Test of the new scintillator bars

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.


Wrapped 3cm-wide bar Unwrapped 3cm-wide bar Unwrapped 4.5cm-wide bar