Requirements to RICH FEE Serguei Sadovsky IHEP, Protvino CBM meeting GSI, 10 March 2005

B M C Parameters of the PMT FEU-Hive External PMT diameter is 6 mm Photo-cathode diameter is 5 mm Photo-detector element diameter 7 mm PMT length is mm Photo-cathode: K 2 CsSb Quantum efficiency at 410 nm is 25% Effective number of dynodes is 12 Nominal HV is less than 2 kV Amplification is 10 6 Dynamical charge range is pC Noise current is 3000 e/sec Capacitance is 15 pF Power dissipations is 40 mW

B M C Inputs for RICH Front End Electronics on the base of the PMT FEU-Hive: Negative polarity of the output signals Total charge in a pulse – from 0.25 to 25 pC Noise e/sec Pulse lenght -- several ns Output capasitance pF ADC bit number bits Channel density channels /cm2 Total number of channels –

B M C HV regulation Classical scheme of the HV regulation with ballast resistor and PMT dividing sercuit The ballast resistor has 6 bit regulation in the region kV, i.e. with 6V step Avaliable space, we have only 0.4 cm2/channel, due to this we have, probably, no possibility for the HV regulation

B M C Summary Nominal HV for the PMT is 2 kV No HV regulation, but pre-selection of the PMTs with different gains Power consumption 40 mW/PMT due to HV divider 8-9 bit ADC The width of the PMT signal is several ns Shaper time depends on requirements to the time resolution, it should be at least 3 time samples for any PMT pulse, thus τ ~ 3/F clock The main problem is the electronics density, i.e. 0.4 cm2/channel