CONTRACT F4E-OFC-958: PROVISION OF SUPPORT SERVICES FOR THE FINALISATION OF THE DESIGN OF THE EC UPPER LAUNCHER (EC UL) AND EX-VESSEL WAVEGUIDE SYSTEM (EC EW) Task Order #03: Provision of GRASP© and GRAY calculations for EC Launcher FDR (FRD2) Subtask:4 F4E-OFC-958_D5: GRASP ANALYSIS OF REFERENCE AND PERTURBED BEAMS

A simplified model of the ECH-UL was simulated with GRASP, a commercial antenna package. The eight nominal beams (pure HE11 at waveguide aperture) were mapped on all mirrors for the reference and upper, lower full beam steering range. Coordinates of geometric optics central ray and peak power density values are listed in this report for reference. Spillover losses were computed and found to be compliant with the 3% maximum requirement. Single-mode beam parameters were extrapolated from results of full electromagnetic calculations and listed here for a quick comparison with analytic models. One-dimensional beam profiles were also extracted for the same purpose along suitable lines, whose position and orientation are listed in Appendixes. The impact of the addition of a 7.5% power in LP11 spurious mode was assessed in terms of power distribution on mirrors and spillover losses. The position of the beam centroid was also computed for comparison with analytical beam squint estimates. The (first-pass) distribution of incident stray radiation was mapped on about 1/3 of the inner surface of a simplified model of the launcher. Position and orientation of all the maps are included in the report. Absorbed power was computed for all surfaces for stainless steel and copper-coated boundary conditions. Tables of peak and average incident and absorbed power, together with average angle of incidence, are included in the report to aid independent calculations on stray radiation distribution. Maps of the normal component of the Poynting vector were provided to IO, but are not included in the report because of the similarity with those of absorbed power. One-dimensional cuts in specified positions of a few most critical surfaces were computed and are included in an Appendix. A worst-case analytic model was made for treating narrow grooves in walls (e.g. thin gap between sub-mirrors). Simple recipes were provided (using results of full electromagnetic simulations) to estimate power loading as a function of groove parameters, to aid in assessing acceptable sizes for grooves. This report provides all the necessary information for cross-validation of the analytic models of beam propagation and beam squint induced by spurious modes. Furthermore, the results described in this report provide the necessary input for calculations of the distribution of stray radiation accounting for multiple reflections on walls.