[BLAST_ANAWARE] lifetime unpol/ABS D2 runs

From: Tancredi Botto (tancredi@lns.mit.edu)
Date: Fri Jul 30 2004 - 13:06:07 EDT


Hi genya, chi

I attached a plot of the beam lifetime vs current for runs 8878-8889
(empty, green), runs 8901-8911 (unpol D2, red) and in black ABS runs. Abs
and unpol runs have been taken consecutively, without interruptions, after
a maintennace shutdown. The empty target data come from the nihgt before
the shutdown. The lower ABS black band is from abs before the shutdown as
well.

Allow to me jump in: i just want to point out that if you compare unpol
D2 to ABS, the lifetime data shows that the target density during unpol D2
is always less or at best close than that observed for ABS.

This analysis can not be very precise but find it hard to believe that
the unpol system set to 1.5 V did produce a much higher flow than the ABS
(if anyhting, it was the other way around !) and this is consistent with
the fact the both unpol and abs have the same ed rates.

So again it looks like the unpol system is delivering less gass than
expected, and that abs intensity estimations based on such "unpol
calibration" will exaggerate the ABS density.

-- tancredi
P.S.
I've added the beam lifetime (tau) to scaler_ntuple.C. You can easily redo
it yourself.

________________________________________________________________________________
Tancredi Botto, phone: +1-617-253-9204 mobile: +1-978-490-4124
research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949
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tau.gif



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