The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory is a stadium-sized facility that, when completed in 2008, will contain a 192-beam, 1.8-megajoule, 500-terawatt, ultraviolet laser system together with a 10-m-diam target chamber and room for 100 diagnostics. NIF is the world's largest and most energetic laser experimental system and will provide a scientific center to study inertial confinement fusion and matter at extreme energy densities and pressures. NIF's energetic laser beams will compress fusion targets to conditions required for thermonuclear burn, liberating more energy than required to initiate the fusion reactions. Other NIF experiments will study physical processes at temperatures approaching 108 K and 1011 bar, conditions that exist naturally only in the interior of stars and planets. NIF has completed the first phases of its laser commissioning program. The first four beams of NIF have generated 106 kJ in 23-ns pulses of infrared light and over 16 kJ in 3.5-ns pulses at the third harmonic (351 nm). NIF's target experimental systems are being commissioned and experiments have begun. This work provides a detailed look at the NIF laser systems, laser and optical performance, and results from recent laser commissioning shots. We follow this with a discussion of NIF's high-energy-density and inertial fusion experimental capabilities, the first experiments on NIF, and plans for future capabilities of this unique facility.
The National Ignition Facility, a center for the study of high energy density plasma physics and fusion energy ignition, is currently under construction at the Lawrence Livermore National Laboratory. The heart of the NIF is a frequency tripled, flashlamp-pumped Nd:glass laser system comprised of 192 independent laser beams. The laser system is capable of gen-erating output energies of 1.8MJ at 351nm and at peak powers of 500 TW in a flexible temporal pulse format. A descrip-tion of the NIF laser system and its major components is presented. We also discuss the manufacture of nearly 7500 pre-cision large optics required by the NIF including data on the manufactured optical quality vs. specification. In addition, we present results from an on-going program to improve the operational lifetime of optics exposed to high fluence in the 351-nm section of the laser.
An analog fiber-optic data link has been demonstrated for direct charge readout of wire chambers used in high energy particle detectors. The fiber link consists of a Nd:YAG laser carrier, a Mach-Zehnder external modulator, and a low-noise optical receiver. A charge pulse developed on a sensing wire flows directly into the electro-optic modulator with no preamplification. The substitution of passive modulators and fiber cable for active electronics and copper wire near large collider detectors has clear advantages with regard to radiation damage susceptibility, EMI immunity, physical size, and power consumption. Also, the modulator performance was unaffected for an applied one Tesla magnetic field. Reduction of noise contributions from the laser carrier and optical receiver and exploitation of the 'effective optical gain' properties of external modulators resulted in shot-noise-limited link sensitivity. Modulators were packaged with large termination resistorsenabling increased charge sensitivity with an increased system risetime tradeoff. Energy resolution of the fiber link was comparable to preamps conditional on large terminations and subsequent slow readout. For shorter risetimes required in timing diagnostics, small termination resulted in sensitivity 6.8 times inferior to preamps. Several potential improvements in sensitivity are discussed.
Measurements have been made on optical properties of Bicron BCF-91 waveshifting optical fiber. This fiber is proposed as a means of converting UV and blue light emitted from liquid scintillator when exposed to ionizing radiation. The conversion is accomplished by coiling the fiber in a reservoir filled with liquid scintillator and coated internally with reflective paint. UV and blue light is absorbed by the waveshifting dyes in the fiber and reemitted light is channeled into the core of the fiber and output to photo detectors. It has been proposed to outfit the hadron calorimeter sub-system of the GEM detector to be built at the Superconducting Super Collider with 800,000 separate liquid scintillator/waveshifting fiber cells. The measurements described in this work deal with the optical performance of the fiber: spectral emission, response as a function of input wavelengths, response as a function of irradiated length, propagation length and output numerical aperture. The theoretical response of an ideal calorimeter cell is studied based on the results of the measurements presented in this paper.
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