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Liquefied Noble Gas Detectors for Low Energy Particle Physics

Liquefied Noble Gas Detectors for Low Energy Particle Physics. Vitaly Chepel. LIP-Coimbra and Department of Physics University of Coimbra, Portugal. V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013. Main source of the talk. JINST 8 (2013) R04001.

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Liquefied Noble Gas Detectors for Low Energy Particle Physics

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  1. Liquefied Noble Gas Detectors for Low Energy Particle Physics Vitaly Chepel LIP-Coimbra and Department of Physics University of Coimbra, Portugal V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  2. Main source of the talk JINST 8 (2013) R04001 If not given on the slides, see this paper for references V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  3. Outline • Dark Matter (DM) and coherent neutrino scattering (CNS) cases from the detection point of view (very short – much has been said by other speakers already) • II. On physics of the detection processes at low energies: what we knew, what we have discovered and what we still need to learn • III. Short review of DM and CNS experiments using liquefied noble gases V. Chepel V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  4. DM versus CNS V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  5. Expected integral rates (thanks to E.Santos) Practical thresholds V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  6. WIMP Search Technology Zoo Ionisation Detectors Targets: Ge, Si, CS2, CdTe CoGeNT, DRIFT, DM-TPC GENIUS, HDMS, IGEX, NEWAGE Light & Ionisation Detectors Targets: Xe, Ar ArDM, LUX, WARP, XENON, ZEPLIN cold (LN2) Heat & Ionisation Bolometers Targets: Ge,Si CDMS, EDELWEISS cryogenic (<50 mK) ionisation Q L scintillation H phonons Scintillators Targets: NaI, Xe, Ar ANAIS, CLEAN, DAMA, DEAP, KIMS, LIBRA, NAIAD, XMASS, ZEPLIN-I Bolometers Targets: Ge, Si, Al2O3, TeO2 CRESST-I, CUORE, CUORICINO Bubbles & Droplets CF3Br, CF3I, C3F8, C4F10 COUPP, PICASSO, SIMPLE Light & Heat Bolometers Targets: CaWO4, BGO, Al2O3 CRESST, ROSEBUD cryogenic (<50 mK) (credit H.Araújo) V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  7. LNG detectors: a bit of history First papers: + hundreds of further papers + achievements in understanding LNG physics + technology developments + some disappointments All this has resulted in a series of large scale detectors now working at the cutting edge of science V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  8. DM double phase detectors: important steps Foundations of the double-phase technique for particle detection: First proposal for using double-phase detectors for WIMP search: Proposed background discrimination by using both scintillation and ionisation signals: V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  9. First LNG dark matter detectors DAMA - First single phase detector ZEPLIN-II - First double phase detector V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  10. Operation principle of a double-phase electroluminescence detector Primary scintillation Secondary scintillation (proportional to extracted charge) S2/S1 ratio – the basis for elctron/nuclear recoil discrimination in double phase detectors PMTs V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  11. Scintillation – a closer look Two mechanisms ionization electrons direct excitation recombination Similar emission field dependent V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  12. Scintillation – a closer look Xe - Xe+ Xe – Xe* Xe2*  Xe + Xe + hv Xe - Xe V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  13. Scintillation – a closer look E, eV Xe - Xe+ Xe – Xe* l3 l1 V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  14. Scintillation – a closer look The transitions are undistinguishable spectroscopically but allowed  short lifetime (LXe ~ 2.2 ns; LAr ~5 ns) forbidden  long lifetime (LXe ~ 27 ns; LAr ~1600 ns; LNe ~15 ms; LHe ~13 s) The population of the singlet and triplet states also depends on particle kind Nuclear recoils can be distinguished from electrons using pulse shape discrimination V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  15. Scintillation – a closer look Pulse shape discrimination 1600 ns (45 ns?) Slow recombination (~35-45 ns) Fast recombination (~1 ns) V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  16. PSD in LXe Scintillatuion pulse shape discrimination in LXe (XMASS) 137Cs 252Cf Prompt/total ph.e. ratio XMASS prototype (K. Ueshima, PhD thesis. 2010) V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  17. PSD in LXe (XMASS) 4.8-7.2 keVee 4.8-7.2 keVee 9.6-12 keVee Ueshima, e.a., NIMA659(2011)161 V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  18. PSD in LAr nuclear recoils electron nuclear electron recoils Prompt fraction (F) = Nph(fast) / Nph(total) 90 ns integration a few ms integration D-D neutron generator (Lippincott e.a., PRC78(2008)035801) XMASS V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  19. Light yield – depends on particle and energy all excitons recombine Too many excitons  bi-excitonic quenching e- Electrons escape recombination (Doke/Hitachi interpretation) V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  20. Light yield – different behaviour at low energies e- Less light for low energies Less light for nuclear recoils dE/dx is not a good parameter for low energies V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  21. Scintillation yield for electrons and g-rays LXe Anomaly ! (9.4 keV g; 83mKr) Relative yield Absolute yield same data  e- e- Data from g - Szydagis, e.a., JINST 6(2011)P10002 – evaluated yield (absolute) e - Aprile, e.a., PRD 86(2012)112004 – Compton electrons; relative yield; re-normalized by me at 122 keV Baudis, e.a., PRD 87(2013)115015 – Compton electrons; relative yield; 1)g e- 2) Anomalous behaviour can happen for some sources Must be careful with detector calibration ! V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  22. Field dependence of light yield LXe 56.5 keV nucl. recoils (*) S1 threshold (for electrons) ~10 keV  (Baudis, 2013) Light yield, a.u. 122 keV g (*) 1 MeV e- (**) (estimated in Baudis, 2013) For nuclear recoils, ~10 keV threshold was used by XENION100 and ZEPLIN-III * Aprile e.a., PRL97(2006)081302 ** Kubota e.a., PRB20(1979)3486 V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  23. Scintillation efficiency for nuclear recoils in LXe 1 is for 122 keV g-rays (57Co) At zero field ! LXe or (Compilation by Horn, e.a. PLB705 (2011) 471) V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  24. Scintillation efficiency in LAr and LNe LNe LAr Gastler e.a., PRC85(2012)085811 Hitachi’04 (theor.) Regenfus e.a., J.Phys:Conf.Ser375(2012)12019 Lippincott e.a. PRC86(2012)015807 V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  25. Ws value for LAr and LXe recent ~5 keV 211 recent (see Chepel and Araújo 2013 for references)

  26. Energy partition ionization Particle energy excitation heat (Platzman equation) Electrons: Ions (atoms) lose their energy in electronic and nuclear collisions: Lindhard’s partition function:  0.1–0.2 for Enr 10 keV in LXe Does W makes sense for nuclear recoils? (Dahl’2009) withEnr  100 – 200 eV 15.6 eV for electrons cf V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  27. Ionization yield from nuclear recoils 200 eV/e- Notice weak field dependence 0.27  2 kV/cm 0.1  2 kV/cm Aprile e.a.,2006 V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  28. Charge/light vs electric field light charge nr electrons nr Aprile e.a., 2006 V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  29. Field dependence of free charge yield LXe • Notice: • weak field dependence • increase of the yield at low energies Extrapolated from E~10 kV/cm using Jaffé model (Obodovski) V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  30. Nelectrons due to nuclear recoils Exp. data (different fields but dependence on the field is weak) LXe Roughly, i.e. favours low energies The yield is smaller than for electrons even after correction for nuclear collisions suggested (Dahl’2009) Compressed gas model Wnr Solid state model Fundamental limit I=12.13 eV or Eg=9.28 eV SRIM prediction V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  31. More electrons escape at low E (r – recombining fraction at zero field) 2 10 20 30 Enr, keV LXe Bezrukov, e.a. AP35(2011)119 V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  32. Nuclear recoil tracks in LXe LXe ER = 100 keV Electron thermalization length (Mozumder, 1995) (simulated with TRIM) V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  33. Nuclear recoil “track” details LXe ER = 100 keV Primary particle Secondary recoils Track endpoint 100 nm V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  34. Nuclear recoil “track” details LXe Primary particle Secondary recoils Track endpoint ER = 100 keV 100 nm V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  35. Simulated electron tracks LXe thermalization distance 4.5 mm Less light and more charge should be observed for lower energies 4 mm Electrons, E=30 keV (PENELOPE 2011) V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  36. Simulated 0.5 MeV electron tracks LXe 500 mm Thermalization sphere Simulated with PENELOPE (Courtesy V. Solovov) V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  37. Ionization and drift parameters ~200 eV for nuclear recoils, if Nex/Ni = 1 (assumed Se/Sn0.12) hole mobility LXe is “more solid” than LAr V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  38. Electron emission to gas Worked very well - no big surprises ! Model by Bolozdynya NIMA422(1999)314 Eth Gushchin e.a., JETP55(1982)860 Two emission mechanisms: ‘hot’ emission – prompt for e > Vo ‘thermal’ emission – thermal evaporation Delayed emission observed, more significant in LAr V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  39. Secondary scintillation in gas Well established linear dependence (n – number density) For saturated vapour  simple parametrization: V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  40. Single electron spectrum This is how ZEPLIN-III sees a single electron Sensitivity of the ionization channel = 1 electron (if it is extracted from the track, did not get captured by an impurity molecule and succeded to cross the potential barrier on the liquid surface) ZEPLIN-III: ~300 secondary scintillation photons per extracted electron V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  41. Single electron noise - origins SE signal correlated with preceding scintillation - Photoionization SE signals with no apparent correlation with preceding scintillation – possibly delayed emission of electrons trapped under the liquid surface and autoemission from the cathode wires Time between scintillation and SE pulse 20 ms without signals Rate 5.7 s-1 within the central area of ZEPLIN-III containing 1.3 kg of LXe LXe bulk cathode wires Previous irradiation of the detector does affect the rate Santos e.a., JHEP12(2011)115 V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  42. Single electron noise (cont.) (Sangiorgio e.a., arXiv1301.4290) Single electron spectrum in a small LAr chamber (double phase) following accidental discharges - the rate decreased with time V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  43. Sub-keV electrons in LAr (Sangiorgio e.a., arXiv1301.4290) General comment: Thomas-Imel box model seems to provide useful framework to describe recombination at low energies (there are several other papers in which this parametrization was successfully used) Fit with Thomas-Imel model V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  44. Summary (before going to experiments) • Scintillation: • determines energy threshold in DM search experiments (5-10 keVnr in LXe, currently) • provides energy scale for nuclear recoils • needs to be better studied for low energy (10 keV) electrons and g-rays to understand backgrounds and make feasible in-volume calibration (e.g., with 37Ar and 83mKr) • Ionization: • surprise: high charge yield from nuclear recoils, weak field dependence • need to understand recombination better (e.g., the role of escape electrons) and initial ionizations/excitations share • if measured via secondary scintillation in gas may provide sensitivity as low as few electrons (probably down to ~200 eV for nuclear recoils in LXe) V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  45. Summary (before going to experiments) • Drift: • sufficient electron life time is routinely achieved • drift velocity well measured • Emission: • Not everything is clear but no troubles in practice • Secondary scintillation in gas: • OK, plenty of light (e.g., 300 ph./electron – in ZEPLIN-III) • provides sensitivity to single electrons extracted from the liquid • Single electron noise: • origins need to be understood • no problem for DM search experiments • trouble for coherent scattering of neutrino V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  46. LXe DM ZEPLIN-III Planar geometry high field (3–4 kV/cm) with two electrodes Scint. threshold - 7 keVnr; ionization – set to 5 electrons Electron recoil rejection efficiency – 99.99% - the best reported for LXe Status – completed Next: LZ  ~7t V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  47. LXe DM XENON100 178 PMTs Bulk geometry good self-shielding (~5 mdru in 34 kg fiducial) Scint. threshold 6 keVnr Electron recoil rejection efficiency – 99.5% Status – 225 live days DM data published – the best exclusion limit Two events in the band 6.6-30.5 keVnr, consistent with expected background Next: XENON 1t --- see Alexey Lyashenko’s talk V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  48. LXe DM LUX350 61x2 PMTs Bulk geometry good self-shielding (~0.8 mdru expected in 100 kg fiducial) Thin-wall Ti vessel for low background 300 t ultrapure water tank viewed by PMTs Status – deployed underground  Ask Vladimir Solovov for details Next: LZ ~7t V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  49. LXe DM XMASS 649 PMTs Spherical geometry, scintillation only;800 kg of LXe, 100 kg fiducial e/n rejection (PSD) 92% at 5 keVnr, 99.9% at 15 keVnr (at 50% recoil acceptance) 15.9 ph.e./keV at the centre – the highest response Status – running Next: 20t of LXe V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

  50. LAr DM WARP140 37 Bulk geometry; 140 kg of isotopicaly pure argon (natural Ar contains long living 39Ar, ~1 s-1 kg-1) TPB wavelength shifter deposited on all surfaces (LAr scintillates at 127 nm) Dual discrimination: S1 pulse shape + S2/S1 ratio  very good rejection power LAr active volume / LAr active shield / LAr coolant Status – ? V. Chepel Dark Matter, Dark Energy and their Detection, Novosibirsk, 25 July 2013

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