MTX/ELF II microwave power measurements and calibration for the 2 GW, 140 GHz, ELF II free-electron laser

Techniques for measuring the power and frequency of the Electron Laser Facility (ELF)-II free-electron laser (FEL) used for plasma heating experiments on the Microwave Tokamak Experiment (MTX) have been developed. A multichannel 140-GHz receiver capable of measuring FEL power levels from 10 mW to 0.1 μW within an accuracy of ±1 dB and with a 50-dB dynamic range and a 2-ns response time has been designed. By using calibrated attenuators, it is possible to measure power levels from 10 GW to 0.1 μW. The microwave output of the FEL in a microwave load tank is sampled by using WR-8 or WR-28 stub waveguide antennas. Microwave turning mirrors are used to guide the microwave beam down an evacuated beam tube to the MTX. Stub, WR-8, fundamental-mode waveguide antennas are used for beam detection on the microwave turning mirrors