High power gyrotrons and their appplications

The gyrotron is the most powerful source of coherent radiation in the millimeter wave and terahertz region of the electromagnetic spectrum. Early research on the gyrotron was aimed at producing high average power gyrotron oscillators for use in plasma heating. Today, gyrotron oscillators produce over 1 MW of average power in continuous (CW) operation at frequencies up to 170 GHz. Such gyrotrons are a crucial part of the program to heat plasmas to temperatures suitable for nuclear fusion reactors. In recent years, operation of the gyrotron oscillator has been extended to the THz range, at moderate average power levels (tens to hundreds of watts) or, in pulsed mode, at tens to hundreds of kilowatts. Gyrotron amplifiers have also made significant advances, with extension of operating frequencies to 250 GHz and peak power levels to above 50 kW in W-Band (95 GHz). These recent advances in gyrotron oscillator and amplifier research and development have opened up a wide range of exciting new applications. Examples of important applications of gyrotrons include: high power radars for weather and defense; enhanced NMR spectroscopy of biomolecules; materials heating and processing; nuclear material detection; cancer detection and cancer therapy; terahertz imaging; gas and air breakdown by intense millimeter wave beams; rocket propulsion; wireless power beaming; and food processing and purification. The state-of-the-art of gyrotron research will be reviewed together with examples of present-day and proposed future novel applications.