Contents of this Issue:
1. Science Highlight —
Understanding the Mysteries of High-temperature Superconductors
(contact: Zhi-xun Shen,
zxshen@stanford.edu)
High-temperature superconductors (HTSCs) operate in mysterious ways, but scientists are starting to understand their peculiarities by using a state-of-the-art spectroscopy system at SSRL. One of the biggest mysteries is how a material that starts as an insulator - which does not conduct electricity - can become a high-temperature superconductor after being doped with electric carriers. Researchers Kyle Shen and Donghui Lu (both SSRL), working in Zhi-xun Shen's group at SSRL and Stanford, looked at the evolution from insulator to superconductor by studying an HTSC material at different doping concentrations. The team used angle-resolved photoemission spectroscopy (ARPES), a method of probing the electronic states in solids.
Their results, published in Science Feb. 11, contribute to creating a fundamental understanding of the perplexing physics in the mysterious HTSCs. Scientists hope to develop a theory explaining why the materials can be superconducting at a temperature much higher than conventional superconductors, and thereby how to improve the materials, currently too brittle for widespread use. The ARPES data revealed electronic states in the two-dimensional momentum space that are much stronger along the direction diagonal to the copper-oxygen bond (the "nodal" direction) than the direction parallel to the copper-oxygen bond (the "anti-nodal" direction), even through the anti-nodal direction is where the superconducting gap is the largest. The results show that the difference in momentum directions is important to the electronic structure, and put strong constraints on proposed HTSC models.
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To learn more about this research see:
http://www-ssrl.slac.stanford.edu/research/highlights_archive/HTSC.html or http://www-ssrl.slac.stanford.edu/research/highlights_archive/HTSC.pdf |
2. XLAM-GLAM Materials Science Review in
Washington DC
(contact: Jo Stöhr,
stohr@slac.stanford.edu)
A review of the materials science program associated with the X-ray Laboratory for Advanced Materials (XLAM) at SSRL and the Stanford University campus-based Geballe Laboratory for Advanced Materials (GLAM) took place at DOE-BES headquarters on March 17. The review was conducted by Harriet Kung, the Director of the Division of Materials Sciences and Engineering, and her staff. On the Stanford side, the meeting was attended by the SSRL Director and Deputy Director, Keith Hodgson and Jo Stöhr, and by Mac Beasley and Z.-X. Shen of GLAM (Director and Deputy Director, respectively, of GLAM). Jo Stöhr presented the SLAC/SSRL perspective and Z.-X. Shen gave an overview of the GLAM perspective of the joint materials science programs at XLAM. Both talks emphasized the unique environment of materials science at Stanford based on a strong coupling of SSRL and Stanford and the seminal role of SSRL and XLAM faculties. The presentations also provided a vision of the future which included new facilities on SPEAR3 and the expansion of the Stanford Ultrafast Science Center.
3.
Applications for Stanford-Berkeley Physical Sciences Summer School Due by May 8
(contact: Anders Nilsson,
nilsson@slac.stanford.edu)
The website for the fourth Stanford-Berkeley summer school (June 13-17) has been updated and applications are now being accepted. The deadline for submittal is May 8. This summer school, which will be held at SSRL, will be limited to approximately 40 graduate students, with a preference for those pursuing doctoral research in the physical sciences in which synchrotron radiation is expected to play a significant role. The summer school is jointly sponsored by UC Berkeley, Stanford University, LBNL, and SSRL. Visits to both the Advanced Light Source (ALS) in Berkeley and SSRL will be included, with opportunities to interact with the professional staff and graduate students at both facilities. This summer school will provide basic lectures on the synchrotron radiation process, requisite technologies, and a broad range of scientific applications presented by professors and scientists from these organizations and their user communities. Further details can be found at: http://www-ssrl.slac.stanford.edu/sbsummerschool/
4.
SSRL Users' Organization Executive Committee March Meeting
(contact: Glenn Waychunas, SSRLUOEC
Chair, gawaychunas@lbl.gov)
The SSRL Users' Organization Executive Committee (SSRLUOEC) met on Friday, March 18. The meeting included presentations by Keith Hodgson, Glenn Waychunas, and Cathy Knotts. Plans for the 32nd Annual SSRL Users' Meeting (to be organized by Joy Andrews, UCEB, and Clyde Smith, SSRL) were discussed -- if you have suggestions for session topics, speakers, or workshops, please forward these to Cathy Knotts. Plans for annual awards were also discussed, including the Farrel Lytle Award and the W.E. Spicer Young Investigator Award; nominations for these awards will be due in early August, so start to think about potential candidates that you might want to nominate. Representatives from the four DOE synchrotron facilities are planning a trip to Washington, DC on April 8 to raise awareness about the broad range of research conducted at these facilities as well as the need to support basic sciences in general. More information from the SSRLUOEC will be shared shortly.
5.
Visitors from the Photon Factory and the Chalmers University of Technology
Professor Toshio Kasuga, Head of the Light Source Division at KEK in Japan, together with Drs. Takashi Obina (controls group) and Tsukasa Miyajima (orbit and magnet group), visited SLAC and SSRL during the week of March 21 to discuss accelerator-related development plans for the 2.5-GeV Photon Factory storage ring, the 6.5-GeV AR ring, and future linac-based light sources, including an SPPS-like facility operating at ~3 GeV and a short-pulse X-ray FEL operating at 8 GeV (after the end of KEK-B Factory operation). The group met with SSRL accelerator physicists and engineers to discuss SPEAR beam monitoring and orbit feedback systems, and the PF optical monitors. They also met with SLAC and SPPS staff to discuss multi-bunch feedback system and short-pulse linac light source design.
Lars Börjesson, Chalmers University of Technology in Gothenburg, and Secretary General to the Committee for Research Infrastructure, visited SSRL/SLAC on Thursday, March 24. His visit included presentations and discussions on the SPPS, LCLS and the HHG source development at Berkeley, as well as the Ultrafast Science Center and the science that will become possible in the soft and hard x-ray regime.
6.
SPEAR3 "Breathes" in Response to Temperature Changes
(contact: Neil Calder,
neil.calder@slac.stanford.edu)
As the sun rises, the SPEAR3 synchrotron facility at SLAC expands. The change
is microscopic, but it doesn't escape the SPEAR3 feedback regulation system.
The lattice of beam-focusing magnets expands radially with the structure, but
the beam stays put, becoming slightly displaced. To stay centered within the
magnets, the beam must also expand. An array of monitors tracks the beam's
position, and relays information to the feedback system. The signal cycles
every six seconds, instructing the radiofrequency to adjust by about half a
hertz per cycle. This allows the beam to "breathe" with daily and seasonal
changes in temperature.
http://www2.slac.stanford.edu/tip/2005/mar04/spear3.htm
7.
Clyde Smith to Give SLAC Public Lecture on April 26
The SLAC Public Lecture Series has been incredibly popular, drawing 300-400
attendees for each presentation. SSRL Scientist Clyde Smith will give the next
public lecture, "Smarter Drugs: How Protein Crystallography Revolutionizes Drug
Design", on Tuesday, April 26, at 7:30 pm.
http://www2.slac.stanford.edu/lectures/upcoming.htm
8.
User Administration Update
(contacts: Cathy Knotts,
knotts@slac.stanford.edu; Lisa Dunn, lisa@slac.stanford.edu)
Proposal Submission: If you would like to conduct experiments at SSRL, please consider submitting a new X-ray and VUV proposal by the May 1 deadline, or submit a new Macromolecular Crystallography proposal by the July 1 deadline (proposals submitted by these dates will be eligible for beam time during the 2006 user run, which is expected to begin ~November 28, 2005). For more information on the proposal submittal, review and scheduling process, visit: http://www-ssrl.slac.stanford.edu/users/user_admin/guide.html
Requirements Before Arrival: Instructions for proposal spokesperson and
on-site
users became more complicated within the last year, and this information may
not be filtering down to all users because many are still arriving unaware of
the requirements or without having completed the necessary documentation. As a
reminder, everyone who utilizes the experimental facilities here (e.g., all
on-site users) must do the following before their first visit each run year:
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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 Sciences. Additional information about SSRL and its operation and schedules is available from the SSRL WWW site.
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