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Requirements to RICH FEE

Requirements to RICH FEE. Serguei Sadovsky IHEP, Protvino CBM meeting GSI, 10 March 2005. 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 60-70 mm Photo-cathode: K 2 CsSb

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Requirements to RICH FEE

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

  2. 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 60-70 mm • Photo-cathode: K2CsSb • Quantum efficiency at 410 nm is 25% • Effective number of dynodes is 12 • Nominal HV is less than 2 kV • Amplification is 106 • Dynamical charge range is 0.25-2.5 pC • Noise current is 3000 e/sec • Capacitance is 15 pF • Power dissipations is 40 mW

  3. 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 -- 3000 e/sec • Pulse lenght -- several ns • Output capasitance -- 15 pF • ADC bit number -- 8-9 bits • Channel density -- 2.5 channels /cm2 • Total number of channels – 100000- 200000

  4. 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 1.6-2 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

  5. 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/Fclock • The main problem is the electronics density, i.e. 0.4 cm2/channel

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