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    User name Armstrong

    Log entry time 15:18:29 on June11,2004

    Entry number 125365

    This entry is a followup to: 125310


    keyword=Target High Power Heater during current scan

      The Figure below shows the 4He target high power
    heater during the owl shift current ramp (to 10 µA) and
    a linear extrapolation to higher currents. 
       For the uninitiated, the higher power heater is there to stabilize
    the cooling of the target. At zero beam current, it is in essence
    a measure of the total cooling capacity of the cryotarget (under
    the operating conditions present at that time); as the beam current
    increases, the high power heater power level is automagically reduced
    by the control system. Note that stable operation requires that the
    heater power be non-zero, so the intercept is an overestimate of the
    max. operating current.
      While the data are not very linear vs. beam current, they are
    too limited based on this scan to determine a better functional form.
      We also may be able to adjust the operating conditions of the 
    target to improve the heating power... butI don't have a good
    intuition of by how much we can improve things.

    FIGURE 1