This research investigated the radiation cooling mechanism and formation of detached plasma in the case of gas injection in the D-module of GAMMA 10/PDX. In GAMMA 10/PDX, divertor simulation experiments have been started by using a divertor simulation experimental module (D-module). A V-shaped target made of tungsten has been installed in this module. In order to understand the effect of impurity injection into divertor simulation experimental module, we injected H 2 and Ar gases to the D-module and measured the heat flux and ion flux. According to the increase of gas injection, reduction of ion and heat fluxes have been observed. In the Ar injection experiments, H 2 gas has been injected simultaneously to examine the effect of molecular process on detached plasma formation. In this case, both the heat flux and ion flux are drastically reduced. These results indicate radiation cooling and formation of detached plasma due to gas injection. Simultaneous injection of noble gas and hydrogen gas showed the most effective results on detached plasma generation.
Gas fueling by supersonic molecular beam injection (SMBI) has been performed at the central-cell in GAMMA 10. The results of SMBI experiment with plenum pressure from 0.3 MPa to 2.0 MPa were obtained using a laval nozzle. The distribution of the emission intensity during SMBI was investigated by the 2-dimensional image captured by the fast camera as an index of the neutral transport. The experimental results indicates that the effect of the laval nozzle reduces the dispersion of injected hydrogen molecules in the peripheral region. In this paper, we also studied the line density at the central-cell (NLcc) and Hα emission intensity during SMBI. Comparison between SMBI and conventional gas puffing is also discussed from the view point of the fueling efficiency.
In the divertor simulation experiments in the GAMMA 10/PDX tandem mirror, pressure of the neutral gas was investigated by using a fast ionization gauge. The gauge was absolutely calibrated for hydrogen gas by using a capacitance manometer. Change of the gauge sensitivity due to the magnetic field of GAMMA 10/PDX was also evaluated. The typical gas pressure measured in detached plasma experiments was 0.1-10 Pa. The degree of plasma detachment determined from the reduction of heat flux was enhanced as the gas pressure increases. Rapid increase of the gas pressure under the plasma flow was also observed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.