Abstract

Inertial confinement fusion is one of the most active area of high energy density physics. To achieve nuclear fusion ignition and gain in laboratory is the major object. By the use of Shenguang II and prototype of Shenguan III laser facility physics about Holhraum and implosion were investigated experimently. SGIII laser facility is under constructing. It will equipped with 48 beams, and its output is designed as 60kJ in 1ns or 180kJ in 5ns. Ahead of that a prototype with 8 beams has been built to proof-test new engineering technology and assembly, its output is about 10kJ in 1ns with 0.35μm laser. Some experiments have been performed on it. Its pointing accuracy was tested as 30μ m, the radiation temperature is ~200eV in holhruams with 1mm in diameter and 1.7mm in length. In indirect drive implosion experiments with DD filled capsule 1.3×10⁸ of neutron yields were detected, and convergence of about 10 were obtained consistenly between nuclear diagnostics and atomic line spectral image. These experiments demonstrate that the ability of the prototype of SGIII laser facility is close to the designed level.

In recent years a series of radiation-related physics experiments have also been carried out on high power laser facilities at the Research Center of Laser Fusion in China, which include the x-ray opacity, the x-ray Thomson scattering and the x-ray emission spectrum.

The x-ray opacities of hot, dense plasmas have long been of interest due to their important and urgent need in studies of inertial confinement fusion (ICF), x-ray lasers and astrophysics. The x-ray opacity experiment of hot, dense plasmas has been conducted on the Shengguang II laser facility, in which two types of cavities (a conical cavity called a type I target, and a cylindrical cavity with foam baffles called a type II target ) were designed to convert the eight-beam laser into x-ray radiation to efficiently heat the sample and to prevent the sample from irradiation of the reflected laser and plasmas. The typical opacity results show that a sample temperature of about 95 eV has been reached using the type II target which is the highest obtained on the high power laser facility.

X-ray Thomson scattering is a potential tool of diagnosing dense plasma. In our work to develop the diagnostics of x-ray Thomson scattering, a HOPG crystal spectrometer with high efficiency and high spectral resolution has been set up. This spectrometer was used in the mosaic focusing mode to measure the spectrally resolved x-ray scattering of a radiatively heated carbon foam and the scattering spectrum was observed successfully also on the Shengguang II laser facility.

The K-shell emission x-ray spectra from the aluminum plasmas generated by interaction of the 120 TW, 30fs laser with aluminum targets have been measured by defocusing the laser beam. Laser energy-normalized intensity of the He-a line increases with the laser intensity approximately as a power law ε∝ILγ with the much smaller exponent of ɣ =0.062 compared with the previous experiments (ɣ =0.2~0.5) which is caused by the stronger radial thermal diffusivity in the target for the smaller laser spot. Laser-to-He-a line conversion efficiency of up to 1.9 × 10-3 and as high as about 3×1013 photons/ 2 π sr aluminum He-a line x-ray source have been achieved for each shot due to pre-plasma effect and relatively large laser spot and energy for each shot. The x-ray spectra as a function of the laser intensity have also been analyzed to get the electron temperature and density.

© 2009 IEEE