The concept of fast ignition with inertial confinement fusion (ICF) is a way to reduce the energy required for ignition and burn and to maximize the gain produced by a single implosion. Based on recent experimental findings at the PETAWATT laser at Lawrence Livermore National Laboratory, an intense proton beam to achieve fast ignition is proposed. It is produced by direct laser acceleration and focused onto the pellet from the rear side of an irradiated target and can be integrated into a hohlraum for indirect drive ICF.

Techniques have been developed to improve the unifoimity of the laser focal profile, to reduce the ablative Rayleigh-Taylor &stability, and to suppress the various laser-plasma instabilities. There are now three diiectdrive ignition target designs that utilize these techniques. Evaluation of these designs is still ongoing. Some of them may achieve the gains above 100 that are necessary for a fusion reactor. Two laser systems have been proposed that niay meet all of the requirements for a fusion reactor.

We have developed a hybrid Ti:sapphire-Nd:glass laser system that produces more than 1500 TW (1.5 PW) of peak power. The system produces 660 J of power in a compressed 440+/-20 fs pulse by use of 94-cm master diffraction gratings. Focusing to an irradiance of >7x10(20) W/cm (2) is achieved by use of a Cassegrainian focusing system employing a plasma mirror.

We have investigated the kinetics of excitation and lasing of the free radical SO by rotationally-resolved optical pumping near 250 nm with a continuously-tunable, narrow-line width KrF laser. Longitudinal photodissociation of SO2 by a 193-nm ArF excimer laser produced SO(X3Z-) concentrations close to 10l6 cm-3 over a 50-cm length. Pumping of SO(B3Z-) by the KrF laser occurred from the v" = 2 ground state vibrational level which was preferentially produced by photodissociation. The fraction of ground state population that could be excited to SO(B) was determined by measuring the saturation fluence for excitation as a function of buffer gas pressure and comparing with a simple model. Addition of a buffer gas increased excitation by nearly 30 times due to increased rotational mixing in the ground electronic state. Lasing was demonstrated on six new vibrational bands of fully-allowed SO(B-X) band in the region 262-315 nm. A small-signal gain coefficient of 0.11 cm-' and pulse energy of 1 1 pJ were achieved on the 270-nm SO-(B,v'=2-X,v"=5) laser transition. A full computational rate equation model of the excitation and lasing dynamics, including collisional rotational mixing, was developed. The A 3 n electronic state of SO was also investigated as a possible ultraviolet energy storage laser medium. Excitation of SO(A311,v'=5,6) near 250 nm was achieved after a time delay from photodissociation to allow for vibrational relaxation into SO(X,v"=O). Measurements of the radiative lifetime, deactivation rate, and saturation fluence, along with computation modeling, indicate that a storage laser based on the weak SO(A,v'=WX,v"=4) transition is not feasible with our production and excitation capabilities. Lasing on a direct-pumped single rotational transition of the SO(A,v'=5-+X,v"=l) band may be possible, but with very limited capacity to store energy.

A versatile, rapidly convergent, iterative algorithm is presented for the construction of kinoform phase plates for tailoring the far-field intensity distribution of laser beams. The method consists of repeated Fourier transforming between the near-field and the far-field planes with constraints imposed in each plane. For application to inertial confinement fusion, the converged far-field pattern contains more than 95% of the incident energy inside a desired region and is relatively insensitive to beam aberrations.