Design of a high power Cherenkov FEL for industrial applications

(TU-4-12)

A. Doria, G.P. Gallerano, L.Giannessi, E. Giovenale  

ENEA - Divisione Fisica Applicata

ENEA is involved in the design of microwave industrial Free Electron Laser in the framework of a BRITE EC project. ENEA researchers focussed on the design of a high power, low cost 100 GHz FEL. In order for the system to be suitable for industrial applications, constraints on costs, safety and power must be fulfilled, in particular sytem should cost less than 100 kECU, maximum voltage should be about 100 kV and output power must be about 10 W CW, and a few kW for pulsed operation. A high average/power, high peak power Cherenkov FEL has been designed fulfilling these requirements. The advantage of a Cherenkov FEL (CFEL) respect to the conventional FELs is the fact that the electron beam couples longitudinally with the electromagnetic field. This implies that no relativistic beam is needed to generate short wavelength thus increasing the efficiency of the emission process. Spontaneous emission characteristics have been considering a finite size for the electron beam.

The proposed devices operate in three different regimes:

1)CW operation - oscillatory regime - low gain: with an e-beam energy of 102 keV, and a current of 250 mA it is possible to obtain 50 W CW output at 100 GHz

2)CW/Pulsed operation - oscillatory regime - medium gain: with an e-beam energy of 102 keV, and a current of 2 A it is possible to operate in pulsed mode with long pulses, with an output power of 8 kW at 100 GHz. To operate in CW mode it is necessary to utilise a 200 kW e-beam (such electron sources can be found commercially).

3)Pulsed operation - single pass device - high gain: with an e-beam energy of 102 keV, and a current of 250 A it is possible to obtain high power pulses of 10 MW at 100 GHz.

Details of the design will be presented, together with calculations.