1. Dead time measurement.
There is a dead time ~500 ms when using non-zerosuppressed 4 range readout due to unsufficient size of TEM data buffer - see previous report
we decided to use in GSI zero suppressed 4 range readout to avoid this dead time in order to provide syncronization of 2 data streams: from calorirmeter and from beam diagnostics system
muon run collected with zero suppression stil shows non-Poissonian distribution of time between events
see histograms with different limits and bin size:
"hole" at small times between events <200ms
due to the time for event transmission TEM=>VME
significantly smaller than without zero suppression (~2 ms)
partly compensated by enhancement at 200-400 ms: real dead time <100 ms
peaks at 1.6 ms and 1.7 ms
contain ~2% of events
events from peaks have shifted pedestals in all channels
zero suppression doesn't work
explaination: second triggering after normal event
already seen with 1 range readout
not a problem in GSI as we plan to use external trigger
2. Trigger thresholds.
There is a possibility to measure the trigger thresholds in each channel by reading diagnostic information
it gives trigger bit for each layer
if we enable trigger only from one column - we will know exactly the output of trigger discriminator for each of selected 8 crystals
by collecting 12 runs with trigger enabled from different columns we can measure trigger efficiency vs signal amplitude for all channels
Data collected - analysis is going on.
3.Longitudinal position resolution.
light asymmetry vs position calibrated using muons
nonlinearity of light asymmetry corrected with spline function
we can find longitudinal position resolution by fitting linear function (X vs Z or Y vs Z) to 4 measurements of muon trajectory in 4 layers
resolution was found for filight electronics and for PEM electronics (with 5 times better signal to noise ratio)
position resolution for all 96 crystals is shown at the plot
position resolution with flight electronics and PEM electronics is strongly correlated - crystals and diodes are the same
spread in resolution is connected with crystal to crystal spread of light tapering
resolution with PEM electronics is better by factor 1.5, while signal/noise ration improved by factor ~5
this could be explained by intrinsic crystal non-uniformity ~2% (across the crystal ?)
