#### Abstract

A powerful new approach to the study of particle transport and helium ash confinement in high-temperature fusion plasmas is demonstrated by charge-exchange recombination spectroscopy of ${\mathrm{He}}^{++}$ in Ohmically heated PDX discharges. Time- and space-resolved measurements of ${\mathrm{He}}^{++}$ density following a short puff of helium gas into the plasma edge are fitted with use of a diffusive/convective transport model with coefficients $D=(2.1\mathrm{}\pm 0.9)\times {10}^{4}$ ${\mathrm{cm}}^{2}$ ${\mathrm{s}}^{-1\mathrm{}}$ and $\frac{v\left(r\right)\mathrm{}}{D}=\frac{(0.8\mathrm{}\pm 0.3)\partial \left(\mathrm{ln}{n}_{e}\right)}{\partial r}$.

DOI: http://dx.doi.org/10.1103/PhysRevLett.52.530

- Received 9 November 1983
- Published in the issue dated 13 February 1984

© 1984 The American Physical Society