Calculation of Geometry Matrices for IRVBs for Application to 3D Tomography of Radiative Phenomena in LHD

Abstract

InfraRed imaging Video Bolometers (IRVBs) can provide hundreds of channels of bolometric data forming an image of the plasma radiation [B.J. Peterson, Rev. Sci. Instrum. 71, 3696 (2000)]. By calculating the geometry matrix (or response matrix) of the detector field of view (FoV) with respect to a predefined three dimensional (3D) plasma grid of plasma voxels these geometry matrices can be used for 3D tomography of the plasma radiation. This is done by assuming that the plasma reproduces itself every half field period. Then by combining the FOV of 3 IRVBs with different views of the plasma (top, tangential, semi-tangential), one large geometry matrix can be derived relating 1968 IRVB channels to 13,161 plasma voxels. Results indicate that FoVs should be modified or supplemented to view plasma voxels near the helical divertor xpoints of the diagonal cross-sections (5◦ <φ< 13◦) which are in the shadows of the helical coils.