Digital Fabrication and Reliability Evaluation Method for G-Band TWT Electron Optical System

Abstract

Terahertz traveling wave tubes (THz-TWTs) electron optical system (EOS) has strict fabrication accuracy requirements. The low reliability of traditional manual assembly always is the direct problem hindering the development of TWT to high frequency, high power, high efficiency, and high reliability. In this article, a digital fabrication and reliability evaluation method for THz-TWTs EOS was presented. First of all, through improving the gun shell structure and sealing molds, developing automatic and semi-automatic assembly methods, writing automatic geometric measure programs, measuring the thermal deformation of cathode and focusing electrode (FE) under working temperature, etc., the implementation of digital fabrication technology was completed, which promoted the fabrication accuracy (1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma \text{)}$</tex-math> </inline-formula> to 3–10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $</tex-math> </inline-formula> m and 0.05 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> –0.1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> . Then, in order to find the tolerance limit to keep the electronic trajectory stable and the balance between design reliability and fabrication reliability, the CST particle solver single and multi-parameter sweep function was used to analyze the EOS of a 0.22 THz-TWT. Based on the digital fabrication technology process capability, 6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma $</tex-math> </inline-formula> quality management theory, and equal proportion compress single parameter tolerance limit method, we defined four independent sensitive parameters, and calculated the reliability of THz-TWT EOS digital fabrication was not less than 72.47% by MINITAB software. This method can be used as a quantitative calculation of whether the TWT EOS design and fabrication are matched, and give appropriate tolerance and compensation range in the actual TWT fabrication process.