Dynamics of a microcapillary discharge plasma using a soft x-ray laser backlighter
We have used the new technique of soft x-ray laser shadowgraphy in combination with traditional plasma emission spectroscopy and theoretical modeling to study the dynamics of a plasma column created by a discharge through a 380 {mu}m diameter evacuated microcapillary. The transient microcapillary plasma was imaged with high-spatial and temporal resolution using a tabletop discharge pumped 46.9-nm laser backlighter. Model computations show that the sharp boundary observed between the absorbent and transparent regions of the shadowgrams is defined by the spatial distribution of weakly ionized ions that are strongly photoionized by the probe laser. The plasma was observed to rapidly evolve from an initially nonuniform distribution into a column with good azimuthal symmetry and minimum density on axis [computed electron density on axis n{sub e}=(1--3)x10{sup 19}cm{sup -3}]. This concave electron density profile constitutes a plasma waveguide for laser radiation. Heated solely by Joule dissipation from relatively small excitation currents (1.5 kA), this dense plasma reaches substantial electron temperatures of T{sub e}=15--20eV as a result of the absence of significant hydrodynamic losses and reduced radiation losses caused by large spectral line opacities. The results illustrate the potential of tabletop soft x-ray lasers as a new plasma diagnostic tool.
- Sponsoring Organization:
- (US)
- OSTI ID:
- 40205406
- Journal Information:
- Physical Review E, Vol. 62, Issue 5; Other Information: Othernumber: PLEEE8000062000005007209000001; 088010PRE; PBD: Nov 2000; ISSN 1063-651X
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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