A kinetic model for KrF is presented that, by neglecting all but the most important kinetic processes, adequately describes the performance of electron-beam-pumped KrF lasers by a few, simple analytical expressions. The expression for the saturation intensity as a function of pump rate and gas composition is checked by measurements of gain saturation in both argon-rich and krypton-rich laser mixtures. The effects of fluorine burn-up are considered and are shown to impose a fundamental relationship between output fluence and efficiency of KrF laser amplifiers.

High-intensity laser beams propagating in a plasma become focused because the index of refraction depends on the relativistic mass of the electron and therefore is a function of the electric field strength through the electron velocity. Around the focus the laser field has such a high density of energy that electrons and ions are emitted owing to the nonlinear force arising from this field. The equations of motion for the electrons and the ions and the Maxwellian equations for the laser and plasma fields are solved under certain approximations. We calculate the maximal energy and the angular distribution of the emitted ions and compare the results with experimental data.

Experimental results are given on high-power ion beams (HPIB) generation in a vacuumspherical focusing diode with self-magnetic insulation, obtained from the nanosecond accelerator PARUS with 0.2-TW power and 60-ns pulse duration for a matched load. When the passive plasma source of the ions was used, the efficiency of the HPIB generationwas measured to be as high as 20% for 700-kV diode voltage and 10-kA/cm2 beam density in the focal plane.

The application of a coaxial plasma opening switch (POS) prior to the diode resultedin a factor-of-1.8 increase in the diode power in comparison with a match operation inthe absence of a POS.

The results of high-power ion beam (HPIB) generation and in the magnetically insulated diode (MID) installed on a 3 × 1010-W nanosecond accelerator are given. The possibility of efficient HPIB ballistic focusing with the use of the preformed plasma in the HPIB transport region was demonstrated.

Several new diagnostics (spring pendulum and acoustic probe) were used to measure the plasma ablation pressure during the impact of the HPIB with the target.

The highest degree of HPIB focusing attained during the experiments with spherical geometries of the diode electrodes was equal to 60. The ablation average pressures measured by the spring pendulum gave several kilobars for 8–10 kA/cm2 of HPIB density. The peak pressure measured by acoustic probes attained tens of kilobars for the same HPIB current amplitudes.

We investigated several examples of ion beam targets that utilize the energy efficiency of direct drive while optimizing on the symmetry requirements. Heavy-ion beams of charge state Z ≥ 3 at 5–10 GeV have ≲15–20 m bending radii with 3.5-T fields. Beams like these could be used with targets involving direct drive. Control of asymmetries in direct-drive ion beam targets depends on control of the effects of residual target asymmetries after an appropriate illumination scheme has been adopted. In this paper, we outline results of our investigations into ion beam target concepts in which the effects of residual asymmetries are ameliorated. The beams are placed according to our axially symmetric Gaussian-quadrature illumination scheme (Mark 1986). The targets survive the effects of residual asymmetries in our recent 2-D hydrodynamic simulations. We also briefly discuss the additional positive effects of polarized DT fuel on ion beam targets.

Results of novel experiments with laser-heated capillary targets are presented. In these experiments the interior of gold capillaries having a 200- or 700-μm 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 (λ = 0.53 μm) was employed, delivering 8-J energy in 3 ns. The experiments showed 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-μm diameter show uninhibited laser light propagation due to multireflections off the inner wall. In contrast, at the entrance of capillaries with a 200-μm inner diameter a plasma plug forms that absorbs most of the laser energy. In both cases significant energy transport was 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 ≊7% could be inferred for the conversion efficiency from laser light into X-ray radiation emitted from the rear opening of the capillary.

The increase in time-integrated divergence of a 1.7-MeV, 10-MA relativistic electron beam due to transport over 10 cm in a gas cell filled with 1 and 6 Torr of nitrogen was measured. The divergence was characterized by a multiple-pinhole beam sampling technique involving an aperture plate, an expansion region, and an attenuator plate followed by nylon radiochromic film. The divergence is determined by a fit of the measured deposition profile to response functions calculated using Monte Carlo coupled electronphoton transport codes. The initial value of 6.9° after the entrance foil is observed to increase to 12°. The errors in the measurement are quantified with Monte Carlo techniques. The response function fit gives a significantly better estimate of the divergence than a Gaussian fit.

The radiation hydrodynamics of a 125-μm thin carbon layer illuminated by thermal radiation of Trad = 200 eV temperature is studied within a multigroup radiation model. Whereas a major part of the incident photons deposit their energy by K-shell absorption close to the surface, soft photons below the K edge and hard photons (hv > 800 eV) penetrate deeper into the material and drive a heat wave with a sharp front. A nonablated mass fraction of 20% is accelerated with a hydrodynamic efficiency of 11%. About half of the incident radiation flux is reemitted by the heated carbon plasma. The heat front trajectory can be reproduced by the analytical heating wave model when effective opacity parameters corresponding to the most penetrating components are used.

Layered-targets experiments at 1.06-μm laser light have been performed in order to measure mass-ablation rate ṁ and ablation pressure Pa as a function of absorbed laser flux Ia and laser wavelength λL at irradiances of 1011-4.5 × 1012 W/cm2. The results can be put in the forms ṁ(g/cm2-s) ≈ 4.25 × 105[Ia(W/cm2)/1014]5/9(1 μm/λL)4/9 and Pa(Mbar) ≈ 20[Ia(W/cm2)/1014]7/9(1 μm/λL)2/9, which are consistent with the estimates obtained from a steady-state self-regulated model for plasma heating and with hydrodynamical simulations. Results show also a small lateral energy transport.