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  • Aladdin newsletter header

    March/April 1998


    The Users Advisory Committee (UAC) met at O'Hare on May 2nd to discuss future directions for instrumentation and operations at the SRC. Several promising ideas were brought up in a very productive session. The following gives the essence of the discussion on selected topics and some possible/likely actions:

    Establishing a beam line with wide photon energy range requested by users:
    A simple solution would be the addition of two extra gratings to the HERMON monochromator, which would extend its spectral range down to 60 eV.

    Replacing the old permanent magnet undulator:
    The current SSRL undulator dates from the early days of undulator development. It tilts the beam and is not tunable during a fill. The UAC stressed flexibility as guideline for a new undulator, which means keeping the full energy range. This includes EUV lithography (about 100 eV) and spin-polarized photoemission at the low end (about 10-50 eV). A likely choice would be an electromagnetic undulator similar to the U1 that is currently being tested. A modification of the existing OMM monochromator is being considered for high flux applications, such as spin-polarized photoemission, and a branch line with a Wadsworth monochromator for high resolution valence spectroscopy.

    Changes in the beam time proposal process:
    Various review committees and NSF have asked for a faster process for getting access to beam time at the SRC. The UAC felt that the currently-available procedures were adequate but was open to establishing additional avenues.Last year, the on-line Rapid Request mechanism was expanded and widely used. In addition, a second proposal submission date will be made available 6 months after the spring date (deadlines Feb. 1 and Aug. 1). To reduce the load on PI's and reviewers, while maintaining flexibility in the scheduling, the duration of proposals will be extended from 12 to 18 months. Users who prefer the current system will be able to continue with the previous 1 year cycle.


    The beam time schedule from Aug. 98 to Jan 99 is now on the Web. See the topic "Yearly Schedules" under the button "Beam Schedules". Let Hartmut Höchst know if rescheduling is necessary or an advance reservation for a later scheduling period is needed.


    The 1998 Users Meeting of the SRC will take place Friday, Oct. 23. It will be accompanied by a Workshop on Spectromicroscopy on Saturday, Oct. 24, chaired by Pupa De Stasio. As further information becomes available it will appear in the News section of the SRC Web page.


    Under the title "Eyes on the Nucleus", Science Magazine introduces recent work by Ben Nelms, Richard Maser, Jim MacKay, Max Lagally, and John Petrini on the repair of radiation-damaged DNA in nuclei (Science 280, 590 (1998)). Cell nuclei were irradiated with a stripe pattern of synchrotron radiation from the SRC, using masks produced at the CXrL. By biochemical tagging methods, the question was settled whether repair enzymes move to the damaged DNA or vice versa. A brief writeup of the results can be found on the SRC Web page in the Highlights section.

    In the March 12 issue of Nature (p. 134), Piers Coleman introduces recent work on the Fermi surface of high temperature superconductors, performed by Juan Carlos Campuzano's group at the SRC (M.R. Norman et al., Nature 392, 157 (1998)). In high temperature superconductors with a doping level below the optimum, the familiar concept of a Fermi surface starts falling apart and the electronic structure becomes highly unusual. This is also the region where a pseudo-gap is observed at temperatures as high as room temperature. For an introduction to high temperature superconductor work see the Highlights section.

    "Synchrotron Beam Makes Cell Tell All" is the title of a writeup in Science News (Vol. 153, p. 279 (1998)) where two types of synchrotron-based microscopies are described. It mentions Pupa De Stasio's photoelectron microscopy work at the SRC, where she keeps breaking resolution records. The 23 nm resolution given in the writeup is down to 20 nm in the meantime and dropping.


    The new Scienta analyzer of the SRC has been running at the high-resolution 4m NIM beam line for the past month and is providing its first solid state results. Currently, Juan Carlos Campuzano's group is using it for mapping the Fermi surface of high temperature superconductors (see item 4). Information on the Scienta analyzer is on the Web. It can be requested on the SRC Web page under Online Forms.


    John Weaver, University of Minnesota, one of the SRC pioneers, received the "Distinguished Achievement Citation" from the Iowa State Alumni Foundation. He was cited for "consistently brought very powerful tools such as photoemission and scanning tunneling microscopy to bear on both fundamental and practical problems in surface science." The Honors and awards Ceremony will be on October 9th during the Homecoming weekend.

    Gerry Harp, who has been a driving force behind the magnetic work at the SRC, was granted tenure at Ohio University.