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Laboratory tests of stellar interior opacity models

Bailey, James E.

The internal structure of stars depends on the radiative opacity of the stellar matter. However, opacity models have never been experimentally tested at the conditions that exist inside stars. Experiments at the Sandia Z facility are underway to measure the x-ray transmission of iron, an important stellar constituent, at temperature and density high enough to evaluate the physical underpinnings of stellar opacity models. Initial experiments provided information on the charge state distribution and the energy level structure for the iron ions that exist at the solar radiation/convection boundary. Data analysis and new experiments at higher densities and temperatures will be described.

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TYPE Conference YEAR 2010
OSTI

Quantitative extraction of spectral line intensities and widths from x-ray spectra recorded with gated microchannel plate detectors

Review of Scientific Instruments

Dunham, Greg; Bailey, James E.; Rochau, G.A.; Lake, Patrick W.; Nielsen-Weber, L.B.

Plasma spectroscopy requires determination of spectral line intensities and widths. At Sandia National Laboratories Z facility we use elliptical crystal spectrometers equipped with gated microchannel plate detectors to record time and space resolved spectra. We collect a large volume of data typically consisting of five to six snapshots in time and five to ten spectral lines with 30 spatial elements per frame, totaling to more than 900 measurements per experiment. This large volume of data requires efficiency in processing. We have addressed this challenge by using a line fitting routine to automatically fit each spectrum using assumed line profiles and taking into account photoelectron statistics to efficiently extract line intensities and widths with uncertainties. We verified that the random data noise obeys Poisson statistics. Rescale factors for converting film exposure to effective counts required for understanding the photoelectron statistics are presented. An example of the application of these results to the analysis of spectra recorded in Z experiments is presented. © 2007 American Institute of Physics.

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TYPE Journal Article YEAR 2007
ScopusOSTIDOI

Twin-elliptical-crystal time- and space-resolved soft x-ray spectrometer

Review of Scientific Instruments

Lake, Patrick W.; Bailey, James E.; Rochau, G.A.; Gard, P.; Petmecky, D.; Bump, M.; Joseph, N.R.; Moore, T.C.; Nielsen-Weber, L.B.

Elliptical crystal spectrometers equipped with time-gated microchannel plate (MCP) detectors provide time-, space-, and spectrally resolved data. A common problem is that the number of time resolution elements is limited by the number of MCP frames. The number of frames that fit on a given MCP is limited by the image size and the alignment tolerance. At the Z facility these problems have been addressed with twin-elliptical-crystal spectrometers. Using two crystals and detectors doubles the number of frames available. This enables measurements with ∼350 ps time resolution while still recording data from an ∼4 ns wide time window. Alternatively, the twin crystal design allows simultaneous measurements with different crystals to investigate different spectral regimes. © 2006 American Institute of Physics.

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TYPE Conference YEAR 2006
ScopusOSTI
Results 151–175 of 212
Results 151–175 of 212