EPAC08 - Classification:07 Accelerator Technology Main Systems/T06 Room Temperature RF

07 Accelerator Technology Main Systems

T06 Room Temperature RF

Paper	Title	Page
MOPP080	Studies of Breakdown in a Pressurized RF Cavity	736
	M. BastaniNejad, A. A. Elmustafa Old Dominion University, Norfolk, Virginia M. Alsharo'a, P. M. Hanlet, R. P. Johnson, S. Korenev, M. Kuchnir, D. J. Newsham, R. Sah Muons, Inc, Batavia C. M. Ankenbrandt, A. Moretti, M. Popovic, K. Yonehara Fermilab, Batavia, Illinois D. M. Kaplan Illinois Institute of Technology, Chicago, Illinois D. Li LBNL, Berkeley, California D. Rose, C. H. Thoma, D. R. Welch Voss Scientific, Albuquerque, New Mexico
	Previous studies of RF breakdown in a cavity pressurized with dense hydrogen gas have indicated that breakdown probability is proportional to a high power of the surface electromagnetic field. This behavior is similar to the Fowler-Nordheim description of electron emission from a cold cathode, and it implies that breakdown is a quantum mechanical effect that is characterized by the work function of the cavity metal. We describe our present efforts to measure the distributions of work functions at the nanoscale level on the surfaces of the electrodes used in breakdown studies, and to understand how the RF conditioning process affects them.
MOPP081	Engineering Design of a PETS Tank Prototype for CTF3 Test Beam Line	739
	D. Carrillo, L. García-Tabarés, J. L. Gutierrez, I. Rodriguez, E. Rodríguez García, S. Sanz, F. Toral CIEMAT, Madrid G. Arnau-Izquierdo, N. C. Chritin, S. Doebert, G. Riddone, I. Syratchev, M. Taborelli CERN, Geneva J. Calero CEDEX, Madrid
	In the CLIC concept, PETS (Power Extraction and Transfer Structure) role is to decelerate the drive beam and transfer RF power to the main beam. One of the CTF3 test beam line (TBL) aims is to study the decelerated beam stability and evaluate PETS performance. The PETS core is made of eight 800 mm long copper rods, with very tight tolerances for shape (± 20 micron), roughness (less than 0.4 micron) and alignment (± 0.1 mm). Indeed, they are the most challenging components of the tank. This paper reports about the methods of fabrication and control quality of these bars. A special test bench has been designed and manufactured to check the rod geometry by measuring the RF fields with an electric probe. Other parts of the PETS tank are the power extractor, the waveguides and the vacuum tank itself. Industry is partially involved in the prototype development, as the series production consists of 15 additional units, and some concepts could be even applicable to series production of CLIC modules
MOPP083	Status of High Power Tests of Normal Conducting Single-cell Structures	742
	V. A. Dolgashev, S. G. Tantawi SLAC, Menlo Park, California Y. Higashi, T. Higo KEK, Ibaraki
	We report results of ongoing high power tests of single cell traveling wave and standing wave structures. These tests are part of an experimental and theoretical study of rf breakdown in normal conducting structures at 11.4 GHz. The goal of this study is to determine the gradient potential of normal-conducting, rf powered particle beam accelerators. The test setup consists of reusable mode launchers and short test structures and powered by SLAC’s XL-4 klystron. The mode launchers and structures were manufactured at SLAC and KEK and tested in SLAC klystron test laboratory. V. A. Dolgashev, S. G. Tantawi, et al. “High Power Tests of Normal Conducting Single Cell Structures,” SLAC-PUB-12956, PAC07, Albuquerque, New Mexico, 25-29 June 2007, pp 2430-2432.
MOPP084	Installation and Commissioning of the RF System for the New Elettra Booster	745
	A. Fabris, M. Bocciai, L. Bortolossi, M. Ottobretti, C. Pasotti, M. Rinaldi ELETTRA, Basovizza, Trieste
	The commissioning of the new booster of the Elettra synchrotron radiation source started in Fall 2007. The RF system of the booster is made of a five cells accelerating cavity fed by a 60 kW 500 MHz power plant. The accelerating cavity voltage is ramped along with the booster energy at a 3 Hz repetition rate. The cavity field is controlled by analog feedback loops on amplitude, phase and the resonant frequency. This paper describes the setting into operation of the system and its performances during the commissioning phase of the machine.
MOPP085	Bench Characterization of a Prototype of a 3rd Harmonic Cavity for the LNLS Electron Storage Ring	748
	R. H.A. Farias, D. A. Nascimento, C. Pardine, P. F. Tavares LNLS, Campinas
	The UVX electron storage ring at the Brazilian Synchrotron Light Laboratory suffers from longitudinal instabilities driven by a HOM of one of the RF cavities. The operational difficulties related to these unstable modes were successfully overcome by determining the proper cavity temperature set point in combination with phase modulation of the RF fields at the second harmonic of the synchrotron frequency. However, a serious drawback of the method is to increase the energy spread of the electron beam, which is detrimental for the undulator emission spectrum. The use of higher harmonic cavities is a more appropriate technique since it provides damping of the longitudinal modes without increasing the energy spread. A full scale prototype of a 3rd harmonic cavity was manufactured at the LNLS workshops and had its main rf properties measured. Special care was taken to measure the shunt impedance of the fundamental resonant mode since it determines how many cavities will be necessary for the adequate operation of the system, which is designed to operate in passive mode. In this work we present the results of the bench characterization of the cavity.
MOPP086	A Novel Fabrication Technique for the Production of RF Photoinjectors	751
	P. Frigola, R. B. Agustsson, S. Boucher, A. Y. Murokh RadiaBeam, Los Angeles D. Cormier, T. Mahale NCSU, Raleigh L. Faillace Rome University La Sapienza, Roma J. B. Rosenzweig, G. Travish UCLA, Los Angeles, California
	Recent developments in Direct Metal Free Form Fabrication (DMFFF) technology may make it possible to design and produce near netshape copper structures for the next generation of very high duty factor, high gradient radio frequency (RF) photoinjectors. RF and thermal-management optimized geometries could be fully realized without the usual constraints and compromises of conventional machining techniques. A photoinjector design incorporating DMFFF and results from an initial material feasibility study will be reported.
MOPP087	RF System for the SSRF Booster Synchrotron	754
	Q. Gu, L. X. Chen, M. Chen, L. Feng, Z. Q. Feng, H. T. Hou, J. F. Liu, C. Luo, D. Q. Mao, F. Wang, Zh. G. Zhang, S. J. Zhao, Y. B. Zhao, Z. S. Zhou SINAP, Shanghai
	The booster synchrotron of the Shanghai Synchrotron Radiation Facility (SSRF) ramps the energy of electron beam from 150 MeV to 3.5 GeV with a repetition rate of 2 Hz. The guidelines of the system design are simplicity and reliability, and the ability of top-up injection for the storage ring is also taking into account. The RF system consists of a 180kW CW plant with a WR1800 waveguide line, two PETRA type 5-cell cavities and an analog low level RF electronics with vector-sum scheme. An overview, installation and commissioning of the whole booster RF system are presented in this paper. The performance of the RF system with the beam is also given.
MOPP088	The High Harmonics Cavity System for the New Experimental Storage Ring at FAIR	757
	R. G. Heine, C. Dimopoulou, U. Laier GSI, Darmstadt
	The "Facility for Antiproton and Ion Research" (FAIR) will consist of several synchrotrons and storage rings dedicated to target experiments as well as in-situ experiments. One of the in-situ experiments is ELISe, a head-on collision of a heavy ion beam in the new experimental storage ring(NESR) with an electron beam prepared in the electron ring (ER). The vertex is placed in a bypass to the NESR where both rings have a common straight section. To prepare the heavy ion beam for collision with the bunched electron beam circulating at a fixed repetition rate a dedicated RF system called high harmonics cavity system (HHC) operating at a frequency of 44.7MHz is needed. The HHC will be realised as a disk loaded coaxial quarter wave resonator. This paper deals with the actual development status of this RF system, including analytically derived voltage demands, multipactor thresholds and considerations on input coupling and HOM damping.
MOPP090	Incorporating RF into a Muon Helical Cooling Channel	760
	S. A. Kahn, M. Alsharo'a, R. P. Johnson Muons, Inc, Batavia D. R. Broemmelsiek, A. Jansson, V. Kashikhin, V. S. Kashikhin, A. L. Klebaner, G. F. Kuznetsov, G. V. Romanov, A. V. Shemyakin, D. Sun, K. Yonehara, A. V. Zlobin Fermilab, Batavia, Illinois L. Thorndahl CERN, Geneva
	A helical cooling channel (HCC) consisting of a pressurized gas absorber imbedded in a magnetic channel that provides solenoidal, helical dipole and helical quadrupole fields has shown considerable promise in providing six-dimensional cooling for muon beams. The energy lost by muons traversing the gas absorber needs to be replaced by inserting RF cavities into the lattice. Replacing the substantial muon energy losses using RF cavities with reasonable gradients will require a significant fraction of the channel length be devoted to RF. However, to provide the maximum phase space cooling and minimal muon losses, the helical channel should have a short period and length. In this paper we shall examine three approaches to include RF cavities into the HCC lattice: Use higher frequency cavities that can be placed inside the magnetic channel, Interleave cavities between magnetic coil rings, and Place banks of RF cavities between segments of HCC channels. Each of these approaches has positive and negative features that need to be evaluated in selecting the proper concept for including RF into the HCC system.
MOPP091	Upgrade of Input Power Coupling System for the SNS RFQ	763
	Y. W. Kang, A. V. Aleksandrov, P. E. Gibson, T. W. Hardek, C. Luck, R. C. Peglow, A. V. Vassioutchenko ORNL, Oak Ridge, Tennessee
	A RF input power coupler system has been developed for upgrade of input coupling to the RFQ in the SNS linac front-end. The design employs two coaxial loop couplers for 402.5 MHz operation. Two couplers are used in parallel to power the accelerating structure with up to 800 kW total peak power at 8% duty cycle. Each coupler loop has a coaxial ceramic window that is connected to each output of a magic-T waveguide hybrid splitter through a coaxial to waveguide transition. The coaxial loop couplers have been designed, manufactured, and high power processed. This paper presents the following: RF and mechanical designs of the couplers and system, procedure and result of high power RF conditioning, and test and operation results of the upgraded system.
MOPP093	Fast L-band Waveguide Phase Shifter	769
	S. Kazakov, S. V. Shchelkunov Omega-P, Inc., New Haven, Connecticut J. L. Hirshfield Yale University, Physics Department, New Haven, CT A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio E. Nenasheva Ceramics Ltd., St. Petersburg V. P. Yakovlev Fermilab, Batavia, Illinois
	During the operation of accelerators it is often important to rapidly change the parameters of the RF system, such as cavity resonant frequency, coupling, or electrical length. For this purpose a fast L-band planar phase shifter has been designed, that has advantages compared to the coaxial scheme considered before by the authors (EPAC 06). The phase shifter is based on a new ferroelectric ceramic, whose permittivity changes with application of an external voltage. The switching time depends on only the external HV circuit and can by less than a few microseconds. The conceptual design and electrical parameters of the new phase shifter are presented, as are first results of low power measurements on a 1/3 model.
MOPP094	Reduction of Q-loss-effects in Ferrite-loaded Cavities	772
	H. G. Koenig, S. Schaefer GSI, Darmstadt
	Accelerating cavities loaded with Ni-Zn ferrites have been widely used in synchrotrons for many years. So far their performance is significantly limited by the so-called high-loss-effect (HLE) or quality-loss-effect (QLE). After some milliseconds, this effect leads to a sudden drop of the resonator's voltage namely under the following conditions: fixed frequencies with RF-power above a specific threshold level and a parallel DC-biasing. The mechanism of this unwanted loss has not been fully understood yet. Now a simple method has been found to work against this effect with the aid of mechanical damping of surface waves. For small samples of ferrites the QLE is fully suppressed by using a rubber belt around the circumference or by covering the surface with a thin layer of hot-melt adhesive. We were able to show that similar methods applied to full size rings lead to a significant increase of the onset voltage of the QLE. Most of the existing ferrite loaded accelerating cavities with QLE-limitations can be increased in their accelerating voltage by the above-mentioned modification.
MOPP095	Advanced Experimental Techniques for RF and DC Breakdown Research	775
	J. W. Kovermann RWTH, Aachen S. Calatroni, A. Descoeudres, T. Lefevre, W. Wuensch CERN, Geneva
	Advanced experimental techniques are being developed to do in-situ analysis of DC and RF breakdowns. First measurements with a specially built spectrometer have been made with a DC spark setup at CERN and with CLIC accelerating structures in the 30GHz power test facility. This spectrometer measures the light intensity development during a breakdown for narrow wavelength intervals in the visible and near infrared range which will give information about the involved elements, temperature and plasma parameters and eventually precursors of a breakdown. Planned experiments for X-ray spectroscopy and imaging, measurements of RF-signals and ion and electron energy distribution and infrared imaging of breakdown sites are presented.
MOPP096	C-band Linac Optimization for a Race-track Microtron	778
	Yu. A. Kubyshin UPC, Barcelona D. Carrillo, L. García-Tabarés, F. Toral CIEMAT, Madrid A. V. Poseryaev, V. I. Shvedunov MSU, Moscow
	Optimization results of a C-band standing wave on-axis coupled linac for a miniature race-track microtron (RTM) are presented. The optimization procedure includes three steps: choice of the linac cells lengths and field strength following requirements of the RTM beam dynamics, 2D cells geometry optimization to maximize the shunt impedance and minimize the surface field strength and, finally, full scale 3D optimization. The 3D calculations were done independently with two codes: ANSYS and HFSS. Various methods of calculation of the coupling slots dimensions, including the waveguide-linac coupling slot, are described in detail.
MOPP097	Measurements on the Rf Cavity for the ALBA Storage Ring	781
	M. L. Langlois, M. Cornelis, F. Pérez, P. Sanchez ALBA, Bellaterra
	ALBA storage ring will use 6 ambient temperature nose cone HOM damped cavities tuned at 500 MHz, designed at BESSY and known as the EU cavity. A first one, manufactured by ACCEL, was delivered in 2007 to investigate on its behaviour. This paper describes the data collected during investigation. First, bead-pull measurements were performed to assess impedance, both on fundamental and high order modes. Emphasis was put on E011, due to the discrepancy between expected values and results for this mode. The vacuum bake-out and related pressure are shown. Then, the cavity was conditioned and observations were made on multipacting levels, conditioning time and surface temperatures. The latter were found inhomogeneous and leads are detailed to avoid local overheating.
MOPP098	A 201-MHz Normal Conducting RF Cavity for the International MICE Experiment	784
	D. Li, A. J. DeMello, S. P. Virostek, M. S. Zisman LBNL, Berkeley, California R. A. Rimmer Jefferson Lab, Newport News, Virginia
	MICE is a demonstration experiment for the ionization cooling of muon beams. Eight RF cavities are proposed to be used in the MICE cooling channel. These cavities will be operated in a strong magnetic field; therefore, they must be normal conducting. The cavity design and construction are based on the successful experience and techniques developed for a 201-MHz prototype cavity for the US MUCOOL program. Taking advantage of a muon beam’s penetration property, the cavity employs a pair of curved thin beryllium windows to terminate conventional beam irises and achieve higher cavity shunt impedance. The cavity resembles a round, closed pillbox cavity. Two half-shells spun from copper sheets are joined by e-beam welding to form the cavity body. There are four ports on the cavity equator for RF couplers, vacuum pumping and field probes. The ports are formed by means of an extruding technique.
MOPP099	MICE RF System	787
	A. J. Moss, P. A. Corlett, J. F. Orrett, J. H.P. Rogers STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
	The Muon Ionisation Cooling Experiment (MICE) at the Rutherford Appleton Laboratory uses normal conducting copper cavities to re-accelerate a muon beam after it has been retarded by liquid hydrogen absorbers. Each cavity operates at 200MHz and requires 1MW of RF power in a 1ms pulse at a repetition rate of 1Hz. In order to provide this power, a Thales TH116 triode, driven by a Burle 4616 tetrode is used, with each amplifier chain providing ~2.5MW. This power is then split between 2 cavities. The complete MICE RF system is described, including details of the low level RF, the power amplifiers and the coaxial power distribution system.
MOPP100	Performance of Compact Electron Injector on Evanescent Oscillations	790
	V. V. Mytrochenko, M. I. Ayzatskiy, I. V. Khodak, K. Kramarenko, V. A. Kushnir, A. Opanasenko, S. A. Perezhogin, D. L. Stepin, Z. V. Zhiglo NSC/KIPT, Kharkov
	An injector on the basis of a resonator structure with exponentially increasing amplitude of the electric field along an axis was developed at NSC KIPT. The injector is supplied with RF power through a rectangular-to-coaxial waveguide transition to provide axial symmetry of the accelerating field. The injector was designed to provide the output current up to 1 A at particle energy up to 1 MeV. Results of the injector test are presented in the work. Results obtained are compared with calculated ones.
MOPP102	High Field Gradient RF System for a Spiral FFAG, RACCAM	793
	C. Ohmori KEK, Ibaraki J. Fourrier, J. Pasternak LPSC, Grenoble F. Meot CEA, Gif-sur-Yvette
	A high field-gradient RF system for a spiral FFAG is described. It is wideband to cover the frequency of 3 to 7.5 MHz. The beam will be accelerated with a high repletion rate of 100 Hz to fit requirements for hadron therapy. The cavity has a wide aperture of 90 cm in horizontal direction to allow a large excursion for beam acceleration. It has less than 40 cm in length to fit a very short straight section.
MOPP103	High Field Gradient RF System for Bunch Rotation in PRISM-FFAG	796
	C. Ohmori KEK, Ibaraki M. Aoki, Y. Arimoto, I. Itahashi, Y. Kuno, Y. Kuriyama, A. Sato, M. Y. Yoshida Osaka University, Osaka Y. Iwashita Kyoto ICR, Uji, Kyoto Y. Mori KURRI, Osaka
	The PRISM project aims to supply a high quality muon beam using a wide aperture FFAG for mu-e conversion experiment. The low energy muon which has a large momentum spread will be manipulated in the FFAG using a bunch rotation technique with a low frequency RF around 3.5 MHz. Because of a short lifetime of muon, the rotation should be end in 5-6 turns in the FFAG and more than 2 MV is needed. The low frequency RF system using a magnetic alloy is designed to achieve a very high field gradient of more than 200 kV/m. The whole system is designed for a very low duty pulse operation to minimize the cost. The system has been modified to operate at 2 MHz for the beam test using alpha particle. A field gradient of more than 100 kV/m has been obtained by the preliminary test.
MOPP104	Possible Upgrade Scenario for J-PARC Ring RF	799
	C. Ohmori, K. Hara, A. Takagi, M. Toda, M. Yoshii KEK, Ibaraki K. Hasegawa, M. Nomura, A. Schnase, F. Tamura, M. Yamamoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
	The whole J-PARC RCS RF system is operational and during beam commissioning in 2007 the beam in RCS was successfully accelerated to final energy and then extracted. The Main Ring RF system has been installed in the tunnel. Both Ring RF systems are based on the new technology using magnetic alloy loaded cavities and have achieved higher field gradient than existing ferrite base RF systems in this frequency region. For the future upgrade of the J-PARC Main Ring, a short accelerating cycle is required to increase the average beam current. In this paper, a possible upgrade scenario for RF cavities based on improvements of the magnetic alloy ring cores will be described.
MOPP105	Compact, Tunable RF Cavities	802
	M. Popovic, C. M. Ankenbrandt, E. Griffin, A. Moretti, R. E. Tomlin Fermilab, Batavia, Illinois M. Alsharo'a, I. B. Enchevich, R. P. Johnson, S. Korenev Muons, Inc, Batavia
	New developments in the design of fixed-field alternating gradient (FFAG) synchrotrons have sparked interest in their use as rapid-cycling, high intensity accelerators of ions, protons, muons, and electrons. Potential applications include proton drivers for neutron or muon production, rapid muon accelerators, electron accelerators for synchrotron light sources, and medical accelerators of protons and light ions for cancer therapy. Compact RF cavities that tune rapidly over various frequency ranges are needed to provide the acceleration in FFAG lattices. An innovative design of a compact RF cavity that uses orthogonally biased ferrite for fast frequency tuning and liquid dielectric to adjust the frequency range is being developed using physical prototypes and computer models.
MOPP106	Study of Radiation From RF Cavities	805
	R. Sandstrom DPNC, Genève D. Huang IIT, Chicago, Illinois J. Norem ANL, Argonne, Illinois
	Essential for muon accelerators such as neutrino factories or muon colliders, ionization cooling channels use RF cavities to restore the energy lost in liquid hydrogen absorbers. One major limitation in cooling comes from electrons emitted from the cavities which can cause breakdowns or unacceptable thermal load to the liquid hydrogen vessels. In the Muon Ionization Cooling Experiment MICE, these electrons also cause background in the detectors. This paper presents simulations related to these dark currents, and analysis of data from a direct measurement of this radiation in the MuCool Test Area (MTA).
MOPP108	Status of HOM Damped Room-temperature Cavities for the ESRF Storage Ring	808
	V. Serriere, A. K. Bandyopadhyay, L. Goirand, J. Jacob, D. Jalas, B. Ogier, A. Triantafyllou ESRF, Grenoble N. Guillotin SOLEIL, Gif-sur-Yvette
	At the ESRF, longitudinal coupled bunch instabilities driven by cavity HOM are currently avoided up to the nominal current of 200 mA by precisely controlling the temperatures of the six five-cell cavities installed on the storage ring. A longitudinal bunch by bunch feedback has recently allowed to overcome the remaining HOM and thereby increase the current in the storage ring to 300 mA. In parallel, HOM damped room-temperature cavities are being developed for highly reliable passive operation at 300 mA. They are designed for a possible later upgrade to higher currents.
MOPP109	Status of the 100 MeV Preinjector for the ALBA Synchrotron	811
	A. Falone, D. Einfeld, M. Pont ALBA, Bellaterra D. Jousse, J.-L. Pastre, F. Rodriguez, A. S. Setty THALES, Colombes A. Sacharidis EuroMev, Buc
	A turn key 100 MeV linac has been constructed by THALES in order to inject electrons into the booster synchrotron of ALBA. The linac will be commissioned in May 2008. This paper will remind the main features of the linac* and will give results obtained during the commissioning tests. The energy and emittance measurements will be done on the transfer line conceived and realized by CELLS. * D. Einfeld "Status of ALBA", PAC07, Albuquerque, USA, June 2007. ** A. Setty "Beam dynamics of the 100 MeV preinjector for the spanish synchrotron ALBA", PAC07, Albuquerque, USA, June 2007.
MOPP110	The SNS Resonance Control Cooling System Control Valve Upgrade Performance	814
	D. C. Williams, J. P. Schubert, J. Y. Tang ORNL, Oak Ridge, Tennessee
	The normal-conducting linac of the Spallation Neutron Source (SNS) uses 10 separate Resonance Control Cooling System (RCCS) water skids to control the resonance of 6 Drift Tube Linac (DTL) and 4 Coupled Cavity Linac (CCL) accelerating structures. The RCCS water skids use 2 control valves; one to regulate the chilled water flow and the other is used to bypass water to a heat exchanger. These valves have hydraulic actuators that provide position and feedback to the control system. Frequency oscillations occur using these hydraulic actuators due to their coarse movement and control of the valves. New air actuator control positioners have been installed on the DTL3 RCCS water skid to give finer control and regulation of DTL3 cavity temperature. This paper shows a comparison of resonance control performance for two valve configurations.
MOPP111	Beam Tests with the MAFF IH-RFQ at the IAP-Frankfurt	817
	H. Z. Zimmermann, D. Habs LMU, Garching A. Bechtold, P. Kolb, A. Schempp IAP, Frankfurt am Main
	The IH-type RFQ for the MAFF project at the LMU Munich is integrated into a test bench at the IAP in Frankfurt. The existing IH-RFQ set-up is the second after the HIS at GSI and the first one that can be directly compared to a very similar 4-rod type machine, the REX-ISOLDE RFQ at CERN. The test bench consists of an ionsource, an electrostatic quadrupole lens system with implemented steerers, and several beam diagnostic like a two dimensional emittance scanner, bending magnet and a fast faraday cup. Experimental results will be presented. These tests accompanied with theoretical investigations will be done with special respect to the applicability of such normal conducting RFQ accelerators to the EURISOL post accelerator.
THXM01	CLIC Accelerating Structure Development	2922
	W. Wuensch CERN, Geneva
	One of the most important objectives of the CLIC (Compact Linear Collider) study is to demonstrate the design accelerating gradient of 100 MV/m in a fully featured accelerating structure under nominal operating conditions including pulse length and breakdown rate. The development and testing program which has been put into place to achieve this objective is described. Recent advances in understanding and quantifying the effects which limit the accelerating gradient are presented.
	Slides
THXM03	Status of the European HOM Damped Normal Conducting Cavity	2932
	E. Weihreter BESSY GmbH, Berlin
	Cavities with damped higher order modes (HOMs) are an essential ingredient for state of the art storage ring based high brilliance synchrotron radiation sources to avoid degradation of the beam quality due to coupled bunch instabilities. Starting with a review of the concepts of existing HOM damped cavities the status of a normal conducting 500 MHz cavity is presented which has been developed for low and medium energy high brilliance synchrotron light sources within the frame of an EC funded collaboration. The results of numerical simulations and of low power impedance measurements are reported together with conceptional improvements, expected performance, and first operational achievements in the Metrology Light Source in Berlin.
	Slides