Test on RPC Veto Detector Model Anticoincidence Detector

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Test on RPC Veto Detector Model —— Anticoincidence Detector for Daya Bay Neutrino Exp.

Test on RPC Veto Detector Model —— Anticoincidence Detector for Daya Bay Neutrino Exp. Speaker: Jiawen Zhang 5 June 2006 1

Outline u. RPC Introduction u. RPC R&D in IHEP Of CAS Ø RPC Performance

Outline u. RPC Introduction u. RPC R&D in IHEP Of CAS Ø RPC Performance Study Ø RPC Mass Production for BESIII u. RPC for Daya bay Neutrino Exp. Ø Precondition and requirement Ø Test Design Ø Test Result u. Summary 2

RPC Introduction What is RPC? RPC is composed of two resistive plates with gas

RPC Introduction 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. Advantages: u. Simple structure u. Cheap to make a larger area detector 3

RPC R&D in IHEP Of CAS l The RPCs for the BESIII Muon tracker

RPC R&D in IHEP Of CAS l The RPCs for the BESIII Muon tracker detector were constructed by using a new type of phenolic rosin laminates developed in IHEP of CAS. l The methods of improving surface quality is similar to other bakelite plates, and have been used to construct RPCs elsewhere. Oscilloscope traces of 100 triggered cosmic ray registered in a RPC prototype at 8 k. V. The average signal amplitude from a pickup electrode is about 400 m. V with a 50 Ω termination. No secondary streamers were recorded 4

Bakelite surface 5

Bakelite surface 5

R&D —— prototype performance 1. 18 0. 044 96 -98% 7

R&D —— prototype performance 1. 18 0. 044 96 -98% 7

R&D ---- long-term stability other neutron irradiation experiments Beam test Max: 98. 8% Average:

R&D ---- long-term stability other neutron irradiation experiments Beam test Max: 98. 8% Average: 97. 2% Min: 95. 3% 8

R&D ---- Humidity effect • During the R&D test, we added water vapor into

R&D ---- Humidity effect • During the R&D test, we added water vapor into the gas for about one month. No effects were observed. • All the HV connectors to the RPC are covered with insulation glue. Last summer, the humidity was about 80 -90% lasting about 2 week in Beijing. We tested the RPC bare chambers and the assembled modules, no problem was found, and we will do more test soon. 9

R&D---Flammability gas • The flammability Iso-butane of the mixture gas maybe catch fire, if

R&D---Flammability gas • The flammability Iso-butane of the mixture gas maybe catch fire, if its proportion is more than 15%. • We used the gas mixture of argon: F 134 a: Iso-butane = 50: 42: 8, Therefore the problem won’t be avoided with the ventilation requirement for Radon removal. 10

RPC mass production for BESIII • Single layer RPC (bare chamber) efficiency ε>95% Barrel

RPC mass production for BESIII • Single layer RPC (bare chamber) efficiency ε>95% Barrel 7. 5 Kv Min. 85. 6% Max. 99. 02% Aver. 95. 39% Barrel 8. 0 Kv Min. 90. 38% Max. 99. 2% Aver. 96. 4% 11

RPC mass production for BESIII • A new bare chamber single counting rate is

RPC mass production for BESIII • A new bare chamber single counting rate is below 1000 Hz/m 2( only training 1 -3 days), if training for a long time, the single counting rate will be below 500 Hz/m 2 Barrel 7. 5 Kv Min. 0. 016 Max. 0. 599 Aver. 0. 095 Barrel 8. 0 Kv Min. 0. 022 Max. 0. 872 Aver. 0. 130 12

RPC mass production for BESIII • 2 layers of RPCs form a super layer,

RPC mass production for BESIII • 2 layers of RPCs form a super layer, ε >98% Mean 0. 98 Average eff: 0. 99 13

The requirements of Daya bay Neutrino Exp. u The anticoincidence detector is used to

The requirements of Daya bay Neutrino Exp. u The anticoincidence detector is used to decrease the cosmic ray background to improve measurement precision Table 1. Neutrino instance and Cosmic ray flux Near Site Far Site Neutrino rate (/day) 560 80 Muon Flux (Hz/m 2) ~1 0. 045 According to the design, we know the radius of central detector is 1. 6 m. And by calculation, the cosmic ray through the detector is 8 Hz near site, and 0. 36 Hz far site. Taking example of far site, the cosmic ray through 4 modules every day is 4× 0. 36 Hz× 3600 s× 24 h=125000 >>80 14

 • Anticoincidence detector ε~99. 9%, 125(>80) cosmic ray won’t be removed • Anticoincidence

• Anticoincidence detector ε~99. 9%, 125(>80) cosmic ray won’t be removed • Anticoincidence detector ε~99. 99%, 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! 15

The design of detector u. Requirement Ø Higher efficiency Ø Less noise But these

The design of detector u. Requirement Ø Higher efficiency Ø Less noise 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%[1] , noise <0. 1 Hz. [2] ) 16

The design of detector(2) u. Outer detector scheme • • Adopt 2 dimension readout

The design of detector(2) u. Outer detector scheme • • Adopt 2 dimension readout RPC operate in streamer mode The gas mixture used as Ar: C 2 H 2 F 4: C 4 H 10 =50: 42: 8 HV: +4000 V,-4000 V ü Single gap, 3 layers in one module ü Each layer overlapping assembly, no dead space. ü Each module overlapping assembly too, so between modules no dead space. 17

detector(3) u Efficiency and noise ü Efficiency of each layer is ε ~95%, and

detector(3) u Efficiency and noise ü Efficiency of each layer is ε ~95%, and adopt choose 2 out of 3 as a hit, their coincidence efficiency is εeff =ε 3+C 32 ε 2(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% ü The RPC bare chamber noise rate ~800 Hz/ m 2 , the shaped signal width is τ=100 ns=10 -7 s, so the module noise rate is 3 C 32 r 2 τ=3 × 3 X(800)2× 10 -7=0. 576 Hz/m 2 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. 05 Hz/m 2. If we reduce RPC noise rate to 300 Hz/m 2, 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 1 Hz ! 18

The design of detector(4) • Electronics and readout l the same as BESIII Muon

The design of detector(4) • Electronics and readout l the same as BESIII Muon detector. l Each FEC can handle 16 channels,and a total of 16 FEC composed a data chain. l All the data chains are connected to the VME readout system. l A fast-OR signal from each FEC is sent to the trigger system. l The primary bitmap signal are transferred from parallel to serial, hence reduce significantly the cables. l The width of the shaped signal is 100 ns. 19

Test Result(1) • Group 1 (have been used as a telescope sys. ) 99.

Test Result(1) • Group 1 (have been used as a telescope sys. ) 99. 5± 0. 25% 20

Test Result(2) • Group 2(haven’t used) 99. 3± 0. 4% 21

Test Result(2) • Group 2(haven’t used) 99. 3± 0. 4% 21

Summary u RPC is economical for a larger area detector u The RPC performance

Summary u RPC is economical for a larger area detector u The RPC performance developed by IHEP is excellent, single gap RPC efficiency>95%, noise rate <800 Hz/m 2, dark current <2μA/m 2 u Adopt 3 layers, 2 dimension readout, RPC and module overlapping assembly, no dead space. Adopt choose 2 out of 3 as a hit, their coincidence efficiency >99%, the noises <0. 05 Hz/m 2 u Electronics and readout are same to BESIII Muon detector. 23

Reference 1. 2. Determination of Neutrino Mixing-Angle θ 13 Using the Daya Bay Nuclear

Reference 1. 2. Determination of Neutrino Mixing-Angle θ 13 Using the Daya Bay Nuclear Power Facilities,version 3. 1 Preliminary study of Daya Bay reactor neutrino experiment, Yaxuan Sun, Ph. D thesis The end Thanks! 24