PROJECT STATUS AND PERSPECTIVES

Transcription

1 COBRA CdZnTe 0-NEUTRINO BETA-BETA RESEARCH APPARATUS PROJECT STATUS AND PERSPECTIVES DATE JULY 28, 2011 BY JERRAD MARTIN

2 Agenda Introduction to COBRA Past Results Status of Current R&D PROJECT STATUS AND PERSPECTIVES DATE JULY 28, 2011 BY JERRAD MARTIN

3 Neutrinoless Double Beta Decay (0νββ) ( Z, A ) ( Z + 2, A ) + 2e e Dependent on neutrino rest masses ( / ) = νe _ νe 0νββ-decay e T1/2 > years! A unique signature No ν s means β s carry all of the kinetic energy

4 Cadmium Zinc Telluride Source = detector Multiple isotopes 116 Cd above MeV Room temperature Modular Semiconductor Maturing technology / Isotope % Abun Q (kev) Mode Zn β - β - Cd β - β - Cd β - β - Te β - β - Te β - β - Zn β + /EC Cd β + β + Cd EC/EC Te β + /EC

5 Cadmium Zinc Telluride Source = detector Multiple isotopes / 116 Cd above MeV Room temperature Modular Semiconductor Maturing technology Isotope % Abun Q (kev) Mode Zn β - β - Cd β - β - Cd β - β - Te β - β - Te β - β - Zn β + /EC Cd β + β + Cd EC/EC Te β + /EC

6 Cadmium Zinc Telluride Source = detector Multiple isotopes / 116 Cd above MeV Room temperature Modular Semiconductor Maturing technology Isotope % Abun Q (kev) Mode Zn β - β - Cd β - β - Cd β - β - Te β - β - Te β - β - Zn β + /EC Cd β + β + Cd EC/EC Te β + /EC

7 76 Ge 130 Te 116 Cd COMPARISON OF 0νββ BACKGROUNDS SPEC FROM: NPGROUP.PD.INFN.IT/LUNA/DESCRIPTION-EN.HTML

8 Cadmium Zinc Telluride Source = detector Multiple isotopes 116 Cd above MeV Room temperature Modular Semiconductor Maturing technology

9 Cadmium Zinc Telluride Source = detector Multiple isotopes / 116 Cd above MeV Room temperature Modular Semiconductor Si, Ge Detectors h h e e CZT Detector _ + _ Maturing technology e e +

10 Detector Technologies Coplanar Grid CZT Good energy resolution Simple readout 2 anodes, 1 cathode No location of interaction info Pixelated CZT Superior energy resolution Strong small pixel effect 3D LOI information 2D from pixels, depth from A/C Complex readout: 1 channel/pixel

11 Event Tracking Sub-mm spatial resolution Differentiate between: alphas electrons muons gammas 55 μm pixels 14x14x0.3 mm 3 Si

12 Event Tracking Sub-mm spatial resolution Differentiate between: alphas electrons muons gammas [Bloxham, Freer. NIMA, 2006] No gammas, quenching/degradation Smeared at 2.3%

13 COBRA: The Experiment LABORATORI NAZIONALI GRAN SASSO 3500 M.W.E. REDUCES COSMIC RAYS AND NEUTRONS

14 COBRA: The Experiment First Prototype 2x2 1cm 3 detectors About 8 kg days at LNGS Current Generation 4x4 1cm 3 detectors About 18 kg days at LNGS Clean Cu PE [B] Pb Cu U,Th,K EMF n s γ s X-rays

15 Background Reduction Clean Plastic Delrin Wires Kapton foil Radon N2 flushing Crystal Passivation Dye-free paint, Parylene

16 Background Reduction Clean Plastic Delrin Wires Kapton foil Radon N2 flushing Crystal Passivation BACKGROUND FEWER THAN 5 COUNTS/KEV/KG/YR IN ROI Dye-free paint

17 Published Results 4-fold non-unique beta decay of 113 Cd (from 2x2 prototype) 10 independent measurements from 4x4 system: J.V. Dawson et al., Nucl. Phys. A 818, 264 (2009) Half-life: Q-value: ectral shape fits better with unique 3-fold forbidden than non-unique transition

18 Published Results Six limits above years from a total of 18 kg days of data based on 18 kg J.V. days Dawson of data, et al., arxiv:

19 Current R&D 64 CPG detectors at LNGS Liquid scintillator Growth of 116 Cd enriched CZT Pixel prototypes at LNGS Polaris (U-Mich), WUSTL, Timepix Large-scale experiment

20 Large-Scale Experiment 10-3 cts/(kev kg yr), 2.8 MeV 10-3 cts/(kev kg yr), ΔE=1% 5x10-4 cts/(kev kg yr), ΔE=1% 50 mev 420 kg CZT, 90% enriched in 116 Cd

21 Large-Scale Experiment Example: large-volume CZT, 0.5x3.9x3.9 cm 3 23,593 enriched detectors (90% 116 Cd) Total 420kg of 116 Cd 256 pixels per detector at 2.5mm pitch 6M total pixels 1W per detector, 32W per module Air cooling will be sufficient ( Air = N2) An 80-module unit/crate would have approximately 13mW/cm 3

22 11cm 65cm Cu cooling fins ASICs Cathode HV FPGA Anode bumps Data Out

23 50cm 60cm 65cm

24 10 full units >420kg 116 Cd

25 Summary COBRA is a CZT-based 0νββ search World best limits even with low masses J.V. Dawson et al., Phys. Rev. C 80 (2009) Pixelated CZT tested in low background Goal: ton-scale proposal in 2012/2013

26 THANK YOU! QUESTIONS?

27 BONUS SLIDES

28 Detector Technologies _ e e + e e Weighting Potential determines how charge is collected over the drift path Small pixel effect corrects for incomplete collection Small pixels (or thin strips) only see charge in last millimeter so depth dependence is negated

29 Alternatives Thick detectors with fine pitch 1.5x2.2x2.2 cm 3 74,140 detectors (compare: 23,593) 350µm pixels, 4096 per det. 304M total pixels Total power and powerdensity both higher Many tightly packed detectors 1.72W per detector Flat cross-strip detectors 0.5x3.9x3.9 cm 3 23,593 detectors mm-strips per anode+cathode 1.4M total strips (501B virtual pixels) uses existing ASIC technology 32-channel BNL ASIC Power is lowest (0.66W/ detectors), but a different mechanical design required