FOCUSING MONOCHROMATOR AND IMAGING-PLATE CAMERA FOR GRAZING-INCIDENCEDIFFRACTION STUDIES OF THIN-FILMS

A multiple-imaging-plate detector system and focusing monochromator ha ve been developed and successfully applied to the time-resolved study of phase transitions in Langmuir-Blodgett films by grazing-incidence X -ray diffraction (GIXD). The monochromator described here combines fix ed-exit-beam height with sagittal focusing of the second crystal. The design is similar to that of Matsushita et nl. [Matsushita, Ishikawa & Oyanagi (1986). Nucl. Instrum. Methods, A246, 377-379], with the exce ption that the motion of the first crystal is achieved via a computer- controlled X-Y translation table rather than a set of cams. The second crystal is a ribbed Si(111) wafer mounted in a four-point bending mec hanism. The first reported application of imaging plates to a GIXD stu dy was carried out by our group and proved to be very successful in th e determination of thin-film structure [Foran, Peng, Steitz, Barnes & Gentle (1996). Langmuir, 12, 774-777]. To extend the capabilities of t his system, an imaging-plate camera was designed and built which can a ccommodate up to 13 imaging plates (40 x 20 cm) inside the vacuum cham ber of the main diffractometer at the Australian Beamline at the Photo n Factory.