1. Erice, 20.9.2009Kai Zuber1 Status of the COBRA Experiment K. Zuber, TU Dresden

2. Erice, 20.9.2009Kai Zuber2 Contents General introduction Low background issues Pixel activities Summary and Outlook

3. Erice, 20.9.2009Kai Zuber3 COBRA Use large amount of CdZnTe Semiconductor Detectors large array of CdZnTe detectors K. Zuber, Phys. Lett. B 519,1 (2001)

4. Erice, 20.9.2009Kai Zuber4 COBRA collaboration Supporting institutes: Jagellonian University (Poland), Los Alamos Nat. Lab. (USA) TU Dresden TU Dortmund Laboratori Nazionali del Gran Sasso University of Bratislava Washington University at St. Louis Mat. Res. Centre Freiburg University of Erlangen University of Hamburg More welcome University of Jyvaskyla University of La Plata Czech Technical University Prague JINR Dubna

5. Erice, 20.9.2009Kai Zuber5 Isotopes nat. ab. (%) Q (keV)Decay mode

6. Erice, 20.9.2009Kai Zuber6 Advantages source = detector semiconductor (good energy resolution, clean) room temperature tracking („Solid state TPC“) modular design (coincidences) industrial development of CdTe detectors two isotopes at once 116 Cd above 2.614 MeV

7. Erice, 20.9.2009Kai Zuber7 Background COBRA beyond 2.614 MeV background a priori much lower S. Pirro, Milano

8. Erice, 20.9.2009Kai Zuber8 It‘s all about background 1024 pixel, pixel size: 625  m Background from: natural radioactivity, cosmogenic produced radioisotopes, cosmic rays, neutrons energy measurement only energy measurement and tracking two options

9. Erice, 20.9.2009Kai Zuber9 Gran Sasso (Italy) COBRAGERDA CUORE It‘s all about background reduction

10. Erice, 20.9.2009Kai Zuber10 COBRA Set-up at LNGS Designed for 64 detectors (at hand)

11. Erice, 20.9.2009Kai Zuber11 Results: Cd-113 We have more than 10 independent measurements now... first time theoretical model based on nuclear structure calculation (thanks to J. Suhonen) 4-fold non-unique beta decay (1/2 +  9/2 + ) first time histogram of 10 16 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. Erice, 20.9.2009Kai Zuber12 Results: 0νDBD based on 18 kg days of data, J.V. Dawson et al., Phys. Rev. C 80,025502 (2009) six half-life limits above 10 20 years, one world best, six limits within factor 3 of world best, coincidence analysis ongoing

13. Erice, 20.9.2009Kai Zuber13 Current status Background at 2.8 MeV around 5 counts/keV/kg/yr still options to improve Data taking with red crystals finished, now running 4 (8) clear painted detectors in a nitrogen atmosphere Cd-116 peak range Major background: Red paint and radon in the air

14. Erice, 20.9.2009Kai Zuber14 The solid state TPC energy resolution tracking pixelated CdZnTe detectors massive background reduction positive signal identification Semiconductor Tracker

15. Erice, 20.9.2009Kai Zuber15 Pixelisation 0   1-1.5mm ~15  m 3 MeV  7.7MeV  life-time = 164.3  s Beta with endpoint 3.3MeV  = 1 pixel,  and  = several connected pixel,  = some disconnected p. idea: massive background reduction by particle identification

16. Erice, 20.9.2009Kai Zuber16 Pixel detectors Pixel detector with 200  m pixels (10000 pixel) produced! 1024 pixel, pixel size: 625  m two options: Timepix, CZT ASICs

17. Erice, 20.9.2009Kai Zuber17 Option 1: ASICs for CZT Detectors: 2x2x0.5 cm 3 One 32x32 pixels sent for bonding to 1024 channel ASIC Second one 55x55 pixels sent for bonding to 2048 channel ASIC 64 pixel detectors Installation at LNGS winter 2009

18. Erice, 20.9.2009Kai Zuber18 Option 2: Timepix Medipix2 coll. Timepix Si, 300 μ m thick (data shown) TimePix CdTe detector 1mm thick  Both systems 256x256 Pixel, 55 μ m pitch, 1.4x1.4 cm 2 1mm Myon candidate

19. Erice, 20.9.2009Kai Zuber19 snapshot... 214 Bi alpha-beta coincidence candidate Unfortunately I can‘t show you a double beta event...

20. Erice, 20.9.2009Kai Zuber20 Event pool surface-u/g It reacts on environment, ie. not completely dominated by internal background

21. Erice, 20.9.2009Kai Zuber21 Particles.... Alphas Betas Muons

22. Erice, 20.9.2009Kai Zuber22 A nice muon...

23. Erice, 20.9.2009Kai Zuber23 Nobody said it was going to be easy, and nobody was right. George W. Bush Yes we can! B. Obama

24. Erice, 20.9.2009Kai Zuber24 Needed Sensitivity 50 meV

25. Erice, 20.9.2009Kai Zuber25 KING COBRA - Below 50 meV 116 Cd 116 In 116 Sn A real time low-energy solar neutrino and Supernova experiment? Threshold energy: 464 keV 7 Be contribution g.s. alone: 227 SNU  = 14s K. Zuber, Phys. Lett. B 571,148 (2003) K Balasi, P. Divari, T.Kosmas, J. Suhonen, E. Ydrefors,K. Zuber, in prep. e e e Current idea: 40x40x40 CdZnTe detectors = 420 kg, enriched in 116 Cd Down to 10 meV you might be...

26. Erice, 20.9.2009Kai Zuber26 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 data taken.

27. Erice, 20.9.2009Kai Zuber27