ABSTRACT
The implosion efficiency in inertial confinement fusion depends on the degree of stagnated fuel compression, density uniformity, sphericity, and minimum residual kinetic energy achieved. Compton scattering-mediated 50-200 keV x-ray radiographs of indirect-drive cryogenic implosions at the National Ignition Facility capture the dynamic evolution of the fuel as it goes through peak compression, revealing low-mode 3D nonuniformities and thicker fuel with lower peak density than simulated. By differencing two radiographs taken at different times during the same implosion, we also measure the residual kinetic energy not transferred to the hot spot and quantify its impact on the implosion performance.
ABSTRACT
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.
ABSTRACT
We demonstrate temporal shaping of 0.35-microm-wavelength pulses produced by a third-harmonic conversion of the output from the Nova Nd:phosphate glass-laser amplifier system for use in inertial confinement fusion experiments. We describe the computer models used to calculate the pulse shape that is required as the input to the amplifier system, the experimental apparatus used to produce these pulses, and the high-power 0.35-microm shaped pulses produced in recent experiments.
ABSTRACT
High-powered glass-laser systems with multiple beams, frequency-conversion capabilities, and pulseshaping flexibility have made numerous contributions to the understanding of inertial confinement fusion and related laser-plasma interactions. The Nova laser at Lawrence Livermore National Laboratory is the largest such laser facility. We have made improvements to the Nova amplifier system that permit increased power and energy output. We summarize the nonlinear effects that now limit Nova's performance and discuss power and energy produced at 1.05-, 0.53-, and 0.35-microm wavelengths, including the results with pulses temporally shaped to improve inertial confinement fusion target performance.
ABSTRACT
To provide high-energy, high-power beams at short wavelengths for inertial-confinement fusion experiments, we routinely convert the 1.05-microm output of the Nova, Nd:phosphate-glass, laser system to its second- or third-harmonic wavelength. We describe the design and performance of the 3 x 3 arrays of potassium dihydrogen phosphate crystal plates used for type-II-type-II phase-matched harmonic conversion of the Nova 0.74-m diameter beams. We also describe an alternate type-I-type-II phasematching configuration that improves third-harmonic conversion efficiency. These arrays provide conversion of a Nova beam of up to 75% to the second harmonic and of up to 70% to the third harmonic.
