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    User name Jin Huang

    Log entry time 20:33:14 on November23,2009

    Entry number 302171

    This entry is a followup to: 302096

    keyword=RHRS Optics Problem

    As a search for proof that RHRS Q3 polarity is inversed, we ran a quick optics check on single carbon foil.

    How does the check works.
    As shown on page 8 of hall A NIM paper, HRS magnets have a focus effect on y direction. Say for central carbon foil, no matter the phi direction of out coming particle, it will be focused to a specific focal plane y position. When Q3 is inversed, this focus will be broken. The approach of this study is by checking this focus property before and after HRS polarity changes.

    We selected a positive and a negative polarity runs for each spectrometer. For each run, 2 plots are generated: Focal Plane Y hit distribution (Left) and React Z Distribution (Right)

    first plot :
    Top : LHRS Positive Polarity
    Bottom : LHRS Negative Polarity

    Second Plot:
    Top : RHRS Positive polarity
    Bottom : RHRS Negative Polarity

    As you can see, LHRS Y-Phi optics properties remain similar before and after polarity change. However, VZ reconstruction on RHRS positive run is messed up. Also the Y focusing is gone.

    Therefore, RHRS optics has problem at positive polarity. Compiling previous information, it's most likely that Q3 is inversed.


    Besides optics study, we also recorded trigger rate before/after turning off Q3 on RHRS.

    Conf. Current/uA LHRS T1/Hz RHRS T1/Hz

    Q3 ON 10 810 700

    Q3 OFF 10 800 850

    Which means we are getting better acceptance after turn off Q3. Therefore we move to low current production with RHRS Q3 off

    FIGURE 1

    FIGURE 2