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4. Metrology for Measuring Custom Periodicities on Diffraction Gratings.

Author

Zhang, Ningxiao, McEntaffer, Randall, McCurdy, Ross, and DeRoo, Casey

Subjects
OPTICAL interferometers, DIFFRACTION gratings, METROLOGY, INTERSTELLAR molecules, SCANNING electron microscopy
Abstract

We present a new, inexpensive, bench-top method for measuring groove period over large areas with high mapping resolution and high measurement accuracy, dubbed the grating mapper for accurate period (GMAP). The GMAP has the ability to measure large groove period changes and nonparallel grooves, both of which cannot be measured via optical interferometry. In this paper, we detail the calibration and setup of the GMAP, and employ the instrument to measure three distinct gratings. Two of these measured gratings have customized groove patterns that prevent them from being measured via other traditional methods, such as optical interferometry. Our implementation of this tool achieves a spatial resolution of 0.1 mm × 0.1 mm and a period error of 1.7 nm for a 3 μ m size groove period. [ABSTRACT FROM AUTHOR]

Published
2021
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5. Performance Testing of a Large-Format X-ray Reflection Grating Prototype for a Suborbital Rocket Payload.

Author

Donovan, Benjamin D., McEntaffer, Randall L., DeRoo, Casey T., Tutt, James H., Grisé, Fabien, Eichfeld, Chad M., Gall, Oren Z., Burwitz, Vadim, Hartner, Gisela, Pelliciari, Carlo, and Caria, Marlis-Madeleine La

Subjects
X-ray reflection, SPECTROMETERS, PROBABILITY theory, ELECTRON beam lithography, FABRICATION (Manufacturing)
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 > 2 5 0 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 R g (λ ∕ Δ λ) > 4 5 0 0 at the 94% confidence level. The resulting R g posterior probability distribution suggests that this confidence level is likely a conservative estimate though, since only a finite R g parameter space was sampled and the model could not constrain the upper bound of R g to less than infinity. Raytrace simulations of the tested system found that the observed data can be reproduced with a grating performing at R g = ∞. It is therefore postulated that the behavior of the obtained R g posterior probability distribution can be explained by a finite measurement limit of the system and not a finite limit on R g . Implications of these results and improvements to the test setup are discussed. [ABSTRACT FROM AUTHOR]

Published
2020
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