Deep collisional-radiative modelling of edge turbulent electron density and temperature fluctuations using gas puff imaging on Alcator C-Mod

Measuring turbulent n_e and T_e fluctuations in the edge of magnetic confinement fusion devices is essential towards better diagnosing blobby transport and the overall applicability of edge plasma turbulence modelling. For this task, the gas puff imaging (GPI) diagnostic on Alcator C-Mod can capture visible light (587.6 nm) arising from the dynamic interaction of edge plasma turbulence with neutral helium. The Phantom camera used for GPI resolves HeI emission on a field-aligned 2-dimensional (R,Z)-grid with a spatial resolution of approximately 1-2 mm and temporal resolution of 2.5 µs. But these GPI measurements are only indirectly connected to n_e and T_e. For deeper analysis of the turbulent fluctuations contributing to the observed single line emission, the tenets of collisional radiative (CR) theory for atomic helium in the edge of high field tokamaks are reviewed, and we invert the CR model in a novel physics-informed numerical optimization framework to convert GPI signals into consistent experimental measurements of the turbulent n_e and T_e. This poster will present results from this computational analysis along with various time-dependent perturbations and spatial constraints on HeI (e.g. ionization, drifts) to evaluate their impact on interpreting plasma fluctuations.