Plasma and Fusion Research

Volume 16, 2405019 (2021)

Regular Articles

Computer Tomography on Divertor Impurity Monitor for ITER with Minimizing Errors in a Logarithmic Scale
Hiroki NATSUME, Shin KAJITA1), Vladislav S. NEVEROV2), Radmir I. KHUSNUTDINOV2,3), Evgeny VESHCHEV4), Maarten DE BOCK4), Alexei R. POLEVOI4), Hirohiko TANAKA, Noriyasu OHNO, Hiroaki OGAWA5) and Sin-iti KITAZAWA5)
Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
1)
Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8603, Japan
2)
NRC Kurchatov Institute, Kurchatov sq. 1, 123182 Moscow, Russian Federation
3)
NRNU MEPhI, Kashirskoye sh. 31, 115409 Moscow, Russian Federation
4)
ITER Organization, 13115 St. Paul-lez-Durance, France
5)
Naka Fusion Institute, National Institutes for Quantum and Radiological Science and Technology (QST), Naka 311-0193, Japan
(Received 13 November 2020 / Accepted 6 January 2021 / Published 12 March 2021)

Abstract

The computer tomography for divertor impurity monitor, which measures plasma emissions in the divertor region, for ITER has been conducted using a ray-tracing technique. We have attempted four different solution methods for the inversion problem and compared the results. The solution methods which minimize errors in logarithmic scale had better performance than the methods which minimize errors in linear scale. This is likely due to the fact that the values in the emission profile vary in a wide range of orders of magnitude. The accuracy of the reconstruction has been investigated by changing discharge conditions and the number of field-of-views used. The deterioration in accuracy was most noticeable when the emission profile was reconstructed using only two field-of-views. In addition, the accuracy deteriorated, making the estimation more challenging, under discharge conditions with low emission intensity because of the wider range of emission intensity under such conditions.

Keywords

divertor impurity monitor, computer tomography, ray-tracing, inversion problem, tokamak diagnostic

DOI: 10.1585/pfr.16.2405019

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