Keyword: SRF
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MOPEA038 Coherent Wiggler Radiation of Picosecond CW Electron Beam Produced by DC-SRF Photoinjector wiggler, radiation, electron, acceleration 160
 
  • S. Huang, J.E. Chen, S. Chen, K.X. Liu, S.W. Quan, Zh.W. Wang, X.D. Wen, F. Zhu
    PKU, Beijing, People's Republic of China
  
  The DC-SRF photoinjector at Peking University is capable of providing CW electron beam with the energy of 3-5 MeV. The beam has high repetition rate, picosecond bunch length and high quality, which can be used to produce high repetition rate THz wave by wiggler radiation. Through off-crest acceleration, electron beam from the injector may be bunched, which will lead to coherent enhancement of the radiation power. With current setup of the DC-SRF injector and a 10-period wiggler, THz radiation power of 10s mW to a few watts can be achieved within the wavelength range of 200 μm to 500 μm. In this work, we will present the calculation results about THz radiation produced by the electron beam from DC-SRF photoinjector. The preparation for the experiments will be also described.  
 
MOPEA048 Operation Status of RF System for the PLS-II Storage Ring cryomodule, klystron, status, LLRF 187
 
  • M.-H. Chun, J.Y. Huang, Y.D. Joo, H.-G. Kim, S.H. Nam, C.D. Park, H.J. Park, I.S. Park, Y.U. Sohn, I.H. Yu
    PAL, Pohang, Kyungbuk, Republic of Korea
  
  Funding: Supported by the Korea Ministry of Science and Technology
The RF system of the Pohang Light Source-II (PLS-II) storage ring is operating at the 3.0GeV/200mA with two superconducting RF (SRF) cavities. Each RF station is composed with a 300kW klystron with power supply unit, transmission components, a digital LLRF and a SRF cavity. And a cryogenic system of 700W capacities is supplied the LHe and LN2 to three cryomodules of SRF cavities. The second SRF cavity is installed during at the beginning in 2013 and the third one will be installed during summer shutdown in 2014 for stable 400mA operation with all 20 insertion devices. Also the third high power RF station with a 300kW klystron, power supply unit and WR1800 waveguide components will be prepared in 2013. The third LLRF system is already installed, but improved stabilities of amplitude, phase and tuner control. This paper describes the present operation status and improve plan of the RF system for the PLS-II storage ring. 		 
 
MOPEA061 Operation Experience at Taiwan Light Source kicker, cavity, diagnostics, injection 220
 
  • Y.-C. Liu, H.H. Chen, H.C. Chen, S. Fann, S.J. Huang, J.A. Li, C.C. Liang, Y.K. Lin, Y.-H. Lin, M.-S. Yeh
    NSRRC, Hsinchu, Taiwan
  
  A matrix structure has been implemented for the purpose of successful operation of TLS and continuous progress of Taiwan Photon Source (TPS) construction. A dedicated and flexible manpower distribution has proven it could keep as same performance of TLS operation as possible. We will summarize the machine operation experience at TLS during TPS civil construction period.  
 
MOPFI003 SRF Photoinjector Cavity for BERLinPro cavity, cathode, gun, HOM 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.  
 
MOPFI080 Fabrication, Transport and Characterization of Cesium Potassium Antimonide Cathode in Electron Guns cathode, gun, laser, vacuum 461
 
  • T. Rao, S.A. Belomestnykh, I. Ben-Zvi, X. Liang, I. Pinayev, B. Sheehy, J. Skaritka, J. Smedley, E. Wang, T. Xin
    BNL, Upton, Long Island, New York, USA
  • R.R. Mammei, J.L. McCarter, M. Poelker
    JLAB, Newport News, Virginia, USA
  • M. Ruiz-Osés
    Stony Brook University, Stony Brook, USA
  
  a number of accelerator applications need high current, low emittance and high brightness electron beams. Recent studies have shown cesium potassium antimonide to be a robust photocathode capable of producing high peak and average currents. However, for some applications, the UHV conditions required for producing these cathodes necessitate their fabrication site to be physically removed from the gun location and the cathode to be transferred between the two sites in UHV load-lock chambers. We have fabricated two cathodes at BNL, transported and tested them in DC gun at JLab at 100 kV and 200 kV. These cathodes have delivered up to 8A/cm2 without significant degradation. Localized changes in the QE have been attributed to heating due to laser, increasing the QE at lower laser power, but damaging the cathode at higher power. Two more load-lock chambers have been built to transport and insert similar cathodes in SRF guns operating at 700 MHz and 112 MHz for the first time. In this paper, we will describe the design of the load-lock chambers, transfer mechanisms, transport of the cathodes over ~ 1000 km and the cathode performance in gun environment.  
 
MOPWO008 Eigenmode Computation for Elliptical Cavities Subject to Geometric Variation using Perturbative Methods cavity, simulation, factory, higher-order-mode 900
 
  • K. Brackebusch, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  
  Funding: Work supported by Federal Ministry for Research and Education BMBF under contracts 05H09HR5 and 05K10H.
Parametric studies of geometric variations are an essential part of the performance optimization and error estimation in the design of accelerator cavities. Using common eigenmode solvers the analysis of intentional and undesired geometric perturbations tend to be very extensive since any geometric variation involves an entire eigenmode recomputation. Perturbative methods constitute an efficient alternative for the computation of a multitude of moderately varying geometries. They require a common eigenmode computation of solely one (so called unperturbed) geometry and allow for deriving the eigenmodes of similar but modified (so called perturbed) geometries from these unperturbed eigenmodes. In [*],[**] the practicability of perturbative methods was already proven by means of simple cavity geometries. In this paper we investigate the applicability and efficiency for practically relevant cavities. For this, basic geometric parameters of elliptical cavities are varied and the respective eigenmodes are computed by using perturbative as well as common methods. The accuracy of the results and the computational effort of the different methods are compared.
*K. Brackebusch, H.-W. Glock, U. van Rienen, WEPPC096, IPAC 2011
**K. Brackebusch, U. van Rienen, MOPPC062, IPAC 2012 		 
 
MOPWO081 The Scheme of Beam Synchronization in MEIC ion, electron, collider, proton 1067
 
  • Y. Zhang, Y.S. Derbenev, A. Hutton
    JLAB, Newport News, Virginia, USA
  
  Funding: Supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357.
Synchronizing colliding beams at single or multiple collision points is a critical R&D issue in the design of a medium energy electron-ion collider (MEIC) at Jefferson Lab. The path-length variation due to changes in the ion energy, which varies over 20 to 100 GeV, could be more than several times the bunch spacing. The scheme adopted in the present MEIC baseline is centered on varying the number of bunches (i.e., harmonic number) stored in the collider ring. This could provide a set of discrete energies for proton or ions such that the beam synchronization condition is satisfied. To cover the ion energy between these synchronized values, we further propose to vary simultaneously the electron ring circumference and the frequency of the RF systems in both collider rings. We also present in this paper the requirement of frequency tunability of SRF cavities to support the scheme. 		 
 
WEOBB102 Design Integration of the FRIB Driver Linac linac, cryomodule, solenoid, ion 2055
 
  • Y. Zhang, N.K. Bultman, F. Casagrande, C.P. Chu, A. Facco, P.E. Gibson, Z.Q. He, K. Holland, M. Leitner, Z. Liu, F. Marti, D. Morris, S. Peng, E. Pozdeyev, T. Russo, J. Wei, Y. Yamazaki, Z. Zheng
    FRIB, East Lansing, Michigan, USA
  
  Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
FRIB driver linac will deliver all stable heavy ion beams with beam energy more than 200 MeV/u, and beam power on target up to 400 kW. As the first SRF linac for high power heavy ion beams, there are many technical challenges, and integration of all the accelerator components is important. In this paper, major issues on integration of the FRIB drive linac are introduced and the corresponding studies are discussed, which include developments of accelerator online model, minimize uncontrolled beam loss in the SRF linac for high power heavy ion beams, beam diagnostic systems for beam tuning and for machine protection system (MPS), secondary collimators for charge selection of multi charge state ion beams, beam loading and stability of LLRF control, proper degauss process with superconducting (SC) solenoids when combined with SC dipole correctors, vacuum system, cryogenic and distribution system, helium pressure drop and stability of the cryomodules. 		 
slides icon Slides WEOBB102 [3.557 MB]  
 
WEIB202 Industrialization of the ILC Project linac, cavity, linear-collider, collider 2105
 
  • M.C. Ross
    SLAC, Menlo Park, California, USA
  
  Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515.
The International Linear Collider Global Design Effort (GDE) team completed the Technical Design Report (TDR) in early 2013. The TDR consists of a description of the machine design, a summary of the R&D program carried out in support of the design, a cost estimate and a project plan. The number of high technology components to be fabricated for ILC is large, similar to that built for the Large Hadron Collider*, and industrial partners have had an important role throughout the technical development and design period. It is recognized that transfer of new technology to industrial partners and subsequent collaborative development can be difficult**. To counter this, the ILC Technical Design Phase (TDP) team arranged a series of vendor visits, component development contracts, workshop satellite meetings and industrial production study contracts. The GDE collaboration provided the framework for development through an agreed-upon performance parameter set and project implementation scheme. The latter includes a ‘plug-compatibility’ policy that promotes innovation as long as specified interface conditions are met. In this paper we show the evolution of the technology from the labs where it was developed to the companies where high performance cavities are now routinely produced.
* The longest journey: the LHC dipoles arrive on time.
http://cerncourier.com/cws/article/cern/29723
** Office of High Energy Physics Accelerator R&D Task Force Report
http://www.acceleratorsamerica.org/report/acceleratortaskforcereport.pdf 		 
slides icon Slides WEIB202 [5.181 MB]  
 
WEPWA011 Injector Linac for the MESA Facility linac, booster, electron, target 2150
 
  • R.G. Heine, K. Aulenbacher
    IKP, Mainz, Germany
  
  Funding: Work supported by the German Federal Ministery of Education and Research (BMBF) and German Research Foundation (DFG) under the Cluster of Excellence "PRISMA"
In this paper we present several possible configurations of an injector linac for the upcoming Mainz Energy-recovering Superconducting Accelerator (MESA)* and discuss their suitability for the project.
*R. Heine, K. Aulenbacher, R. Eichhorn "MESA - Sketch of An Energy Recovery Linac For Nuclear Physics Experiments At Mainz" IPAC 12, New Orleans, USA, 2012, p.1993, TUPR073
 		 
 
WEPWO002 RF Measurements of the 1.6 Cell Lead/Niobium Photoinjector in HoBiCaT cavity, gun, cathode, vacuum 2313
 
  • A. Burrill, W. Anders, T. Kamps, J. Knobloch, O. Kugeler, P. Lauinger, A. Neumann
    HZB, Berlin, Germany
  • P. Kneisel
    JLAB, Newport News, Virginia, USA
  • R. Nietubyć
    NCBJ, Świerk/Otwock, Poland
  • J.K. Sekutowicz
    DESY, Hamburg, Germany
  
  The development of a simple and robust SRF photoinjector capable of delivering up to 1 mA average current in c.w. operation continues to progress with the horizontal RF testing of the 1.6 cell Pb/Nb hybrid photoinjector. This injector utilizes a sputtered lead coating on a removable Nb cathode plug as the photoelectron source and has recently been tested in the horizontal test cryostat facility, HoBiCaT, at HZB. In this paper we will report on the status of these RF measurements and compare the performance to previous vertical RF tests performed at JLab. We will also report on the experience operating this cavity with a TTF-III high power RF input coupler, as well as provide a summary of the microphonics susceptibility now that it has been installed into a helium vessel and equipped with a Saclay style tuner.  
 
WEPWO009 Numerical Coupling Analyses of BERLinPro SRF Gun cavity, gun, simulation, cathode 2328
 
  • E.N. Zaplatin
    FZJ, Jülich, Germany
  • W. Anders, A. Burrill, T. Kamps, J. Knobloch, O. Kugeler, A. Neumann
    HZB, Berlin, Germany
  
  BERLinPro is an approved ERL project to demonstrate energy recovery at 100 mA beam current by pertaining a high quality beam. These goals place stringent requirements on the SRF cavity (1300 MHz, β=1) for the photoinjector which has to deliver a small emittance 100 mA beam with at least 1.8 MeV kinetic energy while limited by fundamental power coupler performance to about 230 kW forward power. The RF and beam dynamics gun cavity features 1.4 λ/2 cell resonator. We present results of mechanical structure developments of SRF gun. The main purpose of the whole structure optimization was the design of the gun helium vessel together with the tuner and stiffening rings to provide the simple construction for structure tuning with minimization of the cavity frequency dependence on external pressure. During the resonator tuning and external load structure deformations the cavity field profile variation along the beam path should stay within 5%.  
 
WEPWO010 BERLinPro Seven-cell SRF Cavity Optimization and HOMs External Quality Factors Estimation cavity, HOM, factory, 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 		 
 
WEPWO017 Efforts on Nondestructive Inspections for SC Cavities cavity, target, laser, cryogenics 2352
 
  • Y. Iwashita, Y. Fuwa, M. Hashida, S. Sakabe, S. Tokita, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
  • H. Hayano, K. Watanabe, Y. Yamamoto
    KEK, Ibaraki, Japan
  • K. Otani
    INRS-EMT, Varennes (Québec), Canada
  
  The high resolution camera, so-called Kyoto Camera, inspecting the Sc cavity inner surface showed the importance of nondestructive inspections to improve yield in production of high performance SC Cavities. Further efforts have been continued for the inspection and the high resolution T-map, X-map and eddy current scanner have been developed. A radiography to detect small voids inside the Nb EBW seam with the target resolution of 0.1 mm is under investigation. We have carried out radiography tests with X-rays induced from an ultra short pulse intense laser.  
 
WEPWO018 Status of the IHEP 1.3 GHz Superconducting RF Program for the ILC cavity, cryomodule, vacuum, HOM 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.  
 
WEPWO019 Development of Frequency Measurement Setup for ADS 650MHz and 1.3GHz Superconducting RF Cavities at IHEP cavity, linac, simulation, controls 2358
 
  • S. Jin, J. Gao, Y. Liu, Z.C. Liu, J.Y. Zhai, T.X. Zhao, H.J. Zheng
    IHEP, Beijing, People's Republic of China
  
  The Accelerator Driven Sub-critical System (ADS) is under development in China, and the 650MHz β=0.82 superconducting RF cavity (SRF) has been chosen as a possible candidate to accelerate the proton bunches in the medium energy section from 360MeV to 1.5GeV [1]. In order to obtain quality management and quality assurance during fabrication, radio frequency measurements on parts and subassemblies of SRF cavities become a proper method [2]. In this paper, study on developing a new frequency measurement setup mainly for half cells, dumb-bells and end groups of ADS650MHz cavities at IHEP was reported. A digital pressure sense was assembled in the setup. Together with the simulation on the structural and frequency by ANSYS Workbench, a quantitative standard for the frequency measurement was built for the cavity fabrication. Since a 9-cell TESLA-Like cavity is also under study in the meantime, via a slight modification, the setup can be also used for it.  
 
WEPWO028 10×10mm2 MgB2 Film Fabricated by HPCVD as a Candidate Material for SRF Cavit cavity, superconductivity, radio-frequency, heavy-ion 2375
 
  • F. He, K.X. Liu, Z. Ni, D. Xie
    PKU, Beijing, People's Republic of China
  • Q. Feng
    Peking University, Beijing, People's Republic of China
  
  Magnesium diboride (MgB2) is one of candidate material for superconducting radio frequency cavities because of its good features: high transition temperature of ~39K and absence of weak links between grains which prevents other high-Tc superconducting materials, such as YBCO. Previous study of MgB2 are mainly focused on the films’ superconducting properties which are fabricated on Al2O3, SiC or some metal substrates with small scale less than 10×10 mm2. In this work we explore a technique to deposit clean and large-scale MgB2 films on Mo substrate, which is expected to provide a probable way to fabricate MgB2 thin-film cavities.. The measurement results show that its superconducting properties and mechanical behaviors are as good as those fabricated on small-scale metal substrates.  
 
WEPWO029 Design of a SRF Quarter Wave Electron Gun at Peking University cavity, electron, gun, simulation 2378
 
  • P.L. Fan, K.X. Liu, S.W. Quan, F. Zhu
    PKU, Beijing, People's Republic of China
  
  Funding: Work supported by National Basic Research Project (No. 2011CB808302) and National Natural Science Funds (No. 11075007)
Superconducting RF electron guns hold out the promise of very bright beams for use in electron injectors, particularly in future high average power free-electron lasers (FELs) and energy recovery linacs (ERLs). Peking University is designing a new SRF gun which is composed of a quarter wave resonator (QWR) and an elliptical cavity. Comparing to the elliptical cavity, the QWR is sufficiently compact at the same frequency and its electric field is quasi-DC. We have finished the preliminary design of the QWR cavity. The simulation shows that multipacting is not a critical issue for our cavity structure. Beam dynamic simulation of the QWR cavity is also presented.
contact author : zhufeng7726@pku.edu.cn 		 
 
WEPWO041 Beam Commissioning Superconducting RF Cavities for PLS-II Upgrade cavity, vacuum, storage-ring, LLRF 2390
 
  • Y.U. Sohn, M.-H. Chun, J.Y. Huang, Y.D. Joo, S.H. Nam, C.D. Park, H.J. Park, I.S. Park, I.H. Yu
    PAL, Pohang, Kyungbuk, Republic of Korea
  
  Two superconducting RF cavities were commissioned with electron beam at PLS-II, which is upgraded machine from PLS with 3 GeV, 20 insertion devices, and now on user service. These srf cavities have been prepared during last 3 years. Each cavity was tested with higher than 2 MV rf voltage and 125 kW standing wave power at CW mode after installation at storage ring. PLS-II is on user operation with 200 mA beam current now, and on the way of beam current improvement upto 400mA, by synchrotron conditioning for beam chamber and in-vacuum udulators. Upto 200 mA beam current no beam instability from the higher order modes is observed. With top-up mode operation, the errors of amplitude of rf field and phase are recorded as 0.3% and 0.3 degree peak to peak, respectively during one day. Successful PLS-II upgrade with hardware and its designed performance will be declared at the end of 1st half user run in 2013.  
 
WEPWO043 IFMIF-EVEDA SRF Linac Couplers Test Bench vacuum, linac, controls, LLRF 2396
 
  • D. Regidor, I. Kirpitchev, J. Molla, P. Méndez, A. Salom, M. Weber
    CIEMAT, Madrid, Spain
  • M. Desmons, N. Grouas, P. Hardy, V.M. Hennion, H. Jenhani, F. Orsini
    CEA/IRFU, Gif-sur-Yvette, France
  
  The IFMIF-EVEDA SRF Linac is a cryomodule equipped with eight superconducting HWR cavities, operating at the frequency of 175 MHz and powered by 200kW CW RF couplers. Before assembling the couplers to the cryomodule, it is necessary to process them using high levels of RF power. In order to perform this conditioning, the power couplers must be connected to a RF network which is fed by an RF source and ended with a load or a short-circuit, depending on the conditioning mode to be applied. A test bench has been designed for the conditioning of the SRF LINAC couplers. The main component is the “test box”, a resonant cavity where two couplers will be assembled to transmit the 200 kW from the RF source to the appropriate termination. The test box includes a large pumping port allowing an efficient pumping of the entire vacuum volume limited by the coupler ceramic windows. Several diagnostics as light detectors, vacuum gauges and thermal transducers will provide information on the relevant parameters for the control of the RF conditioning process. In addition, a support frame has been designed to maintain the whole assembly and reduce the mechanical stress on the couplers.  
 
WEPWO049 A Proposal for an ERL Test Facility at CERN cavity, linac, electron, HOM 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, HOM 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. 		 
 
WEPWO054 Multistep Mechanical Analyses of Centrifugal Barrel Polishing Barrel and Cavity cavity, simulation, acceleration, niobium 2426
 
  • M. Chen, C.A. Cooper, L. Ristori
    Fermilab, Batavia, USA
  
  Funding: US Department of Energy
Fermilab has successfully demonstrated the ability to improve the performance of damaged 1.3 GHz single cell and 9-cell Tesla–type cavities by using a modified centrifugal barrel polishing (CBP) process that leaves a mirror finish on the inside of the cavity. Fermilab now is developing and constructing a new CBP machine which can handle both 650 MHz and 1.3 GHz cavities. The new machine will have a larger moment arm and therefore impart more force on the cavity and machine. Because of these increased forces the effects on cavity supports and machine design were examined. This paper will document the multistep mechanical analyses for the CBP barrel and cavity, calculations of the fatigue life and the requirements for the structural welds. 		 
 
WEPWO058 Recent Progress at Fermilab Controlling Lorentz Force Detuning and Microphonics in Superconducting Cavities cavity, resonance, controls, cryomodule 2438
 
  • W. Schappert, Y.M. Pischalnikov
    Fermilab, Batavia, USA
  
  Funding: Work is supported by U.S. Department of Energy
SRF cavities are susceptible to detuning by mechanical deformations induced by the Lorentz force and microphonics. Providing the RF overhead required to maintain the accelerating gradient in detuned cavities can increase both the capital and operating costs of superconducting accelerators. Recent work at Fermilab has shown that active vibration control using a piezo actuator can reduce both Lorentz Force detuning and microphonics to the point where negligible RF overhead is required to maintain the accelerating gradient. 		 
 
WEPWO065 Optimization of Elliptical SRF Cavities for β <1 cavity, HOM, 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. 		 
 
WEPWO071 Quench and High Field Q-SLOP Studies using a Single Cell Cavity with Artificial Pits cavity, niobium, feedback, factory 2465
 
  • Y. Xie, G.H. Hoffstaetter, M. Liepe
    CLASSE, Ithaca, New York, USA
  
  Surface defects such as pits have been identified as some of the main sources of limitations of srf cavity performance. A single cell cavity was made with 30 artificial pits in the high magnetic field region to gain new insight in how pits limit the cavity performance. The test of the pit cavity showed clear evidence that the edges of two of the largest radius pits transitioned into the normal conducting state at field just below the quench field of the cavity, and that the quench was indeed induced by these two pits. Insights about quench and non-linear rf resistances will be presented.  
 
WEPWO073 RF Design Optimization for New Injector Cryounit at CEBAF cavity, coupling, cryomodule, injection 2471
 
  • H. Wang, G. Cheng, F.E. Hannon, A.S. Hofler, R. Kazimi, J.P. Preble, R.A. Rimmer
    JLAB, Newport News, Virginia, USA
  
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
A new injector superconducting RF (SRF) cryounit with one new 2-cell, β=0.6 cavity plus one refurbished 7-cell, β=0.97, C100 style cavity has been re-designed and optimized for the engineering compatibility of existing module for CEBAF operation. The optimization of 2-cell cavity shape for longitudinal beam dynamic of acceleration from 200keV to 533keV and the minimization of transverse kick due to the waveguide couplers to less than 1 mrad have been considered. Operating at 1497MHz, two cavities has been designed into a same footprint of CEBAF original quarter cryomodule to deliver an injection beam energy of 5MeV in less than 0.27o rms bench length and a maximum energy spread of 5keV.

 
 
WEPWO076 Development of Ultra High Gradient and High Q0 Superconducting Radio Frequency Cavities cavity, niobium, acceleration, cryogenics 2474
 
  • R.L. Geng, W.A. Clemens, J. Follkie, T. Harris, D. Machie, R. Martin, A.D. Palczewski, E. Perry, G. Slack, R.S. Williams
    JLAB, Newport News, Virginia, USA
  • C. Adolphsen, Z. Li
    SLAC, Menlo Park, California, USA
  • J.K. Hao, Y.M. Li, K.X. Liu
    PKU, Beijing, People's Republic of China
  • P. Kushnick
    JLab, Newport News, Virginia, USA
  
  Funding: Work supported by DOE. Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
We report on the recent progress at Jefferson Lab in developing ultra high gradient and high Q0 superconducting radio frequency (SRF) cavities for future SRF based machines. A new 1300 MHz 9-cell prototype cavity is being fabricated. This cavity has an optimized shape in terms of the ratio of the peak surface field (both magnetic and electric) to the acceleration gradient, hence the name low surface field (LSF) shape. The goal of the effort is to demonstrate an acceleration gradient of 50 MV/m with Q0 of 1010 at 2 K in a 9-cell SRF cavity. Fine-grain niobium material is used. Conventional forming, machining and electron beam welding method are used for cavity fabrication. New techniques are adopted to ensure repeatable, accurate and inexpensive fabrication of components and the full assembly. The completed cavity is to be first mechanically polished to a mirror-finish, a newly acquired in-house capability at JLab, followed by the proven ILC-style processing recipe established already at JLab. In parallel, new single-cell cavities made from large-grain niobium material are made to further advance the cavity treatment and processing procedures, aiming for the demonstration of an acceleration gradient of 50 MV/m with Q0 of 2·1010 at 2K.
The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes. 		 
 
WEPWO077 Rf System Requirements for JLab’s MEIC Collider Ring ion, cavity, electron, impedance 2477
 
  • S. Wang, R. Li, R.A. Rimmer, H. Wang, Y. Zhang
    JLAB, Newport News, Virginia, USA
  
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The Medium-energy Electron Ion Collider (MEIC), proposed by Jefferson Lab, consists of a series of accelerators [1]. At the top energy are the electron and ion collider rings. For the ion ring, it accelerates five long ion bunches to colliding energy and rebunches ions into a train of very short bunches before colliding. A set of low frequency RF system is needed for the long ion bunch energy ramping. Another set of high frequency RF cavities is needed to rebunch ions. For the electron ring, superconducting RF (SRF) cavities are needed to compensate the synchrotron radiation energy loss. The impedance of the SRF cavities must be low enough to keep the high current electron beam stable. The preliminary design requirements of these RF cavities are presented.
The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes. 		 
 
WEPWO085 Commissioning SRF Gun for the R&D ERL at BNL gun, cavity, HOM, 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. 		 
 
WEPWO087 Parameter Optimization for Laser Polishing of Niobium for SRF Applications laser, niobium, cavity, target 2498
 
  • L. Zhao, M.J. Kelley
    The College of William and Mary, Williamsburg, USA
  • M.J. Kelley, J.M. Klopf, C.E. Reece
    JLAB, Newport News, Virginia, USA
  
  Surface smoothness is critical to the performance of SRF cavities. As laser technology has been widely applied to metal machining and surface treatment, we are encouraged to use it on niobium as an alternative to the traditional wet polishing process where aggressive chemicals are involved. In this study, we describe progress toward smoothing by optimizing laser parameters on BCP treated niobium surfaces. Results show that microsmoothing of the surface without ablation is achievable.  
poster icon Poster WEPWO087 [1.683 MB]  
 
WEPFI076 Experience with a 5 kW, 1.3 GHz Solid State Amplifier linac, status, cryomodule, factory 2869
 
  • K.M.V. Ho, R. Eichhorn, D.L. Hartill, M. Liepe
    CLASSE, Ithaca, New York, USA
  
  This study describes the experience with and performance of a commercially available 1.3 GHz 5kW Solid State Amplifier in various experiments at Cornell University. This paper focuses on several key factors in testing the performance of the amplifier. Among those are phase and amplitude stability, gain linearity, and phase shift vs. power. High power amplifiers are usually built with multiple RF power modules and the individual output signals are then combined in a power combiner. Therefore, the phases of the individual RF output power signals have to be adjusted within tight tolerances. The relative phases can be affected by different lengths cables and also affect the overall gain performance of the amplifier.  
 
WEPME007 Commissioning of the Upgraded Superconducting CW Linac ELBE cavity, klystron, vacuum, linac 2935
 
  • H. Büttig, A. Arnold, A. Büchner, M. Justus, M. Kuntzsch, U. Lehnert, P. Michel, R. Schurig, G.S. Staats, J. Teichert
    HZDR, Dresden, Germany
  
  With the expansion of the radiation source ELBE a center for high power radiation sources is being built at the Helmholtz Zentrum Dresden-Rossendorf (HZDR). In a first step (January 2012) the available CW RF-power (1.3 GHz) per superconducting 9-cell TESLA cavity at ELBE had been increased from 8.5 kW to 20 kW (CW) using solid state amplifiers. In a second step the performance of several machine components of ELBE must be redesigned to enable full power operation without risks. The poster gives an overview how these problems have been solved at ELBE and reports on the commissioning.  
 
WEPME052 LLRF Characterisation of the Daresbury International Cryomodule LLRF, cavity, cryomodule, resonance 3046
 
  • L. Ma
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • P.A. Corlett, A.J. Moss
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  The 2-cavity Superconducting RF (SRF) Linac cryomodule of the Accelerators and Lasers in Combined Experiments (ALICE) located at Daresbury Laboratory will be replaced by a new International ERL Cryomodule in early 2013. The improved 7-cell, 1.3 GHz SRF cavities will be characterised and compared with the original 9-cell cavities. Tests will be performed by driving the cavities by a VCO-PLL loop so that Q measurements, microphonics sensitivity and Lorentz force detuning can be analysed. A digital LLRF system using the LLRF4 board developed by Larry Doolittle has been developed at Daresbury Laboratory and will be installed on the upgraded cryomodule. This system is capable of controlled cavity filling to reduce waveguide reflection voltage, feedback/feed forward control and adaptive beam loading compensation. The new cryomodule will be evaluated with both the analog LLRF system and the digital LLRF system to allow for performance comparison. Cavity operation with high QL will also be tested to discover the feedback control limit as a function of inherent microphonics. This paper sets out to discuss the qualification process, testing and results of the upgraded cryomodule installation.  
 
THYB201 Where Next with SRF? linac, cavity, cryomodule, proton 3124
 
  • G. Ciovati
    JLAB, Newport News, Virginia, USA
  
  Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
RF superconductivity (SRF) has become, over the last ~20 years, the technology of choice to produce RF cavities for particle accelerators. This occurred because of improvements in material and processing techniques as well as the understanding and remediation of practical limitations in SRF cavities. This development effort span ~40 years and Nb has been the material of choice for SRF cavity production. As the performances of SRF Nb cavities are approaching what are considered to be theoretical limits of the material, it is legitimate to ask what will be the future of SRF. In this article we will attempt to answer such question on the basis of near-future demands for SRF-based accelerators and the basic SRF properties of the available materials. Clearly, Nb will continue to play a major role in SRF cavities in the coming years but the use of superconductors with higher critical temperature than Nb is also likely to occur. 		 
slides icon Slides THYB201 [1.549 MB]  
 
THOBB201 Pathway to a Post Processing Increase in Q0 of SRF Cavities cavity, shielding, niobium, cryogenics 3129
 
  • O. Kugeler, J. Knobloch, J.M. Vogt
    HZB, Berlin, Germany
  • S. Aull
    CERN, Geneva, Switzerland
  
  A significant improvement of Q0 to values larger than 3.2x1010 at 1.8K has been repeatedly achieved in an SRF cavity by thermal cycling, i.e. heating the cavity briefly above transition temperature and subsequent cooling. Conceivable explanations for this effect reach from effectivity deviations of the magnetic shielding to thermal currents to hydrogen diffusion. Experimental We have experimentally verified some of these explanations, leaving a direct impact of cooling dynamics on frozen flux as the most plausible one. The pathway to this finding is being presented and the application to SRF systems is elicited.  
slides icon Slides THOBB201 [1.184 MB]  
 
THPEA053 Data Acquisition and Monitoring for TPS SRF Module Horizontal Test EPICS, monitoring, controls, cavity 3264
 
  • Y.-H. Lin, L.-H. Chang, M.H. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, Z.L. Liu, C.H. Lo, M.H. Tsai, Ch. Wang, M.-S. Yeh, T.-C. Yu
    NSRRC, Hsinchu, Taiwan
  • M.H. Tsai
    NTUT, Taiwan
  
  Three KEKB-type single-cell SRF modules were shipped to NSRRC before the end of 2012. The horizontal test of the first KEKB-type SRF module has been already finished in January of 2013. While the horizontal tests for the next two SRF module will be completed in May and August of this year. This article introduces the data acquisition and monitoring systems during the SRF horizontal test in NSRRC.  
 
THPFI004 Progress on the SRF Linac Developments for the IFMIF-LIPAC Project cryomodule, solenoid, linac, vacuum 3294
 
  • F. Orsini
    CEA/DSM/IRFU, France
  • P. Abramian, J. Calero, J.C. Calvo, J.L. Gutiérrez, T. Martínez de Alvaro, J. Munilla, I. Podadera, F. Toral
    CIEMAT, Madrid, Spain
  • N. Bazin, P. Brédy, P. Carbonnier, G. Devanz, G. Disset, N. Grouas, P. Hardy, V.M. Hennion, H. Jenhani, J. Migne, A. Mohamed, J. Neyret, J. Relland, B. Renard, D. Roudier
    CEA/IRFU, Gif-sur-Yvette, France
  
  In the framework of the International Fusion Materials Irradiation Facility (IFMIF), which consists of two high power accelerator drivers, each delivering a 125 mA deuteron beam at 40 MeV in CW, an accelerator prototype is presently under design and realization for the first phase of the project. This accelerator includes a SRF Linac, which is designed for the transportation and focalization of the deuteron beam up to 9 MeV. This SRF Linac is a large cryomodule of ~6 m long, working at 4.4 K and at the frequency of 175 MHz in continuous wave. It is mainly composed of 8 low-beta HWRs, 8 Solenoid Packages and 8 RF Power Couplers. This paper focuses on the recent developments and changes made on the SRF Linac design: following the abandon of the HWR frequency tuning system, initially based on a plunger located inside the central region of the resonator, a new external tuning system has been designed, implying a complete redesign of the resonator and consequently impacting the cryomodule lattice. The recent changes in the design are presented in this paper. In addition, cold tests were performed on a HWR prototype and cold tests results of the magnets prototypes are also presented.  
 
THPME002 Compact High-Tc 2G Superconducting Solenoid for Superconducting RF Electron Gun solenoid, cavity, gun, electron 3514
 
  • G. Nielsen, A. Baurichter, N. Hauge, E.K. Krauthammer
    Danfysik A/S, Taastrup, Denmark
  
  A solenoid with second generation (2G) high-temperature superconducting (HTS) coils for use in the superconducting RF electron gun of the WiFEL free electron laser at the University of Wisconsin, Madison, has successfully been designed, manufactured, tested and magnetically characterized at Danfysik. The solenoid is designed to operate in the temperature range between 5 K and 70 K. A stack of 16 serially connected pancake coils wound from SuperPower 2G HTS-tape is mounted inside a cylindrical iron yoke with end caps. The solenoid was designed with an excitation current margin of at least 130 % of the nominal operation current in the whole temperature range. At operation, 17.2 kA-turns yield a center field of 0.20 T and a field integral of 3.1 T2 mm, with very small integrated field errors. With a yoke outer diameter of 176 mm and a total length of 136 mm, the solenoid is very compact, and can therefore be placed very close to the RF cavity, improving its emittance compensating efficiency. Careful magnetic design minimizes the leak field at the SC cavity surface. Heat dissipation is negligible hence conduction cooling through copper braids attached to the iron yoke is sufficient.  
 
THPME010 Magnetic Shielding for the 1.3 GHz Cryomodule at IHEP shielding, simulation, cavity, cryomodule 3528
 
  • S. Jin, Y. Chen, J. Gao, R. Ge, Y. Liu, Z.C. Liu, J.Y. Zhai, T.X. Zhao, H.J. Zheng
    IHEP, Beijing, People's Republic of China
  • F. Yang
    China Iron and Steel Research Institute Group, Beijing, People's Republic of China
  
  An ILC-type Superconducting RF (SRF) accelerating unit is being studied at IHEP. In order to achieve the design performance including both accelerating gradient and quality factor, the SRF cavity must be cooled with ambient magnetic field well shielded to the level of several mG[1,2]. In this paper, permeability of several kinds of materials for magnetic shielding made in China is systematically studied in cooperation with China Iron & Steel Research Institute Group (CISRI) and reported for the first time. By using proper material, numerical calculation for the magnetic shielding design was done via the program of Opera-3D, and then magnetic shield was fabricated by CISRI. This paper will show those studies above and the final magnetic shielding effect at room temperature. Comparisons between simulation result and real effect will also be discussed in the paper, as well as the preliminary analysis for the magnetic field leaking of this design.  
 
THPME035 The Electronic System Design and Realization for First Set 500 MHz KEKB SRF Module High Power Test controls, cavity, cryogenics, HOM 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.  
 
THPME040 The Installation and Commissioning of the Helium Cryogenic System for theTPS Project cryogenics, storage-ring, electron, controls 3600
 
  • H.H. Tsai, S.-H. Chang, W.-S. Chiou, F. Z. Hsiao, C.K. Kuan, H.C. Li, T.F. Lin, C.P. Liu
    NSRRC, Hsinchu, Taiwan
  
  The construction of an electron accelerator with energy 3 GeV is under way for high brilliance and flux X-ray photon source at NSRRC. There will be eventually four superconducting radio frequency (SRF) cavities installed to maintain the electron energy. The helium cryogenic system has been designed and fabricated to provide the required liquid helium for SRF cavities. The cryogenic system consists of the 700-W refrigerator, the 315-kW variant frequency compressor, the oil removal system, the recovery compressor system, the gas helium buffer tanks, and one 7000-L liquid helium Dewar. The overall system installation and commissioning will be presented and discussed in this paper.