1. LASER TIME SLICING PROMISES ULTRAFAST TIME RESOLUTION
by Art Robinson
(Contact: RWSchoenlein@lbl.gov)

Scientists from Berkeley Lab have generated 300-femtosecond pulses of bend-magnet synchrotron radiation at the Advanced Light Source with the aid of a laser "time-slicing" technique. Their proof-of-principle experiment demonstrates that this technique is a viable one for producing ultrashort pulses of x rays. An ALS bend-magnet beamline (see item 2 below) will soon be commissioned that will be dedicated to time-resolved x-ray diffraction, EXAFS, and other techniques capable of probing the long-range and local structure of matter on a femtosecond time scale.

Read the full story at http://www-als.lbl.gov/als/science/sci_archive/femto2.html.html.

Publication about this research: R.W. Schoenlein, S. Chattopadhyay, H.H.W. Chong, T.E. Glover, P.A. Heimann, C.V. Shank, A.A. Zholents, and M.S. Zolotorev, "Generation of Femtosecond Pulses of Synchrotron Radiation," Science 287, 2237 (2000).

2. NEW FEMTOSECOND BEAMLINE 5.3.1 COMPLETED
(Contact: PAHeimann@lbl.gov)

A new beamline dedicated to femtosecond research has been built and will soon begin commissioning before initial experiments begin later this month. Beamline 5.3.1 was built to provide a permanent home for time-resolved experiments using the laser time-slicing technique described in Item 1 above, as well as other time-resolved laser-pump experiments previously performed at Beamline 7.3.3. The Sector-5 location was chosen because the laser time-slicing technique requires the use of the Sector-5 wiggler. At Beamline 5.3.1, which is half an arc sector away from the wiggler, the time-of-flight spreading of the electron slice will be limited to 100 fs. Also, as with Beamline 7.3.3, there is only one vertically reflecting mirror, which reduces the scattering in the horizontal plane. Low horizontal scattering is important for the background underneath the femtosecond x-ray pulses.

Research topics to be explored at the new beamline include coherent phonons close to a phase transition, dynamics in complex materials such as in colossal magnetoresistive (CMR) crystals, simple chemical reactions in solution, and atomic physics in high laser fields. One of the first experiments is scheduled to be an x-ray absorption fine structure (XAFS) measurement of a material melted by the ultrafast laser pulse. Another early experiment will look at the photoabsorption spectrum of an aluminum foil heated to a temperature at which it exists between the solid and plasma states.

The Beamline 5.3.1 engineering effort was led by Mike Kritscher and Keith Franck. Phil Heimann was the beamline scientist for the construction. The beamline was funded by University of California Directed Research and Development (UCDRD) funds with matching funds from the ALS for engineering, assembly, and installation.

3. CALL FOR ABSTRACTS: 2000 ALS USERS' MEETING
(Contact: alsabstract@lbl.gov)

The ALS Users' Executive Committee (UEC) invites ALS users, including students and postdocs, to submit abstracts for oral or poster presentations at the annual Users' Meeting, to be held at Berkeley Lab on October 16-18, 2000. Highlight oral presentations for the Young Researcher session will be selected by the UEC from the abstracts received; other submissions will be presented as posters. The poster sessions will be held in conjunction with the vendor exhibits on Monday, October 16, and Tuesday, October 17. Abstracts can be submitted on line at http://www-als.lbl.gov/als/usermtg/abstracts.html. The deadline is Tuesday, August 15.

General information about the meeting, including a list of workshops proposed for this year's program, can be found at http://www-als.lbl.gov/als/usermtg/. Registration and accommodation materials will be mailed out later this summer.

4. WHO'S IN TOWN

Following are some of the experimenters who will be collecting data during the next two weeks at the ALS.

Beamline 1.4.2
Lizelle Baylon (Solano Middle School)
Connie Hafner-Edwards (Vallejo Middle School)

Beamline 1.4.3
Phil Huie (Stanford Univ.)
Hoi-Ying Holman (Berkeley Lab)
Sherry Zhang and Phil Ross (Berkeley Lab)
Ted Raab (Univ. of Colorado, Boulder)
Jessica Preciado, Ralph Greif, and Boris Rubinsky (Univ. of California, Berkeley)
Felicia Betancourt and Robert Glaeser (Univ. of California, Berkeley, and Berkeley Lab)

Beamline 7.3.1.1
Kwang-Young Eun (Korea Institute of Science and Technology)
Boris Sinkovic (Univ. of Connecticut)

Beamline 8.0.1
Fred Schlachter (Berkeley Lab)
Marcello Sant'Anna (Berkeley Lab and Univ. Federal Fluminense, Brazil)
Maria Novella Piancastelli (Univ. of Rome)
Tony van Buuren and Christoph Bostedt (Lawrence Livermore National Laboratory)

Beamline 10.3.1
Thomas Cahill and Steve Cliff (Univ. of California, Davis)
Harry Atwater and Claudine Chen (California Institute of Technology)

5. OPERATIONS UPDATE
(Contact: EJLampo@lbl.gov)

For the user runs of June 14-19, June 20-25, June 27-July 3, and July 6-10, the beam availability was 96%. Of the delivered beam, 89% was delivered as scheduled without interruption. There were no significant outages.

Long-term and weekly operations schedules are available on the Web (http://www-als.lbl.gov/als/accelinfo.html). Requests for special operations use of the "scrubbing" shift should be sent to Gary Krebs (GFKrebs@lbl.gov, x7727) 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.