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Paper Title Other Keywords Page
MOP16 The TRASCO-SPES RFQ rfq, vacuum, dipole, quadrupole 69
 
  • A. Pisent, M. Comunian, J. Esposito, A. Palmieri
    INFN/LNL, Legnaro, Padova
  • E. Fagotti
    INFN Milano, Milano
  • G. Lamanna
    CINEL, Vigonza (PD)
  • M. S. Mathot
    CERN, Geneva
  A high intensity RFQ is under construction at LNL. Developed within TRASCO research program, the Italian feasibility study an ADS (Accelerator Driven System), it will be employed as the first accelerating element of SPES facility, the ISOL project of LNL. The RFQ operates at the frequency of 352 MHz in CW mode, is able to deliver a proton current up to 30 mA and consists of six brazed segments whose length is 1.2 m. In this article the results obtained from the construction of a 20 cm “technological model”, aimed at testing the construction procedure of the final structure, will be discussed. Finally we will report about the machining and the outcomes obtained after RF testing of the first two segments built up to now.  
 
MOP18 Cold-Model Tests and Fabrication Status for J-PARC ACS linac, vacuum, alignment, simulation 75
 
  • H. Ao, H. Akikawa
    JAERI/LINAC, Ibaraki-ken
  • K. Hasegawa, A. Ueno
    JAERI, Ibaraki-ken
  • N. Hayashizaki
    TIT, Tokyo
  • M. Ikegami, S. Noguchi
    KEK, Ibaraki
  • V.V. Paramonov
    RAS/INR, Moscow
  • Y. Yamazaki
    J-PARC, Ibaraki-ken
  The J-PARC (Japan Proton Accelerator Research Complex) LINAC will be commissioned with energy of 181-MeV using 50 keV ion source, 3 MeV RFQ, 50 MeV DTL and 181 MeV SDTL (Separated DTL) on September 2006. It is planed to be upgraded by using 400 MeV ACS (Annular Coupled Structure), which is a high-beta structure most suitable for the J-PARC, in a few years from the commissioning. The first ACS cavity, which will be used as the first buncher between the SDTL and the ACS, is under fabrication. Detailed design and tuning procedure of ACS cavities has been studied with RF simulation analysis and cold-model measurements. The results of cold-model measurements, fabrication status, and related development items are described in this paper.  
 
MOP24 Using a Solid State Switch for a 60kV Bouncer to Control Energy Spread during the Beam Pulse* linac, synchrotron, impedance, power-supply 87
 
  • L. Donley, J.C. Dooling, G.E. McMichael, V. F. Stipp
    ANL, Argonne, Illinois
  The beam injected into the IPNS Linac is from a column utilizing a Cockcroft-Walton voltage source. The accelerating column consists of a single high gradient gap. To lessen the likelihood of gap voltage breakdown, we pulse (“bounce”) the column voltage up during the beam pulse allowing the column DC voltage to be lower. The accelerating voltage is supplied through a 5 MΩ resistor and has only small capacitance to hold the voltage constant during the beam pulse. A capacitor is connected between the high voltage end of the column and the bouncer pulse generator. The bouncer pulse increases the column voltage to the proper level just microseconds before the beam pulse. A slope on the top of the bouncer pulse allows for correction to be added, compensating for the voltage droop that results from beam loading. The bouncer that has served this purpose in the past utilized a tube amplifier. In searching for a suitable replacement system it was decided that the system should be able to deliver a 60 kV pulse and the slope on the top of the pulse could be controlled by an RC rise. A solid state switch was purchased for this application. Switch protection and other design decisions will be discussed.  
 
MOP35 The Research of a Novel SW Accelerating Structure with Small Beam Spot electron, photon, focusing, target 114
 
  • X. Yang, H. Chen, Y. Chen, X. Jin, M. Li, H. Lu, Z. Xu
    CAEP/IAP, Mianyang, Sichuan
  A new kind of on-axis coupled biperiodic standing-wave (SW) accelerating structure has been built for a 9 MeV accelerator. The research progress was introduced in this paper, it includes the choice of the accelerating structure, the analysis of electron beam dynamics, the tuning of the cavity, the measurement of the accelerating tube and the powered test. The small beam spot is the most interesting feature of this accelerating structure, the diameter of the beam spot is 1.4 mm. This accelerator has been used for the x photons generation and the x-ray dose rate is about 3400 rad/min/m.  
 
MOP63 Numerical Calculation of Coupling Impedances in Kicker Modules for Non-Relativistic Particle Beams simulation, impedance, kicker, synchrotron 162
 
  • B. Doliwa, T. Weiland
    TU Darmstadt, Darmstadt
  In the context of heavy-ion synchrotrons, coupling impedances in ferrite-loaded structures (e.g. fast kicker modules) are known to have a significant influence on beam stability. While bench measurements are feasible today, it is desirable to have the coupling impedances in hands already during the design process of the respective components. To achieve this goal, as a first step, we have carried out numerical analyses of simple ferrite-containing test systems within the framework of the Finite Integration Technique[1]. This amounts to solving the full set of Maxwell's equations in frequency domain, the particle beam being represented by an appropriate excitation current. With the resulting electromagnetic fields, one may then readily compute the corresponding coupling impedances. Despite the complicated material properties of ferrites, our results show that their numerical treatment is possible, thus opening up a way to determine a crucial parameter of kicker devices before construction.

[1] Weiland, T., Electronics and Communication (AEÜ), Vol. 31 (1977), p. 116.

 
 
MOP65 Simple Theory of Thermal Fatigue Caused by RF Pulse Heating 168
 
  • S. Kuzikov
    IAP, Nizhniy Novgorod
  The projects of electron-positron linear colliders imply that accelerating structures and other RF components will undergo action of extremely high RF fields. Except for breakdown threat there is an effect of the damage due to multi-pulse mechanical stress caused by Ohmic heating of the skin layer. A new theory of the thermal fatigue is considered. The theory is based on consideration of the quasi-elastic interaction between neighbor grains of metal due to the expansion of the thermal skin-layer. The developed theory predicts a total number of the RF pulses needed for surface degradation in dependence on temperature rise, pulse duration, and average temperature. The unknown coefficients in the final formula were found, using experimental data obtained at 11.4 GHz for the copper. In order to study the thermal fatigue at higher frequencies and to compare experimental and theoretical results, the experimental investigation of degradation of the copper cavity exposed to 30 GHz radiation is carried out now, basing on a 30 GHz free electron maser.  
 
MOP66 Calculation of RF Properties of the Third Harmonic Cavity dipole, scattering, higher-order-mode, quadrupole 171
 
  • K. Rothemund, D. Hecht, U. van Rienen
    Rostock University, Faculty of Engineering, Rostock
  Recently a third harmonic structure has been proposed for the injector of the TTF-FEL to avoid nonlinear distortions in the longitudinal phase space. This structure, consists of four nine cell TESLA-like cavities. For the use of this structure in combination with the TTF-FEL it might be interesting to investigate higher order modes (HOM) in the structure and their effect on the beam dynamics. The complexity of the structure, four nine cell cavities assembled with four input couplers and eight HOM-couplers, results in an extremely high numerical effort for full 3D modelling. Therefor Coupled S-Parameter Calculation (CSC) [1] has been applied. This method is based on the scattering parameter description of the rf components found with field solving codes or analytically for components of special symmetry. This paper presents the results of the calculation of rf properties (e.g. scattering parameters, Q-values) of the complete four times nine cell structure equipped with all input- and HOM-couplers.

[1] H.-W. Glock, K. Rothemund, U. van Rienen, CSC - A Procedure for Coupled S-Parameter Calculations, IEEE Trans. Magnetics, vol. 38, pp. 1173 - 1176, March 2002

 
 
MOP70 A Pass Band Performance Simulation Code of Coupled Cavities simulation, linac, RF-structure, beam-loading 183
 
  • X. Tao, D. Tong
    TSINGHUA, Beijing
  A simulation code of accelerating cavities named PPSC is developed by the solutions of the microwave equivalent circuit equations. PPSC can give the pass band performance of periodic or non-periodic accelerating structures, such as the dispersion frequency and the reflection factor of the cavity, the field distribution of each mode and so on. The natural parameters of the structure, such as the number of the cavities, the resonant frequencies and Q-factors of each cavity, the coupling factor between two cavities, and the locations of the couplers, can be changed easily to see the different results of the simulation. The code is written based on MS Visual Basic under MS windows. With these, a user-friendly interface is made. Some simple examples was simulated and gave reliable results.  
 
MOP77 Design Parameters of the Normal Conducting Booster Cavity for the PITZ-2 Test Stand vacuum, booster, gun, emittance 204
 
  • V.V. Paramonov, N.I. Brusova, A.I. Kvasha, A. Menshov, O.D. Pronin, A.K. Skasyrskaya, A.A. Stepanov
    RAS/INR, Moscow
  • A. Donat, M. Krasilnikov, A. Oppelt, F. Stephan
    DESY Zeuthen, Zeuthen
  • K. Flöttmann
    DESY, Hamburg
  The normal conducting booster cavity is intended to increase the electron bunch energy in the Photo Injector Test (DESY, Zeuthen) stage 2 experiments. The normal conducting cavity is selected due to infrastructure particularities. The L-band cavity is designed to provide the accelerating gradient up to 14 MV/m with the total input RF power 8.6 MW, RF pulse length up to 900 mks and repetition rate 5 Hz. The multi-cell cavity is based on the CDS compensated accelerating structure with the improved coupling coefficient value. The main design ideas and decisions are described briefly together with cavity parameters - RF properties, cooling and pumping circuits.  
 
MOP84 First Cryogenic Tests with JLab's new Upgrade Cavities* damping, impedance, pick-up, higher-order-mode 216
 
  • P. Kneisel, G. Ciovati, G. Myneni, G. Wu
    Jefferson Lab, Newport News, Virginia
  • J. Halbritter
    FZ Karlsruhe, Karlsruhe
  • J. Sekutowicz
    DESY, Hamburg
  For the upgrade of CEBAF to 12 GeV two types of 7-cell cavities have been developed: the High Gradient type (HG) has been optimized with respect to the ratio of Epeak/Eacc and for the Low Loss (LL) type the shunt impedance has been maximized. Each cavity type features four DESY type coaxial HOM couplers and a waveguide input coupler. Design goals for these cavities have been set to Eacc = 20 MV/m with a Q-value at 2.05 K of Q0 = 8·109. A niobium prototype of each cavity has been fabricated at JLab and in a first test the HG cavity has been evaluated at cryogenic temperatures after appropriate buffered chemical polishing. Data for Q(E) were taken at several temperatures after R(T) was measured during initial pump down. In addition the pressure sensitivity as well as the Lorentz force detuning were evaluated. The damping of approximately 20 High Order Modes was measured to verify the room temperature data. Measurements on the LL prototype are in progress. We present in this contribution a summary of measured results of tests we performed on the new proposed shapes of the upgrade cavities.  
 
MOP85 Influence of Ta Content in High Purity Niobium on Cavity Performance: Preliminary Results* vacuum, electron, superconductivity 219
 
  • P. Kneisel, G. Myneni
    Jefferson Lab, Newport News, Virginia
  • T. Carneiro
    RMC, Bridgeville
  • M. Imagumbai
    CBMM, Tokyo
  • Chr. Klinkenberg
    NPC, Düsseldorf
  • D. Proch, W. Singer, X. Singer
    DESY, Hamburg
  In a previous paper* a program designed to study the influence of the residual tantalum content on the superconducting properties of pure niobium metal for RF cavities was outlined. The main rationale for this program was based on a potential cost reduction for high purity niobium, if a less strict limit on the chemical specification for Ta content, which is not significantly affecting the RRR–value, could be tolerated for high performance cavities. Four ingots with different Ta contents have been melted and transformed into sheets. In each manufacturing step the quality of the material has been monitored by employing chemical analysis, neutron activation analysis, thermal conductivity measurements and evaluation of the mechanical properties. The niobium sheets have been scanned for defects by an eddy current device. From three of the four ingots—Ta contents 100, 600 and 1,200 wppm—two single cell cavities each of the CEBAF variety have been fabricated and a series of tests on each cavity with increasing amount of material removal have been performed. This contribution reports about the results from different tests and gives an analysis of the data.

*T. Carneiro et al; http://conference.kek.jp/SRF2001/

 
 
MOP86 Cold Test Results of the ISAC-II Medium Beta High Gradient Cryomodule alignment, acceleration, 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 simulation, acceleration, 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.  
 
MOP92 Simulation of the RF Coupler for TRIUMF ISAC-II Superconducting Quarter Wave Resonators simulation, impedance, cryogenics, acceleration 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.  
 
TUP02 Development of a 352 MHz Cell-Coupled Drift Tube Linac Prototype linac, quadrupole, focusing, alignment 288
 
  • M. Vretenar, Y. Cuvet, J. Genest, C. Völlinger
    CERN, Geneva
  • F. Gerigk
    CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon
  At linac energies above 40 MeV, alternative structures to the conventional Drift Tube Linac can be used to increase efficiency and to simplify construction and alignment. In the frame of the R&D activities for the CERN SPL and Linac4, a prototype of Cell-Coupled Drift Tube Linac (CCDTL) at 352 MHz has been designed and built. This particular CCDTL concept is intended to cover the energy range from 40 to 90 MeV and consists of modules of ~5 m length made of 3 or 4-gap DTL tanks linked by coupling cells. The focusing quadrupoles are placed between tanks, and are aligned independently from the RF structure. The CCDTL prototype consists of two half tanks connected by a coupling cell and requires an RF power of 120 kW to achieve the design gradient. RF tests will be made at low and high power, the latter up to a 20% duty cycle. This paper introduces the main features of this CCDTL design, describes the RF and mechanical design of the prototype and presents the first measurement results.  
 
TUP06 Results of the High-Power Conditioning and the First Beam Acceleration of the DTL-1 for J-PARC linac, rfq, acceleration, 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.  
 
TUP20 Some Relevant Aspects in the Design and Construction of a 30-62 MeV Linac Booster for Proton Therapy proton, linac, cyclotron, booster 336
 
  • V.G. Vaccaro, S. Falco
    Naples University Federico II, Mathematical, Physical and Natural Sciences Faculty, Napoli
  • A. D'Elia
    Naples University Federico II, Napoli
  • D. Davino
    Universita' degli Studi del Sannio, Benevento
  • M.R. Masullo
    INFN-Napoli, Napoli
  Recent results in accelerator physics showed 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. This suggested to design a linac booster able to increase the proton energy up to 62 MeV as required for treating tumours like the ocular ones. In this paper we will review the rationale of the project; we will discuss the basic design of a compact 3 GHz SCL (Side Coupled Linac) with a new approach to the linac cavities. Among the many challenges of such a project one of the most interesting is the tuning of the cavities. Because the tuning can be done only after assembling the system, it is difficult to detect which cavities are responsible for the detuning: indeed the resonant behavior of single cavity is lost since the resonances merge into the resonant modes of the whole system. It is shown how, from the measured mode frequencies of the system, it is possible to derive the unknown resonances of each cavity and then refine the tuning. The proposed procedure is quite general and is not restricted to the SCL.  
 
TUP50 Cumulative Beam Breakup with Time-Dependent Parameters focusing, injection, linear-collider, dipole 384
 
  • J. R. Delayen
    Jefferson Lab, Newport News, Virginia
  A general analytical formalism developed recently for cumulative beam breakup (BBU) in linear accelerators with arbitrary beam current profile and misalignments [1] is extended to include time-dependent parameters such as energy chirp or rf focusing in order to reduce BBU-induced instabilities and emittance growth. Analytical results are presented and applied to practical accelerator configurations.

[1] J. R. Delayen, Phys. Rev. ST Accel. Beams 6, 084402 (2003)

 
 
TUP80 A Long-Pulse Modulator for the TESLA Test Facility (TTF) klystron, cathode, linac, linear-collider 459
 
  • W. Kaesler
    PPT, Dortmund
  The long-pulse (1.6 ms) klystron modulator for TTF is a hardtube pulser using a Bouncer-circuit for droop compensation. It is built up with new advanced components representing industrial standards. The on-/off switch is a rugged 12 kV IGCT-stack with a fast 4kA turn-off capability. The 100 kJ storage capacitor bank contains only three capacitors with self-healing, segmented PP-foil technology. A new 100 kA solid-state switch based on light triggered thyristors (LTT) replaced the standard ignitrons as crowbar switches. The 300 kW high voltage power supply is based on modern switched mode technology.  
 
TUP86 Coupler Development and Gap Field Analysis for the 352 MHz Superconducting CH-Cavity quadrupole, linac, simulation, proton 477
 
  • 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 s.c. multi-cell structures ranging from the RFQ exit energy up to the injection energy into elliptical multi-cell cavities. The reasonable frequency range is from about 150 MHz up to 800 MHz. A 19-cell, β=0.1, 352 MHz, bulk niobium prototype cavity is under development at the ACCEL-Company, Bergisch-Gladbach. This paper will present detailed MicroWave Studio simulations and measurements for the coupler development of the 352 MHz superconducting CH cavity. It will describe possibilities for coupling into the superconducting CH-Cavity. The development of the coupler is supported by measurement on a room temperature CH-copper model. We will present the first results of the measurements of different couplers, e.g. capacitive and inductive couplers, at different places of the CH Cavity.  
 
TUP93 Results of a 3D-EM-Code Comparison on the TRISPAL Cavity Benchmark simulation, resonance, rfq 495
 
  • P. Balleyguier
    CEA/DAM, Bruyères-le-Châtel
  Several 3D electromagnetic codes (MAFIA, CST MicroWave-Studio, Vector-Fields Soprano, Ansoft HFSS, SLAC Omega3P) have been tested on a 2-cell cavity benchmark. Computed frequencies and Q-factors were compared to experimental values measured on a mock-up, putting the emphasis on the effect of coupling slots. It comes out that MAFIA limitations due to the staircase approximation is overcome by all other codes, but some differences still remain for losses calculations in re-entrant corners  
 
TUP96 Mechanical Stability Simulations on a Quarter Wave Resonator for the SPIRAL II Project simulation, acceleration, linac, vacuum 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.  
 
WE102 State of the Art SRF Cavity Performance damping, linac, electron, higher-order-mode 518
 
  • L. Lilje
    DESY, Hamburg
  The paper will review superconducting RF cavity performance for β=1 cavities used in both linear and circular accelerators. These superconducting cavities are used in two kinds of applications: High current storage rings and efficient high duty cycle linacs. In recent years the performance of those cavities has been improving steadily. High accelerating gradients have been achieved using advanced surface preparation techniques like electropolishing and surface cleaning methods like high pressure water rinsing. High intensity beams can be handled with advanced higher-order-mode damping schemes.  
Transparencies
 
THP28 Multi-Mode SLED-II Pulse Compressors resonance 660
 
  • S. Kuzikov, Y.Y. Danilov, G. G. Denisov, V. G. Paveliev, D. Yu. Shegol'kov, A. A. Vikharev
    IAP, Nizhniy Novgorod
  • I. Syratchev
    CERN, Geneva
  Compact SLED-II pulse compressors are considered. The primary idea of S. Kazakov to use a set of the cylindrical multi-mode cavities, to be free of high-Q resonances around the 11.4 GHz, is analyzed. This idea is developed, in order to provide more delaying time per miter of the line. Another idea to provide compactness is to avoid two-channel scheme with 3 dB coupler usually used for SLED-II pulse compressors. A reflectionless delay line is built in this case, using coupling in a form of the non-symmetrical mode converter. SLED-II pulse compressors of higher frequency bands also are considered. It is suggested to shape these compressors on a base of the multi-mirror transmission lines. The operating mode in this case is a Gaussian wavebeam traveling between mirrors. Various configurations of the mirrors are compared from the point of view of maximum of compactness at the given pulse duration. The results of the preliminary experiments at low power level are discussed.  
Transparencies
 
THP29 Development of C-band Accelerating Section for SuperKEKB acceleration, linac, positron, klystron 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.  
 
THP30 Production of S-band Accelerating Structures linac, vacuum, target, microtron 666
 
  • C. Piel, K. Dunkel, H. Vogel, P. vom Stein
    ACCEL, Bergisch Gladbach
  ACCEL currently produces accelerating structures for several scientific laboratories. Multi-cell cavities at S-band frequencies are required for the projects CLIC-driver-linac, DLS and ASP pre-injector linac and the MAMI-C microtron. Based on those projects differences and similarities in design, production technologies and requirements will be addressed.  
 
THP31 A Four-Cell Periodically HOM-Damped RF Cavity for High Current Accelerators damping, acceleration, 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.  
 
THP41 Development of High RF Power Delivery System for 1300 MHz Superconducting Cavities of Cornell ERL Injector alignment, insertion, superconductivity, linac 694
 
  • S.A. Belomestnykh, M. Liepe, V. Medjidzade, H. Padamsee, V. Veshcherevich
    LEPP, Ithaca, New York
  • N.P. Sobenin
    MEPhI, Moscow
  Development of a 150 kW CW RF power delivery system for 1300 MHz superconducting cavities is under way at Cornell University in collaboration with MEPhI. The system is based on a twin-coupler consisting of two identical coaxial antenna-type couplers derived from the TTF-3 input coupler design. Because the average power is much higher than in the TTF-3 coupler, the required coupling is stronger and we wanted to avoid multipacting phenomena, major changes were made to the prototype design. Presented coupler has completely redesigned cold part and significantly improved cooling of warm bellows. The results of thermal and mechanical stress calculations are reported. The magnitudes and phases of RF fields applied to each side of the twin-coupler must be very close to each other. This imposes very strict requirements upon a power dividing system. These requirements and proposed layout of a system satisfying them are discussed.  
 
THP44 The Design and Performance of the Spallation Neutron Source Low-Level RF Control System linac, controls, feedback, klystron 703
 
  • M. Champion, M. Crofford, K. Kasemir, H. Ma, C. Piller
    ORNL/SNS, Oak Ridge, Tennessee
  • L. Doolittle, C. Lionberger, M. Monroy, A. Ratti
    LBNL, Berkeley, California
  • J. Power, H. Shoee
    LANL, Los Alamos, New Mexico
  The Spallation Neutron Source linear accelerator low-level RF control system has been developed within a collaboration of Lawrence Berkeley, Los Alamos, and Oak Ridge national laboratories. Three distinct generations of the system, described in a previous publication [1], have been used to support beam commissioning at Oak Ridge. The third generation system went into production in early 2004, with installation in the coupled-cavity and superconducting linacs to span the remainder of the year. The final design of this system will be presented along with results of performance measurements.

[1] M. Champion, et al, "The Spallation Neutron Source Accelerator Low Level RF Control System", Proceedings of the PAC2003 Conference, Portland, Oregon.

 
 
THP51 Tuning of External Q And Phase for The Cavities of A Superconducting Linear Accelerator impedance, scattering, linac, resonance 724
 
  • V.V. Katalev, S. Choroba
    DESY, Hamburg
  The RF power required for a certain gradient of a superconducting cavity depends on the beam current and coupling between the cavity and waveguide. The coupling with the cavity may be changed by variation of Qext. Different devices can be used to adjust Qext or phase. In this paper three stub and E-H tuners are compared and their usability for the RF power distribution system for the superconducting accelerator of the European Xray laser and the TESLA linear collider is considered. The tuners were analyzed by using the scattering matrix. Advantages and limitations of the devices are presented.  
 
THP54 Moscow Meson Factory DTL RF System Upgrade rfq, vacuum, dipole, impedance 733
 
  • A.I. Kvasha
    RAS/INR, Moscow
  The last paper devoted to description of the first part (DTL) RF system of Moscow Meson Factory upgrade was published in the Proceedings of PAC95 Conference in Dallas. Since then some new works directed at improvement of reliability and efficiency of the RF system were carried out. Among them there are a new powerful pulse triode “Katran” installed in the output RF power amplifiers (PA) of three channels, modifications of the anode modulator control circuit and crow-bar system, a new additional RF channel for RF supply of RFQ and some alterations in placing of the anode modulator equipment decreasing a level of interference’s at crow-bar circuits. Some new checked at MMF RF channels ideas concerning of PA tuning are of interest for people working in this sphere of activity.  
 
THP61 SKIP - A Pulse Compressor for SuperKEKB linac, acceleration, 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.  
 
THP64 Waveguide Stub Tuner Analysis for CEBAF Application klystron, simulation, insertion, resonance 757
 
  • H. Wang
    Jefferson Lab, Newport News, Virginia
  • M. Tiefenback
    TJNAF, Newport News, Virginia
  Three-stub WR650 waveguide tuners have been used on the CEBAF superconducting cavities for two changes on the external Qs: increasing the Q from 6·106 to 8·106 on 5-cell cavities to reduce the klystron power at operation gradients and decreasing the Q from 2·107 to 8·106 on 7-cell cavities to ease the control system handling the Lorenz Force detuning. To understand the reactive tuning effects in the machine operations with beam current and mechanical tuning, a network analysis model was developed. The S parameters of the stub tuner were simulated by MAFIA and measured on the bench. We used this stub tuner model to study tuning range, sensitivity, frequency pulling as well as cold waveguide and window heating problems. Detailed experimental results will be compared against this model. Pros and cons of this stub tuner application will be summarized.  
 
THP65 Low-Power RF Tuning of the Spallation Neutron Source Warm LINAC Structures linac, pick-up, target, vacuum 760
 
  • C. Deibele, G. Johnson
    ORNL, Oak Ridge
  • J. Billen, N.K. Bultman, J. Stovall
    LANL, Los Alamos, New Mexico
  • J. Error, P. Gibson
    ORNL/SNS, Oak Ridge, Tennessee
  • J. Manolitsas, D. Trompetter
    ACCEL, Bergisch Gladbach
  • A. Vasyuchenko
    RAS/INR, Moscow
  • L. Young
    TechSource, Santa Fe, NM
  The Spallation Neutron Source (SNS) is an accelerator-based neutron source being built at Oak Ridge National Laboratory. A conventional 402.5 MHz drift-tube linac (DTL) accelerates the beam from 2.5 to 86 MeV, and the 805 MHz coupled-cavity linac (CCL) continues acceleration to 186 MeV. Tuning the six DTL tanks involves adjusting post-coupler lengths and slug tuners to achieve the design resonant frequency and stabilized field distribution. A 2.5 MW klystron feeds RF power into each DTL tank through a ridge-loaded waveguide that does not perturb either the frequency or field distribution in the tank. The CCL consists of 4 RF modules operating in the βλ/2 mode. Each module contains 96 accelerating cavities in 12 segments of 8 cavities each, 11 active bridge coupler cavities, and 106 nominally unexcited coupling cavities. For each RF module, power from a single 5 MW klystron splits once and drives bridge couplers 3 and 9. We will discuss the special tools and measurement techniques developed for the low-power tuning activities.  
 
THP67 Traveling Wave and Standing Wave Single Cell High Gradient Tests vacuum, linear-collider, simulation, collider 766
 
  • V.A. Dolgashev
    SLAC/ARDB, Menlo Park, California
  • Y. Higashi, T. Higo
    KEK, Ibaraki
  • C.D. Nantista, S.G. Tantawi
    SLAC/ARDA, Menlo Park, California
  Accelerating gradient is one of the crucial parameters affecting design, construction and cost of next-generation linear accelerators. Operating accelerating gradient in normal conducting accelerating structures is limited by rf breakdown. In this paper we describe an experimental setup for study of these limits for 11.4 GHz traveling-wave and standing-wave accelerating structures. The setup uses matched mode converters that launch the circular TM01 mode and short test structures. The test structures are designed so that the electromagnetic fields in one cell mimic the fields in prototype structures for the Next Linear Collider. Fields elsewhere in the test structures and in the mode converters are significantly lower then in this single cell. This setup allows economic testing of different cell geometries, cell materials and preparation techniques with short turn around time. In this paper we present design considerations and initial experimental data.  
 
THP69 The Tuning Study of the Coupled Cavities for the RF Chopper System of J-PARC simulation, linac, proton, insertion 770
 
  • S. Wang, S. Fu
    IHEP Beijing, Beijing
  • T. Kato
    KEK, Ibaraki
  A 3 MeV medium-energy beam transport line (MEBT) is located between RFQ and DTL in the linac of the Japan Proton Accelerator Research Complex (J-PARC). MEBT accomplishes beam matching and chopping. An rf deflector (RFD), which is a heavily loaded cavity, was adopted as a chopper in J-PARC linac for chopping 500 μs long macropulses from the ion source into sub-pulses for injecting into the following 3 GeV rapid-cycling ring. A coupled RFD system was proposed in the design of chopper system for saving the cost of rf power source. The tuning of the coupled RFD system was successfully performed. The longer rise time of the second RFD and the delay of the second RFD excitation were found during the tuning of the coupled RFD system, and these phenomena were further analyzed and investigated. Both in the high power and beam tests, the chopper worked well without any discharge under 36 kW peak driving power.  
 
THP70 Experimental Study of an 805 MHz Cryomodule for the Rare Isotope Accelerator linac, vacuum, resonance, alignment 773
 
  • T.L. Grimm, S. Bricker, C. Compton, W. Hartung, M. Johnson, F. Marti, J. Popielarski, R.C. York
    NSCL, East Lansing, Michigan
  • G. Ciovati, P. Kneisel
    Jefferson Lab, Newport News, Virginia
  • L. Turlington
    TJNAF, Newport News, Virginia
  The Rare Isotope Accelerator (RIA) driver linac will use superconducting, 805 MHz, 6-cell elliptical cavities with geometric β values of 0.47, 0.61 and 0.81. Each elliptical cavity cryomodule will have four cavities [1]. Room temperature sections between each cryomodule will consist of quadrupole doublets, beam instrumentation, and vacuum systems. Michigan State University (MSU) has designed a compact cryostat that reduces the tunnel cross-section and improves the linac real estate gradient. The cold mass alignment is accomplished with a titanium rail system supported by adjustable nitronic links from the top vacuum plate, and is similar to that used for existing MSU magnet designs. The same concept has also been designed to accommodate the quarter-wave and half-wave resonators with superconducting solenoids used at lower velocity in RIA. Construction of a prototype β=0.47 cryomodule was completed in February 2004 and is presently under test in realistic operating conditions. Experimental results will be presented including: alignment, electromagnetic performance, frequency tuning, cryogenic performance, low-level rf control, and control of microphonics.

[1] “Cryomodule Design for the Rare Isotope Accelerator”, T.L. Grimm, M. Johnson and R.C. York, PAC2003, Portland OR (2003)

 
 
THP75 Superconducting Accelerating Structure with Gradient as 2 Times Higher as TESLA Structure linac, impedance, acceleration 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.
 
 
THP82 Experiences in Fabrication and Testing the Prototype of the 4.90 GHz Accelerating Sections for MAMI C vacuum, resonance, microtron, linac 788
 
  • A. Jankowiak, H. Euteneuer, S. Schumann, O. Tchoubarov
    IKP, Mainz
  The fourth stage of the Mainz Microtron (MAMI) is under construction as a 855 to 1500 MeV Harmonic Double Sided Microtron[1], with one of its two linacs operating at the MAMI-frequency of 2.45 GHz, the other at 4.90 GHz. The bi-periodic on axis coupled accelerating structure in operation at MAMI has been optimised for 4.90 GHz[2], such a high frequency till now not having been used for high power cw-acceleration. To ensure a smooth and efficient industrial production of the ten 35 AC-sections needed, a prototype was built and high power tested fully in-house at IKPH. After a short recapitulation of the design of the cavity profile, the configuration of the section with its tuners and diagnostic probes is discussed. Details of the procedures of machining, tuning and brazing the resonator discs, and the rf-parameters achieved for the section are given. Finally, the experiences and measurements during its high power test up to 22 kW are reported: the conditioning behaviour and the irreversible permanent as well as the reversible dynamic changes of passband gap and resonance frequency as a function of maximal applied rf-power.

[1] A. Jankowiak et al., "Design and Status of the 1.5 GeV-Harmonic Double Sided Microtron for MAMI", Proceedings EPAC2002, [2] H. Euteneuer et al., "The 4.90GHz Accelerating structure for MAMI C", Proceedings EPAC2000

 
Transparencies
 
THP83 Measurements of High Order Modes in High Phase Advance Damped Detuned Accelerating Structure for NLC dipole, linear-collider, collider, controls 791
 
  • N. Khabiboulline, T. Arkan, H. Carter
    FNAL, Batavia, Illinois
  • G. Linder
    University of Illinois at Urbana-Champaign, Urbana, Illinois
  • G. Romanov
    Fermilab, Batavia, Illinois
  The RF Technology Development group at Fermilab is working together with the NLC and JLC groups at SLAC and KEK on developing technology for room temperature X-band accelerating structures for a future linear collider. We have built several series of structures for high gradient tests. We have also built 150° phase advance per cell, 60 cm long, damped and detuned structures (HDDS or FXC series). Some of these structures will be used for the 8-pack test at SLAC by the end of 2004, as part of the JLC/NLC effort to demonstrate the readiness of room temperature RF technology for a linear collider. HDSS structures are very close to the final design for the linear collider, and it was very interesting to study the properties of high order modes in the structures produced by semi-industrial methods. In this study advanced RF technique and methods developed at Fermilab for structure low power testing and tuning have been used. The results of these measurements are presented in this paper.  
 
THP84 Design of a 300 GHz Broadband TWT Coupler and RF-Structure simulation, RF-structure, electron, plasma 794
 
  • F.L. Krawczyk, F.E. Sigler
    LANL/LANSCE, Los Alamos, New Mexico
  • B.E. Carlsten, L.M. Earley
    LANL, Los Alamos, New Mexico
  • J.M. Potter
    JP Accelerator Works, Inc., 2245, Los Alamos, NM
  • M.E. Schulze
    GA, Los Alamos
  • E. Smirnova
    MIT/PSFC, Cambridge, Massachusetts
  Recent LANL activities in millimeter wave structures focus on 94 and 300 GHz structures. They aim at power generation from low power (100–2000 W) with a round electron beam (120 kV, 0.1–1.0 A) to high power (2–100 kW) with a sheet beam structure (120 kV, 20 A). Applications cover basic research, radar and secure communications and remote sensing of biological and chemical agents. In this presentation the design and cold-test measurements of a 300 GHz RF-structure with a broadband (>6% bandwidth) power coupler are presented. The design choice of two input/output waveguides, a special coupling region and the structure parameters themselves are presented. As a benchmark also a scaled up version at 10 GHz was designed and measured. These results will also be presented.  
 
THP85 Test Results of the 3.9 GHz Cavity at Fermilab damping, emittance, linear-collider, collider 797
 
  • N. Solyak, I. Gonin
    Fermilab, Batavia, Illinois
  • L. Bellantoni, T. Berenc, H. Edwards, M. Foley, N. Khabiboulline, D. Mitchell, A. Rowe
    FNAL, Batavia, Illinois
  Fermilab is developing two types of 3.9 GHz superconducting cavities to improve performances of A0 and TTF photoinjectors. In frame of this project we have built and tested two nine-cell copper models and one 3-cell niobium accelertating cavity and series of deflecting cavities. Properties of the high order modes were carefully studied in a chain of two copper cavities at room temperature. High gradient performance were tested at helium temperature. Achieved gradients and surface resistances are exceed goal parameters. In paper we discuss results of cold tests of the 3-cell accelerating and deflecting cavities.  
 
THP90 The Technique for the Numerical Tolerances Estimations in the Construction of Compensated Accelerating Structures booster, linac, proton, survey 812
 
  • V.V. Paramonov, A.K. Skasyrskaya
    RAS/INR, Moscow
  The requirements to the cells manufacturing precision and tining in the multi-cells accelerating structures construction came from the required accelerating field uniformity, based on the beam dynamics demands. The standard deviation of the field distribution depends on accelerating and coupling modes frequencies deviations, stop-band width and coupling coefficient deviations. These deviations can be determined from 3D fields distribution for accelerating and coupling modes and the cells surface displacements. With modern software it can be done separately for every specified part of the cell surface. Finally, the cell surface displacements are defined from the cell dimensions deviations. This technique allows both to define qualitatively the critical regions and to optimize quantitatively the tolerances definition.  
 
THP92 Effect of the Tuner on the Field Flatness of SNS Superconducting RF Cavities simulation, resonance, superconducting-RF, pick-up 815
 
  • A. Sun
    ORNL/SNS, Oak Ridge, Tennessee
  • H. Wang, G. Wu
    Jefferson Lab, Newport News, Virginia
  Field flatness in a multi-cell superconducting cavity affects not only the net accelerating voltage, but also the peak surface field and the Lorenz Force detuning coefficient. Our measurement indicates that the field flatness changes both external Q of the Fundamental Power Coupler (FPC) and external Q of the Field Probe (FP). The field amplitude tilts linearly to the distance between the cell center and the cavity’s geometry center (pivot point). The tilt rate has been measured in a cryomodule cold (2 K) test, being about 2%/100 kHz, relative the field flatness at the cavity’s center frequency of 805 MHz. Bead-pull measurements confirmed that the field flatness change is 2.0%/100 kHz for a medium β cavity with helium vessel, and 1.72%/100 kHz without helium vessel. These results matched the predictions of simulations using ANSYS and SUPERFISH. A detailed analysis reveals that longitudinal capacitive gap deformation is the main cause of the frequency change. Field flatness change was not only due to the uneven stored energy change within the cell, but also due to cell-to-cell coupling.  
 
THP94 Cold Tests of a 160 MHz Half-Wave Resonator resonance, linac, simulation, vacuum 821
 
  • R. Stassen, R. Maier
    FZJ/IKP, Jülich
  • R. Eichhorn, F. M. Esser, B. Laatsch, G. Schug, H. Singer
    FZJ, Jülich
  The number of polarized particle in the cooler synchrotron COSY is limited by the present injector system. A new linac was projected based on superconductive half-wave resonators to fill COSY up to the space charge limit. The first prototype of a 160 MHz Half-Wave Resonator (HWR) has been built and tested. RF-measurements in CW as well as in a pulsed operation will be presented. A second prototype with a slightly different way of fabrication will be completed soon. All measurements have been done using the new 4 kW loop-coupler. The use of a cold window allows to change the coupling from 1· 106 to 1· 1010 without any risk of contamination. The mechanical tuner consisting of a stepper motor driven coarse tuner and a fast piezo system to compensate the Lorentz-Force detuning has successfully integrated into the vertical test-cryostat.  
 
FR202 Status of High-Power Tests of Dual Mode SLED-II System for an X-Band Linear Collider vacuum, linear-collider, collider, linac 852
 
  • S.G. Tantawi
    SLAC/ARDA, Menlo Park, California
  • V.A. Dolgashev, C.D. Nantista
    SLAC/ARDB, Menlo Park, California
  We have produced 400 ns rf pulses of greater than 500 MW at 11.424 GHz with an rf system designed to demonstrate technology capable of powering a TeV scale electron-positron linear collider. Power is produced by four 50 MW X-band klystrons run off a common 400 kV solid-state modulator. We present the layout of our system, which includes a dual-moded transmission waveguide system and a dual-moded resonant-line (SLED-II) pulse compression system. Dual-moding of the transmission lines allows power to be directed through a pulse compression path or a bypass path; dual-moding in the pulse compressor allows the delay lines to be about half as long as they otherwise would need to be. We describe the design and performance of various components, including hybrids, directional couplers, power dividers, tapers, mode converters, and loads. These components are mostly overmoded to allow for greater power handling. We also present data on the processing and operation of this system. The power from that system is transported to feed a set accelerator structure. We will present the design and the high power testing data for the overmoded transfer line and the distribution network.  
Transparencies