Line spread functions of blazed off-plane gratings operated in the Littrow mounting

Abstract

Abstract. Future soft x-ray (10 to 50 Å) spectroscopy missions require higher effective areas and resolutions to perform critical science that cannot be done by instruments on current missions. An x-ray grating spectrometer employing off-plane reflection gratings would be capable of meeting these performance criteria. Off-plane gratings with blazed groove facets operating in the Littrow mounting can be used to achieve excellent throughput into orders achieving high resolutions. We have fabricated two off-plane gratings with blazed groove profiles via a technique that uses commonly available microfabrication processes, is easily scaled for mass production, and yields gratings customized for a given mission architecture. Both fabricated gratings were tested in the Littrow mounting at the Max Planck Institute for Extraterrestrial Physics (MPE) PANTER x-ray test facility to assess their performance. The line spread functions of diffracted orders were measured, and a maximum resolution of 800 AE 20 is reported. In addition, we also observe evidence of a blaze effect from measurements of relative efficiencies of the diffracted orders.

A review on fabrication of blazed gratings

“…Wet etching is an important method used for the fabrication of blazed gratings [35,36]. Figure 10 schematically displays the etching process for an off-cut (111) silicon surface with resisting masks, where the dotted line represents the (111) crystal planes [98].…”

“…Thus, realising blazed gratings with small angles requires precise control over the accuracy of the groove parameters and groove shape errors, which poses significant challenges with respect to the fabrication process. Although several advancements in blazed grating manufacturing have been reported based on mechanical ruling [27][28][29], holographic ion beam etching (IBE) [30,31], electron beam lithography (EBL) [32][33][34], and wet etching [35,36], significant developments are still required to advance the manufacturing of high-quality gratings worldwide. This paper briefly reviews the recent progress in blazed grating manufacturing, and the advantages and disadvantages of these methods are also addressed to provide a better understanding of the technical development thus far, which is expected to promote improvements in blazed grating fabrication.…”

The Off-plane Grating Rocket Experiment (OGRE) system overview

“…Off-plane reflection gratings for soft X-ray applications are designed, manufactured, and tested at Penn State University. Many papers have been written on the fabrication and testing of these gratings, [8][9][10][11][12][13] and so in this paper we will focus on the design of the OGRE grating, the modules in which the gratings will be housed, and how these modules will be incorporated into the rocket. 6 OGRE's X-ray optic will be treated as 6 independent 60 • azimuth optics.…”

Optical design of the Off-plane Grating Rocket Experiment

“…To maximize diffraction efficiency, OGRE gratings will operate in the Littrow mount (α = β = δ). 19 For each 60 • azimuthal section of optic, α = β = 30 • . The angles in Fig.…”