The 9030DA double additive monochromator consists of two 9030 monochromators placed in series. Stray light is drastically reduced in a double monochromator, and in the 9030DA it is further minimized by the use of concave holographic gratings. The inbound light is dispersed by the first grating and again by the second. Both gratings rotate simultaneously in the same direction, and in the DA the monochromators are coupled so that the dispersion is double that of a single 9030 monochromator. Bandpass is half of the corresponding 9030 monochromator for the same output slit, and resolution using a 100 um slit is 0.4 nm.This includes one set of standard slits, but the grating must be selected/specified separately.