ALSNews Vol. 224, june 11, 2003
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
- Coherent Terahertz Synchrotron Radiation
- ALS Achieves Lowest Vertical Emittance in a Storage Ring
- Symposium Pays Tribute to Iran Thomas
- Be a Part of the ALS 10th Anniversary Celebration
- New User Advisories Issued
- Who's in Town: A Sampling of ALS Users
- Operations Update
1. COHERENT TERAHERTZ SYNCHROTRON RADIATION
by Art Robinson
(Contact: JMByrd@lbl.gov)
When the wavelength of synchrotron radiation is comparable to the length of an electron bunch in the storage ring, or the length of any structure on the bunch, the radiation from multiple electrons is in phase, resulting in a quadratic rather than the usual linear dependence of the power emitted on the number of electrons. Because the number of electrons participating in the coherence can be large (more than 1 million), the potential power enhancement is very large, making coherent synchrotron radiation (CSR) a subject of great interest to both synchrotron users and accelerator designers. However, the electromagnetic field associated with CSR can influence the motion of the electrons in the bunch, resulting in a self-amplified instability. This instability increases the electron bunch length and energy spread and represents a fundamental limitation on the performance of an electron storage ring. A joint Advanced Light Source/Berkeley Lab/University of California, Davis, team has now been able to observe and, for the first time, explain this instability.
Read the full story at http://www-als.lbl.gov/als/science/sci_archive/61coherent.html.
Publication about this research: J.M. Byrd, W. Leemans, A. Loftsdottir, B. Marcelis, M.C. Martin, W.R. McKinney, F. Sannibale, T. Scarvie, and C. Steier, "Observation of broadband self-amplified spontaneous coherent terahertz synchrotron radiation in a storage ring," Phys. Rev. Lett. 89, 224801 (2002).
2. ALS ACHIEVES LOWEST VERTICAL EMITTANCE IN A
STORAGE RING
(Contact: CSteier@lbl.gov)
Emittance is one of the key parameters that describe a particle beam circulating in a storage ring. Defined as the product of the beam size and beam divergence in the respective directions, there are both horizontal and vertical emittances. Decreasing the storage ring's vertical emittance results in a higher brightness in synchrotron light sources and a higher luminosity in particle colliders. Through careful analysis and characterization of the storage ring, ALS accelerator scientists have reduced the ALS vertical emittance to 5 picometer-radians during accelerator physics studies. This is the lowest emittance value ever realized in any storage ring.
In the vertical plane, the emittance is determined by magnetic and alignment imperfections in the storage ring. To compensate for these imperfections, the scientists adjusted the power supplies of 18 skew quadrupoles--magnets intentionally tilted by 45 degrees around the longitudinal axis and used for coupling control and vertical dispersion correction. The resulting vertical emittance, less than 0.1% of the horizontal emittance, corresponds to a vertical beam size of about 5 microns in the straight sections of the storage ring, where the undulators that produce the brightest synchrotron radiation are located. This emittance is a factor of 25 to 30 lower than the emittance during ALS user operations and about a factor of 2 smaller than the best values achieved in earlier studies at other storage rings around the world, such as ESRF in France, SLS in Switzerland, and Spring-8 and ATF in Japan. Such low emittances meet the values required for the next generation of linear collider damping rings, and at the ALS, very small vertical emittances will be especially important for those spectroscopy studies in which the highest possible resolution is important.
3. SYMPOSIUM PAYS TRIBUTE TO IRAN THOMAS
(Contact: GFKrebs@lbl.gov)
ALS Division Director Daniel Chemla was among those paying tribute to the late Iran Thomas of the Department of Energy's Office of Science at a special symposium held May 28-29. "BES Science 2018: A Future Retrospective" was held at the Sheraton National Hotel in Arlington, Virginia, in honor of Thomas, a long-time director in the Office of Basic Energy Sciences (BES) who passed away on February 28. During his tenure, Thomas enabled the development of new and innovative research programs and some of the world's most powerful scientific user facilities, including the ALS. Speakers were asked to place themselves in the year 2018, the year of Iran's 80th birthday, 15 years into the future. In providing a "retrospective" of the years from 2003 to 2018, the speakers were to challenge both the scientific communities and the federal agencies to set a course to achieve this future.
The symposium began with an exhibit of posters and displays of BES-supported Nobel Prizes and BES user facilities. The ALS contributed a poster showing the progress of science at the ALS from the past and into the future. The poster session was followed by a dinner during which national user facility directors reminisced about Iran Thomas. The following day, the talks began with a welcome by Pat Dehmer, Director of BES. The morning session, "BES Science," was chaired by Berkeley Lab Director Charles Shank, and ALS Division Director Daniel Chemla was the first speaker of the morning with a talk titled "Enabling BES Science: A retrospective on the growth of BES science in materials sciences, chemistry, and biosciences." The talk extrapolated from active research areas with significant advances in which BES and BES facilities played a critical role: the high-Tc superconductivity saga; carbon nanotubes and cohort; bio-materials, -machines, and -systems; and quantum coherence and macroscopic ordering in condensed matter. The full program and several of the presentations and remarks are available online at http://www.ornl.gov/%7Egrg/BES_sym/.
4. BE A PART OF THE ALS 10TH ANNIVERSARY CELEBRATION
(Contact: als10years@lbl.gov)
Do you have stories about the early years of the ALS, or historical insights (and hindsights) about its construction? Or were you there when the first light shone through a beamline? If you have a story to tell or a photo to show, let us know at als10years@lbl.gov.
We would also like to hear from anyone who would like to participate in helping to plan the celebration. Send in your suggestions and contact information to als10years@lbl.gov.
5. NEW USER ADVISORIES ISSUED
(Contact: EJMoxon@lbl.gov)
Two new ALS User Advisories have recently been posted to the ALS Web site at http://www-als.lbl.gov/als/user-advis/. Advisories are short information sheets that provide safety guidelines and procedures, equipment specifications, and contact information for a variety of issues concerning ALS users. The new advisories are the following:
ALS User Advisory No. 17: Electrical Safety During Beamline Bakeouts. Details the procedures and proper equipment required for safely baking out vacuum vessels before they are used at the ALS.
ALS User Advisory No. 18: The Use of Biological Materials at the ALS. Provides a step-by-step guide for users intending to use biological materials (biologicals) in experiments at the ALS. All biologicals must be registered and approved by Berkeley Lab's Institutional Biosafety Committee and the ALS before they may be brought to the ALS. Included in the advisory are instructions for registering materials; guidelines for the proper shipping, storage, and handling of biologicals; and links to Berkeley Lab's Biosafety Manual and to the Biosafety Registration Form.
6. 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
Raymond Jeanloz (Univ. of California, Berkeley)
John Bradley (Lawrence Livermore National Laboratory)
T.J. Wilkinson (Berkeley Lab)
Ted Raab (Carnegie Institution of Washington)
Hoi-Ying Holman (Berkeley Lab)
Beamline 4.0.2
Chuck Fadley (Univ. of California, Davis, and Berkeley Lab)
Steve Cramer (Univ. of California, Davis, and Berkeley Lab)
Beamlines 5.0.1, 5.0.2, 5.0.3
Thomas Poulos (Univ. of California, Irvine)
Mark Knapp (Roche Bioscience)
Steven Jordan (Amgen)
Ed Berry (Berkeley Lab)
Barry Stoddard (Fred Hutchinson Cancer Research Center)
David Christianson (Univ. of Pennsylvania)
Marc Whitlow (Berlex Biosciences)
Ian Wilson (The Scripps Research Institute)
Glen Spraggon (Novartis Institute for Functional Genomics)
Ning Zheng (Univ. of Washington)
Richard Brennan (Oregon Health & Science University)
Duncan McRee (Syrrx, Inc.)
Beamline 7.0.1
Z.Q. Qiu (Univ. of California, Berkeley)
Byron Freelon (Berkeley Lab)
Miquel Salmeron (Berkeley Lab)
Beamline 7.3.1.1
Jo Stohr (Stanford Synchrotron Radiation Laboratory)
Hiroo Hashizume (Nara Institute of Science and Technology, Japan)
Geoffrey Thornton (Manchester Univ., UK)
Beamline 8.0.1
Thomas Callcott (Univ. of Tennessee)
Beamlines 8.2.1, 8.2.2, 8.3.1
Kenan Garcia (Stanford Univ.)
Jennifer Doudna (Univ. of California, Berkeley, and Berkeley Lab)
Axel Brunger (Stanford Univ.)
John Kuriyan (Univ. of California, Berkeley, and Berkeley Lab)
Pamela Bjorkman (California Institute of Technology)
Joseph Mougous (Univ. of California, Berkeley)
Beamline 10.0.1
Fred Schlachter (Berkeley Lab)
Z.-X. Shen (Stanford Univ.)
Nora Berrah (Western Michigan Univ.)
Beamline 10.3.2
Peter Nico (California State Univ., Stanislaus)
Hoi-Ying Holman (Berkeley Lab)
7. OPERATIONS UPDATE
(Contact: Lampo@lbl.gov)
For the user run of May 29 - June 1, the beam reliability (time delivered/time scheduled) was 85%. Of the scheduled beam, 77% was delivered to completion without interruption. Repair of a water-flow switch requiring controlled access, tuning problems, and chicane magnet control problems contributed to loss of beam during this short run.
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 (ALS-CR@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. A Web page showing the ring status in real time can be found at http://www-als.lbl.gov/als/status/.
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-875
Editors: lstamura@lbl.gov, alrobinson@lbl.gov, amgreiner@lbl.gov,
ejmoxon@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.