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Gratings enable dispersive spectroscopy from the X-ray to the optical, and feature prominently in proposed flagships and SmallSats alike. The exacting performance requirements of these future missions necessitate assessing whether the present state-of-the-art in grating manufacture will limit spectrometer performance. In this work, we manufacture a 1.5 mm thick, 1000 nm period (1000 gr mm−1) flat grating using electron-beam lithography (EBL), a promising lithographic technique for patterning gratings for future astronomical observatories. We assess the limiting spectral resolution of this grating by interferometrically measuring the diffracted wavefronts produced in ± first order. Our measurements show this grating has a performance of at least R ∼ 14,600, and that our assessment is bounded by the error of our interferometric measurement. The impact of EBL stitching error on grating performance is quantified, and a path to measuring the period error of customized, curved gratings is presented. [ABSTRACT FROM AUTHOR]

We report on resolving power measurements of an X-ray reflection grating designed for use in an astronomical soft X-ray spectrograph. The grating was patterned via electron-beam lithography (EBL) to have fanned grooves to match the convergence of an illuminating beam. Grating measurements were conducted in an echelle-like mounting, which yields access to high diffraction orders in the soft X-ray bandpass (0.2–2.0 keV). By comparing the zeroth-order line-spread function to the telescope focus, we find evidence for minimal broadening (<1″) introduced by the figure of the grating. In addition, we fit for the spectral resolution (R = λ/Δλ) intrinsic to this grating using a Bayesian Markov Chain Monte Carlo approach. Using an ensemble fitting technique, we find that the grating resolution R exceeds 2200 (3σ lower bound). This current grating resolution meets the performance required for a notional soft X-ray grating spectroscopy mission measuring hot baryonic material in the extended halos of galaxies. Using ray-trace simulations, we identify a geometric aberration resulting from path length differences across the width of the grating as a limiting factor in assessing the resolution of these gratings and discuss methods for placing better constraints on the inherent resolution of X-ray astronomical reflection gratings fabricated using EBL. [ABSTRACT FROM AUTHOR]