Tagger Rate study from data taken Sept. 2001 during PrimEx beam tests

Below are plots of the PrimEx pair spectrometer rates vs individual t-counter rates. The rates for both the PS and the Tagger were calculated using multi-hit TDCs with cuts on the region outside of the trigger event.

The T-counter rates are taken straight from the multi-hit TDC's which had the Left-Right hardware coincidence as input.

The PS rates were calculated from 4-fold coincidences done via software. The coincidence windows used were +/-5ns.

All data points (ranging from beam current of 75pA up to 80nA) were used to fit a 4th order polynomial. A linear function was also fit, but using only the points from 1nA to 64nA inclusive.

The inset on each plot shows the ratio of the T-counter rates to the ps rates normalized to the ratio at 8nA. The x-axis is the individual T-counter rate in kHz.

There was some problem with the fits to T-counter 2 and T-counter 18 which I've not tracked down yet.

Nominally, individual T-counters have a maximum rate of 4 MHz before failing. Unfortunately, this data only goes up to about 1.3 MHz for these counters, so the drop-off is not clearly seen. We can, however, see that the T-counters are starting to reach a limit somewhere near 1.2 to 1.4 MHz. The possible exception is T-counter 7 which may be losing hits at a slightly lower rate.

click on a plot for an enlarged view.
click on "PS" at the lower right of a plot for a encapsulated Postscript format of the plot.
PS PS PS PS PS PS PS PS PS PS PS PS PS PS PS PS PS PS PS
David Lawrence
davidl@jlab.org
Mon Oct 29 13:12:35 EST 2001