Experiments with laser-irradiated cylindrical targets
Results of novel experiments with laser-heated capillary targets are presented. In these experiments the interior of gold capillaries having a 200 micron or 700 micron 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 (wavelength 0.53 micron) was employed, delivering 8 J energy in 3 ns. The experiments show 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 micron diameter show uninhibited laser light propagation due to multireflections off the inner wall. In contrast, at the entrance of capillaries with a 200 micron inner diameter a plasma plug forms that absorbs most of the laser energy. In both cases significant energy transport is 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 approximately 7% could be inferred for the conversion efficiency from laser light into X-ray radiation emitted from the rear opening of the capillary.
Bibliographic Reference: Article: Laser and Particle Beams, Vol. 9 (1991) No. 3, pp. 725-747
Record Number: 199210155 / Last updated on: 1994-12-02
Original language: en
Available languages: en