EFFECT OF THE SHIELDING BLOCK STRUCTURE ON BEAM PROPAGATION FOR THE ITER ECRH&CD UPPER LAUNCHER

In the context of the completion of the ITER ECRH&CD Upper Launcher detailed design phase, we conclude the beam truncation study on the focusing mirror and we perform an evaluation of the effect of the propagation through the shielding block structure on the beam propagation. For this purpose, we used a simplified version of the blanket module with different propagation paths and varying distance between beam center and wall.

The evolution of beams has been calculated with the electromagnetic code GRASP®, a numerical tool in which the detailed characteristics of the reflectors surfaces and the surrounding structures can be introduced and the resulting field propagation in vacuum can be computed including all the relevant effects. The description of the beam resulting from Physical Optics calculations takes into account the relevant causes of deformation and non gaussianity, such as aberration and beam truncation and diffraction from structure edge.

In the electromagnetic simulation, we first consider the extreme case of a beam running close to one corner all along the blanket length: in this worst case the beam is affected by two faces of the shield module. Intermediate cases (beam propagating close to one side or entering close to the edge and then deviating) are also considered.