Experimental study of high-power, saturated amplification in a sheet-beam, small-period-wiggler FEL (with applications to magnetic fusion research)

The study of sheet-beam, small-period-wiggler FELs as candidate sources for heating magnetic fusion plasmas has achieved a major milestone. In a proof-of-principle, pulsed experiment, saturated FEL amplifier operation was realized with 250 kW of output power at 86 GHz. Input microwave power was 1 kW, beam voltage as 450 kV and beam current was 17 A. The planar wiggler had a peak value of 3.8 kV, a period of 0.96 cm and was 67 cm long. The linear gain of 30 dB, saturated gain of 24 dB and saturated efficiency of 3% are all in good agreement with theoretical predictions for this FEL which operated in the Raman regime. Follow-on work would include development of a thermionic, sheet-beam, electron gun compatible with CW FEL operation, and adding a section of tapered wiggler to increase the output power and efficiency.