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  • Aladdin newsletter header

    THE ELECTRONIC ALADDIN NEWSLETTER NO. 15
    November / December 1997


    HIGHLIGHTS FROM THE SRC USERS MEETING

    The SRC Users Meeting and a Topical Workshop on Correlated Electrons took place Oct. 24/25. In the morning of the first day, students reported on their experience and their results at SRC. In the afternoon, a series of topical talks gave insight into some new applications of synchrotron radiation, such as in cell biochemistry. The workshop presented the latest thoughts and results from a variety of exotic, new states of electrons, such as high temperature superconductors and one-dimensional solids.

    A collection of pictures from the workshop can be found at:

    http://hhochst.src.wisc.edu/SRC/Workshop/UMeet97_Gallery.html


    USERS WORKING WITH THE NEW INFRARED MICROSCOPE

    David Wieliczka from the University of Missouri-Kansas City came to SRC to research a nagging problem: Dental fillings. With the newly-commissioned infrared microscopy beamline he wanted to investigate the sealing properties of new composites and their potential lifetime when used as fillers. The microscope was able to scan across the tooth-filling interface and to take infrared spectra revealing the interface between the polymer adhesive and the dentin. Dave was extremely impressed with the high flux of the new IR-beamline. Based on his experience with conventional laboratory sources, data of similar spectral quality could not have been obtained from laboratory IR instruments. Due to their large light source size, conventional laboratory IR microscopes are constrained to larger spot sizes while the well-focused light spot of the synchrotron source allows lateral resolution of several microns. Details on this work can be found at:

    http://hhochst.src.wisc.edu/webPRESS/IR_Beamline/
    dental_fillings/toothscan.html

    Richard Duerst and co-workers from Abbott Laboratories (Illinois) tested the infrared microscope on small polystyrene spheres that are used in combinatorial chemistry for drug development. Using the reflection mode he was able to obtain chemical fingerprints of the molecules adsorbed on single spheres.

    These infrared experiments were performed in just a few days, which is quite a departure from the several week long ultra high vacuum experiments that have been characteristic of synchrotron experiments in the ultraviolet.


    ATOMIC PHYSICS AT THE NEW PGM BEAMLINE

    With its single p-hole in the valence shell, the chlorine atom has long served as the prototype system to study the influence of the asymmetric charge distribution on electron dynamics. The new PGM undulator beamline at SRC has now made possible a significant step forward in the analysis of gas-phase photoexcitation in this open-shell system. Using total ion yield detection, Denise Caldwell and coworkers have observed excitations from the 2p-shell for the first time. The total yield spectrum of atomic chlorine around the 2p region reveals a rich spectrum of lines with a number of unexpected features. In comparison to closed-shell argon, the single line for the 2p3/2-4s excitation is now "split" into three major components for the open-shell chlorine atom. The most unexpected of the characteristics of these chlorine 2p excitations are the extraordinarily narrow width of the spectral lines. A tentative analysis reveals that the sharpest feature at 204.34 eV has a width of 18 ± 0.5meV. This is a factor of four less than what might be

    expected based on a comparison with the corresponding width in argon.


    BEAM STABILITY IMPROVES AFTER SEPTEMBER UPGRADE

    During September, an extensive upgrade of Aladdin took place. The vacuum chamber sections containing the quadrupole magnets were replaced. The new sections contain robust beam position monitors (BPM’s), different clearing electrodes, extra bellows for mechanically decoupling the position monitors from the rest of the chamber, and new ion pumps with attached sublimators. Particularly important for the operation of the ring with the high precision undulators are the BPM's. The new BPM's are firmly referenced to the concrete floor, providing a more stable beam position readout. The change in beam stability was monitored by two optical diagnostic stations at different points in the ring (averaged over more than 35 user fills, Aladdin running at 800 MeV, Global Feedback system active). Prior to the upgrade, the vertical beam position varied by plus/minus 60 micron at one of the monitors, after the upgrade by plus/minus 45 micron. The spread at the other monitor improved more dramatically, from 115 micron to 20 micron.


    BEAM TIME REQUESTS FOR 1998/99 SOLICITED

    The deadline for the annual beam time requests will be Feb. 1 '98. A form will be available on the SRC Web site under "Online Forms". It can also be downloaded as WordPerfect file from there. As usual, the request will be for a full year (August '98 to July '99). In addition to the annual beam time, there will be some beam time set aside in the second half of the period (Jan-July '99) for an extra round of proposals for hot topics during Sept.'98.


    HONORS FOR SRC RESEARCHER

    Gelsomina "pupa" De Stasio received the worldwide TOYP (The Outstanding Young Persons of the world) Award for Scientific and Technological Development by the Junior Chamber International. The award was given to pupa during a formal ceremony in Honolulu on November 18. Previously, she had won the national award in Italy. After that she was selected among the awardees of 116 countries worldwide for the international award. She received the award for the commissioning of the MEPHISTO spectromicroscope which in 1997 reached the world record resolution of 50 nm, and for her work on spectromicroscopy in boron neutron capture therapy. Most of the work that led to the award was performed at SRC.