Abstract: A program is underway at the Naval Research Laboratory (NRL) to develop a high-resolution spectrometer for the study of astrophysical sources at EUV/soft X-ray wavelengths. The spectrometer design is simple in that the sole optic is a multilayer-coated spherical grating or mosaic of co-aligned gratings used at near-normal incidence, allowing large effective collecting area without the strict tolerance requirements of grazing incidence optics. Therefore, both high resolution and high throughput can be obtained over several selected narrow bandpasses. We present efficiency and resolving power measurements of spherical gratings which have parameters similar to that intended for our flight instrument. Two gratings were replicated from the same ruled master and then coated with a multilayer of molybdenum and silicon. A third sister grating was used as a control and overcoated with gold.!18
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