Plasma and Fusion Research

Volume 11, 1302093 (2016)

Letters

Application of Tomographic Ion Doppler Spectroscopy to Merging Plasma Startup in the MAST Spherical Tokamak
Hiroshi TANABE, Takuma YAMADA1), Takenori WATANABE, Keii GI, Kazutake KADOWAKI, Michiaki INOMOTO, Ryota IMAZAWA2), Mikhail GRYAZNEVICH3), Rory SCANNELL3), Neil CONWAY3), Brendan CROWLEY3), Ken G MCCLEMENTS3), Ian FITZGERALD3), Clive MICHAEL3), James HARRISON3), Alex MEAKINS3), Nick HAWKES3), Thomas O'GORMAN3), Chio-Zong CHENG, Yasushi ONO and the MAST TEAM3)
Graduate School of Frontier Sciences, University of Tokyo, Tokyo 113-0032, Japan
1)
Faculty of Arts and Science, Kyushu University, Fukuoka 819-0395, Japan
2)
Japan Atomic Energy Agency, Ibaraki 311-0193, Japan
3)
CCFE, Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB, UK
(Received 9 January 2016 / Accepted 23 April 2016 / Published 10 June 2016)

Abstract

This paper describes recent advances in merging/reconnection experiments in MAST, namely tomographic ion Doppler spectroscopy capability from 2013 which solves the problem of the absence of ion temperature profile measurement during the solenoid-less startup. Providing 32 channel line-integrated spectra from 0.25 m < rtangential < 1.1 m are connected to a grating spectrometer with the focal length of 1.0 m and grating frequency of 1800 L/mm, and tomographic reconstruction is applied to measure local ion temperature profile. This system successfully contributes to the study of ion heating during merging/reconnection startup and revealed that magnetic reconnection mostly heats ions in the downstream region of outflow jet and also found its contribution to bulk electron heating as well as the localized heating at X point with the time scale of energy relaxation between ions and electrons.

Keywords

spherical tokamak, magnetic reconnection, acceleration and heating, energy conversion, solenoid-less startup, plasma diagnostics, ion Doppler spectroscopy and computer tomography

DOI: 10.1585/pfr.11.1302093

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