110 GHz notch-filter development at TEXTOR-94

After the installation of a 110 GHz gyrotron at TEXTOR-94 the development of 110 GHz notch-filter was necessary for protecting the sensitive Electron Cyclotron Emission (ECE)-diagnostic, covering the frequency range 104≤f≤148 GHz. The design and construction of a narrow (Δf≤1000 MHz) and deep (Amax≥50 dB) notch filter is explained. Furthermore the behaviour at different modes is studied. Also the influence of the aperture on the width of the notch as well as the influence of the number of used cavities on the depth of the notch and the losses in the pass band is studied and presented in the paper.