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Last Updated: | 01 DEC 2003 |
| Content Owner: | L. Dunn | |
| Page Editor: | L. Dunn |
**** **** **** * * * * * * **** **** **** * * * * * * **** **** * * **** HEADLINES - a digital monthly publication
Contents of this Issue:
1. Science Highlight - Structure of Actin
Cross-linked with a-Actinin: A Network of Bundles
(contact: Cyrus Safinya, University of
California at Santa Barbara)
With the completion of the Human Genome Project and the emerging proteomics era, the biosciences community is beginning the daunting task of understanding the structures and the structure-function relations of collections of interacting proteins. Cellular activity, which is tightly regulated, often results from protein-protein and protein-nucleic acid interactions, leading to the formation of large assemblies of biomolecules for distinct functions. Examples include DNA condensation during the cell cycle, and bundle and network formation of filamentous actin proteins in cell attachment, motility, and cytokinesis.
A group of researchers from the University of California at Santa Barbara have recently reported on the structure of filamentous (F) actin complexed with the actin cross-linking protein alpha-actinin. The synchrotron-based SSRL work has led to a proposed structure of F-actin bundles showing how the cross-linking protein alpha-actinin induces a network-like structure in F-actin at low concentrations, with a gradual transition as a function of increasing concentration, to a bundle phase consisting of a disordered nanoscale quasi-square lattice. The work, carried out by O. Pelletier, E. Pokidysheva, L. S. Hirst, N. Bouxsein, Y. Li and C. R. Safinya, appeared in Physical Review Letters 91, 148102, 2003), and was further highlighted as the Cover Image of the October 3rd issue. The research was supported by the National Institutes of Health, the National Science Foundation, and the Department of Energy.
For more information on this work see:
http://www-ssrl.slac.stanford.edu/research/highlights_archive/actinin.html
or
http://www-ssrl.slac.stanford.edu/research/highlights_archive/actinin.pdf
2. First Beam Stored in SPEAR3!
(contact: Bob Hettel)
Major milestones were observed over the last few weeks as SPEAR operators and
accelerator physicists reported the first beam signals at SPEAR3 from the
booster on December 10 - right on schedule! On the following day, the first
injection into SPEAR3 occurred when a single 3 GeV bunch was injected into
SPEAR3 and made a complete turn around the ring. By the afternoon of December
11, 10-15 turns were observed, which is as much as was expected without the RF
system. On December 12, operators turned on the RF system which enabled the
possibility of storing beam. Working through the weekend, the SPEAR3
commissioning crew achieved the first stored and accumulated beam on Monday,
December 15. These activities demonstrate that the major systems, including
performing at-energy injections, are working as planned and provide
encouragement that starting and commissioning this third generation light
source at SSRL will continue to proceed smoothly. As has been the case
throughout the project, extraordinary teamwork has been a key component. A
dedication celebration is planned for Thursday, January 29 to recognize the
people who made the project successful as well as the state-of-the-art science
that SPEAR3 enables to SSRL's synchrotron user community. To learn more about
this celebration and to RSVP, visit the event website at:
http://www-conf.slac.stanford.edu/spear3/
A video which chronicles the installation activities is available at:
http://www-ssrl.slac.stanford.edu/movies/spear3-oct-03.mpg
Technical information on SPEAR3 is available at:
http://www-ssrl.slac.stanford.edu/spear3/
3. Holiday Greetings from the Director
It is with a great deal of pride that we can look back over a truly remarkable year of accomplishments that will define the future of SSRL and synchrotron radiation research at SLAC for decades to come - the completion and early commissioning success of SPEAR3, the commissioning and first experimental runs of SPPS, and the progress with project engineering and design of LCLS which will soon lead to construction. All this remarkable progress is due to the dedicated and creative talents of our wonderful staff at SSRL, colleagues at SLAC and those at many other laboratories working in partnership on many aspects of the above projects. As we near the holiday break, it is a time to reflect back on all these achievements while anticipating resuming general user operations at SSRL in a major way next year. We have a new on-site guest house (for which we thank Stanford University) which will make life here more comfortable and convenient for our users and other visitors. We continue to benefit from the support and encouragement provided by our funding agencies - DOE BES and BER and NIH. We have very good reasons to look forward to an equally exciting 2004! Let me close by wishing all of you - our staff, the SSRL users, and our many other colleagues and friends around the country, and indeed the world, the very best for a wonderful coming new year. — Keith
4. SLAC Scientific Policy Committee Fall Meeting
The fall Scientific Policy Committee (SPC) meeting, held December 5-6, focused on the high energy physics part of the SLAC program, but included a few presentations from SSRL to bring the committee up to date. The SSRL presentations at this SPC meeting were primarily on LCLS-related topics. Keith Hodgson gave an overview talk on SSRL describing the progress made on SPEAR3 with the successful completion of construction and now with the commissioning effort. He then described the status of the LCLS, providing an overview for Paul Emma's discussion on a new scheme for making ultrashort pulses with the LCLS. This is a novel technique that will make it possible to select an ~1 femtosecond slice of the LCLS beam (nominally 230 femtoseconds long in the baseline design) in a straightforward and inexpensive way. Finally, Jerry Hastings described the progress being made at the SPPS, which included a recent measurement on the electron beam length using transition radiation from a thin foil (for more details regarding the SPPS experiment see topic #6 below).
5. LCLS Update
(contact: John Galayda)
FY2003 was the first year of Project Engineering Design activities for the Linac Coherent Light Source. Despite receiving its first allocation ($6M) of a planned $36M design budget late in the year, the Project team put together a plan for early acquisition of key accelerator systems, starting in FY2005. The $30M plan was reviewed and approved by DOE in May 2003 (an approval of what is formally called critical decision 2A), and we are hoping to see these funds in the President's Budget for FY2005. For the present year, LCLS is expected to receive $7.5M of engineering design funds and $2M for R&D.
The Office of Science 20-Year Facilities Roadmap exercise provided what turned out to be an important milestone for LCLS. In February 2003, a subcommittee of the DOE Basic Energy Sciences Advisory Committee, co-chaired by Sunil Sinha and Geraldine Richmond, placed the LCLS in the highest priority category, after considering nearly a dozen proposals. As reported in the November Headlines, LCLS was subsequently assigned a very high priority by the Office of Science in the final version of the 20-Year Facility Roadmap, placing significant emphasis on LCLS in the future, and its ability to support a growing research program over the next two decades ( http://www.sc.doe.gov/Sub/Facilities_for_future/facilities_future.htm). The Project team has taken this to heart, and has been developing a roadmap for expansion of LCLS capabilities over the course of its operating life. The layout for the LCLS building has been revised to allow a more straightforward expansion of the facility at a later date. This will entail some increase in the project cost, which will be presented to DOE for approval around April 2004.
Expansion in scientific dimensions as well as in sheer capacity has also been given serious consideration. A group of SLAC scientists led by Max Cornacchia has prepared a report describing a wide variety of extensions of LCLS capability by a number of performance measures such as shorter pulse duration, extended wavelength range and higher average power. This report has been submitted for publication. Perhaps the most exciting of these options will be published soon in PRL. As mentioned above, Paul Emma, et al. have proposed a very promising and inexpensive method to produce ~1 femtosecond x-ray pulses with the LCLS. With ~1 femtosecond pulses, the LCLS can be used to explore ultrafast phenomena in chemistry with the time resolution of state-of-the-art chemical lasers and spatial resolution of x-rays.
6. Second SPPS Experimental Run Underway
(contacts: Jerry Hastings;
John Arthur)
The second run of the Sub-Picosecond Pulse Source for x-ray studies began on November 17, 2003. The team assembled to resume studies of the timing aspects of the electron beam and photon beam. In addition, characterization of the details of the photon beam were continued with the commissioning of a Be refractive lens provided by our DESY colleagues and their collaborators at University of Aachen. The Be lens provides a nicely focused beam of about 700 x 250 microns (horizontal. x vertical) with 2-3 x 106 photons per pulse. The measured energy spread of the photon beam from crystal analyzer rocking curves is 1.5%.
There have also been initial successes with the electron beam diagnostics. The electro-optic crystal diagnostics have clearly seen beam effects, although much work remains. The observed effects are most likely due to wakefields and not the fast transient from the electron bunch itself. Work continues in this area. Another diagnostic was also installed to measure the bunch length. A thin Ti foil (1 micron) inserted into the electron beam path produces coherent transition radiation in the micron wavelength range (wavelengths longer than the electron bunch length). This radiation exits the vacuum pipe thru a very thin (10 micron) mylar window. A Michelson interferometer was used to auto- correlate this beam. The measured bunch length was 160 femtoseconds FWHM. It should be noted that in this initial try, little attention was given to adjusting the linac parameters to give the shortest possible bunch, expected to be 80 fs FWHM. These measurements were performed in collaboration with the E-164 plasma wakefield acceleration experiment.
After a two-week break while SLAC is shut down, the SPPS will resume operation on January 8 and run through February 18. During this period, time-resolved diffraction experiments will continue as well as the installation of a Kirkpatrick-Baez micro-focusing mirror system provided by the ESRF. The sub-micron focal spot should achieve unprecedented x-ray peak power, comparable to that of an unfocused x-ray free electron laser beam.
7. 2004 Workshop on Ultrafast X-ray
Science
(contact: Ultrafast2004@lbl.gov)
A workshop on ultrafast x-ray science welcoming both ultrafast laser practitioners and accelerator-based x-ray researchers will be held April 28-May 1, 2004 in San Diego, CA. Workshop goals include: identifying scientific highlights and directions for the use of x-ray techniques; promoting the cross-fertilization of ideas at the common forefront of the laser and accelerator-based communities; and defining the source characteristics and ancillary equipment required for productive user facilities for ultrafast x-ray science. Attendance is limited to 200 persons. Please visit the meeting web site (http://Ultrafast2004.lbl.gov/) to indicate your interest by February 16, 2004.
8. User Administration Update
(contact: Cathy Knotts)
As mentioned above, there is good news to share -- several major milestones have been achieved to date, which provide encouragement that the start up effort will proceed smoothly. SPEAR3 staff will be working on equipment commissioning over the holiday period and into January/February. We expect that beam will be delivered to most beam lines in March, 2004. Before the first post-SPEAR3 schedule can be completed, however, there are a number of issues which impact scheduling that need to be resolved, such as approval of beam line operations by radiation physics. Staff will also need time to check and commission each beam line before they will be ready for users. We expect to have better estimates of how much time these activities will require in early January and will be incorporating the latest information into the schedule as it becomes available. We anticipate that schedules will distributed by early February. In the meantime, information on the status of beam lines can be found on the SSRL website at:
Holiday Closure: Stanford University, SLAC, and SSRL (with the exception of staff working on SPEAR3 startup and commissioning) will be closed for the upcoming holiday from December 20, 2003 through January 4, 2004.
__________________________________________________________________________
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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