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User name pking
Log entry time 15:06:11 on December 3,2014
Entry number 404386
keyword=More about the DVCS deadtime calculation in datamon
The DVCS deadtime is calculated from the ratio of the accepted triggers (DVCS_stop) to the combined input trigger rate after prescaling (DVCS_MasterOR). This is the fraction of potential triggers which are missed because the system is busy.
Figure 1 is from run 10301, triggered at 103kHz/512==201Hz. The CODA rate was also 200Hz, and there is enough time between triggers to fully readout the event data. There are no triggers missed.
Figure 2 is from run 10302, triggered at 103kHz/32==3.2kHz. The average CODA rate was about 1kHz, but fluctuated up to about 1.3-1.4 KHz. We were missing an average of 2/3 of the triggers, but the snapshot may have been taken during one of the higher fluctuations when an 54% deadtime is about right.