Development of off-plane gratings for WHIMex and IXO

Abstract

Future X-ray astronomical missions will need to address a number of important goals such as studying the dynamics of clusters of galaxies, determining how elements are created in the explosions of massive stars, and revealing most of the "normal" matter in the universe which is currently thought to be hidden in hot filaments of gas stretching between galaxies. In order to achieve these goals, spectrometers capable of high resolution and high throughput are necessary for the lowest X-ray energies, 0.3-1.0 keV. We present recent progress in the development of off-plane reflection grating technology for use on upcoming missions. Off-plane grating spectrometers consist of an array of gratings capable of reaching resolutions above 3000 (λ/∆λ). Concept designs have been made for the International X-ray Observatory X-ray Grating Spectrometer. More recently however, we have designed an Optics Module Assembly for WHIMex, an Explorer mission concept that incorporates a Wolter telescope, steering flats, and an array of gratings. This paper will discuss these designs and the application of off-plane arrays for the future.

Analytical alignment tolerances for off-plane reflection grating spectroscopy

“…2) along the ẑ axis and parallel to the xy plane. This distance is typical of X-ray grating spectrometer architectures recently studied by NASA [1,7]. A direction cosine diagram illustrating our assumptions is shown in Fig.…”

First results from a next-generation off-plane X-ray diffraction grating

“…Previous studies pointed toward the possibility of achieving this level for the off-plane configuration [McEntaffer et al(2004)]. Using these initial tests, conceptual designs for instruments onboard future NASA missions such as the Warm-Hot Intergalactic Medium Explorer (WHIMEx ) and IXO XGS [Bautz et al(2012), McEntaffer et al(2011] have used 40% diffraction efficiency as the basis for determining spectrometer properties. The assumption of obtaining this level flows down to the size of the array, the number of gratings, their size/mass/material, etc.…”

Fabrication of large-area and low mass critical-angle x-ray transmission gratings

“…In recent years the x-ray astronomy community has produced an impressive number of mission concepts for a soft x-ray spectrometer, either as a dedicated spectroscopy mission, 1,[5][6][7][8] or as an instrument on board a larger x-ray observatory. 7,[9][10][11][12][13] X-ray grating spectrometer dispersion provides much larger resolving power for soft x rays (<∼ 2 keV) than imaging microcalorimeters, which have superior resolution E/∆E for harder x rays. X-ray gratings come in two main flavors: Reflection 4,11,14,15 and transmission gratings.…”

“…7,[9][10][11][12][13] X-ray grating spectrometer dispersion provides much larger resolving power for soft x rays (<∼ 2 keV) than imaging microcalorimeters, which have superior resolution E/∆E for harder x rays. X-ray gratings come in two main flavors: Reflection 4,11,14,15 and transmission gratings. 3,10,16 Transmission gratings are very thin and offer a mass advantage, especially for large aperture x-ray telescopes.…”