We had various problems in the D-tunnel all through saturday morning.
Things seemed ok but inded we were sending a wroing gate to the tof;s
This morning we take two cosmic runs field on and off, and there is
clearly a problem with the pulse heights of many tofs there. However,
there is even another more urgent problem: there is a non negligible L/R
cosmic asymetry. Please see statistical analysis in the logbook.
Instead of plotting the adc for a cut on the respective tdc channel, we
cut both tdc top and bottom so that we can count the number of cosmic
triggers in a run (macro plot_adc_ntp.C).
Results for field off: the tof rate is distributed asymeetrically, with
inefficiencies that are up to 10%. At least 3 tof's (L9, L15, R5 are
clearly bad, with only 30 % of the expected events. Inside the right
sector, 5 tofs out of 11 are more than 3 sigma away from the expected
average number of counts (of course they are equal area/angle tof's).
I believe that the hv of the tof's should increase by more than 10-20V
and maybe should go 10 % from the current voltage, for starters. I talked
to johjn and he also agrees that the first priority is gain matching...
That is done with cosmics so requires no accelerator operation in the
ring.
Hopefully tavi and adrian will carry us far enough that the we can use
beam again tomorrow evening. Manouch is "cancelling" CCR shifts. I cancel
the night shift of tonight. Tavi and Adrian are the nextg people on shift.
regards,
tancredi, peter, nikolas (still here!!) and chris (fixing liblast..).
-- tancredi
P.S.
I emphasize that the amount of work today required at least 3 people. Else
the above problem would, again, not be discovered. I believe that proper
gain matching will require at least 2 shifts.
________________________________________________________________________________
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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