A. Sakumi

Heavy ion stripping by a highly-ionized laser plasma

Abstract Using projectiles of 225 keV/u 16O ions we experimentally investigated the scientific feasibility of highly ionized plasmas as strippers for low energy heavy ion beams. A fully ionized plasma was produced by irradiating a small pellet of lithium hydride with a Nd-glass laser. For the measurement of charge state distribution of the projectiles after passage through the plasma, we developed a time-resolved magnetic spectrograph. The intensity of 16O4+, 16O5+and 16O6+ behind the plasma target were simultaneously measured. From the measured distribution curve we have found that this plasma can yield higher charge states than conventional gaseous or solid strippers. Results of a numerical analysis are compared with the experimental data.

Stopping power measurement of 225 keV/u oxygen ions in laser-produced lithium hydride plasma

We experimentally investigated the stopping power of 225 keV/u oxygen ions in laser-produced lithium hydride (LiH) plasma. The plasma target was produced by irradiation of a small LiH pellet with a Q-switched Nd-glass laser. We have developed a system to measure the energy loss of projectile ions in the target with a time-of-flight method. We found that the measured stopping power in the plasma was more than three times higher than the one in cold matter. The effective charge of the projectiles determined from the measured stopping power was also higher than the one in cold matter.

A TOF system to measure the energy loss of low energy ions in a hot dense plasma

Abstract The energy loss of 180 keV/u 28Si ions in a plasma target was measured by using a TOF system. In order to produce the target plasma a Q-switched Nd-glass laser was focused onto a small LiH (Lithium Hydride) pellet. Spherical symmetry of the plasma expansion was checked by a high speed framing camera. Using this system we found that the energy loss of the ions in the plasma was larger than that in the cold equivalent by a factor of 3.5.

Heavy ion beam inertial confinement fusion studies in TIT

The HICF studies in Tokyo Institute of Technology are focused on beam-plasma interaction and acceleration of intense ion beams by inductive and RF methods. Two types of plasma targets have been developed by means of Z-pinch discharge and laser irradiation for the interaction experiments. Measurements of energy loss and charge exchange of heavy ions are conducted with those plasma targets. An inductive acceleration of light ions has been initiated with a Mendel type plasma gun connected to a magnetic core cavity. An RFQ linac generates an intense helium beam of sharp rise in order that a beam-induced plasma can be studied.

Energy loss and effective charge of low-energy oxygen ions in partially ionized plasma

This article reports on the interaction between slow ions and a partially ionized plasma. Temporal evolutions of energy loss and charge distribution of 2.4 MeV oxygen beams in the laser-induced polyethylene plasma were measured. The charge distribution showed strong stripping ability in the early phase of the plasma. Stopping power deduced from the experimental energy loss was 1.9 times larger than that for the solid. The effective charge of the projectile ion was estimated from the yields of 4+ and 6+ states. The peak value of the effective charge was 1.4 times larger than that of the solid. The stopping power equation given by Sigmund was extended for the partially ionized plasma and it could reproduce the measured energy loss.

Beam-plasma interaction experiments between low-energy heavy ions and laser plasmas

Interaction of /spl ap/0.2 MeV/u oxygen ions with plasmas has been studied using laser plasma targets. We have observed high charge stripping at an early rise time of CO/sub 2/ laser and enhanced energy loss in LiH plasma.