ALSNews Vol. 213, December 11, 2002
ALSNews is a biweekly electronic newsletter to keep users and other interested parties informed about developments at the Advanced Light Source, a national user facility located at Lawrence Berkeley National Laboratory, University of California. To be placed on the mailing list, send your name and complete internet address to ALSNews@lbl.gov. We welcome suggestions for topics and content.
Previous Issues are available.
Table of Contents
- Experimental Progress Toward CSR Source
- Latest SRI 2003 Information Available Online
- ALS Awards and Honors
- Berkeley Lab to Close for Holidays
- Who's in Town: A Sampling of ALS Users
- Operations Update
1. EXPERIMENTAL PROGRESS TOWARD CSR SOURCE
(Contacts: MCMartin@lbl.gov, JMByrd@lbl.gov)
A high-power coherent synchrotron radiation (CSR) source in the THz range could enable a number of new scientific research directions, including the study of low-energy phenomena in condensed matter systems; direct nondestructive imaging techniques for medical, technological, and security applications; novel nonlinear regimes in materials; and ultrafast time-resolved studies of the dynamical properties of chemical reactions and correlated electron systems. The ALS is currently developing the scientific case and a plan for a storage-ring-based CSR source. Recent high-profile experiments have brought the goal of a CSR source several steps closer to reality.
Super-radiant, temporally coherent synchrotron radiation can significantly enhance the available photon flux at far-infrared wavelengths, a traditionally difficult frequency range. At wavelengths longer than the electron bunch length, the individual accelerated electrons radiate in phase. This means that the radiative power in this long-wavelength regime is proportional to the square of the number of electrons, as opposed to the linear relationship that is well known with conventional (incoherent) synchrotron light sources. This effect is usually not observed in synchrotron storage rings since electron bunch lengths are usually longer than the vacuum chamber dimensions, meaning any CSR is screened. However, even at very low stored beam currents, the number of electrons is quite large, so the resultant flux enhancement is huge.
To demonstrate the very high powers possible from CSR in the THz frequency range, ALS scientists Michael Martin and Wayne McKinney collaborated with researchers at Jefferson Lab (Virginia) and Brookhaven National Lab (New York) to measure the CSR power and spectrum from a new energy recovery linac (ERL) located at Jefferson Lab. This ERL is capable of accelerating ~500-fs electron bunches with a relatively high 75-MHz repetition rate and, therefore, a relatively high average current due to the use of superconducting rf accelerating cavities. At the long-wavelength end of the spectrum, the intensity gain using this CSR source compared to a conventional thermal infrared source was observed to be about six orders of magnitude in intensity, in good agreement with predictions. These results were recently published in Nature 420, 153 (2002).
Another important step toward a storage-ring CSR source is to fully understand just how tightly electron bunches can be compressed and how much current can be stored stably at these short bunch lengths. Studies at several synchrotron facilities, including the ALS, have found that at quite high single-bunch currents, the electron bunches become unstable and begin to emit bursts of CSR. Recently, a team led by John Byrd and Fernando Sannibale of the ALS Accelerator Physics Group made detailed characterizations of the ALS beam parameters when this bursting regime occurs, and these measurements were compared to a model predicting the onset of self-amplified microbunching in stored electron bunches. With no adjustable parameters, there was excellent agreement, showing that we are beginning to understand the mechanism behind this bursting instability threshold. These results were recently published in Phys. Rev. Lett. 89, 224801 (2002). All of these experimental results are now being used with recently developed modeling capabilities to determine optimized parameters for achieving stable high-power CSR in a storage ring source.
2. LATEST SRI 2003 INFORMATION AVAILABLE ONLINE
(Contacts: HAPadmore@lbl.gov, stohr@ssrl.slac.stanford.edu)
A wealth of new information concerning the 2003 International Conference on Synchrotron Radiation Instrumentation (SRI 2003) is now posted at the official conference Web site (http://www.sri2003.lbl.gov/). One of the largest and most important synchrotron-related meetings in the world, SRI 2003 will be hosted jointly by the ALS and the Stanford Synchrotron Radiation Laboratory (SSRL) and is being chaired by Howard Padmore (ALS) and Jo Stohr (SSRL). The conference will be held August 25-29, 2003, at the Yerba Buena Center for the Arts in downtown San Francisco. The updated SRI 2003 Web site includes information about the venue, accommodations, abstract submission, and registration. A notice of the second announcement and direction to the Web site will be sent by email in the next few days to over 10,000 people who are currently on the mailing list. Organizers are planning to keep meeting transactions (such as announcements, abstract submission and review, and registration) as electronic as possible by using email and the Web. The conference proceedings will be published through the American Institute of Physics.
The ALS is pleased to acknowledge those in its orbit who have been elected to Fellowship this year in the American Physical Society. ALS Users' Executive Committee member Dennis Lindle (University of Nevada, Las Vegas) was cited for "seminal contributions in atomic and molecular photoionization and the polarization of x-rays induced by photoionization of atoms and molecules." In particular, the nomination letter mentioned his "world class" research and leadership role at the ALS, "one of the finest UV/x-ray light sources in the world." Former ALS Accelerator Physics Group Leader Alan Jackson (Berkeley Lab) was recognized for "pioneering work in the development and construction of 3rd generation synchrotron radiation sources." Alan was the deputy director of the ALS construction project and guided the accelerators through construction, commissioning, and the generation of first light in 1993 and oversaw accelerator physics activities for six years thereafter. He is currently serving as Technical Director for the Australian Synchrotron Project. User Marjorie Ohlmstead (University of Washington) was recognized for "innovative studies of interface formation between dissimilar materials, especially the competition between thermodynamic and kinetic constraints in controlling morphologies and properties of heterostructures." Another user, Denis Cubaynes (Paris-Sud University), was cited for "his achievements in the field of atomic photoionization of laser-excited atoms and for having brought new insights into the creation and the properties of hollow atoms."
The APS Fellowship Program was created to recognize members who have made advances in knowledge through original research and publication or made significant and innovative contributions in the application of physics to science and technology. Each year, no more than one-half of one percent of the membership are recognized by their peers for election to the status of Fellow. This year a total of 192 new Fellows were elected. Congratulations to all on being recognized by the APS for your extraordinary contributions to science!
4. BERKELEY LAB TO CLOSE FOR HOLIDAYS
Berkeley Lab will close on the evening of December 23 and reopen on the morning of January 2. During the closure, the Lab will shut down as much heating and ventilating equipment as possible to reduce costs. However, power to the ALS building will be maintained, and the last user run of 2002 extends to 10:30 p.m. on December 23. Anyone having to work on site during this time will need a current ID badge and parking permit to gain access. The User Services Office will provide badging only until 4 p.m. on December 23. Unbadged visitors must have been verified and cleared through the gate by an appropriate host prior to entry. The first user run of 2003 will be January 4 - 6. The next issue of ALSNews will be published on January 22. We wish you all a pleasant and relaxing holiday season!
5. WHO'S IN TOWN: A SAMPLING OF ALS USERS
Following are some of the experimenters who will be collecting data during the next two weeks at the ALS.
Beamline 1.4.3
Hoi-Ying Holman (Berkeley Lab)
Dan Fried (Univ. of California, San Francisco)
Ted Raab (Carnegie Institution of Washington)
Beamline 4.0.2
Jo Stohr (Stanford Synchrotron Radiation Laboratory)
Chuck Fadley (Univ. of California, Davis, and Berkeley Lab)
Beamlines 5.0.1, 5.0.2, 5.0.3
Shengfeng Chen, Jinyu Liu, Dong Hae Shin (Berkeley Structural Genomics
Center)
Dan Knighton, Marc Deller, Samantha Greasley, Hans Parge (Agouron/Pfizer-La
Jolla)
Russell Doolittle, Justin Kollman (Univ. of California, San Diego)
Marc Knapp (Roche Bioscience)
Steve Damo, Seok-Yong Lee (Berkeley Lab)
Will Somers, Kevin Parris (Wyeth-Ayerst Research)
Gyorgy Snell (Syrrx, Inc.)
Beamline 7.0.1
James Allen (Univ. of Michigan)
Stuart Parkin (IBM Almaden Research Center)
Jim Tobin (Lawrence Livermore National Laboratory)
Steve Kevan (Univ. of Oregon)
Beamline 7.3.1.1
Z.Q. Qiu (Univ. of California, Berkeley)
Gary Mitchell (The Dow Chemical Company)
Stephen Urquhart (Univ. of Saskatchewan, Canada)
Beamline 8.0.1
David Shuh (Berkeley Lab)
Beamline 8.2.1
Jay Nix, Sergei Trakhanov, Martin Laurberg (Univ. of California, Santa
Cruz)
Beamline 8.2.2
Doug Davies, George Wisedchaisri, Jan Abendroth (Univ. of Washington)
Joseph Mougous (Univ. of California, Berkeley)
Beamline 8.3.1
Partho Ghosh, Lori Buetow, Jonathan Mikolosko (Univ. of California, San
Diego)
Beamline 10.0.1
Nora Berrah (Western Michigan Univ.)
Xingjiang Zhou (Berkeley Lab)
Beamline 10.3.2
Alain Manceau (Univ. Joseph Fourier, France)
Andrei Istratov (Berkeley Lab)
6. OPERATIONS UPDATE
(Contact: Lampo@lbl.gov)
For the user runs of November 20 - 26 and December 3 - 8, the beam reliability (time delivered/time scheduled) was 96%. Of the scheduled beam, 88% was delivered to completion without interruption. There were no significant outages.
Long-term and weekly operations schedules are available on the Web (http://www-als.lbl.gov/als/schedules/index.html). Requests for special operations use of the "scrubbing" shift should be sent to Bruce Samuelson (BCSamuelson@lbl.gov, x4738) by 1:00 p.m. Friday. The Accelerator Status Hotline at (510) 486-6766 (ext. 6766 from Lab phones) features a recorded message giving up-to-date information on the operational status of the accelerator.
ALSNews is a biweekly electronic newsletter to keep users informed about developments at the Advanced Light Source, a national user facility located at Ernest Orlando Lawrence Berkeley National Laboratory, University of California. To be placed on the mailing list, send your email address to ALSNews@lbl.gov. We welcome suggestions for topics and content. Submissions are due the Friday before the issue date.
LBNL/PUB-863
Editors: lstamura@lbl.gov, alrobinson@lbl.gov, amgreiner@lbl.gov
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-AC03-76SF00098.