This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.Beamline X25 Development Objectives The major objective during this year was to complete the upgrade of X25. The new undulator was in place and commissioning was underway when this report was written last year. The experimental station was to be brought into operation for the remainder of the year. A second objective was to install the new monochromator and focusing mirror assemblies that had been ordered at the end of last year. This would require modifications of the existing beamline, and to design and accomplish these modifications was an ancillary objective. The new optics would be installed during and after the end-of-year shutdown. Another objective was to begin acquisition of a new diffractometer for X25 that would be able easily to handle crystals down into the 10-20 m range. The final objective is to bring the beamline back into operation before the end of the grant year. Results Commissioning of the new undulator involved careful measurement of its behaviour, and comparison with the expected performance. Also the gap settings needed to be calibrated to the peak photon energies being emitted so the gap and monochromator angle could be matched. The magnets that eventually were acquired for the undulator were stronger than those originally specified, so there was a shift of emission to higher brightness and (paradoxically) to lower energy. The end result is a better undulator. This commissioning of the undulator was completed and the beamline was brought into operation in April '06 with use of the original x-ray optics. X25 has operated for six months since the undulator was commissioned, employing the diffractometer that had been upgraded during the May '06 shutdown. It has been operated principally through a rapid-access mechanism and was able to accommodate all of the General Users. The new monochromator and mirror appear to be working, and we are preparing to take data at the time of writing. The monochromator (built by Larry Rock Design, Inc.) employs a Si(111) crystal to provide monochromatization, followed by a bent Si(111) crystal that focuses the beam in the horizontal direction. The first crystal is cooled to approximately 100K with a closed-loop refrigeration unit that employs He gas as a heat-transfer agent. The monochromator is followed in the beamline by a bent-plane mirror that provides vertical focusing. The mirror has two reflective surfaces, silica and palladium. The silica will be used in low-energy ranges and the Pd in high to provide rejection of the Si(333) reflection from the monochromator. We anticipate that the beamline will be commissioned and in operation by the end of May '07. We have ordered a new diffractometer for X25 from Crystal Logic after a competitive design and bidding process. The emphasis for this instrument will be to handle very small crystals while still being versatile enough to handle other innovations. The existing Q315 detector will be mounted on the lift table that now carries the whole diffractometer, and the diffractometer will stand alone on a stable base. The carriage for the detector is counter weighted an equivalent weight hidden in the support will move in synchrony in the opposite direction to keep the center of mass stationary to make this mount extremely stable. The diffractometer will have an in-line microscope that will allow one to position a crystal precisely (within a few m) on the direct beam, which can be visualized on a phosphor screen placed at the specimen position. The beam-conditioning system will typically be motorized slits. The mounting is such that these can be replaced with a one-bounce parabolic capillary to provide a small, clean beam. Plans We are responding to the intense need within the community we serve to be able to perform diffraction studies on very small crystals. This next year will be filled with balancing routine data collection with exploring the use of our new micro-crystal diffractometer. We imagine that X25 will continue to be the site for very difficult projects, complementing the high-throughput emphasis at X29. We also plan to move the existing Crystal Logic diffractometer from X25 to X26-C, replacing the nearly 20-year old Enraf-Nonius currently operating there. Significance The new upgrades to the optics and micro-diffractometer will allow us to push further into the use of tiny crystals. The brightness of X25, which should surpass that of X29, also will provide us with experience that will be valuable as we work to plan development of beamlines for NSLS-II.
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