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    February 2004

    1. Synchrotron Radiation Experiment for Improved Fluorescent Lighting

    Graduate Student Yoshi Aiura and Prof. James Lawler at the University of Wisconsin are using vacuum ultraviolet radiation from the Aladdin Storage Ring at the Synchrotron Radiation Center to test improvements in high power density fluorescent lamps. Aiura and Lawler's research appeared in the January 2004 issue of Optics and Photonics News in a feature article by Graeme Lister of OSRAM-SYLVANIA INC. entitled “Keeping the Lights Burning, The Drive for Energy Efficient Lighting”.

    Because lighting consumes 20 to 25% of all electrical power, increased efficiency and a reduction in power consumption by lighting fixtures would mean a significant reduction in energy usage and a corresponding benefit to the environment. Fluorescent lighting is 5 to 6 times more efficient than incandescent (hot filament) lighting and offers the best possibility of even greater efficiency. Regular fluorescent lamps typically last 10,000 to 20,000 hours (versus 2000 hours for incandescent lamps), and electrodeless fluorescent lamps have lifetimes of 100,000 hours. Fluorescent lighting is already used in many commercial and industrial spaces. However, incandescent lighting is still the most prevalent form of lighting in North American homes due to a preference for its more natural-looking light and several performance problems with residential compact fluorescent lamps. If these issues can be addressed, the use of fluorescent lighting in residences could increase dramatically, thereby bringing about an overall decrease in energy usage.

    All fluorescent lamps contain mercury-argon plasmas which produce ultraviolet radiation when subjected to an electric current. This ultraviolet radiation excites a phosphor which releases visible light. Compact fluorescent lamps, as well as ultra-long-lived electrodeless fluorescent lamps, operate at much higher power densities than standard fluorescent lamps. Mercury-argon plasmas behave differently at these higher power densities than they do in standard fluorescent lamps. These plasma effects can degrade the performance of compact and electrodeless (radio-frequency excited) fluorescent lamps. The work being done by Aiura and Lawler at the SRC is designed to understand these plasma effects so that better fluorescent lamps can be designed.

    The new experiment, which started operation during 2003, uses the intense synchrotron radiation available at the SRC as a continuum for absorption spectroscopy on high power density mercury-argon plasmas in a specially modified electrodeless Icetron® lamp from Osram-Sylvania Inc. The smooth, spectrally broad, and intense continuum of synchrotron radiation is ideal for absorption studies, even on plasma which is radiating strongly. The experiment enables Aiura and Lawler to map the absolute density of ground state mercury atoms using absorption signals at 185 nm and the absolute density of ground level mercury ions using absorption signals at 194 nm. The increase in harder ultraviolet radiation at 185 nm can decrease the phosphor efficiency and more rapidly degrade the phosphor. This experiment is being used to test models of radial cataphoresis under various plasmas conditions. Plasma models are critical to efficient design of advance fluorescent lamps. The experiment is supported by the NSF, USHIO INC., and OSRAM-SYLVANIA INC.

    2. PGM Resurrection

    The PGM beamline is once again available for the user community following the successful installation of the temporary M1 mirror. The original M1 plane mirror contained internal water cooling channels and it is believed that a separation occurred between the channels and the optical surface, creating a distortion in the mirror which resulted in a severe loss of resolution. On the advice of the UAC, a quick-turn-around temporary mirror consisting of a silicon mirror with back cooling was designed and procured and installed in December. This mirror does not allow the beamline to achieve its ultimate resolution, but will make the beamline usable to many users until a new, full-specification mirror can be designed and fabricated.

    Testing of the PGM with the temporary M1 mirror has just been completed. Overall, the beamline is performing very well. Photon flux levels are the same as they have always been and scale with slit settings as expected. The new mirror is fully conditioned and can be used with any beam current at 800 MeV or 1 GeV.

    A best resolution of 0.9 meV at 21.5 eV has been achieved with an entrance slit of 17 microns and an exit slit of 10 microns, with the M1 apertures closed to a level where approximately half the flux is lost. If an entrance slit of 34 microns and an exit slit of 20 microns are used, the resolution is 1.2 meV with all apertures open. Overall, the temporary mirror limits the use of the very smallest slit settings. At that level, the slope errors of the temporary mirror and the small heating effects start to limit resolution. For all practical purposes, exit slit settings smaller than 20 microns will not be useful while the temporary M1 is in place. At the 20 micron slit setting or above, the measured resolution agrees well with predicted numbers and with previous performance of the beamline. This means that users who do not use the very highest resolution available from the beamline should not see a notable change in performance. A final report with more extensive documentation of the present condition of the PGM will be available very soon to all SRC users.

    The beamline manager, Mary Severson, would like to extend a sincere thank you to the user community for their patience during the PGM repairs. Thank you also to all of those on the SRC staff who worked so hard to make sure the PGM was repaired as quickly as possible.

    3. SRC Recruiting for Summer Research Program

    The SRC Research Experience for Undergraduates (SRC REU) program is preparing for its third year and we are busy recruiting students for the four positions we will have available. The program provides minority undergraduate students the opportunity to participate in research at the SRC under the guidance of SRC users and staff. This year the participants can choose to study in one of five fields of research: Spectromicroscopy and Cancer Therapy under “pupa” De Stasio; Next Generation Synchrotron Light Sources under Joe Bisognano; Molecular Memory and Nanostructure Fabrication under Franz Himpsel; Atomic-Molecular Physics under Ralf Wehlitz; and Nano Fabrication and Metrology Research under Don Thielman.

    The program runs from June7 through August 6, at the end of which the participants will write a paper and give an oral presentation of their research. The program provides a stipend, full support for travel, housing, health insurance (if needed), transportation, and a partial food allowance. Students have access to all campus libraries and facilities. There are no fees or tuition costs. In addition to their individual research experience, students participate in forums and workshops on university research opportunities and career planning. There are also planned social activities with students in other UW summer programs. During their stay, students are encouraged to explore Madison and the university.

    Applications to the program must be completed by March 1. More information can be found on the SRC website at htm