Local Neutral Density Enhancement by Streaming Neutral Gas Injection

Abstract

An array of nozzles arranged in a bicycle-wheel spoke pattern designed to create a region of high neutral gas density in an H À ion source was tested for its capability to generate a pressure gradient in a vacuum chamber. An experimental setup was designed and built to measure the local pressure around the nozzle array. The two-dimensional direct simulation Monte Carlo (DSMC) technique was employed to simulate the local pressure distribution around the nozzles and to compare the results with the measurements. Pressure measurements and DSMC simulations showed that the streaming neutral gas injection (SNGI) technique was capable of increasing the local pressure to 200% when the ambient pressure was 3:0 Â 10 À2 Pa. At higher ambient pressures, the enhancement factor decreased to 58% when the ambient was 2.8 Pa. A sloshing-type SNGI was also designed and the highest enhancement was 87% at an ambient pressure of 2:6 Â 10 À1 Pa.

Ion propagation in an aluminum hollow cylinder target laser ion source

“…Since cooling down of the plasma will lead to lower ion and electron energies, this will increase the probability of molecules, clusters and also negative ion formation. 21,22) To understand the fundamental properties of spatially confining an expanding plasma, the geometry of the target was designed to have a hollow cylindrical shape with the plasma ignited inside the conduit. 23) In the present work, an aluminum hollow cylinder target is utilized in the laser ion source and the experimental results are presented.…”