PMT change and ADC gate.
New PMTs on the top trigger paddle
Top trigger paddle always had a strange shape of Delta(t) with
a dip in the middle (left plot). Paul has replaced both PMTs.
After that, the shape of Delta(t) has improved (right plot).
Still, it is not quite what it is expected to be. The other trigger
paddle is fine (bottom plot).
Proper ADC gate
Caen ADC v265 requires the gate to start at least 65 ns before the signals.
It wasn't clear if the gate can also end 65 ns earlier or if it should cover
the whole signal. Apparently, the later is true. With a 100 ns gate, the
separation of peak from the pedestal is about 180 ADC counts (left plot).
Separation inceases with an increase in the width of the ADC gate until
about 175 ns. After that, it seems to remain constant. Right plot is
for 200 ns gate, with signal-to-pedestal separation of about 450 counts.