Tests of RPCs (Resistive Plate Chambers) for the ARGO experiment at YBJ
Sensitivity of Hybrid Resistive Plate Chambers to Low-Energy Neutrons
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Transcript of Sensitivity of Hybrid Resistive Plate Chambers to Low-Energy Neutrons
Sensitivity of Hybrid Sensitivity of Hybrid Resistive Plate Chambers to Resistive Plate Chambers to Low-Energy NeutronsLow-Energy Neutrons
Byungsik HongKorea Detector Laboratory, Korea University
M. Ito, T.I. Kang, B.I. Kim, H.C. Kim, J.H. Kim, K.B. Lee, K.S. Lee, S. Park, M.S. Ryu, K.S. Sim
Korea Detector Laboratory, Korea UniversityS.J. Hong
Neuroscience Research Institute, Gachon Medical School
Oct. 10-12, 2005 VIII RPC Workshop 2
Outline
1. Motivation
2. Detector construction and setup
3. Results Gd-coated single gap with strip readout Gd-coated double gap with pad readout LiF-coated double gap with pad readout
4. Conclusions
Oct. 10-12, 2005 VIII RPC Workshop 3
Motivation
1. Why do we want to measure low energy neutrons? Crucial to detect anti-personal mines and explosive
underground, etc. Possible application to imaging devices
2. If the R&D is successful, then Easy-to-build neutron detector Cheap and large neutron detection system
Oct. 10-12, 2005 VIII RPC Workshop 4
Basic Idea
1.Coating the inner surfaces of electrodes with neutron sensitive materials
2.Conditions for neutron detectors The neutron capture cross section for coating material
should be well known in advance over a wide range of energy.
The sensitivity should depend mostly on the capture cross section for neutrons.
Oct. 10-12, 2005 VIII RPC Workshop 5
Candidate 1Interesting isotopes are about 30% in natural Gd2O3.Ref.) M. Abbrescia et al., NIMA 533 (2004) 149.
Mass No. %152 0.2154 2.2155 14.8156 20.5157 15.7158 24.8160 21.8
Oct. 10-12, 2005 VIII RPC Workshop 6
Candidate 2n + 6Li α + 3H (Q = 4.78 MeV, Eα = 2.05 MeV, EH = 2.73 MeV )
~ 950 barns for 25 meV~ 550 barns for 75 meV
Oct. 10-12, 2005 VIII RPC Workshop 7
Construction of Hybrid RPC
Ground
Ground
Hybrid RPC Gap
Hybrid RPC Gap
Signal pad(or strip plane)
DetectorStructure
(electrodes)
Read
Out
Operation
Mode
Gd-RPC/
Plain-RPC
Single Gap
(bakelite)2D-
StripsStreamer
Gd-RPC/
Plain-RPC
Double Gap
(bakelite)Pad Streamer
LiF-RPCDouble Gap
(glass)Pad
Low Gain
Avalanche
Oct. 10-12, 2005 VIII RPC Workshop 8
Gd-Coated Single-Gap RPCGd layer mixing composition:- Gd : linseed oil : heptane= 2.5 : 1 : 9- Gd layer thickness: 80 ㎛- Bakelite resistivity ~ 2*1010 Ωcm
Readout strip-x-strip plane thickness: 0.4mm strip width: 2mm-y-strip plane thickness: 1.6mm strip width: 3mm
Gd layer mixing composition: - Gd : PVC : thinner= 8 : 1 : 2.7- Gd layer thickness: 25 ㎛- Bakelite resistivity ~ 2*1010 Ωcm
Readout padx-width: 100mm
y-width: 100mm
Gd-Coated Double-Gap RPC
Oct. 10-12, 2005 VIII RPC Workshop 9
LiF-Coated Double-Gap RPC
Readout padx-width: 55mmy-width: 55mm
LiF layer mixing composition:- LiF : linseed oil : heptane 1.7 : 1 : 29- LiF layer thickness: 20 ㎛- Glass resistivity ~ 7*1012 Ωcm
Oct. 10-12, 2005 VIII RPC Workshop 10
PicturesAssembled Single-Gap Gd-RPC
Assembled Double-Gap Gd-RPC
Assembled Double-Gap LiF-RPC
Oct. 10-12, 2005 VIII RPC Workshop 11
Experimental Conditions252Cf (T½=2.645 y) source at KAERI
○ Test detectors
- Installed behind the concrete wall, which shields gammas and also moderates neutrons in an energy region close to the thermal energy
- Neutron energy ranges between 10 and 560 meV, centering at 75 meV.
○ Neutron rate
- Measured, independently, by a Bonner sphere at the position of the present data taking
- R = 44.5 Hz/cm2 on Sept. 8, 2005
Oct. 10-12, 2005 VIII RPC Workshop 12
ResultsSingle-gap Gd-RPC with random trigger
Ar : i-C4H10 = 50 : 50
Oct. 10-12, 2005 VIII RPC Workshop 13
‘forward’ configuration ‘backward’ configuration
ne-
e-
Gd2O
3
RPC
Backward scattering electrons generate avalanches: always the same thickness.
n
Bakelite Gd layer
e-
Essentially no absorption
Forward vs BackwardRef.) M. Abbrescia et al., NIMA 533 (2004) 149.
Neutron intensity decreases with the depth of the Gd layer exponentially.
ne-
e-
Gd2O
3
RPC
n
e-
Bakelite Gd layer
Long way to go
Oct. 10-12, 2005 VIII RPC Workshop 141 2 3 4 5 6 7 80
Number of strips
Num
ber
of c
lust
ers
Entries 310Mean 2.563rms 1.163
Results
1 2 3 4 5 6 7 80
Channel
Num
ber
of n
eutr
ons
- Single-gap Gd-RPC with random trigger + (xy-coincidence)
- Possible imaging application
Oct. 10-12, 2005 VIII RPC Workshop 15
ResultsDouble-gap Gd-RPC with random trigger
Ar : i-C4H10 = 65 : 35
ne-
e-n
readout pad
gap
e-
e-
gap
Oct. 10-12, 2005 VIII RPC Workshop 16
ResultsDouble-gap LiF-RPC with random trigger
Ar : i-C4H10 = 65 : 35
LiF-RPC4.0 mV5.0 mV6.5 mV8.0 mV
Oct. 10-12, 2005 VIII RPC Workshop 17
Eff
icie
ncie
s pe
r ga
p (G
d-R
PC
)
Neutron energy (meV)
GEANT SimulationForward config.
Oct. 10-12, 2005 VIII RPC Workshop 18
GEANT simulation
Neutron Energy (meV)
Eff
icie
ncie
s pe
r ga
p (L
iF-R
PC
)
Oct. 10-12, 2005 VIII RPC Workshop 19
Comparison
LiF-RPC4.0 mV5.0 mV6.5 mV8.0 mV ~60% of
possible maximum
Oct. 10-12, 2005 VIII RPC Workshop 20
Conclusions
1. We have built and tested the prototype RPC which is sensitive to low energy neutrons (~75 meV).
2. The Gd- and LiF-coated RPCs show stable operation in the operational HV plateau regions.
3. The 2D-strip readout with the spatial resolution of ~2.5 cm is possible.
4. Technical difficulties to be solved Control the surface roughness for large area Rate capability (we may need low resistive electrodes.)
5. Applications in real world