Investigation of gain and hyperfine splitting in the niobium X-ray laser

Neon-like niobium X-ray lasers have been studied using both slab and thin-foil target geometries. Niobium foils of various lengths were irradiated from both sides with two beams of the frequency-doubled Nova laser system using a line focus. We looked for gain by measuring spectrally integrated line intensities at different plasma lengths. Gain was observed in four neon-like niobium lines corresponding to 3s–3p transitions. The line profile of theJ = 0–1 line ( = 145.9 ) shows splitting due to the hyperfine effect. Improved contrast in the hyperfine structure is observed as the plasma length is increased. Hyperfine splitting may be relevant to other 3s–3p transitions in neon-like niobium as well as other neon-like X-ray laser systems.     

First observation of lasing at 231 Å in neon-like nickel using the prepulse technique

We report lasing for the first time in nickel on the neon-like J=01, 3p3s transition at 231 Å as well as several weaker transitions including the J=2»1 lines at 298 Å and 304 Å. Amplification is seen only when the prepulse technique of using a low intensity prepulse before the main optical drive pulse is used to illuminate the nickel target. The prepulse technique is also shown to produce lasing in copper and dramatically improve the output of the germanium laser.     

The self-consistent mean spherical approximation for the one-component plasma

The consequences of choosing the adjustable hard-core diameter in the mean spherical approximation for the one-component plasma so as to achieve thermodynamic consistency between the energy and compressibility equations are investigated. Such a choice is found to be possible only for >8.5 and, although the resulting correlation functions are discontinuous, the height of the main peak in the static structure factor is remarkably accurate. Two especially noteworthy aspects of the thermodynamic results are that the compressibility equation is much more accurate than in any previous approximation free of input from computer simulations and that the nonstatic part of the internal energy has a ^1/4 dependence in the strong coupling limit in agreement with Monte Carlo data.     

The national ignition facility: path to ignition in the laboratory

The National Ignition Facility (NIF) is a 192-beam laser facility presently under construction at LLNL. When completed, NIF will be a 1.8-MJ, 500-TW ultraviolet laser system. Its missions are to obtain fusion ignition and to perform high energy density experiments in support of the US nuclear weapons stockpile. Four of the NIF beams have been commissioned to demonstrate laser performance and to commission the target area including target and beam alignment and laser timing. During this time, NIF demonstrated on a single-beam basis that it will meet its performance goals and demonstrated its precision and flexibility for pulse shaping, pointing, timing and beam conditioning. It also performed four important experiments for Inertial Confinement Fusion and High Energy Density Science. Presently, the project is installing production hardware to complete the project in 2009 with the goal to begin ignition experiments in 2010. An integrated plan has been developed including the NIF operations, user equipment such as diagnostics and cryogenic target capability, and experiments and calculations to meet this goal. This talk will provide NIF status, the plan to complete NIF, and the path to ignition.     

A semi-empirical modified hypernetted chain equation for the one-component plasma

The hypernetted chain (HNC) equation for the one-component plasma is corrected by including a single-parameter expression for the bridge graphs whose functional form ensures that the correct long-wavelength limit of the HNC results is retained. The parameter is chosen to improve the short-range behaviour.