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The NEXT experiment @Canfranc LSC

The NEXT experiment @Canfranc LSC

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The NEXT experiment @Canfranc LSC

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  1. The NEXT experiment @Canfranc LSC José Díaz IFIC-Valencia On behalf of the NEXT collaboration Paris, december 2008

  2. NEXT • Stands for Neutrino Experiment with a Xenon TPC • Will be installed in the Canfranc Underground Laboratory (LSC) • Has already been funded with 5 M Euro by the spanish goverment to develope the Physics at LSC Paris, december 2008

  3. Laboratorio Subterráneo de Canfranc (LSC) • It is placed at Canfranc, near the french border, in the spanish part of theSomport tunnel under the the Tobazo mountain • It has an equivalent depth of 2500 meters of water • LSC was inaugurated 26 March 2006 and depends on Aragon government, University of Zaragoza and Ministery of Education and Science Paris, december 2008

  4. Canfranc Underground Lab Hall A Paris, december 2008

  5. LSC Cosmic Background Paris, december 2008

  6. Neutrino mass possible patterns Normal Inverted Paris, december 2008

  7. Mass Hierarchy Possible evidence (best value 0.39 eV) “quasi” degeneracy ? >> m1 m2  m3 inverted normal cosmological disfavoured region (WMAP) Feruglio F. , Strumia A. , Vissani F. hep-ph/0201291 Paris, december 2008

  8. Neutrinoless double beta decay only forMajoranaNeutrinos ν = νc P P Left ν n n Left Phase Space 106x2νββ Paris, december 2008

  9. 0 experimental signature Other background sources: Separation from  improved by explicit 2e- signature Neutrinoless  decay  : Spike at the end-point of decay nucleus, convoluted with experimental resolution 2 : Continuous spectrum. Separation from  depends on detector resolution Paris, december 2008

  10.  Decay Rates 2=G2 |M2|2 0=G |M0|2 m2 • G0, G :calculable phase space factors • G ~ Q5 high Q value preferred • M0 , M2 : nuclear physics matrix elements  their values are model dependent  for final confirmation measurement with different isotopes • m: neutrino rest mass  How heavy is the neutrino? Theory & experiments tell us: T2≥1018 y and T0≥1025 y, but no strong correlations between these two!  We need large detector masses (~100 kg to multi-tons)! Paris, december 2008

  11. Double beta figure of merit Paris, december 2008

  12. 2 background and energy resolution An energy resolution better than 2-3% essential to make 2 background negligible Different reading devices give suitable energy resolution in TPC (~1%): LEMS, GEMS, Micromegas APD, PMT Very active R&D going on Micromegas, APD and PMT Paris, december 2008

  13. 238U … 222Rn (radon) … 214Bi 214Po 3.27 MeV g ou e-conv e- a (164 ms) 210Pb 232Th … 208Tl g or e-conv 4.99 MeV e- g de 2.614 MeV ou e-conv produced 100% of the times Non  backgroundsdue to Radioactive Natural Chains Paris, december 2008

  14. Non  backgrounds Paris, december 2008

  15. Non  backgrounds Paris, december 2008

  16. If 214Bi et 208Tl are present in the sources e- + g (Compton) e- + e- “Internal Backgrounds” e- + e-conv e- + e- e- (Möller) “External Background” If 214Bi et 208Tl are present in the environment g interacts with the source e- + e- (double Compton, or Compton + Möller) Non  backgrounds Neutrons produced around the detector can thermalize in a hydrogen-rich material and produce phtons by radioactive capture. Neutrons are produced by fission and from muon spallation. Muon induced neutron background must be well understood. Paris, december 2008

  17. Source Candidates Q (MeV) Abund.(%) Paris, december 2008

  18. Experimental approaches: Source = Detector (SED) Bolometers (Cuore, Cuoricino) and the “classical” Ge semiconductor detectors (IGEX, Heidelberg-Moscow, GERDA, MAJORANA,..) Also CZT detectors Advantages: Excellent energy resolution, excellent efficiency, compact. Disadvantages: No pattern signature (2e- not observed, but only total energy deposited), difficulty to reject non  background, limited to a single isotope per experiment. Paris, december 2008

  19. Cuoricino/Cuore TeO2 Bolometer: Source = Detector Heat sink: ~8-10 mK Thermal coupling: Teflon Thermometer: NTD Ge thermistor Absorber: TeO2 crystal • Cuoricino: • 52 TeO2 bolometers • Total detector mass: M ~ 11 kg 130Te • no enrichment • Started 2003 in Gran Sasso • Cuore: • 19 Cuoricino-like towers • Total detector mass: M ~200 kg • In the construction phase; start 2011 Paris, december 2008

  20. Cuoricino/Cuore 0.8 keV FWHM @ 46 keV 1.4 keV FWHM @ 0.351 MeV 2.1 keV FWHM @ 0.911 MeV 2.6 keV FWHM @ 2.615 MeV 3.2 keV FWHM @ 5.407 MeV the best  spectrometer so far 210Po a line Energy resolution of a TeO2 crystal of 5x5x5 cm3 (~ 760 g ) • Pros and cons: • very good energy resolution • acceptable costs • background handling very challenging ( surface contamination) Paris, december 2008

  21. Heidelberg-Moscow Results for Ge double beta decay 57 kg years of 76Ge data Apply single site criterion Paris, december 2008

  22. Source foils + tracker+ calorimeter B(25 G) 3 m 4 m Experimental approaches: Track-Calorimetry The tracks of both electrons are measured Advantages: Pattern signature observed, particle ID allows rejection of external backgrounds, several sources (or optimal source) in the same detector Disadvantages: Modest energy resolution due to calorimeter resolution and energy losses in source Paris, december 2008

  23. Track-Calorimetry Efficiency Efficiency is the convolution of many different factors: range out due to source foil thickness, magnetic field turning around tracks before they get to calorimeter, tracking algorithm efficiency, etc. Improving resolution requires minimizing a complicated function involving optimal foil thickness, magnetic field strength (or not magnetic field at all) and tracking algorithm(s) Paris, december 2008

  24. Optimal 0 detector • We would like to combine the advantages of good energy resolution with those of tracking capabilities. • This offers the best rejection capabilities of both 2 and external background • The isotope should be available at reasonable cost Paris, december 2008

  25. TPC of 136Xe: An attractive possibility 136Xe is a suitable nucleus to be used for a 0 experiment: Pressure can be fitted to optimize track length Xe can be easily enriched in 136Xe and is available from different companies The 2 mode has not been measured but has at least T1/2>2x1020 y Good energy resolution Paris, december 2008

  26. The NEXT (Neutrino Experiment with a Xenon TPC) Project • The NEXT collaboration was formed with the aim of proposing an experiment that could foster the Physics at Canfranc. • An experiment that could set the neutrino mass limit under 50 meV, has a good potential of discovery if Nature realizes the inverted hierarchy. It emerged that the suitable experiment would be a Xenon TPC housing 100 kg of 136Xe • Mainly spanish groups at present (UA Barcelona, CIEMAT Madrid, IFIC Valencia, U Santiago Compostela, U Zaragoza,but becoming international (Saclay, LBL, Coimbra?) Paris, december 2008

  27. Xenon TPCs for rare events • Xenon TPCs for different fields are becoming popular: • Gotthard experiment • EXO • XENON • MUNU Paris, december 2008

  28. Gotthard TPC Paris, december 2008

  29. Gotthard Data • Only 5 kg of 136Xe • T1/22>2.1x1020 y • T1/20>3.4x1023 y Paris, december 2008

  30. Readout grid for e- EXO EXPERIMENT • using liquid 136Xe (200 kg, 80% enriched) • currently in comissioning phase with natural Xe • detector is a TPC with ionization and light readout 40 cm 40 cm Paris, december 2008

  31. EXO: Energy Resolution Ionization: 1.8% @ 2.48 MeV Ionization + Scintillation: 1.4% @ 2.48 MeV They hope for better improvement for Exo-200 (better light collection). Paris, december 2008

  32. EXO GAS double beta counter Anode Pads Micro-megas WLS Bar Xe Gas Isobutane TEA Electrode Lasers . . . . . . . . . . . . . . . . Grids PMT For 200 kg, 10 bar, box is 1.5 m on a side Paris, december 2008

  33. Gas Properties • Possible gas – Xe + iso-butane + TEA • Iso-butane to keep electrons cold, stabilize micromegas/GEM • TEA • Converts Ba++ -> Ba+ • Q for TEA + Ba++->TEA+ + Ba+* ~ 0 • Converts 172 nm -> 280 nm? • ? Does it trap electrons? • ?Does it trap Ba+? Paris, december 2008

  34. Progress on energy resolution – Pure Xe, 2 Bar s = 0.6% Alpha spectrum at 2 b pressure. Paris, december 2008

  35. XENON Experiment • Dark Matter search • Dual Phase (Liquid+Gas) • Read by PMT • Atmospheric pressure • Radiopure Paris, december 2008

  36. NEXT concept • Pure Xenon TPC at high pressure • Pressure determined by tracking length • Scintillation light acts as trigger/mark of  events • A cylinder 1 m rdius and 1 m length would contain about • 100 kg of enriched xenon (70%) Paris, december 2008

  37. NEXT concept • With P=10 bar tracks are easily identified with 2 cm granularity • Tracks exhibit a typical boleadora pattern due to Bragg law Paris, december 2008

  38. NEXT concept • Background scales with surface but mass with volume • NEXT concept provides scalability to higher masses • Xenon can be obtained and enriched at reasonable cost (but increasing) Paris, december 2008

  39. Is NEXT competitive with current detectors in project or running? If we can achieve a energy resolution of 1 % FWHM and can control the background, the answer is YES! Sensitivities down to 60 meV for m are possible for NEXT-100 and down to 20 meV for NEXT-1000! Paris, december 2008

  40. Readout • Electroluminiscence light • PMT (Valencia) • APD (Barcelona) ) • Charge • Micromegas (Zaragoza) • GEMs,LEMs (Barcelona) Paris, december 2008

  41. Electroluminescence Theory: Light production is a linear process, while charge amplification is exponential  smaller fluctuations in light  better energy resolution 55Fe in Xe Paris, december 2008

  42. Electroluminescence 3% FWHM at 5 bar for 60 keV  only a factor ~2-3 worse than results with solid state detector (Coimbra Group) L.C.C. Coelho et al. NIM A 575 (2007) 444–448 Can we scale it???? Paris, december 2008

  43. Electroluminiscence Readout • PMTs: • R&D carried out by IFIC (Valencia) • PMTs available from DM experiments • Qeff≈ 25% @ 175 nm • R&D in progress to increase pressure range and improve radio purity • APDs: • R&D carried out by IFAE (Barcelona) in cooperation with Univ. Coimbra • Used in Exo experiment • Qeff≈ 100% @ 175 nm from API • R&D plans: measurements with mesh and THGEMs Paris, december 2008

  44. Barcelona Prototype • IFAE provided a design of a HP TPC • ~30 cm long, ~30 cm diameter • design for up to 10 bar • modular approach: readout technology can be “easily” exchanged and even cross-institute exchanges possible • pressure test was successfull: chamber did lose less than 0.1 bar over 1 month at 8.7 bar • Commissioning of first chamber under way Paris, december 2008

  45. Barcelona Prototype Paris, december 2008

  46. Barcelona Readout Paris, december 2008

  47. Zaragoza Measurements withMicromegas Paris, december 2008

  48. PMT Reading at Valencia • PMT out of xenon vessel to avoid degassing and contamination • A window transparent to UV light (175 nm) needed • Three prototypes forseen: NEXT-0-PMT, NEXT-1-PMT, NEXT-10 if chosen as readout technology by the collaboration Paris, december 2008

  49. NEXT-PMT-0 prototype Goals • Electronic treatment of the signal • Primary scintillation light in Xe • Secondary scintillation light • Energy resolution • High pressure system • Vacuum system Paris, december 2008

  50. Characteristics of NEXT-PMT-0 • Read out by 1 PMT outside the Xenon vessel • Vacuum system (rotatory+turbomolecular) able to reach 10-7 torr in reasonable time (6 h) • High pressure (10 atm) Xenon gas system • Vessel made of stainless steel with ultra-low degassing properties (Made by Vacuum-projects Ltd.) • 2 HV ports + ground port. Vacuum and temperature monitoring. Paris, december 2008