Analysis of transmission characteristics for single and double disk windows

X. Yang1, B. Piosczyk1, R. Heidinger2, G. Dammertz1, M. Thumm1,3

Forschungszentrum Karlsruhe, Association EURATOM-FZK,
1Institut für Hochleistungsimpuls- und Mikrowellentechnik,

2Institut für Materialforschung I , D-76021 Karlsruhe, Germany

3 also Universität Karlsruhe, Institut für Höchstfrequenztechnik und Elektronik,

Kaiserstr. 12, D-76128 Karlsruhe, Germany





The work reports about window design studies for both the JET EP ECRH project and the ASDEX-Upgrade ECRH system. Detailed calculations of the millimeter wave transmission characteristics for conventional single-disk windows, for frequency tunable double-disk windows and for ultra-broadband Brewster windows have been performed. The geometry of the window unit has been optimized in order to obtain a suitable transmission characteristic, i.e. power reflection less than -20dB within a frequency bandwidth of about 1 GHz around the chosen frequencies. In particular the influence of mechanical tolerances on the transmission characteristic have been investigated in order to be able to specify the mechanical dimensions of the CVD-diamond disks and of the window unit. In case of the Brewster window, the thickness has been optimized to get low power reflection over a wide angle range around the Brewster angle.