Ion Rotational Velocity and Temperature Measurements on the Centrifugal Mirror Fusion Experiment

A multi-chord ion Doppler spectroscopy (IDS) diagnostic has been developed for the Centrifugal Mirror Fusion Experiment (CMFX) at the University of Maryland, College Park. The cylindrical CMFX plasma is set into azimuthal E x B rotation in a magnetic mirror. The resulting rotational velocity shear can suppress magnetohydrodynamic instabilities. Therefore, the measurement of ion rotational velocity profiles is critical to the characterization of the CMFX plasma. A fiber-optic array consisting of ten tangential viewing chords is set up to take ten simultaneous line-integrated spectroscopic measurements of the intensity, Doppler broadening, and Doppler shift of emission from native impurities and introduced impurity gases. Radial profiles of emissivity and rotational velocity are obtained via an Abel-like matrix inversion of the spectra. We present the current design of the IDS system and the inversion method, the calibration procedure, and spectroscopic measurements of impurities and of the Balmer-alpha and -beta lines of deuterium and hydrogen.

Acknowledgement: Work supported by the ARPA-E Grant No. DE-AR0001270.