Measurements of impurity mixing efficiency during massive gas injection in J-TEXT
- 4 February 2020
- journal article
- research article
- Published by IOP Publishing in Plasma Physics and Controlled Fusion
- Vol. 62 (4), 045003
- https://doi.org/10.1088/1361-6587/ab72e2
Abstract
Experiments of disruption mitigation with massive gas injection have been conducted in J-TEXT tokamak with various impurities (He, Ne, Ar and He&Ar (90%:10%) mixtures) injection. A 17-channels polarimeter-interferometer (POLARIS) has been used to analyze the evolution of the electron density profile during pre-TQ and TQ phases. Experiments show that both the impurity species and applied high voltage of the valve have an obvious influence on the impurities deposition location and electron density profile. Moreover, with the high spatial resolution of POLARIS, a rather accurate impurity mixing efficiency has been obtained. The results show that Ar, the high atomic number (high-Z) impurity, has high cooling efficiency and evident mitigation effects, but the mixing efficiency for Ar is only of order 5% - 8%. As for the low-Z impurity, He has fast propagation velocity and can reach high mixing efficiency, which is found to be of order 20% - 40%. The use of the mixtures of high-Z and low-Z impurities (He&Ar (90%:10%)) can combine the fast penetration of He and high cooling efficiency of Ar, and the mixing efficiency is up to the order 20% - 40%, improving the disruption mitigation efficiency and time response of disruption mitigation system.Keywords
Funding Information
- National Natural Science Foundation of China (51821005, 71762031, 11905077, 11575068, 11775089)
- China Postdoctoral Science Foundation (2019M652615)
- National Magnetic Confinement Fusion Science Program (2015GB104000, 2015GB111002)
- National Key R&D Program of China (2017YFE0302000, 2018YFE0309101)
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