Development of multichord ion Doppler spectroscopy system for toroidal flow measurement of field-reversed configuration

K Araoka; T Asai; D Kobayashi; T Seki; T Takahashi; J Morelli; H Gota

doi:10.1063/5.0101878

Development of multichord ion Doppler spectroscopy system for toroidal flow measurement of field-reversed configuration

Rev Sci Instrum. 2022 Dec 1;93(12):123512. doi: 10.1063/5.0101878.

Authors

K Araoka¹, T Asai¹, D Kobayashi¹, T Seki¹, T Takahashi¹, J Morelli², H Gota³

Affiliations

¹ College of Science and Technology, Nihon University, Tokyo 101-8308, Japan.
² Department of Physics, Engineering Physics and Astronomy, Queen's University, Kingston, Ontario K7L 3N6, Canada.
³ TAE Technologies, Inc., Foothill Ranch, California 92610, USA.

PMID: 36586891
DOI: 10.1063/5.0101878

Abstract

A double-chord ion Doppler spectroscopy (IDS) system was developed to measure the ion temperature and flow velocity of field-reversed configuration (FRC) plasmas in the FRC amplification via a translation-collisional merging (FAT-CM) device. Adopting a Czerny-Turner mount monochromator and 16-channel photomultiplier tube array, the developed IDS system achieves high wavelength resolution and fast time response. In addition, two vertically aligned optical paths share the optical system up to the monochromator and then branch just before the detector, successfully reducing crosstalk to <1%. The Doppler broadening was measured at two measurement points in the FAT-CM device, simultaneously, and ion temperatures of ∼50 eV were measured. Toroidal spin-up from 7 to 15 km/s and a steady flow velocity of ∼10 km/s were estimated from the Doppler shift obtained by the developed system. The observation of the toroidal flow velocity and the spatial profile of the ion temperature of the FRC plasma in the FAT-CM device were realized. These spectroscopic diagnostic's double chord capabilities will aid in understanding and improving the FRC plasmas.