MRPC Principle -f from RPC to MRPC Work in avalanche mode for cathode high rate capacity Thin gas gap to improve time resolution anode Quench avalanche process to avoid streamer Idea comes true in 1996 M.C.S.Williams et al.,Nucl.Instr. and Meth..A374(1996)132 2023/6/28 Talk for EM group伍健 16
2023/6/28 Talk for EM group 伍健 16 MRPC Principle – from RPC to MRPC Thin gas gap to improve time resolution Quench avalanche process to avoid streamer Idea comes true in 1996 M.C.S. Williams et al., Nucl. Instr. and Meth. A 374 (1996) 132 Work in avalanche mode for high rate capacity
MRPC Basic Structure Signal electrode Cathode -10 kV Stack of equally-spaced resistive plates with voltage applied to external surfaces (all internal (-8kV) plates electrically floating) Pickup electrodes on external (-6kV) surfaces (resistive plates transparent to fast signal) (-4kV Internal plates take correct voltage initially due to electrostatics but (-2kV) kept at correct voltage by flow of electrons and positive ions- Anode 0 V feedback principle that dictates equal gain in all gas gaps Signal electrode cnspin.williams@cem.ch sHde 12 2023/6/28 Talk for EM group伍健 11
2023/6/28 Talk for EM group 伍健 17 MRPC Basic Structure
9 Feedback Effect Cathode-10 kV (-8kV) Normal Operation -6.5 KVokVI Low E field-low gain High E field-high gain (-4kV) (2kV) Cathode-10 kV Anode 0V (-8kV) (-6kV) (←4kV) (-2kV) Abnormal Operation: Anode 0 V Feedback effect recovers the right electric potential 2023/6/28 Talk for EM group伍健 18
2023/6/28 Talk for EM group 伍健 18 Feedback Effect Normal Operation Abnormal Operation: Feedback effect recovers the right electric potential
Gas Parameters for MRPC Operation Gas Mixture:90%C2F H2+5%iso-Butane +5%SF6 Transverse Diffusion (cm/s) 000 t03 a-first townsend coefficlent Longitudinal Dlffusion(cm/s) B-attachment coefficlent n-effective townsend coefficlent 0 200 Drift Velocity (m/ns) 60 80 100 120 140 160 60 80 100 120 140 160 Electric Field (kV/cm) Electric Field (kV/cm) Operation E-field:~110 kV/cm Effective Townsend Coefficient:n ~1400 /cm Electron drift velocity 200 microns/ns(2x105m/s) 2023/6/28 Talk for EM group 伍健 19
2023/6/28 Talk for EM group 伍健 19 Gas Parameters for MRPC Operation Gas Mixture: 90%C2F4H2 + 5%iso-Butane + 5%SF6 Operation E-field : ~ 110 kV/cm Effective Townsend Coefficient : ~ 1400 /cm Electron drift velocity ~ 200 microns/ns (2105m/s)