Temperature gradient scale length measurement: A high accuracy application of electron cyclotron emission without calibration

S Houshmandyar; Z J Yang; P E Phillips; W L Rowan; A E Hubbard; J E Rice; J W Hughes; S M Wolfe

doi:10.1063/1.4955297

Temperature gradient scale length measurement: A high accuracy application of electron cyclotron emission without calibration

Rev Sci Instrum. 2016 Nov;87(11):11E101. doi: 10.1063/1.4955297.

Authors

S Houshmandyar¹, Z J Yang², P E Phillips¹, W L Rowan¹, A E Hubbard³, J E Rice³, J W Hughes³, S M Wolfe³

Affiliations

¹ Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712, USA.
² Huazhong University of Science and Technology, Wuhan, Hubei 430074, China.
³ Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02129, USA.

PMID: 27910677
DOI: 10.1063/1.4955297

Abstract

Calibration is a crucial procedure in electron temperature (T_e) inference from a typical electron cyclotron emission (ECE) diagnostic on tokamaks. Although the calibration provides an important multiplying factor for an individual ECE channel, the parameter ΔT_e/T_e is independent of any calibration. Since an ECE channel measures the cyclotron emission for a particular flux surface, a non-perturbing change in toroidal magnetic field changes the view of that channel. Hence the calibration-free parameter is a measure of T_e gradient. B_T-jog technique is presented here which employs the parameter and the raw ECE signals for direct measurement of electron temperature gradient scale length.