Operators: seely vziskin chris2
Atomic fraction was taken and measured to be 53% w/o MFT and 43% with MFT on. The greater difference is atributed to the greater molecular background from SFT chamber which is consitent with the higher pressure in SFT. However, the tune for the ion polarimeter was bad and the nanoampmeter signal was very low (factor of 4 lower). This could also be due to a bad electron beam since the operations could not reinject again. I suggest the AF to be measured again in the afternoon.
I modifed the show_ep_asym2.C code to choose the dilution factor for each sector by minimizing the chi squared. This method is attractive since it does not require a "fudging" of the dilution by hand. Also, the dilution determined this was seems to be insensitive to the number of bins used in the plot.
I used this method to further investigate the l/r issue. I tried to include the Cerenkov into the cut and here is what I found:
left dilution right dilution
no cc 0.13 0.09
cc_el 0.16 0.14
It seems that the Cerenkov clean up both right and left sides, with the right side benefiting more. The average dilution of 0.15 corresponds to 25% target polarization, assuming 60% beam polarization. This result remains the same (l/r dilution= 0.16/0.13) even if I do not make a tight cut on the center of the target, which is simply amazing to me. I think that this underscores the importance of the Cerenkovs working and working properly. I include the plot of the "final" asymmetry with the cerenkov cut.
back to running with reversed field. Did an MFT 2-3 scan. Adjusted the static field since I think it shifted a little.
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