LINAC 2004 - List of Keywords

A B C D E F G H I K L M O P Q R S T U V

vacuum

Paper	Title	Other Keywords	Page
MOP14	Development of Intense Beam Proton Linac in China	rfq, linac, proton, dipole	63
	S. Fu, S.X. Fang, H. Ouyang, S. Zhao IHEP Beijing, Beijing B. Cui, X. Guan CIAE, Beijing J. Fang, Z.Y. Guo PKU/IHIP, Beijing
	Study on intense beam proton linac was started about four years ago in a national program for the basic research on ADS in China. This ADS program is meant for the future development of the clean nuclear power generation. Another important application of HPPA for Chinese Spallation Neutron Source was also proposed recently in China, and it is financially supported by Chinese Academy of Sciences. In this paper, the research progress on intense beam proton linac in these two application fields will be outlined. It involves the test result of an high-current ECR proton source, construction status of a 3.5 MeV RFQ accelerator and the design of a DTL linac.

MOP16	The TRASCO-SPES RFQ	rfq, dipole, quadrupole, coupling	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	coupling, linac, 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.

MOP27	Commissioning of a 6 MeV X-Band SW Accelerating Guide	electron, linac, gun, injection	96
	Q. Jin, Y. Lin, X. Sun, X. Tao, D. Tong TSINGHUA, Beijing B. Chen, B. Sun, Y. Zou BIEVT, Beijing 100016
	A 6 MeV, X-band on-axis SW electron linear accelerating guide is being developed in Accelerator laboratory of Tsinghua University. It can be suitable for portable radiation therapy and radiography. The design, manufacture and high power test of the guide are given in this paper. The guide is 38 cm long and contains 25 accelerating cells with 24 coupling cells, operated in the π/2 mode. The RF power source is a pulsed magnetron at 9300 MHz with 1.5 MW peak power. The results of beam tests are following: the electron energy is more than 6 MeV at 50 mA and focal spot size is less than φ 1.5 mm without any focusing solenoid.

MOP49	Status And Operating Experience of The TTF Coupler	klystron, linac, superconductivity, free-electron-laser	156
	W.-D. Möller, D. Kostin DESY, Hamburg
	Five accelerating modules are installed in the VUV FEL linac so far. This includes 40 high power couplers connected to the superconducting cavities, eight in every module. All of them are processed and operated up to the cavity performance limits. The coupler processing procedure is described. The performance in relation to the test results on the coupler test stands are discussed.
	Transparencies

MOP77	Design Parameters of the Normal Conducting Booster Cavity for the PITZ-2 Test Stand	coupling, 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.

MOP82	SRF Cavity and Materials R&D at Fermilab	superconductivity, superconducting-RF, electron, emittance	213
	N. Khabiboulline, P. Bauer, L. Bellantoni, T. Berenc, C. Boffo, R. Carcagno, C. Chapman, H. Edwards, L. Elementi, M. Foley, E. Hahn, D. Hicks, D. Mitchell, A. Rowe, N. Solyak, I. Terechkine FNAL, Batavia, Illinois A. Gurevich, M. Jewell, D. C. Larbalestier, P. Lee, A. Polyanskii, A. Squitieri UW-Madison/ASC, Madison, Wisconsin
	Two 3.9 GHz superconducting RF cavities are under development at FNAL for use in the upgraded Photoinjector Facility. A TM110 mode cavity will provide streak capability for bunch slice diagnostics, and a TM010 mode cavity will provide linearization of the accelerating gradient before compression for better emittance. The status of these two efforts and a review of the FNAL infrastructure development will be given.

MOP85	Influence of Ta Content in High Purity Niobium on Cavity Performance: Preliminary Results*	electron, superconductivity, coupling	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/

MOP87	Conceptual Layout of the European X-FEL Linear Accelerator Cryogenic Supply	linac, booster, electron, superconducting-magnet	225
	B. Petersen, H. Lierl, A. Zolotov DESY, Hamburg
	As a source for the European x-ray free electron laser (European X-FEL project) at DESY a superconducting linear accelerator will deliver a pulsed electron beam of about 20 GeV. A conceptual layout for the cryogenic supply of the linac is presented. The linac will consist of about 1000 superconducting niobium 1.3 GHz 9-cell cavities, which will be cooled in a liquid helium bath at a temperature of 2 K. Eight cavities and one superconducting magnet package will be assembled to a cryomodule of 12.2 m length. The cryomodules are equipped with two thermal shields at a 5 K and 80 K temperature level respectively. The linac of about 1.6 km length will be divided in 10 cryogenic sub units. Each sub unit will consist of 12 cryomodules. In addition to the main linac, two injector sections have to be supplied separately by means of helium refrigerators and a related helium distribution system.

MOP89	A Wire Position Monitor System for the ISAC-II Cryomodule Components Alignment	alignment, linac, impedance, acceleration	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.

TU101	Engineering and Building RF Structures - The Works	rfq, linac, simulation, radio-frequency	237
	D. Schrage LANL, Los Alamos, New Mexico
	The translation of the physics designs of linear accelerators into engineering and manufacturing requirements is discussed. The stages of conceptual design, prototyping, final design, construction, and installation are described for both superconducting (LANL β = 0.175 Spoke Cavity) and normal-conducting (APT/LEDA 6.7 MeV RFQ) accelerators. An overview of codes which have linked accelerator cavity and thermal/structural analysis modules is provided.
	Transparencies

TU203	High Pressure, High Gradient RF Cavities for Muon Beam Cooling	emittance, radiation, simulation, collider	266
	R. P. Johnson, M. Popovic FNAL, Batavia, Illinois M.M. Alsharo'a, R.E. Hartline, M. Kuchnir, T.J. Roberts Muons, Inc., Batavia C. M. Ankenbrandt, A. Moretti Fermilab, Batavia, Illinois K. Beard, A. Bogacz, Y.S. Derbenev Jefferson Lab, Newport News, Virginia D. M. Kaplan, K. Yonehara IIT, Chicago, Illinois
	High intensity, low emittance muon beams are needed for new applications such as muon colliders and neutrino factories based on muon storage rings. Ionization cooling, where muon energy is lost in a low-Z absorber and only the longitudinal component is regenerated using RF cavities, is presently the only known cooling technique that is fast enough to be effective in the short muon lifetime. RF cavities filled with high-pressure hydrogen gas bring two advantages to the ionization technique: the energy absorption and energy regeneration happen simultaneously rather than sequentially, and higher RF gradients and better cavity breakdown behavior are possible than in vacuum due to the Paschen effect. These advantages and some disadvantages and risks will be discussed along with a description of the present and desired RF R&D efforts needed to make accelerators and colliders based on muon beams less futuristic.
	Transparencies

TU204	Effect of High Solenoidal Magnetic Fields on Breakdown Voltages of High Vacuum 805 MHz Cavities	collider, linac, factory, background	271
	A. Moretti, A.D. Bross, S. Geer, Z. Qian Fermilab, Batavia, Illinois D.M. Errede University of Illinois at Urbana-Champaign, Urbana, Illinois D. Li LBNL/AFR, Berkeley, California J. Norem ANL, Argonne, Illinois R.A. Rimmer Jefferson Lab, Newport News, Virginia Y. Torun IIT, Chicago, Illinois M.S. Zisman LBNL, Berkeley, California
	The demonstration of muon ionization cooling by a large factor is necessary to demonstrate the feasilibility of a collider or neutrino factory. An important cooling experiment, MICE [1], has been proposed to demonstrate 10 % cooling which will validate the technology. Ionization cooling is accomplished by passing a high-emittance beam in a multi-Tesla solenoidal channel alternately through regions of low Z material and very high accelerating RF Cavities. To determine the effect of very large solenoidal magnetic fields on the generations of Dark current, X-Rays and breakdown Voltage gradients of vacuum RF cavities, a test facility has been established at Fermilab in Lab G. This facility consists of a 12 MW 805 MHz RF station, and a large bore 5 T solenoidal superconducting magnet containing a pill box type Cavity with thin removable window apertures allowing dark current studies and breakdown studies of different materials. The results of this study will be presented. The study has shown that the peak achievable accelerating gradient is reduced by almost a factor two in a 4 T field. [1] http://mice.iit.edu/.
	Transparencies

TUP08	Carbon Ion Injector Linac for a Heavy Ion Medical Synchrotron	linac, rfq, ion, focusing	306
	D.A. Swenson LLC, Albuquerque, New Mexico
	The design of a Carbon Ion Injector Linac for a heavy ion medical synchrotron will be presented. The linac is designed to accelerate quadruply-ionized carbon ions (¹²C⁴⁺) with a charge/mass ratio (q/A) of 0.333, and all other ions with the same or higher charge/mass ratios, such as H¹⁺, H₂¹⁺, D¹⁺, T¹⁺, ³He¹⁺, ⁴He²⁺, ⁶Li²⁺, ¹⁰B⁴⁺, and ¹⁶O⁶⁺ to an output energy of 7 MeV/u. The 200 MHz linac consists of an Radio Frequency Quadrupole (RFQ) linac to accelerate the ions from an input energy of 0.008 MeV/u to an intermediate energy of 0.800 MeV/u, and an Rf-Focused Interdigital (RFI) linac to accelerate these ions to the output energy. The combined linac structures have a total length of 7.8 meters and a total peak rf power requirement of about 600 kW. The RFQ linac employs a radial-strut, four-bar design that is about twice as efficient as the conventional four-bar RFQ design. The RFI linac, which is basically an interdigital drift tube structure with rf quadrupole focusing incorporated into each drift tube, is about 5 times more efficient than the conventional Drift Tube Linac (DTL) structure. Details of the linac structures and their calculated performance will be presented.

TUP54	Resistive-Wall Wake Effect in the Beam Delivery System	single-bunch, focusing, impedance, linear-collider	393
	J. Wu SLAC, Menlo Park, California J. R. Delayen Jefferson Lab, Newport News, Virginia T.O. Raubenheimer SLAC/NLC, Menlo Park, California J.-M. Wang BNL/NSLS, Upton, Long Island, New York
	The resistive wall instability is investigated in the context of the final beam delivery system of linear colliders. The emittance growth is calculated analytically and compared against the results of full numerical simulations. Criteria for the design of final beam delivery systems are developed.

TUP72	TTF II Beam Monitors for Beam Position, Bunch Charge and Phase Measurements	undulator, pick-up, instrumentation, single-bunch	435
	M. Wendt, D. Nölle DESY, Hamburg
	An overview of the basic beam instrumentation with regard to elecromagnetic beam monitors for the TESLA Test Facility phase II (TTF II) is given. Emphasis is put on beam position monitor (BPM) and toroid transformer systems for beam orbit and bunch charge observations. Furthermore broadband monitors, i.e. wall current and bunch phase monitors, are briefly presented.

TUP84	Spectrographic Approach to Study of RF Conditioning Process in Accelerating RF Structures	RF-structure, plasma, quadrupole, electron	471
	H. Tomizawa, H. Hanaki, T. Taniuchi JASRI-SPring-8, Hyogo A. Enomoto, Y. Igarashi, S. Yamaguchi KEK, Ibaraki
	The acceleration gradient of a linac is limited by rf breakdown in its accelerating structure. We applied an imaging spectrograph system to study the mechanism of rf breakdown phenomena in accelerating rf structures. Excited outgases emit light during rf breakdown, and the type of outgases depend on surface treatments and rinsing methods for their materials. To study rf breakdown, we used 2-m-long accelerating structures and investigated the effects when high-pressure ultrapure water rinsing (HPR) treatment was applied to these rf structures. We performed experiments to study the outgases under rf conditioning with quadruple mass spectroscopy and imaging spectrography. As a result, we could observe instantly increasing signals at mass numbers of 2 (H₂), 28 (CO), and 44 (CO₂), but not 18 (H₂O) just after the rf breakdown. We also conducted spectral imaging for the light emissions from the atoms in a vacuum that are excited by rf breakdown. Without HPR, we observed the atomic lines at 511 nm (Cu I), 622 nm (Cu II), and 711 nm (C I). With HPR, 395 nm (O I), 459 nm (O II), 511 nm (Cu I), 538 nm (C I), 570 nm (Cu I), 578 nm (Cu I), 656 nm (H I), and 740 nm (Cu II) were observed.

TUP89	Static Absolute Force Measurement for Preloaded Piezoelements Used for Active Lorentz Force Detuning System	resonance, impedance, linac, linear-collider	486
	S. P. Sekalski, A. Napieralski, S. P. Sekalski TUL, Lodz A. Bosotti INFN/LASA, Segrate (MI) M. Fouaidy IPN, Orsay L. Lilje, S. Simrock DESY, Hamburg R. Paparella, P.F. Puricelli INFN Milano, Milano
	To reach high gradients in pulsed operation of superconducting (SC) cavities an active Lorentz force detuning compensation system is needed. For this system a piezoelement can be used as an actuator (other option is a magnetostrictive device). To guarantee the demanded lifetime of the active element, the proper preload force adjustment is necessary. To determine this parameter an absolute force sensor is needed which will be able to operate at cryogenic temperatures. Currently, there is no calibrated commercial available sensor, which will be able to measure the static force in such an environment. The authors propose to use a discovered phenomenon to estimate the preload force applied to the piezoelement. The principle of the proposed solution based on a shape of impedance curve, which changes with the value of applied force. Especially, the position of resonances are monitored. No need of specialized force sensor and measurement in-situ are additional advantages of proposed method.

TUP96	Mechanical Stability Simulations on a Quarter Wave Resonator for the SPIRAL II Project	simulation, acceleration, linac, 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.

TUP97	Some Estimations for Correlation Between the RF Cavity Surface Temperature and Electrical Breakdown Possibility	electron, simulation, photon	507
	V.V. Paramonov RAS/INR, Moscow
	The electrical breakdown in accelerating cavities is the complicated phenomenon and depends on many parameters. Some reasons for breakdown can be avoided by appropriate vacuum system design and the cavity surface cleaning. This case, for normal conducting accelerating cavities free electrons - the dark currents due to Fowler-Nordheim emission can be considered as the main reason of possible electrical breakdown. It is known from the practice - the combination of the high electric field at the cavity surface with high surface temperature is the subject for risk in the cavity operation. In this paper the dependence on the surface temperature is considered and 'effective' electric field enhancement is discussed.

TUP98	The Finite State Machine for Klystron Operation for VUV-FEL and European X-FEL Linear Accelerator	klystron, cathode, power-supply, bunching	510
	W. Cichalewski, B. Koseda, A. Napieralski TUL, Lodz F.-R. Kaiser, S. Simrock DESY, Hamburg
	In order to provide a pulsed RF power signal that fulfills all designers and users demands the work on power supplies, pulse transformers, waveguides and klystrons has to be well coordinated. Because operators not engineers will operate mention user facility therefore software has to be implemented in order to automate the enormous quantity of hardware operation accompanying regular operation of linear accelerator collider. A finite state machine is adequate formal description of reactive systems that has become starting point for designing our control software. To present the complexity of the task that establishing FSM for Klystron system would be, one has to become acquainted with complexity of the system itself. Therefore this article describes the construction and principles of the klystron and modulator as well as ideas concerning the implementation of a FSM for such a system.

WE101	Gradient Limitations for High-Frequency Accelerators	collider, linear-collider, plasma, linac	513
	S. Döbert SLAC, Stanford
	While the physics of gradient limitations in high frequency rf accelerators still lacks a full theoretical understanding, a fairly complete empirical picture has emerged from the experimental work done in the past few years to characterize this phenomenon.Experimental results obtained mostly in the framework of the NLC/GLC project at 11 GHz and from the CLIC study at 30 GHz will be used to illustrate the important trends.The dependence of achievable gradient on pulse length, operating frequency and fabrication materials will be described. Also, the performance results most relevant to linear colliders will be presented in some detail. Specifically, these relate to the requirements that the structures sustain a certain gradient without incurring damaged, and that more importantly, they run reliably at this gradient, with breakdown rates less one in a million pulses. Finally interesting observations concerning the dynamics of breakdowns like spatial and temporal correlations and dark currents will be covered briefly, including the insights they provide into the breakdown mechanism.
	Transparencies

TH104	Industrial RF Linac Experiences and Laboratory Interactions	linac, proton, site, electron	569
	M. Peiniger ACCEL, Bergisch Gladbach
	Since more than two decades ACCEL Instruments GmbH at Bergisch Gladbach (formerly Siemens/Interatom) is supplying the worldwide accelerator labs with key components like rf cavities and power couplers, s.c. magnets, insertion devices, vacuum chambers and x-ray beamline equipment. Starting with the design and production of turn key SRF accelerating modules in the late 80th, meanwhile ACCEL is engineering, manufacturing, on site commissioning and servicing complete accelerators with guaranteed beam performance. Today, with a staff of more than 100 physicists and engineers and about the same number of manufacturing specialists in our dedicated production facilities, ACCEL's know how and sales volume in this field has accumulated to more than 2000 man years and several hundred Mio €, respectively. Basis of our steady development is a cooperative partnership with the world leading research labs in the respective fields. As an example, for the supply of a turn key 100 MeV injector linac for the Swiss Light Source, and meanwhile also for the Diamond Light Source as well as for the Australian Synchrotron Project, we established a very fruitful partnership with DESY.
	Transparencies

THP04	Fabrication of Superconducting Cavities for SNS	electron, linac	602
	M. Pekeler, S. Bauer, J. Schwellenbach, M. Tradt, H. Vogel, P. vom Stein ACCEL, Bergisch Gladbach
	During the last three years ACCEL fabricated all 109 superconducting cavities for the Spallation Neutron Source (SNS) in Oakridge, Tennessee. Two series of 35 medium beta (β=0.61) and 74 high beta (β=0.81) cavities have been delivered. Besides cavity manufacturing ACCEL also performed rf tuning and chemical surface preparation. We give an outline on the current manufacturing experience and comment on future developments for industrial cavity production.
	Transparencies

THP05	Superconducting beta=0.15 Quarter-Wave Cavity for RIA	linac, superconductivity, ion, resonance	605
	M. Kelly ANL, Argonne, Illinois Z.A. Conway, J.D. Fuerst, M. Kedzie, K.W. Shepard ANL/Phys, Argonne, Illinois
	A production-design 115 MHz niobium quarter-wave cavity with a full stainless steel helium jacket has been built and tested as part of the R&D for the Rare Isotope Accelerator (RIA) driver linac. The two-gap cavity is designed to accelerate ions over the velocity range 0.14<β<0.24. Processing of the cavity RF surfaces, including high-pressure rinsing and assembly of the cavity with a moveable high-power RF coupler were all performed under clean room conditions. Cold test results including high-field cw operation, microphonics, and helium pressure sensitivity will be presented in this paper. Performance of a pneumatically actuated slow-tuner device suitable not only for this cavity but a number of other cavities required for RIA will also be discussed.

THP06	Cold Tests of a Superconducting Co-Axial Half-Wave Cavity for RIA	linac, superconductivity, resonance, proton	608
	M. Kelly ANL, Argonne, Illinois J.D. Fuerst, M. Kedzie, K.W. Shepard ANL/Phys, Argonne, Illinois
	This paper reports cold tests of a superconducting niobium half-wave cavity with integral helium vessel, the design of which is suitable for production for the Rare Isotope Accelerator (RIA) driver linac. The cavity operates at 172 MHz and can provide more than 2 MV of accelerating voltage per cavity for ions with 0.24<β<0.37. Cavity RF surfaces were prepared using electropolishing, high-pressure rinsing and clean assembly. Measurements of Q₀ show a residual RF surface resistance RS = 5 nΩs in both 2 K and 4 K operations. The cavity can be operated at 4.5 K with E_Acc >10 MV/m (E_Peak >30 MV/m). Performance exceeds RIA specifications of an input power of 12 Watts at 4.5 K and E_Acc = 6.9 MV/m. RMS frequency jitter is only 1.6 Hz at E_Acc = 8 MV/m and T = 4.5 K as determined from microphonics measurements in a realistic accelerator environment connected to the ATLAS refrigerator.
	Transparencies

THP10	Tuner Design for High Power 4-Rod-RFQs	rfq, linac, simulation, ion	617
	A. Schempp, L. Brendel, B. Hofmann, H. Liebermann IAP, Frankfurt-am-Main
	The performance of high power RFQ linacs, as used in spallations sources and proposed for projects like ADxy, IFMIF or high duty factor drivers for RIB application are limited by beam dynamics properties as well as technical limits like sparking, power density, cooling and thermal stresses. A "one piece structure" even possible in theory has to have means for tuning the real fields like exchangable or moving tuners. Tuner design features will be discussed and results will be presented.

THP13	Construction of a 161 MHz, β=0.16 Superconducting Quarter Wave Resonator with Steering Correction for RIA	light-ion, linac, emittance, ion	626
	A. Facco INFN/LNL, Legnaro, Padova C. Compton, T.L. Grimm, W. Hartung, F. Marti, R.C. York NSCL, East Lansing, Michigan V. Zvyagintsev TRIUMF, Vancouver
	We have built a 161 MHz, β=0.16 superconducting Quarter Wave Resonator with steering correction for the low beta section of RIA. This bulk niobium, double wall cavity, compatible with both separate vacuum between beam line and cryostats or unified one, was designed in collaboration between MSU-NSCL and LNL. The design is suitable for extension to other frequencies, e.g. to obtain the 80 MHz, β=0.085 cavity required in RIA. The shaped drift tube allows correction of the residual QWR steering that can cause emittance growth especially in light ions; this could make this resonator a good alternative to Half-Wave resonators in high intensity proton-deuteron linacs, like the SPES injector project at LNL. First test results will be presented.

THP16	Engineering and Cryogenic Testing of the ISAC-II Medium Beta Cryomodule	alignment, target, linac, heavy-ion	630
	G. Stanford, Y. Bylinskii, R.E. Laxdal, B. Rawnsley, T. Ries, I. Sekatchev TRIUMF, Vancouver
	The medium beta section of the ISAC-II Heavy Ion Accelerator consists of five cryomodules each containing four quarter wave bulk niobium resonators and one superconducting solenoid. A prototype cryomodule has been designed and assembled at TRIUMF. The cryomodule vacuum space contains a mu-metal shield, an LN2 cooled, copper, thermal shield, plus the cold mass and support system. This paper will describe the design goals, engineering choices and fabrication and assembly techniques as well as report the results of the initial cold tests. In particular we will summarize the alignment procedure and the results from the wire position monitoring system.

THP23	An Electrode With Molybdenum-Cathode and Titanium-Anode to Minimize Field Emission Dark Currents	cathode, electron, ion, feedback	645
	T. Nakanishi, F. Furuta, T. Gotou, M. Kuwahara, K. Naniwa, S. Okumi, M. Yamamoto, N. Yamamoto, K. Yasui DOP Nagoya, Nagoya H. Matsumoto, M. Yoshioka KEK, Ibaraki K. Togawa RIKEN Spring-8 Harima, Hyogo
	A systematic study to minimize field emission dark currents from high voltage DC electrode has been continued. It is clearly demonstrated that much lower field emissions observed for Molybdenum (Mo) and Titanium (Ti) in comparison to Stainless-steel and Copper. Furthermore, by analyzing gap-length dependence data of the dark current from Mo and Ti, we can find a method to separate the primary field emission currents (FEC) from secondary induced currents (SIC). The latter currents will be created by possible bombardments of metal surface of anode or cathode by electrons or positive ions, respectively. From this data analysis, it is suggested that Mo is suitable for cathode due to its smallest FEC, and Ti is adequate for anode due to relatively small SIC. This prediction was confirmed by our experiment using a pair of Mo and Ti electrode, which showed the total dark current is suppressed below 1 nA at 105 MV/m applied for an area of 7 mm² with a gap-length of 1.0 mm. Therefore this Mo-Ti electrode seems useful for a high field gradient DC gun, especially for a GaAs-photocathode gun using an NEA (Negative Electron Affinity) surface.

THP25	Development of Field-Emission Electron Gun from Carbon Nanotubes	cathode, electron, acceleration, 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.

THP30	Production of S-band Accelerating Structures	linac, coupling, 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.

THP34	A High-Power Test of an X-Band Molybdenum-Iris Structure	klystron, linear-collider, collider, linac	678
	W. Wuensch, A. Grudiev, T. Heikkinen, I. Syratchev, T. Taborelli, I. Wilson CERN, Geneva C. Adolphsen SLAC/NLC, Menlo Park, California S. Döbert SLAC, Stanford
	In order to achieve accelerating gradients above 150 MV/m, alternative materials to copper are being investigated by the CLIC study. The potential of refractory metals has already been demonstrated in tests in which a tungsten-iris and a molybdenum-iris structure reached 150 and 193 MV/m respectively (30 GHz and a pulse length of 15 ns). In order to extend the investigation to the pulse lengths required for a linear collider, a molybdenum-iris structure scaled to X-band was tested at the NLCTA. The structure conditioned to only 65 MV/m (100 ns pulse length) in the available testing time and much more slowly than is typical of a copper structure. However the structure showed no sign of saturation and a microscopic inspection of the rf surfaces corroborated that the structure was still at an early stage of conditioning. The X-band and 30 GHz results are compared and what has been learned about material quality, surface preparation and conditioning strategy is discussed.
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THP38	High Precision Survey and Alignment of Large Linear Accelerators	alignment, survey, simulation, target	690
	J. Prenting, M. Schlösser DESY, Hamburg J. Green, G. Grzelak, A. Mitra, A. Reichold OXFORDphysics, Oxford, Oxon A. Herty CERN, Geneva
	For the future linear accelerator TESLA the demanded accuracy for the alignment of the components is 0.5 mm horizontal and 0.2 mm vertical, both on each 600 m section. Other accelerators require similar accuracies. These demands can not be fulfilled with open-air geodetic methods, mainly because of refraction. Therefore the RTRS (Rapid Tunnel Reference Surveyor), a measurement train performing overlapping multipoint alignment on a reference network is being developed. Two refraction-free realizations of this concept are being developed at the moment: the first one (GeLiS) measures the horizontal co-ordinates using stretched wires, combined with photogrammetric split-image sensors in a distance measurement configuration. In areas of the tunnel where the accelerator is following the earth curvature GeLiS measures the height using a new hydrostatic leveling system. The second concept (LiCAS) is based on laser straightness monitors (LSM) combined with frequency scanning interferometry (FSI) in an evacuated system. LiCAS measures both co-ordinates with respect to its LSM-beam and is thus suitable for geometrically straight tunnel sections. Both measurement systems will be placed on a train, which could do the reference survey autonomously.

THP42	NLC Hybrid Solid State Induction Modulator	klystron, induction, pulsed-power, controls	697
	R.L. Cassel, M. Nguyen, G.C. Pappas, J.E. deLamare SLAC, Stanford C. Brooksby, E. Cook, J. Sullivan LLNL, Livermore
	The Next Linear Collider accelerator proposal at SLAC requires a high efficiency, highly reliable, and low cost pulsed power modulator to drive the X-band klystrons. The original NLC envisions a solid state induction modulator design to drive up to 8 klystrons to 500 kV for 3 μs at 120 PPS with one modulator delivering greater than 1,000 MW pulse, at 500 kW average. A change in RF compression techniques resulted in only two klystrons needed pulsing per modulator at a reduced pulse width of 1.6 μsec or approximately 250 MW of the pulsed power and 80 kW of average powers. A prototype Design for Manufacturability (DFM) 8-pack modulator was under construction at the time of the change, so a redirection of modulator design was in order. To utilities the equipment which had already be fabricated, a hybrid modulator was designed and constructed using the DFM induction modulator parts and a conventional pulse transformer. The construction and performance of this hybrid two klystron Induction modulator will be discussed. In addition the next generation DFM induction modulator utilizing a ten turn secondary and fractional turn primary transformer well be presented.

THP43	Reduction of RF Power Loss Caused by Skin Effect	simulation, electromagnetic-fields	700
	Y. Iwashita Kyoto ICR, Kyoto
	RF current flows only on a metal surface with very thin skin depth, which decreases with RF frequency. Thus the surface resistance increases with the frequency. Because the skin depth also decreases when the metal conductivity increases, the improvement of the conductivity does not contribute much; it is only an inverse proportion to the square root of the conductivity. Recently, it is shown that such a power loss can be reduced on a dielectric cavity with thin conductor layers on the surface, where the layers are thinner than the skin depth. Some possibilities to implement the idea and to extend the application to general cavities and transmission lines will be discussed.

THP54	Moscow Meson Factory DTL RF System Upgrade	rfq, coupling, 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.

THP56	Control of the Low Level RF System for J-Parc Linac	klystron, linac, feedback, proton	739
	S. Michizono, S. Anami, E. Kadokura, S. Yamaguchi KEK, Ibaraki E. Chishiro, T. Kobayashi, .H. Suzuki JAERI, Ibaraki-ken
	A low level RF (LLRF) system for J-Parc linac generates RF and clock signals, drives a klystron, and stabilizes accelerating fields in the cavities. The LLRF system is controlled by two units: a programmable logic controller (PLC) and a compact PCI (cPCI) controller. Functions of the PLC are ON/OFF and UP/DOWN controls, and STATUS and ANALOG monitors. The PLC is locally operated by a touch panel, and remotely operated by an EPICS IOC with Ethernet communication. The cPCI controller is for RF feedback and feed-forward controls, including a cavity tuner control, and then, locally and remotely operated by communication with the PLC. On the other hand, RF waveform data, which are stored in the memory of DSP and CPU boards in the cPCI, are directory transmitted to an EPICS OPI by a request from EPICS.

THP58	Development of C-band High-Power Mix-Mode RF Window	resonance, klystron, acceleration, 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.

THP60	High-Power RF Distribution System for the 8-Pack Project	linear-collider, collider, diagnostics, resonance	751
	C.D. Nantista SLAC/ARDB, Menlo Park, California D.P. Atkinson LLNL, Livermore J.Q. Chan SLAC/NLC, Menlo Park, California S.Y. Kazakov KEK, Ibaraki D.C. Schultz SLAC, Menlo Park, California S.G. Tantawi SLAC/ARDA, Menlo Park, California
	The 8-Pack Project at SLAC is a prototype rf system whose goal is to demonstrate the high-power X-band technology developed in the NLC/GLC program. In its first phase, it has reliably produced a 400 ns rf pulse of over 500 MW using a solid-state modulator, four 11.424 GHz klystrons and a dual-moded SLED-II pulse compressor [1]. In Phase 2, the output power of our system has been delivered into the bunker of the NLCTA (Next Linear Collider Test Accelerator) and divided between several accelerating structures, first four and finally eight, for beam acceleration. We describe here the design, cold-test measurements, and processing of this power distribution system. Due to the high power levels and the need for efficiency, overmoded waveguide and components are used. For power transport, the TE 01 mode is used in 7.44 cm and 4.064 cm diameter circular waveguide. Only near the structures is standard WR90 rectangular waveguide employed. Components used to manipulate the rf power include transitional tapers, mode converters, overmoded bends, fractional directional couplers, and hybrids. [1] S. Tantawi, et al., “Status of High-Power Tests of the Dual-Mode SLED-II System for an X-Band Linear Collider,” FR202, these proceedings.

THP65	Low-Power RF Tuning of the Spallation Neutron Source Warm LINAC Structures	coupling, linac, pick-up, target	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	coupling, 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.

THP70	Experimental Study of an 805 MHz Cryomodule for the Rare Isotope Accelerator	linac, resonance, alignment, coupling	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)

THP72	A Newly Designed and Optimized CLIC Main Linac Accelerating Structure	damping, luminosity, linac, dipole	779
	A. Grudiev, W. Wuensch CERN, Geneva
	A new CLIC main-linac accelerating-structure design, HDS (Hybrid Damped Structure), with improved high-gradient performance, efficiency and simplicity of fabrication is presented. The gains are achieved in part through a new cell design which includes fully-profiled rf surfaces optimized to minimize surface fields and hybrid damping using both iris slots and radial waveguides. The slotted irises allow a simple structure fabrication in quadrants with no rf currents across joints. Further gains are achieved through a new structure optimization procedure, which simultaneously balances surface fields, power flow, short and long-range transverse wakefields, rf-to-beam efficiency and the ratio of luminosity to input power. The optimization of a 30 GHz structure with a loaded accelerating gradient of 150 MV/m results in a bunch spacing of eight rf cycles and 29% rf-to-beam efficiency. The dependencies of performance on operating frequency, accelerating gradient, and phase advance per cell are shown.

THP82	Experiences in Fabrication and Testing the Prototype of the 4.90 GHz Accelerating Sections for MAMI C	coupling, 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
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THP94	Cold Tests of a 160 MHz Half-Wave Resonator	resonance, linac, coupling, simulation	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	linear-collider, collider, linac, coupling	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