O.M. Signals, Compared Over Varying Inputs
IceCube 2007 Home
Introduction
Here we set up a series of trials where we
varied the input voltage to the O.M. to study its effect on signal
shape and size.
Equipment:
Optical Module
Hamamatsu BB-7250, containing PMT model R5912-02
Oscilloscope
Lecroy Wavepro 7000
Photo Multiplier Tube
Hamamatsu R7081-10
Amanda type scintillater/P.M.T. box
Setup
The O.M. and the P.M.T were placed inside
the dark box with their faces to a scintillater plate (the type in the
Amanda type scintillater/P.M.T. box). The Amanda type
scintillater/P.M.T. box was placed on top of the dark box, directly
above the scintillater plate. The trigger on the Oscilloscope was
set to qualify a trigger by the signal on the Amanda type
scintillater/P.M.T. box to reach -30 mV, and the signal on the P.M.T.
to reach -250 mV within 100 ns of the first. This setup was used
to guarantee muon caused triggers. The signal from the O.M. was
averaged and stored. Persistence recordings of all of the signals
and histograms of the signal size were also recorded.
Results
Here is a normalized (by deviding by the highest
value) comparison of the different average signals. There is a
clear widening of the average signal as the input voltage
increases. To explain this it is helpful the look at the
persistence recording of the signals that were averaged (here). The
large amount of wild noise that is down and to the right of the real signal pulse
has the effect of pulling the average
towards itself. The noise is probably caused by saturation
of the O.M. as it is running at a high input voltage and is facing a
scintillater plate that emits much more like per muon than a tank of
water would.
IceCube 2007 Home
