Hydrogenic Recycling in TFTR Discharges
Abstract
Particle recycling from the walls affects the fueling and charge exchange rates in tokamak plasmas. We study hydrogenic recycling in TFTR discharges from the DT experimental campaign. The DEGAS 3D neutrals code is used to model 2D profiles of the ionization and Balmer-α emission rates of the H, D, and T recycled from the limiter. Measured profiles of the Balmer-α emission rates are fitted by adjusting plasma scrape off length at the outer midplane, λ. This modeling provides the ionization rates in the scrape off plasma and within the last closed flux surface. The later is input in the TRANSP plasma analysis code for computing the recycling source rates and species conservation. We compare recycling characteristics of a variety of discharge types formed with various major radii, R_0, plasma currents, and degrees of limiter conditioning, both with and without lithium pellet injection. As R0 increases from 2.45 to 2.62m, the inferred λ decreases from several cm to less than one cm. The ratio of the ionization rate within the last closed flux surface to the average Balmer-α emission rate increases by a factor of approximately four. We compare particle and energy confinement times.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- November 1996
- Bibcode:
- 1996APS..DPP..6Q07B