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Neutron scattering systems for calibration of dark matter search and low-energy neutrino detectors

International conference: Dark matter, dark energy and their detection, 22-26 July 2013. Neutron scattering systems for calibration of dark matter search and low-energy neutrino detectors

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Neutron scattering systems for calibration of dark matter search and low-energy neutrino detectors

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  1. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 Neutron scattering systems for calibration of dark matter search and low-energy neutrino detectors A.Bondar, A.Buzulutskov, A.Burdakov, E.Grishnjaev, A.Dolgov, A.Makarov, S.Polosatkin, A.Sokolov, S.Taskaev, L.Shekhtman Novosibirsk State University Budker Institute of Nuclear Physics SB RAS Novosibirsk State Technical University

  2. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 Outline: A problem of calibration of WIMP detectors Neutron scattering systems for liquid noble gas detector calibration - based on DD generator - based on p7Li generator

  3. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 R.W.Schnee, arXiv: 1101.5205v1 - most probable WIMP incident energy WIMPs (weakly interacting massive particles) are a one possible candidate for Dark Matter Theoretical models predict a mass of WIMPs in the range 10-1000 GeV/c2 WIMPs expected to interact with matter by elastic scattering with production on recoil nucleus with energies ~1-100 keV, the recoil spectrum depend on mass of the WIMP and detector velocity in the Galaxy frame Recoils spectrum measurements are required for estimation of WIMP mass and interpretation of experimental data

  4. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 R+A*R+A+hn R+A++e R+A’ e+A*e+A+hn e+A++e R+A e+A Recoil spectrum measurements require calibration that is establishing of energy scale of detector response Such calibration can be done by measuring of detector response from particles produced recoil nucleus with know energy A response to electrons and recoil nucleus is different for ionization and scintillation detectors This difference often specified by quenching factor Leff: Ee [keVee] = Leff × Er [keVnr] Electrons (gammas) Nucleus

  5. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 Data of ionization and scintillation quenching factors below 10 keV for liquid noble gases are insufficient and controversial Scintillation quenching factors Ar Xe Ne D.Gastler et al. // Phys. Rev. C. 2012. V. 85. 065811 A.Manzur et al. // Phys. Rev. C. 2010. V. 81. 025808. Lippincott W.H. et al. // Phys. Rev. C. 2012. V. 86. 015807

  6. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 CrAD detector of dark matter The project of two-phase avalanche cryogenic detector suitable for DM search have proposed in Budker INP The prototype of the detector is constructed in the Laboratory of Cosmology and Elementary Particle Physics of NSU The prototype will be applied for measurements of quenching factors in the noble gases for recoil energy range 1-100 keV Volume: 50 l Working gases: Ar, Xe, Ne, He Sensitivity: up to single electron (~100 eV) Spatial resolution: ~1 mm Measurements: both scintillation (bottom PTMs) and ionization (side PMTs) A.Buzulutskov et al. // this conf.

  7. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 Scintillation detector of scattered neutrons Liquid argon Neutron source q Scattering event DM detector calibration scheme Primary recoil nucleus required for detector calibration can be produced by neutrons Recoils is produced by elastic scattering on neutrons A source of neutrons with constant energy and low divergence is required

  8. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 Neutron sources • Isotopes (252Cf) • Nuclear reactor • DD neutron generator (2.45 MeV) • p7Li neutron generator Wide spectrum of neutrons

  9. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 DD neutron generator Utilizes nuclear fusion reaction D(D,n)3He (En=2.45 MeV) Industrial neutron generators with neutron yield 106 n/s is produced for geophysical applications Neutron spot size ~1 mm DD neutron generator (produced by Budker INP)

  10. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 Energy of Ar recoils Recoil energy, keV Scattering angle, deg. DD neutrons scattering Elastic scattering: n+Arn+Arrec Inelastic scattering: n+Arn+Ar*n+Arrec+g(1.46 MeV) Cross-section of scattering Cross-section, barn Scattering angle, deg.

  11. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 Neutron generator Water-filled tank Scintillation detectors of scattered neutrons Pulse height spectrum (90 scattering) Count rate, 10-10 keV-1 Active region of WIMP detector Recoil energy, keV DD scattering system Neutron generator: 106 n/s Scintillators: slilbene Water shield: 40 cm Baseline: 80 cm Count rate of scattering events ~0.1 min-1

  12. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 Neutron generator Water-filled tank Scintillation detectors of scattered neutrons Active region of WIMP detector Background suppression Neutron background (random coincidence): - Neutron collimation Cosmic ray background: - Pulse shape discrimination (scintillation detector)

  13. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 w/o neutrons w/ neutrons 2.45 MeV Time, ns Pulse shape discrimination Scintillation pulses from gammas and neutrons in stilbene have different shape and can be effectively distinguished

  14. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 Neutron generator Water-filled tank Scintillation detectors of scattered neutrons Active region of WIMP detector Calibration in low-energy range Calibration below 10 keV is a challenge: -Increase of “geometric” errors for low-angle scattering: -Failure to shield scintillation detector from neutron source

  15. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 Neutron generator Water-filled tank Scintillation detectors of scattered neutrons Active region of WIMP detector Calibration in low-energy range Calibration below 10 keV is a challenge: -Increase of “geometric” errors for low-angle scattering: -Failure to shield scintillation detector from neutron source

  16. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 Calibration by inelastic scattering Recoils energy for inelastic scattering to small angle tend co constant value -8.3 keV Energy of Ar recoils Recoil energy, keV Escape of “geometric” error allow to increase solid angle of scintillation detector without loss of accuracy 100 times gain in count rate is estimated Recoils with energy 1.2 keV can be produced with 14 MeV DT neutrons Scattering angle, deg. Pulse height spectrum for small-angle scattering

  17. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 Neutron generator Water-filled tank Scintillation detectors of scattered neutrons Active region of WIMP detector Calibration in low-energy range Calibration below 10 keV is a challenge: -Increase of “geometric” errors for low-angle scattering: -Failure to shield scintillation detector from neutron source

  18. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 Generator of tagged neutrons Neutron generating reaction: D+Dn(2.45 MeV)+3He(0.8 MeV) Recorded by build-in detector Tagged neutron generator should provide effective trigger for suppression of random coincidence The generator of tagged neutrons in under development in Budker INP

  19. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 p7Li neutron generator Generator of epithermal neutrons in the reaction 11B(p,n)11Be have been developed in Budker INP for medical applications (neutron cancer therapy) Tandem accelerator H- ion source Proton beam: 1.9 MeV, 3 mA HV power supply Neutron yield 1011 n/s

  20. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 p7Li neutron generator Generator of epithermal neutrons in the reaction 7Li(p,n)7Be have been developed in Budker INP for medical applications (neutron cancer therapy)

  21. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 p7Li neutron generator 7Li(p,n)7Be: reaction threshold 1.822 MeV Neutron energy is determined by beam energy and neutron escape direction Operation point En=77 keV Neutron energy, keV Neutron escape direction, degrees

  22. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 p7Li neutron generator Operation point for Ar detector calibration: q=110, Ep=2.077 MeV, En=77 keV 40Ar have a peak of scattering cross-section on 77 keV Sulphur filter can be applied for additional monochromatization The system produces Ar recoils in the range 0 - 7.5 keV Scattering cross-section, barn Neutron energy, keV

  23. International conference: Dark matter, dark energy and their detection, 22-26 July 2013 Conclusion Neutron scattering systems for calibration on liquid cryogenic detectors are under development in the Laboratory of Cosmology and and Elementary Particle Physics of NSU The systems will allow to measure ionization and scintillation yield for liquid noble gases in the range of recoil energies 0.5-200 keV

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