X-RAY GRATING EVALUATION FACILITY

(X-ray Source Chamber, Loading Chamber, and Detector Chamber) In MIT's X-ray Grating Evaluation Facility (X-GEF) a quasi-monochromatic X-ray source is collimated by opaque slits or an adjustable mirror. Selected quasi-monochromatic lines are used to determine the calibration at discrete energies. The efficiency of certain transfer standard gratings is measured at the energies of the quasi-monochromatic lines and over a broad energy band at the Brookhaven Synchrotron. These gratings are used to calibrate the X-GEF and to characterize the continuum radiation from the X-GEF X-ray sources. This knowledge of the source continuum allows calibration over a broad range of energies. The first order diffraction efficiency is measured as a function of incidence angle. This gives a measure of the physical thickness of the grating lines, and allows measured grating efficiency to be correlated with the electromagnetic model of the diffraction by grating bars. The data is used as feedback to the fabrication process, and as a consistency check on the calibration model.