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Theoretical aspects of producing laser plasmas are considered: the characteristics of the plasma, the transfer of laser energy to the material, and the different mechanisms of heating. The high power lasers required are described. Details are given of the arrangement used at Limeil in experiments to find evidence of nuclear fusion produced by a laser beam, and some results presented. Limiting factors in the experiments are discussed.

The analysis of LiH and LiD nanosecond — created laser plasmas reveals correlations between the various parameters of each plasma event. Relationships are found involving the energy spectra of the ion species, the target reflectivity, neutron production, hard and soft x‐ray emission, the electron temperature, and the input laser energy. Ion — expansion spectra of nonthermal origin are observed under the condition of high target reflectivity. High target reflectance is correlated to neutron and hard x‐ray production as well as an apparent decrease in electron thermal content for laser energies of 18–70 J. The ion — expansion spectra are obtained with mass and charge separation by the parallel electric and magnetic fields of a Thomson parabola ion analyzer. A novel feature of this device is the conversion of the analyzed ion beam to a visible image via an electron multiplier array, providing complete information on a single — shot basis. The Nd+3 glass laser used in these experiments delivers up to 70 J to ...

The effect of 10.6 μ radiation, in CO2 laser plasmas, on the spontaneous emission at 2.4 μ and the plasma impedance is studied by a phase-lock technique. The results reveal the influence that collisions between molecules in the primary laser cycle and excited states have on the properties of the discharge.

Measurements are presented of the electron energy distribution functions in CO 2 laser plasmas. Limitations of the diagnostic methods are discussed and their importance for the measurements is evaluated. The influence of the components of the laser mixture on the plasma characteristics is investigated; practically all distributions are found to be non-Maxwellian. The effect of the lasing action on the plasma is investigated with time-resolved probe and spectroscopic techniques. It is found that electron-electron interactions are insufficient to relax the distribution function during lasing. The modulation of electronically excited nitrogen levels indicates a strong coupling to the ground levels via the electron gas.

A series of high speed photographs are presented which show the crater and plasma formation when pulsed laser light is focussed onto the surface of a metal. Some features of the evaporation process are discussed. A spatially and time resolved spectral study of various laser plasmas was undertaken. We distinguish between three different modes of laser operation, i.e. normal mode (free running), semi-Q-switched mode and giant pulse mode. Various laser plumes were investigated as spectrochemical sources for quantitative analysis. For comparison, a series of aluminium alloy standards was analysed for copper content. The detection system employed a time resolution gating technique.

The effect of laser action, in CO2 laser plasmas, on the spontaneous emission in the visible spectral region is studied by means of a phase‐lock technique. The results reveal that direct collisions between molecules in the primary laser cycle and highly excited states have an important influence on the properties of the plasma.

Diagnostic measurements on uv photogenerated laser plasmas are presented. Ionization data obtained with an X‐band microwave interferometer show plasma density to be a function of both the gas mix and the irradiation source parameters. Electron density as a function of pressure is given for selected gases and mixtures. At atmospheric pressure the photoplasma density in the standard CO2 laser mix is found to be surprisingly low.

Brief discussions are given for each of the following areas of research covered during this report period: solid-state laser program, design analysis, component development, diagnostics, gas lasers, chemical lasers---the iodine laser, basic studies and advanced concepts, laser propagation, laser plasmas, laser fusion, isotope separation, and program resources. (MOW)

A spectroscopic technique for measuring time-varying gas kinetic temperatures with submicrosecond time resolution is described. The temperature in H 2 O discharges is determined from instantaneous OH emission spectra at ∼3064 A. The temperature rose linearly from 350 K to ∼2000 K at the end of a 4-μs 150-A current pulse through H 2 O. This temperature rise tends to switch off the gain and shorten the lsser pulse. Helium, when added, limited the temperature rise to ∼200 K and lengthened the laser pulse. Previous observations that the laser medinm becomes lossy after the end of the current pulse is shown to be due to the observed temperature rise. Models of pulsed lasers should include temperature, and hence time-dependent rate constants, to be accurate. Time-varying gas kinetic temperatures in pulsed CO 2 -N 2 -He laser plasmas, e.g., in TEA CO 2 lasers, could be determined by this technique using the 3371-A emission from the second positive system of nitrogen.