Streak camera receiver definition study

Detailed streak camera definition studies were made as a first step toward full flight qualification of a dual channel picosecond resolution streak camera receiver for the Geoscience Laser Altimeter and Ranging System (GLRS). The streak camera receiver requirements are discussed as they pertain specifically to the GLRS system, and estimates of the characteristics of the streak camera are given, based upon existing and near-term technological capabilities. Important problem areas are highlighted, and possible corresponding solutions are discussed

Electron-Temperature Measurement In Laser-Produced Plasmas By The Ratio Of Isoelectronic Line-Intensities

A class of spectroscopic line ratios has been adapted as a diagnostic of electron temperature from \u3c 100 eV to \u3e 1 keV. The diagnostic makes use of the ratio of line intensities from isoelectronic states of different elements in specially prepared targets. The diagnostic is simple to interpret, shows weak dependence on plasma density, requires only low to moderate spectral resolution, uses a single charge state, and can be adapted to minimize line reabsorption and wavelength coincidences with other spectral lines. We present theoretical and experimental results

Tracer Spectroscopy Diagnostics Of Doped Ablators In Inertial Confinement Fusion Experiments On Omega

A technique has been developed for studying the time-dependent, local physical conditions in ablator samples in an inertial confinement fusion(ICF)hohlraum environment. This technique involves backlit point-projection absorption spectroscopy of thin tracer layers buried in the interior of solid samples mounted on laser-driven hohlraums. It is shown how detailed view-factor, atomic, hydrodynamics, and radiation-transport modeling can be used to infer time-dependent physical conditions in the interiors of these samples from the observed absorption spectra. This modeling is applied to the results of an experimental campaign on the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] designed to compare radiation-wave velocities in doped and undoped ICF ablator materials

Observation of extremely strong shock waves in solids launched by petawatt laser heating

Understanding hydrodynamic phenomena driven by fast electron heating is important for a range of applications including fast electron collimation schemes for fast ignition and the production and study of hot, dense matter. In this work, detailed numerical simulations modelling the heating, hydrodynamic evolution, and extreme ultra-violet (XUV) emission in combination with experimental XUV images indicate shock waves of exceptional strength (200 Mbar) launched due to rapid heating of materials via a petawatt laser. We discuss in detail the production of synthetic XUV images and how they assist us in interpreting experimental XUV images captured at 256 eV using a multi-layer spherical mirror

Neutron detectors for fusion reaction-rate measurements

Fusion reactions in an inertial-confinement fusion (ICF) target filled with deuterium or a deuterium/tritium fuel release nearly monoenergetic neutrons. Because most the neutrons leave the compressed target without collision, they preserve reaction-rate information as they travel radially outward from their point of origin. Three fast, neutron detector techniques, each capable of measuring the fusion reaction-rate of ICF targets, have been demonstrated. The most advanced detector is based on the fast rise-time of a commercial plastic scintillator material (BC-422) which acts as a neutron-to-light converter. Signals, which are recorded with a fast optical streak camera, have a resolution of 25 ps. Good signals can be recorded for targets producing only 5 x 10{sup 7} DT neutrons. Two other detectors use knock-on collisions between neutrons and protons in a thin polyethylene (CH{sub 2}) converter. In one, the converter is placed in front of the photocathode of an x-ray streak camera. Recoil protons pass through the photocathode and knock out electrons which are accelerated and deflected to produce a signal. Resolutions < 25 ps are possible. In the other, the converter is placed in front of a microchannel plate (MCP) with a gated microstrip. Recoil protons eject electrons from the gold layer forming the microstrip. If a gate pulse is present, the signal is amplified. Present gate times are about 80 ps

Shock-induced shifts in the aluminum K photoabsorption edge

We present results of studies on shock-induced shifts in the K-photoabsorption edge of aluminum. Time-resolved x-ray spectroscopic measurements indicated maximum red shifts of ~7 eV for compressions of ~2.2 times normal density. The results are interpreted using hydrodynamic simulations which incorporated a new model for calculating the K-edge energy in a dense plasma

X-ray emission from high-Z spherical laser plasmas: Implications for plasma dynamics

Conversion of 351-nm laser light to soft x-rays has been studied using spherical gold targets irradiated at 5 x 10/sup 12/ - 4 x 10/sup 15/ W/cm/sup 2/. Spectra and time histories of sub-keV and M-band emission are presented. Results have been compared to detailed models (LASNEX) to better determine the dynamics of the plasma processes which lead to x-ray emission. 10 refs

Characterization of a subpicosecond x-ray streak camera for ultrashort laser-produced plasmas experiments

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