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User name A. Camsonne
Log entry time 01:50:01 on September 07, 2009
Entry number 288360
keyword=Compton BCM puzzleI looked at the raw data. The problem is that I set the electron detector to be read every 50 events or less for previous runs. The time between two readings if thus rather short giving a lot of uncertainty on the BCM current ( frequency of VtoF bigger than readout rate ) and clock ( 20 MHz ) this gives some erratic values of the current when you divided those two. It seems that for photon only, the rate of read out is much smaller, it seems to even fit all the time in one helicity window ( 27 ms ). So one thing I will want to try is to increase the size of the fifo in the limit of the VME CPU memory and take only coincidence data to reduce the rate the electron detector is read-out. Ideally the buffer should be able to contain a full helicity window. I will try that after the next access since I had to power cycle the ETROC and my FPGA programmer crashed ( I will have to make sure to put it on hareboot4 ).
On run 18985, one see the scalers values for the BCM and the clock is almost all the time 27 ms ( 20 MHz clock ).
On the run 18922, the clock count is much smaller and the BCM scaler
value as well.
A copy of this log entry has been emailed to: rsholmes@jlab.org,rom@jlab.org,souder@jlab.org,paschke@jlab.org
Figure 1
Figure 2
