Performance Testing of a Large-Format X-ray Reflection Grating Prototype for a Suborbital Rocket Payload

Abstract

The soft X-ray grating spectrometer on board the Off-plane Grating Rocket Experiment (OGRE) hopes to achieve the highest resolution soft X-ray spectrum of an astrophysical object when it is launched via suborbital rocket. Paramount to the success of the spectrometer are the performance of the [Formula: see text] reflection gratings populating its reflection grating assembly. To test current grating fabrication capabilities, a grating prototype for the payload was fabricated via electron-beam lithography at The Pennsylvania State University’s Materials Research Institute and was subsequently tested for performance at Max Planck Institute for Extraterrestrial Physics’ PANTER X-ray Test Facility. Bayesian modeling of the resulting data via Markov chain Monte Carlo (MCMC) sampling indicated that the grating achieved the OGRE single-grating resolution requirement of [Formula: see text] at the 94% confidence level. The resulting [Formula: see text] posterior probability distribution suggests that this confidence level is likely a conservative estimate though, since only a finite [Formula: see text] parameter space was sampled and the model could not constrain the upper bound of [Formula: see text] to less than infinity. Raytrace simulations of the tested system found that the observed data can be reproduced with a grating performing at [Formula: see text]. It is therefore postulated that the behavior of the obtained [Formula: see text] posterior probability distribution can be explained by a finite measurement limit of the system and not a finite limit on [Formula: see text]. Implications of these results and improvements to the test setup are discussed.

Silicon pore optics: a mature and adaptable x-ray mirror technology

“…The Off-plane Grating Rocket Experiment (OGRE) [17][18][19] is a soft X-ray spectroscopy suborbital rocket payload. OGRE aims to achieve a spectral resolution greater than 2000 within its 10 to 55 Å wavelength range.…”

A Comprehensive Line-Spread Function Error Budget for the Off-Plane Grating Rocket Experiment

“…The OGRE spectrometer is designed to utilize gratings with a radial groove profile and a groove period of 160 nm at a distance of 3300 mm from the hub of the converging grooves. 10 However, the processes used to manufacture these gratings will introduce errors that cause the manufactured groove pattern to deviate slightly from the idealized groove pattern. This deviation is expected to be a random process; therefore, the groove period at any given location on a grating will have a Gaussian distribution about its nominal value.…”

“…Results from this testing indicate that the OGRE grating prototype achieved a grooveinduced spectral resolution of R g > 4500 at the ∼ 94% confidence level. 10 However, this achieved spectral resolution was found to be limited by the measurement limit of the assembled spectrometer. Thus, the true grating-induced aberrations of the OGRE grating prototype could not be measured in this test and could have been higher than this limit.…”

A comprehensive line spread function error budget for the Off-plane Grating Rocket Experiment

“…The OGRE spectrometer is designed to utilize gratings with a radial groove profile and a groove period of 160 nm at a distance of 3300 mm from the hub of the converging grooves. 10 However, the processes used to manufacture these gratings will introduce errors that cause the manufactured groove pattern to deviate slightly Table 1 Errors induced into the LSF of the OGRE spectrometer from a 60-deg azimuthal section of the OGRE optic assembly. Since the optic will be treated as an assembled unit, the only errors to consider are its performance in the dispersion direction (measured as an FWHM) and the crossdispersion direction (measured as an HPD).…”

“…Results from this testing indicate that the OGRE grating prototype achieved a groove-induced spectral resolution of R g > 4500 at the ∼94% confidence level. 10 However, this achieved spectral resolution was found to be limited by the measurement limit of the assembled spectrometer. Thus, the true grating-induced aberrations of the OGRE grating prototype could not be measured in this test and could have been higher than this limit.…”