The x-ray transmission grating monochromator consists of a fixed entrance slit (slit 1) to collimate the beam, an AXAF type LETG grating facet (1008 lines/mm), and a fixed exit slit (slit 2) to select the wavelength (energy) of interest. The entrance slit and grating facet are mounted on a linear translator at about 450 cm from the x-ray source and 250 - 300 cm from the detectors (proportional counter or MCP detector). The monochromator provides a spectral resolution of about 3 Angstrom (determined by the finite source size) over an energy range of 0.1 to 3 keV. A test article can be placed between slit 2 and and measurement detector (e.g. and x-ray filter for transmission) or after the test article (e.g. an MCP detector).