The low-frequency electric microfield distribution in a Coulomb plasma is calculated for various plasma parameters, from weak to strong Coulomb coupling and from zero to strong electron screening. Two methods of numerical calculations are employed: the adjustable-parameter exponential approximation and the Monte Carlo simulation. The results are represented by analytic fitting formulas suitable for applications.

Analysis is presented of K-shell spectra obtained from solid density plasmas produced by a high contrast (1O":l) subpicosecond laser pulse (0.5 pm) at 10'8-10'9 W/cm'. Stark broadening measurements of He-like and Li-like lines are used to infer the mean electron density at which emission takes place. The measurements indicate that there is an optimum condition to produce x-ray emission at solid density for a given isoelectronic sequence, and that the window of optimum conditions to obtain simultaneously the shortest and the brightest x-ray pulse at a given wavelength is relatively narrow. Lower intensity produces a short x-ray pulse but low brightness. The x-ray yield (and also the energy fraction in hot electrons) increases with the laser intensity, but above some laser intensity (IO's W/cm* for Al) the plasma is overdriven: during the expansion, the plasma is still hot enough to emit, so that emission occurs at lower density and lasts much longer. Energy transport measurements indicate that approximately 6% of the laser energy is coupled to the target at lOI* W/cm* (1% in thermal electrons with T,=O.6 keV and 5% in suprathermal electrons with The25 keV). At Zh*= 10's W pm2/cm2 (no prepulse) around 10" photons are emitted per laser shot, in 2n srd in cold K, radiation (2-9 A, depending on the target material) and up to 2X lo*' photons are obtained in 271. srd with the unresolved transition array (UTA) emission from the Ta target. 0 1995 American Institute of Physics.

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A Monte Carlo scheme to sample the screening potential H(r) of Yukawa plasmas notably at short distances is presented. This scheme is based on an importance sampling technique. Comparisons with former results for the Coulombic one-component plasma are given. Our Monte Carlo simulations yield an accurate estimate of H(r) as well for short range and long range interparticle distances.