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SRF

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MO103 SNS Superconducting Linac Operational Experience and Upgrade Path cavity, cryomodule, linac, HOM 11
 
  • S.-H. Kim
    ORNL, Oak Ridge, Tennessee
 
 

Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy
The SNS Superconducting Linac (SCL) has been providing the main acceleration in two different accelerating sections with 33 medium beta and 48 high beta superconducting radio-frequency (SRF) 6-cell cavities. The use of superconducting elliptical cavities for particles whose velocity are less than the speed of light, make this accelerator a very important milestone for learning operating conditions of this cavity type. Since the SNS SCL is the first large-scale high energy pulsed-superconducting proton linac that provides high beam power utilizing H- beams, many aspects of its performance were unknown and unpredictable. A large amount of data has been collected on the pulsed behavior of cavities and cryomodules at various repetition rates and at various temperatures. This experience will be of great value in determining future optimizations of SNS as well in guiding in the design and operation of future pulsed superconducting linacs. This paper describes the details of the rf properties, performances, path-forward for the SNS power ramp-up goal, and upgrade path of the SNS superconducting linac.

 

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TUP006 Improving the Superconducting Cavities and Operational Findings at the S-DALINAC cavity, niobium, vacuum, superconducting-cavity 395
 
  • R. Eichhorn, A. Araz, M. Brunken, J. Conrad, H.-D. Gräf, M. Hertling, F. Hug, C. Klose, M. Konrad, T. Kuerzeder, C. Liebig, M. Platz, A. Richter, S.T. Sievers, T. Weilbach
    TU Darmstadt, Darmstadt
 
 

Funding: Work supported by the DFG through SFB 634
After 15 years operating the S-DALINAC the design quality factor for the superconducting cavities has still not been reached. Currently, the cavities are heat treated at 850 C in an UHV furnace installed in Darmstadt three years ago. We will report about the furnace, the heat treatment procedure and the results of subsequent surface resistance measurements. Prior to the heat treatment the field flatness of some of the 20 cell elliptical cavities has been measured, leading to unexpected operational findings to be reported: operating and frequency-tuning the cavity for several years led to heavy distortions of the field flatness. This might be an indication that the frequency tuning of the cavity done by compressing the cavity longitudinally, does not act uniformly on each cell even though the cavity is only supported at the end cells. The paper will close with a status report on machine operation and modifications undertaken during the last two years.

 
TUP028 Status of High Current R&D Energy Recovery Linac at Brookhaven National Laboratory electron, cavity, emittance, gun 453
 
  • A. Kayran, D. Beavis, I. Ben-Zvi, M. Blaskiewicz, J.M. Brennan, A. Burrill, R. Calaga, P. Cameron, X. Chang, K.A. Drees, G. Ganetis, D.M. Gassner, J.G. Grimes, H. Hahn, L.R. Hammons, A. Hershcovitch, H.-C. Hseuh, A.K. Jain, R.F. Lambiase, D.L. Lederle, V. Litvinenko, G.J. Mahler, G.T. McIntyre, W. Meng, T.C. Nehring, B. Oerter, C. Pai, D. Pate, D. Phillips, E. Pozdeyev, T. Rao, J. Reich, T. Roser, T. Russo, Z. Segalov, A.K. Sharma, J. Smedley, K. Smith, T. Srinivasan-Rao, J.E. Tuozzolo, G. Wang, D. Weiss, N. Williams, Q. Wu, K. Yip, A. Zaltsman
    BNL, Upton, Long Island, New York
  • H. Bluem, M.D. Cole, A.J. Favale, D. Holmes, J. Rathke, T. Schultheiss, A.M.M. Todd
    AES, Medford, NY
  • J.R. Delayen, L.W. Funk, H.L. Phillips, J.P. Preble
    JLAB, Newport News, Virginia
 
 

Funding: Work performed under contract No. DE-AC02-98CH10886 with the auspices of the DoE of United States.
An ampere class 20 MeV superconducting Energy Recovery Linac (ERL) is under construction at Brookhaven National Laboratory (BNL) for testing concepts for high-energy electron cooling and electron-ion colliders. One of the goals is to demonstrate an electron beam with high charge per bunch (~5 nC) and extremely low normalized emittance (~5 mm-mrad) at an energy of 20 MeV. Flexible lattice of ERL loop provides a test-bed for testing issues of transverse and longitudinal instabilities and diagnostics of intense cw e-beam. The superconducting 703 MHz rf photoinjector is considered as an electron source for such a facility. At first we develop the straight pass (gun – 5 cell cavity – beam stop) test for the SRF Gun performance studies. Then the novel injection line concept of emittance preservation at the lower energy will be tested at this ERL. In this paper we present the status and our plans for construction and commissioning of this facility.

 
TUP041 Superconducting Options for the UK's New Light Source Project cryomodule, FEL, linac, cavity 486
 
  • P.A. McIntosh, R. Bate, C.D. Beard, D.M. Dykes, S.M. Pattalwar
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
 
 

The UK's new light source project was officially launched on April 11th 2007, which will be based on advanced conventional and free electron lasers, with unique and world leading capabilities. User consulation exercises have already been initiated to determine the fundamental photon output requirements for such a machine. In order to match a nominal requirement for high repetition rates (extending up to 1 MHz), a series of superconducting rf (SRF) linac options have been investigated, reflecting varied beam loading conditions and subsequent high and low power rf solutions.

 
TUP042 High Repetition Rate Electron Injectors for FEL Based Next Generation Light Sources gun, emittance, cavity, simulation 489
 
  • B.L. Militsyn, C.D. Beard, J.W. McKenzie
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
 
 

Several laboratories concentrate their efforts on development of high repetition rate FEL based next generation light sources. One particular concept under development at STFC Daresbury Laboratory specifies high brightness electron bunches with a charge of 0.2-1 nC which arrive with a frequency up to 1 MHz. As emittance of the bunches should not exceed 1 um, traditional high repetition rate thermionic injectors, similar to the ones used at high micropulse repetition rate FELs like ELBE or FELIX, may not be used. We consider three options of high repetition rate injectors based on photocathode guns - a high voltage dc gun, a one and half cell superconducting rf gun and a normal conducting VHF gun, recently proposed at LBNL. We consider practical injector schemes for all three guns and provide the results of beam dynamic simulations. We also discuss the photocathodes which may be used in each gun, as this critical component defines achievable beam parameters and operational efficiency of the injectors.

 
WE201 RF Systems for CW SRF Linacs linac 709
 
  • S.A. Belomestnykh
    CLASSE, Ithaca, New York
 
 

The talk will provide an overview of the latest developments in rf systems for cw operated SRF linacs, such as CEBAF (in particular, 12 GeV Upgrade), Cornell ERL injector, ELBE, and ERLP at Daresbury.

 

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TH101 Superconducting RF R&D Toward High Gradient cavity, niobium, HOM, superconducting-cavity 725
 
  • C.M. Ginsburg
    Fermilab, Batavia
 
 

High-beta superconducting rf elliptical cavities are being developed in large numbers for several accelerator projects including the International Linear Collider (ILC). In recent years, the understanding of cavity performance limitations has improved significantly, leading to better than 40 MV/m in some cavities. However, further improvement is needed to reach reliably the 31.5 MV/m operating gradient proposed for the ILC Main Linac cavities. World-wide R&D on the cavity gradient frontier includes improved surface cleaning and smoothing treatments, development of alternative cavity shapes and materials, and novel cavity manufacturing techniques. Substantial progress has been made with diagnostic instrumentation to understand cavity performance limitations. Some highlights of the efforts in superconducting rf R&D toward achieving higher gradients in high-beta elliptical cavities are reviewed.

 

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THP013 Various Applications of Dry-Ice Cleaning in the Field of Accelerator Components at DESY cavity, gun, cathode, superconductivity 803
 
  • A. Brinkmann, D. Reschke, J. Ziegler
    DESY, Hamburg
 
 

Funding: We acknowledge the support of the European Community Research Infrastructure Activity under FP6 'Structuring the European Research Area' program (CARE, contract number RII-CT-2003-506395
Dry-Ice cleaning offers a dry and waterless cleaning option removing hydrocarbons and particles without residues. Complex excavations like Cu rf gun cavities and Nb multicell cavities in horizontal installation position can be cleaned in an effective way. In the recent past rf gun cathodes and cathode transportboxes could be cleaned satisfactory. A status report will be given.

 
THP018 Successful Qualification of the Coaxial Blade Tuner cavity, simulation, insertion, superconducting-cavity 818
 
  • R. Paparella, A. Bosotti, C. Pagani, N. Panzeri
    INFN/LASA, Segrate (MI)
  • C. Albrecht, R. Lange, L. Lilje
    DESY, Hamburg
  • J. Knobloch, O. Kugeler, A. Neumann
    BESSY GmbH, Berlin
 
 

Cavity tuners are needed to precisely tune the narrow-band resonant frequency of superconducting cavities. The Blade Tuner presented is installed coaxially to the cavity and changes the resonator frequency by varying its length. Piezoceramic actuators add dynamic tuning capabilities, allowing fast compensation of main dynamic instabilities as Lorentz Forces, under pulsed operations, and microphonic noise. A prototype piezo Blade Tuner has been assembled on a TESLA cavity and extensively cold tested inside the horizontal cryostats CHECHIA (DESY) and HoBiCaT (BESSY). Then, as suggested by results, a few minor modifications have been implemented thus achieving the current Blade Tuner design. The introduction of thicker blades re-distributed along the circumference allows to increase its stiffness and fulfill European and American pressure vessel codes, while ensuring requested performances and cost. The paper will present the successful characterization tests performed on the prototype, the extensive mechanical analyses made to validate the final model and the results from qualification tests of first revised Blade Tuner produced, to be installed in the second module of ILCTA at FNAL.

 
THP029 Performance of 3.9-GHZ Superconducting Cavities cavity, HOM, superconductivity, status 848
 
  • E.R. Harms, H.T. Edwards, A. Hocker, T.N. Khabiboulline, N. Solyak
    Fermilab, Batavia
 
 

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
3.9 GHz SRF cavities have been built and tested at Fermilab for use in the DESY FLASH facility. Six cavities have undergone testing in various scenarios. Comparisons of performance in these different conditions, from bare cavities in a vertical dewar to 'dressed' in the horizontal test stand and intermediate test configurations are presented. We also report on analysis of expected maximum performance and an estimate of same.

 
THP039 SRF Cavity Imperfection Studies Using Advanced Shape Uncertainty Quantification Tools cavity, cryomodule, dipole, HOM 870
 
  • V. Akcelik, K. Ko, L. Lee, Z. Li, C.-K. Ng, L. Xiao
    SLAC, Menlo Park, California
 
 

Funding: Work supported by DOE contract DE-AC02-76SF00515.
The shape deviation of a SRF cavity from the design shape may result in significant impact on cavity performance and wakefields that could lead to unexpected effects in beam dynamics. Yet, most of these deviations are unknown in the final cavity installation because of the complicated process of assembly and tuning. It is desirable to be able to uncover such distortions using measurable rf quantities. With these data, the cavity performance can be analyzed and realistic tolerance criteria may be implemented in the cavity design and manufacture for quality assurance. To perform such analyses, SLAC has developed advanced Shape Determination Tools, under the SciDAC support for high performance computing, that recover the real cavity shape by solving an inverse problem. These tools have been successfully applied to analyze shape distortions to many SRF cavities, and identified the cause of unexpected cavity behaviors. The capabilities and applications of these tools will be presented.

 
THP042 High-Gradient SRF R&D for ILC at Jefferson Lab cavity, cathode, instrumentation, niobium 879
 
  • R.L. Geng, G. Ciovati, A.C. Crawford
    JLAB, Newport News, Virginia
  • M.S. Champion, D.A. Sergatskov
    Fermilab, Batavia
  • F. Furuta, K. Saito
    KEK, Ibaraki
 
 

Funding: Supported by DOE
Jefferson Lab plays an active role in the ILC high-gradient SRF R&D. Eight 9-cell cavities have been processed and tested so far by using the state-of-the-art recipes. Five reached a maximum gradient of over 32 MV/m. However, not surprisingly, the high-gradient performance is not necessarily reached during the first test. Re-processing by progressively more material removal can improve performance ultimately, but the number of re-processing cycles needed is un-predictable. Some cavities are quench limited repeatedly at around 20 MV/m. The quench locations are near the equator weld of specific cells. Based on the non-trivial high-gradient experiences in the past two years, we come to the conclusion that new capabilities beyond the state-of-the-art must be added to the existing SRF infrastructures in order to reliably achieve high gradients at a low cost. Targeted R&D is required to identify and characterize gradient limiting defects and field emitters. An enhanced high-gradient R&D program is emerging at JLab for continued contribution to realize the ambitious ILC gradient yield goal.

 

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