First results from a next-generation off-plane X-ray diffraction grating
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Future NASA X-ray spectroscopy missions will require high throughput, high resolving power grating spectrometers. Off-plane reflection gratings are capable of meeting the performance requirements needed to realize the scientific goals of these missions. We have identified a novel grating fabrication method that utilizes common lithographic and microfabrication techniques to produce the high fidelity groove profile necessary to achieve this performance. Application of this process has produced an initial pre-master that exhibits a radial (variable line spacing along the groove dimension), high density (> 6000 grooves/mm), laminar profile. This pre-master has been tested for diffraction efficiency at the BESSY II synchrotron light facility and diffracts up to 55 % of incident light into usable spectral orders. Furthermore, tests of spectral resolving power show that these gratings are capable of obtaining resolving powers well above 1300 (λ/Δλ) with limitations due to the test apparatus, not the gratings. Obtaining these results has provided confidence that this fabrication process is capable of producing off-plane reflection gratings for the next generation of X-ray observatories.
KeywordsX-ray spectroscopy Off-plane reflection gratings X-ray diffraction
This work was supported by NASA grants NNX12AF23G and NNX12AI16G. We would also like to acknowledge internal funding from the University of Iowa in support of Casey DeRoo. Special thanks are due to several people including Christian Laubis and his terrific support crew at PTB as well as James Carter and Bill Jones at MSFC for support of the resolution tests.
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