This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The decision has been made that the re-commissioning and characterization of the 8BM optics would lead to upgrades in the current monochromator. This was to be carried out while the beamline is still at 8-BM so as to reduce the commissioning time after the move to the Sector 24 bending magnet source. Characterization of the optics has identified several elements of the current monochromator that could benefit from upgrades. The first was discovered early on. There were problems in the direct cooling of the first crystal that has led to the possibility of a bulge in the first crystal. A possible solution to this problem is the replacement of the first monochromator crystal by a newer, micro-finned, direct, water-cooled crystal that can be retrofitted into the Oxford Danfysik double crystal monochromator. This new first crystal was installed in December 2005 in conjunction with Oxford Danfysik. The horizontal focusing that is accomplished by the sagittal second crystal has never reached full potential. The difficulty of separating the problems in the first crystal and that of the second has slowed the redesign in the second crystal bender. As a first step in the direction of improving the performance of the second crystal, we have decided to reduce the step size of the motors used to bend the crystal and to install Linear Variable Differential Transformers (LVDT) to measure the displacement directly. The combination of gear reducers and LVDT s will increase the reproducibility of this motion. The added torque from the gear reduced motors will be able to accommodate the smaller radii that are possible after the relocation of the beamline to Sector 24. The new sagittal bender assembly was installed in December 2005 with the first crystal installation. The majority of the early commissioning and characterization has been restricted to overcoming the changes introduced by the installation of a new first crystal and the change in the bending motors of the second crystal. Recurring problems with restrictions in the Yaw motor have been overcome and compensation for the slight changes in the height of the new and re-installed crystals along with a recalibration of the Bragg angle has been accomplished. It is clear that the vertical focusing performance is not satisfactory. The measured flux is similar to the one prior to the upgrade. Further characterization will be performed when the beam comes back in June. Finally, a combination of a 4.7 mrad tilt angle of the mirrors and artificial restrictions in the travel of the second crystal have limited the current energy range of the monochromator to 14.5 keV. This will be resolved after further characterization.
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