• P. Bauer, G. Annala, M.A. Martens, V.D. Shiltsev, G. Velev
  Fermilab, Batavia, Illinois
• L. Bottura, N.J. Sammut
  CERN, Geneva

• Y. Luo, P. Cameron, A. Della Penna, W. Fischer, J.S. Laster, A. Marusic, F.C. Pilat, T. Roser, D. Trbojevic
  BNL, Upton, Long Island, New York

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

• M.A. Martens, J. Annala, P. Bauer, V.D. Shiltsev, G. Velev
  Fermilab, Batavia, Illinois

• B. Goddard, H. Burkhardt, V. Kain, T. Risselada
  CERN, Geneva

• 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

• M. Takao, M. Masaki, J. Schimizu, K. Soutome, S. Takano, H. Tanaka
  JASRI/SPring-8, Hyogo

• M. Xiao, Y. Alexahin, D.E. Johnson, M.-J. Yang
  Fermilab, Batavia, Illinois

• Y.T. Yan, Y. Cai, F.-J. Decker, S. Ecklund, J. Irwin, J. Seeman, M.K. Sullivan, J.L. Turner, U. Wienands
  SLAC, Menlo Park, California

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

• Y.T. Yan, Y. Cai
  SLAC, Menlo Park, California

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.

• R. Calaga, S. Abeytunge, M. Bai, W. Fischer
  BNL, Upton, Long Island, New York
• F. Franchi
  GSI, Darmstadt
• R. Tomas
  CELLS, Bellaterra (Cerdanyola del Vallès)

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

• V. Sajaev, L. Emery
  ANL, Argonne, Illinois

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%.

• V. Sajaev
  ANL, Argonne, Illinois
• V. Lebedev, V. Nagaslaev, A. Valishev
  Fermilab, Batavia, Illinois

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

• W. Wan, W.E. Byrne, H. Nishimura, G.J. Portmann, D. Robin, F. Sannibale, A. Zholents
  LBNL, Berkeley, California

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

• M.-J. Yang
  Fermilab, Batavia, Illinois

• M.-J. Yang, M. Xiao
  Fermilab, Batavia, Illinois

• F. Nolden, B.  Franzke, C. Peschke
  GSI, Darmstadt
• M.C. Balk, R. Schuhmann, T. Weiland
  TEMF, Darmstadt
• F. Caspers, L. Thorndahl
  CERN, Geneva

• W.K. Lau, L.-H. Chang, C.W. Chen, H.Y. Chen, P.J. Chou, K.-T. Hsu, S.Y. Hsu, T.-T. Yang
  NSRRC, Hsinchu
• M. Dehler
  PSI, Villigen

• J. Wu, A. Chao, B. Nash
  SLAC, Menlo Park, California

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.

• B. Doliwa, H. De Gersem, T. Weiland
  TEMF, Darmstadt

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

• G. Huang, W.-H. Huang, S. Zheng
  Tsinghua University, Beijing
• J.Q. Wang, D.M. Zhou
  IHEP Beijing, Beijing

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

• N. Mityanina
  BINP SB RAS, Novosibirsk

• N.J. Sammut, L. Bottura
  CERN, Geneva
• J. Micallef
  University of Malta, Faculty of Engineering, Msida

• D.J. Harding, P. Bauer, J.N. Blowers, J. DiMarco, H.D. Glass, R. Hanft, J.A. John, W.F. Robotham, M. Tartaglia, J. Tompkins, G. Velev
  Fermilab, Batavia, Illinois

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

• M.A. Green
  LBNL, Berkeley, California
• Y. Ivanyushenkov
  CCLRC/RAL, Chilton, Didcot, Oxon
• W. Lau, R. Senanayake, S.Q. Yang
  OXFORDphysics, Oxford, Oxon

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

• M.A. Green, D. Li, S.P. Virostek, M.S. Zisman
  LBNL, Berkeley, California
• Y. Ivanyushenkov
  CCLRC/RAL, Chilton, Didcot, Oxon
• W. Lau, A. E. White, H. Witte, S.Q. Yang
  OXFORDphysics, Oxford, Oxon

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

• E. Métral
  CERN, Geneva

• G. Moritz, J. Kaugerts
  GSI, Darmstadt
• B. Auchmann, S. Russenschuck, R. de Maria
  CERN, Geneva
• J. Escallier, G. Ganetis, A.K. Jain, A. Marone, J.F. Muratore, R.A. Thomas, P. Wanderer
  BNL, Upton, Long Island, New York
• M. Wilson
  Oxford Instruments, Accelerator Technology Group, Oxford, Oxon

• C. Wang, V.P. Yakovlev
  Omega-P, Inc., New Haven, Connecticut
• J.L. Hirshfield
  Yale University, Physics Department, New Haven, CT
• T.C. Marshall
  Columbia University, New York

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

• Z. Zhang, R.D. Ruth, S.G. Tantawi
  SLAC, Menlo Park, California

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

• R. Giacone, D.L. Bruhwiler, J.R. Cary, D.A. Dimitrov, P. Messmer
  Tech-X, Boulder, Colorado
• E. Esarey, C.G.R. Geddes, W. Leemans
  LBNL, Berkeley, California

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

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

• G.R. Werner
  CIPS, Boulder, Colorado
• J.R. Cary
  Tech-X, Boulder, Colorado

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

• J. Wenninger, G. Arduini, B. Goddard, D. Jacquet, V. Kain, M. Lamont, V. Mertens, J.A. Uythoven
  CERN, Geneva
• Y.-C. Chao
  Jefferson Lab, Newport News, Virginia

• M. Deile, E. Alagoz, G.M. Anelli, G.A. Antchev, M. Ayache, F. Caspers, E. Dimovasili, R. Dinapoli, F.D. Drouhin, K. Eggert, L. Escourrou, O. Fochler, K. Gill, R. Grabit, F. Haug, P. Jarron, J. Kaplon, T. Kroyer, T. Luntama, D. Macina, E. Mattelon, L. Mirabito, H. Niewiadomski, E.P. Noschis, M. Oriunno, A. Park, A.-L. Perrot, O. Pirotte, J.M. Quetsch, F. Regnier, G. Ruggiero, S. Saramad, P. Siegrist, W. Snoeys, T. Souissi, R. Szczygiel, J. Troska, F. Vasey, A. Verdier
  CERN, Geneva
• V. Avati, M. Järvinen, M. Kalliokoski, J. Kalliopuska, K. Kurvinen, R. Lauhakangas, F. Oljemark, R. Orava, V. Palmieri, H. Saarikko, A. Soininen, K. Österberg
  Helsinki University, Department of Physics, University of Helsinki
• V. Berardi, M.G. Catanesi, E. Radicioni
  INFN-Bari, Bari
• V. Boccone, M. Bozzo, A. Buzzo, S. Cuneo, F. Ferro, M. Macri, S. Minutoli, A. Morelli, P. Musico, M. Negri, A. Santroni, G. Sette, A. Sobol
  INFN Genova, Genova
• C. Da Vià, J. Hasi, A. Kok, S. Watts
  Brunel University, Middlesex
• J. Kasper, V. Kundrât, M. V. Lokajicek, J. Smotlacha
  FZU, Prague

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

• M.J. Syphers, D.J. Harding
  Fermilab, Batavia, Illinois

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

• M.J. Syphers, G. Annala, D.A. Edwards, N.M. Gelfand, J.A. Johnstone, M.A. Martens, T. Sen
  Fermilab, Batavia, Illinois

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

• Y. Luo, S. Peggs, F.C. Pilat, T. Roser, D. Trbojevic
  BNL, Upton, Long Island, New York

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

• Y. Luo, P. Cameron, A. Della Penna, A. Marusic, S. Peggs, T. Roser, D. Trbojevic
  BNL, Upton, Long Island, New York
• O.R. Jones
  CERN, Geneva

Besides two eigentunes Q1 and Q2 , two amplitude ratios r1 and r2 and two phase differences ∆ φ₁ and ∆ φ₂ are introduced for the global coupling observation. Simulations are carried out to check their behaviors in the process of the skew quadrupole strength scans. Some attractive features of the phase differences ∆ φ_1,2 have been found, which are possibly useful for the global decoupling phase loop, or future global decoupling feedback. Analytical descriptions to these 6 quantities are described in the Twiss parameters through the linear coupling's action-angle parameterization, or in coupling coefficient through the linear coupling's Hamiltonian perturbation theory. Dedicated beam experiments are carried out at the Relativistic Heavy Ion Collider (RHIC) to check the global coupling observables from the phase lock loop (PLL) system. The six observables are measured under PLL driving oscillations during the 1-D and 2-D skew quadrupole scans. The experimental results are reported and discussions are given.

• Y. Luo, M. Bai, F.C. Pilat, T. Satogata, D. Trbojevic
  BNL, Upton, Long Island, New York

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

• C. Montag, A. Marusic, R.J. Michnoff, T. Roser, T. Satogata, C. Schultheiss
  BNL, Upton, Long Island, New York

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

• R. Pakter, F.B. Rizzato, W. Simeoni
  IF-UFRGS, Porto Alegre

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

• A.C. Kabel, Y. Cai
  SLAC, Menlo Park, California
• T. Sen
  Fermilab, Batavia, Illinois

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

• T. Pieloni, W. Herr
  CERN, Geneva

• J. Shi, B. Anhalt
  KU, Lawrence, Kansas

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

• 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

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).

• R. Connolly, R.J. Michnoff, S. Tepikian
  BNL, Upton, Long Island, New York

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

• J.B. Rosenzweig, A.M. Cook, M.P. Dunning, P. Frigola, G. Travish
  UCLA, Los Angeles, California
• D.T. Palmer
  SLAC, Menlo Park, California
• C. Sanelli, F. Tazzioli
  INFN/LNF, Frascati (Roma)

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

• S.S. Kurennoy, D.C. Nguyen, D.L. Schrage, R.L. Wood
  LANL, Los Alamos, New Mexico
• V. Christina, J. Rathke, T. Schultheiss
  AES, Medford, NY
• L.M. Young
  TechSource, Santa Fe, New Mexico

• L. Xiao, R.F. Boyce, D. Dowell, Z. Li, C. Limborg-Deprey, J.F. Schmerge
  SLAC, Menlo Park, California

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

• M.D. Cole
  AES, Medford, NY
• I. Ben-Zvi, A. Burrill, H. Hahn, T. Rao, Y. Zhao
  BNL, Upton, Long Island, New York
• P. Kneisel
  Jefferson Lab, Newport News, Virginia

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

• X. Bian, H. Chen, S. Zheng
  TUB, Beijing
• D. Li
  LBNL, Berkeley, California

• A. Morita, K. Egawa, K. Hosoyama, H. Koiso, T. Kubo, M. Masuzawa, K. Ohmi, K. Oide, R. Sugahara, M. Yoshida
  KEK, Ibaraki

• K. Ohmi, Y. Funakoshi, M. Tawada
  KEK, Ibaraki

• C.-K. Ng, N.T. Folwell, L. Ge, J. Langton, L. Lee, A. Novokhatski
  SLAC, Menlo Park, California

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

• T. Abe, T. Kageyama, H. Sakai, Y. Takeuchi
  KEK, Ibaraki

• 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

• K. Akai, Y. Morita
  KEK, Ibaraki

• T. Kageyama, T. Abe, H. Sakai, Y. Takeuchi
  KEK, Ibaraki

• T. Kamitani, N. Delerue, M. Ikeda, K. Kakihara, S. Ohsawa, T. Oogoe, T. Sugimura, T. T. Takatomi, S. Yamaguchi, K. Yokoyama
  KEK, Ibaraki
• Y. Hozumi
  GUAS/AS, Ibaraki

• H. Sakai, T. Abe, T. Kageyama, Y. Takeuchi
  KEK, Ibaraki

• T. Takahashi, M. Izawa, S. Sakanaka, K. Umemori
  KEK, Ibaraki
• T. Koseki
  RIKEN/RARF/CC, Saitama

• K. Yokoyama, M. Ikeda, K. Kakihara, T. Kamitani, S. Ohsawa, T. Sugimura, T. T. Takatomi
  KEK, Ibaraki

• V.V. Tarnetsky, V. Auslender, I. Makarov, M.A. Tiunov
  BINP SB RAS, Novosibirsk

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

• W.K. Lau, J. Chan, L.-H. Chang, C.W. Chen, H.Y. Chen, K.-T. Hsu, S.Y. Hsu, J.-Y. Hwang, Y.C. Wang, T.-T. Yang
  NSRRC, Hsinchu

• V. Wu, A.Z. Chen, Z. Qian, D. Wildman
  Fermilab, Batavia, Illinois

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

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

• D. Horan, E.E. Cherbak
  ANL, Argonne, Illinois

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.

• H. Ao, T. Morishita, A. Ueno
  JAERI/LINAC, Ibaraki-ken
• K. Hasegawa
  JAERI, Ibaraki-ken
• M. Ikegami
  KEK, Ibaraki
• V.V. Paramonov
  RAS/INR, Moscow
• Y. Yamazaki
  JAERI/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

• J. Watanabe, K. Nakayama, K. S. Sato, H. Suzuki
  Toshiba, Yokohama
• M. Izawa
  KEK, Ibaraki
• A. Jackson, G. LeBlanc, K. Zingre
  ASP, Clayton, Victoria
• T. Koseki
  RIKEN/RARF/CC, Saitama
• N. Nakamura, H. Sakai, H. Takaki
  ISSP/SRL, Chiba

• A. Smirnov, D. Yu
  DULY Research Inc., Rancho Palos Verdes, California

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

• Q.S. Shu, G. Cheng, J. T. Susta
  AMAC, Newport News, Virginia
• S.J. Einarson
  CPI/BMD, Beverley, Massachusetts
• T. Garvey
  LAL, Orsay
• W.-D. Müller, D. Proch
  DESY, Hamburg
• T.A. Treado
  CPI, Beverley, Massachusetts

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

• R.E. Laxdal, K. Fong, A.K. Mitra, T.C. Ries, I. Sekachev, G. Stanford, V. Zviagintsev
  TRIUMF, Vancouver

• H. Podlech, H. Deitinghoff, H. Klein, H. Liebermann, U. Ratzinger, A.C. Sauer, R. Tiede
  IAP, Frankfurt-am-Main

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.

• A. Gallo, D. Alesini, C. Biscari, R. Boni, F. Marcellini, M. Zobov
  INFN/LNF, Frascati (Roma)
• C. Pagani
  DESY, Hamburg

• J.H.P. Rogers, C.D. Beard, P.A. Corlett
  CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire

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

• V.D. Shemelin
  Cornell University, Ithaca, New York

Cornell University

• G. Ciovati, P. Kneisel
  Jefferson Lab, Newport News, Virginia

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

• G. Ciovati, P. Kneisel
  Jefferson Lab, Newport News, Virginia
• J.S. Sekutowicz, W. Singer
  DESY, Hamburg

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

• E. Daly, G.K. Davis, W.R. Hicks
  Jefferson Lab, Newport News, Virginia

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

• A.S. Hofler, J.R. Delayen
  Jefferson Lab, Newport News, Virginia

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.

• P. Kneisel, G. Ciovati, G. Myneni
  Jefferson Lab, Newport News, Virginia
• T. Carneiro
  Reference Metals, Bridgeville, Pennsylvania
• D. Proch, W. Singer, X. Singer
  DESY, Hamburg

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

*P. Kneisel et al., Linac 2004.

• P. Kneisel, G. Ciovati, G. Myneni
  Jefferson Lab, Newport News, Virginia
• T. Carneiro
  Reference Metals, Bridgeville, Pennsylvania
• J.S. Sekutowicz
  DESY, Hamburg

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

• P. Kneisel, G. Ciovati, G. Myneni, G. Wu
  Jefferson Lab, Newport News, Virginia
• J.S. Sekutowicz
  DESY, Hamburg

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

• C.E. Reece, E. Daly, S. Manning, R. Manus, S. Morgan, J.P. Ozelis, L. Turlington
  Jefferson Lab, Newport News, Virginia

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

• R.L. Geng, P. Barnes, M. Liepe, V. Medjidzade, H. Padamsee, A.K. Seaman, J. Sears, V.D. Shemelin, N. Sherwood
  Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York

• K.W. Shepard, Z.A. Conway, J.D. Fuerst, M. Kedzie, M.P. Kelly
  ANL, Argonne, Illinois

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

• K.W. Shepard, Z.A. Conway, J.D. Fuerst, M. Kedzie, M.P. Kelly
  ANL, Argonne, Illinois

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

• J.U. Urakawa
  KEK, Ibaraki

• H. Hayano
  KEK, Ibaraki

• D. Li, M.A. Green, S.P. Virostek, M.S. Zisman
  LBNL, Berkeley, California
• W. Lau, A. E. White, S.Q. Yang
  OXFORDphysics, Oxford, Oxon

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

• R.A. Rimmer
  Jefferson Lab, Newport News, Virginia

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

• H. Liebermann, H. Podlech, U. Ratzinger, A.C. Sauer
  IAP, Frankfurt-am-Main

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

• V.G. Vaccaro
  Naples University Federico II, Mathematical, Physical and Natural Sciences Faculty, Napoli
• T. Clauser, A. Rainò, V. Variale
  INFN-Bari, Bari
• A. D'Elia
  Naples University Federico II and INFN, Napoli
• C. De Martinis, D. Giove
  INFN-Milano, Milano
• M.R. Masullo
  INFN-Napoli, Napoli
• M. Mauri
  INFN/LASA, Segrate (MI)

• S. Sakanaka, K. Ebihara, S. Isagawa, M. Izawa, T. Kageyama, T. Kasuga, H. Nakanishi, M. Ono, H. Sakai, T. Takahashi, K. Umemori, S.I. Yoshimoto
  KEK, Ibaraki

• G. Huang, W.-H. Huang, S. Zheng
  Tsinghua University, Beijing
• D.M. Zhou
  IHEP Beijing, Beijing

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

• M.M. Paoluzzi, R. Garoby, M. Haase, P. Maesen, C. Rossi
  CERN, Geneva
• C. Ohmori
  KEK, Ibaraki

• V.P. Yakovlev, O.A. Nezhevenko
  Omega-P, Inc., New Haven, Connecticut
• J.L. Hirshfield
  Yale University, Physics Department, New Haven, CT

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.

• W. Roybal, D.C. Nguyen, W. Reass, D. Rees, P.J. Tallerico, P.A. Torrez
  LANL, Los Alamos, New Mexico

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

• K. Jin, Y. An, L. Feng, G. Huang, G. Liu, G. Wang, X. Zeng
  USTC/NSRL, Hefei, Anhui

• S.-H. Kim, B.H. Chung, K.-H. Chung, J.-S. Hong, J.-H. Jeon, sk. Ko, K. Lee, sj. Noh
  KAPRA, Cheorwon

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

• P. Piot
  Fermilab, Batavia, Illinois
• M. Dohlus, K. Floettmann, M. Marx, S.G. Wipf
  DESY, Hamburg

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

• H. Matsumoto, S. Kazakov, K. Saito
  KEK, Ibaraki

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.

• C.D. Nantista, V.A. Dolgashev, R. Siemann, S.G. Tantawi, J. Weisend
  SLAC, Menlo Park, California
• I.E. Campisi
  ORNL, Oak Ridge, Tennessee

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.

• J. Shi, H. Chen, S. Zheng
  TUB, Beijing
• J.M. Byrd, D. Li
  LBNL, Berkeley, California

• 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

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.

• F.C. Pilat, Y. Luo, N. Malitsky, V. Ptitsyn
  BNL, Upton, Long Island, New York

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.

• 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

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.

• M. Kobayashi
  KEK, Ibaraki

• M. Zobov, D. Alesini, G. Benedetti, M.E. Biagini, C. Biscari, R. Boni, M. Boscolo, A. Clozza, G.O. Delle Monache, G. Di Pirro, A. Drago, A. Gallo, A. Ghigo, S. Guiducci, M. Incurvati, C. Ligi, F. Marcellini, G. Mazzitelli, C. Milardi, L. Pellegrino, M.A. Preger, P. Raimondi, R. Ricci, C. Sanelli, M. Serio, F. Sgamma, B. Spataro, A. Stecchi, A. Stella, C. Vaccarezza, M. Vescovi
  INFN/LNF, Frascati (Roma)
• J.D. Fox, D. Teytelman
  SLAC, Menlo Park, California
• E. Levichev, P.A. Piminov, D.N. Shatilov
  BINP SB RAS, Novosibirsk

• P. Drumm
  CCLRC/RAL, Chilton, Didcot, Oxon

• R.L. Geng, A.K. Seaman, V.D. Shemelin
  Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
• H. Padamsee
  Cornell University, Ithaca, New York

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

• L. Emery
  ANL, Argonne, Illinois

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

• A.S. Kesar, S.E. Korbly, R.J. Temkin
  MIT/PSFC, Cambridge, Massachusetts
• M. Hess
  IUCF, Bloomington, Indiana

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.

• H. Nishimura, T. Scarvie
  LBNL, Berkeley, California

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

• W. Guo, M. Borland, K.C. Harkay, V. Sajaev, B.X. Yang
  ANL, Argonne, Illinois

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

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

• A.J. Saverskiy, H. Deruyter, M. Hernandez, A.V. Mishin, D. Skowbo
  AS&E, Billerica, Massachusetts

• V.G. Vaccaro
  Naples University Federico II and INFN, Napoli
• T. Clauser, A. Rainò
  Bari University, Science Faculty, Bari
• C. De Martinis, D. Giove, M. Mauri
  INFN/LASA, Segrate (MI)
• S. Lanzone
  Naples University Federico II, Napoli
• M.R. Masullo
  INFN-Napoli, Napoli
• V. Variale
  INFN-Bari, Bari

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

• A. Jansson, P. Lebrun, J.T. Volk
  Fermilab, Batavia, Illinois

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

• J.M. Weber, M.J. Chin, L.R. Doolittle
  LBNL, Berkeley, California
• R. Akre
  SLAC, Menlo Park, California

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

• W.J. Corbett, C. Limborg-Deprey, W.Y. Mok, A. Ringwall
  SLAC, Menlo Park, California

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

• N. Barov, J.S. Kim, A.W. Weidemann
  Far-Tech, Inc., San Diego, California
• R.H. Miller, C.D. Nantista
  SLAC, Menlo Park, California

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

• L. Ducimetière
  CERN, Geneva

• R.J. Briggs
  SAIC, Alamo, California
• L. R. Reginato, W. Waldron
  LBNL, Berkeley, California

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

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

• C.C. Jensen, G. E. Krafczyk
  Fermilab, Batavia, Illinois

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

• Z.-D. Tsai, J.-C. Chang, C.-Y. Liu
  NSRRC, Hsinchu
• J.-R. Chen
  NTHU, Hsinchu

• D.-J. Wang, H.C. Ho, Z.-D. Tsai, J. Wang
  NSRRC, Hsinchu

• P. Marchand, M. Louvet, M. Louvet-Monsanglant, K. Tavakoli, C. Thomas-Madec
  SOLEIL, Gif-sur-Yvette
• L. Arnaudon, O. Brunner, R. Losito, P. Maesen, E. Montesinos, G. Pechaud, M.P. Prax
  CERN, Geneva
• P. Bosland, P. Bredy, S. Chel, G. Devanz
  CEA/DSM/DAPNIA, Gif-sur-Yvette

• V.D. Shemelin, H. Padamsee
  Cornell University, Ithaca, New York
• M. Liepe
  Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York

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.

• V.V. Paramonov, L.V. Kravchuk
  RAS/INR, Moscow
• K. Floettmann
  DESY, Hamburg
• M. Krasilnikov, F. Stephan
  DESY Zeuthen, Zeuthen

• R.M. Jones, R.H. Miller
  SLAC, Menlo Park, California

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

• J.W. Wang, C. Adolphsen, V. Bharadwaj, G.B. Bowden, V.A. Dolgashev, R.M. Jones, E.N. Jongewaard, J.R. Lewandowski, Z. Li, R.H. Miller
  SLAC, Menlo Park, California

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

• 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

• M. Ikegami, Z. Igarashi, S. Lee
  KEK, Ibaraki
• H. Akikawa, K. Hasegawa, Y. Kondo, T. Ohkawa
  JAERI, Ibaraki-ken
• H. Ao, S. Sato, T. Tomisawa, A. Ueno
  JAERI/LINAC, Ibaraki-ken

• Y.-S. Cho, S.-H. Han, J.-H. Jang, H.-S. Kim, Y.-H. Kim, H.-J. Kwon, M.-Y. Park, K.T. Seol
  KAERI, Daejon

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

• H.-J. Kwon, Y.-S. Cho, J.-H. Jang, H.-S. Kim, Y.-H. Kim
  KAERI, Daejon

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

• P. Stoltz, A. Prideaux
  Tech-X, Boulder, Colorado

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

• H. Qin, R.C. Davidson, S.R. Hudson, E. Startsev
  PPPL, Princeton, New Jersey

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

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

• J.-F. Ostiguy, M. Kriss, M. McCusker-Whiting, L. Michelotti
  Fermilab, Batavia, Illinois

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

• J. Beebe-Wang
  BNL, Upton, Long Island, New York

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.

• W. Waldron, L. R. Reginato
  LBNL, Berkeley, California
• R.J. Briggs
  SAIC, Alamo, California

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

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

• S.D. Nelson, G.J. Caporaso, A. Friedman, B.R. Poole
  LLNL, Livermore, California
• R.J. Briggs
  SAIC, Alamo, California
• W. Waldron
  LBNL, Berkeley, California

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

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

• S.D. Nelson, B.R. Poole
  LLNL, Livermore, California

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

• A. Roy
  NSC, New Delhi

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