Influence of plasma-neutral interactions on ALT-II pump limiter performance during NI heating at TEXTOR
Measurements of the particle exhaust by the ALT-II toroidal belt pump limiter during neutral beam injection (NI) on the TEXTOR tokamak have demonstrated the influence of plasma-neutral interactions on the particle exhaust efficiency of the pump limiter. During NI, the plasma flow into the pump limiter throat increases 3-5 times. This increase is due almost entirely to an increase in the plasma density, while the electron temperature remains nearly constant. Localised recycling at the neutraliser plates has been seen with both Langmuir probes and a fibre optic for viewing H(alpha) light from the neutraliser plate. To study the influence of plasma-neutral interactions on the removal efficiency, changes in the backconductance for neutral gas in the pump limiter throat, as a function of the incoming plasma conditions, have been studied by injecting helium gas into the plenum and monitoring the partial pressure. The results are compared with similar experiments on the ALT-I modular pump limiter and with simulations using the EIRENE code. Plasma-neutral interactions significantly influence the removal and exhaust efficiencies of the pump limiter for the range of throat plasma parameters encountered during NI, and affect the ability of pump limiters to meet particle and helium exhaust requirements in larger devices.
Bibliographic Reference: Article: European Physical Society, Vol. 14B (1990) Part III, p. 1447
Record Number: 199110268 / Last updated on: 1994-12-02
Original language: en
Available languages: en