High Average Power Investigation of Dielectric Dissipation in the W-Band Gyro-TWT

Abstract

The dielectric load gyro-traveling wave tube (gyro-TWT) is a primary high-power millimeter source, and its power capacity is limited by the thermal capacity of the attenuated dielectric. The heavy outgassing was observed when the gyro-TWT operated in a long pulse duration in the experiment. The heat dissipated on the dielectric, and its distribution is analyzed. Then the thermal performance for different pulse duration is investigated. The dielectric temperature reaches 390 °C and 214 °C for the pulse duration of 2 ms and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200 ~\mu \text{s}$ </tex-math></inline-formula> with a duty cycle of 10%, respectively. It indicates the thermal resistance of the dielectric limits the power capacity. The average power capacity in different pulse duration is evaluated. Then a high average power experiment is realized. A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${W}$ </tex-math></inline-formula> -band gyro-TWT is operated at 60.5 kV–9.4 A, with a pulse duration of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200 ~\mu \text{s}$ </tex-math></inline-formula> and a duty cycle of 16%. A peak power of 126.1 kW and an average power of 20.2 kW are obtained at 94 GHz.