1 / 20

Sensitivity of Hybrid Resistive Plate Chambers to Low-Energy Neutrons

Sensitivity of Hybrid Resistive Plate Chambers to Low-Energy Neutrons. Byungsik Hong Korea 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 University S.J. Hong

zocha
Download Presentation

Sensitivity of Hybrid Resistive Plate Chambers to Low-Energy Neutrons

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Sensitivity of Hybrid Resistive Plate Chambers to Low-Energy Neutrons Byungsik Hong Korea 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 University S.J. Hong Neuroscience Research Institute, Gachon Medical School

  2. Outline • Motivation • Detector construction and setup • Results • Gd-coated single gap with strip readout • Gd-coated double gap with pad readout • LiF-coated double gap with pad readout • Conclusions VIII RPC Workshop

  3. Motivation • Why do we want to measure low energy neutrons? • Crucial to detect anti-personal mines and explosive underground, etc. • Possible application to imaging devices • If the R&D is successful, then • Easy-to-build neutron detector • Cheap and large neutron detection system VIII RPC Workshop

  4. Basic Idea • Coating the inner surfaces of electrodes with neutron sensitive materials • 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. VIII RPC Workshop

  5. Candidate 1 • Interesting isotopes are about 30% in natural Gd2O3. • Ref.) M. Abbrescia et al., NIMA 533 (2004) 149. VIII RPC Workshop

  6. ~ 550 barns for 75 meV ~ 950 barns for 25 meV Candidate 2 n + 6Li  α+ 3H (Q = 4.78 MeV, Eα = 2.05 MeV, EH = 2.73 MeV ) VIII RPC Workshop

  7. Ground Hybrid RPC Gap Signal pad (or strip plane) Hybrid RPC Gap Ground Construction of Hybrid RPC VIII RPC Workshop

  8. Gd-Coated Double-Gap RPC Gd layer mixing composition: - Gd : PVC : thinner= 8 : 1 : 2.7 - Gd layer thickness: 25㎛ - Bakelite resistivity ~ 2*1010 Ωcm Readout pad x-width: 100mm y-width: 100mm Gd-Coated Single-Gap RPC Gd 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 VIII RPC Workshop

  9. LiF-Coated Double-Gap RPC LiF layer mixing composition: - LiF : linseed oil : heptane 1.7 : 1 : 29 - LiF layer thickness: 20㎛ - Glass resistivity ~ 7*1012 Ωcm Readout pad x-width: 55mm y-width: 55mm VIII RPC Workshop

  10. Pictures Assembled Single-Gap Gd-RPC Assembled Double-Gap Gd-RPC Assembled Double-Gap LiF-RPC VIII RPC Workshop

  11. Experimental Conditions • 252Cf (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/cm2on Sept. 8, 2005 VIII RPC Workshop

  12. Results Single-gap Gd-RPC with random trigger Ar : i-C4H10 = 50 : 50 VIII RPC Workshop

  13. ‘backward’configuration RPC e- n e- Gd2O3 Bakelite Bakelite Gd layer Gd layer e- e- n n RPC Essentially no absorption Long way to go e- n Backward scattering electrons generate avalanches: always the same thickness. Neutron intensitydecreases with the depth of the Gd layer exponentially. e- Gd2O3 Ref.) M. Abbrescia et al., NIMA 533 (2004) 149. Forward vs Backward ‘forward’configuration VIII RPC Workshop

  14. Number of neutrons Number of clusters Channel Entries 310 Mean 2.563 rms 1.163 1 2 3 4 5 6 7 8 0 1 2 3 4 5 6 7 8 0 Number of strips Results - Single-gap Gd-RPC with random trigger + (xy-coincidence) - Possible imaging application VIII RPC Workshop

  15. e- n e- n e- gap gap readout pad e- Results Double-gap Gd-RPC with random trigger Ar : i-C4H10 = 65 : 35 VIII RPC Workshop

  16. Results Double-gap LiF-RPC with random trigger Ar : i-C4H10 = 65 : 35 LiF-RPC 4.0 mV 5.0 mV 6.5 mV 8.0 mV VIII RPC Workshop

  17. Efficiencies per gap (Gd-RPC) Neutron energy (meV) Forward config. GEANT Simulation VIII RPC Workshop

  18. Efficiencies per gap (LiF-RPC) Neutron Energy (meV) GEANT simulation VIII RPC Workshop

  19. Comparison LiF-RPC 4.0 mV 5.0 mV 6.5 mV 8.0 mV ~60% of possible maximum VIII RPC Workshop

  20. Conclusions • We have built and tested the prototype RPC which is sensitive to low energy neutrons (~75 meV). • The Gd- and LiF-coated RPCs show stable operation in the operational HV plateau regions. • The 2D-strip readout with the spatial resolution of ~2.5 cm is possible. • Technical difficulties to be solved • Control the surface roughness for large area • Rate capability (we may need low resistive electrodes.) • Applications in real world VIII RPC Workshop

More Related