Design and construction of an induction linac for a mm wave free electron laser for fusion research

Abstract A new induction accelerator is designed and being constructed for application to fusion research. The main characteristics of the new induction linac are: (1) Foils made of a new Fe-based nanocryostalline soft magnetic material “Finemet”, which has a higher saturation flux density and lower power loss than other commercially available Fe based amorphous alloys, are used. (2) The maximum beam energy and current will be 2.5 MeV, and 3 kA respectively; the accelerating voltage can be kept constant within ±1% during the pulse; the gradient of the voltage in time d V a d t can be controlled in the range of ±20%. (3) The acceleration units are divided into two parts; one is for the beam generation and the other is for post acceleration of the beam. The latter 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 heating research is planned with the JAERI medium size tokamak JFT-2M.