Design and Analysis of a Magnetron Injection Gun for G-Band TE₁₃ Mode Gyro-TWT

Abstract

Electron beam transportation stability is important to the gyro-traveling-wave tube (gyro-TWT). For conventional <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{G}$</tex-math> </inline-formula> -band TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{01}}$</tex-math> </inline-formula> mode magnetron injection gun (MIG), the transportation performance is unsatisfactory because of the small interaction tunnel. For the transportation problem, a MIG with a slotted cathode for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{G}$</tex-math> </inline-formula> -band TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{13}}$</tex-math> </inline-formula> mode gyro-TWT is proposed in this article. The MIG is designed and optimized, and a velocity ratio of 1.15 and a transverse velocity spread of 0.58% are obtained. Furthermore, the cathode has been produced and fabricated. A thermal test, a surface morphology test, and a computed tomography (CT) scan have been carried out. Then, beam quality and transportation stability are analyzed when thermal expansion, morphology deviation, stray electron, and magnetic field misalignment exist, respectively. The beam transportation performance is good under all conditions, and the total simulated velocity spread of the main electron is 3.3%.