Test on RPC Veto Detector Model —— Anticoincidence Detector for Daya Bay Neutrino Exp. Speaker: Jiawen Zhang. 5 June 2006. Outline. RPC Introduction RPC R&D in IHEP Of CAS RPC Performance Study RPC Mass Production for BESIII RPC for Daya bay Neutrino Exp. Precondition and requirement
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Test on RPC Veto Detector Model—— Anticoincidence Detector for Daya Bay Neutrino Exp.
Speaker: Jiawen Zhang
5 June 2006
What is RPC?
RPC is composed of two resistive plates with gas flowing between them. High voltage is applied on the plates to produce a strong electric field in the gas. When a cosmic-ray passes through the gas between the two plates, a signal will produce, which is then picked up by the pickup strip and sent to the DAQ system.
Oscilloscope traces of 100 triggered cosmic ray registered in a RPC prototype at 8 kV. The average signal amplitude from a pickup electrode is about 400 mV with a 50 Ω termination. No secondary streamers were recorded
RPC mass production for BESIII
Average eff: 0.99
Table 1. Neutrino instance and Cosmic ray flux
According to the design, we know the radius of central detector is 1.6m. And by calculation, the cosmic ray through the detector is 8Hz near site, and 0.36Hz far site.
Taking example of far site, the cosmic ray through 4 modules every day is 4×0.36Hz×3600s×24h=125000>>80
12(~15%) cosmic ray won’t be removed
Most of cosmic ray can be removed by spectrum & time relation of later neutron signal
So the result is acceptable!
But these two factors are contradictions, so the key problem is how to balance the two factors.
A fact is that a water Cherenkov may be used. (efficiency is ~ 95% ,noise <0.1Hz. )
εeff=ε3+C32 ε2(1- ε)=0.953+3×0.952×(1-0.95)=99.3%
The efficiency of the module with the water Cherenkov is
1-(1- εeff)(1- ε)=1-(1-0.99)(1-0.95)=99.95%
3C32r2 τ=3 ×3 X(800)2×10-7=0.576Hz/m2
since the module has 3 layers RPC, so we can do the track for itself. By using the track information, the noise can be reduced to <0.05Hz/m2. If we reduce RPC noise rate to 300Hz/m2, the noise can be reduce to more lower.
In addition, Because the noise of the water Cherenkov is very small, the total noise is
not more than 1Hz!