Keyword: extraction
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TUPSO21 SwissFEL Cathode Load-lock System cathode, vacuum, gun, laser 259
 
  • R. Ganter, M. Bopp, N. Gaiffi, T. Le Quang, M. Pedrozzi, M. Schaer, T. Schietinger, L. Schulz, L. Stingelin, A. Trisorio
    PSI, Villigen PSI, Switzerland
 
  The SwissFEL electron source is an RF photo-injector in which the photo-cathode plug can be exchanged. Without load-lock, the cathode exchange takes about one week and cathode surface gets contaminated in the atmosphere during installation, leading to unpredictable quantum efficiency (QE) fluctuations. This motivated the construction of a load lock system to prepare and insert cathodes in the photo-injector. This load lock system consists of three parts: the preparation chamber, the transportable vacuum suitcase and the gun load lock chamber. This three parts system gives the possibility to prepare the cathode surface with methods like vacuum firing and plasma cleaning. The QE can be checked and the plug can be inserted in the gun without breaking vacuum. This will allow establishing an optimized a reproducible cathode preparation procedure. Since several cathodes can be loaded in advance, the exchange procedure reduces the machine shutdown to a few hours (shorter RF conditioning). The system is described and first experience with its use is reported.  
 
TUPSO67 Design Optimization of 100 Kv DC Gun Wehnelt Electrode for FEL Linac at LEBRA electron, gun, cathode, simulation 387
 
  • T. Sakai, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nakao, K. Nogami, T. Tanaka
    LEBRA, Funabashi, Japan
 
  The 125-MeV electron linac at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University has been used for generation of the near infrared FEL and the Parametric X-ray Radiation. In addition, the THz beam generated in a bending magnet became available in the FEL experimental rooms in 2012 by transporting in the FEL optical beam line. The electron gun system for the LEBRA linac can extract the electron beam in three modes, the full bunch, the superimposed and the burst modes. However, the shape of the electron gun wehnelt electrode has not been optimized for the operation with the superimposed or the burst modes; the wehnelt was designed for use in the full bunch operation. The beam trace simulation suggested that the beam extracted from the cathode in the superimposed and the burst modes was slightly lost at the anode due to the strong space charge effect resulted from a high peak extraction current. Therefore, simulation of the beam trace was carried out to optimize the wehnelt shape for the maximum beam extraction efficiency for all the beam operation modes. The present paper reports the result of the simulation on the optimized electron gun design.