Light guide

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--- Cosmic ray data --- We take cosmic ray data on a lead glass block with FEU-84-3 PMTs attached on both ends. The bases are regular resistor voltage deviders. Data are taken with several configurations. Comparing the response of the PMT when having an air-gap (like in RadPhi) to having a 3.7cm long light guide glued to the PMT and coupled with optical grease to the lead glass block leads to a 2.5 times higher light output. The light guide is wrapped in aluminized mylar.

PMT response with air-gap:
Cosmics response airgap.jpg

PMT response with light-guide.
Cosmics response LGwrapped.jpg