Detaied design of (fixed) end mirror for high power/CW operations, Deliverable (a).4.2 of EFDA Task TW3-TPHE-ECHULB4

The task of this work, that follows the conceptual design of the end mirror set (deliverable (a).2.1), is to provide the optical design for the fixed end mirrors of the ITER Upper launcher for ECRH, minimising the beam size in the plasma region relevant for absorption. In this work: - The correct background is built for the evaluation of the mirror properties in term of steering range and focalization when the steering angle is varied. - The beam size in the relevant location (in-vacuum propagation) for two different possible surfaces is examined, with the aim of choosing the one most suitable for the task. - All the relevant beam parameters (including astigmatism) are given in the two cases to be used with beam-tracing codes for the related physics analysis (f). - Some options for beam launch with reduced angular range ("dedicated" to stabilization of single surfaces of safety factor "q"), and for launch with increased beam size at the waveguide output are also studied. - Some evaluations are given of the possible effect of beam distortion due to mirror non-ideal shape and to localized thermal expansion occurring in highpower CW operations. For the beam size evaluation a detailed model with a complete geometrical description of the optics layout of the RS launcher has been implemented in Mathematica® code. The description of beam parameters has been done according to the gaussian beam optics laws of propagation from the waveguide output to the first reflection and from the mirror to the plasma region.