Design of a 170 GHz waveguide-based notch filter for burning plasma diagnostics protection

Intense stray radiation from high-power 170 GHz gyrotrons used for electron cyclotron heating in magnetic confinement fusion devices poses a severe threat to sensitive microwave diagnostic receivers. To protect these critical front-end systems in next-generation burning plasma experiments, this paper presents ENOCH (Electromagnetic Notch Protection of Electron Cyclotron Heating), a novel 170 GHz waveguide-based notch filter. Engineered within a standard WR-06 waveguide geometry, the proposed eight-cavity resonant structure provides robust power protection without sacrificing diagnostic performance. Full-wave electromagnetic simulations demonstrate an exceptional rejection depth exceeding 60 dB at the 170 GHz interference frequency alongside a remarkably low insertion loss across the primary 134-166 GHz diagnostic passband. Furthermore, a coupled electromagnetic-thermal analysis confirms the filter's structural resilience under 100 W of continuous-wave input power. Compact, manufacturable, and easily integrated, the ENOCH design fulfills the stringent operational criteria required for reliable diagnostic protection in high-power, harsh environments typical of ITER- and ARC-class tokamaks.