Time-resolved spectroscopy of nonequilibrium ionization in laser-produced plasmas

Miscellaneous · Fri Jan 01 00:00:00 EST 1988

OSTI ID:6938993

Marjoribanks, R S

The highly transient ionization characteristic of laser-produced plasmas at high energy densities has been investigated experimentally, using x-ray spectroscopy with time resolution of less than 20 ps. Spectroscopic diagnostics of plasma density and temperature were used, including line ratios, line profile broadening and continuum emission, to characterize the plasma conditions without relying immediately on ionization modeling. The experimentally measured plasma parameters were used as independent variables, driving an ionization code, as a test of ionization modeling, divorced from hydrodynamic calculations. Several state-of-the-art streak spectrographs, each recording a fiducial of the laser peak along with the time-resolved spectrum, characterized the laser heating of thin signature layers of different atomic numbers imbedded in plastic targets. A novel design of crystal spectrograph, with a conically curved crystal, was developed. Coupled with a streak camera, it provided high resolution ({lambda}/{Delta}{Lambda} > 1000) and a collection efficiency roughly 20-50 times that of planar crystal spectrographs, affording improved spectra for quantitative reduction and greater sensitivity for the diagnosis of weak emitters. Experimental results were compared to hydrocode and ionization code simulations, with poor agreement. The conclusions question the appropriateness of describing electron velocity distributions by a temperature parameter during the time of laser illumination and emphasis the importance of characterizing the distribution more generally.

• Research Organization: Rochester Univ., NY (USA)
• OSTI ID: 6938993
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
LASER-PRODUCED PLASMA
X-RAY SPECTROSCOPY
CALCULATION METHODS
DATA ANALYSIS
EXPERIMENTAL DATA
MEASURING INSTRUMENTS
MEASURING METHODS
PLASMA DENSITY
THEORETICAL DATA
DATA
INFORMATION
NUMERICAL DATA
PLASMA
SPECTROSCOPY
700101* - Fusion Energy- Plasma Research- Confinement
Heating
& Production