EPSAfter a conversation with Itaru today, we realized the tagging ratio plots shown below from October 2002 did not take TDC self-inhibit deadtime into account. The problem is that if an untagged photon came into the TAC within about 25ns of a tagged one, the TAC would miss the tagged one due to the 25ns deadtime induced by the untagged one. This would lead to a lower tagging ratio. The plot shown here is the tagging ratio vs. fine e-channel with a filter to exclude tagger hits in which there was a TAC hit between 10 and 60 ns of the tagger hit. This should remove the undesirable tagger hits where deadtime could come into play. The tagging ratio here flattens out to about 94%.
Here is are two plots made from run 797, an 80pA run with the TAC in. The first shows the occupancy of the TAGM bank (fine energy channels with ET coincidence). This plot is also cut on the hit NOT being associated with the trigger.
The second plot is the tagging ratio vs. fine E-channel (lower values on the x-axis correspond to higher energy photons). This represents the fraction of hits for which the reconstructed photon was in coincidence with a TAC hit. This plot shows an expected drop in the ratio at the highest energy due to increased Moeller electrons in those detectors.
I've started work on the PFlux library to calculate the photon flux for PrimEx data. Here is the
output of bankdump for the RATE bank which holds intermediary data. This is for Run 799
for which the
logbook states:
The MOR should be the sum of the tagger T-counter which is roughly 19*100kHz=1.9MHz from this picture. |
 PS |
| Here is the rate measured for T-counter 2 via TDC for the first 2 minutes of run 799. |  PS |
| This plot shows the rates measured via TDC for all 19 T-counters. The rate is calculated every 10k events. This number is somewhat arbitrary and will need to be optimized. |  PS |
| This shows the projection of the T-counter 6 rate from the above plot. |  PS |
| Here is a profile I ran on pflux_mon with all process flags on. (This tells us where the program is spending the most time.) | |
The plot at the bottom of those posted on Setp. 9th showed two bands in HYCAL vs. Ephoton. The second (lower photon energy band) was due to a hot E-counter and the quick and dirty photon reconstruction code used to produce the hbook DSTs. That version assumed when there were two and only two E-T coincidences, it was due to the electron passing through adjacent E-counter's. The photon energy was calculated as the average of that determined for the two E-counters. This was true much of the time, but a significant portion of the events had the erroneous hit from the hot E-counter bringing the average artificially down. Here is a plot of just W26 vs. the tagger energy after the fix.
These plots were produced from run 847. In this run, the photon beam was centered on PbWO4 crystal W26. A very rough photon energy was calculated for events meeting certain criteria. Mainly, that there were only one or two E-T coincidences. (The two coincidence events were assumed to be from the overlap region of the E-counters and an average energy was used).
No timing calibration was done so the cuts shown eliminated several T counters.
