A LASER-AIDED PREALIGNED PINHOLE COLLIMATOR FOR SYNCHROTRON X-RAYS

A pinhole small-angle x-ray scattering (SAXS) instrument was construct ed at the SUNY X3A2 beamline, National Synchrotron Light Source, Brook haven National Laboratory. The three pinholes were mounted in a thick- walled stainless steel pipe and prealigned by using a portable laser s ource and a charge-coupled device (CCD) area detector. After the preal ignment, incorporation of the collimator to the synchrotron x-ray sour ce required only maximization of the incident x-ray intensity passing through the pinholes, which could be done easily by using a scintillat ion counter after proper attenuation. The entire synchrotron SAXS inst rument setup took only a few hours even without stepping motor control for the pinhole collimator unit. By combining this collimator with a CCD-based x-ray area detector which could be assembled by using commer cially available components, the SAXS instrument showed good performan ce for structural scales up to an order of 100 nm. The CCD-based x-ray area detector used a computer(or manually) controlled intensified uni t with a variable gain setting in order to accommodate the changing x- ray flux and to protect the detector from over exposure, a necessary f eature for operation of an area detector at a synchrotron light source .