A laser-aided prealigned pinhole collimator for synchrotron x rays

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Abstract
A pinhole small‐angle x‐ray scattering (SAXS) instrument was constructed at the SUNY X3A2 beamline, National Synchrotron Light Source, Brookhaven National Laboratory. The three pinholes were mounted in a thick‐walled stainless steel pipe and prealigned by using a portable laser source and a charge‐coupled device (CCD) area detector. After the prealignment, incorporation of the collimator to the synchrotron x‐ray source required only maximization of the incident x‐ray intensity passing through the pinholes, which could be done easily by using a scintillation counter after proper attenuation. The entire synchrotron SAXS instrument 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 commercially available components, the SAXS instrument showed good performance for structural scales up to an order of 100 nm. The CCD‐based x‐ray area detector used a computer‐ (or manually) controlled intensified unit with a variable gain setting in order to accommodate the changing x‐ray flux and to protect the detector from over exposure, a necessary feature for operation of an area detector at a synchrotron light source.