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Observation of advanced particle removal rates in pump limiter simulation experiments

Conference ·
OSTI ID:7092384
The performance of particle removal schemes for density and impurity control in tokamaks and mirror machines depends strongly on the plasma parameters and local recycling near the plasma neutralizier plates and gas pumping ducts. The relationship between plasma density, electron temperature, ion energy and gas flow and particle removal rate through a pumping duct located near a plasma neutralizer plate has been experimentally investigated in the steady state plasma device PISCES. Results indicate that initially the particle removal by pumps at the end of the duct is proportional to the plasma flux to the plate. A nonlinear increase in the pumping rate occurs when the ionization mean free path for neutrals from the plate becomes less than the plasma radius. The transition from a transparent to an opaque plasma due to local ionization of the neutrals produced at the neutralizer plate greatly enhances the particle removal rate by recycling of the neutral gas as it flows away from the neutralizer plate or out of the pumping ducts. Parameters were varied to determine the importance of ballistic scattering of higher energy ions from the plate, but no effects were found in these experiments.
Research Organization:
California Univ., Los Angeles (USA). Center for Plasma Physics and Fusion Engineering
OSTI ID:
7092384
Report Number(s):
DOE/ER/52104-1; CONF-840520-14; ON: DE84014327
Country of Publication:
United States
Language:
English