The paddle is a standard TOF paddle but with small trapezoidal light-guides. It is placed into a light-tight black box. Hamamatsu PMT 10534SEL with a nominal gain of 1.21*10^6 (at 1750V) is used. For triggering, two 1cm-wide finger scintillators are placed above and below the paddle as pictured. Their discriminators are set to 200 mV to ensure triggering on quality tracks only. Coincidence of these 2 signals goes into the scope's channel 1 (yellow) which is set to trigger the scope. 10534SEL anode signal with a delay over a long cable goes straight into the scope's channel 2 (blue) with 50 Ohm load. Pulses are averaged over 16 triggers (averaging is done manually due to EM noise issue). A representative pulse (witin +-5 mV of the calculated average) is shown below. The trigger telescope was located in the middle of the paddle at 50'' from the PMT.
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The curve represents a simple exponential fit in the form ADC = a * exp(b * HV), where ADC is in mV and HV is in Volts. The fitted parameters are: a=0.2144 and b=5.13611e-03