LEIR RF System impedance, ion, coupling, 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 FinemetŪ 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 coupling, 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.

WPAT034 The CEBAF Separator Cavity Resonance Control System controls, monitoring, linac, electron 2339
  • M.J. Wissmann, AA. Guerra, C. Hovater, T. Plawski
    Jefferson Lab, Newport News, Virginia
  Funding: This work supported by the U.S. Department of Energy under contract DE-AC05-84ER40150.

The CEBAF energy upgrade from 6 GeV to 12GeV will increase the range of beam energies available to the experimental halls. RF deflection cavities (separators) are used to direct the electron beam to the three experimental halls. Consequently with the increase in RF separator cavity gradient needed for the higher energies, RF power will also increase requiring the cavities to have active resonance control. At the 6 GeV energy, the cavities are tuned mechanically and then stabilized with Low Conductivity Water (LCW), which is maintained at constant temperature of 95o Fahrenheit. This is no longer feasible and an active resonance control system, that controls both water temperature and flow has been built. The system uses a commercial PLC with embedded PID controls to control water temperature and flow to the cavities. The system allows the operator to remotely adjust temperature/flow and consequently cavity resonance for the full range of beam energies. Ultimately closed loop control will be maintained by monitoring the cavities reflected power. This paper describes this system.

WPAT038 Instability of the RF Control Loop in the Presence of a High-Q Passive Superconducting Cavity feedback, simulation, superconducting-RF, luminosity 2553
  • S.A. Belomestnykh, R.P.K. Kaplan, J.J.R. Reilly, V. Veshcherevich
    Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
  Funding: Work is supported by the National Science Foundation.

An instability of the active RF cavity field control loop was observed during experiments with beam-driven (passive) superconducting cavities in CESR when the cavity external Q factor was raised to a value above 1x107. A computer model was developed and further experiments have been performed to study this instability and find a way to cure it. The results of simulations are presented alongside the experimental results.

WPAT040 Pushing the Limits: RF Field Control at High Loaded Q linac, beam-loading, klystron, feedback 2642
  • M. Liepe, S.A. Belomestnykh, J. Dobbins, R.P.K. Kaplan, C.R. Strohman, B.K. Stuhl
    Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
  • C. Hovater, T. Plawski
    Jefferson Lab, Newport News, Virginia
  Funding: This work is supported by Cornell University.

The superconducting cavities in an Energy-Recovery-Linac will be operated with a high loaded Q of several 1E7, possible up to 1E8. Not only has no prior control system ever stabilized the RF field in a linac cavity with such high loaded Q, but also highest field stability in amplitude and phase is required at this high loaded Q. Because of a resulting bandwidth of the cavity of only a few Hz, this presents a significant challenge: the field in the cavity extremely sensitive to any perturbation of the cavity resonance frequency due to microphonics and Lorentz force detuning. To prove that the RF field in a high loaded Q cavity can be stabilized, and that Cornell's newly developed digital control system is able to achieve this, the system was connected to a high loaded Q cavity at the JLab IR-FEL. Excellent cw field stability – about 2·10-4 rms in relative amplitude and 0.03 deg rms in phase - was achieved at a loaded Q of 2.1·107 and 1.4E8, setting a new record in high loaded Q operation of a linac cavity. Piezo tuner based cavity frequency control proved to be very effective in keeping the cavity on resonance and allowed reliable to ramp up to high gradients in less than 1 second.

WPAT050 High Power Phase Shifter linac, proton, klystron, power-supply 3123
  • I. Terechkine, G.W. Foster, I.G. Gonin, T.K. Khabiboulline, A. Makarov, N. Solyak, D. Wildman
    Fermilab, Batavia, Illinois
  One of the approaches to power distribution system of a superconducting proton linac that is under discussion at Fermilab requires development of a fast-action, megawatt-range phase shifter. Using two phase shifters with a waveguide hybrid junction can allow independent control of phase and amplitude of RF power at the input of each superconducting cavity of the linac. This promises significant saving in number of klystrons and modulators required for the accelerator. A prototype of a waveguide version of a phase shifter that uses Yttrium-Iron Garnet (YIG) blocks was developed and tested. This report presents design concept of the device and main results of simulation and proof-of-principle tests.  
WPAT055 Enhancements for the 1 MW High Voltage Converter Modulator Systems at the SNS klystron, SNS, cathode, linac 3313
  • D.E. Anderson, J. Hicks, D. E. Hurst, E.R. Tapp, M. Wezensky
    ORNL, Oak Ridge, Tennessee
  • D. Baca, W. Reass
    LANL, Los Alamos, New Mexico
  • V.V. Peplov
    RAS/INR, Moscow
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.

The first-generation high frequency switching megawatt-class high voltage converter modulators (HVCM) developed by Los Alamos National Laboratory for the Spallation Neutron Source at Oak Ridge National Laboratory have been installed and are now operational. Each unit is capable of delivering pulses up to 11 MW peak, 1 MW average power at voltages up to 140 kV to drive klystron(s) rated up to 5 MW. To date, three variations of the basic design have been installed, each optimized to deliver power to a specific klystron load configuration. Design improvements, with the primary intention of improving system reliability and availability, have been under development since the initial installation of the HVCM units. This paper will examine HVCM reliability studies, reliability operational data, and modifications and improvements performed to increase the overall system availability. We will also discuss system enhancements aimed at improving the ease of operation and providing for additional equipment protection features.

WPAT070 500 MHz Coaxial Transition Between the ELETTRA Input Coupler and the Transmission Waveguide vacuum, injection, storage-ring, insertion 3810
  • C. Pasotti, A. Fabris, M. Svandrlik
    ELETTRA, Basovizza, Trieste
  The investigations have shown that the 500 MHz ELETTRA input power coupler can safely sustain more than 150 KW. The critical component limiting the increase of the trasmitted RF power is the connection element between the input power coupler and the transmission line. An optimized design has been studied to overcome this limit. During the optimization process, the entire RF chain (input power coupler, connection element and transition to the standard waveguide WR1800) has been verified. The analysis has been carried out to check the performances of the whole lay-out in terms of efficiency of transmitted power and sensitivity to any signal coming from the cavity ( HOMs included). A prototype with an improved cooling system has been realized and tested.  
WPAT076 Resonant High Power Combiners insertion, impedance, radio-frequency, synchrotron 3970
  • M.L. Langlois, J.P. Buge, G. Peillex-Delphe
    TED, Vélizy Cedex
  Particle accelerators need radio frequency sources. Above 300 MHz, the amplifiers mostly used high power klystrons developed for this sole purpose. As for military equipment, users are drawn to buy "off the shelf" components rather than dedicated devices. IOTs have replaced most klystrons in TV transmitters and find their way in particle accelerators. They are less bulky, easier to replace, more efficient at reduced power. They are also far less powerful. What is the benefit of very compact sources if huge 3 dB couplers are needed to combine the power? To alleviate this drawback, we investigated a resonant combiner, operating in TM010 mode, able to combine 3 to 5 IOTs. Our IOTs being able to deliver 80 kW C.W. apiece, combined power would reach 400 kW minus the minor insertion loss. Values for matching and insertion loss are given. The behavior of the system in case of IOT failure is analyzed.  
WPAT078 A High Power RF Power Supply for High Energy Physics Applications power-supply, radio-frequency 4018
  • M.J. Bland, J. Clare, P. W. Wheeler
    University of Nottingham, Nottingham
  • J.S. Przybyla
    EEV, Chelmsford, Essex
  Funding: Particle Physics and Astronomy Research Council (PPARC).

Accelerators used for experiments in high-energy physics require very high power radio frequency sources to provide the energy needed to accelerate the particles. The RF power needs to be stable and predictable such that any variation in the supplied RF power has a limited and acceptable impact on the accelerated beam quality. The output load specifications for high voltage DC power systems are becoming increasingly more demanding. In addition, the impact of such systems on the electricity source is becoming more tightly regulated through power quality directives. These regulations set limits, for example, on the allowable individual harmonic current amplitudes and on "flicker" caused by transient load demands - the latter is particularly important for "long-pulse" modulators. The requirements above have to be met while still providing higher reliability to a higher specification at lower cost. A situation has now been reached where modulators based on existing approaches cannot meet these specifications and stay within acceptable cost and size limits. This demands that new approaches be taken to provide the power supplies needed for such applications. The research proposed here addresses this need.

WPAT084 A NEW DESIGN FOR A SUPER-CONDUCTING CAVITY INPUT COUPLER coupling, electron, vacuum, 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.

WPAT086 Superconducting RF Cavity Frequency and Field Distribution Sensitivity Simulation simulation, SNS, radiation, superconducting-RF 4194
  • S. An
    ORNL, Oak Ridge, Tennessee
  Funding: Under contract DE-AC05-00OR22725 for the U.S. Department of Energy.

Frequency and electromagnetic field distribution sensitivity of a superconducting RF (SRF) cavity due to cavity’s small deformation are the fundamental phyical paramethers in cavity and tuner design. At low temperature, the frequency sensitivity can be obtained by measuring prototype cavity, but it is not easy to test the filed distribution sensitivity. This paper presents and describes a simulation method combining ANSYS and SUPERFISH to calculate the cavity frequency and field distribution variation due to cavity’s small deformation caused by mechanical force, radiation force, thermal expansion etc.. As an example, the simulation results of the frequency and field flatness sensitivity on the SNS cavities were confirmed by their test results.


WPAT089 Test Bed for Superconducting Materials coupling, superconducting-RF, superconductivity, vacuum 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.

WPAT095 Low-Loss Ferroelectric for Accelerator Application coupling, vacuum, 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.

WOAB004 Applying Frequency Map Analysis to the Australian Synchrotron Storage Ring sextupole, synchrotron, quadrupole, dynamic-aperture 407
  • Y.E. Tan, M.J. Boland, G. LeBlanc
    ASP, Clayton, Victoria
  The technique of frequency map analysis has been applied to study the transverse dynamic aperture of the Australian Synchrotron Storage Ring. The results have been used to set the strengths of sextupoles to optimise the dynamic aperture. The effects of the allowed harmonics in the quadrupoles and dipole edge effects are discussed.  
WOAC007 Beam-Based Nonlinear Optics Corrections in Colliders sextupole, octupole, coupling, multipole 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 coupling, 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.

ROAA002 CESR-c: Performance of a Wiggler-Dominated Storage Ring wiggler, luminosity, sextupole, betatron 189
  • A. Temnykh
    Cornell University, Department of Physics, Ithaca, New York
  Funding: Work supported by the U.S. National Science Foundation.

CESR-c operates now as a Wiggler-Dominated Storage Ring extending the lowest operating energy to 1.5GeV/beam. To improve beam stability at low energy, 12 super-ferric wiggler magnets with total length of 15m and 2.1T maximum field were installed in the ring. They cause ~90% of total beam radiation lost and increase radiation damping rate by factor 10 from ~3 to 40 Hz. However, the field of the wiggler magnets not only initiates the radiation, but potentially affects beam dynamics. The latter was an issue of a great concern from the planning the CESR-c project. In this paper we describe general performance of CESR-c and report the results of an experimental study on some aspects of beam dynamics. Comparisons are made between the experimental data and the model prediction. We find that all parameters, which are critically dependent on wigglers, such as beam properties and ring nonlinearity, are in good agreement with those calculated from the model. This validates the ring and wiggler models and justifies our design and production technique of the magnets. The experience we obtained will be extremely useful in future work on linear collider damping rings.

ROAA005 Recent Innovations in Muon Beam Cooling and Prospects for Muon Colliders emittance, simulation, collider, beam-cooling 419
  • R.P. Johnson, M. Alsharo'a, P.M. Hanlet, R. E. Hartline, M. Kuchnir, K. Paul, T.J. Roberts
    Muons, Inc, Batavia
  • C.M. Ankenbrandt, E. Barzi, L. DelFrate, I.G. Gonin, A. Moretti, D.V. Neuffer, M. Popovic, G. Romanov, D. Turrioni, V. Yarba
    Fermilab, Batavia, Illinois
  • K. Beard, S.A. Bogacz, Y.S. Derbenev
    Jefferson Lab, Newport News, Virginia
  • D.M. Kaplan, K. Yonehara
    Illinois Institute of Technology, Chicago, Illinois
  Funding: This work was supported in part by DOE SBIR/STTR grants DE-FG02-02ER86145, 03ER83722, 04ER84015, 04ER86191, and 04ER84016.

A six-dimensional(6D)cooling channel based on helical magnets surrounding RF cavities filled with dense hydrogen gas* is used to achieve the small transverse emittances demanded by a high-luminosity muon collider. This helical cooling channel**(HCC) has solenoidal, helical dipole, and helical quadrupole magnetic fields to generate emittance exchange. Simulations verify the analytic predictions and have shown a 6D emittance reduction of over 3 orders of magnitude in a 100 m HCC segment. Using three such sequential HCC segments, where the RF frequencies are increased and transverse dimensions reduced as the beams become cooler, implies a 6D emittance reduction of almost six orders of magnitude. After this, two new post-cooling ideas can be employed to reduce transverse emittances to one or two mm-mr, which allows high luminosity with fewer muons than previously imagined. In this report we discuss the status of and the plans for the HCC simulation and engineering efforts. We also describe the new post-cooling ideas and comment on the prospects for a Higgs factory or energy frontier muon collider using existing laboratory infrastructure.

*R. P. Johnson et al. LINAC2004, www.muonsinc.com/TU203.pdf. **Y. Derbenev and R.P. Johnson, Submitted to PRSTAB, http://www-mucool.fnal.gov/mcnotes/public/pdf/muc0284/muc0284.pdf.

RPAE016 Smith-Purcell Radiation from a Charge Moving Above a Finite-Length Grating radiation, electron, coupling, 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.

RPAE037 Operation with a Low Emittance Optics at ANKA optics, emittance, injection, storage-ring 2467
  • E. Huttel, A. Ben Kalefa, I. Birkel, A.-S. Müller, P. Wesolowski
    FZK, Karlsruhe
  • M. Giovannozzi
    CERN, Geneva
  • M. Pont, F. Pérez
    CELLS, Bellaterra (Cerdanyola del Vallès)
  ANKA is a synchrotron light source operating in an energy range from 0.5 to 2.5 GeV. The electron storage ring at ANKA is designed as a variation of an eightfold Double Bend Achromat structure. Since its commissioning the facility has been operated with zero dispersion in the long straight sections resulting in an emittance of about 100 nmrad. Since mid 2004 ANKA is operated with dispersion distributed over the complete ring thus reducing the emittance to 40 nmrad. In the course of the re-design of the storage ring optics a compensation of higher order field components leads to a visibly increased momentum acceptance. Optics calculations and measurements as well as operational experience will be discussed.  
RPAP020 Fixed Field Alternating Gradient Accelerators (FFAG) for Fast Hadron Cancer Therapy proton, ion, acceleration, cyclotron 1667
  • E. Keil
    CERN, Geneva
  • A. Sessler
    LBNL, Berkeley, California
  • D. Trbojevic
    BNL, Upton, Long Island, New York
  Funding: * AMS supported by the U.S. Department of Energy under Contract No. DE-AC03-76SF0009

Cancer accelerator therapy continues to be ever more prevalent with new facilities being constructed at a rapid rate. Some of these facilities are synchrotrons, but many are cyclotrons and, of these, a number are FFAG cyclotrons. The therapy method of "spot scanning” requires many pulses per second (typically 200 Hz), which can be accomplished with a cyclotron (in contrast with a synchrotron). We briefly review commercial scaling FFAG machines and then discuss recent work on non-scaling FFAGs, which may offer the possibility of reduced physical aperture and a large dynamic aperture. However, a variation of tune with energy implies the crossing of resonances during the acceleration process. A design can be developed such as to avoid intrinsic resonances, although imperfection resonances must still be crossed. Parameters of two machines are presented; a 250 MeV proton therapy accelerator and a 400 MeV carbon therapy machine.

RPAT012 A Hardware Transverse Beam Frequency Response Simulator synchrotron, feedback, betatron 1269
  • J. Ning, C.-Y. Tan
    Fermilab, Batavia, Illinois
  Funding: Fermi National Accelerator Lab.

We build an electronical instrument to get the frequency response close to the pattern of transverse beam frequency response. The method is to apply 1)a time delay circuit with ADC, FIFO RAM and DAC; 2)a phase shift circuit which is an all pass filter with adjustable phase shift in the frequency range of 25kHz to 30kHz; in a feedback loop of 3)a commutating filter which is a high Q band pass filter. We can dynamically adjust the center frequency, the side band distance during the testing. With this instrument, some beam instruments can be tested without using the real beam.

RPAT049 Numerical Studies on the Electro-Optic Sampling of Relativistic Electron Bunches laser, electron, lattice, simulation 3070
  • S. Casalbuoni, H. Schlarb, B. Schmidt, B. Steffen
    DESY, Hamburg
  • P. Schmüser, A. Winter
    Uni HH, Hamburg
  Ultraviolet and X ray free electron lasers require sub-picosecond electron bunches of high charge density. Electro-optic sampling (EOS) is a suitable diagnostic tool for resolving the time structure of these ultrashort bunches. The transient electric field of the relativistic bunch induces a polarization anisotropy in a nonlinear crystal which is sampled by femtosecond laser pulses. In this paper, the EOS process is studied in detailed numerical calculations. The THz and the laser pulses are treated as wave packets which are propagated through the zinc telluride resp. gallium phosphide crystals. The effects of signal broadening and distortion are taken into account. The time resolution is limited by the lowest lattice oscillation frequency which amounts to 5.3 THz in ZnTe and 11 THz in GaP. The shortest bunch length which can be resolved with moderate distortion is about 200 fs (FWHM) in ZnTe and 100 fs in GaP.  
RPAT094 Femtosecond Synchronisation of Ultrashort Pulse Lasers to a Microwave RF Clock laser, linac, monitoring, feedback 4299
  • A. Winter
    Uni HH, Hamburg
  • N. Ignashin, A. Simonov, S. Sytov
    IHEP Protvino, Protvino, Moscow Region
  • E.-A. Knabbe, S. Simrock, B. Steffen
    DESY, Hamburg
  A precise synchronization between the laser repetition rate and the linac-RF is mandatory for electro-optic sampling or pump-probe experiments. The level of stability is usually determined by measuring of the spectral noise power density of the feedback signal when the system is locked. However, an independent measurement is needed to confirm this. In this paper, we present an approach exploiting electronic techniques to synchronize a TiSa laser to the RF of the DESY VUVFEL with sub-50 fs stability. The remaining time jitter is measured by an RF monitoring system independent of the locking PLL.  
RPPE014 Temperature Regulation of the Accelerating Section in CANDLE Linac feedback, linac, simulation, radio-frequency 1416
  • S. Tunyan, G.A. Amatuni, B. Grigoryan
    CANDLE, Yerevan
  The temperature of the CANDLE S-Band Linac high-power RF components will be regulated by stand-alone closed loop (SACL) water system. The RF components are made of oxygen-free high conductivity copper and respond quickly to temperature changes. Temperature stabilization better than ± 0.1 C is required to achieve a good RF phase and energy stability. The temperature regulation and control philosophy along with the simulation results are discussed.  
RPPE057 Resistive Wall Wakefield in the LCLS Undulator undulator, impedance, electron, simulation 3390
  • K.L.F. Bane, G.V. Stupakov
    SLAC, Menlo Park, California
  Funding: Work supported by the U.S. Department of Energy, contract DE-AC03-76SF00515.

In the Linac Coherent Light Source (LCLS), a short, intense bunch (rms length 20 microns, bunch charge 1 nC) will pass through a small, long undulator beam pipe (radius 2.5 mm, length 130 m). The wakefields in the undulator, particularly the resistive wall wake of the beam pipe, will induce an energy variation along the bunch, a variation that needs to be kept to within a few times the Pierce parameter for all beam particles to continue to lase. Earlier calculations included the short-range resistive wall wake, but did not include the frequency dependence of conductivity (ac conductivity) of the beam pipe walls. We show that for copper and for the LCLS bunch structure, including the ac conductivity results in a very large effect. We show that the effect can be ameliorated by choosing aluminum and also by taking a flat, rather than round, beam pipe chamber (if the vertical aperture is fixed). The effect of the (high frequency) anomalous skin effect is also considered.

RPPE059 Measurements of Epsilon and Mu of Lossy Materials for the Cryogenic HOM Load damping, coupling, 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.

RPPE060 Overview of SNS Cryomodule Performance SNS, vacuum, linac, klystron 3496
  • M. A. Drury, E. Daly, G.K. Davis, J.R. Delayen, C. Grenoble, W.R. Hicks, K. King, T. Plawski, T. Powers, J.P. Preble, H. Wang, M. Wiseman
    Jefferson Lab, Newport News, Virginia
  Funding: Supported by U.S. DOE Contract Nos. DE-AC05-84ER40150.

Thomas Jefferson National Accelerating Facility (Jefferson Lab) has completed production of 24 Superconducting Radio Frequency (SRF) cryomodules for the Spallation Neutron Source (SNS) superconducting linac. This includes one medium-beta (0.61) prototype, eleven medium-beta and twelve high-beta (0.81) production cryomodules. Ten medium-beta cryomodules as well as two high beta cryomodules have undergone complete operational performance testing in the Cryomodule Test Facility at Jefferson Lab. The set of tests includes measurements of maximum gradient, unloaded Q (Q0), microphonics, and response to Lorentz forces. The Qext’s of the various couplers are measured and the behavior of the higher order mode couplers is examined. The mechanical and piezo tuners are also characterized. The results of these performance tests will be discussed in this paper.

RPPP038 Electron-Cloud Effects in Transport Lines of a Normal Conducting Linear Collider positron, electron, focusing, vacuum 2527
  • J. Wu, M.T.F. Pivi, T.O. Raubenheimer, A. Seryi
    SLAC, Menlo Park, California
  Funding: Work is supported by the U.S. Department of Energy under contract DE-AC02-76SF00515.

In the transport lines of a normal conducting linear collider, the long positron bunch train can generate an electron cloud which can then amplify intra-train offsets. This is a transient effect which is similar to but different from the electron-cloud driven coupled bunch instabilities in a positron storage ring. In this paper, we study this phenomenon both analytically and via numerical simulation. Some criterion on the critical cloud density with respect to given collider parameters is discussed.

RPPT014 Design and Measurements of an X-Band Accelerating Cavity for SPARC coupling, 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.  
RPPT039 Stabilized Optical Fiber Links for the XFEL laser, feedback, polarization, electron 2589
  • A. Winter
    Uni HH, Hamburg
  • J. Chen, F J. Grawert, F.O. Ilday, F.X. Kaertner, J. Kim
    MIT, Cambridge, Massachusetts
  • H. Schlarb, B. Schmidt
    DESY, Hamburg
  The timing synchronization scheme for the European X-Ray free electron laser facility (XFEL) is based on the generation and distribution of sub-picosecond laser pulses with actively stabilized repetition rate which are used to synchronize local RF oscillators. An integral part of the scheme is the distribution of the optical pulse stream to parts of the facility via optical fiber links. The optical path length of the fiber has to be stabilized against short-term and long-term timing jitter due to environmental effects, such as temperature drifts and acoustic vibrations, to better than 10 fs for distances ranging from tens of meters to several kilometers. In this paper, we present first experimental results for signal transmission through a km-long fiber link with femtosecond stability.  
RPPT051 Electron Model of Linear-Field FFAG acceleration, electron, quadrupole, extraction 3173
  • S.R. Koscielniak
    TRIUMF, Vancouver
  • C. Johnstone
    Fermilab, Batavia, Illinois
  Funding: TRIUMF receives federal funding via a contribution agreement through the National Research Council of Canada.

A fixed-field alternating-gradient accelerator (FFAG) that employs only linear-field elements ushers in a new regime in accelerator design and dynamics. The linear-field machine has the ability to compact an unprecedented range in momenta within a small component aperture. With a tune variation which results from the natural chromaticity, the beam crosses many strong, uncorrec-table, betatron resonances during acceleration. Further, relativistic particles in this machine exhibit a quasi-parabolic time-of-flight that cannot be addressed with a fixed-frequency rf system. This leads to a new concept of bucketless acceleration within a rotation manifold. With a large energy jump per cell, there is possibly strong synchro-betatron coupling. A few-MeV electron model has been proposed to demonstrate the feasibility of these untested acceleration features and to investigate them at length under a wide range of operating conditions. This paper presents a lattice optimized for a 1.3 GHz rf, initial technology choices for the machine, and describes the range of experiments needed to characterize beam dynamics along with proposed instrumentation.

RPPT052 Analysis of Rapid Betatron Resonance Crossing betatron, acceleration, lattice, linac 3206
  • S.R. Koscielniak, A. Baartman
    TRIUMF, Vancouver
  Funding: TRIUMF receives federal funding via a contribution agreement through the National Research Council of Canada.

The reduction of transverse and longitudinal cooling requirements, the increased number of beam circulations, and the reduce cost, as compared to RLAs, are arguments to adopt the linear-field FFAG as the acceleration stage of a Neutrino Factory. Because of the large range of central momenta, pm 50% delta p/p, and negative uncorrected chromaticity, the non-scaling FFAG will cross many integer and half-integer betatron resonances during the 10-20 turns acceleration. There is the expectation that if driving terms are small enough and crossing is fast enough, then there is insufficient time for the betatron amplitudes to grow. The conventional theory of resonance crossing is applied to slow acceleration, over 100s or 1000s of turns. This paper examines whether the rapid parameter changes encountered in the multi-GeV FFAGs, or few-MeV electron model, are compatible with simple theory.

FOAC003 New Concepts in FFAG Design for Secondary Beam Facilities and Other Applications proton, cyclotron, ion, acceleration 261
  • M.K. Craddock
    UBC & TRIUMF, Vancouver, British Columbia
  Fixed Field Alternating Gradient accelerators offer much higher acceptances and repetition rates - and therefore higher beam intensities - than synchrotrons, at the cost of more complicated magnet and rf cavity designs. Perhaps because of the difficulty and expense anticipated, early studies never progressed beyond the stage of successful electron models, but in recent years, with improvements in magnet and rf design technology, FFAGs have become the focus of renewed attention. Two proton machines have now been built, and three more, plus a muon phase rotator, are under construction. In addition, more than 20 designs are under study for the acceleration of protons, heavy ions, electrons and muons, with applications as diverse as treating cancer, irradiating materials, driving subcritical reactors, boosting high-energy proton intensity, and producing neutrinos. Moreover, it has become apparent that FFAG designs need not be restricted to the traditional 'scaling' approach, in which the orbit shape, optics and tunes are kept fixed. Dropping this restriction has revealed a range of interesting new design possibilities. This paper will review the various approaches being taken.  
FPAE005 Characteristics of Injected Beam at HIMAC Synchrotron injection, simulation, survey, synchrotron 952
  • T.H. Uesugi, T. Furukawa, K. Noda, S. Shibuya
    NIRS, Chiba-shi
  At the HIMAC synchrotron, we have carried out the tune survey with the lifetime measurement in order to obtain the high intensity. Under the relatively high intensity, it was observed that a part of the circulating beam was lost due to the coherent oscillation in both the horizontal and the vertical direction. Taking account of the tune shift and spreads, the working point was optimized so as to avoid resonance line. We will describe the experimental result.  
FPAE006 Optimization of AGS Polarized Proton Operation with the Warm Helical Snake proton, extraction, dipole, simulation 1003
  • J. Takano, M. Okamura
    RIKEN, Saitama
  • L. Ahrens, M. Bai, K.A. Brown, C.J. Gardner, J. Glenn, H. Huang, A.U. Luccio, W.W. MacKay, T. Roser, S. Tepikian, N. Tsoupas
    BNL, Upton, Long Island, New York
  • T. Hattori
    RLNR, Tokyo
  Funding: US DOE and RIKEN Japan.

A normal conducting helical dipole partial Siberian snake (Warm Snake) has been installed in the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory (BNL) for overcoming all of imperfection depolarizing resonances and reducing the transverse coupling resonances caused by the solenoidal Siberian snake which had been operated in AGS before the last polarized run. The polarized proton beam has been accelerated successfully with the warm snake and the polarization at extraction of the AGS was increased to 50% as opposed to 40% with the solenoidal snake. The magnetic field and beam trajectory in the warm snake was calculated by using the OPERA-3D/TOSCA software. We present optimization of the warm snake with beam during RUN5.

FPAE014 Acceleration of Polarized Protons in the AGS with Two Helical Partial Snakes polarization, extraction, injection, dipole 1404
  • H. Huang, L. Ahrens, M. Bai, A. Bravar, K.A. Brown, G. Bunce, E.D. Courant, C.J. Gardner, J. Glenn, R.C. Gupta, A.U. Luccio, W.W. MacKay, V. Ptitsyn, T. Roser, S. Tepikian, N. Tsoupas, E. Willen, A. Zelenski, K. Zeno
    BNL, Upton, Long Island, New York
  • F. Lin
    IUCF, Bloomington, Indiana
  • M. Okamura
    RIKEN/RARF/CC, Saitama
  • J. Takano
    RIKEN, Saitama
  • D.G. Underwood
    ANL, Argonne, Illinois
  • J. Wood
    UCLA, Los Angeles, California
  Funding: Work supported by U.S. DOE and RIKEN of Japan.

The RHIC spin program requires 2*1011 proton/bunch with 70% polarization. As the injector to RHIC, AGS is the bottleneck for preserving polarization: there is not enough space in the ring to install a full snake to overcome the numerous depolarizing resonances. An ac dipole and a partial Siberian snake have been used to preserve beam polarization in the past. The correction with this scheme is not 100% since not all depolarizing resonances can be overcome. Recently, two helical snakes with double pitch design have been built and installed in the AGS. With careful setup of optics at injection and along the ramp, this combination can eliminate all depolarizing resonances encountered during acceleration. This paper presents the accelerator setup and preliminary results.

FPAE047 Test Scheme Setup for the PEFP 20MeV DTL beam-losses, quadrupole, proton, klystron 2965
  • H.-S. Kim, Y.-S. Cho, Y.-H. Kim, H.-J. Kwon, K.T. Seol
    KAERI, Daejon
  • Y.-S. Hwang
    SNU, Seoul
  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 is under development for the Proton Engineering Frontier Project (PEFP). The goal of the first stage of the project is to develop a 20MeV accelerator and the initial test of the 20MeV accelerator will be made. The DTL of 20 MeV accelerator consists of four tanks and will be driven with single klystron, which gives rise to some unique problems with regard to the way of independent resonance control for each tank. Some changes made in the LLRF for reducing phase or amplitude error of cavities affect all of four tanks simultaneously, for which it is not possible to use LLRF for individual control of phase and amplitude of each tank. For independent control of each tank, we are going to use the temperature control of the drift tubes as a frequency tuner. During the initial test of the DTL, the phase of each tank will be synchronized with the first tank phase, and beam based test will be performed as if all of tanks were single unit. The detailed description of the test scheme and the analysis results will be given in this paper.

FPAE058 Spallation Neutron Source Superconducting Linac Commissioning Algorithms linac, SNS, simulation, Spallation-Neutron-Source 3423
  • S. Henderson, I.E. Campisi, J. Galambos, D.-O. Jeon, Y. Zhang
    ORNL, Oak Ridge, Tennessee
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos and Oak Ridge.

We describe the techniques which will be employed for establishing RF and quadrupole setpoints in the SNS superconducting linac. The longitudinal tuneup will be accomplished using phase-scan methods, as well as a technique that makes use of the beam induced field in the unpowered cavity.* The scheme for managing the RF and quadrupole setpoints to achieve a given energy profile will be described.

*L. Young, Proc. PAC 2001, p. 572.

FPAE062 Beam Parameters of a Two-Sectional Electron Linac with the Injector Based on a Resonance System with Evanescent Oscillations linac, simulation, emittance, electron 3567
  • V.V. Mytrochenko, M.I. Ayzatskiy, V.N. Boriskin, A. Dovbnya, I.V. Khodak, V.A. Kushnir, A. Opanasenko, S.A. Perezhogin, A.N. Savchenko, D.L. Stepin, V.I. Tatanov, Z.V. Zhiglo
    NSC/KIPT, Kharkov
  The S-band electron linac has been designed at NSC KIPT to cover an energy range from 30 to about of 100 MeV. The linac consists of a couple of the four-meter long piecewise homogeneous accelerating sections. Each section is supplied with RF power from a separate klystron. The peculiarity of the linac is using of the injector based on evanescent oscillations. The report presents both simulation results of self-consistent particle dynamics in the linac and results of measurement of beam parameters.  
FPAP012 The Effect of Inhomogeneous Magnetic Field on Budker-Chirikov Instability electron, ion, simulation, betatron
  • Y. Golub
    MRTI RAS, Moscow
  The two-beams electron - ion system consists of a nonrelativistic ion beam propagating co-axially with a high-current relativistic electron beam in a longitudinal inhomogeneous magnetic field. The effect of the longitudinal inhomogeneous magnetic field on instability Budker-Chirikov (BCI) in the system is investigated by the method of a numerical simulation in terms of the kinetic description of both beams. The investigations are development of investigations in*,**. Is shown, when the inhomogeneity magnetic field results in the decreasing of an increment of instability Budker-Chirikov and the increasing of length of propagation of a electron beam. Also is shown, when take place the opposite result.

*Yu.Ya. Golub, N.E.Rozanov, Nuclear Instruments and Methods in Physics Research, A358 (1995) 479. **Yu.Ya. Golub, Proceedings of EPAC 2002, Paris, France, p. 1497.

FPAP018 Luminosity Loss Due to Beam Distortion and the Beam-Beam Instability luminosity, simulation, emittance, electron 1586
  • J. Wu, A. Chao, T.O. Raubenheimer, A. Seryi
    SLAC, Menlo Park, California
  • C.K. Sramek
    Rice University, Houston, Texas
  Funding: Work is supported by the U.S. Department of Energy under contract DE-AC02-76SF00515.

In a linear collider, sources of emittance dilution such as transverse wakefields or dispersive errors will couple the vertical phase space to the longitudinal position within the beam (the so-called ‘banana effect'). When the Intersection Point (IP) disruption parameter is large, these beam distortions will be amplified by a single bunch kink instability which will lead to luminosity loss. We study this phenomena both analytically using linear theory and via numerical simulation. In particular, we examine the dependence of the luminosity loss on the wavelength of the beam distortions and the disruption parameter. This analysis may prove useful when optimizing the vertical disruption parameter for luminosity operation with given beam distortions.

FPAP034 Space-Charge Transport Limits in Periodic Channels lattice, focusing, space-charge, simulation 2348
  • S.M. Lund
    LLNL, Livermore, California
  • S. R. Chawla
    UCB, Berkeley, California
  Funding: Research performed under the auspices of the US DOE by the University of California at LLNL and LBNL under contract Nos. W-7405-Eng-48 and DE-AC03-76SF00098.

It has been observed in both experiment and particle in cell simulations that space-charge-dominated beams suffer strong emittance growth in alternating gradient quadrupole transport channels when the undepressed phase advance σ0 increases beyond about 80 degrees per lattice period. Transport systems have long been designed to respect this phase advance limit but no theory has been proposed to date to explain the the cause of the limit. Here we propose a mechanism to parametrically explain the transport limit as being due to classes of halo particle orbits moving close to the beam edge in phase-space when σ0 increases beyond 80 degrees. A finite beam edge and/or perturbation acting on an edge particle can then act to move edge particles to large amplitude and lead to large increases in beam phase space area, lost particles, and degraded transport. A core particle model for a uniform density elliptical beam in a periodic focusing lattice was written and is applied to parametrically analyze this process for both periodic alternating gradient quadrupole and solenoidal transport lattices. Self-consistent particle in cell simulations are also carried out to support results.

FPAT011 Fast Automated Decoupling at RHIC coupling, quadrupole, monitoring, 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.

FPAT035 Transverse Beam Instability in a Compact Dielectric Wall Induction Accelerator impedance, induction, acceleration, simulation 2378
  • Y.-J. Chen, J.F. McCarrick, S.D. Nelson
    LLNL, Livermore, California
  Funding: This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Using the dielectric wall accelerator technology, we are developing of a compact induction accelerator system primarily intended for pulsed radiography. Unlike the typical induction accelerator cell that is long comparing with its accelerating gap width, the proposed dielectric wall induction accelerator cell is short and its accelerating gap width is comparable with the cell length. In this geometry, the rf modes may be coupled from one cell to the next. We will present recent results of rf modeling of the cells and prediction of transverse beam instability on a 2-kA, 8-MeV beam.

FPAT056 RF Control System Upgrade at CAMD diagnostics, impedance, klystron, monitoring 3339
  • V.P. Suller
    CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • M.G. Fedurin, P. Jines, D.J. Launey
    LSU/CAMD, Baton Rouge, Louisiana
  A description is given of the new control system for the RF system of the CAMD light source. The new design being implemented brings all RF signals into the data acquisition system via a modular, custom made, RF detector and renders the amplitude and tune control loops in the VME computer. On line calculations ensure monitoring of proper operation and display the information to the user in an efficient way. In addition, an advanced load impedance monitoring diagnostic has been implemented, being displayed as a Smith Chart, which is based on the system used at the SRS in Daresbury, England.  
FPAT068 Spallation Neutron Source Drift Tube Linac Resonance Control Cooling System Modeling feedback, linac, SNS, Spallation-Neutron-Source 3754
  • J.Y. Tang, A.V. Aleksandrov, M.M. Champion, P.E. Gibson, J.P. Schubert
    ORNL, Oak Ridge, Tennessee
  • A. Feschenko, Y. Kiselev, A.S. Kovalishin, L.V. Kravchuk, A.I. Kvasha
    RAS/INR, Moscow
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.

The Resonance Control Cooling System (RCCS) for the warm linac of the Spallation Neutron Source was designed by Los Alamos National Laboratory. The primary design focus was on water cooling of individual component contributions. The sizing the RCCS water skid was accomplished by means of a specially created SINDA/FLUINT model tailored to these system requirements. A new model was developed in Matlab Simulink and incorporates actual operational values and control valve interactions. Included is the dependence of RF input power on system operation, cavity detuning values during transients, time delays that result from water flows through the heat exchanger, the dynamic process of water warm-up in the cooling system due to dissipated RF power on the cavity surface, differing contributions on the cavity detuning due to drift tube and wall heating, and a dynamic model of the heat exchanger with characteristics in close agreement to the real unit. Because of the Matlab Simulink model, investigation of a wide range of operating issues during both transient and steady state operation is now possible. Results of the DTL RCCS modeling are presented

FOAA003 HOM Effects in Vacuum System with Short Bunches vacuum, positron, luminosity, synchrotron 289
  • A. Novokhatski
    SLAC, Menlo Park, California
  Funding: Work supported by Department of Energy contract DE–AC02–76SF00515.

High luminosity in electron-positron factories requires high beam currents of very short bunches. SLAC PEP-II and KEKB B-factories are progressively increasing currents and gaining more and more luminosity. Because of this the interaction of high currents and vacuum chamber elements becomes more important for the operation of the rings. High Order Modes (HOM) excited by short intense bunches propagate along the vacuum chamber, penetrating and dissipating inside vital vacuum elements like shielded bellows, vacuum valves and vacuum pumps. As a result these elements can heat up or have temperature oscillations. Often HOM heating has a resonance character. HOM heating of vacuum pumps can lead to vacuum pressure increases. High frequency modes excited by short bunches “check” the quality of the vacuum chamber by detecting small gaps, weak RF screens or weak feed-through. At these high currents even smooth tapers and smooth collimators become a source of HOM production. We will discuss the physical nature of these very interesting HOM effects.

FOAA006 Digital Low-Level RF Controls for Future Superconducting Linear Colliders linac, feedback, klystron, collider 515
  • S. Simrock
    DESY, Hamburg
  The requirements for RF Control Systems of Superconducting Linear Colliders are not only defined in terms of the quality of field control but also with respect to operability, availability, and maintainability of the RF System, and the interfaces to other subsystems. The field control of the vector-sum of many cavities driven by one klystron in pulsed mode at high gradients is a challenging task since severe Lorentz force detuning, microphonics and beam induced field errors must be suppressed by several orders of magnitude. This is accomplished by a combination of local and global feedback and feedforward control. Sensors monitor individual cavity probe signals, and forward and reflected wave as well as the beam properties including beam energy and phase while actuators control the incident wave of the klystron and individual cavity resonance frequencies. The operability of a large llrf system requires a high degree of automation while the high availability requires robust algorithms, redundancy, and extremely reliable hardware. The maintenance of the llrf demands sophisticated on-line diagnostics for the llrf subsystems to minimize downtime.  
FOAD001 Frozen Beams storage-ring, lattice, ion, laser 4
  • H. Okamoto
    HU/AdSM, Higashi-Hiroshima
  In general, the temperature of a charged particle beam traveling in an accelerator is very high. Seen from the rest frame of the beam, individual particles randomly oscillate about the reference orbit at high speed. This internal kinetic energy can, however, be removed by introducing dissipative interactions into the system. As a dissipative process advances, the beam becomes denser in phase space or, in other words, the emittance is more diminished. Ideally, it is possible to reach a "zero-emittance" state where the beam is Coulomb crystallized. The space-charge repulsion of a crystalline beam just balances the external restoring force provided by artificial electromagnetic elements. In this talk, general discussion is made of coasting and bunched crystalline beams circulating in a storage ring. Results of molecular dynamics simulations are presented to demonstrate the dynamic nature of various crystalline states. A possible method to approach such an ultimate state of matter is also discussed.