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MO302 Development of Room Temperature and Superconducting CH-Structures linac, proton, impedance, ion 28
 
  • H. Podlech
    IAP, Frankfurt-am-Main
  H-mode cavities (IH-DTL, IH-RFQ, 4-Vane-RFQ) have been developed and operated successfully during the last decades for a large variety of applications in ion acceleration. At the IAP Frankfurt a new type of H-mode cavity, the CH-structure is under development. This multi cell drift tube cavity is operated in the H21 mode. Due to its mechanical stability, room temperature as well as superconducting cavities can be realized. The CH-structure is an excellent candidate for high power ion accelerators in the energy range from 5 to 100 MeV. The design status of the GSI 70 MeV, 70 mA proton injector DTL consisting of room temperature CH-structures is reported. Superconducting CH-structures can be used especially for cw operated linacs as designed for XADS, IFMIF or in nuclear physics projects. By using the KONUS beam dynamics and performing the particle simulations with the LORASR code it is possible to realize multi cell cavities without internal focusing lenses. A superconducting 352 MHz CH-structure (β=0.1) with 19 gaps has been built. We present the results of the first tests with this new cavity. The status of a PC version of the LORASR code will be reported.  
Transparencies
 
MOP12 KONUS Beam Dynamics Design of a 70 mA, 70 MeV Proton CH-DTL for GSI-SIS12 linac, proton, rfq, quadrupole 60
 
  • R. Tiede, G. Clemente, H. Podlech, U. Ratzinger
    IAP, Frankfurt-am-Main
  • W. Barth, L. Groening
    GSI, Darmstadt
  • Z. Li
    IMP, Lanzhou
  • S. Minaev
    ITEP, Moscow
  The future scientific program at GSI needs a dedicated proton injector into the synchrotron SIS, in order to increase the proton intensity of the existing UNILAC/SIS12 combination by a factor of 70, resulting in 7· 1012 protons in the synchrotron. A compact and efficient 352 MHz RFQ - CH-DTL combination based on novel structure developments for RFQ and DTL was worked out. For DTLs operated in an H-mode like CH-cavities (H210-mode), the shunt impedance is optimized by use of the KONUS beam dynamics. Beam dynamics simulation results of the CH-DTL section, covering the energy range from 3 to 70 MeV, with emphasis on the low energy front end are presented. Optimization aims are the reduction of emittance growth, of beam losses and of capital costs, by making use of the high acceleration gradients and shunt impedance values provided by the Crossbar H-Type (CH) structure. In addition, the beam dynamics design of the overall DTL layout has to be matched to the power limits of the available 352 MHz power klystrons. The aim is to power each cavity by one klystron with a peak rf power of around 1 MW.  
 
MOP30 Linear Accelerator LINAC-800 of the DELSY Project electron, linac, gun, radiation 105
 
  • V.V. Kobets, N. Balalykin, I.N. Meshkov, I.A. Seleznev, G. Shirkov
    JINR, Dubna, Moscow Region
  In the report the modernization of electron linear accelerator MEA (Medium Energy Accelerator) is discussed. The goal of the work is to create on the base of MEA a complex of free electron lasers overlaying a range of radiation waves from infrared to ultraviolet. Status of the work is reported.  
 
MOP31 Development of a C-band Accelerating Module for SUPERKEKB linac, positron, klystron, electron 108
 
  • S. Ohsawa, M. Ikeda, K. Kakihara, T. Kamitani, T. Oogoe, T. Sugimura, S. Yamaguchi, K. Yokoyama
    KEK, Ibaraki
  High power rf processing of 1 m C-band accelerating section for Super KEKB was successfully performed and power corresponding to 42 MV/m was achieved. Processing data were accumulated including acoustic sensor to find the arcing position. No structural damage was observed from the phase shift measurement performed after the processing. Processed accelerator was installed in the beam line of KEKB linac and being re-processed. The beam acceleration of 40 MV/m was successfully achieved in October 2003. Present status of C-band accelerator development is reported.  
 
MOP44 Electron-Cloud Effects in the Positron Linacs of Future Linear Colliders electron, linac, positron, simulation 141
 
  • D. Schulte, A. Grudiev, F. Zimmermann
    CERN, Geneva
  • K. Oide
    KEK, Ibaraki
  Inside the rf structures of positron linacs for future linear colliders, electron multipacting may occur under the combined influence of the beam field and the electromagnetic rf wave. The multipacting could lead to an electron-cloud build up along the bunch train. We present simulation results of this effect for various proposed designs, and discuss possible consequences and eventual countermeasures.  
Transparencies
 
MOP68 Ribbon Ion Beam Dynamics in Undulator Linear Accelerator focusing, undulator, ion, linac 177
 
  • E.S. Masunov, S.M. Polozov
    MEPhI, Moscow
  The possibility to use radio frequency undulator fields for ion beam focusing and acceleration in linac (UNDULAC-RF) is discussed. In periodical resonator structure the accelerating force is produced by the combination of two or more space harmonics of a longitudinal or a transverse undulator field*. The particle motion equations in Hamilton form are carried out by means of smooth approximation. The analysis of 3D effective potential permits to find the conditions under which focusing and acceleration of the particles occur simultaneously. The analytical results are verified with a numerical simulation. Examples illustrating the efficiency of the proposed method of acceleration are given for longitudinal and transverse undulators. The results are compared with a conventional linac and the other possibility of ion beam acceleration in UNDULAC-E(M) where electrostatic and magnetic fields are used.

*E.S. Masunov, Technical Physics, Vol. 46, No.11, 2001, pp. 1433-1436.

 
 
MOP71 Advanced Beam-Dynamics Simulation Tools for RIA linac, simulation, beam-losses, rfq 186
 
  • T.P. Wangler, R. Garnett
    LANL, Los Alamos, New Mexico
  • N. Aseev, P.N. Ostroumov
    ANL/Phys, Argonne, Illinois
  • R. Crandall
    TechSource, Santa Fe, NM
  • D. Gorelov, R.C. York
    NSCL, East Lansing, Michigan
  • J. Qiang, R. Ryne
    LBNL, Berkeley, California
  Understanding beam losses is important for the high-intensity RIA driver linac. Small fractional beam losses can produce radioactivation of the beamline components that can prevent or hinder hands-on maintenance, reducing facility availability. Operational and alignment errors in the RIA driver linac can lead to beam losses caused by irreversible beam-emittance growth and halo formation. We are developing multiparticle beam-dynamics simulation codes for RIA driver-linac simulations extending from the low-energy beam transport (LEBT) line to the end of the linac. These codes run on the NERSC parallel supercomputing platforms at LBNL, which allow us to run simulations with large numbers of macroparticles for the beam-loss calculations. The codes have the physics capabilities needed for RIA, including transport and acceleration of multiple-charge-state beams, and beam-line elements such as high-voltage platforms within the linac, interdigital accelerating structures, charge-stripper foils, and capabilities for handling the effects of machine errors and other off-normal conditions. We will present the status of the work, including examples showing some initial beam-dynamics simulations.  
 
MOP75 Hminus Distribution in the HERA RF-Volume Source laser, electron, plasma, extraction 198
 
  • J. Peters
    DESY, Hamburg
  The HERA RF-Volume Source is the only source available that delivers routinely an Hminus current of 40 mA without Cs. The production mechanism for Hminus ions in this type of source is still under discussion. Laser photodetachment measurements have been started at DESY in order to measure the Hminus distribution in the source. The measurements have also been done under extraction conditions at high voltage. The results of the measurements with and without extraction are a basis for the development of a theory for the transition between plasma and vacuum (sheath), a cornerstone for beam transport programs. Knowledge of the H- distribution and where they are produced makes further source improvements possible.  
 
MOP86 Cold Test Results of the ISAC-II Medium Beta High Gradient Cryomodule coupling, alignment, linac, lattice 222
 
  • R.E. Laxdal, Y. Bylinskii, G.S. Clark, K. Fong, A.K. Mitra, R. L. Poirier, B. Rawnsley, T. Ries, I. Sekatchev, G. Stanford, V. Zvyagintsev
    TRIUMF, Vancouver
  Many proposals (RIA, Eurisol, ISAC-II) are emerging for a new generation of high gradient heavy ion accelerators. The ISAC-II medium beta cryomodule represents the first realized application that encorporates many new techniques to improve the performance over machines presently being used for beam delivery. The machine lattice, compatible with multi-charge acceleration, uses high field (9T) superconducting solenoids with bucking coils for active fringe field compensation. The bulk niobium quarter wave medium beta cavity produces 6 MV/m over an effective length of 18cm with a peak surface field of ~30 MV/m. TRIUMF has developed a mechanical tuner capable of both coarse (kHz) and fine (Hz) frequency adjustments of the cavity. The demonstrated tuner resolution is better than 0.1 μm (0.6 Hz). A new rf coupling loop has been developed that operates at 200 Watts forward power with less than 0.5 Watt of power being added to the helium load. Cold alignment in ISAC-II has been done with rf pick-ups using a stretched wire technique. Finally all cryomodule and testing has been done in a clean environment. The alignment cryogenic, solenoid and rf performance will be presented.  
Transparencies
 
MOP88 RF Coupler Design for the TRIUMF ISAC-II Superconducting Quarter Wave Resonator coupling, simulation, superconductivity, damping 228
 
  • R. L. Poirier, K. Fong, P. Harmer, R.E. Laxdal, A.K. Mitra, I. Sekatchev, B. Waraich, V. Zvyagintsev
    TRIUMF, Vancouver
  An RF Coupler for the ISAC-II medium beta (β=0.058 and 0.071) superconducting quarter wave resonators was designed and tested at TRIUMF. The main goal of this development was to achieve stable operation of superconducting cavities at high acceleration gradients and low thermal load to the helium refrigeration system. The cavities will operate at 6 MV/m acceleration gradient in overcoupled mode at a forward power 200 W at 106 MHz. The overcoupling provides ±20 Hz cavity bandwidth, which improves the stability of the RF control system for fast helium pressure fluctuations, microphonics and environmental noise. Choice of materials, cooling with liquid nitrogen, aluminum nitride RF window and thermal shields insure a small thermal load on the helium refrigeration system by the Coupler. An RF finger contact which causedμdust in the coupler housing was eliminated without any degradation of the coupler performance. RF and thermal calculations, design and test results on the coupler are presented in this paper.  
 
MOP89 A Wire Position Monitor System for the ISAC-II Cryomodule Components Alignment alignment, linac, vacuum, impedance 231
 
  • B. Rawnsley, Y. Bylinskii, G. Dutto, K. Fong, R.E. Laxdal, T. Ries
    TRIUMF, Vancouver
  • D. Giove
    INFN/LASA, Segrate (MI)
  TRIUMF is developing ISAC-II, a superconducting (SC) linac. It will comprise 9 cryomodules with a total of 48 niobium cavities and 12 SC solenoids. They must remain aligned at liquid He temperatures: cavities to ±400 μm and solenoids to ±200 μm after a vertical contraction of ~4 mm. A wire position monitor (WPM) system based on a TESLA design has been developed, built, and tested with a prototype cryomodule. The system is based on the measurement of signals induced in pickups by a 215 MHz signal carried by a wire through the WPMs. The wire is stretched between the warm tank walls parallel to the beam axis providing a position reference. The sensors, one per cavity and two per solenoid, are attached to the cold elements to monitor their motion during pre-alignment, pumping and cool down. A WPM consists of four 50 Ω striplines spaced 90° apart. A GaAs multiplexer scans the WPMs and a Bergoz card converts the RF signals to DC X and Y voltages. National Instruments I/O cards read the DC signals. The data acquisition is based on a PC running LabVIEW. System accuracy is ~7 μm. The paper describes system design, WPM calibration and test results.  
 
MOP92 Simulation of the RF Coupler for TRIUMF ISAC-II Superconducting Quarter Wave Resonators coupling, simulation, impedance, cryogenics 234
 
  • V. Zvyagintsev
    TRIUMF, Vancouver
  The inductive RF coupler for the TRIUMF ISAC-II 106 MHz superconducting accelerating quarter wave resonators was used as a basis for the simulation model of stationary transmission processes of RF power and thermal fluxes. Electromagnetic simulation of the coupler was done with ANSOFT HFSS code. Transmission line theory was used for electromagnetic wave calculations along the drive line to the Coupler. An analogy between electric and thermal processes allows the thermal calculations to be expressed in terms of electrical circuits. The data obtained from the simulation are compared to measured values on the RF coupler.  
 
TU102 Survey of Advanced Acceleration Techniques electron, laser, plasma, undulator 242
 
  • C.J. Joshi
    UCLA, Los Angeles, California
  In this talk I will review the recent progress on the production, manipulation, transport, acceleration and focusing of relativistic electron beams using advanced techniques. In particular, I will report recent progress on cathode-less electron injectors, IFEL bunchers and accelerators, plasma accelerating and transport structures, and electron and positron beam focusing using plasmas. The plasma structures for acceleration can be excited either by laser beams or charged-particle beams. The acceleration gradients in either case can be enormous. For unmatched beams the betatron radiation loss, as the beam oscillates transversely in the high gradient accelerating structure, can generate a high brightness x-ray beam. These x-rays can, in turn, be used to generate positrons. Work done by different groups around the world will be reviewed.  
Transparencies
 
TUP06 Results of the High-Power Conditioning and the First Beam Acceleration of the DTL-1 for J-PARC coupling, linac, rfq, quadrupole 300
 
  • F. Naito, S. Anami, J. Chiba, Y. Fukui, K. Furukawa, Z. Igarashi, K. Ikegami, M. Ikegami, E. Kadokura, N. Kamikubota, T. Kato, M. Kawamura, H. Kobayashi, C. Kubota, E. Takasaki, H. Tanaka, S. Yamaguchi, K. Yoshino
    KEK, Ibaraki
  • K. Hasegawa, Y. Kondo, A. Ueno
    JAERI, Ibaraki-ken
  • T. Itou, Y. Yamazaki
    JAERI/LINAC, Ibaraki-ken
  • T. Kobayashi
    J-PARC, Ibaraki-ken
  The first tank of the DTL for Japan Proton Accelerator Research Complex (J-PARC) was installed in the test facility at KEK. The DTL tank is 9.9 m in length and consists of the 76 cells. The resonant frequency of the tank is 324 MHz. After the installation of the tank, the high-power conditioning was carried out deliberately. Consequently the peak rf power of 1.3 MW (pulse repetition 50 Hz, pulse length 600 μs) was put into the tank stably. (The required power is about 1.1 MW for the designed accelerating field of 2.5 MV/m on the axis.) Following the conditioning, negative hydrogen beam, accelerated by the RFQ linac up to 3 MeV, was injected to the DTL and accelerated up to its design value of 19.7 MeV. The peak current of 30 mA was achieved with almost 100% transmission. In this paper, the conditioning history of the DTL and the result of the first beam test will be described.  
 
TUP13 Test and First Experiments with the new REX-ISOLDE 200 MHz IH-Structure injection, impedance, linac, ion 318
 
  • T. Sieber
    CERN, Geneva
  • D. Habs, O.K. Kester
    LMU, Garching
  For the REX-ISOLDE accelerator, a new accelerating structure is at the moment installed and tested. It willl raise the final energy from the present 2.3 MeV/u to 3 MeV/u. The aim is to increase the mass range of the nuclei available for nuclear spectroscopy from mass 40 to mass 80. The new accelerator component is a 0.5 m IH-structure, working at the double REX frequency of 202.56 MHz. It was originally developed as a 7-Gap resonator for the MAFF* project and later adapted to the requirements at REX by changing from a 7-Gap to a 9-Gap resonator to match the lower injection energy. The poster presents the design of the resonator and the results of the rf-tests, commissioning and first operation during the 2004 running period.

*H. Bongers et al., The IH-7-Gap Resonators of the Munich Accelerator for Fission Fragments (MAFF) Linac, proceedings of the PAC2001, Chicago, June 2001, p.3945

 
 
TUP16 Investigation on Beam Dynamics Design of High-Intensity RFQs rfq, focusing, space-charge, emittance 327
 
  • C. Zhang, A. Schempp
    IAP, Frankfurt-am-Main
  • J. Chen, J. Fang, Z.Y. Guo
    PKU/IHIP, Beijing
  Recently various potential uses of high-intensity beams bring new opportunities as well as challenges to RFQ accelerator research because of the new problems arising from the strong space-charge effects. Unconventional concepts of beam dynamics design, which surround the choice of basic parameters and the optimization of main dynamics parameters’ variation along the machine, are illustrated by the designing Peking University (PKU) Deuteron RFQ. An efficient tool of LANL RFQ Design Codes for beam dynamics simulation and analysis, RFQBAT, is introduced. Some quality criterions are also presented for evaluating design results.  
 
TUP27 Acceleration of Several Charge States of Lead Ion in CERN LINAC3 rfq, linac, ion, injection 351
 
  • V. Coco, J.A. Chamings, A.M. Lombardi, E.Zh. Sargsyan, R. Scrivens
    CERN, Geneva
  CERN’s LINAC3 is designed to accelerate a 100 μAe Pb25+ ion beam from 2.5 keV/u to 4.2 MeV/u. The beam is then stripped using a carbon foil and the resulting 25 μAe 54+ beam is accumulated and cooled in the Low Energy Ion Ring (LEIR) before transfer to the Proton Synchrotron (PS) and ultimately to the Large Hadron Collider (LHC). The Pb25+ ions are selected with a spectrometer from a mixture of ten charge states produced by an Electron Cyclotron Resonance (ECR) source. In view of the fact that the stripping efficiency to Pb54+ is mostly dependent on energy and not on initial charge state, the feasibility of simultaneously accelerating to 4.2 MeV/u several charge states has been investigated. In this paper we report two possible technical solutions, their advantage in terms of intensity for the downstream machines and the experimental results supporting these conclusions.  
 
TUP56 Simulation of RF Breakdown Effects on NLC Beam electron, simulation, linac, ion 396
 
  • V.A. Dolgashev
    SLAC/ARDB, Menlo Park, California
  • T.O. Raubenheimer
    SLAC/NLC, Menlo Park, California
  The linacs of the Next Linear Collider (NLC) will contain several thousand traveling wave X-Band accelerator structures operating at input power of about 60 MW. At this input power prototypes of NLC structures have breakdown rates lower than one breakdown in ten hours. RF breakdowns disrupt flow of energy inside the structure and create arcs with electron and ion currents. Electromagnetic fields of these currents interact with the NLC beam. We simulated deflection of the NLC beam caused by breakdown currents using the particle-in-cell code MAGIC. In this paper we present modeling considerations and simulation results.  
 
TUP94 Parallel Particle in Cell Computation of an Electron Gun with GdfidL gun, electromagnetic-fields, scattering, electron 498
 
  • W. Bruns
    TU Berlin TET, Berlin
  The paper describes an efficient algorithm to integrate the equations of a fast moving charge cloud of small size in a large electron gun. Particle in cell computations of a realistic electron gun is challenging due to the large discrepancy between the size of the cavity and the size of the cloud. A fine grid must be used to resolve the small volume of the charge, with a grid spacing in the order of 0.1 mm. The cavity has extensions of about 100 mm. Therefore one has to deal with about 1000 million gridcells. Such a large grid is handled best with parallel systems. Each node of the parallel system computes the electromagnetic field in its subvolume. As the extension of the charge keeps being small during the flight, at each timestep the charged particles will be located in only a few subvolumes of the nodes of the parallel system. This would lead to a strong load imbalance, if the particle related computations for each particle would be performed by the node where the particle is in. GdfidL instead spreads the data of all particle over all processors, which perform the particle related computations, and send back the results to the processors where the particles are in.  
 
TUP96 Mechanical Stability Simulations on a Quarter Wave Resonator for the SPIRAL II Project simulation, linac, vacuum, coupling 504
 
  • H. Saugnac, J.-L. Biarrotte, S. Blivet, S. Bousson, M. Fouaidy, T. Junquera, G. Olry
    IPN, Orsay
  In the framework of the SPIRAL II project, IPN Orsay is studying a 88 MHz β=0.12 super conducting quarter wave resonator prototype. Due to its low RF bandwidth (around 60 Hz) the resonator must have a very high mechanical stability and have small sensitivity to dynamic mechanical loads. To simulate the effects of geometrical deformations on the fundamental RF frequency a three dimensional analysis is required. The simulations were made by coupling mechanical FEM analysis performed in COSMOS/GEOSTAR™ with the RF electromagnetic FEM code MICAV™ integrated in the COSMOS/GEOSTAR™ interface. Static mechanical loads were first studied to reduce the effects of external pressure on the RF frequency shift and evaluate the tuning sensitivity of the cavity. Then, simulations on the dynamic response of the resonator, using the modal superposition analysis method, with random external pressure variations and harmonic excitation of the cavity were performed. This paper presents the results of the simulations and mechanical solutions chosen to increase the cavity RF frequency stability.  
 
WE205 KEKB Injector Linac and Upgrade for SuperKEKB klystron, linac, injection, positron 549
 
  • S. Michizono
    KEK, Ibaraki
  KEKB Injector linac has provided the 8 GeV electrons and 3.5 GeV positrons to the KEKB asymmetric collider rings designed for the B-physics study. The KEKB has recorded the highest luminosity records to which the linac contributes with an advanced operational stability. The dualbunch injection and continuous injection schemes have been adopted. The operational status of the KEKB injector linac is summarized here. The Super KEKB project aiming for the ten-times higher luminosity is under consideration as the upgrade of KEKB. In this upgrade, the injector linac has to increase the positron acceleration energy from 3.5 GeV to 8 GeV. In order to double the acceleration field (from 20 to 40 MV/m), the C-band rf system has been tested. The newly developed components, such as an acceleration structure and an rf window, are summarized. A C-band acceleration structure is installed in KEKB linac after the rf conditioning of more than 40 MW. The energy gain of more than 40 MV/m is confirmed by the beam analysis. The C-band acceleration unit has been operated continuously for the stability test. The recent operational status of the c-band acceleration unit will be also reported.  
Transparencies
 
TH301 Intermediate-Velocity Superconducting Accelerating Structures linac, ion, proton, impedance 589
 
  • J. R. Delayen
    Jefferson Lab, Newport News, Virginia
  In the last decade, one of the most active areas in the application of the superconducting (SC) rf technology has been for the acceleration of ions to medium energies (~1 GeV/amu). One such accelerator is under construction in the US while others are being proposed in the US, Japan, and Europe. These new facilities require SC accelerating structures operating in a velocity region that has until recently been unexplored, and new types of structures optimized for the velocity range from ~0.2 to ~0.8 c have been developed. We will review the properties of these intermediate-velocity structures, the status of their development, as well as present an overview of the medium-energy superconducting ion accelerator designs being developed world-wide.  
Transparencies
 
THP14 High Beta Cavity Optimization for ISAC-II linac, ion, quadrupole, emittance 627
 
  • R.E. Laxdal, V. Zvyagintsev
    TRIUMF, Vancouver
  • Z.H. Peng
    CIAE, Beijing
  The linac for ISAC-II comprises twenty cavities of medium beta (β=5.8 and 7.1%) quarter wave cavities now in the installation phase. A second stage will see the installation of ~20 MV of high beta quarter wave cavities (~10.4%). The cavity structure choice depends on the efficiency of operation, cost, stability, beam dynamics and schedule. Two main cavity types are considered; a low frequency 106 MHz option and a high frequency 141 MHz cavity. We compare and contrast the cavity choices.  
 
THP18 The Acceleration Test of the APF-IH-LINAC linac, ion, focusing, proton 636
 
  • K. Yamamoto, M. Okamura
    RIKEN, Saitama
  • T. Hattori
    TIT, Tokyo
  • S. Yamada
    NIRS, Chiba-shi
  We manufactured an IH linac with Alternating Phase Focusing as a test machine for medical accelerator injection. It will accelerate C4+ ions from 40 keV/u up to 2 MeV/u. The tank length is around 1.5 m, operation frequency is 100 MHz. We have succeeded to accelerate protons with a simple acceleration system, consisting of a PIG ion source, bending magnets and focus lenses, less than 5m long. This IH linac was calculated using a simple thin lens approximation. Now we are making a beam-tracking program using the results of the electro-magnetic simulation soft (Micro-Wave-Studio, OPERA-3D); it has the merit of easily calculating the 3D-beam dynamics including non-linear effects. We will report the test, the beam simulations and comparisons of the test to the simulations.  
 
THP25 Development of Field-Emission Electron Gun from Carbon Nanotubes cathode, electron, vacuum, gun 651
 
  • Y. Hozumi
    GUAS/AS, Ibaraki
  • M. Ikeda, S. Ohsawa, T. Sugimura
    KEK, Ibaraki
  Aiming to use a narrow energy-spread electron beam easily and low costly on injector electron guns, we have been tested field emission cathodes of carbon nanotubes (CNTs). Experiments for these three years brought us important suggestions and a few rules of thumb. Now at last, anode current of 3.0 [A/cm2] was achieved with 8 kV acceleration voltage by applying short grid pulses between cathode-grid electrodes. In order to proof utility, 100 kV gun system had been designed and structured since last year. Then the value of 300 mA was obtained based on 10-5…10-6 [Pa] back ground pressures. With some improvements anode currents of Ampere order is expected.  
 
THP29 Development of C-band Accelerating Section for SuperKEKB linac, positron, klystron, coupling 663
 
  • T. Kamitani, N. Delerue, M. Ikeda, K. Kakihara, S. Ohsawa, T. Oogoe, T. Sugimura, T. Takatomi, S. Yamaguchi, K. Yokoyama
    KEK, Ibaraki
  • Y. Hozumi
    GUAS/AS, Ibaraki
  For the luminosity upgrade of the present KEK B-factory to SuperKEKB, the injector linac has to increase the positron acceleration energy from 3.5 to 8.0 GeV. In order to double the acceleration field gradient from 21 to 42 MV/m, design studies on C-band accelerator module has started in 2002. First prototype 1-m long accelerating section has been fabricated based upon a design which is half scale of the present S-band section. High power test of the C-band section has been performed at a test stand and later at an accelerator module in the KEKB injector linac. In a beam acceleration test, a field gradient of 41 MV/m is achieved with 43 MW RF power from a klystron. This paper report on the recent status of the high-power test and also the development of a second prototype section.  
 
THP31 A Four-Cell Periodically HOM-Damped RF Cavity for High Current Accelerators damping, coupling, dipole, impedance 669
 
  • G. Wu, R.A. Rimmer, H. Wang
    Jefferson Lab, Newport News, Virginia
  • J. Sekutowicz
    DESY, Hamburg
  • A. Sun
    ORNL/SNS, Oak Ridge, Tennessee
  A periodically Higher Order Mode (HOM) damped RF cavity is a weakly coupled multi-cell RF cavity with HOM couplers periodically mounted between the cells. It was studied as an alternative RF structure between the single cell cavity and superstructure cavity in high beam current application requiring strong damping of the HOMs. The acceleration mode in this design is the lowest frequency mode (Zero Mode) in the pass band, in contrast to the traditional “π” acceleration mode. The acceleration mode of a four-cell Zero Mode cavity has been studied along with the monopole and dipole HOMs. Some HOMs have been modeled in HFSS with waveguide HOM couplers, which were subsequently verified by MAFIA time domain analysis. To understand the tuning challenge for the weakly coupled cavity, ANSYS and SUPERFISH codes were used to simulate the cavity frequency sensitivity and field flatness change within proper tuning range, which will influence the design of the tuner structure. This paper presents this novel accelerating structure that may be used for variety of accelerator applications.  
 
THP35 Development of a Non-Magnetic Inertial Sensor for Vibration Stabilization in a Linear Collider feedback, linear-collider, collider, damping 681
 
  • J. Frisch, A. Chang, V. Decker, L. Hendrickson, T. Markiewicz, R. Partridge, A. Seryi
    SLAC, Menlo Park, California
  • D. Eric, T. Himel
    SLAC/NLC, Menlo Park, California
  One of the options for controlling vibration of the final focus magnets in a linear collider is to use active feedback based on accelerometers. While commercial geophysics sensors have noise performance that substantially exceeds the requirements for a linear collider, they are physically large, and cannot operate in the strong magnetic field of the detector. Conventional nonmagnetic sensors have excessive noise for this application. We report on the development of a non-magnetic inertial sensor, and on a novel commercial sensor both of which have demonstrated the required noise levels for this application.  
Transparencies
 
THP58 Development of C-band High-Power Mix-Mode RF Window vacuum, resonance, klystron, electron 745
 
  • S. Michizono, S. Fukuda, T. Matsumoto, K. Nakao, T. Takenaka
    KEK, Ibaraki
  • K. Yoshida
    MELCO, Hyogo
  High power c-band (5712 MHz) rf system (40 MW, 2 μs, 50 Hz) is under consideration for the electron-linac upgrade aimed for the super KEKB project. An rf window, which isolates the vacuum and pass the rf power, is one of the most important components for the rf system. The window consists of a ceramic disk and a pill-box housing. The mix-mode rf window is designed so as to decrease the electric field on the periphery of the ceramic disk. A resonant ring is assembled in order to examine the high-power transmission test. The window was tested up to the transmission power of 160 MW. The rf losses are also measured during the rf operation.  
 
THP61 SKIP - A Pulse Compressor for SuperKEKB coupling, linac, positron, resonance 754
 
  • T. Sugimura, M. Ikeda, K. Kakihara, T. Kamitani, S. Ohsawa, K. Yokoyama
    KEK, Ibaraki
  An upgrade of KEKB injector linac is planned. A main purpose of this upgrade is to increase injection energy of positrons from 3.5 GeV to 8.0 GeV for the SuperKEKB project. By a limitation of land area, our choice is to double an acceleration field utilizing a C-band accelerator structures instead of present S-band structures. Last year we developed C-band components such as accelerator structure, dummy load, 3 dB hybrid coupler, RF window, sub booster, modulator system, and so on. These components were assembled at a test stand and processed. This accelerator unit was installed in the beam line of injector linac and has been under operation. This summer we will install an RF pulse compressor system to the C-band accelerator unit. This paper reports the status of development of the RF pulse compressor system.  
 
THP71 First Experience with Dry-Ice Cleaning on SRF Cavities superconductivity, extraction, site 776
 
  • D. Reschke, A. Brinkmann
    DESY, Hamburg
  • G. Müller
    BUW, Wuppertal
  • D. Werner
    IPA, Stuttgart
  The surface of superconducting (s.c.) accelerator cavities must be cleaned from any kind of contaminations, like particles or chemical residues. Contaminations might act as centers for field emission, thus limiting the maximum gradient. Today's final cleaning is based on high pressure rinsing with ultra pure water. Application of dry-ice cleaning might result in additional cleaning potential. Dry-ice cleaning using the sublimation-impulse method removes particulate and film contaminations without residues. As a first qualifying step intentionally contaminated niobium samples were treated by dry ice cleaning. It resulted in a drastic reduction of DC field emission up to fields of 100 MV/m as well as in the reduction of particle numbers. The dry ice jet caused no observable surface damage. First cleaning tests on single-cell cavities showed Q-values at low fields up to 4x1010 at 1.8 K. Gradients up to 32 MV/m were achieved, but field emission still is the limiting effect. Further tests are planned to optimize the dry-ice cleaning technique.  
 
THP75 Superconducting Accelerating Structure with Gradient as 2 Times Higher as TESLA Structure coupling, linac, impedance 785
 
  • P. V. Avrakhov, V.E. Balakin
    PTC LPI, Protvino, Moscow Region
  A proposed new accelerating structure for TESLA is assumed to have an effective gradient 2 times more than existing 9-cell cavity. This structure is an interlaced combination of two side-cavity-coupled standing wave substructures with λ/4 cells length. Intercell coupling provides side-coupled cavities made from a special shape waveguide section. The high accelerating gradient is accomplished by 4 factors:
  1. The shortened accelerating cells have transit time factor 0.9 instead of 0.64 for conventional standing wave cells with λ/2 length.
  2. The side magnetic coupling has made it possible to reduce the cells beam aperture that reduce relation between the maximum surface field and the acceleration gradient.
  3. Stronger intercell coupling allows extending the accelerating cavity and improving a duty factor of linac.
  4. Availability of the side coupling elements enables to use them for power input and HOM-couplers. It reduces intercavity distance and enhances duty factor too.
 
 
THP95 Electro Polishing of Niobium Cavities at DESY cathode, synchrotron, electron 824
 
  • A. Matheisen, L. Lilje, H. Morales, B. Petersen, M. Schmoekel, N. Steinhau-Kühl
    DESY, Hamburg
  At DESY a facility for electro polishing (EP) of the super conducting (s.c.) TESLA/TTF cavities have been built and is operational since summer 2003. The EP infrastructure is capable to handle single-cell structures and the standard TESLA/ TTF nine-cell cavities. Several electro polishing processes have been made since and acceleration voltage up to 40 MV/m have been reached in nine cell structures. We report on measurements and experiences gained since 2003 as well as on handling procedures developed for the preparation of electro polished resonators. Specific data like heat production, variation of current density and bath aging will be presented. Another important point for reproducible results is the quality control of the electro polishing process. First quality control steps to be implanted in the EP procedure for large-scale production will be described.