All new scintillator bars come from the same
Eljen scintillator batch #12793. For this test, a bar is placed
inside the ligh-tight black box. Two PMTs are pressed against
the opposite ends of the bar with a spring-loaded mechanism.
A pulsed UV LED is positioned at 2 different points along the bar.
PMTs signals are measured with CAEN V792 ADC.
Light attenuation is calculated assuming a single exponential dependence.
Some bars were measured without removing clear plastic wrap
they came with. Then, the wrapping was removed and the measurement
redone. As an example shown below, the new 3cm-wide bar 12793-04-02
has Latt = 282cm with wrapping and
Latt = 627cm without it. Unwrapped 4.5cm-wide bar 12793-02-10
was measured to have Latt = 559cm. Identical
measurements of the bars for full TOF 6 years ago had attenuation
length on the order of 150cm with plastic wrap and 250-400cm
without it. It looks like the new batch is isgnificantly better
in terms of light attenuation comparing with the old one.
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