LINAC 2004 - List of Sessions

THP — Thursday Poster Session (19-Aug-04 15:30—17:30)

Paper	Title	Page
THP03	DESIGN IMPROVEMENT OF THE RIA 80.5 MHZ RFQ	599
	Q. Zhao, V. Andreev, M. Doleans, D. Gorelov, T.L. Grimm, W. Hartung, F. Marti, S.O. Schriber, X. Wu, R.C. York NSCL, East Lansing, Michigan
	An 80.5 MHz, continuous-wave, normal-conducting, radio-frequency quadrupole (RFQ) was designed for the front end of the Rare Isotope Accelerator (RIA) driver linac. It will accelerate various ion beams (hydrogen up to uranium) from 12 keV/u to about 300 keV/u. The 4-meter-long RFQ accepts the pre-bunched beam from the low energy beam transport (LEBT) and captures more than 80% with a current of ~0.3 mA. Beam dynamics simulations show that the longitudinal output emittance is small for both single^- and two-charge-state ion beams with an external multi-harmonic buncher. A 4-vane resonator with magnetic coupling windows was employed in the cavity design to provide large mode separation, high shunt impedance, and a small transverse dimension. The results of beam dynamics as well as the electromagnetic simulations are presented.
THP04	Fabrication of Superconducting Cavities for SNS	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	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	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
THP07	Performance Improvement of the Multicell Cavity Prototype for Proton LINAC Projects	611
	B. Visentin, D. Braud, J.P. Charrier, B. Coadou, Y. Gasser, J.P. Poupeau, P. Sahuquet CEA/DSM/DAPNIA, Gif-sur-Yvette S. Bousson, H. Gassot, H. Saugnac, P. Szott IPN, Orsay G. Devanz CEA/DAPNIA-SACM, Gif-sur-Yvette Cedex
	The CEA-Saclay/IPN-Orsay collaboration allowed to develop a multicell superconducting cavity prototype (704 MHz, β=0.65). Since the first experimental results[], achieved in a vertical cryostat and the horizontal one "CryHoLab", the accelerating field Eacc has been recently improved up to 19 MV/m (E_peak = 43 MV/m, B_peak = 83 mT, Q₀ = 9.109). E_acc is now limited by quench. The previous one limitation, due to a non understood phenomenon, disappeared . The excellent performances of this 5-cell proton cavity validate the design, the technological choices, the manufacturing and the cavity preparation process. These results augur well for our future R&D program on multicell superconducting cavities within the European CARE/HIPPI framework. [] Proceedings of PAC2003, Portland, USA, TAB047, p.1303**
THP08	The Frankfurt Funneling Experiment	614
	A. Schempp, U. Bartz, N. Müller, J. Thibus, H. Zimmermann IAP, Frankfurt-am-Main
	Funneling is a procedure to multiply beam currents of rf-accelerators at low energies. In the ideal case the beam current can be multiplied in several stages without emittance growth. The Frankfurt Funneling Experiment consists of two ion sources, a Two-Beam RFQ accelerator, two different funneling deflectors and a beam diagnostic equipment system. The whole set-up is scaled for He⁺ instead of Bi⁺ for the first funneling stage of a HIIF driver. The progress of our experiment and the results of the simulations will be presented.
THP10	Tuner Design for High Power 4-Rod-RFQs	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.
THP11	Design of A 352 MHz-Proton-RFQ for GSI	620
	A. Schempp, L. Brendel, B. Hofmann IAP, Frankfurt-am-Main
	Part of the future project of GSI is a new p-linac for the production of Antiprotons. The 4- Rod-RFQ operating at 350 MHz has to accelerate up to 100 mA protons from an ECR source. Design studies have been made using the Parmteq- and Microwave Studio codes to optimize beam dynamics properties and the field distribution of the RFQ. Results of the design studies will be presented.
THP12	Superconducting RFQs in the PIAVE Injector	623
	G. Bisoffi, G. Bassato, G. Bezzon, A. Calore, S. Canella, F. Chiurlotto, A. Lombardi, P. Modanese, A.M. Porcellato, S. Stark INFN/LNL, Legnaro, Padova
	The PIAVE superconducting RFQs were installed on the linac line and connected to the TCF50 cryogenic system. First results on the on-line resonator performance (e.g. Q-curves, amplitude and phase locking) are described as well as the behaviour of the fast tuners.
THP13	Construction of a 161 MHz, β=0.16 Superconducting Quarter Wave Resonator with Steering Correction for RIA	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.
THP14	High Beta Cavity Optimization for ISAC-II	627
	R.E. Laxdal, V. Zvyagintsev TRIUMF, Vancouver Z.H. Peng CIAE, Beijing
	The linac for ISAC-II comprises twenty cavities of medium beta (β=5.8 and 7.1%) quarter wave cavities now in the installation phase. A second stage will see the installation of ~20 MV of high beta quarter wave cavities (~10.4%). The cavity structure choice depends on the efficiency of operation, cost, stability, beam dynamics and schedule. Two main cavity types are considered; a low frequency 106 MHz option and a high frequency 141 MHz cavity. We compare and contrast the cavity choices.
THP16	Engineering and Cryogenic Testing of the ISAC-II Medium Beta Cryomodule	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.
THP17	Progress in the Development of the TOP Linac	633
	L. Picardi, C. Ronsivalle ENEA C.R. Frascati, Frascati (Roma) S. Frullani ISS, Rome
	The TOP Linac (Oncological Therapy with Protons), under development by ENEA and ISS is a sequence of three pulsed (5 msec, 300 Hz) linear accelerators: a 7 MeV, 425 MHz RFQ+DTL (AccSys Model PL-7), a 7–65 MeV, 2998 MHz Side Coupled Drift Tube Linac (SCDTL) and a 65–200 MeV, variable energy 2998 MHz Side Coupled Linac (SCL). The first SCDTL module is composed by 11 DTL tanks coupled by 10 side cavities. The tanks has modified to overcome vacuum leakage that occurred during brazing, and now the module has been completed, and is ready to be tested with protons. The 7 MeV injector has been recently installed in the ENEA Frascati laboratories for preliminary test, before being transferred to the main Oncologycal Hospital in Rome, Istituto Regina Elena.
	Transparencies
THP18	The Acceleration Test of the APF-IH-LINAC	636
	K. Yamamoto, M. Okamura RIKEN, Saitama T. Hattori TIT, Tokyo S. Yamada NIRS, Chiba-shi
	We manufactured an IH linac with Alternating Phase Focusing as a test machine for medical accelerator injection. It will accelerate C⁴⁺ ions from 40 keV/u up to 2 MeV/u. The tank length is around 1.5 m, operation frequency is 100 MHz. We have succeeded to accelerate protons with a simple acceleration system, consisting of a PIG ion source, bending magnets and focus lenses, less than 5m long. This IH linac was calculated using a simple thin lens approximation. Now we are making a beam-tracking program using the results of the electro-magnetic simulation soft (Micro-Wave-Studio, OPERA-3D); it has the merit of easily calculating the 3D-beam dynamics including non-linear effects. We will report the test, the beam simulations and comparisons of the test to the simulations.
THP21	Calculation of Electron Beam Dynamics of the LUE-200 Accelerator	639
	A.P. Sumbaev, V. Alexandrov, N.Y. Kazarinov, V.F. Shevtsov JINR, Dubna, Moscow Region
	The results of calculations of the focusing and transportation systems of the electron beam of LUE-200 accelerator – the driver of a pulse source of resonant neutrons IREN, JINR (Dubna), are presented. Simulations of the beam dynamics in the traveling wave accelerator were carried out by means of PARMELA code. The calculations have been fulfilled for various parameters of the focusing magnetic fields in the accelerator and the channel, various currents of the beam and various initial distributions of electrons.
THP22	3D Beam Dynamics Simulation in Undulator Linac	642
	E.S. Masunov, S.M. Polozov MEPhI, Moscow
	The ion beam can be bunched and accelerated in linear accelerator with RF undulator (UNDULAC-RF). The acceleration and focusing of beam can be realized without using a synchronous wave. In this paper the computer simulation of high intensity ion beam dynamics in UNDULAC-RF was carried out by means of the "superparticles" method. The computer simulation and optimization of ion dynamics consist of two steps. At the first, the equations of particles motion in polyharmonic fields are devised by means of smooth approximation. Hamiltonian analysis of these equations allows to find a velocity of reference particle in polyharmonic field and to formulate the conditions of good longitudinal bunching and transverse focusing beam. At the second, the 3D ion beam dynamics simulation in an UNDULAC is governed by founded functions of reference particle velocity and a ratio of amplitude harmonics. The influence of the space charge on RF focusing conditions, transmission coefficient, longitudinal and transverse emittances, and other acceleration system characteristics are investigated by computer simulation. Masunov E.S., Sov. Phys.-Tech. Phys., vol. 35, No. 8, p. 962, 1990.
THP23	An Electrode With Molybdenum-Cathode and Titanium-Anode to Minimize Field Emission Dark Currents	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.
THP24	Highly Polarized Electrons from GaAs-GaAsP and InGaAs-AlGaAs Strained Layer Superlattice Photocathodes	648
	T. Nakanishi, F. Furuta, M. Kuwahara, K. Naniwa, T. Nishitani, S. Okumi, N. Yamamoto, K. Yasui DOP Nagoya, Nagoya H. Horinaka, T. Matsuyama OPU, Osaka H. Kobayakawa, Y. Takashima, Y. Takeda, O. Watanabe DOE Nagoya, Nagoya-City
	GaAs-GaAsP strained layer superlattice photocathode has been developed for highly polarized electron beams. This cathode achieved a maximum polarization of 92% with a quantum efficiency of 0.5%. Criteria for achieving the highest polarization together with high quantum efficiency using superlattice photocathodes are discussed based on experimental spin-resolved quantum efficiency spectra of GaAs-AlGaAs, InGaAs-AlGaAs and GaAs-GaAsP superlattice structures.
THP25	Development of Field-Emission Electron Gun from Carbon Nanotubes	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.
THP26	Comparison of 2 Cathode Geometries for High Current (2 kA) Diodes	654
	N. Pichoff CEA/DAM, Bruyères-le-Châtel F. Bombardier, M. Caron, E. Merle, C. Noël, O. Pierret, R. Rosol, C. Vermare CEA, Pontfaverger-Moronvilliers D.C. Moir LANL, Los Alamos, New Mexico A. Piquemal CEA/PTN, Bruyères-le-Châtel
	AIRIX (FRANCE) and DARHT axis-1 (USA) are two high current accelerators designed for flash X-ray radiography. The electron beam produced (2 kA, 3.5 to 3.8 MV, 60 ns) is extracted from a velvet cold cathode. Specific calculations have demonstrated the influence of the cathode geometry on the emitted beam profile [1]. To check this assumption we have made two different experiments (DARHT March 2003 – AIRIX March 2004). We have compared the beam characteristics with two different geometries both theoretically and experimentally. The beam simulations have been done with 3 codes: a home-made code (M2V) and 2 commercial codes (PBGUNS and MAGIC). The extracted beam current and transverse profiles, for the first experiment, have been measured and compared to simulations results. In the second one, we have compared the beam’s extracted current and the energy spread. [1] E. Merle et al., "Efforts to Improve Intense Linear Induction Accelerator (LIA) Sources for Flash Radiography",Proceedings of the LINAC2002 conference. August 19-23, 2002 Gyeongju, Korea.
THP27	Ultra Low Emittance Electron Gun Project for FEL Application	657
	R. Ganter, M. Dehler, J. Gobrecht, C. Gough, G. Ingold, S. Leemann, M. Paraliev, M. Pedrozzi, J.-Y. Raguin, L. Rivkin, V. Schlott, A. Streun, A. Wrulich PSI, Villigen A. Candel, K. Li ETH, Zürich
	Most of the current 1Å Free-Electron Laser (FEL) projects are based on thermionic or photocathode guns aiming at an electron beam emittance of 0.5 to 1 mm·mrad. The design of a gun capable of producing a beam with an emittance one or two order of magnitude lower than the state of the art would reduce considerably the cost and size of such a FEL. Due to the recent advances in nanotechnologies and vacuum microelectronics, a field-emitter based gun is a promising alternative scheme. We present first measurements on commercial field emitter arrays as well as 3-D numerical simulations of the electron beam dynamics for typical bunch distributions generated from field emitters in realistic gun geometries. The design and some experimental results on a 500kV pulser is also presented.
	Transparencies
THP28	Multi-Mode SLED-II Pulse Compressors	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	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	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	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.
THP32	New Accelerating Modules RF Test at TTF	672
	D. Kostin DESY, Hamburg
	Five new accelerating modules were installed into the TTF tunnel as a part of the VUV FEL Linac. They are tested prior to the linac operation. The RF test includes processing of the superconducting cavities, as well as maximum module performance tests. The test procedure and the achieved performance together with the test statistical analysis are presented.
THP33	Progress toward NLC/GLC Prototype Accelerator Structures	675
	J. Wang, G. Bowden, V.A. Dolgashev, R.M. Jones, J. Lewandowski, C.D. Nantista, S.G. Tantawi SLAC/ARDA, Menlo Park, California C. Adolphsen, D.L. Burke, J.Q. Chan, J. Cornuelle, S. Döbert SLAC/NLC, Menlo Park, California T. Arkan, C. Boffo, H. Carter, N. Khabiboulline FNAL, Batavia, Illinois N. Baboi DESY, Hamburg D. Finley, I. Gonin, S. Mishra, G. Romanov, N. Solyak Fermilab, Batavia, Illinois Y. Higashi, T. Higo, T. Kumi, Y. Morozumi, N. Toge, K. Ueno KEK, Ibaraki Z. Li, R. Miller, C. Pearson, R.D. Ruth, P.B. Wilson, L. Xiao SLAC, Menlo Park, California
	The accelerator structure groups for NLC (Next Linear Collider) and GLC (Global Linear Colliders) have successfully collaborated on the research and development of a major series of advanced accelerator structures based on room-temperature technology at X-band frequency. The progress in design, simulation, microwave measurement and high gradient tests are summarized in this paper. The recent effort in design and fabrication of the accelerator structure prototype for the main linac is presented in detail including HOM (High Order Mode) suppression and couplers, fundamental mode couplers, optimized accelerator cavities as well as plans for future structures. We emphasize techniques to reduce the field on the surface of the copper structures (in order to achieve high accelerating gradients), limit the dipole wakefields (to relax alignment tolerance and prevent a beam break up instability) and improve shunt impedance (to reduce the RF power required).
THP34	A High-Power Test of an X-Band Molybdenum-Iris Structure	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.
	Transparencies
THP35	Development of a Non-Magnetic Inertial Sensor for Vibration Stabilization in a Linear Collider	681
	J. Frisch, A. Chang, V. Decker, L. Hendrickson, T. Markiewicz, R. Partridge, A. Seryi SLAC, Menlo Park, California D. Eric, T. Himel SLAC/NLC, Menlo Park, California
	One of the options for controlling vibration of the final focus magnets in a linear collider is to use active feedback based on accelerometers. While commercial geophysics sensors have noise performance that substantially exceeds the requirements for a linear collider, they are physically large, and cannot operate in the strong magnetic field of the detector. Conventional nonmagnetic sensors have excessive noise for this application. We report on the development of a non-magnetic inertial sensor, and on a novel commercial sensor both of which have demonstrated the required noise levels for this application.
	Transparencies
THP36	Vibration Stabilization of a Mechanical Model of a X-Band Linear Collider Final Focus Magnet	684
	J. Frisch, A. Chang, V. Decker, L. Hendrickson, T. Markiewicz, R. Partridge, A. Seryi SLAC, Menlo Park, California E. Eric, L. Eriksson, T. Himel SLAC/NLC, Menlo Park, California
	The small beam sizes at the interaction point of a X-band linear collider require mechanical stabilization of the final focus magnets at the nanometer level. While passive systems provide adequate performance at many potential sites, active mechanical stabilization is useful if the natural or cultural ground vibration is higher than expected. A mechanical model of a room temperature linear collider final focus magnet has been constructed and actively stabilized with an accelerometer based system.
THP37	Approaches to Beam Stabilization in X-Band Linear Colliders	687
	J. Frisch, L. Hendrickson, T. Markiewicz, A. Seryi SLAC, Menlo Park, California P. Burrows, S. Molloy, G. White Queen Mary University of London, London C. Perry OXFORDphysics, Oxford, Oxon T.O. Raubenheimer, T. Thomas SLAC/NLC, Menlo Park, California
	In order to stabilize the beams at the interaction point, the X-band linear collider proposes to use a combination of techniques: inter-train and intra-train beam-beam feedback, passive vibration isolation, and active vibration stabilization based on either accelerometers or laser interferometers. These systems operate in a technologically redundant fashion: simulations indicate that if one technique proves unusable in the final machine, the others will still support adequate luminosity. Experiments underway for all of these technologies, have already demonstrated adequate performance.
THP38	High Precision Survey and Alignment of Large Linear Accelerators	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.
THP39	Operation of a 1.3 GHz, 10 MW Multiple Beam Klystron	693
	H.P. Bohlen, A. Balkcum, M. Cattelino, L. Cox, M. Cusick, S. Forrest, F. Friedlander, A. Staprans, E. Wright, L. Zitelli CPI, Palo Alto, California K. Eppley SAIC, Boston
	Results will be reported for a 1.3 GHz, 10 MW multiple beam klystron that is being developed for the TESLA linear accelerator facility. The design parameters for the device are 10 MW peak RF output power with 150 kW average power, 1.5 ms pulse length, 65% efficiency, 50 dB gain, and 2.0 A/cm² maximum cathode loading. Initial testing of the device has validated the basic design approach. Six 120 kV electron beams of measurably identical currents of 22.9 A each have been successfully propagated through the klystron circuit with 99.5% DC beam transmission at full operating video duty and with 98.5% saturated RF transmission. A peak power of 10 MW at 1.3 GHz with 60% efficiency and 49 dB of gain has been measured.
THP41	Development of High RF Power Delivery System for 1300 MHz Superconducting Cavities of Cornell ERL Injector	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.
THP42	NLC Hybrid Solid State Induction Modulator	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	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.
THP44	The Design and Performance of the Spallation Neutron Source Low-Level RF Control System	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.
THP45	The Toshiba E3736 Multi Beam Klystron	706
	A. Yano, S. Miyake TETD, Saitama Y.H. Chin KEK, Ibaraki S.Y. Kazakov IHEP Protvino, Protvino, Moscow Region A.V. Larionov, V.E. Teryaev BINP SB RAS, Protvino, Moscow Region
	A 10 MW, L-band multi beam klystron (MBK) for TESLA linear collider and TESLA XFEL has been under development at Toshiba Electron Tubes & Devices Co., Ltd. (TETD) in collaboration with KEK. The TESLA requires pulsed klystrons capable of 10 MW output power at 1300 MHz with 1.5 ms pulse length and a repetition rate of 10 pps. The MBK with 6 low-perveance beams in parallel in the klystron enables us to operate at lower cathode voltage with higher efficiency. The design work has been accomplished and the fabrication is under way. We are going to start conditioning and testing of prototype #0 in the beginning of June 2004. The design overview and the initial test results at the factory will be presented.
THP46	Cable Insulation Breakdowns in the Modulator with a Switch Mode High Voltage Power Supply	709
	A. Cours ANL, Argonne, Illinois
	The Advanced Photon Source modulators are PFN-type pulsers with 40 kV switch mode charging power supplies (PSs). The PS and the PFN are connected to each other by 18 feet of high-voltage (HV) cable. Another HV cable connects two separate parts of the PFN. The cables are standard 75 kV x-ray cables. All four cable connectors were designed by the PS manufacturer. Both cables were operating at the same voltage level (about 35 kV). The PS’s output connector has never failed during five years of operation. One of the other three connectors failed approximately five times more often than the others. In order to resolve the failure problem, a transient analysis was performed for all connectors. It was found that transient voltage in the connector that failed most often was subjected to more high-frequency, high-amplitude AC components than the other three connectors. It was thought that these components caused partial discharge in the connector insulation and led to the insulation breakdown. Modification of the PFN eliminated one HV cable and significantly reduced the AC components during the pulse. A connector with higher partial discharge inception voltage was chosen as a replacement.
THP47	The RF-System for A High Current RFQ at IHEP	712
	Z. Zhang, J. Li, J. Qiao, X. Xu IHEP Beijing, Beijing
	The R&D of a high current proton RFQ is one of the most important research tasks of the Accelerator Driven Sub-critical system (ADS) basic research project. In preliminary research phase, the 352.2 MHz RF system will be operated in pulse mode. CERN kindly provided IHEP with some RF equipment. Because the given RF system was used for CW operation at CERN before, to apply them to our pulse mode operation, some modifications and improvements are necessary. We made some indispensable assemblies, and also did some tests and commissioning of every sub-system. At present, the initial high power conditioning of the klystron is finished, and output power can reach nominal value. A description of RF power system is given, in particularly, the performance of HV power supply, thyratron crowbar and capacitors, hard tube modulator and its control electronics, and klystron power conditioning are presented.
	Transparencies
THP48	A High-Resolution S-band Down-Converting Digital Phase Detector for SASE FEL Use	715
	A.E. Grelick, N.D. Arnold ANL/APS, Argonne, Illinois J. Carwardine, N. Dimonte, A. Nassiri, T. Smith ANL, Argonne, Illinois
	Each of the rf phase detectors in the Advanced Photon Source linac consists of a module that down converts from S-band to 20 MHz followed by an analog I/Q detector. Phase is calculated from one digitized sample per pulse each of I and Q. The resulting data has excellent long-term stability but is noisy enough so that a number of samples must be averaged to get a usable reading. The more recent requirement to support a SASE FEL has presented the need to accurately resolve the relative phase of a single pulse. Replacing analog detection with digital sampling and replacing internal intermediate frequency reference oscillators with a lower noise external oscillator were used to control the two largest components of noise. The implementation of a central, ultralow noise reference oscillator and a distribution system capable of maintaining the low phase noise is described, together with the results obtained to date. The principal remaining technical issue is determining the processing power required as a function of measurement channels per processor, measured pulse repetition rate, intrapulse data bandwidth, and digital filter characteristics. The options and tradeoffs involved and the present status are discussed.
THP49	The RF-Station Interlock for the European X-ray laser	718
	T. Grevsmühl, S. Choroba, Ph. Duval, O. Hensler, J. Kahl, F.-R. Kaiser, A. Kretzschmann, K. Rehlich, U. Schwendicke, S. Simrock, S. Weisse DESY, Hamburg H. Leich, RW. Wenndorff DESY Zeuthen, Zeuthen
	The RF-station interlock for the European X-ray laser will be based on a 19"- 3U crate incorporating a controller with the 32-bit RISC NIOS-processor (ALTERA). The main task of the interlock system is to prevent any damage from the components of the RF station and connected cavities. The interlock system must also guarantee a maximum time of operation of the RF stations which implies the implementation of self diagnostics and repair strategies on a module basis. Additional tasks are: collection and temporary storage of status information of the individual channels of the interlock system, transfer of this information to the control system, slow control functions (e.g. HV setting and monitoring) and control of inputs and outputs from and to other subsystems. In this paper we present the implementation using an ALTERA-FPGA running a 32-bit RISC NIOS-processor. Connection to the accelerator main control is provided by Ethernet using BSD-style socket routines based on ALTERA's plugs-library. The layout of the system is presented and first hardware components are shown.
THP50	The CEBAF RF Separator System Upgrade	721
	C. Hovater, M. Augustine, A. Guerra, R. Nelson, R.A. Terrel, M. Wissmann TJNAF, Newport News, Virginia
	The CEBAF accelerator uses RF deflecting cavities operating at the third sub-harmonic (499 MHz) of the accelerating frequency (1497 MHz) to “kick” the electron beam to the experimental halls. The cavities operate in a TEM dipole mode incorporating mode enhancing rods to increase the cavity’s transverse shunt impedance. As the accelerators energy has increased from 4 GeV to 6 GeV the RF system, specifically the 1 kW solid state amplifiers, have become problematic, operating in saturation because of the increased beam energy demands. Two years ago we began a study to look into replacement for the RF amplifiers and decided to use a commercial broadcast Inductive Output Tube (IOT) capable of 30 kW. The new RF system uses one IOT amplifier on multiple cavities as opposed to one amplifier per cavity originally. In addition the new RF system supports the proposed 12 GeV energy upgrade to CEBAF. Currently we are halfway through the upgrade with two IOTs in operation and two more to be installed. This paper reports on the new RF system and the IOT performance.
THP51	Tuning of External Q And Phase for The Cavities of A Superconducting Linear Accelerator	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.
THP52	RF Reference Distribution System for the J-PARC Linac	727
	T. Kobayashi, E. Chishiro JAERI, Ibaraki-ken S. Anami, S. Michizono, S. Yamaguchi KEK, Ibaraki
	J-PARC (Japan Proton Accelerator Complex) linac, which is 300 m long, consists of 324 MHz accelerating section of the upstream and 972 MHz section (as future plan) of the downstream. In the klystron gallery, totally about 50 RF source control stations will stand for the klystrons and solid-state amplifiers. The error of the accelerating field must be within ±1° in phase and ±1% in amplitude. Thus, the high phase stability is required to the RF reference for all of the low-level RF control systems and the beam monitor systems. This paper presents a final design of the RF reference distribution system for this linac. The RF reference (12 MHz) is distributed to all stations optically. Low-jitter E/O and O/E with temperature stabilizers are developed. The reference is optically amplified and divided into 14 transmission lines, and is delivered through PSOF (the phase-stabilized optical fiber), the temperature of which is stabilized by cooling water. Each of the transmitted signals is divided more into 4 signals by an optical coupler. Our objective for the phase stability of the reference aims at <±0.3° at a 972 MHz frequency.
THP53	Quasi-Optical Components for Future Linear Colliders	730
	S. Kuzikov, G. G. Denisov, M. Yu. Shmelyov IAP, Nizhniy Novgorod J.L. Hirshfield Omega-P, Inc., New Haven, Connecticut
	This paper presents a concept of the quasi-optical RF system for future Ka-band electron-positron linear collider. According to this concept two RF feeding systems are considered: a Delay Line Distribution System (DLDS) and a pulse compressor based on the multi-mirror traveling-wave resonator. The DLDS is based on oversized waveguides. In such waveguides the so-called image multiplication phenomena are used for power launching, extracting, combining, and splitting of waves. Recent low power tests of mode launchers and other DLDS components are discussed. The 34 GHz pulse compressors, based on three and four-mirror resonators, are considered. The tests of the prototypes at a low power level under different modulation methods are discussed. The simulations and tests of mode converters, miter bends, RF loads, and other components, to be necessary for both compression systems, also are resulted.
THP54	Moscow Meson Factory DTL RF System Upgrade	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.
THP55	Electromagnetic Design of New RF Power Couplers for the S-DALINAC	736
	M. Kunze, M. Brunken, H.-D. Gräf, W.F.O. Müller, A. Richter, T. Weiland TU Darmstadt, Darmstadt
	New rf power couplers for the Superconducting Darmstadt Linear Accelerator (S-DALINAC) injector have to be designed to transfer rf power of up to 2 kW to the electron beam. This allows injector operation at beam currents from 0.15 mA to 0.2 mA and electron energies up to 14 MeV. The new couplers should possibly provide a external Q of 5·10⁶. The transverse kick should be as small as possible. The asymmetric field distribution of the couplers causes emittance growth of the electron beam and therefore the transverse kick has to be minimized. Electromagnetic simulations are applied to investigate different coupler designs and to localize possible problems at an early stage. Cavity external Q and transverse kick can be calculated from 3D electromagnetic eigenmode solutions. The present coaxial-coaxial input couplers at the S-DALINAC are limited to power operation below 500 W under full reflection. In order to reach power operation up to 2 kW a realizations of a low-kick waveguide coupler for the S-DALINAC injector is presented, namely a twin-waveguide coupler.
	Transparencies
THP56	Control of the Low Level RF System for J-Parc Linac	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.
THP57	Digital Feedback System for J-Parc Linac RF Source	742
	S. Michizono, S. Anami, S. Yamaguchi KEK, Ibaraki T. Kobayashi J-PARC, Ibaraki-ken
	At the proton linac of J-Parc (Japan Proton Accelerator Research Complex), an accelerating electric field stability of ±1% in amplitude and ±1° in phase is required for the RF system. In order to accomplish these requirements, a digital feedback system is adopted for flexibility of the feedback (FB) and feed forward (FF) algorism implementation. FPGAs are used for the real-time FB system. A DSP board is also utilized for data processing and communication between FPGAs and a crate control CPU (Host). The system was examined with the DTL cavity and it satisfies the stability specification. In this report, the digital rf system is described and operational stability is also summarized.
THP58	Development of C-band High-Power Mix-Mode RF Window	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.
THP59	Low Level RF Including a Sophisticated Phase Control System for CTF3	748
	J. Mourier, R. Bossart, J. Nonglaton, I. Syratchev, L. Tanner CERN, Geneva
	CTF3 (CLIC Test Facility 3), currently under construction at CERN, is a test facility designed to demonstrate the key feasibility issues of the CLIC (Compact LInear Collider) two-beam scheme. When completed, this facility will consist of a 150 MeV linac followed by two rings for bunch-interleaving, and a test stand where 30 GHz power will be generated. In this paper, the work that has been carried out on the linac’s low power RF system is described. This includes, in particular, a sophisticated phase control system for the RF pulse compressor to produce a flat-top rectangular pulse over 1.4 μs.
THP60	High-Power RF Distribution System for the 8-Pack Project	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.
THP61	SKIP - A Pulse Compressor for SuperKEKB	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	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	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.
THP66	Measurement and Control of Microphonics in High Loaded-Q Superconducting RF Cavities	763
	T.L. Grimm, W. Hartung, T.H. Kandil, H. Khalil, J. Popielarski, J. Vincent, R.C. York NSCL, East Lansing, Michigan C. Radcliffe MSU, East Lansing, Michigan
	Superconducting radio frequency (SRF) linacs with light beam loading, such as the CEBAF upgrade, RIA and energy recovery linacs, operate more efficiently with loaded-Q values >1·10⁷. The narrow band-width puts stringent limits on acceptable levels of vibration, also called microphonics, that detune the SRF cavities. Typical sources of vibration are rotating machinery, fluid fluctuations and ground motion. A prototype RIA 805 MHz v/c=0.47 cryomodule is presently under test in realistic operating conditions [1]. Real-time frequency detuning measurements were made for modulation rates from DC to 1 kHz. At 2 K the maximum frequency deviation was less than 100 Hz peak-to-peak, and was consistent with high loaded-Q operation. The measured modulation spectrum was primarily made up of discrete Fourier components with modulation frequencies less than 80 Hz. Using an accelerometer and helium pressure transducer, the primary sources of vibration were determined to be the high power cryoplant motors and 2 K helium fluctuations. Adaptive feedforward was used to decrease the magnitude of individual Fourier components by four to ten times [2]. Details of the experimental setup and measurements will be presented. [1] “Experimental Study of an 805 MHz Cryomodule for the Rare Isotope Accelerator”, T.L. Grimm et al., THP70, these proceedings. [2] “Adaptive Feedforward Cancellation (AFC) of Sinusoidal Disturbances in SRF Cavities”, H. Khalil et al., TUP76, these proceedings.
	Transparencies
THP67	Traveling Wave and Standing Wave Single Cell High Gradient Tests	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.
THP68	The Simulation Calculations And Dielectric Characteristics Investigation of a Hybrid Dielectric-Iris-Loaded Travelling Accelerating Structure	769
	C.-F. Wu USTC/NSRL, Hefei, Anhui
	Mafia code has been used to calculate the RF properties versus the geometric parameters and dielectric permittivity of the X-band (f=9.37 GHz) hybrid dielectric-iris-loaded travelling accelerating structure. The simulation results show that when the range of the permittivity is about 5–9 and the geometric parameters are optimized, the new structure may have lower ratio (about 1) of peak surface electric field at the iris to axial accelerating electric field , while r, Q, r/Q of the new structure being comparable to iris-loaded accelerating structure. The experimental investigation of the permittivity of the dielectric (ceramic)has been made by using the cavity perturbation technique. The results show that the permittivity of the ceramic is about 5.8 at the X-band and its stability is good.The above results will be applied to the design of the new accelerating structure, which may be a potential candidate of high gradient Linear accelerator.
THP69	The Tuning Study of the Coupled Cavities for the RF Chopper System of J-PARC	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	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)
THP71	First Experience with Dry-Ice Cleaning on SRF Cavities	776
	D. Reschke, A. Brinkmann DESY, Hamburg G. Müller BUW, Wuppertal D. Werner IPA, Stuttgart
	The surface of superconducting (s.c.) accelerator cavities must be cleaned from any kind of contaminations, like particles or chemical residues. Contaminations might act as centers for field emission, thus limiting the maximum gradient. Today's final cleaning is based on high pressure rinsing with ultra pure water. Application of dry-ice cleaning might result in additional cleaning potential. Dry-ice cleaning using the sublimation-impulse method removes particulate and film contaminations without residues. As a first qualifying step intentionally contaminated niobium samples were treated by dry ice cleaning. It resulted in a drastic reduction of DC field emission up to fields of 100 MV/m as well as in the reduction of particle numbers. The dry ice jet caused no observable surface damage. First cleaning tests on single-cell cavities showed Q-values at low fields up to 4x10¹⁰ at 1.8 K. Gradients up to 32 MV/m were achieved, but field emission still is the limiting effect. Further tests are planned to optimize the dry-ice cleaning technique.
THP72	A Newly Designed and Optimized CLIC Main Linac Accelerating Structure	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.
THP74	Laser Produced Ions as an Injection Beam for Cancer Therapy Facility	782
	A. Noda, M. Hashida, Y. Iwashita, S. Nakamura, S. Sakabe, S. Shimizu, T. Shirai, H. Tongu Kyoto ICR, Kyoto H. Daido JAERI APRC, Ibaraki-ken A. Fukumi, Z. Li, K. Matsukado NIRS, Chiba-shi T. Hosokai, H. Iijima, K. Kinoshita, M. Uesaka, T. Watanabe, K. Yoshii UTNL, Ibaraki T. Takeuchi DOP Nagoya, Nagoya
	Ion production from a solid target by a high-power short pulse laser has been investigated to replace the injector linac of the synchrotron dedicated for cancer therapy. As the high power laser, the laser with the peak power of 100 TW and minimum pulse duration of 20 fs which has been developed at JAERI Kansai Research Establishment, is assumed. Laser produced ions with 100% energy spread is energy selected within ±5% and then phase rotated with use of the RF electric field synchronized to the pulse laser, which further reduces the energy spread to ±1%. The scheme of the phase rotation is presented together with the experimental results of laser production from the thin foil target.
THP75	Superconducting Accelerating Structure with Gradient as 2 Times Higher as TESLA Structure	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: The shortened accelerating cells have transit time factor 0.9 instead of 0.64 for conventional standing wave cells with λ/2 length. 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. Stronger intercell coupling allows extending the accelerating cavity and improving a duty factor of linac. 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	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	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	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	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.
THP86	Low Power Measurements on a Finger Drift Tube Linac	800
	A. Schempp, K.-U. Kühnel IAP, Frankfurt-am-Main C.P. Welsch MPI-K, Heidelberg
	The efficiency of RFQs decreases at higher particle energies. The DTL structures used in this energy regions have a defocusing influence on the beam. To achieve a focusing effect, fingers with quadrupole symmetry were added to the drift tubes. Driven by the same power supply as the drift tubes, the fingers do not need an additional power source or feedthrough. Beam dynamics have been studied with PARMTEQ . Detailed analysis of the field distribution was done and the geometry of the finger array has been optimized with respect to beam dynamics. A spiral loaded cavity with finger drift tubes was built up and low power measurements were done. In this contribution, the results of the rf simulating with Microwave Studio are shown in comparison with bead pertubation measurement on a prototype cavity.
THP87	Accelerator Structure Bead Pull Measurement at SLAC	803
	J. Lewandowski, G. Bowden, J. Wang SLAC/ARDA, Menlo Park, California R. Miller SLAC, Menlo Park, California
	Microwave measurement and tuning of accelerator structures are important issues for the current and next generation of high energy physics machines. Application of these measurements both before and after high power processing can reveal information about the structure but may be misinterpreted if measurement conditions are not carefully controlled. For this reason extensive studies to characterize the microwave measurements at have been made at SLAC. For the beadpull a reproducible measurement of less than 1 degree of phase accuracy in total phase drift is needed in order to resolve issues such as phase changes due to structure damage during high power testing. Factors contributing to measurement errors include temperature drift, mechanical vibration, and limitations of measurement equipment such as the network analyzer. Results of this continuing effort will be presented.
THP88	Longitudinal Bunch Shape Monitor Using the Beam Chopper of the J-PARC	806
	F. Naito KEK, Ibaraki
	We propose the longitudinal bunch shape monitor for the low energy part of the linac of the J-PARC. The monitor uses the beam chopper cavity installled in the MEBT line between thr RFQ and the DTL of the J-PARC as a kind of the bunch rotator. Consequentry the longitudinal bunch shape is measured along the horizontal direction. If we can measure the energy distribution of the bunch also, the longitudinal emittance of the beam is derived. In the paper, the basic idea of the monitor is discussed in detail.
THP89	Measured RF Properties of the DTL for the J-PARC	809
	H. Tanaka, T. Kato, F. Naito, E. Takasaki KEK, Ibaraki H. Asano, T. Morishita JAERI, Ibaraki-ken T. Itou JAERI/LINAC, Ibaraki-ken
	RF properties of the second DTL tank for J-PARC have been measured in KEK. The required flatness and stability of the accelerating field of the tank have been achieved by the tunung of the post-couplers, whose shape were modified to adjust the resonant frequency ?324 MHz). Because the third DTL tank has assembled, the rf measurement and the post-coupler tuning will be started soon. Thus the measured results for both tanks will be described in the paper.
THP90	The Technique for the Numerical Tolerances Estimations in the Construction of Compensated Accelerating Structures	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	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.
THP93	A 3D Self-Consistent, Analytical Model for Longitudinal Plasma Oscillation in a Relativistic Electron Beam	818
	G. Geloni, E. Saldin, E. Schneidmiller, M.V. Yurkov DESY, Hamburg
	Longitudinal plasma oscillations are becoming a subject of great interest for XFEL physics in connection with LSC microbunching instability[1] and certain pump-probe synchronization schemes[2]. In the present paper we developed the first exact analytical treatment for longitudinal oscillations within an axis-symmetric, (relativistic) electron beam, which can be used as a primary standard for benchmarking space-charge simulation codes. Also, this result is per se of obvious theoretical relevance as it constitutes one of the few exact solutions for the evolution of charged particles under the action of self-interactions. [1] E. Saldin et al., "Longitudinal Space Charge Driven Microbunching instability in TTF linac", TESLA-FEL-2003-02, May 2003, [2] J. Feldhaus et al., "Two-color FEL amplifier for femtosecond-resolution pump-probe experiments with GW-scale X-ray and optical pulses",DESY 03-091, July 2003
THP94	Cold Tests of a 160 MHz Half-Wave Resonator	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.
THP95	Electro Polishing of Niobium Cavities at DESY	824
	A. Matheisen, L. Lilje, H. Morales, B. Petersen, M. Schmoekel, N. Steinhau-Kühl DESY, Hamburg
	At DESY a facility for electro polishing (EP) of the super conducting (s.c.) TESLA/TTF cavities have been built and is operational since summer 2003. The EP infrastructure is capable to handle single-cell structures and the standard TESLA/ TTF nine-cell cavities. Several electro polishing processes have been made since and acceleration voltage up to 40 MV/m have been reached in nine cell structures. We report on measurements and experiences gained since 2003 as well as on handling procedures developed for the preparation of electro polished resonators. Specific data like heat production, variation of current density and bath aging will be presented. Another important point for reproducible results is the quality control of the electro polishing process. First quality control steps to be implanted in the EP procedure for large-scale production will be described.