Free electron maser amplifier experiments

We present results from the X-band reversed guide magnetic field Raman Free Electron Maser (FEM) amplifier experiment at Strathclyde University. The F EM has been designed for zero slippage to achieve maximum instantaneous ban dwidth. The tuneablity is further extended by the adjustment of beam voltag e and undulator field strength. A 1 kW TWT has been used as the input soure r for broadband measurements and two 25 kW magnetrons for saturated output power measurements at discrete frequencies. Results show an instantaneous - 3 dB bandwidth of 30% for a fixed cathode voltage and magnetic held. The d evice can be tuned over a range of 65% of the centre frequency by adjusting the cathode voltage. A saturated power of over 1 MW has been measured for 50 A input current. Broadband unsaturated gains of over 35 dB have been mea sured. An experiment using a 50 A beam from a thermionic cathode electron g un designed at Strathclyde is currently in progress. This a ill theoretical ly allow CW operation of the FEM using a DC undulator magnet and DC power s ource. (C) 2000 Published by Elsevier Science B.V. All rights reserved.