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Status of the COBRA Experiment

Status of the COBRA Experiment. K. Zuber, TU Dresden. Contents. General introduction Low background issues Pixel activities Summary and Outlook. COBRA. Use large amount of CdZnTe Semiconductor Detectors. large array of CdZnTe detectors.

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Status of the COBRA Experiment

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  1. Status of the COBRA Experiment K. Zuber, TU Dresden

  2. Contents • General introduction • Low background issues • Pixel activities • Summary and Outlook

  3. COBRA Use large amount of CdZnTe Semiconductor Detectors large array of CdZnTe detectors K. Zuber, Phys. Lett. B 519,1 (2001)

  4. COBRA collaboration TU Dresden TU Dortmund University of Bratislava Mat. Res. Centre Freiburg University of Erlangen University of Hamburg University of Jyvaskyla Washington University at St. Louis University of La Plata Czech Technical University Prague JINR Dubna Laboratori Nazionali del Gran Sasso More welcome Supporting institutes: Jagellonian University (Poland), Los Alamos Nat. Lab. (USA)

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

  6. 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“)

  7. Background COBRA S. Pirro, Milano beyond 2.614 MeV background a priori much lower

  8. 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

  9. Gran Sasso (Italy) GERDA COBRA CUORE It‘s all about background reduction

  10. COBRA Set-up at LNGS Designed for 64 detectors (at hand)

  11. 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) We have more than 10independent measurements now... first time histogram of 1016 yrs half-life measurements Q-value: J. V. Dawson et al., Nucl. Phys. A 818,264 (2009) Spectral shape fits better with unique 3-fold forbidden than non-unique transition

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

  13. Current status Major background: Red paint and radon in the air Data taking with red crystals finished, now running 4 (8) clear painted detectors in a nitrogen atmosphere Cd-116peak range Background at 2.8 MeV around 5 counts/keV/kg/yrstill options to improve

  14. The solid state TPC Semiconductor Tracker energy resolution tracking • massive background reduction • positive signal identification pixelated CdZnTe detectors

  15. Pixelisation • idea: massive background reduction by particle identification = 1 pixel,  and = several connected pixel, = some disconnected p. 3 MeV  0  ~15m 1-1.5mm 7.7MeV  life-time = 164.3s Beta withendpoint 3.3MeV

  16. 1024 pixel, pixel size: 625 m Pixel detectors two options: Timepix , CZT ASICs Pixel detector with 200 m pixels (10000 pixel) produced!

  17. Option 1: ASICs for CZT 64 pixel detectors Detectors: 2x2x0.5 cm3 One 32x32 pixels sent for bonding to 1024 channel ASIC Second one 55x55 pixels sent for bonding to 2048 channel ASIC Installation at LNGS winter 2009

  18. Option 2: Timepix Medipix2 coll. • Timepix Si, 300μm thick (data shown) • TimePix CdTe detector 1mm thick  Both systems 256x256 Pixel, 55μm pitch, 1.4x1.4 cm2 1mm Myon candidate

  19. snapshot... 214Bi alpha-beta coincidence candidate Unfortunately I can‘t show you a double beta event ...

  20. Event pool surface-u/g It reacts on environment, ie. not completely dominated by internalbackground

  21. Particles.... Muons Alphas Betas

  22. A nice muon...

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

  24. Needed Sensitivity 50 meV

  25. A real time low-energy solar neutrino and Supernova experiment? e Threshold energy: 464 keV e e 7Be contribution g.s. alone: 227 SNU 116In = 14s 116Cd 116Sn K. Zuber, Phys. Lett. B 571,148 (2003) K Balasi, P. Divari, T.Kosmas, J. Suhonen, E. Ydrefors,K. Zuber, in prep. KING COBRA - Below 50 meV Current idea: 40x40x40 CdZnTe detectors = 420 kg, enriched in 116Cd Down to 10 meV you might be ...

  26. Summary • COBRA is a rather new approach making use of CZT room temperature semiconductors. • First background sources have been identified and removed, working towards larger array (64), lower background. Major upgrade spring in 2010. • The solid state TPC (semiconductor tracker) can be the major and unique step forward. First underground datataken.

  27. Join the Party!

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