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Upgrade and progess on the COBRA double beta detector

Kai Zuber. Upgrade and progess on the COBRA double beta detector. Sudbury, 26. August 2010. - Introduction to COBRA - Current experimental status Physics results The pixel option COBRA Upgrade Summary. COBRA. Use large amount of CdZnTe Semiconductor Detectors.

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Upgrade and progess on the COBRA double beta detector

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  1. Kai Zuber Upgrade and progess on the COBRA double beta detector Sudbury, 26. August 2010

  2. - Introduction to COBRA • - Current experimental status • Physics results • The pixel option • COBRA Upgrade • Summary SNOLAB 2010

  3. COBRA Use large amount of CdZnTe Semiconductor Detectors Focus on 116Cd K. Zuber, Phys. Lett. B 519,1 (2001) SNOLAB 2010

  4. COBRA collaboration Technical University Dresden Technical University Dortmund University of Bratislava Material Res. Centre Freiburg University of Erlangen-Nürnberg University of Hamburg University of Jyvaskyla University of La Plata Laboratori Nazionali del Gran Sasso Czech TechnicalUniversity Prague Washington University at St. Louis JINR Dubna More welcome ? Other institutes: Louisiana State University, University of MIchigan SNOLAB 2010

  5. SNOLAB 2010

  6. Isotopes nat. ab. (%) Q (keV) Decay mode

  7. Advantages • Source = detector • Semiconductor (Good energy resolution, clean) • Room temperature • Modular design (Coincidences) • Two isotopes at once • Industrial development of CdTe detectors • 116Cd above 2.614 MeV • Tracking („Solid state TPC“) SNOLAB 2010

  8. Background S. Pirro, Milano Beyond 2.614 MeV background a priori much lower SNOLAB 2010

  9. 1024 pixel, pixel size: 625 m It‘s all about background Background from: natural radioactivity, cosmogenic produced radioisotopes, cosmic rays, neutrons Two options Energy measurement only Energy measurement and tracking SNOLAB 2010

  10. Setup at Gran Sasso Lab SNOLAB 2010

  11. LNGS spectrum SNOLAB 2010

  12. Results: Cd-113 4-fold non-unique beta decay (1/2+9/2+) first time theoretical model based on nuclear structure calculation(thanks to J. Suhonen) first time histogram of 1016yrshalf-lifemeasurements Q-value: J. V. Dawson et al., Nucl. Phys. A 818,264 (2009) Deviations with theory at lower energies SNOLAB 2010

  13. six half-life limits above 1020 years, one world best, six limits within factor 3 of world best Results: 0νDBD based on 18 kg days of data, J.V. Dawson et al., Phys. Rev. C 80, 025502 (2009)

  14. Coincidenceevents SNOLAB 2010

  15. The power of coincidences.. Leads to massive background reduction,but at the moment low efficiency Limits obtained not yet competitive with single detector results -> planned upgrade SNOLAB 2010

  16. Measuredspectrum Data taking with 16 red crystals finished, about 18 kg*d statistics Major background: Red paint on surface, radon Actions: Colourless painting (4 + 4 detectors, nitrogen atmosphere with radon trap) 116Cdpeak region Background at 2.8 MeV around 5 counts/keV/kg/yr ! SNOLAB 2010

  17. Region of interest – Raw data Region of 116Cd peak Data cleaning , analysis ongoing SNOLAB 2010

  18. COBRA - Pixel Idea: Massive background reduction by particle identification Alpha 200 μm pixel simulation For example Bi-214 : Time coincidence of both Electron 3 MeV Space and time coincidences possible 200 μm pixel simulation SNOLAB 2010

  19. Pixel size Reasonablerange (130Te) For 200 m 130Te and 116Cd would hit about 7-10 pixel SNOLAB 2010

  20. COBRA – Pixel CZT World largest CZT detector = 36 gramscollaboration with Zhong He (Univ. of Michigan) 20x20x5 mm3 systems8x8 pixels (running at LNGS Jan. –May 2010) 32x32 pixel system 100x100 pixel system Timepix system: 14x14x0.3 mm3 Si ( 2 systems) 14x14x1 mm3 CdTe (2 systems) 256x256 systems128x128 systems 20x20x15 mm3 11x11 pixel system Up to 40 slices in z by pulse information Running at LNGS from Sep. 2009-Jan. 2010 One system running in Felsenkeller Labsince Sep. 2009, one running at LNGSsince May 2010, before Modane Sudbury, 26.08.2010 SNOLAB 2010

  21. Polaris system (U Mich) preliminary Latest development on CZT 36 gram detector, 6 times larger than current COBRA detectors Pixelated in 11x11, Can be sliced in z up to 40 slicesdue to drift time

  22. Polarissystem Together with University of Michigan (group Zhong He) The power of pixels! Running at LNGS from Sep. 2009-Jan. 2010 Sudbury, 26.08.2010 SNOLAB 2010

  23. Polarissystem 116Cd peakregion No survivor after 125 days of data taking!!! Corresponds to a background between 2700-3000 keV of 0.9 counts/keV/kg/yr Detector not tuned for low background Sudbury, 26.08.2010 SNOLAB 2010

  24. 55 μm pixel Si Timepix device Timepix It reacts on environment, ie. not completely dominated by internalbackground

  25. A nicemuon A nice muon...

  26. Timepix 256x256 pixels, 55mm Alphas Muons Electrons Particle identification as background reduction tool works! SNOLAB 2010

  27. Picture show NO event in 117.5 days in energy range between 2.7 and 3 MeV which looks like 1(2) electrons SNOLAB 2010

  28. COBRA - Pixel Idea: Massive background reduction by particle identification Alpha 200 μm pixel simulation Bi-214 = Time coincidence of both Electron 3 MeV 55 μm pixel real event alpha electron alpha electron 200 μm pixel simulation SNOLAB 2010

  29. Yes we can! B. Obama Nobody said it was going to be easy, and nobody was right. George W. Bush

  30. COBRA Upgrade 2010/11 Upgrade to 64 CZT 1 cm3 detectors, about 0.42 kg (all detectors at hand) Single grid readout , i.e. pulse shaping Improved shielding , readout (new DAQ) , material selection Active veto (CsI), strongly enhances physics potential Aim : Background below 1 count/keV/kg/yr Running CZT in LSci Produce enriched CZT detectors Running a larger scale Polaris system and pixel systems SNOLAB 2010

  31. Pulse shape J. McGrath et al. , NIM A 615,57 (2010) Much more information in pulse shape 60Co pulse CPG detector works like a Frisch grid in wire chambersP. Luke , IEEE Trans. NS 42, 207 (1995) Single site event Multiple site event Experiment TCAD simulation Modification of preamps necessary... DoneFirst new preamps and two FADCs installed at LNGS this week SNOLAB 2010

  32. COBRA Upgrade Aim : Improve excited state and positron decay sensitivity by factor 10-30 128Te 1st excited state 116Cd 1st excited state Done for : NaI, CsI , BGO, CdWO4 Exploring various readout concepts Note: Can tolerate some impuritiesbecause of coincidencerequirement SNOLAB 2010

  33. Material screening (DLB) Factor of 1000 reduction with respect to unshielded SNOLAB 2010

  34. Bare crystals in LScintillator I SNOLAB 2010

  35. Bare crystals in LScintillator II

  36. Crystal growing done within the collaboration Crystal growing Preparation for growing enriched crystal/detector SNOLAB 2010

  37. King Cobra Measurement of 50 meV neutrino mass would require about 400 kgof CZT, isotopically enriched in Cd-116 Shielding must be ableto reduce background to less than 10-3 events /kg/keV/yr Plan is to have TDR by end of 2012 SNOLAB 2010

  38. Conclusion COBRA is a promising next generation experiment to explore double beta decay of Cd-116. First scientific results have been obtained , major upgrades planned in the nextyear Unique option would be the semiconductor tracker (solid-state TPC)in form of a pixel CZT, first measurements are very promising  The plan is to have a proposal for the large scale experiment ready by end of 2012 IWORID2010

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