A magnetic diagnostic suite for the Pegasus-III experiment.

Pegasus-III is an ultralow aspect ratio spherical tokamak providing a dedicated US experiment for comparative solenoid-free startup studies. A new magnetic diagnostic suite for equilibrium and low frequency (<200 kHz) magnetohydrodynamic mode analysis has been installed. These new diagnostics address the significant challenges of measuring magnetic field in a high noise environment with the majority constrained to fit in an 8 mm diagnostic gap on the high field side.

Spatial heterodyne spectroscopy for fast local magnetic field measurements of magnetized fusion plasmas.

A novel spectroscopy diagnostic for measuring internal magnetic fields in high temperature magnetized plasmas has been developed. It involves spectrally resolving the Balmer-α (656 nm) neutral beam radiation split by the motional Stark effect with a spatial heterodyne spectrometer (SHS). The unique combination of high optical throughput (3.

Ion temperature and rotation fluctuation measurements with ultra-fast charge exchange recombination spectroscopy (UF-CHERS) in the DIII-D tokamak.

An upgraded detector and several optimizations have significantly improved the Ultra-Fast Charge Exchange Recombination Spectroscopy (UF-CHERS) diagnostic sensitivity to ion temperature and parallel velocity fluctuations at turbulence relevant spatio-temporal scales. Normalized broadband ion temperature and parallel velocity fluctuations down to x̃x∼1% (x = T, v) and up to ∼450 kHz have been measured in a variety of plasmas. The multi-field nature of the CHERS technique also allows measurements of the cross-phase angles of the fluctuating fields.

Spatial heterodyne spectroscopy for high speed measurements of Stark split neutral beam emission in a high temperature plasma.

Measurement of electrostatic potential, or local electric field, turbulence is a critical missing component in validating nonlinear turbulence and transport simulations of fusion plasmas. A novel diagnostic is being developed for measuring local electric field fluctuations, , via high-speed measurements of the light emitted from a hydrogenic neutral beam. It exploits the proportionality of the spectral line splitting from the Motional Stark Effect to the total electric field experienced by the neutral atom at the excitation site.