Log entry time 16:24:12 on June29,2004

Entry number 127392

This entry is a followup to: 126672

  Do the septa behave differently (in terms of heating) for 
the hydrogen target vs. the helium target? I have heard 
conflicting statements about this. Of course, we have extended
the "plug" collimator during the configuration change, so a 
direct comparison is not really fair...nevertheless...

  I looked at a recent stable run at 40 µA (run 2510).
I 'grepped' on the raw CODA files to get the septa temperatures,
which were steady throughout the run:

  Right arm upper coil = 7.80 K
            lower coil = 7.65 K
  Left arm upper coil  = 7.00 K
           lower coil  = 7.20 K

 Compare these values to the scan we did with the helium target
   (See entry 126672)

  and we see the data nearly lie on the curve; displaced downwards
by about 0.05 K (or, roughly, allowing about 4 more µA of
beam for the same heating). Any model of the septum heating must
explain this near coincidence - either hydrogen would have been
worse than helium, and the plug extension improved things to 
compensate, or....