Andrew P. Rasmussen

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In the history of astronomy, major advances in our understanding of the Universe frequently arise from dramatic improvements in our ability to accurately measure astronomical quantities. Aided by rapid progress in information technology, current sky surveys are changing the way we view and study the Universe. Next-generation surveys will maintain this(More)
We report progress in using nanoimprint lithography to fabricate high fidelity blazed diffraction gratings. Anisotropically etched silicon gratings with 200 nm period and 7.5° blaze angle were successfully replicated onto 100 mm diameter wafers with subnanometer roughness and excellent profile conformity. Out-of-plane distortion induced by residual stress(More)
We present a spectrometer design based on a novel nanofabricated blazed X-ray transmission grating which is modeled to have superior efficiency. Here we outline a full instrument design proposed for Constellation-X which is expected to give resolving powers ~2000 (HEW). The spectrometer advantages include lower mass budget and smaller diffractor area, as(More)
Efficiency measurements of a grazing-incidence diffraction grating in the off-plane mount were performed using polarized synchrotron radiation. The grating had 5000 grooves/mm, an effective blaze angle of 14 degrees, and was gold coated. The efficiencies in the two polarization orientations (TM and TE) were measured in the 1.5-5.0 nm wavelength range and(More)
The Reflection Grating Spectrometer of the Constellation-X mission has two strong candidate configurations. The first configuration, the in-plane grating (IPG), is a set of reflection gratings similar to those flown on XMM-Newton and has grooves perpendicular to the direction of incident light. In the second configuration, the off-plane grating (OPG), the(More)
The RS CVn binary system HR 1099 was extensively observed by the XMM-Newton observatory in February 2000 as its first-light target. A total of 570 ks of exposure time was accumulated with the Reflection Grating Spectrometers (RGS). The integrated X-ray spectrum between 5–35Å is of unprecedented quality and shows numerous features attributed to transitions(More)
XMM is designed to provide sensitive, high resolution spectroscopy, on a wide variety of cosmic sources. We brieey review some issues related to high-resolution spectroscopy with the observatory, with emphasis on spectroscopy with the RGS. The most important spectroscopic plasma diagnostics accessible with the RGS are reviewed, after which w e discuss(More)
Despite the central role of posttraumatic stress disorder (PTSD) in international humanitarian aid work, there has been little examination of the measurement invariance of PTSD measures across culturally defined refugee subgroups. This leaves mental health workers in disaster settings with little to support inferences made using the results of standard(More)
The observation of the supernova remnant N132D by the scientific instruments on board the XMM-Newton satellite is presented. The X-rays from N132D are dispersed into a detailed line-rich spectrum using the Fe are identified. Images of the remnant, in narrow wavelength bands, produced by the European Photon Imaging Cameras reveal a complex spatial structure(More)
The amount and nature of dark energy (DE) can be tightly constrained by measuring the spatial correlation features and evolution of a sample of ∼ 100, 000 galaxy clusters over the redshift range 0 < z < ∼ 1.5. Such an X-ray survey will discover all collapsed structures with mass above 3.5 × 10 14 h −1 M ⊙ at redshifts z < 2 (i.e. the full range where such(More)