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Last Updated: | 27 JUNE 2002 |
| Content Owner: | L. Dunn | |
| Page Editor: | L. Dunn |
**** **** **** * * * * * * **** **** **** * * * * * * **** **** * * **** HEADLINES - a digital monthly publication
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Contents of This Issue:
1. Science Highlight - VISA: A Milestone on
the Path Towards X-ray Free Electron Lasers
(contact: Heinz-Dieter Nuhn, nuhn@ssrl.slac.stanford.edu)
Results of the VISA (Visible to Infrared SASE Amplifier) experiment have recently been published in the May 2002 issue of Physics Review Letters. The experiment was carried out by a BNL-LLNL-SLAC-UCLA collaboration with major contribution by SSRL and within the broader framework of the LCLS R&D program funded by DOE-BES. The experiment, located in the Accelerator Test Facility (ATF) at the National Synchrotron Light Source at BNL, was designed to test the physics of Free-Electron Lasers (FELs) based on the Self-Amplified-Spontaneous- Emission (SASE) collective instability, and to demonstrate the possibility of producing an electron beam having characteristics close to those needed for the future Linac Coherent Light Source (LCLS).
VISA demonstrated a gain greater than 10^8, and an exponential growth rate of 18.5 cm. There is also clear evidence of saturation of the FEL intensity at about 3.6 m from the undulator entrance. The factor that makes the VISA experiment particularly significant is that its system requirements are very demanding and similar to those of the LCLS project.
One of the properties of a SASE FEL is the generation of nonlinear harmonics, which occurs only in the high gain and saturation regime. Both simulation and theory predict the intensity of the 3rd harmonic to be about 1% of the fundamental for an x-ray SASE FEL. This is about 8 orders of magnitude brighter than current third generation synchrotron radiation sources. The radiation is transversely coherent and provides the possibility for SASE FELs to have broad spectral coverage, i.e., it will make sub-Angstrom radiation available from the LCLS. The spectrum of SASE radiation was measured for the first time at the VISA experiment. The measurement confirms experimentally that high quality nonlinear harmonic spectra can be expected for future short wavelength SASE FELs driven by high-brightness electron beams. The VISA team will continue the work through this year with a detailed study of the dependence of radiation parameters on electron beam quality.
More information regarding this research can be found at:
http://www-ssrl.slac.stanford.edu/research/highlights_archive/visa.html
2. 29th Annual SSRL Users' Meeting is Coming
Soon!
(contact: Cathy Knotts, knotts@ssrl.slac.stanford.edu)
The 29th Annual SSRL Users' Meeting, which will be held on October 7-8, 2002, provides a forum for the presentation and discussion of research activities from SSRL users and the general synchrotron community. User research from SPEAR2 as well as discussions of new capabilities with SPEAR3 will be shared through invited talks and poster presentations. Dr. Yves Petroff (former Director General, ESRF) will give a keynote address on recent developments in synchrotron science.
Call for Abstracts:
Users are invited to submit abstracts for oral or poster presentation at the Users' Meeting. The deadline for abstracts for oral presentation is August 19 and September 23 for poster presentation. The poster session will be held the afternoon of Monday, October 7, and will include the student poster competition, with prizes to be awarded at the dinner later that evening.
Workshops:
In conjunction with the Annual Users' Meeting, four workshops will be held on Tuesday, October 8 and Wednesday, October 9.
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Information regarding abstract submission, workshops and registration for the Users' Meeting can be found at: http://www-ssrl.slac.stanford.edu/conferences/ssrl29/
3. The Summer Shutdown Approaches
(contact: Piero Pianetta, pianetta@slac.stanford.edu)
Preparations for SPEAR3 and ongoing maintenance activities have resulted in a shutdown schedule that seems as busy as the run itself. Shutdown activities this year will begin July 8th, and the rush will be on to get the work completed before start-up activities begin in September. User operations are expected to begin again on November 11th.
As in the past several shutdowns, the SPEAR concrete shielding tunnel will be modified in several locations for improved radiation containment and earthquake safety. To the user community the most obvious modification will be the relocation of the BL5 alcove and the addition of a new bending magnet beam line alcove between BL4 and BL5. Additional work includes modification of the tunnel as required to accommodate the new BL4 hybrid wiggler and modified walls and new roof shielding at the east pit.
The BL5 alcove reconstruction necessitated the temporary removal of major portions of BL5. While most of the components will be reinstalled in the fall, the staff waved goodbye to the BL5-2/3 Locust monochromator. The Locust will be replaced by a new spherical grating monochromator (SGM) as part of the SPEAR3 upgrade of BL5. The new SGM will cover the carbon K through transition metal L edges (250 - 1200 eV) with high resolution and throughput while the existing normal incidence monochromator (NIM) will continue to serve the correlated materials community in the low photon energy range. In the fall only the NIM on BL5-4 will be operational with the new SGM scheduled for winter installation and commissioning. When full operations of BL5 resume, the BL5-2/5-3 stations will be rechristened BL5-1/5-2 while BL5-4 will retain its SPEAR2 appellation.
With ongoing preparations to handle the higher powers provided by SPEAR3, the activity level on the SPEAR3 Beam Line Upgrade projects has been very high throughout the year. Recently installed liquid nitrogen-cooled crystal monochromators on BL6-2, 9-3, and 10-2 will allow the beam lines to run with full SPEAR3 power loading. During the shutdown multi-layers will be installed in the BL6-2 LN monochromator and improved crystal exchange mechanisms will be installed in all commissioned LN monochromators.
BL10-2 also stands to benefit from a new M0 mirror system to replace the mirror system that experienced a vacuum failure during the run. Rather than fix the old mirror system, fabrication of an improved 1.2 m long mirror system, originally planned as part of the SPEAR3 upgrade of the beam line, was expedited to permit installation a year early. Though the schedule is very tight, we anticipate the mirror system will be installed just prior to SPEAR startup in the fall. When installed, this mirror system will again permit focused operations of BL10-2 with the added benefits of improved thermal stability, increased vertical acceptance and enhanced focusing performance.
While the vacuum failure of a key mask associated with BL11-3 precluded installation of this new beam line in the spring, fabrication of a replacement mask is scheduled for completion during the summer. Following completion of this mask, the BL11-3 optics and masks will be installed in time for commissioning during the fall start up of SPEAR. Once commissioned, this beam line will provide 12.7 keV focused beam for thin film diffraction and macromolecular crystallography.
The beam line development work outlined above is just a sampling of the hundreds of activities expected to be completed by various SSRL groups this summer. Hence, shutdown projects are carefully managed to make the most efficient use of limited resources without compromising the quality of the work or the safety of staff and to ensure that user operations start back up on schedule in the fall!
4. Scientific Staff Positions Available at
SSRL
(contact: Danielle Harris, dwharris@slac.stanford.edu)
The Stanford Synchrotron Radiation Laboratory, a division of the Stanford Linear Accelerator Center (SLAC), is accepting applications for scientific staff positions in support of its programs in materials science. Candidates should have experience in condensed matter research using diffraction techniques such as surface x-ray scattering, powder diffraction, 4-circle diffractometry, anomalous x-ray scattering or inelastic x-ray scattering. Experience with the development or maintenance of a synchrotron radiation beam line is desirable. The SSRL scientific staff is partly engaged in facility development and support of x-ray research by external users. Up to one half of the time is available for individual research. The positions will be associated initially with scientific programs on the third generation storage ring SPEAR3. In the future, they may also involve next-generation x-ray facilities such as the Sub-Picosecond Photon Source (SPPS) and the Linac Coherent Light Source (LCLS), both under development at SLAC. Applicants should submit a letter of application with names and addresses of three references and a curriculum vitae by August 1, 2002, to dwharris@slac.stanford.edu, or to:
Stanford Synchrotron Radiation Laboratory
Stanford Linear Accelerator Center
Attention: Danielle Harris, M/S 69
2575 Sand Hill Road
Menlo Park, CA 94025-7015
USA
Stanford University is an Equal Opportunity Employer through Affirmative Action.
C. S. Raman, Assistant Professor at the University of Texas Medical School at Houston, has been selected as one of America's most promising biomedical researchers by the Pew Charitable Trusts. Dr. Raman and the other 19 junior faculty members at medical schools and research institutions receiving the Pew Scholar Award will each receive $240,000 over a four-year period to help support their research. Rebecca W. Rimel, the Trusts' president has stated "This longstanding program has encouraged scientists to push the limits of their fields by helping them expand their research in new directions and invigorate each other through stimulating exchange of ideas. We are privileged to back their courage and imagination." The long-term goal of Dr. Raman's lab is to understand the molecular bases of signal transduction at the cellular level using a multifaceted approach that includes high-resolution x-ray crystallography among other methods. According to Raman, "SSRL's generous support, by providing timely beam time, played a key role in my getting this award!"
Hendrik Ohldag's paper on "Understanding Magnetic Coupling at Antiferromagnetic /Ferromagnetic Interfaces - A Dichroism Spectromicroscopy Study" earned high marks at the Spring 2002 Materials Research Society Meeting. MRS Meeting graduate student papers are judged on several criteria including originality of the work and the timeliness of the results as well as the student's potential for future achievement in materials research. Hendrik's contribution earned him the Gold. Receiving this award is quite an honor, especially given the high level of excellence represented in the competition. Hendrik, who calls the University of Duesseldorf home, currently holds appointments in Jo Stohr's group at SSRL and at the ALS.
6. User Lodging Update
(contact: Cathy Knotts, knotts@ssrl.slac.stanford.edu)
If you were at SLAC this month, you may have noticed the flurry of activity related to the new User Lodging Facility. Heavy equipment has been busily moving a significant amount of dirt off the construction site to prepare for the new facility. All pedestrians, cyclists and motorized vehicles should be cautious and obey flagmen who will periodically be assisting to direct traffic around the construction site. When completed in June 2003, the 110-room facility will provide lodging for a combined SSRL/SLAC user community of 3,000 plus, but not all at one time - naturally.
7. Upcoming Events at SSRL and Elsewhere
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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: http://www-ssrl.slac.stanford.edu/
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