A gyro-TWT with a space-charged limited gun

Most gyrotron traveling wave tubes (gyro-TWT) currently employ temperature-limited magnetron-injection electron guns to produce electron beams with high perpendicular to parallel velocity ratios. Certain problems with these guns have inspired the investigation of alternative space-charge-limited guns. An improved design technique applied to the helical transverse, magnetic "wiggler" employed in early cyclotron maser experiments shows promise for high power operation. A previously reported C-band gyro-TWT has been modified. The magnetron injection gun has been replaced with a Pierce-type electron gun. A bifilar helix of prescribed length capable of producing a helically varying transverse magnetic field for converting axial electron energy into transverse electron energy of low energy spread was placed between the Pierce gun and the rf interaction circuit. The rf interaction circuit was not changed. Substantial output power was achieved. Comparison of initial experimental results with previous results using the magnetron injection gun are presented.