upgrade and progess on the cobra double beta detector sudbury, 26. august 2010 kai zuber

Upgrade and progess on the COBRA double beta detector

Sudbury, 26. August 2010

Kai Zuber

K. ZuberSudbury, 26.08.2010 SNOLAB 2010

- Introduction to COBRA- Current experimental

status- Physics results- The pixel option- COBRA Upgrade- Summary


COBRA

Use large amount of CdZnTe Semiconductor Detectors

K. Zuber, Phys. Lett. B 519,1 (2001)

Focus on 116Cd


Technical University Dresden Technical University Dortmund

Laboratori Nazionali del Gran Sasso

University of Bratislava

Washington University at St. Louis

Material Res. Centre FreiburgUniversity of Erlangen-NürnbergUniversity of Hamburg

University of Jyvaskyla

University of La Plata

Czech TechnicalUniversity Prague

JINR Dubna

COBRA collaboration

More welcome ?Other institutes: Louisiana State University, University of MIchigan

K. Zuber

Isotopes

Zn70 0.62 1001 ß-ß- Cd114 28.7 534 ß-ß- Cd116 7.5 2809 ß-ß- Te128 31.7 868 ß-ß- Te130 33.8 2529 ß-ß- Zn64 48.6 1096 ß+/EC Cd106 1.21 2771 ß+ß+ Cd108 0.9 231 EC/EC Te120 0.1 1722 ß+/EC

nat. ab. (%)Q (keV)

Decay mode


• 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

• 116Cd above 2.614 MeV

Advantages

K. ZuberSudbury, 26. 08.2010 SNOLAB 2010

Beyond 2.614 MeV background a priori much lower

Background

S. Pirro, Milano


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


Setup at Gran Sasso Lab


LNGS spectrum


Results: Cd-113

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 1016 yrs half-life measurements

Q-value:

J. V. Dawson et al., Nucl. Phys. A 818,264 (2009)

Deviations with theory at lower energies

K. Zuber

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 1020 years, one world best, six limits within factor 3 of world best


Coincidence events


The power of coincidences..

130Te 130Xe 2e (536keV )

Leads to massive background reduction,but at the moment low efficiencyLimits obtained not yet competitive with single detector results-> planned upgrade


Background at 2.8 MeV around 5 counts/keV/kg/yr !

Data taking with 16 red crystals finished, about 18 kg*d statisticsMajor background: Red paint on surface, radon

116Cdpeak region

Measured spectrum

Actions: Colourless painting (4 + 4 detectors, nitrogen atmosphere with radon trap)


Region of 116Cd peak

Region of interest – Raw data

Data cleaning , analysis ongoing


Idea: Massive background reduction by particle identification

200 μm pixel simulation

For example Bi-214 :Time coincidence of both

Alpha

Electron 3 MeV


COBRA - Pixel

Space and time coincidences possible


Pixel size

(130Te)

Reasonablerange

For 200 m 130Te and 116Cd would hit about 7-10 pixel

K. Zuber

20x20x5 mm3 systems8x8 pixels (running at LNGS Jan. –May 2010)32x32 pixel system100x100 pixel system

Timepix system:14x14x0.3 mm3 Si ( 2 systems)14x14x1 mm3 CdTe (2 systems)256x256 systems128x128 systems

World largest CZT detector = 36 gramscollaboration with Zhong He (Univ. of Michigan)

20x20x15 mm3

11x11 pixel systemUp to 40 slices in z by pulse informationRunning at LNGS from Sep. 2009-Jan. 2010One system running in Felsenkeller Lab

since Sep. 2009, one running at LNGSsince May 2010, before Modane

COBRA – Pixel CZT

Sudbury, 26.08.2010 SNOLAB 2010

K. Zuber

Latest development on CZT

36 gram detector,6 times larger than current COBRA detectors

preliminary

Pixelated in 11x11,Can be sliced in zup to 40 slicesdue to drift time

Polaris system (U Mich)

K. Zuber

Polaris system

The power of pixels!

Together with University of Michigan (group Zhong He)


Running at LNGS from Sep. 2009-Jan. 2010

K. Zuber

No survivor after 125 days of data taking!!! Corresponds to a background between 2700-3000 keVof 0.9 counts/keV/kg/yr

Detector not tuned for low background

Polaris system

116Cd peakregion


K. Zuber

Timepix

It reacts on environment, ie. notcompletely dominated by internalbackground

55 μm pixel Si Timepix device

K. Zuber

A nice muon...

A nice muon


Timepix

Electrons

Particle identification as background reduction tool works!

256x256 pixels, 55m

MuonsAlphas


Picture show

NO event in 117.5 days in energy range between 2.7 and 3 MeV which looks like 1(2) electrons


Idea: Massive background reduction by particle identification


Bi-214 =Time coincidence of both

alpha electron

alpha

electron

Alpha

Electron 3 MeV


55 μm pixel real event

COBRA - Pixel

K. Zuber

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


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 selectionActive veto (CsI), strongly enhances physics potentialAim : Background below 1 count/keV/kg/yr

Running CZT in LSciProduce enriched CZT detectorsRunning a larger scale Polaris system and pixel systems


Pulse shape

Much more information in pulse shape

CPG detector works like a Frisch grid in wire chambersP. Luke , IEEE Trans. NS 42, 207 (1995)

60Co pulse

Experiment

TCAD simulation

Single site event Multiple site event

J. McGrath et al. , NIM A 615,57 (2010)

Modification of preamps necessary... DoneFirst new preamps and two FADCs installed at LNGS this week


COBRA Upgrade

Aim : Improve excited state and positron decay sensitivity by factor 10-30

Done for :NaI, CsI , BGO, CdWO4

Exploring various readout concepts

Note: Can tolerate some impuritiesbecause of coincidencerequirement

128Te 1st excited state116Cd 1st excited state


Material screening (DLB)

Factor of 1000 reduction with respect to unshielded


Bare crystals in LScintillator I

K. Zuber

Bare crystals in LScintillator II

K. Zuber

Crystal growing

Crystal growing done within the collaboration

Preparation for growing enriched crystal/detector



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

K. ZuberCambridge, 14.07.2010 IWORID2010

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 nextyearUnique 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

upgrade and progess on the cobra double beta detector sudbury, 26. august 2010 kai zuber

Documents

cd iworid

upgrade iworid

milano iworid

mevadvantages iworid

university of michigan

world best iworid

radon trap iworid

kai zuber iworid