Author: Kugeler, O.
Paper Title Page
MOPFI001 Characterization of a Superconducting Pb Photocathode in a SRF Gun Cavity 279
 
  • R. Barday, T. Kamps, O. Kugeler, A. Neumann, M. Schmeißer, J. Völker
    HZB, Berlin, Germany
  • P. Kneisel
    JLAB, Newport News, Virginia, USA
  • R. Nietubyć
    NCBJ, Świerk/Otwock, Poland
  • J.K. Sekutowicz
    DESY, Hamburg, Germany
  • J. Smedley
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Bundesministerium für Bildung und Forschung and Land Berlin. The Pb deposition activity is supported by EuCARD.
Photocathodes are a limiting factor for the next generation of ultra-high brightness photoinjector driven accelerators. We studied the behavior of a superconducting Pb cathode in the cryogenic environment of a superconducting rf gun cavity related to the quantum efficiency, its spatial distribution and the work function. Cathode surface contaminations can modify the performance of the photocathodes as well as the gun cavity. We discuss the possibilities to remove these contaminations.
 
 
MOPFI002 Results from Beam Commissioning of an SRF Plug-gun Cavity Photoinjector 282
 
  • M. Schmeißer, R. Barday, A. Burrill, A. Jankowiak, T. Kamps, J. Knobloch, O. Kugeler, P. Lauinger, A. Neumann, J. Völker
    HZB, Berlin, Germany
  • P. Kneisel
    JLAB, Newport News, Virginia, USA
  • R. Nietubyć
    NCBJ, Świerk/Otwock, Poland
  • J.K. Sekutowicz
    DESY, Hamburg, Germany
  • I. Will
    MBI, Berlin, Germany
 
  Superconducting rf photoelectron injectors (SRF guns) hold the promise to deliver high brightness, high average current electron beam for future lightsources or other applications demanding continuous wave operation of an electron injector. This paper discusses results from beam commissioning of a hybrid Pb coated plug-gun Nb cavity based SRF photoinjector for beam energies up to 3 MeV at Helmholtz-Zentrum Berlin. Emittance measurements and transverse phase space characterization with solenoid-scan and pepperpot methods will be presented.  
 
MOPFI003 SRF Photoinjector Cavity for BERLinPro 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.  
 
WEPWO002 RF Measurements of the 1.6 Cell Lead/Niobium Photoinjector in HoBiCaT 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.  
 
WEPWO004 Studies of Systematic Flux Expulsion in Superconducting Niobium 2316
 
  • J.M. Vogt, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
 
  The quality factor Q0 that can be obtained in a superconducting cavity is known to depend on various factors like niobium material properties, treatment history and magnetic shielding. We believe that cooling conditions have an additional impact, as they appear to influence the amount of trapped flux and hence the residual resistance. We have constructed a test stand using niobium rods to study flux trapping. Here we can precisely control the temperature and approach Tc from below in the superconducting state. Although the sample remains in the superconducting state, a change in the amount of trapped flux is visible. The procedure can be applied repeatedly resulting in a significantly lowered level of trapped flux in the sample. Furthermore, simulations using the Radia software package for Mathematica developed by the ESR were used to better unterstand the measured changes in magnetic flux around the Sample. Applying a similar procedure for minimization of trapped magnetic flux to a superconducting cavity could allow for reduction of the magnetic contribution to the surface resistance and result in a significant improvement of Q0.  
 
WEPWO009 Numerical Coupling Analyses of BERLinPro SRF Gun 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%.  
 
THOBB201 Pathway to a Post Processing Increase in Q0 of SRF Cavities 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]