The electron temperature of a quiescent plasma in a metal discharge chamber, where the walls serve as the anode, can be raised by introducing a second anode consisting of 0.0025-cm-diam tungsten wires held at potentials as high as 100 V with respect to the walls. Hot electrons orbit the wires and return to the plasma. Cold electrons are absorbed. Smooth temperature variation, without introduction of noise, has been achieved between 0.5 and 4.0 eV.
Few-joule table-top lasers can generate pressures up to the 100 kbar range in solid materials by propagating a low-intensity beam through a transparent dielectric, which confines the ablation pressure, onto an ablation layer in contact with the material of interest. This technique has application in studies of material dynamic behavior and material processing. Development and application of physically based models of this process have lagged experiment. In this article the particulars of a detailed computational model incorporated into a two-dimensional radiationhydrodynamics code are presented. The model accounts for the initial absorption onto a metal surface, low-intensity photoionization absorption in neutral vapor, collisional ionization, recombination, dielectric breakdown, band gap collapse, electron conductivity, thermal transport, and constitutive properties of the materials. The model shows that most of the laser energy is absorbed in the dielectric tamper, not the ablator. Good agreement is found between simulated and measured pressure histories for materials irradiated with several tens of joules using a single-beam neodymium-glass laser at the Lawrence Livermore National Laboratory.
A compact Ar−N2 excitation transfer laser pumped by a coaxial electron gun is demonstrated. This laser emits a 40-ns, 300-kW pulse at a nominal repetition rate of 1 HZ. With 45 J of energy delivered to the electron gun, 12 mJ of laser output at 3577 Å is obtained. A 2.8% laser efficiency is estimated from simple electron deposition calculations, and the over-all electrical efficiency is estimated to be 0.03%. Because the stored energy needed in previously reported Ar−N2 lasers has been reduced by more than an order of magnitude while maintaining a comparable laser energy output, this device represents a significant step forward in the study of high-pressure electron-beam-pumped lasers.
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