Development of the poloidal Charge eXchange Recombination Spectroscopy system in Heliotron J

TL;DR

This paper presents the development and initial results of a poloidal Charge eXchange Recombination Spectroscopy system in Heliotron J, enabling detailed plasma rotation measurements with high spatial and temporal resolution.

Contribution

The paper introduces a novel CXRS system with high throughput and resolution for measuring poloidal plasma rotation in Heliotron J, including calibration and initial experimental results.

Findings

Electron diamagnetic rotation observed in NBI plasma

Ion diamagnetic rotation observed with ECH added

Radial electric field profile varies with heating method

Abstract

A Charge eXchange Recombination Spectroscopy (CXRS) system designed to measure the poloidal rotation velocity is developed in Heliotron J. The poloidal CXRS system measures the carbon emission line (C VI, n=8-7, 529.05nm) and the Doppler shift of the emission line provides the information of plasma rotation velocity. A high throughput photographic-lens monochromator (F/2.8) with 0.73nm/mm dispersion is adopted to achieve high rotation velocity and temporal resolution. Since two heating neutral beams from two tangential injectors (NBI) are used as the diagnostic beams, a wide observation range (0.26<r/a<0.92) is covered by 15 sightlines with a high spatial resolution(d<r/a> < 0.06) at peripheral region (r/a>0.6). The system design and the calibration method are presented. The initial results of poloidal rotation measurement show an electron diamagnetic rotation in an NBI heated plasma, while an ion diamagnetic rotation is observed when ECH is additionally applied. The evaluated radial electric field profile shows a positive Er at plasma core region in the ECH+NBI plasma, and a negative Er in the NBI heated plasma.