continued taking data for Cerenkov efficiency study.
we took 2 hr. runs at 0.2 sccm with the BLAST field at 0, 1500, and 3000
A. the change from 1500 and 3000 took a while for beam steering and
slit optimization (slit settings are in the log book).
run summary:
------------------
2926 field off 267 k WC off
2927 field off 351 k WC on (SH lights OFF)
2930 1500 A 354 k WC on (SH lights OFF)
2931 3000 A 189 k WC on (SH lights OFF)
the epics server crashed sometime before run 2930 was started, so that
run has no epics events, but does have physics events. thanks to
vitaliy, we were able to make an ntuple out of the physics events.
(just had to bypass the 'while' loop in ntuple.C that looks for the
first epics event to get the 'go' time.)
estimated the Cerenkov efficiencies for the front two C's in each sector
by cutting on ttl or ttr (wherever the proton was): first plot ttl:ttr
for the chosen paddle combination to find where the elastic ep events
are; then cut around these events. confirm that this cut gives coplanar
events by plotting ptl:ptr; then plot ncl (or ncr) which tells you which
Cerenkov fired for the event. in these plots all the events that fired
a Cerenkov should be in one Cerenkov only since we used only middle
tofs. if an event doesn't fire any Cerenkovs, it goes in the '-1' bin.
then we calculated the efficiency by: e = (N_total - N_(-1))/N_total,
where N_(-1) is the number of events (in the '-1' bin) that don't fire
the Cerenkov. i didn't calculate the efficiencies for all paddle
combinations, but i did do two separate combinations for C1. The
results are shown below:
run # TOFL TOFR C eff. (%)
------------------------------
2927 2 13 L0 91.7 (no field)
5 12 L1 88.2
6 11 L1 87.1
11 6 R1 91.9
12 5 R1 95.1
13 2 R0 91.8
------------------------------
2930 2 13 L0 93.0 (1500 A)
5 12 L1 93.4
6 11 L1 93.9
11 6 R1 96.5
12 5 R1 96.6
13 2 R0 92.5
------------------------------
2931 2 13 L0 88.3 (3000A)
5 12 L1 79.5
6 11 L1 80.6
11 6 R1 90.2
12 5 R1 92.4
13 2 R0 91.3
------------------------------
finally, noted that right_tof_top_0 adc looks funny when you run
plot_adc.C. all of the events are in one bin (mean = 466.7), but are
not obviously bad (reasonable number of events in this tof, etc., just
not distributed). first guess was binning, but plot_adc.C bins
everything the same, so still not sure what's up with this tube.
js vz
-- -------------------------------------------------------------------- jason seely 26.650.b massachusetts institute of technology 77 massachusetts avenue cambridge, ma 02139-4307email: seely@mit.edu phone: 617.253.4772/6734 html: web.mit.edu/seely/www --------------------------------------------------------------------
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