Three types of fast-wave amplifiers were reported in this session. The gyrotron traveling-wave amplifier (gyro-TWT) features broad bandwidth with moderate output power while the gyroklystron amplifier is capable of high power amplification over a relatively narrow bandwidth. Sirigiri of MIT reported the first operation of their 140 GHz quasi-optical gyro-TWT, demonstrating 9 kW of power at a gain of 25 dB. The University of Maryland group is continuing the development of frequency-doubling coaxial gyroklystron amplifiers as drivers of linear colliders. Tens of MW of output power were reported by Lawson in the Ku-band with 4 cavities.

CPI and the University of Maryland have recently teamed up to extend the frontiers of the gyroklystron amplifier into the Ka-Band for testing and conditioning the CERN Compact Linear Collider. It is currently well into the design stage aimed at 50 MW peak power at 30 GHz, as is described by Blank. Calabazas Creek Research, Inc., in collaboration with the Maryland group, is developing a 10 MW, 91 GHz gyroklystron. As discussed by Neilson in their progress update, all major subassemblies have now been fabricated and are being cold tested. Hot test is planned for July, 2002.

The relative merits of single-frequency and frequency-multiplying gyroklystrons are analyzed in a theory talk by Nusinovich on behalf of the Maryland and UC Davis collaboration. The third type of gyro-amplifiers, reported by Whyte of the University of Strathclyde, is based on the Raman free electron maser operation in a reversed guide magnetic field. It features high efficiency (35%) and broad bandwidth (up to 70%) at MW power levels.