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Ivkovic, S.

Paper Title Page
TUPEC015 High Gradient Electrodes for a Diode - RF Electron Gun 1743
 
  • C.H. Gough, S. Ivkovic, F. Le Pimpec, M. Paraliev
    PSI, Villigen
  
 

As part of the SwissFEL project at Paul Scherrer Institute, an electron gun test stand has been built and operated. The goal is to achieve an exceptionally low emittance beam with a charge of 200pC for XFEL application. The electron gun consists of a High Gradient (HG) pulsed diode followed by an RF acceleration structure. The diode has an adjustable gap and the cathode is pulsed at up to 500 kV. The electrons were extracted either from a near-flat cathode surface or a dedicated photo-source recessed in a hollow cathode surface. For the diode electrtodes, many metals, geometries and surface treatments were studied for their HG and photo emission suitability. Polished metal electrodes, single tips, field emitter arrays and electrodes coated with different Diamond Like Carbon (DLC) types were tested. In particular, we found that DLC coating had useful properties. Surface electric fields over 250MV/m (350 ~ 400kV, in pulsed mode) with negligible parasitic electron emission were achieved; when UV laser illumination was applied to DLC electrodes, it was possible to extract electron bunches of over 60pC at gradients up to 150MV/m.

  
TUPE042 Results of the PSI Diode-RF Gun Test Stand Operation 2233
 
  • F. Le Pimpec, B. Beutner, H.-H. Braun, R. Ganter, C.H. Gough, C.P. Hauri, R. Ischebeck, S. Ivkovic, K.B. Li, M. Paraliev, M. Pedrozzi, T. Schietinger, B. Steffen, A. Trisorio
    PSI, Villigen
  
 

In the framework of the SwissFEL project, an alternative electron source to an RF photo-gun was investigated. It consists of a high voltage (up to 500 kV), high gradient pulsed diode system followed by single stage RF acceleration at 1.5 GHz. The electrons are produced from photo-cathodes or from field emitter arrays. The final goal of this accelerator is to produce a 200 pC electron beam with a projected normalized emittance below 0.4 mm.mrad and a bunch length of less than 10 ps. We present comparisons between beam dynamic simulations and measurements, as well as thermal emittance and quantum efficiency (QE) measurements obtained by producing photo-electrons from various metal cathodes.