Thorman Alex, Michael Clive, Howard John, Victor Brian, Holcomb Chris, Allen Steve
Plasma Research Laboratory, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200, Australia.
Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
Rev Sci Instrum. 2018 Oct;89(10):10D124. doi: 10.1063/1.5038969.
A motional Stark effect (MSE) imaging diagnostic was benchmarked against existing conventional MSE polarimeters on the DIII-D tokamak and delivered new capabilities for measuring the magnetic pitch angle from 2 neutral beams and on the high field side of DIII-D. Line integration across flux surfaces was considerable for the radial view utilised; nevertheless, the imaging MSE measurements from both beams were self-consistent and in close agreement with conventional MSE measurements. The ferroelectric liquid crystal waveplate used in the imaging polarimeter was discovered to have spatially non-uniform retardance; hence, it is necessary for the calibration source to replicate the ray paths of the neutral beam emission through the optical system.
