Andrew Rasmussen

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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)
UNLABELLED BACKGROUND, AIMS AND METHODS: Recent years have seen the introduction of web-based technologies such as the 'wiki', which is a webpage whose content can be edited in real time using a web browser. This article reviews the current state of knowledge about the use of wikis in education, and considers whether wiki technology has features that might(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)
A long 280 ks observation of the Seyfert 1 galaxy NGC 3783 with XMM-Newton is reported. We focus on the oxygen line complex between 17 and 24Å as measured with the RGS spectrometers. Accurate absorption column densities and emission line fluxes are obtained. We explore several options for the geometry and physical form of the emitting and absorbing gas. The(More)
Recent observations with the dispersive X-ray spectrometers aboard Chandra and Newton Observatory have begun to probe the properties of the X-ray intergalactic medium (IGM) at small redshifts. Using large quantities (∼950 ksec) of spectroscopic data acquired using the Reflection Grating Spectrometer (RGS) aboard Newton Observatory, we investigated the(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)