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Cross talk of MAPMT on the single photoelectron level (very preliminary!)

Cross talk of MAPMT on the single photoelectron level (very preliminary!). analog signals to scope. pulser. HV.

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Cross talk of MAPMT on the single photoelectron level (very preliminary!)

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  1. Cross talk of MAPMT on the single photoelectron level (very preliminary!) analog signals to scope pulser HV

  2. A (scintillating) fiber (0.5 mm square) is positioned at the centre of a pixel in mechanical contact with the MAPMT window. No optical grease of gel is used. Low intensity light pulses from a LED are coupled into the fibre. The light intensity is chosen such that the average intensity corresponded to 0.2 photoelectrons per pulse, i.e. the probability for pulses with 2 photoelectrons is negligible. The MAPMT is operated at UC = -950V. The figures below show the results of the measurement of the signals on the scope (area under pulse) on the illuminated pixel and the adjacent eight pulses. The cross-talk on the direct neighbours is of the order of 2% while diagonal neighbours show a signal of about 0.5%. The relative strength of the cross-talk varies with the applied bias. The measurement will take 1-1.5h and occupy 2-3 students. Simple PCB to contact legs of MAPMT needs to be fabricated (few 100 CHF). Something appropriate may exist from Hamamatsu. The measurements have to be performed in a dark box. There is a risk that the MAPMT gets exposed to ambient light in case the students forget to switch off the HV before they open the box !

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