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Contents Laser seeding yields high-power coherent terahertz radiation Controlling graphene’s electronic structure User Services Office provides seamless link to ALS and Lab Memorial service for Jim Patel Save the date: 2007 Users’ Meeting, October 4–6 News Links Building the nuclear pore piece by piece Judges take crash course at Laboratory Operations For the user runs from Beam reliability*: 94.6% Completion**: 87.4% There were no significant interruptions. *Time delivered/time scheduled Questions about beam reliability should be sent to Dave Richardson (DBRichardson@lbl.gov). Requests for special operations use of the “scrubbing” shift should be sent to Rick Bloemhard (ALS-CR@lbl.gov, x4738) by 1:00 p.m. Friday. More Info To subscribe/unsubscribe, email ALSNews@lbl.gov. EDITORS DESIGNER LBNL/PUB-948 (2007) This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Disclaimer. |
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Contact: Roger Falcone, RWFalcone@lbl.gov
Director Zerhouni’s tour of the Berkeley Center for Structural Biology beamlines included a look at Beamline 5.0.3’s new 315r CCD detector and the Berkeley Automounter System (developed by Thomas Earnest and colleagues at Berkeley Lab). Dr. Adams described the upcoming upgrades to the 8.2.1 and 8.2.2 beamlines, and Dr. Zerhouni responded enthusiastically about the prospects for increased automation of crystallographic experiments.
NIH Director Elias Zerhouni, NCXT Director Carolyn Larabell, and Berkeley Lab Deputy Director Graham Fleming at the NCXT. As part of his tour, Director Zerhouni also inspected the NCXT’s newly constructed soft x-ray microscope. This is the first such microscope to be designed and built specifically for biological and biomedical imaging. (The NCXT is an NIH National Center for Research Resources that also receives joint funding from the Department of Energy, Office of Biological and Environmental Research.)
Laser seeding yields high-power coherent terahertz radiation Contact: Fernando Sannibale, FSannibale@lbl.gov Researchers at Berkeley Lab have been exploring the ways coherent synchrotron radiation (CSR) is generated in electron storage rings when femtosecond lasers are used to carve out ultrafast x-ray pulses by femtoslicing (see previous highlight published in ALSNews Vol. 271, “Tailored Terahertz Pulses from a Laser-Modulated Electron Beam.” In their most recent work, the researchers reported the first observation of seeding an instability of the electron beam by the laser, and they presented a physical model that shows how this occurs under the proper conditions. Such a mechanism makes it possible to control the instability onset and to exploit its gain for the generation of pulses of terahertz CSR of unprecedented power. Terahertz radiation with a wavelength from about 1 cm to about 100 microns between the microwave and the infrared would provide access to a large number of fundamental phenomena. To mention only some of them: excited electrons orbit, small molecules rotate, proteins vibrate, superconducting energy gaps resonate, and gaseous and solid-state plasmas oscillate at terahertz frequencies. But generating terahertz radiation is ordinarily a challenging task for any kind of source, including storage-ring-based synchrotron light sources. The new findings by the ALS group could represent a significant step toward satisfying the need for powerful terahertz sources. Read more…
Publication about this research: J.M. Byrd, Z. Hao, M.C. Martin, D.S. Robin, F. Sannibale, R.W. Schoenlein, A.A. Zholents, and M.S. Zolotorev, “Laser seeding of the storage-ring microbunching instability for high-power coherent terahertz radiation,” Phys. Rev. Lett. 97, 074802 (2006). Controlling graphene’s electronic structure Contact: Eli Rotenberg, ERotenberg@lbl.gov Graphene, because of its unusual electron properties, reduced dimensionality, and scale, has enormous potential for use in ultrafast electronic transistors. It exhibits high conductivity and an anomalous quantum Hall effect (a phenomenon exhibited by certain semiconductor devices at low temperatures and high magnetic fields). Among its novel properties, graphene’s electrical charge carriers (electrons and holes) move through a solid with effectively zero mass and constant velocity, like photons. Graphene’s intrinsically low scattering rate from defects implies the possibility of a new kind of electronics based on the manipulation of electrons as waves rather than particles. The primary technical difficulty has been controlling the transport of electrical charge carriers through the sheet. This area of research is known as bandgap engineering. While bandgap engineering is the basis of semiconductor technology, it is only now being applied to graphene. Using angle-resolved photoemission spectroscopy (ARPES) at ALS Beamline 7.0.1, a team of scientists from the ALS and Germany characterized the electronic band structure and successfully controlled the gap between valence and conduction bands in a bilayer of graphene thin films deposited on a substrate of silicon carbide. This was done by doping one sheet with adsorbed potassium atoms, creating an asymmetry between the two layers. Read more…
Publication about this research: T. Ohta, A. Bostwick, T. Seyller, K. Horn, E. Rotenberg, “Controlling the Electronic Structure of Bilayer Graphene,” Science 313, 5789 (2006). User Services Office provides seamless link to ALS and Lab Contacts: Gary Krebs, GFKrebs@lbl.gov; Jeff Troutman, JPTroutman@lbl.gov
User Services Office staff. Clockwise from top left: Ken Winters, Jeff Troutman, Olga Poblete, Sharon Fujimura, and Carmen Escobar. Not pictured: Valerie Wysinger. The goal of the User Services Office is to provide a seamless interface between the user and the ALS and Berkeley Lab while ensuring the highest safety standards. This six-member team offers the following administrative services to the users during their stay.
In addition, the User Services Office administers critical databases for users to record their experiments and publications:
The ALS Users Services Office, located in the mezzanine of Building 6 (Room 2212), is open from 8 a.m. to noon and 1 to 5 p.m. Stop by, or contact them by phone (510-486-7745) or email (alsuser@lbl.gov). Other user resources include the User Services Office Web page and the User Guide. Memorial service for Jim Patel Last month, Jamshed (Jim) R. Patel, ALS user and dear colleague to many, died at his home in Menlo Park at the age of 81. Jim was one of the key players in the development of x-ray microdiffraction at the ALS, and his sharp mind and kind and gentle nature will be deeply missed. A memorial service will be held for Jim on Saturday, June 9th, at 3:00 p.m., at Saint Raymond’s Catholic Church, located at 1100 Santa Cruz Avenue, Menlo Park, CA. All who wish to remember Jim are welcome to attend (see “In Memoriam: The ALS remembers Al Baez and Jim Patel,” ALSNews Vol. 274). Save the date: ALS Users’ Meeting, October 4–6 It’s not too early to start planning to attend this year’s ALS Users’ Meeting. The meeting will be held on site at Berkeley Lab—from Thursday, October 4, to Saturday, October 6—and will offer a variety of invited talks, workshops, and selected science highlights. Ongoing facility projects such as top-off mode and the construction of the new ALS user support and the ALS user housing buildings will be discussed. The topical workshops are great opportunities to network, discuss recent successes, and combine efforts to address shared experimental challenges. The workshop topics are actively coming together now, and both suggestions and volunteer leaders are welcome. Please contact the meeting chairs Peter Fischer (PJFischer@lbl.gov) and Ken Goldberg (KAGoldberg@lbl.gov) for additional information or if you are interested in proposing a workshop for the meeting. |
On March 31st, the Director of the National Institutes for Health (NIH), Elias Zerhouni, visited Berkeley Lab and the UC Berkeley campus. As part of his visit, he toured the ALS with Graham Fleming (Berkeley Lab Deputy Director), Roger Falcone (ALS Director), Paul Adams (Head of the 
Dr. Zerhouni, a radiographer with considerable experience in full-body CAT scanning, was enormously enthusiastic about the potential of the new technique and told the assembled group, “I love this stuff!” Nearing the end of the NCXT tour, Mark Le Gros, the Berkeley Lab scientist responsible for the design and construction of the new microscope, showed Director Zerhouni his latest innovation, an instrument for a technique known as correlated microscopy. At the end of his inspection of the NCXT beamline, Director Zerhouni, with overall responsibility for the NIH’s $29 billion budget, beamed and said “this was money well spent!”
