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    User name jsingh

    Log entry time 06:05:18 on February 1,2003

    Entry number 94114

    keyword=Compton Fun:Rebooted Compton Slow Control

    short version:
    I noticed that the Compton Laser Cavity was not locking. Beam off was requested to reboot the Compton Slow Control. Total time w/o beam was roughly 20 min.

    longer version (see Compton Logbook for longest version):
    The online analysis for Compton Runs 7198-7199 were very strange. There was no signal in the data. On closer inspection, it appeared that the problem was related to the Laser Cavity not locking. I watched the event rates as the DAQ was supposed to be turning the cavity on and off. The rates were completely flat and in addition, i could see no light in the cavity on the CCD camera display. After conferring with Alexandre C., we decided to reboot the slow control for the Compton. I requested for Beam off and also had the Electron Detector masked. (The Electron Detector was made unstuck Friday afternoon around lunch, see entry #94023) We rebooted the Compton Slow Control. The power reading on the laser cavity was reading strange values (-2000W to +1000000W, should be around 1000W when ON). We rebooted again to try to fix this. The power now occasionally reads in the correct ballpark, but it is still way off most of the time. We moved the electron detector back to the "BEAM IN" postion. Because of the reboot, the photon detector went back to its "HOME" position. Therefore, we moved the photon detector back to the center crystal (33). Taking Compton data again. So far run #7202 looks good. The cavity seems to be locking just fine. Only problem now is the power reading for the cavity.