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    User name D. Parno

    Log entry time 13:11:22 on December13,2008

    Entry number 253243

    keyword=Compton spectrum in PbWO4 crystal

    After swapping back to the original PbWO4 crystal (central crystal in the Saclay array) and DAQ settings, I obtained a very nice, clear Compton spectrum with this afternoon's beam (Fig. 1).

    Fig. 2 shows the corresponding asymmetry in Compton events. We see an asymmetry of about 6-7% at the Compton edge, which agrees quite well with what we saw in the GSO data from early last week (when it was working well). Looks like the beam is still polarized!

    It looks as though the fault was with the new detector, either the GSO crystal itself or its phototube.

    FIGURE 1

    FIGURE 2