PMT assembly is aimed at T0 monitoring and is located on the top flange of the YELLOW UPSTREAM polarimeter. It contains 3 scintillators making a telescope for particles emitted from the target in vertical direction. 4 PMTs look at the 3 scintillators: V1 and V1 at the bottom scintillator, S1 -- on the next one, and S2 -- on the topmost one.
HV is supplied from the counting house through former bias cables, signals arrive at the panel in the middle of Rack4 and then are connected to WFD in Rack1.Crate2.Station20:
- V1 - YELLOW BIAS 3 - R4 Middle Panel 1 - WFD R22.214.171.124
- V2 - YELLOW BIAS 4 - R4 Middle Panel 2 - WFD R126.96.36.199
- S1 - YELLOW BIAS 5 - R4 Middle Panel 3 - WFD R188.8.131.52
- S2 - YELLOW BIAS 6 - R4 Middle Panel 4 - WFD R184.108.40.206
At the moment V1 and S1 are connected to an HV power supply in Rack4.Crate2.2, V2 and S2 are left unconnected. All PMTs have working voltage ~1.0 kV. V1 and S1 draw ~0.5 mA at 1 kV, while V2 and S2 need ~1.5 mA at 1 kV and, thus, better power supply.