We present the methodology used to fabricate an X-ray reflection grating and describe a technique for grating replication. Further, we present the experimental procedure and results of a study to measure the diffraction efficiency of a replicated X-ray reflection grating in an extreme off-plane geometry. The blazed grating demonstrates a total diffraction efficiency of ∼60% from 0.34 to 1.2 keV at a grazing angle of ∼1.°5, with single-order efficiency ranging from ∼35% to 65% for energies within the blaze envelope. The diffraction efficiency of the grating measured relative to the reflectivity of the metal coating averages ∼90% above 0.34 keV. Data collected as a function of beam position on the grating indicate a relative variation in total efficiency of <1% rms across the grating surface.
The Water Recovery X-Ray Rocket (WRXR) was a suborbital rocket payload that was launched and recovered in April 2018. The WRXR flew two technologies being developed for future large x-ray missions: x-ray reflection gratings and a hybrid CMOS detector (HCD). The large-format replicated gratings on the WRXR were measured in ground calibrations to have absolute single-order diffraction efficiency of ∼60%, ∼50%, and ∼35% at CVI, OVII, and OVIII emission energies, respectively. The HCD was operated with ∼6 e − read noise and ∼88 eV energy resolution at 0.5 keV. The WRXR was also part of a two-payload campaign that successfully demonstrated NASA sounding rocket water recovery technology for science payloads. The primary instrument, a soft x-ray grating spectrometer, targeted diffuse emission from the Vela supernova remnant over a field-of-view >10 deg 2 . The flight data show that the detector was operational during flight and detected x-ray events from an on-board calibration source, but there was no definitive detection of x-ray events from Vela. Flight results are presented along with a discussion of factors that could have contributed to the null detection.
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