MICRODIFFRACTION AT BEAMLINES X25 AND X29

这个子项目是众多研究子项目之一

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. Microdiffraction at beamlines X25 and X29 H¿roux, Robinson Objectives  Both X25 and X29 are benefitting from improved capability to collect diffraction data routinely from smaller crystals. We have coordinated improvements between the two undulator beamlines to provide the users with a more consistent environment. We are pursuing the development of better ways to find small crystals with both conventional optics and with a grid search using x-rays. We continue implementing better control of the divergence to the users via CBASS. We want to implement more diagnostic tools to monitor the stability of the x-ray beam delivered by the NSLS. We are also deploying an automounter at X25 similar to that at X29. Results  Users are routinely collecting data with a 50x50 ¿m2 beam by slitting the apertures in the hutch to the desired size, and restricting the beam size upstream to control beam divergence. Macros to calibrate the slits have been implemented at both beamlines. Micro-crystal experiments by Soares using a beam size of approximately 10x10 ¿m2 did not require any special assistance from the beamline scientist. A very useful procedure to visualize the size of the beam at the sample (apertures + divergence) possible by the "burning" of a solution of glycerol containing cacodylic acid. This procedure takes only a few seconds of exposure to the x-rays and has a dual purpose of establishing the beam size and confirming alignment of the spindle with the beam. A chronic problem in crystallography is to localize the crystal in an ocean of mother liquor. Optical visualization is a problem since there is glare on the mother liquor, there is optical distortion, and one direction is not visible (through the side of the loop). Better digital cameras have been implemented at both beamlines. We have also implemented x-ray grid searches to supplement the optical technology (see software development by Skinner). We installed a beam-position monitor just downstream from the monochromator. This device enables us to record the position of the beam as well as the intensity for each image. The users now have plots of the behavior of the beam at the end of the html log for every dataset taken at X25. We will complement this work by the addition of a white-beam position monitor. Repair of the focusing-mirror motors has enabled us to improve the optimization of the vertical size of the beam (set at 70-90 ¿m) with a horizontal focus of 260 ¿m. We purchased an amplifier / multichannel-analyzer for a new x-ray fluorescence emission detector. This is a mobile unit which can be brought to any of our beamlines at the user's request. Within seconds, the users can scan the sample and determine what metals are present. The Q315 detector was upgraded last summer. Plans  We will install an automounter at X25 soon. We are in the process of acquiring a white-beam position monitor. This work is done in collaboration with the NSLS-II experimental facilities division (J. Kiester), BNL instrumentation group (J. Smedley) and Case Western University (J. Bohon). This new monitor will be positioned where a previous wBPM was installed at X25 years ago. This wBPM consists of two synthetic diamond crystals mounted in a cooled chamber. The photocurrent will be harvested and will give us information about the quality and stability of the white beam. Significance  Having a very good understanding of the beam quality and stability is fundamental when thinking about mini to micro beams. Developing a user base for this type of setup is important in order to prepare for new experiments done at NSLS-II. Any development has to take into account the users and their need. This is done by combining the efforts of X29 and X25 together.