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Note to X25 Users by Lonny Berman, January 26, 2006 |
Greetings. I believe that it has been more than one year since I last communicated to the NSLS X25
beamline user community via the
X25 listserver and this note.
Many of you are aware that the X25 beamline is sustaining a major upgrade, consisting of replacement
of the wiggler radiation source with an in-vacuum undulator, and various optics upgrades that will
serve to exploit the properties of the undulator source. Certain front end components were upgraded
as well. Details are described in the
X25 Upgrade Web pages.
At the moment, installation of the undulator is completed, along with the front end upgrades. The undulator will be commissioned during the next two months. We anticipate accommodating users beginning April 1, 2006. The general user allocations for X25 beam time, that were made for the January-April 2006 interval, were restricted intentionally in order that they could fit into the month of April. We anticipate being able to accommodate general users again, for a full scheduling cycle, beginning with the May-August 2006 interval. The percentage of beam time at X25 that is currently available to general users through the NSLS General User Program (PASS system) is 50%. The remaining 50% time fraction is overseen by the BNL PXRR (Macromolecular Crystallography Research Resource) through a Contributing User Agreement with the NSLS; rapid access to beam time on X25 can be applied for through the fraction that is overseen by the PXRR. The full 100% of X25's beam time is dedicated to macromolecular crystallography, as it has been for the past 2 years. It is actually for this reason that the upgrade, which seeks to optimize the beamline for a single purpose (as compared with X25's original generic purposes), was proposed and is being pursued. The beamline optics upgrades will be implemented during the course of this coming year, as they become ready and as the schedule of NSLS x-ray ring operation allows. The first upgrade that will be implemented is a cryogenic cooling system for the existing monochromator's first crystal (and new crystal to go with it), to replace the adaptively-bent first crystal and water cooling system which have been in service since 1992. The new system will be installed in February 2006, during the time period when the undulator itself will be commissioned. At the same time, a motorized bona fide goniometer for rotating the monochromator assembly in order to change the photon energy will be installed, to replace the limited-travel motorized tangent arm drive which has been in operation since the monochromator was originally installed in 1990. Later beamline optics upgrades include an entire new monochromator assembly to replace the existing one, and an entire new vertical focusing mirror system that will be installed downstream of the monochromator. Horizontal focusing of the beam will be achieved through sagittal bending of the monochromator's second crystal; the bending mechanism is part of the new assembly. The monochromator will be re-positioned in the beamline so that it can focus the beam in the horizontal direction at 3.3:1 demagnification. The existing 1:1 double focusing mirror system will remain in the beamline, but will not be used in the new optical configuration. Nevertheless, the capability to operate the beamline in its white beam configurations (focused or unfocused) will be preserved, including the option to use the double focusing mirror system in the white beam. Also in the works is a replacement of the diffractometer system in the hutch, which would incorporate a microfocusing optical element that could be introduced into the beam path just upstream, if desired. This is expected to be ready in about one year's time. |
| Finally, I would like to call your attention to recent personnel changes that affect X25. Michael Becker, the crystallographer who has overseen the X25 macromolecular crystallography program for the past 5.5 years, has recently departed. His associate who helped to support this program at X25, Shai Vaday, has also recently departed. Until their responsibilities have been transferred formally to others, Anand Saxena (asaxena@bnl.gov) will be overseeing the scheduling of users on X25. My associate, Steve LaMarra (slamarra@bnl.gov), and I will be overseeing the official training and hosting of X25 users. We thank both Mike and Shai for their contributions to X25, and wish them well in their new endeavors. |
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Because this listserver is seldom used to disemminate information pertaining to X25, its
recipient list isn't up to date, and the e-mail addresses for current recipients may not be
correct. Information about subscribing or unsubscribing to this list, as well as changing
subscription attributes, can be found at http://lists.bnl.gov/mailman/listinfo/nsls-x25-l.
Regards,
Lonny Berman |
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| Updated 27 Jan 2006 |
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