Q-band high-performance notch filters at 56 and 77 GHz notches for versatile fusion plasma diagnostics

A six-pole Q-band waveguide filter with a notch frequency above the has been developed for plasma diagnostics. The previous paper [Nishiura et al., J. Instrum. 10, C12014 (2015)] reported that exists within standard band. In this study, newly required extends function, which prevents thorny wave from being mixed into an instrument beyond bandwidth of waveguide. mode control technique cavities realizes deep and sharp shape filters 56 77 GHz notches, respectively. former attenuation more than 50 dB at 56.05 1.1 −3 dB. latter 55 76.95 1.6 electron cyclotron emission imaging (ECE) diagnostics implemented pair fabricated demonstrated ECE measurement successfully in intense stray radiation gyrotron.