High Power 95 GHz Gyro-Devices with Permanent or Conventional Solenoid Magnets

A 2nd harmonic compact low voltage gyrotron operating in the TE021 mode at 94 or 95 GHz on the second cyclotron harmonic produced by a compact normal magnet will produce 100kWCW or more at high efficiency (35% or better before collector energy recovery) using a 50 kV magnetron injection gun (MIG) beam. The gyrotron uses the smallest cavity, ~2.2 cm long, in the TE021 mode which will permit operation down to 100 kWCW at high efficiency and allow the smallest magnet. The main magnet that produces the 18 kG cavity field is only 15 cm OD by 7 cm long with a 12 mm ID clear bore. This very compact small bore design, to minimize the coil power of the electromagnet, has ample space for coolants. The power required for the main 18 kG magnet is only about 4.6 kW, not including the coil power for the 0.8 kG MIG field or a collector. This compares to about 7 kWCW of rf Ohmic loss in the cavity at 100 kWCW output. The coils are copper foil wound and edge cooled by attached water-cooled copper plates. The 50 kV MIG produces ~10% axial velocity spread at an alpha of 2.0.