DESIGN AND CONSTRUCTION OF AN INDUCTION LINAC FOR A MM WAVE FREE-ELECTRON LASER FOR FUSION-RESEARCH

A new induction accelerator is designed and being constructed for appl ication to fusion research. The main characteristics of the new induct ion linac are: (1) Foils made of a new Fe-based nanocryostalline soft magnetic material ''Finemet'', which has a higher saturation flux dens ity and lower power loss than other commercially available Fe based am orphous alloys, are used. (2) The maximum beam energy and current will be 2.5 MeV, and 3 kA respectively; the accelerating voltage can be ke pt constant within +/- 1% during the pulse; the gradient of the voltag e in time dV(a) /dt can be controlled in the range of +/- 20%. (3) The acceleration units are divided into two parts; one is for the beam ge neration and the other is for post acceleration of the beam. The latte r is constructed so that the acceleration column may be separated from the driving circuit. We expect FEL radiation with a power of several hundred megawatts in the frequency range of 30-120 GHz, and tokamak he ating research is planned with the JAERI medium size tokamak JFT-2M.