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Tomographic imaging of MHD activity in tokamaks by combining diode arrays and a tangentially viewing pinhole camera

1988; American Institute of Physics; Volume: 59; Issue: 8 Linguagem: Inglês

10.1063/1.1140070

1527-2400

A. Holland, R. J. Fonck, E. T. Powell, S. Šesnić,

Nuclear Physics and Applications

Two 32-channel side-viewing soft x-ray diode arrays will be installed on PBX-M which will provide profile information in the horizontal and vertical directions with a time resolution up to 1 μs. The information from these arrays can be reconstructed to provide a high time-resolution poloidal emission profile using a maximum-entropy-based technique which incorporates the reconstructed profile from a tangentially viewing soft x-ray pinhole camera. The pinhole camera provides lower time-resolution (about 5 ms) shape information which has been reconstructed with the assumption of toroidal symmetry. The pinhole camera information supplements the information from the diode arrays, allowing a reconstruction which can resolve MHD fluctuations of the equilibrium profile. The pinhole camera information need only be a better approximation to the real emission profile than the assumption of a flat profile since the algorithm uses it as a first-order solution which is perturbed by the information from the diode arrays. The algorithm can also explicitly include the bean-shaped PBX-M vacuum vessel and the vignetting of some detectors by the pusher coil.