Experimental determination of DT ion temperatures in laser fusion targets

Using the time-of-flight technique, energy distribution measurements were made of the fusion produced $alpha$ particles emitted from laser implosions of DT gas contained in glass microshells. The number of nuclear reactions was determined by an absolute measurement of both the number of $alpha$ particles and the number of neutrons. From the FWHM of the $alpha$ particle energy distributions, upper limits of the plasmas ion temperature have been inferred. By applying corrections for the broadening of the distribution due to the fuel and the pusher, ion temperatures of 2-3 keV have been calculated. These measurements constitute significant evidence that the implosions produced thermonuclear burn of the DT fuel. (auth

Crystal spectograph for imaging high-density targets

Laser fusion targets are being designed to achieve 100 times liquid hydrogen density using the LLL Argus laser. One method proposed for diagnosing the high density is to seed the D,T fuel with Ar gas and measure the spatial extent of the region emitting the Ar x-rays. A crystal spectrograph has been built to image in 1-D the hydrogen like (3.32 keV) and helium like (3.14 keV) Ar x-rays. The spectrograph was calibrated using an 8 ..mu..m source of Ag L/sub ..beta../ x-rays (3.15 keV) from an x-ray machine

Time resolved, sub-keV x-ray measurements using filtered x-ray diodes

Filtered x-ray diode detectors were used to measure absolute x-ray spectra below 1.5 keV at the Lawrence Livermore Laboratory Argus and Shiva laser facilities. We use K or L-edge filters in five and ten channel arrays to obtain energy resolution between 200 eV and 1.5 keV with channel FWHM's typically 200 eV. A channel with relatively uniform energy response is employed to independently measure the total x-ray energy up to 1.5 keV. Filter transmissions and detector sensitivities are measured absolutely to within +- 10% and +- 20% respectively at Lawrence Livermore Laboratory. With a FWHM time response that is less than 180 ps, the windowless diode detector developed for our experiments does not contribute significantly to system time response. Most of the fast oscilloscopes that we use for recording signals have a FWHM of 300 or 700 ps. We present, as examples, some ten channel x-ray spectral results obtained for disk irradiations at the Argus 1.06 micron laser facility

Sub-keV, subnanosecond measurements of x-ray spectra from laser-produced plasmas

As part of the effort to extend our x-ray diagnostic capabilities, we have made x-ray spectral measurements of laser-produced plasmas for photon energies down to 100 eV with a time response of 0.5 nsec. Fast, windowless x-ray diodes were used in conjunction with critical angle reflecting mirrors and thin filters for energy definition for two channels, 300 to 600 eV and 800 to 1300 eV. A third channel, using only an x-ray diode and filter, provided spectral information in the 100 to 300 eV region. Results from exploding pusher targets will be presented and compared with those of other diagnostic techniques and Lasnex calculations. Future expansion and modifications of the present system will be discussed

Pinhole imaging of laser-produced thermonuclear alpha particles

Results of pinhole images of thermonuclear alpha particles generated by exploding pusher targets in the Argus laser facility are reviewed. Recorded images indicate that the reactions occur within a 25 to 30 micron region with twelve micron resolution for ten micron pinholes and thirty micron resolution for twenty-five micron pinholes. These results are in good agreement with LASNEX computer predictions and are confirmed by Zone Plate imaging of the burn conducted by Natale M. Ceglio at LLL. Planned three-dimensional imaging of the burning D-T gas in the Shiva laser facility using seven micron pinholes is discussed. Higher yields (approximately 5 x 10/sup 10/ reactions) and three orthogonal images of the burn will provide a data base for analysis using an Algebraic Reconstruction Technique to provide a higher resolution (9 micron), three-dimensional view of the burn

Use of thin wall imaging in the diagnosis of laser heated hohlraums

High-Z, laser heated hohlraums can be made thick enough to contain thermal radiation, yet thin enough to let out x-rays >{approximately}6keV produced by hot, relatively dense blow-off plasma. The authors use such ``thin wall hohlraums`` to observe the physical location of hot, dense, laser produced hohlraum plasmas. This technique has allowed them to come to some understanding of laser transport/deposition, plasma stagnation and bulk plasma filling

Use of x-ray imaging on laser fusion experiments

A variety of x-ray imaging techniques have been used to study the absorption, transport and implosion characteristics of exploding pusher microsphere targets irradiated with 1.06 ..mu..m light. Multichannel grazing incidence reflection microscopy, zone plate coded imaging and spatially resolved x-ray spectroscopy have observed the thermal and suprathermal x-ray emission associated with these phenomena. A second generation of x-ray imaging devices, designed for forthcoming high density implosion experiments, including axisymmetric x-ray microscopes and 1- and 2-D crystal line imaging devices, will also be briefly discussed

Diagnostics of Shiva Nova produced high yield thermonuclear events

Experiments with the Shiva Nova laser facility which produce yield levels of scientific breakeven and above will result in neutron, x-ray and particle fluxes which will require specific attention to the survivability of diagnostic instrumentation. These yield levels will also allow the utilization of new diagnotics techniques which can provide detailed information on the state of the imploded fuel and pusher shells