Capability Studies of the Heliotron J Soft X-Ray Tomographic Diagnostic

Abstract

Imaging diagnostics offers magnetic free information for the plasma emissions and able to define plasma shape and position, impurity distribution, and magnetohydrodynamics (MHD) instabilities. The tomographic reconstruction is one of the powerful tools to analyze imaging diagnostic data. Tomography is employed for a wide range of plasma studies prominently for the soft X-ray (SX). SX tomography allows access to spatiotemporal transient phenomena resulting from the magnetohydrodynamics (MHD) activities, which are important for plasma confinement. Heliotron J (H-J) is an L/M = 1/4 helical axis Heliotron with a low magnetic shear configuration and with a bumpy poloidal plasma shape. An attempt for qualitative evaluation of the tomographic reconstruction capabilities for the Heliotron-J device was made. The tomographic reconstructions were made via Phillips -Tikhonov regularizations from the experimental data set at different locations in the time-space. The results suggests that the diagnostic needs to be improved for a high quality of image reconstruction and possible realization of magnetic axis shift, Shafranov Shift.

New tomographic reconstruction technique based on Laplacian eigenfunction

“…As a first benchmark, the nearorthogonal pattern of the LEF is constructed on the flux coordinate. The results are compared with other results obtained from least-squares approximation with the regularization of a Phillips-Tikhonov (PT)-type penalty function [12], which is the standard technique of tomographic reconstruction in fusion plasma for the experimental data of Heliotron J [13].…”