Contents of this Issue:
1. Science Highlight - Chromate Contamination
at DOE Hanford Site Partly Contained by Natural Reactions with Sediments
(contact: John Zachara,
john.zachara.pnl.gov)
Toxic and carcinogenic chromate (hexavalent chromium as CrO42-) has contaminated the groundwater in Hanford, Washington. At Hanford, hexavalent chromium was used in the industrial process to recover plutonium from irradiated nuclear fuels. The resulting high-level waste corroded its storage tanks and leaked into the desert subsoils. Plumes of contaminated groundwater reaching the Columbia River pose a risk to spawning salmon. Because of the depth and large volume (millions of gallons) of the contaminant plumes, existing abatement technologies are largely ineffective for mitigating the contaminated groundwater at this location. However, recent research indicates that the naturally occurring sediments at the Hanford site can immobilize chromate.
John Zachara (PNNL), Gordon Brown, Jeffrey Catalano (Stanford University) and their colleagues used x-ray absorption spectroscopy at SSRL to safely test contaminated (and highly radioactive) soil samples to determine the relative amounts and chemical forms of the chromate (carcinogenic hexavalent chromium or less toxic trivalent chromium). They found that about 42% of the chromate in the contaminant plumes had become an immobile solid of trivalent chromium due to reacting with ferrous iron-bearing sediments in the aquifer. Unfortunately, more than half of the chromium in the plumes remains as the dangerous hexavalent form (chromate), which moves readily through the subsurface sediments. However, the discovery by Zachara's research group (which is one of many ongoing studies at SSRL looking at contaminated sediments from Hanford) is an important step toward mitigating the problem. Developing technical solutions to such large-scale contaminant problems requires key insights into the form of the contaminant, which is intimately linked to its reactivity. This information allows engineers to assess the hazards posed by such extreme chemical and radioactive materials, as well as to design the most effective, long-term strategies to deal with them.
For more information on this work see:
http://www-ssrl.slac.stanford.edu/research/highlights_archive/cr.html
or
http://www-ssrl.slac.stanford.edu/research/highlights_archive/cr.pdf
2. First SPEAR3 Light Seen at BL9-3 and Progress
on Other Beam Lines and
Commissioning
(contact: Tom Rabedeau,
rabedeau@ssrl.slac.stanford.edu)
Another major milestone for the SPEAR3 commissioning and resumption of SSRL user operations occurred when first light was brought into Beam Line 9-3 on March 8. The light observed on the monitor inside BL9-3's hutch showed banding which is consistent with the effect of the separated pole pairs in the wiggler viewed at the 5-mrad off-axis observation angle of BL9-3. This effect could not be seen with the old SPEAR2 ring as its source size was so big that the radiation from each pole pair could not be resolved, so the effect of the reduced source size on SPEAR3 was immediately seen. Light has subsequently been brought into BLs 9-1, 9-2, 6-2, 10-1, 10-2, and 5-4. Commissioning efforts on these beam lines are already showing the improved performance under SPEAR3:
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The first SPEAR3 data set was measured on BL9-3 on March 15, for biological
x-ray absorption spectroscopy, and throughout this first scheduled block of
user beam time, a number of data sets at excellent quality were obtained.
Beam line operations will continue to resume in stages, paced by completion of electrical work, hutch upgrades, PPS checkouts and certification, shielding, Radiation Physics approval and commissioning. Special SPEAR operation conditions will be required when beam lines are opened over the next several weeks, mainly in the form of brief access periods to remove the locks from the injection stoppers and lower currents (25-50 mA) for the first few hours. PA system announcements will be made before these periods and before fills. Users may request a brief delay on the fill time to coordinate their scans and maximize their data taking. SPEAR status updates are available on the website: http://www-ssrl.slac.stanford.edu/talk_display.html
SPEAR3 will operate at 100 mA for this first user run while beam line optical components are upgraded and radiation shielding is added for higher current operation. During this first run year, the accelerator physics and engineering groups will characterize and optimize ring lattice and beam parameters, develop the fast orbit feedback system and ascertain beam stability issues that could be encountered at the higher currents being planned for operation following the initial commissioning run.
Operating and beam time schedules are available on the web at:
http://www-ssrl.slac.stanford.edu/schedules/.
3. Instrument Development Workshop held on LCLS
Biological Imaging Experiments
(contacts: Henry Chapman,
henry.chapman@llnl.gov; Keith Hodgson, hodgson@ssrl.slac.stanford.edu)
Over 60 participants attended the "Instrument Development Workshop for LCLS Biological Imaging Experiments." held at SLAC on March 15-16, 2004. The workshop consisted of a day and a half of presentations and discussion to determine the research needs for single-particle diffraction imaging, and other atomic-resolution imaging methods, to be carried out on the LCLS. The meeting consisted of briefings on critical aspects of the source, detectors, x-ray optics, effects of rapid photoionization on image degradation, data processing (classification of diffraction patterns, registration, and image reconstruction), and sample handling, among many other issues. Breakout sessions were also held to develop a thorough understanding of project risks, mitigation strategies as well as milestones, deliverables and costs. The overwhelming feeling at the workshop was that while much challenging research needs to take place to develop the required techniques, the community will be able to field imaging experiments at the LCLS at the 2009 operations date.
For more details regarding this workshop and the LCLS project see:
http://www-ssrl.slac.stanford.edu/lcls/
4. Pre-registration Required for On-site
Users
(contact: Cathy Knotts,
knotts@slac.stanford.edu)
U.S. Government regulations related to facility access require that facilities
collect biographical information from users in advance of their scheduled visit
and before ID badges can be issued. For users who are not U.S. citizens but
were born in, are citizens of, or represent organizations from certain foreign
countries that the government has identified as either sensitive or state
sponsors of terrorism (SST), additional information must be collected and
forwarded to the DOE for approval of the visit. Spokespersons are required to
provide contact information for all collaborators who plan to be on-site to
work under their proposals, and those collaborators must pre-register by
completing the SSRL User Information Form at least 1 month before their
anticipated visit. We recognize the time and effort needed to comply with this
new requirement, and appreciate your full cooperation with this effort.
http://www-ssrl.slac.stanford.edu/users/user_admin/user-info-form.pdf
5. Stanford-Berkeley Physical Sciences Summer
Postponed until 2005
The 2004 Summer School Program has been postponed until summer 2005. Additional information on the 2005 Summer School will be forthcoming at a later date.
6. Convenient On-site Lodging and Local
Shuttle Service
(contact: Cathy Knotts,
knotts@slac.stanford.edu)
The SLAC Guest House provides comfortable and convenient accommodations for SSRL users and visitors at unbeatable rates including standard rooms with full size bed ($50), larger rooms with queen size bed ($65), and shared rooms with bunk beds ($32.50); all rooms have a private bathroom. Be sure to mention that you are an SSRL user when booking a reservation. http://www.stanford.edu/dept/hds/SLAC/.
The Stanford Marguerite provides free shuttle service to several locations in the Palo Alto area. The SLAC line operates Monday-Friday (except holidays) between SLAC, SU Science & Engineering Quad, West Campus Residences, and Hoover Tower every 40 minutes from 7:30 am-6:00 pm. A SLAC shuttle operates Monday-Friday (except holidays) between the Palo Alto train station and SLAC from 6:41 am-8:15 am and again from 3:20 pm-5:00 pm. http://transportation.stanford.edu/marguerite/MargueriteSched.shtml
7. Upcoming Public Lecture on Synchrotron
Radiation: The Light Fantastic
(contact: Uwe Bergmann,
bergmann@slac.stanford.edu)
SLAC if offering a series of public lectures geared towards the nonscientific community. The next in the series, a synchrotron-related lecture given by Herman Winick, will be held on April 27, 2004 from 7:30-8:30 pm at the SLAC Panofsky Auditorium. See the SLAC Public Lecture Series web site for more information: http://www2.slac.stanford.edu/lectures/
8. User Administration Update
(contacts: Cathy Knotts,
knotts@slac.stanford.edu; Lisa Dunn, lisa@slac.stanford.edu)
New Macromolecular Crystallography (MC) proposals are due April 1, and MC beam
time requests for the next scheduling period are due on April 17.
http://www-ssrl.slac.stanford.edu/users/user_admin/px_proposal_guide.html
New X-Ray/VUV proposals are due May 1 or November 1. Proposals instructions and
forms can be found on the web at:
http://www-ssrl.slac.stanford.edu/users/user_admin/xray_vuv_proposal_guide.html.
__________________________________________________________________________
SSRL Headlines is published electronically monthly to inform SSRL users, sponsors and other interested people about happenings at SSRL. SSRL is a national synchrotron user facility operated by Stanford University for the U.S. Department of Energy Office of Basic Energy Sciences. Additional support for the structural biology program is provided by the DOE Office of Biological and Environmental Research, the NIH National Center for Research Resources and the NIH Institute for General Medical Sciences. Additional information about SSRL and its operation and schedules is available from the SSRL WWW site.
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