High Specific Power, Rapid Start-up 95 GHz Source Technology

Since the 1990's, applications requiring high power (>1 KW) millimeter wave energy have relied on either gyrotrons or multiple gryotwystron amplifiers. While the gryotwystron approach offers bandwidth and single point failure benefits, it is inherently more complex and larger than that of the single gyrotron. The gyrotron however requires a superconducting magnet to create the 3.7 Tesla field necessary for operation. Critical to the operation of the superconducting magnet and its start up is a closed cycle refrigeration system, or cryocooler, to cool the magnet to cryogenic (<100K) temperatures. With the advent of newer 2G superconducting material the maximum temperature required for operation of the superconducting magnet has been raised from 4 K to greater than 50 K. Typically cryocoolers for 4K operation have required greater than 8 kW of input power, provide cool down times in excess of 24 hours, and require compressors that orientation dependent. By using these new 2G superconductors and thus raising the operational temperature to 50 K it should be possible to reduce the input power requirement to less than 5 kW, provide cool down times less than 8 hours, and have an orientation independent cryocooler by developing a new cryocooler system specific to the requirements of gyrotron amplifiers.