Spectroscopic measurements of hydrogen ion temperature during divertor recombination

We explore the possibility of using the neutral H α spectral line profile to measure the ion temperature, T i , in a recombining plasma. Since the H α emissions due to recombination are larger than those due to other mechanisms, interference from nonrecombining regions contributing to the chord integrated data is insignificant. A Doppler and Stark broadened H α spectrum is simulated by the DEGAS 2 neutral transport code using assumed plasma conditions. The application of a simple fitting procedure to this spectrum yields an electron density, n e , and T i consistent with the assumed plasma parameters if the spectrum is dominated by recombination from a region of modest n e variation. General measurements of the ion temperature by H α spectroscopy appear feasible within the context of a model for the entire divertor plasma.