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User name johna
Log entry time 19:57:17 on October 28,2007
Entry number 143693
keyword=fast raster problem (not new)
Since the beginning of the run, we've had problems with the fast raster readout from the ADCs jumping around. In the attached figure, one can see the two different regions. The run started with all events where they should be (centered around 3000 channels), and after ~30k events, the signals shifted to low values where they are presumably being cut off.
Note that the engine gets the 'zero' value of the raster from the average of the 1000 pedestal events, so when the raster is in the bad position from the beginning, the 2-d plot will still be nicely centered and APPEAR normal (maybe the wrong size), but we are NOT getting raster information out properly.
We probably don't care (or don't care too much) about the raster readback for correcting delta (i.e. improving the HMS resolution), but I imagine that we DO care about it for spin precession. So we should figure out what's going on with the raster signal that's going into the ADC.
p.s. second figure is later in the same run. It's clear that the raster signal 'jumped', and all events after ~30k are coming in at the offset position.
FIGURE 1
FIGURE 2
