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RAISE
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 >250 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 Rsub>g</sub>(λ∕Δλ)>4500 at the 94% confidence level. The resulting Rsub>g</sub> posterior probability distribution suggests that this confidence level is likely a conservative estimate though, since only a finite Rsub>g</sub> parameter space was sampled and the model could not constrain the upper bound of Rsub>g</sub> to less than infinity. Raytrace simulations of the tested system found that the observed data can be reproduced with a grating performing at Rsub>g</sub>=∞. It is therefore postulated that the behavior of the obtained Rsub>g</sub> posterior probability distribution can be explained by a finite measurement limit of the system and not a finite limit on Rsub>g</sub>. Implications of these results and improvements to the test setup are discussed.
