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.

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ALSNews           Vol. 19           April 4, 1995

Table of Contents


    1. OPERATIONS UPDATE
    2. FIRST LIGHT TO CHEMICAL DYNAMICS BEAMLINE
    3. VISITING RESEARCHERS -- CAMERON LOPER

1. OPERATIONS UPDATE
(contact: rmmiller@lbl.gov)

Beam availability last week was 92.5% overall and 92.7% during user shifts.

Operations summary for April 4-23
1.5-GeV, 400-mA, 320-bunch operations for users:
    April 5, 16:00-23:15
    April 6-9, 08:00-23:15
1.9-GeV, >250-mA, 320-bunch operations for users:
    April 12, 16:00-23:15
    April 13-16, 08:00-23:15
    April 19, 16:00-23:15
    April 20-23, 08:00-23:15
Maintenance: 
    April 10 & 17, 08:00-16:00, with startup 16:00-23:15
Accelerator Physics:
    April 4, 11 & 18, 08:00-23:15
    April 5, 12 & 19, 08:00-16:00

**R-I-N-G FOR AN OPERATIONS COORDINATOR**
(contact: rkthatcher@lbl.gov)

ALS Operations Coordinators, the main point of contact between ALS operations and users, now carry portable phones so that users can always reach them while the ALS is operating. The extension for these phones has been changed from x6000 to x7464 (or RING for those who are already carrying enough numbers in their heads!). The reason for the change of extension is that large numbers of calls intended for the Lawrence Berkeley Laboratory main switchboard were tying up the Operations Coordinator phone, because the two extensions differed by only one digit.

2. FIRST LIGHT TO CHEMICAL DYNAMICS BEAMLINE
(contact: phil_heimann@macmail.lbl.gov)

On March 24, ALS light shone through Branchline 1 of chemical dynamics beamline 9.0.2 for the first time. The first activity at the beamline was to take transmission grating spectrometer (TGS) measurements characterizing the performance of the beamline's novel harmonic filter. The windowless, differentially pumped rare-gas filter lets the low-energy (8-30 eV) undulator fundamental pass through unattenuated, while suppressing higher undulator harmonics to 0.01% or less of their original flux, for spectral purity unprecedented in a raw undulator beam. The 8-cm-period undulator (U8) now in use will be replaced by a U10 in September 1995, lowering the beamline's minimum photon energy to 5 eV.

Branchline 1, its TGS characterization complete, will deliver high-flux (~10e16 photons/sec), "white" (2% bandwidth) radiation to Endstation 1 for photodissociation and crossed-molecular-beam experiments. Branchline 2, to be completed in June, will use an off-plane, 6.65-meter, normal-incidence Eagle monochromator to achieve resolving powers between 50,000 and 100,000 with various gratings. Endstation 2 will include time-of-flight equipment for coincidence detection, and a zero electron kinetic energy (ZEKE) detector for high-resolution electron spectroscopy with excellent sensitivity. This detector employs a small electric field and a pair of narrow apertures to detect electrons with nearly zero kinetic energy very efficiently. By scanning the incoming photon energy over the range of valence electron binding energies, researchers can use the ZEKE detector to obtain a peak at each electronic and vibrational (and in some cases rotational) energy level of a molecule.

The beamline will also incorporate several lasers. An excimer laser will provide high-power UV light for photochemistry studies and to produce beams of radicals. A pumped dye laser system will produce intense, pulsed visible and UV light suitable for running Endstation 2 when Endstation 1 has the undulator beam. A custom-built, high-power, high-resolution infrared laser system will round out the beamline's capabilities. Arthur Suits (Chemical Sciences Division, Lawrence Berkeley Laboratory) is the PRT spokesperson for Beamline 9.0.2, and Phil Heimann (ALS) is the beamline coordinator.

3. VISITING RESEARCHERS -- CAMERON LOPER
(contact: cloper@lumiere.lbl.gov)

Cameron Loper of North Carolina State University has come to the ALS as part of the Science and Engineering Research Semester (SERS) program, which places college students from all over the United States at national laboratories. His mentor here is mechanical engineer Steve Marks (ALS Experimental Systems Group), who has set Loper on a course of study involving magnetic theory and application and computer programming.

The SERS program offers students majoring in engineering, mathematics, or science, the opportunity to work for 1-2 semesters at a national laboratory. Housing and a stipend are provided, and at Berkeley, the 22 SERS students live together near campus. The students write papers and make presentations about their work at the laboratory.

A major attraction of the SERS program is the opportunity it offers for hands-on, rather than textbook, learning. Loper is learning how to use and write programs for acquisition of magnetic field data. He is working with Marks on the measurement and analysis of U10, a new undulator to be installed in the ALS this fall. Before an insertion device is installed in the ALS storage ring, its magnetic field must be mapped in detail and analyzed extensively to predict performance and to provide a basis for necessary adjustments. Loper is also working with Marks, Ross Schlueter, and Klaus Halbach on the design of magnets for the proposed permanent-magnet recycler and stacker rings for the TevaTron at FermiLab (for more on this project, see ALSNews Vol. 7, Dec. 13, 1994). Loper has been working on concepts for passive compensation for loss of magnetic strength due to temperature fluctuations. He is working hard to absorb all he can about magnetic theory, because "once you know the core theory, you can adapt it to any project."

Another strong draw of the program, and one Loper hasn't entirely gotten used to, is that students work with scientists and engineers whose work is known and used internationally. For example, he thinks it's fantastic that Klaus Halbach "is right here!" To Loper it is amazing to walk around the hill, with its world-class view, and know that the technology and research going on here are at the cutting edge of science.

Loper's LBL supervisor, Steve Marks, finds the students he works with smart, enthusiastic, and productive. He benefited from a similar program as a student and sees being a mentor as a chance to "return the favor." After one more semester at North Carolina State, Loper plans to continue his studies in mechanical engineering at Georgia Tech graduate school.