3D MULTIPACTING STUDY FOR THE ROSSENDORF SRF GUN

The development of the superconducting radio frequency photoinjector (SRF gun) is the most promising technology for many applications beside the DC photoinjector and the normal conducting radio frequency photoinjector. However, there are various challenges during the operation [1, 2]. Multipacting (MP) is one of the recent difficulty for the SRF gun. Thus, among the several ongoing investigations on this phenomenon, the experimental results indicates that the high MP current has been measured in the cathode unit of the SRF gun at Helmholtz-Zentrum Dresden-Rossendorf research institute. This limits the cavity fields (accelerating gradient). To better understand this process, a three and half cells 1.3 GHz TESLA-shape cavity with cathode was modeled in CST Studio Suite R ⃝ at the University of Rostock. All parameters were provided by Helmholtz-Zentrum Dresden-Rossendorf, Germany. The MP simulations have been performed with CST Microwave Studio R ⃝ (CST MWS) and CST Particle Studio R ⃝ (CST PS) [3] which are suitable and powerful for 3D electromagnetic designs. Further, CST PS provides the most advanced model of secondary emission [4]. The radio frequency fields are calculated using the eigenmode solver of CST MWS, whereas the CST PS is used for particle tracking simulation like [4, 5]. The purpose of these numerical simulations is to have a better understanding of MP in the Rossendorf SRF gun and to make a detailed analysis. The midterm goal is to find a new cavity shape, which might suppress the electron amplification so that the SRF gun will be able to operate up to an accelerating gradient of 50 MV/m.