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1.
Article in English | MEDLINE | ID: mdl-11102018

ABSTRACT

Measurements are presented of x-ray (>1.5 keV) and extreme ultraviolet (EUV, lambda=2-44 nm) emission from argon and krypton supersonic gas jets at room (T=300 K) and cryogenic (T=173 K) temperatures irradiated with constant energy (50 mJ), variable width laser pulses ranging from 100 fs to 10 ns. Two regimes of jet operation are explored: cluster formation (radius<100 nm) and droplet formation (radius>1 &mgr;m). The results for both clusters and droplets can be understood in terms of two time scales: a short time scale for optimal resonant absorption at the critical density layer in the expanding plasma, and a longer time scale for the plasma to drop below critical density.

2.
Phys Rev Lett ; 84(14): 3085-8, 2000 Apr 03.
Article in English | MEDLINE | ID: mdl-11019018

ABSTRACT

We report the observation of resonant self-trapping and enhanced laser-plasma heating resulting from propagation of high intensity Bessel beams in neutral gas. The enhancement in absorption and plasma heating is directly correlated to the spatial trapping of laser radiation.

3.
Article in English | MEDLINE | ID: mdl-11046482

ABSTRACT

The quasibound modes of an evolving plasma waveguide were investigated by using variably delayed end-injected and side-injected probe pulses. The use of these different coupling geometries allowed the probing of the waveguide's optical modes during two temporal regimes: early-time plasma channel development, characterized by leaky optical confinement, and later channel hydrodynamic expansion characterized by stronger confinement. The wave equation was solved to determine the available quasiguided optical modes and their confinement for experimentally measured electron density profiles. The guided intensity patterns and spectra measured at the waveguide exit were successfully explained in terms of these mode solutions. The spectrum of broadband end-coupled probe pulses was found to be unaffected by the guiding process, mainly because those modes which survived to the waveguide exit were well-bound, and for strongly bound fields, the transverse mode profiles are wavelength independent. By contrast, side coupling to the quasibound modes of the plasma waveguide was seen to be highly mode and frequency selective.

4.
Article in English | MEDLINE | ID: mdl-11138111

ABSTRACT

A high power, hollow Bessel beam (J5) is generated using an axicon and a phase plate in combination. The optical breakdown of a gas target and generation of a tubular plasma fiber with such a beam is realized. Hydrodynamic simulations of the hollow beam-plasma breakdown and heating are in reasonable agreement with interferometric measurements of the plasma time evolution.

5.
Phys Rev Lett ; 75(13): 2494-2497, 1995 Sep 25.
Article in English | MEDLINE | ID: mdl-10059326
7.
Phys Rev Lett ; 71(15): 2409-2412, 1993 Oct 11.
Article in English | MEDLINE | ID: mdl-10054673
9.
Phys Rev A ; 41(4): 2211-2214, 1990 Feb 15.
Article in English | MEDLINE | ID: mdl-9903336
10.
Phys Rev Lett ; 63(3): 338, 1989 Jul 17.
Article in English | MEDLINE | ID: mdl-10041046
11.
Phys Rev Lett ; 61(20): 2364-2367, 1988 Nov 14.
Article in English | MEDLINE | ID: mdl-10039093
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