MEDeGUN commissioning results

MEDeGUN [1] is an electron gun to be used in an Electron Beam Ion Source (EBIS) designed to serve as C⁶⁺ source for LINAC-based 2^nd generation hadron therapy facilities [2]. The latter require short pulses of at least 1^*10⁸ particles at a repetition rate of 400 Hz, which exceeds the possibilities of currently used electron cyclotron resonance ion sources (ECRIS) and EBISes. The design of MEDeGUN is based on a combination of electrostatic and magnetic compression, which is commonly referred to as Brillouin gun. As previous devices have shown, it is difficult to achieve the design goals in this configuration due to the high sensitivity of the electron beam to any field imperfection. Therefore, the number of interfaces between the cathode, Wehnelt and anode electrodes have been reduced to only two in our design. In spring 2017, the MEDeGUN assembly was installed at the TwinEBIS test bench at CERN [3]. We have since then propagated an electron beam of more than 1 A at 10 keV electron energy through the 2T solenoid with losses of less than 1 mA. We will here present the commissioning results and discuss them with respect to the design goals.