Author: Arnold, A.
Paper Title Page
MOPIK003 Improvement of the Photoemission Efficiency of Magnesium Photocathodes 500
 
  • R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate
    HZDR, Dresden, Germany
  • P. Patra
    IUAC, New Delhi, India
 
  Funding: The work is supported by the European Community under the FP7 programme (EuCARD-2) and by the German Federal Ministry of Education and Research (BMBF) grant 05K12CR1.
To improve the quality of photocathodes is one of the critical issues in enhancing the stability and reliability of photo-injector systems. Presently the primary choice is to use metallic photocathodes for the ELBE SRF Gun-II to reduce the risk of contamination of the superconducting cavity. Magnesium has a low work function (3.6 eV) and shows high quantum efficiency (QE) up to 0.3 % after laser cleaning. The SRF Gun II with an Mg photocathode has successfully provided electron beam for ELBE users. However, the present cleaning process with a high intensi-ty laser (activation) is time consuming and generates unwanted surface roughness. This paper presents the investigation of alternative surface cleaning procedures, such as thermal treatment. The QE and topography of Mg samples after treatment are reported.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK003  
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MOPIK008 Numerical Studies on a Modified Cathode Tip for the ELBE Superconducting RF Gun 515
 
  • E.T. Tulu, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  • A. Arnold
    HZDR, Dresden, Germany
 
  Future light sources such as synchrotron radiation sources driven by an Energy Recovery Linac (ERL), Free Electron Laser (FEL) or THz radiation sources have in common that they require injectors, which provide high-brilliance, high-current electron beams in almost continuous operation. Thus, the development of appropriate highly brilliant electron sources is a central factor. A promising approach for this key component is provided by superconducting radiofrequency photoinjectors (SRF guns) [*]. Since 2007, the free-electron laser FELBE at HZDR successfully operates such a SRF gun under real conditions and equipped with all components [**]. Nevertheless, there are limitations caused by multipacting which should be overcome in order to further improve the gun [***]. One aspect in order to reach this aim lies in studying various modifications of the cathode tip [****]. This contribution will present the effectiveness of isosceles triangular grooves with respect to MP.
* Arnold, et al., NIM A, 593, 57, (2008).
** J. Teichert, et al., 2008 NSS/MIC, Dresden, Germany.
*** J. Teichert, et al., J. Phys.: Conf. Ser. 298(2011), 012008.
**** E. T. Tulu, et al., IPAC2014, p652, Dresden, Germany.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK008  
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TUPAB033 Design of a Stripline Kicker for the ELBE Accelerator 1393
 
  • Ch. Schneider, A. Arnold, J. Hauser, P. Michel, G.S. Staats
    HZDR, Dresden, Germany
 
  ELBE is a linac based cw electron accelerator serving different secondary beams one at a time. Depending on the user demand the bunch repetition rate may vary from single pulse up to 13 MHz. For the future different end stations should be served simultaneously, hence specific bunch patterns have to be kicked to other beam-lines. To use e.g. one bunch out of the bunch train very short kicking durations have to be realized. The variability of the bunch pattern and the frequency resp. switching time are one of the main arguments for a stripline-kicker combined with HV-switches as basic concept. A nearly homogenous field in the kicker has to be realized for uniform deflection of the electron bunch and emittance grow of the bunch has to be kept as low as possible. Furthermore the fast switching ability of the kicker demands for a fast decay of the HV-pulse resp. its reflections in the structure implying a specific design of the kicker elements. For this reason a design with two tapered active electrodes and two ground fenders was optimized in time and frequency domain with the software package CST. Additionally a first prototype was manufactured for laboratory and first beam-line tests.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB033  
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THPAB012 Beam Transport Optimization for Applying an SRF Gun at the ELBE Center 3712
 
  • P.N. Lu, A. Arnold, P. Murcek, J. Teichert, H. Vennekate, R. Xiang
    HZDR, Dresden, Germany
 
  An SRF gun at the ELBE center has been operated with a magnesium cathode. Electron beams were produced with a maximum bunch charge of 200 pC and an emit-tance of 7.7 μm. Simulations have been conducted with ASTRA and Elegant for applying the SRF gun to ELBE user experiments, including neutron beam generation, positron beam generation, THz radiation and Compton backscattering experiment. Beam transport has been optimized to solve the best beam performance for these user stations at the bunch charge of 200 pC. Simulation results indicate that the SRF gun is potential to benefit the high bunch charge applications at ELBE.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB012  
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