Magnetic Field Confinement of Laser Irradiated Solid Particle Plasmas

Laser irradiation of a small solid particle of lithium hydride in vacuum results in the generation of a spherically symmetric, isolated, highly ionized plasma. Experimental studies with such plasmas formed within mirror and minimum-B magnetic field up to 8 kG show that the expanding plasma can be captured by the magnetic field and the expansion kinetic energy thermalized, in agreement with a simple magnetohydrodynamic model of the plasma-magnetic field interaction. In the experiments, the major plasma loss occurs through the mirror loss cones, and mass spectrometer measurements show rapid escape of the highly ionized lithium followed by a more gradual decay of hydrogen indicating a scattering mechanism for the plasma decay. Plasmas with densities of 3 × 1013 cm−3 at temperatures of 100 eV are confined for lifetimes up to 150 μsec in a minimum-B field compared with the 0.3 μsec lifetime associated with the free plasma expansion. Both the magnitude and the temperature dependence of the plasma decay from a minimum-B containment field are consistent with plasma loss by Coulomb collisional scattering into the magnetic field loss cones.