The NIF environment is very complex leading to a large and non trivial radiation background. A shield surrounding the electronics is required to lower the neutron background to less than 1e7 n/cm{sup 2}. Moving electronics to behind the 6 foot-thick target bay wall is the best shield.

Vacuum Ultraviolet (VUV) photoionization mass spectrometry has been used to measure the evolution of chemical composition for two distinct organic aerosol types as they are passed through a thermodenuder at different temperatures. The two organic aerosol types considered are primary lubricating oil (LO) aerosol and secondary aerosol from the alpha-pinene + O3 reaction (alphaP). The evolution of the VUV mass spectra for the two aerosol types with temperature are observed to differ dramatically. For LO particles, the spectra exhibit distinct changes with temperature in which the lower m/z peaks, corresponding to compounds with higher vapor pressures, disappear more rapidly than the high m/z peaks. In contrast, the alphaP aerosol spectrum is essentially unchanged by temperature even though the particles experience significant mass loss due to evaporation. The variations in the LO spectra are found to be quantitatively in agreement with expectations from absorptive partitioning theory whereas the alphaP spectra suggest that the evaporation of alphaP derived aerosol appears to not be governed by partitioning theory. We postulate that this difference arises from the alphaP particles existing as in a glassy state instead of having the expected liquid-like behavior. To reconcile these observations with decades of aerosol growth measurements, which indicate …

Multilayer dielectric (MLD) diffraction gratings for Petawatt-class laser systems possess unique laser damage characteristics. Details of the shape of the grating lines and the concentration of absorbing impurities on the surface of the grating structures both have strong effects on laser damage threshold. It is known that electric field enhancement in the solid material comprising the grating lines varies directly with the linewidth and inversely with the line height for equivalent diffraction efficiency. Here, they present an overview of laser damage characteristics of MLD gratings, and describe a process for post-processing ion-beam etched grating lines using very dilute buffered hydrofluoric acid solutions. This process acts simultaneously to reduce grating linewidth and remove surface contaminants, thereby improving laser damage thresholds through two pathways.

The Savannah River Site has a mission to dissolve fissile materials and disposition them. The primary fissile material is plutonium dioxide (PuO{sub 2}). To support dissolution of these materials, the Savannah River National Laboratory (SRNL) designed and demonstrated a vacuum salt distillation (VSD) apparatus using both representative radioactive samples and non-radioactive simulant materials. Vacuum salt distillation, through the removal of chloride salts, increases the quantity of materials suitable for processing in the site's HB-Line Facility. Small-scale non-radioactive experiments at 900-950 C show that >99.8 wt % of the initial charge of chloride salt distilled from the sample boat with recovery of >99.8 wt % of the ceric oxide (CeO{sub 2}) - the surrogate for PuO{sub 2} - as a non-chloride bearing 'product'. Small-scale radioactive testing in a glovebox demonstrated the removal of sodium chloride (NaCl) and potassium chloride (KCl) from 13 PuO{sub 2} samples. Chloride concentrations were distilled from a starting concentration of 1.8-10.8 wt % to a final concentration <500 mg/kg chloride. Initial testing of a non-radioactive, full-scale production prototype is complete. A designed experiment evaluated the impact of distillation temperature, time at temperature, vacuum, product depth, and presence of a boat cover. Significant effort has been devoted to …

Localized, transient heating of materials using micro-scale, highly absorbing laser light has been used in many industries to anneal, melt and ablate material with high precision. Accurate modeling of the relative contributions of conductive, convective and radiative losses as a function of laser parameters is essential to optimizing micro-scale laser processing of materials. In bulk semi-transparent materials such as silicate glass melts, radiation transport is known to play a significantly larger role as the temperature increases. Conventionally, radiation is treated in the frequency-averaged diffusive limit (Rosseland approximation). However, the role and proper treatment of radiative processes under rapidly heated, high thermal gradient conditions, often created through laser-matter interactions, is at present not clear. Starting from the radiation transport equation for homogeneous, refractive lossy media, they derive the corresponding time-dependent multi-frequency diffusion equations. Zeroth and first moments of the transport equation couple the energy density, flux and pressure tensor. The system is closed by neglecting the temporal derivative of the flux and replacing the pressure tensor by its diagonal analogue. The radiation equations are coupled to a diffusion equation for the matter temperature. They are interested in modeling infrared laser heating of silica over sub-millimeter length scales, and at possibly rapid …

In this article we report on the properties of thin films of the full Heusler compound Co{sub 2}TiSn prepared by DC magnetron co-sputtering. Fully epitaxial, stoichiometric films were obtained by deposition on MgO (001) substrates at substrate temperatures above 600 C. The films are well ordered in the L2{sub 1} structure, and the Curie temperature exceeds slightly the bulk value. They show a significant, isotropic magnetoresistance and the resistivity becomes strongly anomalous in the paramagnetic state. The films are weakly ferrimagnetic, with nearly 1 {mu}{sub B} on the Co atoms, and a small antiparallel Ti moment, in agreement with theoretical expectations. From comparison of x-ray absorption spectra on the Co L{sub 3,2} edges, including circular and linear magnetic dichroism, with ab initio calculations of the x-ray absorption and circular dichroism spectra we infer that the electronic structure of Co{sub 2}TiSn has essentially non-localized character. Spectral features that have not been explained in detail before, are explained here in terms of the final state band structure.