Operators: tancredi karpiusp ----
2nd level trigger reduced the overall Phys0+1 rate by almost 1/10 and
the deadtime to negligible levels. We should not have problems to go to
higher currents. We have trigger rates of 50 Hz at 40 mA and extremely smooth
conditions, apart from the 22 s ring glitch (visible on "all" blast scalers as well).
Onlinegui functions well and gives excellent wch S/N (just remember to hit
start after a clear or refresh!!)
At 1x10^16 At/s on a 100 K cell, we expect about 1.5 Hz / 100 mA total
H rate for reverse field. Our average current may be 25 mA so expect only 0.4
Hz. Clearly there is still a lot more stuff passing the trigger.
By nsed and lrn it is clear that the 2nd level is not too stringent: most of the
accepted events have only one wch-sector and are not elastic H. Almost
all events in file have (of course) at least 3 chamber hits/sector.
Could not compare rates of true H-elastic with 2nd level trigger. Need for
runs to finish crunching. I suggest staying at 20 mA until we confirm
the polarization value also with 2nd level trigger. We need to study eventual polarization trends. Mixing a higher beam current may not be a good idea
just yet.
here are results (average of L-R sectors) for an average beam polarization
of 0.65 from compton. Pol_a: Helastic_tight cut. Pol_b: Helastic cut. Data after cut looks equally good across data sets, and with minimal background.
runs: 3570-3581 Pol_a: 0.90 +- 0.15 Pol_b: 0.76+-0.11 charge 300 C
runs: 3604-3611 Pol_a: 0.35 +- 0.19 Pol_b: 0.24+-0.13 charge 230 C ?
runs: 3612-3619 Pol_a: 0.56 +- 0.18 Pol_b: 0.45+-0.12 charge 230 C
runs: 3620-3628 Pol_a: 0.30 +- 0.18 Pol_b: 0.28+-0.12 charge 230 C (12/05 am)
the second data set showed little polarization early this aft. Wch box L9
was disconnected at TDC. 2nd level trigger runs start with 3654 and are crunching now. Not sure what went wrong with runs 3644-3649, may only need
recrunching (lrn file was small).
We also need to make sure that 2nd level trigger brings the same yield of
good events (possibly cut on tof's only with elas_flrn_outb so as to be
independent of recon efficiencies).
Attached is the normalized "raw" rates in the tofs vs run number from the
.rate program. You can clearly see our 3 running periods:
old collimator - new collimator (>3600) - 2nd level trigger (>3654)
I had no time to update the cut so this rate is representative of random coincs not of gas rate. HOWEVER tof elastic rate (using timing+adc) amouts to
3.33+-0.03 events/C before the additioanl collimator went in and is of
(3.40+-0.03) 1/C in runs 3612-3619 after the collimator. Most of this rate is gas related (a small bckg correction is needed).
Tomorrow tb will not be available (irregardless of snow storms..)
PLAN is to continue polarization anaylsis+monitoring, including yield/coulomb with 2nd level trigger compared with before.
To get tof yield just do: count_charge.C ### and then root elas ### and in the session do Draw("trig") and count the events. Divide by the total charge in
step 1 ........). NOTE the elas crunching filter has been aptly renamed elas_flrn_outb(ending) !!
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