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T riple GEM detector at CERN n_TOF facility

T riple GEM detector at CERN n_TOF facility. S.Puddu 2,4 , G.Claps 1 , G. Croci 3 , F. Murtas 1,2 , A.Pietropaolo 3 , C. Severino 2,4 , M. Silari 2 1) LNF-INFN 2) CERN 3)IFP-CNR 4)LHEP-Bern Universität. Triple GEM detector Triple GEM detector for fast neutrons

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T riple GEM detector at CERN n_TOF facility

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  1. Triple GEM detector at CERN n_TOF facility • S.Puddu2,4, G.Claps1, G. Croci3, F. Murtas1,2, A.Pietropaolo3, C. Severino2,4, M. Silari2 • 1) LNF-INFN 2) CERN 3)IFP-CNR 4)LHEP-Bern Universität • Triple GEM detector • Triple GEM detector for fast neutrons • Triple GEM detector for thermal neutrons • Conclusion Silvia Puddu - n_TOF Collaboration Meeting - CERN 2012

  2. A triple GEM Chamber A Gas Electron Multiplier is made by 50 m thick kapton foil, with copper cladded on each side and perforated by an high surface-density of bi-conical channels; Several triple GEM chambers have been built in Frascati in the LHCbMuon Chamber framework 70 µm 140 µm GEM foil F. SauliNIM A386 531 M. Alfonsi et al., The triple-Gem detector for the M1R1 muon station at LHCb, N14-182, 2005 IEEE-NSS Silvia Puddu - n_TOF Collaboration Meeting - CERN 2012

  3. A Standard Triple GEM construction The detectors described in this talk are built starting form the standard 10x10cm2 : only one GEM foil has been modified to have central electrodes. G3 G2 G1 • FAST neutrons: 128 pads 6x12 mm2~ 100 cm2of sensitive area • THERMAL neutrons: 128 pads 3x6 mm2~ 25 cm2of sensitive area The GEM are stretched and a G10 frame is glued on top Silvia Puddu - n_TOF Collaboration Meeting - CERN 2012

  4. Beam Contamination by gammas Prompt g flash at ~ 600 ns E. Chiaveri et al, CERN n_TOF facility performance report,CERN-SL-2002-053 ECT (2002) C. Guerrero Sanchez, The neutron beam and the associated physics program of the CERN n_Tof facility, ATS seminar 108 107 106 105 104 103 102 10 (eV) 105 ~12 ms ~160 ms 104 F(dg/dlnt/cm2/pulse) ~4.7 ms ~63.7 ms 103 gfrom neutrons radiative capture in the beamdump + 102 “Slow” photons from several processes 10-7 10-6 10-5 10-4 10-3 10-2 10-1 Time(s) Thermal neutrons Fast neutrons Silvia Puddu - n_TOF Collaboration Meeting - CERN 2012

  5. Low Sensitivity to Photons Counts(Hz) HV scan with n_TOF and Cs137 with a gate of 1 second Photons Counts(Hz) Neutrons Workingpoint (870V) → gain ~ 300 HV(V) HV(V) Silvia Puddu - n_TOF Collaboration Meeting - CERN 2012

  6. How detect fast neutrons 200 m Neutrons interact withCH2, and, due to elastic scattering processes, protonsare emitted and enter in the gas volume generating a detectable signal. Aluminium thickness ensures the directional capability, stopping protons that are emitted at a too wide angle. S. Puddu et al., ieee record N21-4 Neutron converter 60 mm PE + 40 mm Al Gas mixture Ar-CO2 70%-30% Measurements near to the beam dump Silvia Puddu - n_TOF Collaboration Meeting - CERN 2012

  7. Measurements : beamimaging Instantaneous counts (10 msec) y x y x Constant: 3640 ± 40 Mean1: 5.9 ± 1.8 cm Mean2: 5.5 ± 1.8 cm Cumulative counts • Delay 2000 ns, HV 870 V, gate 10 ms • Two different intensity beams arrive to the facility Silvia Puddu - n_TOF Collaboration Meeting - CERN 2012

  8. Measurements : mean efficiency From proton beam monitor 49000 ± 1000 136000± 4000 Beam2 Mean efficiency 2.0 ± 0.1 e-4 Beam 1 Beam2 From GEMneutron monitor Beam1 10 ± 3 hits 26 ± 5 hits Silvia Puddu - n_TOF Collaboration Meeting - CERN 2012

  9. Measurements : energyscan The FPGA can detect neutrons vs a delay in time allowing to make a time (i.e. Neutron energy) scan thatallows the efficiency vs energy to be measured (uncertainty ~0.1 ÷1%, ~20% at 10 MeV ) . Number of neutrons acquired 3 MeV 10 MeV Number of neutrons detected 2 x10-4 100 keV Silvia Puddu - n_TOF Collaboration Meeting - CERN 2012 9

  10. How to detectthermal neutron Thermal Neutronsinteract with 10B, and alphas are emitted entering in the gas volume generating a detectable signal. Gas gap (Ar CO2) Alphas 10B (360 nm) Glass Support (1mm) Thermal neutrons Side-On detector Alphas Thermal neutrons Higher efficiency ~ 5% F. Murtaset al., ieeeworkshop record He-2-5 Silvia Puddu - n_TOF Collaboration Meeting - CERN 2012

  11. Monitor for fission reactor Measurements at Triga (ENEA)Power of 1 MW Gamma background freeWithout electronic noise Online plot top view Good linearity from 1W up to 1 MW Eff. = 4% Only Support Support with 10B Thermal neutrons Silvia Puddu - n_TOF Collaboration Meeting - CERN 2012

  12. N-TOF thermalneutron Beam spot online measurement Single event Cumulative counts Time spectrum (1ms/bin) 150ms gate With a scan procedure itis possible to make an image of the neutronbeam in the thermal region Silvia Puddu - n_TOF Collaboration Meeting - CERN 2012

  13. Conclusions • A triple GEM for fast neutrons has been tested at beam dump in n_TOFfacility at CERN • The GEM detector system is able to measure in real time the neutron beamspotwith almost complete rejection of gamma ray • The mean efficiency of this detector is 2 10-4 • The efficiency curve vs neutron energy was measured in the range 100 keV- 10 MeV • With a scan procedure itispossible to obtein the beamimaging for thermalneutrons • A new prototipe for thermalneutrons with 50%efficiency and 9cmwindowwill be ready in 01-2013 • Other GEM detectors was succesfully tested at ISIS spallation neutron source in UK and the Frascati Tokamak in Italy. Silvia Puddu - n_TOF Collaboration Meeting - CERN 2012 13

  14. Triple GEM detector: electronics readout FAST THERMAL • FAST neutrons: 128 pads 6x12 mm2~ 100 cm2 of sensitive area • THERMAL neutrons: 128 pads 3x6 mm2~ 25 cm2 of sensitive area • 8 chip CARIOCA to set the threshold on 16 channels and reshape the signal • FPGA-based DAQ: 128 scaler and TDC channels, in  gate and trigger, out  signals • HVGEM power supply with 7 independent channels and nano-ammeter Developed by G. Corradi D. Tagnani Electronic Group LNF-INFN Developed by A.Balla and G. Corradi and Electronic Group LNF-INFN Silvia Puddu - n_TOF Collaboration Meeting - CERN 2012

  15. Data Acquisition Silvia Puddu - n_TOF Collaboration Meeting - CERN 2012

  16. Triple GEM detector 70 mm 140 mm 50 mm • Particle conversion, charge amplification and signal induction zones are physically separated • Time resolution depends on geometry and gas: 9.7 nsfor Ar-CO2 (70-30) • Spatial resolution depends on geometry (up to 200 m), however is limited by readout • Dynamic range: from 1 to 108 particles/cm2 s • Effective gain is given by the formula: F. SauliNIM A386 531 M. Alfonsi et al., The triple-Gem detector for the M1R1 muon station at LHCb, N14-182, 2005 IEEE-NSS Silvia Puddu - n_TOF Collaboration Meeting - CERN 2012

  17. Triple GEM detector 3mm 1mm 2mm 1mm • Particle conversion, charge amplification and signal induction zones are physically separated • Time resolution depends on geometry and gas: 9.7 nsfor Ar-CO2 (70-30) • Spatial resolution depends on geometry (up to 200 m), however is limited by readout • Dynamic range: from 1 to 108 particles/cm2 s • Effective gain is given by the formula: F. SauliNIM A386 531 M. Alfonsi et al., The triple-Gem detector for the M1R1 muon station at LHCb, N14-182, 2005 IEEE-NSS Silvia Puddu - n_TOF Collaboration Meeting - CERN 2012

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