A description is presented of a flight-qualified large-aperture 12 × 12-sec of arc angular resolution multigrid x-ray collimator developed for the Solar Maximum Mission (SMM) flat crystal spectrometer. This collimator, designed for the 1.4–22.4-Å wavelength range, utilizes an optical bench/metering structure to align and support prealigned grid subassemblies. One advantage of this scheme is to provide ready access to the grid subassemblies for inspection and/or servicing. The optical bench is a lightweight, rigid, and stable aluminum honeycomb structure. Aluminum is a viable material choice in this application because of the good thermal control expected in the SMM instrument package. The grids are of a compound and bimetallic design, having 63.5-μm square holes on an 88.9-μm spacing in 8-μm thick gold, which is in turn supported by a 76-μm thick Invar grid having 600-μm square holes on a 739-μm spacing. The small apertures in the gold provide the 12-sec of arc collimation with the Invar grids providing wide angle off-axis blocking out to an ~35-min of arc view angle. The collimator has seven individual channels, four of a 5.1- × 10-cm area and three of a 1.3- × 10-cm area. Laboratory measurements gave an average angular resolution of 12.5-sec of arc FWHM with 0.259 transmission for the large area channels and 12.0 sec of arc and 0.200 transmission for the small area channels. A hypothetical perfectly aligned collimator would have 12.5-sec of arc resolution and 0.300 transmission. A thermal filter composed of two layers of ~1000-Å thick aluminum prevents solar heating of the front collimator grids by absorbing longer wavelength radiation while passing most of the x radiation in the band of interest. The filter was flight qualified by passing a protoflight acoustic test environment of 147-dB total sound level, 20-μN/M2 reference, for 1-min duration.
© 1980 Optical Society of AmericaFull Article | PDF Article
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