Preliminary design of the soft x-ray array tomographic diagnostic system for Korea Superconducting Tokamak Advanced Research (KSTAR) plasmas

Abstract

Analyses of x-ray (SXR) emission from tokamak plasmas provide valuable information about magnetohydrodynamics activities and transport phenomena. In this study, design and optimization of the SXR detector arrays were performed for the KSTAR (Korea superconducting tokamak advanced research) device. Geometrical arrangement of the array system was made by coverage mapping and tomographic reconstruction tests. The space-time tomography algorithm was developed for KSTAR-like plasmas using the fast maximum entropy method combined with singular value decomposition. Spatial setup of the components in each detector array was determined and optimized by geometrical calculation. A curved beryllium window and a developed cooling system will be mounted on the detector arrays. Due to the existence of the complex structures between outer vessel and passive stabilizers, each array is designed to be miniaturized. Hardware-optimization of the array system was cross-checked with the tomographic test results.

Modified Phillips–Tikhonov regularization for plasma tomography

“…While regularization, the mean-squared error e 2 jf À Wgj 2 =M and the Laplacian r 2 gðx; yÞ should be minimized [7,8]. This task is equivalent to minimizing the functional [5] J ajLgj 2 þ jf À…”

“…The X-ray tomography also allows access to the spatio-temporal transient phenomena due to MHD activities [4], which play an important role in plasma confinement. The problem consists of determining the distribution of the soft Xray emissivity in a poloidal cross-section of the plasma from a number of line-integrated measurements [5]. A set of pinhole 'cameras', each having several X-ray detectors, is placed in a poloidal plane at the same toroidal position of the vacuum vessel.…”

An optimization method for ITER radial x-ray camera line-of-sight design basing on Bayesian uncertainty analysis

“…Up to now, the design of LOS is still typically relied upon experiential judgment from experimental personnel or has been determined through a limited number of phantom tests [2,14]. Such design approaches might be lack comprehensiveness and rigor.…”

Tomography-based spatial uniformity diagnostics for meter-sized plasmas

“…This technique has been well-established and actively used in medicine [11] and astronomy fields [12,13]. Tomography technique has been also employed for fusion plasma diagnostics, particularly cross-sectional x-ray imaging [14][15][16][17][18][19] and bolometers [20,21].…”