Accelerator Technology
Tech 07: Superconducting RF
Paper Title Page
TUP015 Conceptual Design of the Project-X 1.3 GHz, 3-8 GeV Pulsed Linac 841
 
  • N. Solyak, Y.I. Eidelman, S. Nagaitsev, J.-F. Ostiguy, A. Vostrikov, V.P. Yakovlev
    Fermilab, Batavia, USA
  
  The Project-X, a multi-MW proton source, is under development at Fermilab. It enables a Long Baseline Neutrino Experiment via a new beam line pointed to DUSEL in Lead, South Dakota, and a broad suite of rare decay experiments. The facility contains 3-GeV 1-mA CW superconducting linac. In the second stage of about 5% of the H− beam is accelerated up to 8 GeV in a 1.3 GHz SRF pulse linac to Recycler/Main Injector. In order to mitigate the problem with the stripping foil heating during injection to the Main Injector, the pulses with higher current are accelerated in CW linac together with 1 mA beam for further acceleration in the pulse linac. The optimal current in the pulse linac is discussed as well as limitations that determine it's selection. A concept design of the pulse linac is described. The lattice design is presented as well as RF stability analysis. The necessity of the HOM couplers is discussed also.  
 
TUP029 Low-Beta Superconducting RF Cavity Tune Options 865
 
  • E.N. Zaplatin
    FZJ, Jülich, Germany
  
  The main method of the superconducting RF cavity frequency tuning is a resonator wall deformation. Since the highest frequency sensitivity on the geometry change is an accelerating gap variation, the "standard" place of deformation tuning force application in different cavity types are the cavity beam ports. A series of low-beta cavities (QWR, HWR, spoke-type) with different options of tuning have been investigated. Every option is compared with beam port displacement. The problem of resonator frequency shift self-compensation caused by external pressure fluctuations is discussed.  
 
TUP031 Project X Elliptical Cavity Structural Analyses 868
 
  • E.N. Zaplatin
    FZJ, Jülich, Germany
  
  Project X is proposed at Fermi National Accelerator Laboratory high-intensity proton accelerator complex that could provide beam for a variety of physics projects. Superconducting resonators will be used for beam acceleration. Here we report a structural design of elliptical cavities with resonance frequency 650 MHz and β=0.91 and 0.61. Since there is a concern that the pressure in the helium plumbing will not be stable when the cryomodules are connected to the liquid helium supply and helium gas returns it is necessary to provide the cavity stiffening with requirements of 15 Hz amplitude frequency shift. The cavity RF and mechanical properties are investigated. The calculations of the cavity frequency shift with pressure for different schemes of cavity stiffening were provided. The criterion for the optimization was the minimization of a resonant frequency dependence on an external pressure. Based on the results of these simulations several options on cavity stiffening have been proposed. Additionally, the cavity stiffening structural scheme for self-compensation of resonator detuning caused by external pressure fluctuation have been investigated.  
 
TUP032 Development of 1.3 GHz Prototype Niobium Single Cell Superconducting Cavity Under IIFC Collaboration 871
 
  • A. Puntambekar, M. Bagre, J. Dwivedi, P.D. Gupta, R.K. Gupta, S.C. Joshi, G.V. Kane, R.S. Sandha, S.D. Sharma, P. Shrivastava
    RRCAT, Indore (M.P.), India
  • C.A. Cooper, M.H. Foley, T.N. Khabiboulline, C.S. Mishra, J.P. Ozelis, A.M. Rowe, G. Wu
    Fermilab, Batavia, USA
  • V. Jain
    IIT, Mumbai, India
  • D. Kanjilal, K.K. Mistri, P.N. Potukuchi, J. Sacharias
    IUAC, New Delhi, India
  • V.C. Sahni
    Homi Bhbha National Institute (HBNI), DAE, Mumbai, India
  
  Under Indian Institutions Fermilab collaboration (IIFC), Raja Ramanna Centre for Advanced Technology (RRCAT) Indore, Inter University Accelerator Centre (IUAC) New Delhi and Fermi National Accelerator Laboratory (FNAL) have developed two prototype 1.3 GHz niobium single cell superconducting cavities. Development of forming tools, forming of half cells, machining of components, development of welding fixtures along with RF & vacuum qualification were carried out at RRCAT. The electron beam welding was carried out at IUAC. The fabricated prototype cavities were tested for RF and vacuum leak tightness up to 77 K at RRCAT before shipment to FNAL. Processing, consisting of CBP, EP, and heat treatment was carried out jointly by FNAL and Argonne National Laboratory in USA. Both the prototype cavities were tested at 2 K in the VTS facility at FNAL and have achieved the accelerating gradient of ~ 19 to 21 MV/m with Q > 1.5 ·10+10. This paper will report the developmental efforts carried out in tooling, forming, machining, welding & various qualification procedures adopted. The paper will also present the processing and the 2 K test results.  
 
TUP033 Engineering Design of Vertical Test Stand Cryostat 874
 
  • S.K. Suhane, S. Das, P.D. Gupta, S.C. Joshi, P.K. Kush, S. Raghvendra, N.K. Sharma
    RRCAT, Indore (M.P.), India
  • R.H. Carcagno, C.M. Ginsburg, C.S. Mishra, J.P. Ozelis, R. Rabehl, C. Sylvester
    Fermilab, Batavia, USA
  • V.C. Sahni
    Homi Bhbha National Institute (HBNI), DAE, Mumbai, India
  
  Under Indian Institutions and Fermilab collaboration Raja Ramanna Centre for Advanced Technology and Fermi Lab are jointly developing 2K Vertical Test Stand (VTS) cryostats for testing SCRF cavities. The VTS cryostat has been designed for a large testing aperture of 34 inches for testing of 325 MHz Spoke resonators, 650 MHz and 1.3 GHz multi-cell SCRF cavities for Project-X at FNAL and for VTS facility at RRCAT. VTS cryostat comprises of liquid helium (LHe) vessel with internal magnetic shield, top insert plate equipped with cavity support stand and radiation shield, liquid nitrogen (LN2) shield and vacuum vessel with external magnetic shield. . The engineering design and analysis of VTS cryostat has been carried out using ASME B&PV code and FEA. Design of internal and external magnetic shields was performed to limit the magnetic field inside LHe vessel, at the cavity surface <10 mG. Thermal analysis for LN2 shield has been performed to check the effectiveness of LN2 cooling.  
 
TUP039 Low Latency Data Transmission in LLRF Systems 877
 
  • D.R. Makowski, G.W. Jabłoński, A. Napieralski, P. Predki
    TUL-DMCS, Łódź, Poland
  
  Funding: The research leading to these results has received funding from the Polish National Science Council Grant 642/N-TESLAXFEL/09/2010/0.
The linear accelerators applied to drive Free Electron Lasers (FELs), such as the X-Ray Free Electron Laser (XFEL), require sophisticated control systems. The Low Level Radio Frequency (LLRF) control systems of a linear accelerator should provide signal to vector modulator in less than 1 microsecond. Therefore the latency of communication interfaces is more important than their throughput. The paper discusses the application of serial gigabit links for transmission of data in LLRF systems. The latency of pure serial transmission based on Xilinx RocketIO transceivers was evaluated and compared with Xilinx Aurora protocol. The developed low latency protocol will be also presented. 		 
 
TUP041 Quench Dynamics in SRF Cavities: Can We Locate the Quench Origin with 2nd Sound? 883
 
  • Y.B. Maximenko
    MIPT, Dolgoprudniy, Moscow Region, Russia
  • D.A. Sergatskov
    Fermilab, Batavia, USA
  
  A newly developed method of locating quench in SRF cavities by detecting second-sound waves has been gaining popularity in SRF laboratories. The technique is based on measurements of time delays between the quench, as determined by the RF system, and arrival of the 2nd sound wave to the multiple detectors placed around the cavity in superfluid helium. Unlike multi-channel temperature mapping, this approach requires only few sensors and simple readout electronics; it can be used with SRF cavities of almost arbitrary shape. One of its drawbacks is that being an indirect method it requires one to solve an inverse problem to find a location of a quench. We tried to solve this inverse problem by using a parametric forward model. By analyzing the data we found that a simple model where 2nd-sound emitter is a near-singular source does not describe the physical system well enough. A time-dependent analysis of a quench process can help us to put forward a more adequate model. We present here our current algorithm to solve the inverse problem and discuss the experimental results.  
 
TUP042 RF Measurements and Numerical Simulations for the Model of the Bilbao Linac Double Spoke Cavity 886
 
  • J.L. Munoz, I. Bustinduy, N. Garmendia, V. Toyos
    ESS Bilbao, Bilbao, Spain
  • E. Asua
    UPV-EHU, Leioa, Spain
  • F.J. Bermejo
    Bilbao, Faculty of Science and Technology, Bilbao, Spain
  • V. Etxebarria, J. Portilla
    University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain
  • J. Feuchtwanger
    ESS-Bilbao, Zamudio, Spain
  • J. Lucas
    Elytt Energy, Madrid, Spain
  
  A model of a double spoke resonant cavity (operating frequency 352.2 MHz, βg=0.39) has been designed and fabricated in aluminium. The RF characteristics of the cavity have been measured in our laboratory. Experimental measurements have involved the determination of the main cavity parameters, and the characterization of the accelerating electric field profile along the cavity axis by means of a fully automated bead-pullmethod. Additionally, numerical simulations using COMSOL code have been used to fully characterize the cavity. Electromagnetic numerical simulations of the cavity have been also performed to determine its main figures of merit and to identify the most suitable position for opening a port to install a power coupler. In this paper we report the cavity cold model description, the experimental setup and corresponding techniques, together with the numerical methods. The obtained results are described and discussed in detail.  
 
TUP044 A Comparison of Superconducting RF Structures Optimized for β = 0.285 889
 
  • Z.A. Conway, R.L. Fischer, M.P. Kelly, A. Kolomiets, B. Mustapha, P.N. Ostroumov
    ANL, Argonne, USA
  
  Recent advances in low-beta superconducting RF technology have enabled the proposal and construction of ever-increasing-intensity ion accelerators, e.g. The Facility for Rare Isotope Beams (FRIB) at Michigan State University and Project-X at Fermilab. Superconducting TEM-class structures are required for these accelerators and beam quality preservation and cost efficiency are of the highest importance. This paper presents a comparison of the superconducting TEM-class cavities available for the acceleration of ions in the energy range of 16 to 55 MeV/u in order to guide their selection in future ion accelerator projects.  
 
TUP046 Superconducting 72 MHz β=0.077 Quarter-wave Cavity for ATLAS 892
 
  • M.P. Kelly, Z.A. Conway, S.M. Gerbick, M. Kedzie, R.C. Murphy, P.N. Ostroumov, T. Reid
    ANL, Argonne, USA
  
  A 72 MHz superconducting (SC) niobium quarter-wave cavity (QWR) optimized for β=0.077 has been built and tested as part of a beam intensity upgrade of the ATLAS SC heavy-ion linac. The two-gap cavity, designed to accelerate ions over the velocity range 0.06<β<0.12 and provide 2.5 MV of accelerating voltage per cavity at T=4.5 Kelvin, is based on a highly optimized electromagnetic design to reduce surface electric and magnetic fields. Horizontal electropolishing on the complete cavity with the helium jacket, is similar to that performed on 1.3 GHz ILC-type cavities and is a first for a low-β TEM cavity. This development is part of a broader effort to demonstrate ~120 mT surface fields with Rs~5 nΩ in 2 K operation for low-β cavities with the aim of substantially reducing the footprint for future ion linacs. First rf cold test results show the highest accelerating gradients (13.4 MV/m, leff=βλ) and voltage/cavity (4.3 MV) achieved for this class of SC cavity.  
 
TUP051 Design and First Cold Test of BNL Superconducting 112 MHz QWR for Electron Gun Applications 898
 
  • S.A. Belomestnykh, I. Ben-Zvi, X. Chang, R. Than
    BNL, Upton, Long Island, New York, USA
  • C.H. Boulware, T.L. Grimm, B. Siegel, M.J. Winowski
    Niowave, Inc., Lansing, Michigan, USA
  
  Brookhaven National Laboratory and Niowave, Inc. have designed, fabricated, and performed the first cold test of a superconducting 112 MHz quarter-wave resonator (QWR) for electron gun experiments. The first cold test of the QWR cryomodule has been completed at Niowave. The paper discusses the cryomodule design, presents the cold test results, and outline plans to upgrade the cryomodule for future experiments.
Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. The work at Niowave is supported by the U.S. DOE under SBIR contract No. DE-FG02-07ER84861 		 
 
TUP052 HOM Damping Properties of Fundamental Power Couplers in the Superconducting Electron Gun of the Energy Recovery LINAC at Brookhaven National Laboratory 901
 
  • L.R. Hammons, H. Hahn
    BNL, Upton, Long Island, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Among the accelerator projects under construction at the Relativistic Heavy Ion Collider (RHIC) is an R&D energy recovery LINAC (ERL) test facility. The ERL includes both a five-cell superconducting cavity as well as a superconducting, photoinjector electron gun. Because of the high-charge and high-current demands, effective higher-order mode (HOM) damping is essential, and several strategies are being pursued. Among these is the use of the fundamental power couplers as a means for damping some HOMs. Simulation studies have shown that the power couplers can play a substantial role in damping certain HOMs, and this presentation will discuss these studies along with measurements. 		 
 
TUP053 Ferrite HOM Load Surrounding a Ceramic Break 904
 
  • L.R. Hammons, H. Hahn
    BNL, Upton, Long Island, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Several future accelerator projects at the Relativistic Heavy Ion Collider are being developed using a super-conducting electron energy recovery LINAC along with a superconducting electron gun as the source. All of the projects involve high-current, high-charge operation and require effective higher-order mode (HOM) damping to achieve the performance objectives. Among the HOM designs being developed is a waveguide-type HOM load for the electron gun consisting of a ceramic break surrounded by ferrite tiles. This design is innovative in its approach and achieves a variety of ends including broadband HOM damping and protection of the superconducting cavity from potential damage to the ferrite tiles. Furthermore, the ceramic is an effective thermal transition. This design may be useful in various applications since it readily allows for replacement of the ferrite tiles with other materials and may also be useful for testing the absorbing properties of these materials. In this paper, the details of the design will be discussed along with current modelling and testing results as well as future plans. 		 
 
TUP054 Mechanical Design of 56 MHz Superconducting RF Cavity for RHIC Collider 907
 
  • C. Pai, I. Ben-Zvi, A. Burrill, X. Chang, G.T. McIntyre, R. Than, J.E. Tuozzolo, Q. Wu
    BNL, Upton, Long Island, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
A 56 MHz Superconducting RF Cavity operating at 4.4K is being constructed for the RHIC collider. This cavity is a quarter wave resonator with beam transmission along the centreline. This cavity will increase collision luminosity by providing a large longitudinal bucket for stored bunches of RHIC ion beam. The major components of this assembly are the niobium cavity with the mechanical tuner, its titanium helium vessel and vacuum cryostat, the support system, and the ports for HOM and fundamental dampers. The cavity and its helium vessel must meet the ASME pressure vessel code and it must not be sensitive to frequency shift due to pressure fluctuations from the helium supply system. Frequency tuning achieved by a two stage mechanical tuner is required to meet performance parameters. This tuner mechanism pushes and pulls the tuning plate in the gap of niobium cavity. The tuner mechanism has two separate drive systems to provide both coarse and fine tuning capabilities. This paper discusses the design detail and how the design requirements are met. 		 
 
TUP055 Design and Preliminary Test of the 1500 MHz NSLS-II Passive Superconducting RF Cavity 910
 
  • J. Rose, W.K. Gash, B.N. Kosciuk, V. Ravindranath, S.K. Sharma, R. Sikora, N.A. Towne
    BNL, Upton, Long Island, New York, USA
  • C.H. Boulware, T.L. Grimm, C. Krizmanich, B. Kuhlman, N. Miller, B. Siegel, M.J. Winowski
    Niowave, Inc., Lansing, Michigan, USA
  
  NSLS-II is a new ultra-bright 3 GeV 3rd generation synchrotron radiation light source. The performance goals require operation with a beam current of 500mA and a bunch current of at least 0.5mA. Ion clearing gaps are required to suppress ion effects on the beam. The natural bunch length of 3mm is planned to be lengthened by means of a third harmonic cavity in order to increase the Touschek limited lifetime. Earlier work described the design alternatives and the geometry selected for a copper prototype. We subsequently have iterated the design to lower the R/Q of the cavity and to increase the diameter of the beam pipe ferrite HOM dampers to reduce the wakefield heating. A niobium cavity and full cryomodule including LN2 shield, magnetic shield and insulating vacuum vessel have been fabricated and installed.  
 
TUP056 BNL 703 MHz Superconducting RF Cavity Testing 913
 
  • B. Sheehy, Z. Altinbas, I. Ben-Zvi, D.M. Gassner, H. Hahn, L.R. Hammons, J.P. Jamilkowski, D. Kayran, J. Kewisch, N. Laloudakis, D.L. Lederle, V. Litvinenko, G.T. McIntyre, D. Pate, D. Phillips, C. Schultheiss, T. Seda, R. Than, W. Xu, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
  • A. Burrill
    JLAB, Newport News, Virginia, USA
  • T. Schultheiss
    AES, Medford, NY, USA
  
  Funding: This work received support from Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The Brookhaven National Laboratory (BNL) 5-cell, 703 MHz superconducting RF accelerating cavity has been installed in the high-current energy recovery linac (ERL) experiment. This experiment will function as a proving ground for the development of high-current machines in general and is particularly targeted at beam development for an electron-ion collider (eRHIC). The cavity performed well in vertical tests, demonstrating gradients of 20 MV/m and a Q0 of 1010. Here we will present its performance in the horizontal tests, and discuss technical issues involved in its implementation in the ERL. 		 
 
TUP057 The Fundamental Power Coupler and Pick-up of the 56 MHz Cavity for RHIC 916
 
  • Q. Wu, S. Bellavia, I. Ben-Zvi, C. Pai
    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.
A fundamental power coupler (FPC) is designed to obtain the ability of fast tuning the 56MHz SRF cavity in RHIC. The FPC will be inserted from one of the chemical cleaning ports at the rear end of the cavity with magnetic coupling to the RF field. The size and the location of the FPC are decided based on the required operational external Q of the cavity. The FPC is designed with variable coupling that would cover a range of power levels, and it is thermally isolated from the base temperature of the cavity, which is 4.2K. A 1kW power amplifier will also be used to close an amplitude control feedback loop. In this paper, we discuss the coupling factor of the FPC with the carefully chosen design, as well as the thermal issues. 		 
 
TUP058 Fundamental Damper Power Calculation of the 56MHz SRF Cavity for RHIC 919
 
  • Q. Wu, S. Bellavia, I. Ben-Zvi, M.C. Grau, G. Miglionico, C. Pai
    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.
At each injection and extraction period of RHIC operation, the beam frequency will be sweeping across a wide range, and some of the harmonics will cross the frequency of the 56MHz SRF cavity. To avoid cavity excitation during these periods, a fundamental damper was designed for the quarter-wave resonator to heavily detune the cavity. The power extracted by the fundamental damper should be compliant with the cooling ability of the system at all stages. In this paper, we discussed the power output from the fundamental damper when it is fully extracted, inserted, and during its movement. 		 
 
TUP059 Multipacting in a Grooved Choke Joint at SRF Gun for BNL ERL Prototype 922
 
  • W. Xu, S.A. Belomestnykh, I. Ben-Zvi, A. Burrill, D. Kayran, G.T. McIntyre, B. Sheehy
    BNL, Upton, Long Island, New York, USA
  • D. Holmes
    AES, Medford, NY, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The 703 MHz superconducting gun for BNL ERL prototype was tested at JLab with and without choke-joint and cathode stalk. Without choke-joint and cathode stalk, the gradient reached 25MV/m with Q0~6·109. The gun cathode insertion port is equipped with a choke joint with triangular grooves for multipacting suppression. We carried out tests with choke-joint and cathode stalk. The test results show that there are at least two barriers at about 5MV/m and 3.5 MV/m. We considered several possibilities and finally found that the limitation was because the triangular grooves were rounded after BCP, which caused strong multipacting in the choke-joint. This paper presents the primary test result of test results of the gun and discusses the multipacting analysis in the choke-joint. It also suggests possible solutions for the gun and multipacting suppressing for a similar structure. 		 
 
TUP060 New HOM Coupler Design for High Current SRF Cavity 925
 
  • W. Xu, S.A. Belomestnykh, I. Ben-Zvi, H. Hahn, E.C. Johnson
    BNL, Upton, Long Island, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Damping higher order modes (HOMs) significantly to avoid beam instability is a challenge for the high current Energy Recovery Linac-based eRHIC at BNL. To avoid the overheating effect and high tuning sensitivity, current, a new band-stop HOM coupler is being designed at BNL. The new HOM coupler has a bandwidth of tens of MHz to reject the fundamental mode, which will avoid overheating due to fundamental frequency shifting because of cooling down. In addition, the S21 parameter of the band-pass filter is nearly flat from first higher order mode to 5 times the fundamental frequency. The simulation results showed that the new couplers effectively damp HOMs for the eRHIC cavity with enlarged beam tube diameter and two 120° HOM couplers at each side of cavity. This paper presents the design of HOM coupler, HOM damping capacity for eRHIC cavity and prototype test results. 		 
 
TUP062 Design of Coupler for the NSLS-II Storage Ring Superconducting RF Cavity 931
 
  • M. Yeddulla, J. Rose
    BNL, Upton, Long Island, New York, USA
  
  NSLS-II requires four superconducting cavities working at 499.68 MHz. These cavities should support a 500 mA beam current. To operate the cavities in over-damped coupling condition, an External Quality Factor (Qext) of ~ 65000 is required. We have modified the existing coupler for the CESR-B cavity which has a Qext of ~ 200,000 to meet the requirements of NSLS-II. CESR-B cavity has an aperture coupler with a coupler "tongue" connecting the cavity to the waveguide. We have optimized the length, width and thickness of the "tongue" as well as the width of the aperture to increase the coupling using the three dimensional electromagnetic field solver, HFSS. Several possible designs will be presented.  
 
TUP063 HOM Measurements with Beam at the Cornell Injector Cryomodule 934
 
  • S. Posen, M. Liepe
    CLASSE, Ithaca, New York, USA
  
  Funding: NSF
The Cornell ERL injector prototype is undergoing commissioning and testing for running unprecedented currents in an electron cw injector. This paper discusses preliminary measurements of HOMs in the injector prototype’s superconducting RF cryomodule. These include HOM spectra up to 30 GHz measured via small antennae located at the HOM beam line absorbers between the SRF cavities. The spectra are compared at different beam currents and repetition rates. The shape of the spectra are compared to ABCI simulations of the loss factor spectrum of the cryomodule beam line. The total HOM power dissipated in the HOM loads was also measured with beam on, which allowed for an estimate of the loss factor. This measurement was accomplished via temperature sensors on the loads, calibrated to input power by heaters on the loads. 		 
 
TUP064 Designing Multiple Cavity Classes for the Main Linac of Cornell's ERL 937
 
  • N.R.A. Valles, M. Liepe
    CLASSE, Ithaca, New York, USA
  
  Funding: Work supported by NSF Grant No. PHY-0131508, and NSF/NIH-NIGMS Grant No. DMR-0937466
Cornell is currently developing a high current Energy Recovery Linac. The baseline 7-cell cavity design for the main linac has already been completed, and prototyping has begun, as of Fall 2010. Previous work showed that increasing the relative cavity-to-cavity frequency spread increases the beam break-up current through the linac. Simulations show that expected machining variations will introduce a relative HOM frequency spread of 0.5·10-3, corresponding to 150 mA of threshold current. The key idea of this work is to increase the relative cavity-to-cavity frequency spread by designing several classes of 7-cell cavities obtained by making small changes to the baseline center cell shape. This allows a threshold current in excess of 450 mA, which is well above the 100 mA goal for the Cornell Energy Recovery Linac. 		 
 
TUP066 Three-cell Traveling-wave Superconducting Test Structure 940
 
  • P.V. Avrakhov, A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • S. Kazakov, N. Solyak, G. Wu, V.P. Yakovlev
    Fermilab, Batavia, USA
  
  Use of a superconducting traveling wave accelerating (STWA) structure* with a small phase advance per cell rather than a standing wave structure may provide a significant increase of the accelerating gradient in the ILC linac. For the same surface electric and magnetic fields the STWA achieves an accelerating gradient 1.2 larger than TESLA-like standing wave cavities. The STWA allows also longer acceleration cavities, reducing the number of gaps between them. However, the STWA structure requires a SC feedback waveguide to return the few hundreds of MW of circulating RF power from the structure output to the structure input. A test single-cell cavity with feedback was designed, manufactured and successfully tested** demonstrating the possibility of a proper processing to achieve a high accelerating gradient. These results open the way to take the next step of the TW SC cavity development: to build and test a traveling-wave three-cell cavity with a feedback waveguide. The latest results of the single-cell cavity tests are discussed as well as the design of the test 3-cell TW cavity.
* P. Avrakhov, et al, Phys. of Part. and Nucl. Let, 2008, Vol. 5, No. 7, p. 597
** G. Wu, et al, IPAC 2010, THPD048 		 
 
TUP069 Status of the Mechanical Design of the 650 MHz Cavities for Project X 943
 
  • S. Barbanotti, M.S. Champion, M.H. Foley, C.M. Ginsburg, I.G. Gonin, C.J. Grimm, T.J. Peterson, L. Ristori, V.P. Yakovlev
    Fermilab, Batavia, USA
  
  In the high-energy section of the Project X Linac, acceleration of H- ions takes place in superconducting cavities operating at 650 MHz. Two families of five-cell elliptical cavities are planned: β = 0.61 and β = 0.9. A specific feature of the Project X Linac is low beam loading, and thus, low bandwidth and higher sensitivity to microphonics. Efforts to optimize the mechanical design of the cavities to improve their mechanical stability in response to the helium bath pressure fluctuations will be presented. These efforts take into account constraints such as cost and ease of fabrication. Also discussed will be the overall design status of the cavities and their helium jackets.  
 
TUP070 EM Design of the Low-Beta SC Cavities for the Project X Front End 946
 
  • I.G. Gonin, S. Barbanotti, P. Berrutti, L. Ristori, N. Solyak, V.P. Yakovlev
    Fermilab, Batavia, USA
  
  The low-energy part of the Project X H-linac includes three types of superconducting single spoke cavities (SSR) with β = 0.11, 0.21 and 0.4 operating at the fundamental TEM-mode at 325MHz. In this paper we present the detailed EM optimization of cavity shapes having the goal to minimize the peak electric and magnetic fields. We also discuss the importance of the integration of EM and mechanical design.  
 
TUP071 High Power Tests of Dressed Superconducting 1.3 GHz RF Cavities 949
 
  • A. Hocker, E.R. Harms, A. Lunin, A.I. Sukhanov
    Fermilab, Batavia, USA
  
  Funding: U.S. Department of Energy, Contract No. DE-AC02-07CH11359
A single-cavity test cryostat is used to conduct pulsed high power RF tests of superconducting 1.3 GHz RF cavities at 2 K. The cavities under test are welded inside individual helium vessels and are outfitted (“dressed”) with a fundamental power coupler, higher-order mode couplers, magnetic shielding, a blade tuner, and piezoelectric tuners. The cavity performance is evaluated in terms of accelerating gradient, unloaded quality factor, and field emission, and the functionality of the auxiliary components is verified. Test results from the first set of dressed cavities are presented here. 		 
 
TUP072 High Power Couplers for Project X Linac 952
 
  • S. Kazakov, M.S. Champion, M. Kramp, Y. Orlov, O. Pronitchev, V.P. Yakovlev
    Fermilab, Batavia, USA
  
  Project X, a multi-megawatt proton sources is under development in Fermi National Accelerator Laboratory. The key element of the project is a superconducting (SC) 3GV CW proton liner accelerator (linac). The linac includes 5 types of SC accelerating cavities of three 325 and 650 MHz frequencies. The cavities consumes up to 30 kW average RF power and need proper main couplers. Requirements and approach to the coupler design are discussed in the report. New cost effective schemes of the couplers are described. Results of electrodynamics and thermal simulations are presented.  
 
TUP074 Experiments on HOM Spectrum Manipulation in a 1.3 GHz ILC SC Cavity 958
 
  • T.N. Khabiboulline, N. Solyak, V.P. Yakovlev
    Fermilab, Batavia, USA
  
  Superconducting cavities with high operating Q will be installed in the Project-X, a superconducting linac, which is under development at Fermilab. Possibility of cavity design without HOM couplers considered. Rich spectrum of the beam and large number of cavities in ProjectX linac can result to resonance excitation of some high order modes with high shunt impedance. Under scope of study of High Order Modes (HOM) damping the manipulation with HOM spectrum in cold linac is considered. Results of detuning HOM spectrum of 1.3 GHz cavities at 2K in Horizontal Test Station of Fermilab are presented. Possible explanation of the phenomena is discussed.  
 
TUP075 Cavity Loss Factors of Non-relativistic Beams for Project X 961
 
  • A. Lunin, S. Kazakov, V.P. Yakovlev
    Fermilab, Batavia, USA
  
  Cavity loss factor calculation is an important part of total cryolosses estimation for the super conductive (SC) accelerating structures. There are two approaches how to calculate cavity loss factors, the integration of a wake potential over the bunch profile and the combining of loss factors for individual cavity modes. We applied both methods in order to get reliable results for non-relativistic beam. The time domain CST solver was used for a wake potential calculation and the frequency domain HFSS code was used for the cavity eigenmodes spectrum findings. Finally we present the results of cavity loss factors simulations for a non-relativistic part of the ProjectX and analyze it for various beam parameters.  
 
TUP076 First High Power Pulsed Tests of a Dressed 325 MHz Superconducting Single Spoke Resonator at Fermilab 964
 
  • R.L. Madrak, J. Branlard, B. Chase, C. Darve, P.W. Joireman, T.N. Khabiboulline, A. Mukherjee, T.H. Nicol, E. Peoples-Evans, D.W. Peterson, Y.M. Pischalnikov, L. Ristori, W. Schappert, D.A. Sergatskov, W.M. Soyars, J. Steimel, I. Terechkine, V. Tupikov, R.L. Wagner, R.C. Webber, D. Wildman
    Fermilab, Batavia, USA
  
  In the recently commissioned superconducting RF cavity test facility at Fermilab (SCTF), a 325 MHz, β=0.22 superconducting single-spoke resonator (SSR1) has been tested for the first time with its input power coupler. Previously, this cavity had been tested CW with a low power, high Qext test coupler; first as a bare cavity in the Fermilab Vertical Test Stand and then fully dressed in the SCTF. For the tests described here, the design input coupler with Qext ~ 106 was used. Pulsed power was provided by a Toshiba E3740A 2.5 MW klystron.  
 
TUP077 Vibrational Measurements for Commissioning SRF Accelerator Test Facility at Fermilab 967
 
  • M.W. McGee, J.R. Leibfritz, A. Martinez, Y.M. Pischalnikov, W. Schappert
    Fermilab, Batavia, USA
  
  Funding: Operated by Fermi Research Alliance, LLC, under Contract No. DE-AC02- 07CH11359 with the U.S. Department of Energy.
The commissioning of two cryomodule components is underway at Fermilab’s Superconducting Radio Frequency (SRF) Accelerator Test Facility. The research at this facility supports the next generation high intensity linear accelerators such as the International Linear Collider (ILC), a new high intensity injector (Project X) and other future machines. These components, Cryomodule #1 (CM1) and Capture Cavity II (CC2) which contain 1.3 GHz cavities are connected in series in the beamline and through cryogenic plumbing. Studies regarding characterization of ground motion, technical and cultural noise continue. Mechanical transfer functions between the foundation and critical beamline components have been measured and overall system displacement characterized. Baseline motion measurements given initial operation of cryogenic, vacuum systems and other utilities are considered.

 
 
TUP079 Cryomodule Design for 325 MHz Superconducting Single Spoke Cavities and Solenoids 970
 
  • T.H. Nicol, S. Cheban, R.L. Madrak, F. McConologue, T.J. Peterson, V. Poloubotko, L. Ristori, W. Schappert, I. Terechkine, B.A. Vosmek
    Fermilab, Batavia, USA
  
  Funding: U.S. Department of Energy
The low-beta section of the linac being considered for Project X at Fermilab contains several styles of 325 MHz superconducting single spoke cavities and solenoid based focusing lenses, all operating at 2 K. Each type of cavity and focusing lens will eventually be incorporated into the design of cryomodules unique to various sections of the linac front end. This paper describes the design of a multiple-cavity and solenoid cryomodule being developed to test the function of each of the main cryomodule systems – cryogenic systems and instrumentation, cavity and lens positioning and alignment, conduction-cooled current leads, magnetic shielding, cold-to-warm beam tube transitions, interfaces to interconnecting equipment and adjacent modules, as well as evaluation of overall assembly procedures. 		 
 
TUP080 Tests of a Tuner for a 325 MHz SRF Spoke Resonator 973
 
  • Y.M. Pischalnikov, E. Borissov, T.N. Khabiboulline, R.L. Madrak, R.V. Pilipenko, L. Ristori, W. Schappert
    Fermilab, Batavia, USA
  
  Funding: Work is supported by the U.S. Department of Energy
Fermilab is developing 325 MHz SRF spoke cavities for the proposed ProjectX. A compact fast/slow tuner has been developed to compensate microphonics and Lorentz force detuning. The modified tuner design and results of 4K tests of the first prototype are presented. 		 
 
TUP082 Test of a Coaxial Blade Tuner at HTS/FNAL 976
 
  • Y.M. Pischalnikov, S. Barbanotti, E.R. Harms, A. Hocker, T.N. Khabiboulline, W. Schappert
    Fermilab, Batavia, USA
  • A. Bosotti, C. Pagani, R. Paparella
    INFN/LASA, Segrate (MI), Italy
  
  Funding: Work is supported by the U.S. Department of Energy
Fermilab is building Cryomodule 2 for ILCTA facility at NML. A coaxial blade tuner has been chosen for the CM2 1.3GHz SRF cavities. A summary of results from cold test of the tuners in the Fermilab Horizontal Test Stand will be presented. 		 
 
TUP083 Phase and Frequency Locked Magnetrons for SRF Sources 979
 
  • M. Popovic, A. Moretti
    Fermilab, Batavia, USA
  • M.A.C. Cummings, A. Dudas, R.P. Johnson, M.L. Neubauer, R. Sah
    Muons, Inc, Batavia, USA
  
  Funding: Supported in part by STTR Grant DE-SC0002766
In order to make use of ferrite and/or garnet materials in the phase and frequency locked magnetron, for which Muons, Inc., received a Phase II award, materials must be tested in two orthogonal magnetic fields. One field is from the biasing field of the magnetron, the other from the biasing field used to control the ferrite within the anode structure of the magnetron. A test fixture was built and materials are being tested to determine their suitability. The status of those material tests are reported on in this paper. 		 
 
TUP084 Design of Single Spoke Resonators for Project X 982
 
  • L. Ristori, S. Barbanotti, M.S. Champion, M.H. Foley, I.G. Gonin, C.J. Grimm, T.N. Khabiboulline, N. Solyak, V.P. Yakovlev
    Fermilab, Batavia, USA
  
  Project X is based on a 3 GeV CW superconducting linac and is currently in the R&D phase awaiting CD-0 approval. The low-energy section of the Project X H-linac includes three types of super-conducting single spoke cavities operating at 325 MHz. SSR0 (26 cavities), SSR1 (18 cavities) and SSR2 (44 cavities) have a geometrical beta of = 0.11, 0.21 and 0.4 respectively. Single spoke cavities were selected for the linac in virtue of their higher r/Q. In this paper we present the decisions and analyses that lead to the final designs. Electro-magnetic and mechanical finite element analyses were performed with the purpose of optimizing the electro-magnetic design, minimizing frequency shifts due to Helium bath pressure fluctuations and providing a pressure rating for the resonators that allow their use in the cryomodules.  
 
TUP085 Assumptions for the RF Losses in the 650 MHz Cavities of the Project X Linac 985
 
  • A. Romanenko, L.D. Cooley, J.P. Ozelis, N. Solyak, V.P. Yakovlev
    Fermilab, Batavia, USA
  
  The requirements for the FNAL Project X cryogenic system depend on the dynamic heat loads of 650 MHz cavities. The heat load is in turn determined by quality factors of the cavities at the operating gradient. In this contribution we use the available experimental data to analyze quality factors achievable in 650 MHz linac cavities taking into account different RF losses contributions such as BCS resistance, residual resistance and a medium field Q-slope.  
 
TUP086 Microphonics control for Project X 988
 
  • W. Schappert, S. Barbanotti, J. Branlard, G.I. Cancelo, R.H. Carcagno, M.S. Champion, B. Chase, I.G. Gonin, A.L. Klebaner, D.F. Orris, T.J. Peterson, Y.M. Pischalnikov, L. Ristori, N. Solyak, V.P. Yakovlev
    Fermilab, Batavia, USA
  
  Funding: Work is supported by the U.S. Department of Energy
The proposed multi-MW Project X facility at Fermilab will employ cavities with bandwidths as narrow as 20 Hz. This combination of high RF power with narrow bandwidths combined requires careful attention to detuning control if these cavities are to be operated successfully. Detuning control for Projects X will require a coordinated effort between the groups responsible for various machine subsystems. Considerable progress in this area has been made over the past year. 		 
 
TUP088 Resonance Effects of Longitudinal HOMs in Project X Linac 991
 
  • V.P. Yakovlev, I.G. Gonin, T.N. Khabiboulline, A. Lunin, N. Solyak, A.I. Sukhanov, A. Vostrikov
    Fermilab, Batavia, USA
  • A. Saini
    University of Delhi, Delhi, India
  
  High-order mode influence on the beam longitudinal and transverse dynamics is considered for the 650 MHz section of the Project X linac. RF losses caused by HOMs are analyzed. Necessity of HOM dampers in the SC cavities of the linac is discussed.  
 
TUP089 Concept EM Design of the 650 MHz Cavities for the Project X 994
 
  • V.P. Yakovlev, M.S. Champion, I.G. Gonin, T.N. Khabiboulline, A. Lunin, N. Solyak
    Fermilab, Batavia, USA
  • A. Saini
    University of Delhi, Delhi, India
  
  Concept of the 650 MHz cavities for the Project X is presented. Choice of the basic parameters, i.e, number of cells, geometrical β, apertures, coupling coefficients, etc, is discussed. The cavities optimization criteria are formulated. Results of the RF design are presented for the cavities of both low-energy and high energy sections.  
 
TUP090 Design of a β = 0.29 Half-wave Resonator for the FRIB Driver Linac 997
 
  • J.P. Holzbauer, W. Hartung, J. Popielarski
    NSCL, East Lansing, Michigan, USA
  
  The driver linac for the Facility for Rare Isotope Beams will produce primary beams of ions at 200 MeV per nucleon for nuclear physics research. The driver linac will require 344 superconducting cavities, consisting of two types of Quarter-Wave Resonators (QWRs, β = 0.041 and 0.085) and two types of Half-Wave Resonators (HWRs, β = 0.29 and 0.53). A first-generation β = 0.29 HWR has been designed, prototyped, and tested. Second-generation versions of the other cavities are being developed, with one or more prototype having been tested. A second-generation β = 0.29 HWR design has been developed, making use of the experience with the first-generation β = 0.29 HWR and second-generation β = 0.53 HWR. In the second-generation design, the inner conductor is tapered to reduce the peak surface magnetic field. The outer conductor is a straight tube to increase the mechanical stiffness and reduce the sensitivity of the resonant frequency to bath pressure fluctuations. Optimization was employed to minimize the peak surface electric field. The second-generation β = 0.29 HWR design will be presented, including the RF design and mechanical analysis.  
 
TUP094 Novel Crab Cavity RF Design 1006
 
  • M.L. Neubauer, A. Dudas, R. Sah
    Muons, Inc, Batavia, USA
  • R.A. Rimmer, H. Wang
    JLAB, Newport News, Virginia, USA
  
  Funding: Supported in part by DOE SBIR grant DE-SC0005444
A 20-50 MV integrated transverse voltage is required for the Electron-Ion Collider. The most promising of the crab cavity designs that have been proposed in the last five years are the TEM type crab cavities because of the higher transverse impedance. The TEM design approach is extended here to a hybrid crab cavity that includes the input power coupler as an integral part of the design. A prototype was built with Phase I monies and tested at JLAB. The results reported on, and a system for achieving 20-50 MV is proposed. 		 
 
TUP096 Beam Pipe HOM Absorber for SRF Cavities 1012
 
  • R. Sah, A. Dudas, M.L. Neubauer
    Muons, Inc, Batavia, USA
  • G.H. Hoffstaetter, M. Liepe, H. Padamsee, V.D. Shemelin
    CLASSE, Ithaca, New York, USA
  • K. Ko, C.-K. Ng, L. Xiao
    SLAC, Menlo Park, California, USA
  
  Funding: Supported in part by DOE SBIR grant DE-SC0002733 and USDOE Contract No. DE-AC05-84-ER-40150.
Superconducting RF (SRF) systems typically contain resonances at unwanted frequencies, or higher order modes (HOM). For storage ring and linac applications, these higher modes must be damped by absorbing them in ferrite and other lossy ceramic materials. Typically, these absorbers are brazed to substrates that are often located in the drift tubes adjacent to the SRF cavity. These HOM absorbers must have broadband microwave loss characteristics and must be thermally and mechanically robust, but the ferrites and their attachments are weak under tensile and thermal stresses and tend to crack. Based on prior work on HOM loads for high current storage rings and for an ERL injector cryomodule, a HOM absorber with improved materials and design is being developed for high-gradient SRF systems. This work will use novel construction techniques (without brazing) to maintain the ferrite in mechanical compression. Attachment techniques to the metal substrates will include process techniques for fully-compressed ferrite rings. Prototype structures will be fabricated and tested for mechanical strength under thermal cycling conditions. 		 
 
TUP097 Fundamental and HOM Coupler Design for the Superconducting Parallel-Bar Cavity 1015
 
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • S.U. De Silva
    JLAB, Newport News, Virginia, USA
  
  The superconducting parallel-bar cavity is currently being considered as a deflecting system for the Jefferson Lab 12 GeV upgrade and as a crabbing cavity for a possible LHC luminosity upgrade. Currently the designs are optimized to achieve lower surface fields within the dimensional constraints for the above applications. A detailed analysis of the fundamental input power coupler design for the parallel-bar cavity is performed considering beam loading and the effects of microphonics. For higher beam loading the damping of the HOMs is vital to reduce beam instabilities generated due to the wake fields. An analysis of threshold impedances for each application and impedances of the modes that requires damping are presented in this paper with the design of HOM couplers.  
 
TUP098 Multipacting Analysis of the Superconducting Parallel-bar Cavity 1018
 
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • S.U. De Silva
    JLAB, Newport News, Virginia, USA
  
  The superconducting parallel-bar cavity is a deflecting/crabbing cavity with attractive properties, compared to other conventional designs, that is being considered for a number of applications. Multipacting can be a limiting factor to the performance of in any superconducting structure. In the parallel-bar cavity the main contribution to the deflection is due to the transverse deflecting voltage, between the parallel bars, making the design potentially prone to multipacting. This paper presents the results of analytical calculations and numerical simulations of multipacting in the parallel-bar cavity with resonant voltage, impact energies and corresponding particle trajectories.  
 
TUP099 Design of Superconducting Parallel-bar Deflecting/Crabbing Cavities with Improved Properties 1021
 
  • J.R. Delayen, S.U. De Silva
    ODU, Norfolk, Virginia, USA
  • J.R. Delayen
    JLAB, Newport News, Virginia, USA
  
  The superconducting parallel-bar cavity is a deflecting/crabbing cavity with attractive properties, compared to other conventional designs, that is being considered for a number of applications. All designs to-date have been based on straight loading elements and rectangular outer conductors. We present new designs of parallel-bar cavities using curved loading elements and circular or elliptical outer conductors, with significantly improved properties such as reduced surface fields and wider higher-order mode separation.  
 
TUP100 Design of Superconducting Spoke Cavities for High-velocity Applications 1024
 
  • J.R. Delayen, S.U. De Silva, C.S. Hopper
    ODU, Norfolk, Virginia, USA
  • J.R. Delayen
    JLAB, Newport News, Virginia, USA
  
  Superconducting single- and multi-spoke cavities have been designed to-date for particle velocities from β~0.15 to β~0.65. Superconducting spoke cavities may also be of interest for higher-velocity, low-frequency applications, either for hadrons or electrons. We present the design of spoke cavities optimized for β=0.8 and β=1.  
 
TUP101 Plasma Treatment of Single-Cell Niobium SRF Cavities 1027
 
  • J. Upadhyay, M. Nikolić, S. Popović, L. Vušković
    ODU, Norfolk, Virginia, USA
  • H.L. Phillips, A-M. Valente-Feliciano
    JLAB, Newport News, Virginia, USA
  
  In our previous work, we have demonstrated on flat sam- ples that plasma etching in Ar/Cl2 of bulk Nb is a viable alternative surface preparation technique to BCP and EP methods, with comparable etching rates. Here we report on the progress in experimental design for plasma processing of a single cell SRF cavity. The experiments are centered on two discharge types - asymmetric RF and low mode mi- crowave cavity discharge. We report on the experimental design of the setup with a specially designed single cell cavity with sample holders, and discuss the diagnostics of plasma and samples. We provide preliminary results on the RF discharge in the single cell that is to be the main part of the optimized experiment.  
 
TUP102 Cryogenic RF Material Testing at SLAC 1030
 
  • J. Guo, D.W. Martin, S.G. Tantawi, C. Yoneda
    SLAC, Menlo Park, California, USA
  
  Funding: The work is supported by the US Department of Energy
We have been developing an X-band cryogenic RF material testing system since 2005. By measuring the Q of a hemispherical cavity with the material sample at is flat interchangeable bottom, the system is capable to characterize the surface resistance of different materials at the temperature of 3-300K, as well as the quenching RF magnetic field of the superconducting samples at different temperatures. Using a SLAC X-band 50 MW klystron, the system can measure the quenching H-field of up to 300mT under current setup, with the possibility of further enhancement by changing the RF distribution configuration. 		 
 
TUP105 Fabrication of a Model Polyhedral Superconducting Cavity 1035
 
  • N. Pogue, P.M. McIntyre, A. Sattarov
    Texas A&M University, College Station, Texas, USA
  
  Funding: This work was supported in part by the U.S. Department of Energy under Grant DE-FG02-06ER41405
The polyhedral cavity is a superconducting cavity structure in which a multi-cell cavity is built from a Roman-arch assembly of arc segments. Each segment has a Tesla-like r-z profile, and is fabricated either by bonding a Nb foil to a Cu substrate wedge or by depositing a Nb surface on the Cu substrate. The segments are assembled with an arrangement of locking rings and alignment pins, with a controlled narrow gap between segments over much of the arc-span of adjoining segments. A tubular channel is machined in the mating surfaces of the Cu wedges. Dipole modes are suppressed by locating along each channel a tube coated with rf-terminating ferrite. A first model of the cavity is being built to investigate mode structure, evaluate alternatives for the Nb surface fabrication, and develop assembly procedures. 		 
 
TUP106 Effect of Surface Flow on Topography in Niobium Electropolishing 1038
 
  • M.J. Kelley, C.E. Reece
    JLAB, Newport News, Virginia, USA
  • L. Zhao
    The College of William and Mary, Williamsburg, USA
  
  Funding: This work has been supported by U.S. DOE Contract No. DE-AC05-06OR23177 to Jefferson Lab
Electropolishing (EP) is reliably delivering improved performance of multi-celled niobium SRF accelerator cavities, attributed to the smoother surface obtained. This superior leveling is a consequence of an etchant concentration gradient layer that arises in the HF-H2SO4 electrolyte adjacent to the niobium surface during polishing. Electrolyte circulation raises the prospect that fluid flow adjacent to the surface might affect the diffusion layer and impair EP performance. In this study, preliminary bench-top experiments with a moving electrode apparatus were conducted. We find that flow conditions approximating cavity EP show no effects attributable to depletion layer disruption. 		 
 
TUP107 RF-thermal Combined Simulations of a Superconducting HOM Coaxial Coupler 1041
 
  • G. Cheng, H. Wang
    JLAB, Newport News, Virginia, USA
  • D.N. Smithe
    Tech-X, Boulder, Colorado, USA
  
  Funding: This work is supported by Jefferson LAB and Tech-X CRADA #2009S005 on “Simulations of Electromagnetic and Thermal Characteristics of SRF Structures”.
To benchmark a multi-physics code VORPAL developed by Tech-X, the High Order Mode (HOM) coaxial coupler design implemented in Jefferson Lab’s 12GeV upgrade cryomodules is analyzed by use of commercial codes, such as ANSYS, HFSS and Microwave Studio. Testing data from a Horizontal Test Bed (HTB) experiment on a dual-cavity prototype are also utilized in the verification of simulation results. The work includes two stages: first, the HOM feedthrough that has a high RRR niobium probe and sapphire insulator is analyzed for the RF-thermal response when there is traveling wave passing through; second, the HTB testing condition is simulated and results from simulation are compared to thermal measurements from HTB tests. The analyses are of coupled-field nature and involve highly nonlinear temperature dependent thermal conductivities and electric resistivities for the eight types of materials used in the design. Accuracy and efficiency are the main factors in evaluation of the performance of the codes. 		 
 
TUP108 Summary Report for the C50 Cryomodule Project 1044
 
  • M.A. Drury, G.K. Davis, J.F. Fischer, C. Grenoble, J. Hogan, L.K. King, K. Macha, J.D. Mammosser, C.E. Reece, A.V. Reilly, J. Saunders, H. Wang
    JLAB, Newport News, Virginia, USA
  • E. Daly, J.P. Preble
    ITER Organization, St. Paul lez Durance, France
  
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract DE-AC05-06OR23177.
The Thomas Jefferson National Accelerator Facility has recently completed the C50 cryomodule refurbishment project. The goal of this project was to enable robust 6 GeV, 5 pass operation of the Continuous Electron Beam Accelerator Facility (CEBAF). The scope of the project included removal, refurbishment and reinstallation of ten CEBAF cryomodules at a rate of three per year. The refurbishment process included reprocessing of SRF cavities to eliminate field emission and to increase the nominal gradient from the original 5 MV/m to 12.5 MV/m. New “dogleg“ couplers were installed between the cavity and helium vessel flanges to intercept secondary electrons that produce arcing in the fundamental Power Coupler (FPC). Other changes included new ceramic RF windows for the air to vacuum interface of the FPC and improvements to the mechanical tuner. Damaged or worn components were replaced as well. All ten of the refurbished cryomodules are now installed in CEBAF and are currently operational. This paper will summarize the performance of the cryomodules. This paper will also look at problems that must be addressed by future refurbishment projects.
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. 		 
 
TUP109 Fabrication, Treatment and Testing of a 1.6 Cell Photo-injector Cavity for HZB 1047
 
  • P. Kneisel
    JLAB, Newport News, Virginia, USA
  • T. Kamps, J. Knobloch, O. Kugeler, A. Neumann
    HZB, Berlin, Germany
  • R. Nietubyc
    The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock, Poland
  • J.K. Sekutowicz
    DESY, Hamburg, Germany
  
  Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177..
As part of a CRADA (Cooperative Research and Development Agreement) between Forschungszentrum Dresden (FZD) and JLab we have fabricated and tested after appropriate surface treatment a 1.5 cell, 1300 MHz RRR niobium photo-injector cavity to be used in a demonstration test at BESSY*. Following a baseline test at JLab, the cavity received a lead spot coating of ~8 mm diameter deposited with a cathode arc at the Soltan Institute on the endplate made from large grain niobium. It had been demonstrated in earlier tests with a DESY built 1.5 cell cavity – the original design – that a lead spot of this size can be a good electron source, when irradiated with a laser light of 213 nm . In the initial test with the lead spot we could measure a peak surface electric field of ~ 29 MV/m; after a second surface treatment, carried out to improve the cavity performance, but which was not done with sufficient precaution, the lead spot was destroyed and the cavity had to be coated a second time. This contribution reports about the experiences and results obtained with this cavity.
* A. Neumann et al., “CW Superconducting RF Photoinjector Development for Energy Recovery Linacs”, LINAC10, September 13-17, 2010, Tsukuba, Japan.
 		 
 
TUP111 Multipactoring Observation, Simulation and Suppression on a Superconducting TE011 Cavity 1050
 
  • H. Wang, G. Ciovati
    JLAB, Newport News, Virginia, USA
  • L. Ge, Z. Li
    SLAC, Menlo Park, California, USA
  
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and COMPASS of SciDAC No.
A superconducting cavity of the same shape as used for the development of superconducting photo injectors has been built for the studies of high magnetic field induced Q slope due to the local heating. The multipactoring problem has been observed on the TE011 mode, 3.3GHz with magnetic field barriers. To understand and overcome this problem, 3D multipactoring simulations by Omega3P and Track3P have been done and found these to be one-point multipactors pulled out from the flat bottom surface by finite normal component of electric field. Asymmetric coupling ports on the side of the beam tube could have caused the distortion of the TE011 mode. The thermometry measurement later confirmed the predicted impact locations. A structure modification has been adopted based on the simulation prediction. More experimental results with the new geometry will allow further comparison with the 3D multipactoring simulations. 		 
 
WEOBS5 Status of the Short-Pulse X-ray Project (SPX) at the Advanced Photon Source (APS) 1427
 
  • R. Nassiri, N.D. Arnold, G. Berenc, M. Borland, D.J. Bromberek, Y.-C. Chae, G. Decker, L. Emery, J.D. Fuerst, A.E. Grelick, D. Horan, F. Lenkszus, R.M. Lill, V. Sajaev, T.L. Smith, G.J. Waldschmidt, G. Wu, B.X. Yang, A. Zholents
    ANL, Argonne, USA
  • J.M. Byrd, L.R. Doolittle, G. Huang
    LBNL, Berkeley, California, USA
  • G. Cheng, G. Ciovati, J. Henry, P. Kneisel, J.D. Mammosser, R.A. Rimmer, L. Turlington, H. Wang
    JLAB, Newport News, Virginia, USA
  
  Funding: Work at Argonne is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11354.
The Advanced Photon Source Upgrade project (APS-U) at Argonne includes implementation of Zholents’* deflecting cavity scheme for production of short x-ray pulses. This is a joint project between Argonne National Laboratory, Thomas Jefferson National Laboratory, and Lawrence Berkeley National Laboratory. This paper describes performance characteristics of the proposed source and technical issues related to its realization. Ensuring stable APS storage ring operation requires reducing quality factors of these modes by many orders of magnitude. These challenges reduce to those of the design of a single-cell SC cavity that can achieve the desired operating deflecting fields while providing needed damping of all these modes. The project team is currently prototyping and testing several promising designs for single-cell cavities with the goal of deciding on a winning design in the near future.
*A. Zholents et al., NIM A 425, 385 (1999). 		 
slides icon Slides WEOBS5 [1.730 MB]  
 
WEOCS7 Crab Cavity and Cryomodule Prototype Development for the Advanced Photon Source 1472
 
  • H. Wang, G. Cheng, G. Ciovati, W.A. Clemens, J. Henry, P. Kneisel, P. Kushnick, K. Macha, J.D. Mammosser, R.A. Rimmer, G. Slack, L. Turlington
    JLAB, Newport News, Virginia, USA
  • R. Nassiri, G.J. Waldschmidt, G. Wu
    ANL, Argonne, USA
  
  Funding: Work is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11354.
Two single-cell, superconducting, squashed elliptical crab cavities with waveguides to damp Higher Order Modes (HOM) and Lower Order Mode (LOM) have been designed and prototyped for the Short Pulse X-ray (SPX) project at the Advanced Photon Source (APS). The Baseline cavity with LOM damper on the beam pipe has been vertically tested and exceeded its performance specification with over 0.5MV deflecting voltage. The Alternate cavity design which uses an “on-cell” waveguide damper is preferred due to its larger LOM impedance safety margin. Its prototype cavity has been fabricated by a Computer Numerical Controlled (CNC) machine and is subject to further testing. The conceptual design, layout and analysis for various cryomodule components are presented. 		 
slides icon Slides WEOCS7 [7.008 MB]  
 
THOAS4 Enhancement of RF Breakdown Threshold of Microwave Cavities by Magnetic Insulation 2053
 
  • D. Stratakis
    UCLA, Los Angeles, California, USA
  • J.C. Gallardo, R. B. Palmer
    BNL, Upton, Long Island, New York, USA
  
  Funding: This work is funded by US Dept. of Energy grant number DE AC02-98CH10886.
Limitations on the maximum achievable accelerating gradient of microwave cavities can influence the performance, length, and cost of particle accelerators. Gradient limitations are widely believed to be initiated by electron emission from the cavity surfaces. Here, we show that field emission is effectively suppressed by applying a tangential magnetic field to the cavity walls, so higher gradients can be achieved. Numerical simulations indicate that the magnetic field prevents electrons leaving these surfaces and subsequently picking up energy from the electric field. Implementation of the proposed concept into prospective particle accelerator applications is studied by two specific examples - a multi TeV lepton-antilepton collider and a linear muon accelerator driver for an intense neutrino source. 		 
slides icon Slides THOAS4 [1.441 MB]  
 
THOCS1 Would >50 MV/m be Possible with Superconducting RF Cavities? 2119
 
  • T. Tajima
    LANL, Los Alamos, New Mexico, USA
  
  Several laboratories are working on the development of thin-film superconductor technology to overcome the fundamental limit of ~50 MV/m accelerating gradient with niobium SRF cavities. Efforts at LANL attempt to enhance the sustainable surface magnetic field by coating thin layers of superconductors, such as MgB2 on top of niobium. The coating techniques being developed and the results of RF critical field and surface resistance measurements that were obtained in collaboration with other national laboratories, universities and industry will be presented.  
slides icon Slides THOCS1 [0.751 MB]  
 
THOCS2
 SRF Materials R&D  
 
  • L.D. Cooley
    Fermilab, Batavia, USA
  
  Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The push for higher yield of high-gradient SRF cavities has recently received support from a nationwide multi-disciplinary program to understand limitations of superconducting cavities and improve their fabrication and processing. Materials science has revealed deeper understanding of how oxidation, cold work, hydrogen, and roughness affect both fundamental behavior as well as real performance after different processing stages. Processing advances, such as optical inspection, laser re-melting, tumbling, and atomic layer deposition, provide opportunities to optimize the technology, benefiting the design of future SRF-based accelerators such as ILC or Project X. 		 
slides icon Slides THOCS2 [4.470 MB]  
 
THOCS3 R&D Status for In-Situ Plasma Surface Cleaning of SRF Cavities at Spallation Neutron Source 2124
 
  • S.-H. Kim, M.T. Crofford
    ORNL, Oak Ridge, Tennessee, USA
  • M. Doleans
    NSCL, East Lansing, Michigan, USA
  • J.D. Mammosser
    JLAB, Newport News, Virginia, USA
  • J. Saunders
    ORNL RAD, Oak Ridge, Tennessee, USA
  
  Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
The SNS SCL is reliably operating at 0.93 GeV output energy with an energy reserve of 10MeV with high availability. Most of the cavities exhibit field emission, which directly or indirectly (through heating of end groups) limits the gradients achievable in the high beta cavities in normal operation with the beam. One of the field emission sources would be surface contaminations during surface processing for which mild surface cleaning, if any, will help in reducing field emission. An R&D effort is in progress to develop in-situ surface processing for the cryomodules in the tunnel without disassembly. As the first attempt, in-situ plasma processing has been applied to the CM12 in the SNS SRF facility after the repair work with a promising result. This paper will report the R&D status of plasma processing in the SNS. 		 
slides icon Slides THOCS3 [3.294 MB]  
 
THOCS5 Resonance Control in SRF Cavities at FNAL 2130
 
  • Y.M. Pischalnikov, W. Schappert
    Fermilab, Batavia, USA
  • M. Scorrano
    INFN-Pisa, Pisa, Italy
  
  Funding: Work is supported by the U.S. Department of Energy
An adaptive Least Squares algorithm to control Lorentz force detuning in SRF cavities has been developed and tested in the HTS at FNAL. During open-loop tests in the FNAL HTS, the algorithm was able to reduce LFD in a 9-cell 1.3 GHz elliptical cavity operating at 35 MV/m from 600 Hz to less than 10 Hz during both the fill and the flattop. The algorithm was also able to adapt to changes in the gradient of the cavity and to changes in the pulse length. 		 
slides icon Slides THOCS5 [3.572 MB]  
 
THOCS6 Progress in Cavity and Cryomodule Design for the Project X Linac 2133
 
  • M.S. Champion, S. Barbanotti, M.H. Foley, C.M. Ginsburg, I.G. Gonin, C.J. Grimm, J.S. Kerby, S. Nagaitsev, T.H. Nicol, T.J. Peterson, L. Ristori, N. Solyak, V.P. Yakovlev
    Fermilab, Batavia, USA
  
  The continuous wave 3 GeV Project X Linac requires the development of two families of cavities and cryomodules at 325 and 650 MHz. The baseline design calls for three types of superconducting single-spoke resonators at 325 MHz having betas of 0.11, 0.22, and 0.42 and two types of superconducting five-cell elliptical cavities having betas of 0.61 and 0.9. These cavities shall accelerate a 1 mA H− beam initially and must support eventual operation at 4 mA. The electromagnetic and mechanical designs of the cavities are in progress and acquisition of prototypes is planned. The heat load to the cryogenic system is up to 25 W per cavity in the 650 MHz section, thus segmentation of the cryogenic system is a major issue in the cryomodule design. Designs for the two families of cryomodules are underway.  
slides icon Slides THOCS6 [2.241 MB]  
 
FROBS1 World-wide Experience with SRF Facilities 2575
 
  • A. Hutton, A. Carpenter
    JLAB, Newport News, Virginia, USA
  
  The speaker will review and analyze the performance of existing SRF facilities in the world, addressing issues of usage and availability for different customers (HEP research, material sciences, ADS). Lessons learned should be summarized for proposed future facilities (ILC, ProjectX, Muon Collider).  
slides icon Slides FROBS1 [5.473 MB]  
 
FROBS3 Progress on Superconducting RF for the Cornell Energy-Recovery-Linac 2580
 
  • M. Liepe, G.H. Hoffstaetter, S. Posen, J. Sears, V.D. Shemelin, M. Tigner, N.R.A. Valles, V. Veshcherevich
    CLASSE, Ithaca, New York, USA
  
  Cornell University is developing the superconducting RF technology required for the construction of a 5 GeV, 100 mA light source driven by an energy-recovery linac. Currently, a 100 mA injector cryomodule is under extensive testing and prototypes of the components of the SRF main linac cryomodule are under development, fabrication and testing. In this paper we give an overview of these recent activities at Cornell.  
slides icon Slides FROBS3 [10.577 MB]  
 
FROBS4 NSLS-II RF Systems 2583
 
  • J. Rose, W.K. Gash, B. Holub, Y. Kawashima, H. Ma, N.A. Towne, M. Yeddulla
    BNL, Upton, Long Island, New York, USA
  
  The NSLS-II RF systems include solid state modulators for the S-band klystrons powering the traveling wave sections for the 200 MeV injector linac, 7 cell cavity with IOT amplifier for the 3 GeV booster synchrotron and superconducting 500 MHz cavities powered by klystrons and a passive 1500 MHz SRF cavity for the 3 GeV, 500 mA storage ring. The systems are controlled by digital I/Q modulators fed by an ultra-low noise master oscillator. System overviews will be given along with preliminary test data.  
slides icon Slides FROBS4 [1.041 MB]  
 
FROBS5 1.3 GHz Superconducting RF Cavity Program at Fermilab 2586
 
  • C.M. Ginsburg, T.T. Arkan, S. Barbanotti, H. Carter, M.S. Champion, L.D. Cooley, C.A. Cooper, M.H. Foley, M. Ge, C.J. Grimm, E.R. Harms, A. Hocker, R.D. Kephart, T.N. Khabiboulline, J.R. Leibfritz, A. Lunin, J.P. Ozelis, Y.M. Pischalnikov, A.M. Rowe, W. Schappert, D.A. Sergatskov, A.I. Sukhanov, G. Wu
    Fermilab, Batavia, USA
  
  Funding: Work supported by Fermi Research Alliance, LLC under contract DE-AC02-07CH11359 with the U.S. Department of Energy.
At Fermilab, 9-cell 1.3 GHz superconducting RF (SRF) cavities are prepared, qualified, and assembled into cryomodules, for Project X, an International Linear Collider, or other future projects. The 1.3 GHz SRF cavity program includes targeted R&D on 1-cell 1.3 GHz cavities for cavity performance improvement. Production cavity qualification includes cavity inspection, surface processing, clean assembly, and one or more cryogenic low-power CW qualification tests which typically include performance diagnostics. Qualified cavities are welded into helium vessels and are cryogenically tested with pulsed high-power. Well performing cavities are assembled into cryomodules for pulsed high-power testing in a cryomodule test facility, and possible installation into a beamline. The overall goals of the 1.3 GHz SRF cavity program, supporting facilities, and accomplishments are described. 		 
slides icon Slides FROBS5 [3.749 MB]  
 
FROBS6 High Current SRF Cavity Design for SPL and eRHIC 2589
 
  • W. Xu, I. Ben-Zvi, R. Calaga, H. Hahn, E.C. Johnson, J. Kewisch
    BNL, Upton, Long Island, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
In order to meet the requirements of high average current accelerators, such as the Superconducting Proton Linac (SPL) at CERN and the electron–ion collider (eRHIC) at BNL, a high current 5-cell SRF cavity, called BNL3 cavity, was designed. The optimization process aimed at maximizing the R/Q of the fundamental mode and the geometry factor G under an acceptable RF field level of Bpeak/Eacc or Epeak/Eacc. In addition, a pivotal consideration for the high current accelerators is efficient damping of dangerous higher-order modes (HOM) to avoid inducing emittance degradation, cryogenic loading or beam-breakup (BBU). To transport the HOMs out of the cavity, the BNL3 cavity employs a larger beam pipe, allowing the propagation of HOMs but not the fundamental mode. Moreover, concerning the BBU effect, the BNL3 cavity is aimed at low (R/Q)Qext for dangerous modes, including dipole modes and quadrupole modes. This paper presents the design of the BNL3 cavity, including the optimization for the fundamental mode, and the BBU limitation for dipole and quadrupole modes. The BBU simulation results show that the designed cavity is qualified for high-current, multi-pass machines such as eRHIC. 		 
slides icon Slides FROBS6 [2.577 MB]