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    User name Cdaq

    Log entry time 13:10:21 on October 30,1997

    Entry number 423

    keyword=SOS alignment

    Derek and I continued to work on the SOS gas Cerenkov detector yesterday. Derek
    remembered that the center of the Cerenkov box needs to be about 1.5 inch above
    the nominal centerline between the two hodoscope planes. Rolf confirms Derik's
    recollection. This alignment requirement is related the ray focusing of the
    spectrometer. First, since lower energy particles are bent more than the higher
    energy particles, there is an asymmetry in the up/down acceptance of the detector. Second, there is a desire to keep the majority of the particles away from the
    center of the 4 mirrors, i.e. where the four mirror corners of the mirrors meet.
    We have therefore moved the box position so that the TOP of the cross beam
    which supports the box on the 4 threaded rods is 13 inches above the top plate of
    the Cerenkov sled. Note that Liming and I had originally centered the box at 11.5
    inches above the plate. Today we will install the base for phototube 4, check the
    signals, light leak check the box, and then fill with freon. More on all of this later.