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Contents of this Issue:
1. Science Highlight - Investigating Chromium-Contamination and Remediation
(contact: Colleen Hansel, Stanford University)
Industrial activities have led to widespread chromium (Cr) contamination in
the environment. Although Cr is an essential element for humans, the
hexavalent form is toxic, mutagenic and carcinogenic. Consequently, the
presence of Cr in the environment poses a serious threat to human and animal
welfare. However, the toxicity of Cr is a function of oxidation state. For
example, hexavalent Cr has a high solubility in soils and groundwater and, as a
consequence, tends to be mobile in the environment. In contrast, a more
reduced form of chromium, Cr(III), has limited hydroxide solubility and forms
strong complexes with soil minerals. While trivalent Cr is relatively
innocuous and immobile, hexavalent Cr is actively transported into cells by the
sulfate transport system where it is capable of causing damage to DNA as well
as indirectly generating oxygen radicals. Accordingly, reduction of Cr(VI) to
Cr(III) is an important means by which the harmful effects of this toxin are
mitigated. This general process forms the fundamental basis of a large number
of technologies currently being tested for remediation of chromium-contaminated
soils. Researchers from Stanford University's Department of Geological and
Environmental Sciences are working on this problem using a combination of
aqueous chemical measurements and x-ray absorption spectroscopy (XAS). This
research is leading to a greater understanding of the solubility and reduction
of Cr as well as to techniques that can be used to predict the ultimate
solubility of Cr in mature, bioremediated systems.
or http://www-ssrl.slac.stanford.edu/research/highlights_ archive/cr_contamination.pdf
2. SPPS Experiment Begins at SSRL and SLAC
(contacts: Jerry Hastings, SSRL; John Arthur, SSRL)
The Sub Picosecond Pulse Source (SPPS) experiment began in May as a collaboration involving SSRL/SLAC, ANL, BNL, DESY, Lund University, University of California, University of Copenhagen, University of Michigan and Uppsala University. The SPPS project is made possible by an upgrade to the existing SLAC linear accelerator (linac), along with specialized new instrumentation, to produce extremely short pulses of electrons and in turn x-rays. This project provides a fast, relatively inexpensive way to begin experiments with a new generation of very bright, sub-picosecond (less than one millionth of one millionth of a second), hard x-rays. In the last several months, staff from SSRL and other SLAC divisions have been busily installing, performing diagnostics and commissioning instrumentation in preparation for the first SPPS experiments. First x-ray beam into the SPPS was achieved at 8:30 p.m. on Monday, May 19, 2003.
SPPS works by compressing, in several stages, electron bunches created in the standard gun and damping ring of the SLAC linac. A new 10 meter-long bunch compressor chicane was installed near the one kilometer point in Sector 10 of the linac last winter to provide further compression. The 'dog-leg' bend into the Final Focus Test Beam line at the end of the linac does the final compression, yielding a 28 GeV electron bunch with length of 12 micrometers rms (which in time equates to less than one tenth of a picosecond). Finally, a magnetic undulator-an array of permanent magnets-produced an ultra-short pulse of high-brightness x-rays from this electron beam.
One of the unique features of the SPPS is its combination of brightness and sub-picosecond pulse length. The peak brightness of SPPS will exceed that of any existing hard x-ray source by several orders of magnitude and its pulse length is about 80 femtoseconds. This combination will allow the collection of flash measurements of the atomic positions of materials as they undergo changes following an impulse from an ultrafast optical laser. These studies will provide the opportunity to gain direct insights into important processes such as structural changes during actual chemical reactions. In addition, the SPPS will play a role in the accelerator and x-ray optics R&D for the future Linac Coherent Light Source (LCLS) x-ray free electron laser project. Researchers will be able to develop and refine the diagnostic tools associated with the production and use of ultra-short electron and x-ray pulses, and they will be able to gain valuable experience that will be needed for the successful early operation of the LCLS when it comes on-line, which is expected to be in 2008. see related article in SLAC Interaction Point
3. SPEAR3 Installation Progress Continues on Track
(contact: Tom Elioff, SSRL)
The SPEAR3 installation program involves 3 phases: (1) demolition of SPEAR2, (2) preparation of facilities to meet SPEAR3 needs, and (3) the installation of SPEAR3 technical systems and components. Each phase involves a complex procedure that is planned in great detail such that overall completion can be achieved by the end of October 2003. Phase 1 was completed ON SCHEDULE at the beginning of this month and phase 2 is already underway and currently ahead of schedule.
In order to minimize the installation period, an early decision was made to assemble and pre-align the magnets and vacuum system components of the new lattice on support rafts that were more easily transportable. In order to also meet stringent new stability requirements and to meet new earthquake standards, a new reinforced concrete floor was needed for the ring tunnel. A new heavy duty floor was also required for the power supply building.
This month, the existing asphalt of the power supply building floor was removed. Within the narrow confines of the SPEAR tunnel, the existing asphalt and sandstone were excavated to ca. a 20-inch depth and sealed with a concrete mix. Rebar installation and the final concrete pour were completed for Quadrant #1. Completion of the other three quadrants is scheduled for early June.
In addition to the above facility preparations, efforts continued to finalize the preparation of all technical systems for phase 3. See video
4. XAS-Imaging User Commissioning Run on BL9-3
(contacts: Ingrid Pickering, SSRL; Graham George, SSRL; Daniel Durkin, SSRL)
XAS users may recall that a brief period of beam time was set aside on BL9-3 in March for user commissioning of the structural molecular biology XAS imaging facility. Funded by the NIH-NCRR, this facility is designed to image metals and metalloids in dilute biological systems. It uses metal mono-capillary focussing optics (developed by Greg Hirsch of Hirsch Scientific) which currently can generate a spot size down to 5 microns. A 1-element detector is used to detect fluorescence of dilute elements. A high-precision (< 50 nm) raster-scan stage combined with the highly monochromatic BL9-3 beam enables complete images to be achieved at two or more energies in order to generate maps of specific chemical species. Additionally, XAS spectra can be collected from a specific pixel on the map. User-friendly data collection is achieved with software developed at SSRL.
Several users submitted proposals to participate in this commissioning, but due to time constraints only some could be allocated beam time. Robert Scott (U. Georgia) used the setup in a low resolution mode to carry out feasibility studies of a high throughput XAS method to screen an entire proteome for metal binding. David Salt (Purdue U.) studied the distribution and chemical form of arsenic in intact tissues of a hyperaccummulating fern. Helen Nichol (U. Saskatchewan) investigated insect metalloproteins separated by non-denaturing 2-d page and localized iron in the brains of living fruit flies, including collecting Fe K-edge XAS spectra from specific regions in situ. James Penner-Hahn (U. Michigan) used the facility to determine the distribution of metal ions in the byssus of marine bivalve mollusks and in developing zebrafish embryos. All groups reported a positive experience. The feedback from these March 2003 experiments will provide valuable information on this facility as we prepare for the SPEAR3 upgrade and develop plans to make this facility more routinely available to users.
5. BL6-2 Available for Low Energy XAS with SPEAR3
(contacts: Serena DeBeer George, SSRL; Britt Hedman, SSRL)
Due to continuing scientific demand from the SSRL user community for access to low energy (2-3 keV) XAS experiments (in particular for P, S, and Cl K-edge spectroscopy), the decision has been made to maintain this capability for general users on BL6-2 when SPEAR3 becomes operational in 2004. BL6-2 will continue to be used for these experiments until low-energy capabilities become available on BL3-3 and BL4-3, which will be upgraded in the 2004 to 2006 timeframe, as determined by funding. SSRL and its staff look forward to supporting the 2-3 keV user community in 2004 and in the coming years.
6. Transitions in Leadership in ASD and SPEAR3
(contact: Keith Hodgson, SSRL)
After 12 years at the helm of SSRL's Accelerator Systems Department (ASD) Max Cornacchia felt that the start of the SPEAR3 era would be a good time to step down from his position. Bob Hettel is the new Assistant Director for ASD in his place. Max will continue as head of the Accelerator and FEL Physics group within the ASD, and will be involved with LCLS, SPEAR3 and other accelerator research and development. At the same time, Tom Elioff elected to turn over leadership of the SPEAR3 Upgrade Project to Bob and to assume the role of project Deputy Director. This position will enable Tom work on a reduced schedule while still playing a critical role in tracking the progress of the project and its installation, and providing valuable advice for its successful completion.
We all thank Max for his superb leadership and, together with the members the ASD, for contributing so much to the great success of SPEAR2 over the past decade. Under his leadership, SPEAR2 performance, particularly its reliability and stability, made major progress. This has been a critical element in transforming SSRL into a premier national user facility, enabling outstanding experiments to be done and paving the way for SPEAR3. In addition, Max made major contributions to the development of LCLS, coordinating the first Design Study Report published in 1998 and promoting worldwide interest in x-ray lasers and other advanced accelerator topics.
SSRL is indebted as well to Tom, whose visionary and seasoned management of the SPEAR3 project has enabled a successful collaborative effort between SSRL and SLAC technical groups and with the DOE. The SPEAR3 project adds to Tom's distinguished career in the accelerator world, which includes his prominent involvement with the development of the Bevatron and the ALS at LBNL, more than a decade of contributions to the SSC project, deputy directorship of the PEP-I and PEP-II projects at SLAC and coordination of the LBNL effort to install the first permanent magnet wiggler in SPEAR for BL6.
7. SLAC Scientific Policy Committee Meets
(contact: Keith Hodgson, SSRL)
The SLAC Scientific Policy Committee (SPC) held its spring meeting May 2-3, 2003. The SPC is SLAC's highest level external advisory committee, reporting to Stanford University President John Hennessy on all aspects of ongoing activities, future plans, ES&H, etc. The SSRL-related portion of the SPC meeting featured an overview talk by SSRL Director Keith Hodgson. Jerry Hastings, SSRL Assistant Director for the SPPS project, gave an update on the status of the experiment. Arthur Bienenstock, Director of the Geballe Laboratory of Advanced Materials and SSRL faculty member, discussed the Gateway program, the goal of which is to encourage Mexican-American and Mexican students to participate in scientific and engineering research via synchrotron radiation research at SSRL. Ashley Deacon, who is leading SSRL's structural genomics group, spoke about developments in the area of new tools for high-throughput structural biology at the Joint Center for Structural Genomics, one of the nine centers funded under the Protein Structure Initiative. Ashley underscored the importance of these new developments to the general user program as they are now being made available to all users. Uwe Bergmann, Chair for the SSRL Users' Organization Executive Committee (SSRLUO-EC), gave a report on the users' perspective of SSRL operations and future plans. At its closeout session, the SPC was very positive about the SSRL plans for the future - including SPEAR3, LCLS and the SPPS experiment.
8. Register Now for SRI 2003 and X-ray Coherence Satellite Meeting
Register before Tuesday, June 3, 2003, to take advantage of the early registration discount for the 8th International Conference on Synchrotron Radiation. SRI 2003, sponsored by SSRL and the ALS, will be held August 25-29, 2003, at the Yerba Buena Center for the Arts which is centrally located in downtown San Francisco. Visit the SRI 2003 website for the latest program information on this conference. Blocks of rooms have been reserved at several nearby hotels at reduced conference rates, but attendees should make their travel arrangements early to ensure the discounted rates. Additional accommodations are available at the new SLAC Guest House for those who would enjoy very favorable rates and not mind the commute up to the City for the conference (see item 10. below or visit the Guest House website for information about guest house reservations and other information).
A workshop on X-ray Science with Coherent Radiation will be held August 22-23, 2003, as a satellite meeting of SRI 2003. This 2-day workshop will explore novel scientific applications of future coherent hard x-ray sources, including both applications that make use of dc source properties and applications that depend on pulsed sources. Topics will include all aspects of a coherent experiment, from source and optics to experimental techniques, applications and analytical methods. The deadline for abstract submission and advance registration is July 1, 2003. For more information, visit the workshop website.
9. SSRLUO-EC Update
(contacts: Uwe Bergmann, SSRL; Benjamin Bostick, Dartmouth College)
The SSRL Users' Organization Executive Committee (SSRLUO-EC) met on Friday, May 9, 2003. At this meeting, Uwe Bergmann and Benjamin Bostick (Chair and Vice Chair, SSRLUO-EC) summarized a recent visit to Washington and encouraged other users to take the time to contact their congressional representatives to explain the importance of synchrotron radiation studies in their own research. More information including the list of appropriations committee members and template letters is available on the SSRLUO Activism page. see Meeting Minutes
Plans are underway for the 30th Annual SSRL Users' Meeting which will be held October 9-10, 2003. Scientific sessions will include: Micro X-ray Beam Spectroscopy and Diffraction, Spectroscopy and Crystallography of Macromolecules, Small Angle X-ray Scattering and Surface Spectroscopy and a focus is also planned on the SSRL-UTEP Gateway Program. In addition, several workshops will be planned for Wednesday, October 8, including one on high throughput crystallography. If you have suggestions for other workshop topics, please contact Cathy Knotts, firstname.lastname@example.org. The preliminary program and other information will be posted to the meeting website.
10. SLAC Guest House Taking Reservations
The SLAC Guest House, scheduled to open on June 19, 2003, is now accepting
reservations. This new 112-room facility will provide lodging accommodations at
discounted rates for users, visitors and other individuals affiliated with the
SLAC and SSRL as well as Stanford University. Well-appointed guest rooms are
configured in various sizes and bed types to accommodate individual needs.
Each room includes cable TV, high-speed internet connections via SLAC's
network, telephone, coffee maker, desk, wardrobe, air-conditioning and a
private bathroom. Mini-refrigerators, microwaves, hair dryers, roll-a-way
beds, etc., are also available upon request. Other amenities include: 24-hour
reception desk, gift shop, exercise room, laundry facilities, daily
housekeeping services, lounge with large screen TV, spacious lobby, kitchenette
and a landscaped exterior courtyard. If you are planning any summer meetings
or workshops, contact Enrique Jevons, General Manager of the SLAC Guest House
(650-926-2800; email@example.com) to reserve group blocks. For more
information and to make individual reservations, please visit the
Guest House website.
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 S ciences. Additional information about SSRL and its operation and schedules is available from the SSRL WWW site.
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