Experiments with laser-irradiated cylindrical targets

Abstract

Results of novel experiments with laser-heated capillary targets are presented. In these experiments the interior of gold capillaries having a 200-or 700-jixm inner diameter and a 2-12-mm length was axially irradiated by injection of the laser energy through one of the end openings. A frequency-doubled Nd:glass laser (X = 0.53 /tin) was employed, delivering 8-J energy in 3 ns. The experiments showed no significant backreflection of laser light. Depending on the capillary diameter and length, most of the laser energy is either transmitted or absorbed inside the capillary. The transmission of laser light was measured as a function of capillary length and found to be in good agreement with the predictions of a simple theoretical model. Two extreme cases could be identified. Capillaries with a 700-/xm diameter show uninhibited laser light propagation due to multireflections off the inner wall. In contrast, at the entrance of capillaries with a 200-/nm inner diameter a plasma plug forms that absorbs most of the laser energy. In both cases significant energy transport was observed to occur in the axial direction. A stable and strongly radiating plasma column is formed along the capillary axis by the collision of the radially imploding plasma. During the collision, part of the hydrodynamic energy of the plasma is converted into radiative energy. In a special case-a lower limit of = 7 % could be inferred for the conversion efficiency from laser light into X-ray radiation emitted from the rear opening of the capillary.

Plane thermonuclear detonation waves initiated by proton beams and quasi-one-dimensional model of fast ignition

“…For the first time such type of target was suggested by Pashinin & Prokhorov (1972) for compression of a gaseous deuterium by laser pulses. Note that the target was experimentally studied by Stöckl & Tsakiris (1991).…”

Time evolution of colliding laser produced magnesium plasmas investigated using a pinhole camera

“…Previous experiments have incorporated a variety of beam-target configurations including dual beam/parallel planar targets, 25 split beam/ single planar target, 26 split beam/target slabs placed orthogonally, 22 and single beam/internally irradiated microtubes. 27 Very little has been done to image the spatial and temporal progression of colliding laser produced plasmas at very early times and especially in the XUV region. In this article, we report an experimental approach in which a gated XUV camera is used to image the expansion dynamics of colliding laser produced magnesium plasmas in vacuum.…”

<title>Soft x-ray radiation from plasma and microcapillary waveguides</title>

“…Hollow density profile was created in the plasma, which was produced by ablation of the rnicrocapillary wall8 with a pump laser beam (about ablation process see Ref. 8). The laser beam also generates the proper plasma conditions in the core of the microcapillary plasma.…”