A permanent magnet field source for a 140 GHz traveling wave tube

A 140 GHz wideband (7 GHz bandwidth) traveling wave tube was built and tested by Communication and Power Industry Canada Inc., under the auspices of U.S. Army Research Laboratory (ARL). Such a tube represents a high power (130 watts at a duty cycle of 1%) radiation source for high resolution radar at the atmospheric window at 140 GHz. Although the performance objectives of the tube were achieved, its applicability to military purposes was limited due to the massive (136 kg) electric solenoid that furnished the minimum required electron beam-focusing field of 8 kOe over a beam path of 6 cm. This mass coupled with the need for a power supply and the consumption of electrical energy would preclude its use in airborne, ballistic and small mobile surface vehicles.