Repetitive 30-GHz free-electron maser applicable for RF testing properties of materials

The paper is devoted to progress in development and application of the JINR-IAP FEM. This Bragg FEM generates 30 GHz pulses of up to 200 ns duration and 20-30 MW power with an efficiency on the level of ~25 %. Frequency tuning in the range of 6 % with a precision of about 0.1 % was realized by mechanical variation of the distance between the Bragg reflectors. A test facility to study surface heating effects at 30 GHz was constructed based on the FEM source. A special copper cavity modeled on high-Q accelerating structure has been designed with the expected temperature rise of the surface during each pulse of about 200°C. The cavity heating stress caused by 10
⁶
RF-pulses at a repetition rate of 1 Hz will be studied.