Keyword: HOM
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MOPFI003 SRF Photoinjector Cavity for BERLinPro cavity, cathode, SRF, gun 285
 
  • A. Neumann, W. Anders, A. Burrill, A. Frahm, T. Kamps, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
  • E.N. Zaplatin
    FZJ, Jülich, Germany
  
  For the funded BERLinPro project, a 100 mA CW-driven SRF energy recovery linac, a SRF photoinjector cavity has to be developed which delivers a small emittance, 1 mm*mr, high brightness beam while accelerating a high average current within given high power limitations. To achieve these goals the injector is being developed in a three stage approach. In the current design step a cavity shape was developed which fulfills the beam dynamics requirements, implements a high quantum efficiency normal conducting photocathode with the HZDR choke and insert design and allows for beam studies at currents up to 4 mA. This paper will describe the RF design process, higher order mode studies and final mechanical calculations prior to the cavity production.  
 
MOPME019 Alignment Detection Study using Beam Induced HOM at STF cavity, dipole, alignment, cryomodule 509
 
  • A. Kuramoto
    Sokendai, Ibaraki, Japan
  • H. Hayano
    KEK, Ibaraki, Japan
  
  STF accelerator using L-band photocathode RF Gun and two superconducting cavities is under operation for R&D of ILC. Electron beam extracted from the RF Gun is accelerated to 40 MeV by two superconducting cavities. Cavity alignment requirements for ILC are less than 300um offset and 300urad tilt with respect to cryomodule. It is necessary to measure their offset and tilt inside of cryomodule. Cavity offset has been already measured by using beam induced HOM at FLASH in DESY. Cavity deformation during assembly and by cooling contraction has not been examined yet. We measured HOM signals to detect their tilt and bending. TE111-6 which has high impedance is used to estimate cavity offset. To find cavity tilt and bending, we selected pi over nine mode in the first dipole passband (TE111-1) and beam pipe modes. From information of TE111-1 which has maximum radial electric field in the middle cell, we can get electrical center of middle cell. At beam pipes, electrical center can be found by using beam pipe modes. Combinations of these electrical centers tell us cavity tilt and bending. We will present results of these TE111-1 and beam pipe mode together with beam trajectory information.  
 
MOPWA055 Status of Higher Order Mode Beam Position Monitors in 3.9 GHz Superconducting Accelerating Cavities at FLASH cavity, wakefield, dipole, diagnostics 798
 
  • P. Zhang, R.M. Jones, I.R.R. Shinton
    UMAN, Manchester, United Kingdom
  • N. Baboi, P. Zhang
    DESY, Hamburg, Germany
  • T. Flisgen, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  
  Funding: This work was partially funded by the European Commission under the FP7 Research Infrastructures grant agreement No.227579.
Higher order mode (HOM) beam position monitors (BPM) are being developed for the 3.9GHz third harmonic superconducting accelerating cavities at FLASH. The transverse beam position in a cavity can be determined utilizing beam-excited HOMs based on dipole components. The existing couplers used for HOM suppression provide the necessary signals. The diagnostics principle is similar to a cavity BPM, but requires no additional vacuum instruments on the linac. The challenges lie in the dense HOM spectrum arising from couplings of the majority HOMs amongst the four cavities in the cryo-module. HOMs with particularly promising diagnostics features were evaluated using various devices with various analysis methods. After careful theoretical and experimental assessment of HOMs, multi-cavity modes at ~5GHz were chosen to provide a global position over the complete module with superior resolution (~20μm) while trapped modes at ~9GHz provide local position in each cavity with comparable resolution (~50μm). A similar HOM-BPM system is planned for the European XFEL 3.9GHz module with 8 cavities. This paper reviews both the current status and the future prospects of HOM-BPMs in 3.9GHz cavities. 		 
 
MOPWA070 Beam Position Monitor within the Cornell Energy Recovery Linac Cavity Assembly coupling, pick-up, RF-structure, cavity 840
 
  • M.G. Billing, M. Liepe, V.D. Shemelin, N.R.A. Valles
    CLASSE, Ithaca, New York, USA
  
  In an energy recovery Linac (ERL) the low energy beam is very sensitive to deflections due to the RF fields as it passes through the accelerator cavities. Therefore, to avoid the possible effects of beam breakup, it will be important to determine the optimum transverse position for the beam within the first several sets of cavity cells in the cryostat assembly and to maintain this position over long periods. As a result a beam position monitor (BPM) has been designed to be located between the higher-order modes (HOM) loads and the seven-cell RF structures. This BPM’s design reduces the coupling of RF power from the fundamental mode and HOMs into the BPM, while maintaining acceptable position sensitivity and resolution. We analyzed the coupling of the probe to the HOMs of realistically shaped cavities by generating geometries for hundreds of cavities having small shape variations from the nominal dimensions consistent with present machining tolerances, and solved for their monopole and dipole spectra. Our results show that the peak, dissipated power within BPM cables, which pass through the cryostat, is well within the permissible levels.  
 
MOPWO026 Investigation of Numerical Precision Issues of Long Term Single Particle Tracking simulation, dynamic-aperture, resonance, beam-beam-effects 942
 
  • E. McIntosh, R. De Maria, M. Giovannozzi
    CERN, Geneva, Switzerland
  
  Funding: The HiLumi LHC Design Study is included in the HL-LHC project and is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404.
Long term single particle simplectic tracking is one of the most reliable tool to study the dynamic aperture of the circular accelerators. The present computational performance allows to explore the long term behaviour for an extended number of turns. It is well known that for instance single precision floating point arithmetic introduces too much numerical noise even after a moderate number of turns. In this paper we explore the artefacts of the double precision arithmetic that may be visible when the number of turns is in the order of 106, 107. 		 
 
MOPWO028 Recent Developments and Future Plans for SixTrack simulation, collimation, ion, multipole 948
 
  • R. De Maria, R. Bruce, R. Calaga, L. Deniau, M. Fjellstrom, M. Giovannozzi, L. Lari, Y.I. Levinsen, E. McIntosh, A. Mereghetti, D. Pastor Sinuela, S. Redaelli, H. Renshall, A. Rossi, F. Schmidt, R. Tomás, V. Vlachoudis
    CERN, Geneva, Switzerland
  • R. Appleby, D.R. Brett
    UMAN, Manchester, United Kingdom
  • D. Banfi, J. Barranco
    EPFL, Lausanne, Switzerland
  • B. Dalena
    CEA/IRFU, Gif-sur-Yvette, France
  • L. Lari
    IFIC, Valencia, Spain
  • V. Previtali
    Fermilab, Batavia, USA
  • G. Robert-Demolaize
    BNL, Upton, Long Island, New York, USA
  
  Funding: The HiLumi LHC Design Study is included in the HL-LHC project and is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404.
SixTrack is a symplectic 6D tracking code routinely used to simulate single particle trajectories in high energy circular machines like the LHC and RHIC. The paper presents the developments recently implemented and those foreseen for extending the physics models: exact Hamiltonian, different ions and charge states, RF multipoles, non-linear fringe fields, Taylor maps, e-lenses, ion scattering. Moreover new functionalities are also added like variable number of tracked particles, time dependent strengths, GPU computations with a refactoring of the core structure. The developments will benefit studies on the LHC and SPS, for collimation efficiency, ion operations, failure scenarios and HL-LHC design. 		 
 
TUPEA003 Components for CW and LP Operation of the XFEL Linac cavity, cryomodule, linac, cathode 1164
 
  • J.K. Sekutowicz
    DESY, Hamburg, Germany
  
  The European XFEL will use superconducting TESLA cavities operating with 650 μs long bunch trains. With 220 ns bunch spacing and 10 Hz RF-pulse repetition rate, up to 27000 high quality bunches/s will be delivered to insertion devices generating unprecedented high average brilliance photon beams at very short wavelength. While many experiments can take advantage of full bunch trains, others prefer an increased intra-pulse distance of several μ-seconds between bunches, or short bursts with a kHz repetition rate. In this contribution, we discuss progress in the R&D program for a future upgrade of the European XFEL linac, to operation in the continuous wave (cw) and long pulse (lp) mode, which will allow for much more flexibility in the electron and photon beam time structure. Modifications and cw tests of XFEL cryomodules, recent tests result of the SRF injector, test of the second prototype of 120 kW IOT are presented. In addition, computer modeling of the cw-operating TESLA-like cavity with modified HOM couplers is briefly discussed.  
 
TUPWA013 Study of the C-ADS Longitudinal Beam Instabilities Caused by HOMS linac, emittance, damping, simulation 1751
 
  • P. Cheng, Z. Li, J.Y. Tang, J.Q. Wang
    IHEP, Beijing, People's Republic of China
  
  The C-ADS accelerator is a CW proton linac which accelerates the beam to 1.5GeV. It has the characteristics of being very high beam power and very high reliability that are not posed by any of the existing proton linacs. The accelerator uses two families (β=0.63 and β=0.82 ) of elliptical five cell superconducting cavities. High Order Modes can severely limit the operation of these cavities. Monopole modes are found by Microwave Studio CST. Then the longitudinal instability caused by these monopole modes are primarily investigated with code bbusim, taking into account of effects like High Order Modes frequency spread, beam input jitters and other beam and RF parameters of the beams and cavities. Preliminary simulation results show that monopole modes induced instability is not a problem if High Order Modes frequency spread is not less than 1MHz. However, further investigations are necessary in order to make a critical decision such as whether HOM damper will be adopted. Study on the transverse case is under way.  
 
TUPWA021 Multi-Pass, Multi-Bunch Beam Breakup of ERLs with 9-cell Tesla Cavities cavity, betatron, dipole, simulation 1769
 
  • S. Chen, J.E. Chen, L.W. Feng, S. Huang, Y.M. Li, K.X. Liu, S.W. Quan, F. Zhu
    PKU, Beijing, People's Republic of China
  
  Funding: Supported by the Major State Basic Research Development Program of China under Grant No. 2011CB808303 and No. 2011CB808304
In this paper, multi-pass, multi-bunch beam break-up of some small-scale Energy Recovery Linac(ERL) configuration using 9-cell Tesla cavity is discussed. The threshold currents of different cases are investigated and some factors that influence the threshold currents are discussed. 		 
 
WEOAB101 Single Particle Tracking for Simultaneous Long and Short Electron Bunches in the BESSY II Storage Ring cavity, simulation, synchrotron, optics 2038
 
  • M. Ruprecht, A. Jankowiak, A. Neumann, M. Ries, G. Wüstefeld
    HZB, Berlin, Germany
  • T. Weis
    DELTA, Dortmund, Germany
  
  A scheme where 1.5 ps and 15 ps long bunches (rms) can be stored simultaneously in the BESSY II storage ring has recently been proposed (BESSYVSR*). This paper presents simulations of single particle beam dynamics influenced by superconducting cavities used for the strong longitudinal beam focusing. The effect of RF jitter on (very short) bunches is investigated and results are discussed. Furthermore, possible effects on beam dynamics during ramp up and ramp down of the high gradient fields in the cavities are studied. The primary goal is to reveal preliminary design specifications for RF jitter on the basis of single particle dynamics.
* G. Wüstefeld, A. Jankowiak, J. Knobloch, M. Ries, Simultaneous Long and Short Electron Bunches in the BESSY II Storage Ring, Proceedings of IPAC2011, San Sebastián, Spain 		 
slides icon Slides WEOAB101 [3.955 MB]  
 
WEIB203 Industrialization of ILC from a View Point of Industry cavity, target, vacuum, status 2110
 
  • K. Sennyu, H. Hara, F. Inoue, K. Kanaoka, K. Okihira
    MHI, Hiroshima, Japan
  
  Cavity performance has been improved by various efforts to meet the ILC spec stably in these days. For industrialization, not only Quality but also Cost and Delivery time, that is, QCD are important. We report our activities for stable quality and cost reduction in this report.  
slides icon Slides WEIB203 [5.789 MB]  
 
WEIB205 Promoting Local Economic Development by an Integration of Industry, Teaching and Research of Compact Low Energy Accelerators electron, radiation, permanent-magnet, high-voltage 2119
 
  • M. Fan, D.Z. Chen, J. Huang, D. Li, K.F. Liu, B. Qin, Y.Q. Xiong, J. Yang, T. Yu
    HUST, Wuhan, People's Republic of China
  • H.Q. Gao
    Hubei University of Science and Technology, Hubei, People's Republic of China
  
  Huazhong University of Science and Technology has been carrying out R&D of compact low energy accelerators by integrating industry, teaching and research to promote local economic development supported by both national and provincial government and local enterprises. Currently, the projects include: compact medical cyclotron, electron irradiation accelerators, etc. The industry of non-power nuclear energy based on low energy particle accelerator has also drawn attention from the provincial government of Hubei and municipal government of Xianning. Meanwhile, a series of lectures about nuclear science and nuclear safety were hosted to help the public better understand nuclear technology and to wipe out fears of nuclear energy. At the moment, the application of non-power nuclear energy with based on compact low energy accelerator is developing into an industry chain in the area of central China.  
slides icon Slides WEIB205 [2.311 MB]  
 
WEPWA068 Design Concepts for the NGLS Linac cavity, linac, cryomodule, cryogenics 2271
 
  • A. Ratti, J.M. Byrd, J.N. Corlett, L.R. Doolittle, P. Emma, J. Qiang, M. Venturini, R.P. Wells
    LBNL, Berkeley, California, USA
  • C. Adolphsen, C.D. Nantista
    SLAC, Menlo Park, California, USA
  • D. Arenius, S.V. Benson, D. Douglas, A. Hutton, G. Neil, W. Oren, G.P. Williams
    JLAB, Newport News, Virginia, USA
  • C.M. Ginsburg, R.D. Kephart, T.J. Peterson, A.I. Sukhanov
    Fermilab, Batavia, USA
  
  The Next Generation Light Source (NGLS) is a design concept for a multibeamline soft x-ray FEL array powered by a ~2.4 GeV CW superconducting linear accelerator, operating with a 1 MHz bunch repetition rate. This paper describes the concepts under development for a linac operating at 1.3 GHZ and based on minimal modifications to the design of ILC cryomodules in order to leverage the extensive R&D that resulted in the ILC design. Due to the different nature of the two applications, particular attention is given here to high loaded Q operation andμphonics control, as well as high reliability and expected up time.  
 
WEPWO010 BERLinPro Seven-cell SRF Cavity Optimization and HOMs External Quality Factors Estimation cavity, factory, SRF, simulation 2331
 
  • T. Galek, K. Brackebusch, T. Flisgen, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  • J. Knobloch, A. Neumann
    HZB, Berlin, Germany
  • B. Riemann, T. Weis
    DELTA, Dortmund, Germany
  
  Funding: Work funded by EU FP7 Research Infrastructure Grant No. 227579 and by German Federal Ministry of Research and Education, Project: 05K10HRC.
The main scope of this work is the optimization of the superconducting radio frequency (SRF) accelerating cavity design for the Berlin Energy Recovery Linac Project (BERLinPro)*. BERLinPro shall serve as a demonstrator for 100-mA-class ERLs with CW LINAC technology. High-current operation requires an effective damping of higher-order modes (HOMs) of the 1.3 GHz main-linac cavities. Consequently it is important, at the SRF cavity design optimization stage, to calculate the external quality factors of HOMs to avoid beam break up (BBU) instabilities. The optimization of the SRF cavity design consists of two steps. In the first step the cavities' end half-cells are tuned with respect to field flatness, effective shunt impedance and geometrical factor of the fundamental accelerating mode using robust eigenmode simulations. The second step involves frequency domain simulations and the extraction of external quality factors of HOMs from transmission S-parameter spectra using vector fitting procedure and an automated scheme to remove non-static poles **. The eigenmode,as well as the frequency domain simulations are performed using CST Microwave Studio ***.
* A. Neumann et al., Proc. of ICAP2012, pp. 278–280.
** T. Galek et al., Proc. of ICAP2012, pp. 152–154.
*** CST AG, http://www.cst.com 		 
 
WEPWO012 XFEL 3.9 GHz Prototype Cavities Tests cavity, pick-up, status, diagnostics 2337
 
  • P. Pierini, M. Bertucci, A. Bosotti, C. Maiano, P. Michelato, L. Monaco, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • E.R. Harms
    Fermilab, Batavia, USA
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  • E. Vogel
    DESY, Hamburg, Germany
  
  In preparation for the XFEL components production, three prototype cavities have been manufactured and vertically tested at INFN-LASA. Several tests, with and without HOM antennas and in a double cavity test configuration, have been performed. Further tests of one of the prototypes took place at FNAL, to validate results between the two test facilities. Results were consistent with those obtained at INFN-LASA.  
 
WEPWO013 High Power Tests of Injector Cryomodule for Compact-ERL cavity, cryomodule, radiation, accelerating-gradient 2340
 
  • E. Kako, D.A. Arakawa, K. Hara, T. Honma, H. Katagiri, Y. Kojima, Y. Kondo, S. Michizono, T. Miura, H. Nakai, H. Nakajima, K. Nakanishi, S. Noguchi, T. Shishido, T. Takenaka, K. Watanabe, Y. Yamamoto
    KEK, Ibaraki, Japan
  • H. Hara, H. Hitomi, K. Sennyu
    MHI, Kobe, Japan
  
  In the cERL injector cryomodule, electron beams of 10 mA are accelerated from the beam energy of 500 keV to 5 MeV. A three 2-cell cavity system was chosen for the cERL injector. Each cavity is driven by two input couplers to reduce a required RF power handling capacity and also to compensate a coupler kick. In the cERL injector cryomodule, critical hardware components are not superconducting cavities but RF input couplers operating in CW mode. Six input couplers for the installation in the cryomodule were fabricated, and three pairs of input couplers were carefully conditioned. Costruction status, cool-down tests and high power RF test results on injector cryomodule for compact-ERL at KEK will be discussed in this paper.  
 
WEPWO016 Construction of Main Linac Cryomodule for Compact ERL Project cryomodule, cavity, linac, radiation 2349
 
  • K. Umemori, K. Enami, T. Furuya, H. Sakai, M. Satoh, K. Shinoe
    KEK, Ibaraki, Japan
  • E. Cenni
    Sokendai, Ibaraki, Japan
  • M. Sawamura
    JAEA, Ibaraki-ken, Japan
  
  Compact ERL (cERL), which is a test facility of ERL, is under construction at KEK, in Japan. At the first stage of cERL project, electron beam will be accelerated by 30 MV at main linac region. We have developed a main linac cryomodule, which contains two L-band 9-cell superconducting cavities. Cavity assembly work was carefully done at a class-10 clean room and HOM absorbers and cold windows of input couplers were successfully mounted on the cavities. Next, the frequency tuners, thermal anchors, magnetic shields and temperature sensors and so on were assembled to the cryomodule. Then, using a clean-booth, warm windows of the input couplers are connected to the cold windows and gate valves were also attached to the both ends of the cryomodule. Finally, the cryomodule was installed into the beamline of cERL and connected to a 2K cryogenic system. Target of alignment precision of the cavities, after cooling down to 2K, are set to be within 1 mm against the beamline. The first cool-down test, followed by low power and high power measurements, is scheduled within the year 2012.  
 
WEPWO018 Status of the IHEP 1.3 GHz Superconducting RF Program for the ILC cavity, cryomodule, SRF, vacuum 2355
 
  • J. Gao, Y.L. Chi, J.P. Dai, R. Ge, T.M. Huang, S. Jin, C. H. Li, S.P. Li, Z.Q. Li, H.Y. Lin, Y. Liu, Z.C. Liu, Q. Ma, Z.H. Mi, W.M. Pan, Y. Sun, J.Y. Zhai, T.X. Zhao, H.J. Zheng
    IHEP, Beijing, People's Republic of China
  
  The 1.3 GHz superconducting radio-frequency (SRF) technology is one of the key technologies for the ILC. IHEP is building an SRF Accelerating Unit, named the IHEP ILC Test Cryomodule (IHEP ILC-TC1), for the ILC SRF system integration study, high power horizontal test and possible beam test in the future. In this paper, we report the components test results and the assembly preparation of this cryomodule. Processing and vertical test of the large grain low-loss shape 9-cell cavity is done. Performance of the in-house made high power input coupler and tuner at room temperature reaches the ILC specification.  
 
WEPWO022 IHEP03 Fabrication and Testing Status cavity, niobium, cryomodule, status 2364
 
  • Z.C. Liu, J. Gao, S. Jin, Y. Liu, J.Y. Zhai, T.X. Zhao, H.J. Zheng
    IHEP, Beijing, People's Republic of China
  • J.X. Wang, H. Yu, H. Yuan
    BIAM, Beijing, People's Republic of China
  
  IHEP is developing RF superconducting technology with different type of superconducting cavities. Tesla-like cavity which is designed by KEK is one of them. We have fabricated all the parts of the cavity using Nb material from Ningxia and cavity welding will be started soon. This paper will show the cavity fabrication procedures and measurement results.  
 
WEPWO026 HOM Parameters Simulation and Measurement Result of the IHEP02 Low-loss Cavity cavity, dipole, damping, wakefield 2372
 
  • H.J. Zheng, J. Gao, S. Jin, Y. Liu, Z.C. Liu, Z.H. Mi, J.Y. Zhai, T.X. Zhao
    IHEP, Beijing, People's Republic of China
  • H. Yuan
    BIAM, Beijing, People's Republic of China
  
  In cavities , there exists not only the fundamental mode which is used to accelerate the beam but also higher order modes(HOMs). The higher order modes excited by beam can seriously affect beam quality, especially for the higher R/Q mode. This paper reports on recent measurements of higher order modes in the IHEP-2 low-loss SRF cavity. Using different methods, the Qext of the dangerous modes passband are got. This result is compared with TESLA result. R/Q of the first three passbands are also got by CST and compared with the results of TESLA cavity and STFBaseline cavity.  
 
WEPWO047 A Double Quarter-Wave Deflecting Cavity for the LHC cavity, multipole, higher-order-mode, simulation 2408
 
  • R. Calaga
    CERN, Geneva, Switzerland
  • S.A. Belomestnykh, I. Ben-Zvi, J. Skaritka, Q. Wu, B. P. Xiao
    BNL, Upton, Long Island, New York, USA
  
  Funding: The HiLumi LHC Design Study (a sub-system of HL-LHC) is cofunded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404
An asymmetric quarter wave deflecting cavity at 400 MHz for crab crossing in the LHC was already proposed in 2011. Due to improved cancellation of on-axis longitudinal field and the higher order components of the deflecting field, a symmetric version is now considered as the baseline for the quarter wave geometry. Relevant RF properties of the symmetric cavity are compared to the original asymmetric cavity. Some aspects of input coupler design, higher order modes, multipacting and frequency tuning are also addressed. 		 
 
WEPWO048 Investigation of a Ridge-loaded Waveguide Structure for CLIC X-band Crab Cavity cavity, damping, beam-loading, impedance 2411
 
  • V.F. Khan, R. Calaga, A. Grudiev
    CERN, Geneva, Switzerland
  
  In conventional crab cavities the TM11 mode is used to deflect the beam. In a linear collider such as CLIC, it is necessary to damp all the other modes, namely the accelerating i.e. lower order mode (LOM), same order mode (SOM) and higher order modes (HOMs). In addition to this, as the TM11 mode is not the fundamental mode, it is generally not excited with the highest shunt impedance. This necessitates damping of the high shunt impedance modes to acceptable level. Here we report on the investigation of an alternative design of the X-band crab cavity for CLIC based on ridge-loaded waveguide. In this type of cavity, the deflecting mode is the fundamental mode and has the maximum shunt impedance. However, the geometry of the cavity is chosen to optimise the ratio of group velocity to shunt impedance to minimise the effect of beam loading. The other modes are excited above the crabbing mode and are damped using wave-guides. Another advantage of this type of cavity is, unlike the conventional TM11 mode cavities, the e.m. surface fields do not peak at the iris. This provides ample margin to optimise the cavity geometry and reach the desired field distribution.  
 
WEPWO049 A Proposal for an ERL Test Facility at CERN cavity, linac, electron, SRF 2414
 
  • R. Calaga, E. Jensen
    CERN, Geneva, Switzerland
  
  An energy recovery linac at 300-400 MeV is proposed as a test facility using a two-pass two-cryomodule concept as a proof of principle for a future ERL based electron-ion collider. This facility will enable both the development and validation of the required SRF technology performance and ERL specific beam dynamics essential for the future collider. Furthermore, the test facility can be used as the injector to the main linac in future. The test facility proposal, its potential uses and some aspects of the RF system are presented.  
 
WEPWO053 SRF Development for a MW Proton Source at Fermi National Accelerator Laboratory cryomodule, cavity, linac, SRF 2423
 
  • T.T. Arkan, C.M. Ginsburg, A. Grassellino, S. Kazakov, T.N. Khabiboulline, T.H. Nicol, Y. Orlov, T.J. Peterson, L. Ristori, A. Romanenko, A.M. Rowe, N. Solyak, A.I. Sukhanov, V.P. Yakovlev
    Fermilab, Batavia, USA
  
  Funding: Work supported by the US Department of Energy
Fermilab is planning a megawatt-level proton beam facility utilizing niobium superconducting RF (SRF) cavities. Project X at Fermilab will eventually provide high-intensity beams for research into the nature of matter at the "intensity frontier". Research and development in several areas will bring the SRF technology to the level needed for this application. Among developments in SRF being pursued with our national and international collaborators are 162.5 MHz half-wave resonators, 325 MHz single-spoke resonators, and two types of elliptical multi-cell 650 MHz cavities. Performance requirements for these cavities and cryomodules in continuous wave (CW) operation are extremely stringent in order to provide high accelerating gradients with acceptable total cryogenic load and overall accelerator capital and operating costs. This paper presents some highlights of the SRF R&D program and proton linac development work at Fermilab. 		 
 
WEPWO059 Cornell's HOM Beamline Absorbers linac, cavity, damping, cryomodule 2441
 
  • R. Eichhorn, J.V. Conway, Y. He, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, P. Quigley, J. Sears, V.D. Shemelin, N.R.A. Valles
    CLASSE, Ithaca, New York, USA
  
  The proposed energy recovery linac at Cornell aims for high beam currents and short bunch lengths, the combination of which requires efficient damping of the higher order modes (HOMs) being present in the superconducting cavities. Numerical simulations show that the expected HOM power could be as high as 200 W per cavity with frequencies ranging to 40 GHz. Consequently, a beam line absorber approach was chosen. We will review the design, report on first results from a prototype and discuss further improvements.  
 
WEPWO060 The CW Linac Cryo-module for Cornell’s ERL linac, cavity, damping, status 2444
 
  • R. Eichhorn, Y. He, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich
    CLASSE, Ithaca, New York, USA
  
  Cornell University has proposed an energy-recovery linac (ERL) based synchrotron-light facility which can provide greatly improved X-ray beams due to the high electron-beam quality that is available from a linac. As part of the phase 1 R&D program, critical challenges in the design were addressed, one of them being a full linac cryo-module. It houses 6 superconducting cavities- operated at 1.8 K in cw mode- HOM absorbers and a magnet/ BPM section. We will present the design being finalized recently and report on the fabrication status that started in late 2012.  
 
WEPWO065 Optimization of Elliptical SRF Cavities for β <1 cavity, SRF, niobium, simulation 2450
 
  • V.D. Shemelin
    CLASSE, Ithaca, New York, USA
  • J. Newbolt
    Rochester University, Rochester, New York, USA
  
  Funding: NSF award DMR-0807731
A systematic approach to optimization of SRF cavities which was done earlier for β=1 is extended to β<1 Some improvements for earlier developed designs are proposed. 		 
 
WEPWO068 Cornell ERL Main Linac 7-cell Cavity Performance in Horizontal Test Cryomodule Qualifications cavity, linac, cryomodule, higher-order-mode 2459
 
  • N.R.A. Valles, R. Eichhorn, F. Furuta, G.M. Ge, D. Gonnella, Y. He, K.M.V. Ho, G.H. Hoffstaetter, M. Liepe, T.I. O'Connell, S. Posen, P. Quigley, J. Sears, V. Veshcherevich
    CLASSE, Ithaca, New York, USA
  
  Funding: NSF DMR-0807731
Cornell has recently finished producing and testing the first prototype 7-cell main linac cavity for the Cornell Energy Recovery Linac, and completed the prototype cavity qualification program. This paper presents quality factor results from the horizontal test cryomodule (HTC) measurements, from the HTC-1 through HTC-3 experiments, reaching Q's up to 6 x 1010 at 1.6 K. We investigate the effect of thermal cycling on cavity quality factor and show that high quality factors can be preserved from initial mounting to fully outfitting the cavity with side-mounted input coupler and beam line absorbers. We also discuss the production of six additional main-linac cavities as we progress toward constructing a full 6-cavity cryomodule. 		 
 
WEPWO069 HOM Studies of the Cornell ERL Main Linac Cavity: HTC-1 Through HTC-3 cavity, cryomodule, linac, higher-order-mode 2462
 
  • N.R.A. Valles, R. Eichhorn, G.H. Hoffstaetter, M. Liepe
    CLASSE, Ithaca, New York, USA
  
  Funding: Supported by NSF grant DMR-0807731
The Cornell energy recovery linac is designed to run a high energy (5 GeV), high current (100 mA), very low emittance beam (30 pm at 77 pC bunch charge). A major challenge to running such a large current continuously through the machine is the effect of strong higher-order modes(HOMs) that can lead to beam breakup. This paper presents the results of HOM studies for the prototype 7-cell cavity installed in a horizontal test cryomodule (HTC) from initial RF test, to being fully outfitted with side-mounted input coupler and beam line absorbers. We compare the simulated results of the optimized cavity geometry with measurements from all three HTC experiments. 		 
 
WEPWO072 HOM Damping Coupler Design for the 400-MHz RF Dipole Compact Crab Cavity for the LHC HiLumi Upgrade cavity, dipole, damping, coupling 2468
 
  • Z. Li, L. Ge
    SLAC, Menlo Park, California, USA
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  
  Funding: Work partially supported by the US DOE through the US LHC Accelerator Research Program (LARP), and by US DOE under contract number DE-AC02-76SF00515.
Crab cavities are adapted as the baseline design for the LHC HiLumi upgrade to achieve head-on beam-beam collisions for further improvement in luminosity. A 400-MHz compact RF dipole crab cavity design was developed by a joint effort between Old Dominion University and SLAC under the support of US LARP program. This design has shown very favorable RF parameters and can fit into the available beamline spacing for either vertical and horizontal crabbing schemes. A niobium prototype cavity based on such a design has been manufactured for vertical test. In addition, there are stringent wakefield requirements that needed to be met for such a cavity in order to preserve the quality of the circulating beams. In this paper, we will discuss different damping schemes for such a compact design and present the HOM coupler designs to meet the damping requirements. 		 
 
WEPWO080 Compact Superconducting RF-dipole Cavity Designs for Deflecting and Crabbing Applications dipole, cavity, multipole, higher-order-mode 2483
 
  • S.U. De Silva, A. Castilla, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • A. Castilla
    DCI-UG, León, Mexico
  
  Over the years the superconducting parallel-bar design has evolved into an rf-dipole cavity with improved properties. The new rf-dipole design is considered for number of deflecting and crabbing applications. Some of those applications are the 499 MHz rf separator system for the Jefferson Lab 12 GeV upgrade, 400 MHz crabbing cavity system for the proposed LHC high luminosity upgrade, and 750 MHz crabbing cavity for the medium energy electron-ion collider in Jefferson Lab. In this paper we present the optimized rf design in terms of rf performance including rf properties, higher order mode properties, multipacting, multipole expansion for the above mentioned applications.  
 
WEPWO084 Improvement of the Q-factor Measurement in RF Cavities cavity, dipole, coupling, pick-up 2489
 
  • W. Xu, S.A. Belomestnykh, I. Ben-Zvi, H. Hahn
    BNL, Upton, Long Island, New York, USA
  • S.A. Belomestnykh, I. Ben-Zvi
    Stony Brook University, Stony Brook, USA
  
  Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S.
The Q values of Higher-order-modes (HOMs) in RF cavities are measured at room temperature with the 3 dB bandwidth reading by a network analyzer. The resonant curve distortion is created by the resonance splitting due to the ellipticity caused by manufacture tolerance and RF ports. Therefore, the measured Q values are usually lower than the simulated or theoretical Q values. In some cases, even only one mode’s Q can be measured with the 3 dB method. There may be two reasons for this happening. One is that only one mode was excited and the neighbor splitmode was close to 90° polarized; the other reason is that the resonant curve of one mode was distorted by the other mode too much to measure the 3dB range. In this paper, we resolve this issue by looking into the RF measurement setup, including cavity, input coupler and pick-up coupler, from the equivalent circuit and wave point of view. Based on the BNL3 copper prototype cavity, we compared these results from measurement and simulation. 		 
 
WEPWO085 Commissioning SRF Gun for the R&D ERL at BNL gun, SRF, cavity, simulation 2492
 
  • W. Xu, Z. Altinbas, S.A. Belomestnykh, I. Ben-Zvi, S. Deonarine, D.M. Gassner, H. Hahn, J.P. Jamilkowski, P. Kankiya, D. Kayran, N. Laloudakis, L. Masi, G.T. McIntyre, D. Pate, D. Phillips, T. Seda, K.S. Smith, A.N. Steszyn, T.N. Tallerico, R. Than, R.J. Todd, D. Weiss, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
  • S.A. Belomestnykh, I. Ben-Zvi, J. Dai
    Stony Brook University, Stony Brook, USA
  
  Funding: This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S.
The R&D ERL project at BNL aims to demonstrate a high charge, high current energy recovery linac. One of the key SRF system is the 704 MHz half-cell SRF gun. The SRF gun is designed to deliver up to 0.5 A beam at 2 MeV with 1 MW of CW RF power. The gun commissioning started in November 2012. The first photoemission beam from the SRF gun is expected in early 2013. This presentation will discuss the results of the SRF gun commissioning, and the performance of the high-power RF system. 		 
 
WEPWO086 Split Higher Order Modes in Superconducting Cavities resonance, cavity, dipole, higher-order-mode 2495
 
  • H. Hahn, S.A. Belomestnykh, W. Xu
    BNL, Upton, Long Island, New York, USA
  
  Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE and award no. DE-SC0002496 to Stony Brook University with the US DOE.
Split resonances are a common appearance in superconducting cavities and were studied here on the specific example of the TE11 dipole resonance in five-cell copper models of the ERL and BNL3. The BNL3 cavity was designed to be suitable for the envisioned electron-hadron collider eRHIC. Achieving the required high-current performance depends on avoiding beam break-up instabilities by minimizing the Higher Order Modes (HOM) Q-values. This was attempted in the design phase and will be done with appropriate mode dampers in operation. The availability of a copper model provided a convenient opportunity to confirm the design and to study potentially nefarious high-Q resonances. The appearance of split resonances impeded the HOM identification and the theoretical interpretation as elipticity deformation is presented in this report. 		 
 
WEPFI004 Commissioning of First 352.2 MHz - 150 kW Solid State Amplifiers at the ESRF and Status of R&D booster, cavity, storage-ring, status 2708
 
  • J. Jacob, L. Farvacque, G. Gautier, M.L. Langlois, J.M. Mercier
    ESRF, Grenoble, France
  
  Funding: This work receives funding from the EU as work package WP7 in the FP7/CRISP project.
Four 352.2 MHz - 150 kW Solid State Amplifiers (SSA), based on the SOLEIL design and supplied by ELTA/AREVA, are in operation on the ESRF booster since April 2012. A number of interesting effects were observed during commissioning that are inherent to the combination of many RF amplifier modules at high power. While it has only little impact on the booster SSA operated in pulsed regime, some modifications were necessary for the three SSAs that will be delivered by ELTA for an operation in CW on the storage ring. In parallel, the ESRF is developing a more compact SSA using cavity combiners *) instead of the widely adopted coaxial combiner trees. The status of this R&D project will also be reported. 		 
 
WEPFI005 Simulations and RF Measurements of the Fundamental and Higher Order Modes of the ThomX 500 MHz Cavity cavity, impedance, feedback, controls 2711
 
  • M. El Khaldi, I.V. Drebot, P. Lepercq, R. Marie, B. Mercier, T. Roulet, A. Variola, F. Wicek
    LAL, Orsay, France
  • H.D. Dias, M.D. Diop, M.E. El Ajjouri, R. Lopes, A. Loulergue, P. Marchand, F. Ribeiro, R. Sreedharan
    SOLEIL, Gif-sur-Yvette, France
  
  The RF system of the ThomX* storage ring consists in a 500 MHz single cell copper cavity of the ELETTRA type, powered with a 50 kW CW solid state amplifier, and the associated Low Level RF feedback and control loops. The low operating energy of 50 – 70 MeV makes the impedances of the cavity higher order modes (HOMs) particularly critical for the beam stability. Their parasitic effects on the beam can be cured by HOM frequency shifting techniques, based on a fine temperature tuning and a dedicated plunger. A typical cavity temperature stability of ± 0.05°C within a range from 35 up to 80 °C can be achieved by a precise control of its water cooling temperature. On the other hand, the tuning of the cavity fundamental mode is achieved by changing its axial length by means of a mechanical tuner. In order to insure a fine control of the HOM frequencies, a good knowledge of their characteristics is mandatory. The main parameters of the fundamental and of the HOMs up to 4 GHz have been calculated using the HFSS and CST MWS codes. Preliminary measurements results have been obtained and show a good agreement with the simulations.
* A.Variola, “The ThomX Project”, Proceedings of IPAC2011, San Sebastián, Spain 		 
 
WEPFI006 Broad and Narrow Band Feedback Systems at ELSA feedback, cavity, kicker, damping 2714
 
  • M. Schedler, F. Frommberger, P. Hänisch, W. Hillert, C. Reinsch
    ELSA, Bonn, Germany
  
  At the Electron Stretcher Facility ELSA of Bonn University, an upgrade of the maximum stored beam current from 20 mA to 200 mA is planned. The storage ring operates applying a fast energy ramp of 6 GeV/s from 1.2 GeV to 3.5 GeV. The intended upgrade is mainly limited due to the excitation of multibunch instabilities. As a countermeasure, we succesfully commissioned state-of-the-art bunch by bunch feedback systems in the longitudinal and the two transverse dimensions. In addition, a narrow band cavity based feedback system for damping the most harmful longitudinal multi bunch mode caused by a HOM of the accelerating cavities is under construction.  
 
WEPFI007 Amplitude, Phase and Temperature Stabilization of the ELSA RF System cavity, LLRF, controls, feedback 2717
 
  • D. Sauerland, W. Hillert, A. Roth, M. Schedler
    ELSA, Bonn, Germany
  • D. Teytelman
    Dimtel, San Jose, USA
  
  In the stretcher ring of the accelerator facility ELSA electrons are accelerated to a maximum energy of 3.2 GeV applying a fast energy ramp of up to 6 GeV/s. In order to be able to offer higher external beam currents one has to increase the current of the internal beam in ELSA accordingly. The beam current is limited due to excitation of multi bunch instabilities which are mainly caused by higher order modes of the two PETRA cavities used for particle acceleration in the stretcher ring. To control the resonance frequency of these modes, a variable bypass of the cavities' cooling system has been installed which allows a stabilization of their temperature. With this modification, it is possible to vary the temperature of the cavities between 26 °C and 65 °C and thus to shift the higher order modes by hundreds of kHz in frequency. Additionally, first operational studies with a prototype of a FPGA based LLRF system (Dimtel) have been performed which in future will be used to stabilize the amplitude and phase of the accelerating RF fields of the cavities.  
 
WEPFI012 Conceptual Design of ILSF RF System cavity, LLRF, storage-ring, impedance 2723
 
  • Kh.S. Sarhadi, H. Ajam, H. Azizi, M. Fereidani, M. Jafarzadeh, S. Pirani, J. Rahighi, R. Safian, A. Shahverdi
    ILSF, Tehran, Iran
  
  The Iranian Light Source Facility (ILSF) RF system, consisting of RF cavities, power sources and low-level RF systems, is conceptually designed in accordance with the requirements of ILSF 3GeV storage ring. To achieve the desired 400mA beam current, utilization of the existing HOM-damped cavities is explored and RF system parameters are compared based on the usage of each cavity. Moreover, the choice of solid state amplifier as the RF power source is presented with its available power and structure. This paper, furthermore, explains the conceptual design and functionality of the selected digital LLRF system.  
 
WEPFI018 Comparison of High Gradient Performance in Varying Cavity Geometries damping, vacuum, coupling, acceleration 2741
 
  • T. Higo, T. Abe, Y. Arakida, Y. Higashi, S. Matsumoto, T. Shidara, T. Takatomi, M. Yamanaka
    KEK, Ibaraki, Japan
  • A. Grudiev, G. Riddone, W. Wuensch
    CERN, Geneva, Switzerland
  
  Four types of CLIC prototype TW accelerator structures were high-gradient tested at Nextef, KEK, up to 100 MV/m level and the fifth is under test now. The ramping speed of each processing and the resultant breakdown rate were compared among them. From this comparison, it was found that the ramping speed of the structures with opening ports for HOM damping with magnetic coupling became slow and the resultant breakdown rate became high. It was also found that that with lower surface magnetic field showed faster ramping in processing and lower breakdown rate. This indicates the role of the magnetic field on vacuum breakdowns in copper structure at the region of several tens to 100 MV/m. In this paper, we review the processing stage and the high gradient performance of these structures trying to discuss the relevant parameters, surface electric field, surface magnetic field and other parameters such as Sc, “complex pointing vector”, to the performance difference.  
 
WEPFI059 C-band RF Pulse Compressor for SwissFEL coupling, resonance, cavity, klystron 2827
 
  • R. Zennaro, M. Bopp, A. Citterio, R. Reiser, T. Stapf
    PSI, Villigen PSI, Switzerland
  
  The SwissFEL C-band (5.712 GHz) linac consists of 28 RF modules. Each module is composed of a single 50 MW klystron feeding a pulse compressor and four two meter long accelerating structures. The pulse compressor is based on a single Barrel Open Cavity (BOC). The BOC makes use of a “whispering gallery” mode which has an intrinsically high quality factor and operates in resonant rotating wave regime; moreover, and contrary to the conventional SLED scheme, a single cavity is sufficient to define the pulse compressor, without the need for two cavities and a 3-dB hybrid. A prototype has been manufactured and successfully tested. A short description of the BOC is presented, together with the prototype design, production, low level RF measurements, and high power test.  
 
WEPFI079 Electromagnetic Modeling of RF Drive in the LANSCE DTL cavity, coupling, DTL, simulation 2878
 
  • S.S. Kurennoy
    LANL, Los Alamos, New Mexico, USA
  
  A 3D electromagnetic model of the RF drive module in the LANSCE DTL tank 4 has been developed with the CST MicroWave Studio. The model is explored both with eigensolver and in time domain to evaluate maximal fields in the drive module and RF coupling. Here we describe the model and present simulation results.  
 
WEPME063 Progress Report on Development of a 5-μm Drive Laser for Dielectric Laser Acceleration laser, acceleration, focusing, alignment 3079
 
  • G. Xu, I. Jovanovic, S.F. Wandel
    Penn State University, University Park, Pennsylvania, USA
  • E.R. Arab
    PBPL, Los Angeles, USA
  • P.D. Hoang, P. Musumeci, B.D. O'Shea, J.B. Rosenzweig
    UCLA, Los Angeles, USA
  • A.Y. Murokh, A.G. Ovodenko
    RadiaBeam, Santa Monica, USA
  • I. Pogorelsky
    BNL, Upton, Long Island, New York, USA
  
  Funding: This work has been sponsored by Defense Advanced Research Project Agency.
A simple and robust ultrafast, high-peak-power 5-μm laser source for pumping a dielectric photonic structure for high-gradient electron acceleration has been designed and is being constructed. The use of long wavelength drive lasers can mitigate the problem of dielectric structure breakdown caused by multiphoton ionization. In addition, structure fabrication requirements are relaxed, and greater energy can be stored in the structure. The 5-μm laser source consists of two components: (1) a type-II-beta-barium borate-based 2-μm optical parametric amplifier (OPA) as a pump source, and (2) a type-I-zinc-germaniu-phosphate-based 5-μm OPA to produce mJ-class, <100 fs pulses. Our supercontinuum seeded two-stage 2-μm OPA is pumped by a Ti:sapphire amplifier and produces pulse energy of ~1.4 mJ with a pulse duration of 42 fs (~6 optical cycles). Carrier-envelope phase (CEP) stabilization is passively established for 2 μm pulses in our OPA design. An modified design of seed pulse generation for the 5-μm OPA based on several cascaded parametric processes can also result in CEP-stable operation for 5-μm amplified pulses. 		 
 
THOBB203 Study on Fabrication of Superconducting RF 9-cell Cavity for ILC at KEK cavity, electron, gun, status 3132
 
  • T. Saeki, Y. Ajima, K. Enami, H. Hayano, H. Inoue, E. Kako, S. Kato, S. Koike, T. Kubo, S. Noguchi, M. Satoh, M. Sawabe, T. Shishido, A. Terashima, N. Toge, K. Ueno, K. Umemori, K. Watanabe, Y. Watanabe, S. Yamaguchi, A. Yamamoto, Y. Yamamoto, M. Yamanaka, K. Yokoya
    KEK, Ibaraki, Japan
  • Y. Iwashita
    Kyoto ICR, Uji, Kyoto, Japan
  • N. Kawabata, H. Nakamura, K. Nohara, M. Shinohara
    SPS, Funabashi-shi, Japan
  • F. Yasuda
    The University of Tokyo, Institute of Physics, Tokyo, Japan
  
  We constructed a new facility for the fabrication of superconducting RF cavity at KEK from 2009 to 2011. In the facility, we have installed a deep-drawing machine, a half-cell trimming machine, an electron-beam welding machine, and a chemical etching room in one place. We started the study on the fabrication of 9-cell cavity for International Linear Collier (ILC) from 2009 using this facility. The study is focusing on the cost reduction with keeping high performance of cavity, and the goal is the establishment of mass-production procedure for ILC. This article reports the current status of the studies in CFF.  
slides icon Slides THOBB203 [3.983 MB]  
 
THPEA042 TREC: Traceability of Radioactive Equipment at CERN radiation, controls, monitoring, background 3234
 
  • M.P. Kepinski, L. Bruno, Ch. Delamare, S. Mallon Amerigo, P. Martel, S. Petit, T. Schmittler, M.J.S. Tavlet, D. Widegren
    CERN, Geneva, Switzerland
  
  Activated accelerator components are frequently removed from service due to changes in design, configuration or maintenance work. Safe and effective management of such components is a necessity. Moreover, local authorities require the tracking of this equipment: any piece of equipment or waste which has been in a potentially radioactive area must be controlled by a radio protection responsible before leaving the accelerator premises. CERN must also be able to prove that the required measurements have been done and are properly stored in a computerized system. TREC is the official system used at CERN to trace potentially radioactive equipment. It replaces paper work by electronic data, manual phone calls by automatic email notifications and helps to enforce CERN safety rules. Some of the major benefits are the reduction of the delays related to equipment movements (from installation to workshops or waste storage areas) as well as increased personal safety. The system is fully integrated with the CMMS* tools used at CERN to ensure the complete equipment lifecycle’s traceability.
*CMMS: Computerized Maintenance Management System 		 
 
THPEA061 EPICS Accelerator Control System for the IAC-RadiaBeam THz Project controls, EPICS, power-supply, linac 3279
 
  • A. Andrews, B.L. Berls, T. Downer, C.F. Eckman, K. Folkman, Y. Kim, C. O'Neill, J. Ralph
    IAC, Pocatello, IDAHO, USA
  • P. Buaphad, Y. Kim
    ISU, Pocatello, Idaho, USA
  
  The Idaho Accelerator Center (IAC) of Idaho State University has been operating a 44 MeV L-band linac for various nuclear physics related applications. However, for the past several years, this research has been done without the aid of a modern computer based control system. To obtain a better reproducibility and stability in operation, the EPICS accelerator control system has been applied to control various components of this linac. This has been done for the purpose of a joint THz research project between IAC and RadiaBeam that was performed in November 2012. This paper describes the development of the EPICS accelerator control system used during this joint THz research experiment.  
 
THPFI047 Design Guidelines for Ferrite Absorbers Submitted to RF-induced Heating radiation, damping, pick-up, FEL 3394
 
  • A. Bertarelli, M. Garlaschè
    CERN, Geneva, Switzerland
  
  The use of ferrite absorbers is one of the most effective means of damping potentially harmful high order RF modes, which may lead to beam instabilities and excessive power losses in accelerator devices. However, the power deposited on ferrite absorbers themselves may lead to ferrite exceeding its Curie temperature, losing its damping properties. An evaluation of the ferrite capability to dissipate deposited heat is hence of paramount importance for the safe design of particle accelerator devices. In this paper, figures of merit are proposed to assess the maximum specific power allowed on a generic ferrite tile, before it reaches its Curie temperature. Due to its inherent brittleness, sufficient contact pressure between ferrite and its housing, allowing heat transmission by conduction, can hardly be applied. A semi-analytical study is thus performed, assuming that ferrite is evacuating heat solely through radiation. The described method is then exemplified in the case of the BPM-embedded tertiary collimator (TCTP) designed in the framework of the LHC collimation upgrade.  
 
THPFI090 Accuracy of Measurements of ε and μ of Lossy Materials simulation, higher-order-mode, insertion, damping 3499
 
  • V.D. Shemelin, J.J. Kaufman
    CLASSE, Ithaca, New York, USA
  
  Funding: NSF award DMR-0807731
Measurements of samples of lossy ceramic and ferrites for Higher Order Mode Loads are performed routinely in our Lab. Some difference of results for different batches of materials can be explained not only by technological deviations in the material production but also by errors in the dimensions of the measured samples. Simulations with MicroWave Studio for samples in the form of coaxial washers in the frequency range from 1 to 12.4 GHz helped to define the main sources of errors and to improve accuracy of measurements. 		 
 
THPME035 The Electronic System Design and Realization for First Set 500 MHz KEKB SRF Module High Power Test SRF, controls, cavity, cryogenics 3588
 
  • F.-T. Chung, L.-H. Chang, M.H. Chang, L.J. Chen, M.-C. Lin, Y.-H. Lin, Z.L. Liu, C.H. Lo, M.H. Tsai, Ch. Wang, T.-T. Yang, M.-S. Yeh, T.-C. Yu
    NSRRC, Hsinchu, Taiwan
  
  This article reports the home-made electronics circuits for reading the various electronics signals which can be used for site acceptance of superconducting resonant cavity. The adjustment of parameters during 1st SRF high power acceptance can also be used for the update of the 2nd electronics. The modular electronics system will provide the advantages of fast repair, preparing spare parts easily, short install time and flexible adjustment. The hardware whole electronics system is mainly designed by CPLD, PLC and Display meters. The Military Standard connectors are used for signals connection. There are always junction boxes for signal transmission test and convenient signal jumping for ensuring the correct signal source. In safety action, there are Fast Interlock Sum (0-10us) and slow ready chain (50ms-150ms). The complete system realizes the real time monitor and protection of superconducting resonant cavity.