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    User name V. Sulkosky

    Log entry time 22:26:00 on October 15, 2009

    Entry number 295133

    This entry is a followup to: 295131

    keyword=Cryo-Target instabilities

    After beam returned, we have been struggling to run at high current
    due to the reduced capacity of the cryo. Last night we were running
    about 95-96 uA. This evening, the cryo flow is oscillating between 25
    and 25.2 g/s with the JT valve open around 57%. As the plots in the
    previous Halog showed at 100 uA, we had no room left on the HP heater
    and target temperature had warmed up to about 19.2 K. We decided to
    reduce the beam current until we could bring the target under better
    control.

    Unfortunately this increased the detector widths to almost 5500 ppm. As
    a compromise, we had MCC increase the raster size to 10.2 x 10.2 and
    reduced the current to about 92 uA. The widths had come back down to
    about 5200-5300 ppm. The situation is still pretty much on the edge due
    to the limitations on the cooling power. The biggest problem is that
    the supply temperature is still too high around 13.7 K. To run 100 uA,
    it is best to be below 13.5 K.

    A copy of this log entry has been emailed to: paschke,dalton,lerose,mcnulty,rom