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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.

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The results of measurement and analysis of the decay of mirror-confined lithium hydride plasmas are reported. The plasmas are produced by laser irradiation of a solid LiH particle suspended at the center of a mimimum-B magnetic field. In the initial state, the ratio of the Li3+ energy to H+ energy is 7 to 1, the mean energy of lithium ions is about 2000 eV, and the electrons are cold. In the subsequent decay of the mirror-confined plasmas from 3×1013 to 1012 cm−3, the H+ lifetime is sufficiently shorter than the lifetime of the Li3+ ions so that the plasma evolves to a lithium plasma. The density decay is faster than classical but quiescent for the first 250 μsec. After that time, there are sudden increases in the plasma decay rate and in the rf emission at the central cyclotron frequency of lithium ions, interpreted as evidence of the onset of the drift cyclotron loss cone instability. The quiescent behavior is correlated with the observation of optical radiation from the plasma between 70 and 250 μsec. The plasma luminosity is interpreted as evidence for the creation of cold plasma by ionization of cold neutral reflux from the walls of the baseball coil. A quasi-linear Fokker–Planck calculation of the ion distributions and the growth and damping of the drift cyclotron loss cone mode yielded results consistent with an explanation of the quiescent decay as the suppression of the instability by the cold plasma.

A feedback-controlled particle suspension system has been developed for laser target plasma production in the LITE experiment. Suspension voltages derived from position and velocity (position derivative) feedback signals serve to capture an injected particle in high vacuum, damp the particle motion, and stably position the particle at the system null. In typical operations, LiH particles of ∼100-μm diameter, projected by a spring plunger into the suspension region, are captured and positioned at the system center in ⩽0.25 sec with a jitter of ⩽20 μm, less than 1/5 the particle diameter. With this system the precise particle positioning required for spherically symmetric plasma generation is obtained even with large particle sizes, and the feedback particle suspension system is incorporated as an integral part of the LITE experimental facility for studies of neutral injection buildup on a dense, mirror-confined, laser-produced target plasma.