High power test results of the Eli-NP S-Band gun fabricated with the new clamping technology without brazing

High gradient RF photoguns have been a key development to enable several applications of high quality electron beams. They allow the generation of beams with very high peak current and low transverse emittance, thus satisfying the tight demands of free-electron lasers, energy recovery linacs, Compton/Thomson sources and high-energy linear colliders. A new fabrication technique for this type of structures has been recently developed and implemented at the Laboratories of Frascati of the National Institute of Nuclear Physics (INFN-LNF, Italy). It is based on the use of special RF-vacuum gaskets, that allow a brazing-free realization process. The S-band gun of the ELI-NP gamma beam system (GBS) has been fabricated with this new technique. It operates at 100 Hz with 120 MV/m cathode peak field and 1.5 μs long RF pulses to house the 32 bunches necessary to reach the target gamma flux. High gradient tests, performed at full power and full repetition rate, have shown extremely good performances of the structure in terms of breakdown rate. In the paper, we report and discuss all the experimental results, the electromagnetic design and the mechanical realization processes.