Evaluating the Resolution of Gratings Patterned with Electron-Beam Lithography

X-ray spectra offer a wealth of information about the physical conditions around black holes, the hot gas surrounding galaxies, and stellar coronae. Getting these spectra, however, requires making precise X-ray gratings. These gratings must have grooves many times smaller than a human hair, and placing them at the sub-nanometer level. This groove placement can be accomplished with electron-beam lithography (EBL), and the gratings can be measured with an interferometer. EBL also opens new doors into how X-ray optics are designed, potentially reducing the number of optical surfaces required. This would decrease the size and mass of the instrument, thus reducing the cost to send it into space, all while increasing the sensitivity of the instrument. By using the 4D Technology Fizeau interferometer at the University of Iowa to assess and quantify errors in the grating pattern, we can gather vital feedback to the EBL patterning process. Measuring our grating and quantifying any residual errors in the period of the grating will allow us to evaluate the feasibility of new spectrometer designs and estimate their performance capabilities.