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Double beta decay study at LNGS (the experiment LUCIFER)

Lucifer. made in the frame of LUCIFER experiment FP7/2007-2013 ERC grant agreement n. 247115. XXIV SEMINARIO NAZIONALE di FISICA NUCLEARE E SUBNUCLEARE OTRANTO, Serra degli Alimini, 21-27 Settembre 2012 Argomento : Studio del decadimento doppio beta ai LNGS

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Double beta decay study at LNGS (the experiment LUCIFER)

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  1. Lucifer made in the frame of LUCIFER experiment FP7/2007-2013 ERC grant agreement n. 247115. XXIV SEMINARIO NAZIONALE di FISICA NUCLEARE E SUBNUCLEARE OTRANTO, Serra degli Alimini, 21-27 Settembre 2012 Argomento: Studio del decadimento doppio beta ai LNGS Lezione 2: Esperimento LUCIFER Double beta decay study at LNGS(the experiment LUCIFER) I. Dafinei Università "La Sapienza" di Roma and Sezione INFN - Roma

  2. scintillating bolometers LUCIFER experiment large scale crystal production issue Outline

  3. Original idea Milano group mid 1990’s CaF2 scintillating bolometer beta alpha scintillating bolometers scintillating bolometers, why? • device able to measure both phonon (heat) excitation and the photon (scintillation) excitation generated in a crystal by a nuclear event • for a given energy deposit, the amount of emitted light is different for α wrt β/γ • scatter plot light vs. heat separates α from β/γ • The experimental basis for LUCIFER is the R&D activity lead by Stefano Pirroat LNGS , • in the framework of the programs: • BOLUX, funded by INFN – CSN5 • ILIAS-IDEA funded by the EC (WP2-P2)

  4. scintillating bolometers scintillating bolometers, how? (contains the 0νDBD candidate) • material purity • radioactive contamination (<ppt) • chemical purity (<ppm) • fabrication constraints • crystal growth, mechanical processing • package and transport

  5. Ge (Ø = 35 mm) FWHM=250 eV scintillating bolometers light detector (LD) performances LD: Ge disks (0.3 to 1 mm thickness) performances of a LD usually evaluated through the Energy resolution on the 55Fe doublet (5.9 & 6.5 keV X-Ray) S. Pirro et al., "Development of bolometric light detectors for double beta decay searches", NIM A 559 (2006) 361–363

  6. Light detector heater thermistor reflecting cavity scintillating bolometers first scintillating bolometer (March 2004) made of a 1 cm3 PbMoO4 crystal glued on a copper frame and facing a 36 mm diam Ge Crystal, acting a Light Detector

  7. scintillating bolometers first scintillating bolometer S. Pirro – Cryoscint conference - Oxford, 7 Dec 2004 even if on a small sample this was the first proof of alpha discrimination on a Mo based compound

  8. Background-Free area 2615 keV 208Tl  scintillating bolometers more on background measurement 3x3x6 cm3, 420 g CdWO4 Optical Materials 31 (2009) 1388 44 days background The MC simulation predicts a background level of 10-4 c/keV/kg/y in the region of interest

  9. excellent discrimination β/ CdWO4  first exhaustive explanation of the anticorrelation (bent lines) between heat and light release in a scintillating bolometer scintillating bolometers more on discrimination power C. Arnaboldi et al., "CdWO4 scintillating bolometer for Double Beta Decay: Light and heat anticorrelation, light yield and quenching factors ", Astroparticle Physics, 34 (2010), pp. 143-150

  10. LUCIFER experiment LUCIFER Low-background Underground Cryogenics Installation For Elusive Rates Principal Investigator:Fernando Ferroni ERC-2009-AdG 247115 2012 2013 2014 2015 isotope: 82Se , 100Mo , 116Cd R&D on light detectors material: ZnSe, ZnMoO4 , CdWO4 Thermistor production Natural crystal (growth) R&D technique: scintillating bolmeter 15 kg 82Se production Enriched crystal growth Detector assembling demonstrator LUCIFER timeline

  11. LUCIFER experiment LUCIFER in a glance • array of 36÷44 enriched (95%) Zn82Se crystals • total 82Se nuclei: (7.1÷8.9) 1025 • expected background in the ROI (2995 keV): (3÷6)10-3 c/keV/kg/y • energy resolution of the single detector expected: 10 keV FWHM • location: CUORICINO (now CUORE-0) cryostat (till 2015) Bolometric Light Detector Ge crystal Zn82Se crystal (Ø=45mm, h= 55 mm) W=483 g Reflecting Foil PTFE supports

  12. LUCIFER experiment LUCIFER hints The -induced background is recognized through two independent measurements: 1) the decay time of the scintillating signal 2) the different scintillation yield between  and / particles (the “usual” light Vs Heat scatter plot) ZnSe crystals shows an “inverse” QF, i.e. -particles scintillate more than /’s (Astrop. Phys.34 (2011) 344-353 ) Internal contaminations Internal contaminations 1) Decay time of the scintillation light 2) Light Vs Heat scatter Plot / scintillation “Ionization coincidences” between Ge light detector and ZnSe Smeared -source -scintilaltion 208Tl calibration source Directionization 12.5 days measurement

  13. radio-clean! LUCIFER experiment LUCIFER hints alpha discrimination > 20 sigma ! without light detection ZnMoO4 J.W. Beeman et al., "ZnMoO4: A promising bolometer for neutrinoless double beta …", Astroparticle Physics 35 (2012) 813–820

  14. -Discrimination without light detection at 14 sigma  β/ Shape thermal pulse LUCIFER experiment LUCIFER hints arXiv:1207.0433v11 Energy resolution compatible with CUORE detectors ZnMoO4 Radiopurity already at top level, no evidence of 232Th contamination <1.4x10-12 g/g

  15. LUCIFER experiment LUCIFER hints cryogenic “force” Two above–ground (Milano Bicocca) + THREE deep underground (LNGS) Hall C cryostat New Cryostat for Scintillating Bolometer (Oct 2012) Cuore-0/Lucifer cryostat

  16. Measurement of concentration of specific nuclei (238U 232Th) LUCIFER experiment LUCIFER hints radio-purity check 1) High Purity GErmanium – HPGE (,) LNGS Direct measurement of radioactivity. The most sensitive HPGE worldwide 2) Surface Barrier Detectors – SBD () LNGS/MIB 3) Neutron Activation Analysis – NAA PAVIA LENA/MiB 4) Inductive Coupled Plasma Mass Spectroscopy - ICPMS 2 ICPMS – HR (10-14 g/g) LNGS + MIB For DBD scintillating bolometers ICPMS –HR (10-12 g/g) LNGS

  17. ~1ton TeO2 large scale crystal production issue

  18. ~80tons PbWO4 ~1ton TeO2 Compact Muon Solenoid large scale crystal production issue

  19. Rare Events Physics (REP) High Energy Physics (HEP) • extremely high sensitivity • very low background EM calorimetry radiation length Molière radius effectiveness & emission spectrum PM spectral sensitivity Zeff main technological constraints m Tt Light Yield (LY) crystal perfection n response time Radiaton hardness radio-purity afterglow r Hardness (Moh) hygroscopic large scale crystal production issue bigger challenge: quantity (in HEP) is exceeded by difficulty (in REP)

  20. large scale crystal production issue CUORE case precautionary principle: raw materials, reagents, intermediary products, processes and procedures only 2-3% crystals can be measured dedicated crystal growth facility @ SICCAS Jiading dedicated TeO2 synthesis facility @ Kunshan Chemical Plant dedicated clean room SICCAS/INFN @ Jiading dedicated measurement protocols -dimensions -crystal perfection -radio-purity dedicated production protocols -environment conditions -equipment and infrastructures -materials handling

  21. large scale crystal production issue • question: • is it feasible a similar enterprise in the case of scintillating bolometers? • answer: • TeO2 crystal was a lucky case: • industrial scale production already existed • easy implementation of improvements imposed by DBD application • long term existing market for high quality crystals • scintillating crystals for DBD is a more complex case: • no scintillating material for DBD use was produced at large scale till now • some of the problems to be addressed were solved in the case of TeO2 crystal production • work still needed for a reliable production

  22. large scale crystal production issue

  23. large scale crystal production issue 8 URENCO, Stable Isotopes Division enriched Se elemental SeF6 conversion to Se through a dedicated procedure to meet DBD application requirements 10-10 instead of <10-12 preferred! ZnSe synthesis and crystal growth may work as purifiers

  24. large scale crystal production issue recovery and recycling ZnSe crystal growth mechanical processing ZnSe crystal growth SmiLab (ISMA Kharkov expertise) ZnSe samples for cryogenic test • different thermal treatment during crystal growth • chosen from a set of 11 • cryogenic test to fix the best growth conditions for maximal light output and bolometric performance

  25. large scale crystal production issue ZnSe crystal growth we are on the right track !

  26. acknowledgements this work was made in the frame of LUCIFER experiment funded by the European Research Council under the European Unions Seventh Framework Programme FP7/2007-2013 / ERC grant agreement n. 247115.

  27. recommended bibliography (.pdf files available upon request) • N. Nosengo, "Lead from ancient shipwreck will line Italian neutrino experiment",Nature (News) 15 April2010, http://www.nature.com/news/2010/100415/full/news.2010.186.html • A. Alessandrello et al., "Measurement of radioactivity of ancient roman lead ...", NIM B61 (1991) 106-117 • C. Arpesella, "A Low Background Counting Facility at Laboratori Nazionali del Gran Sasso ", Appl. Radiat. Isot. Vol.47, No.9/10, pp. 991-996 (1996) • P.Belli et al., "Deep underground Neutron Flux Measurement with Large BF3 Counters", Il Nuovo Cimento vol. 101 A, no. 6, Giugno 1989 • Ahlen S. P. et al., “Study of penetrating cosmic ray muons and search for large scale anisotropics at the Gran Sasso Laboratory”, Phys. Lett. B, Vol. 249, no.1 (1990), pp.149-156 • L. Cardani et al., “Performance of a large TeO2 crystal … “, JINST 7 P01020 (2012) • S. Pirro et al., "Development of bolometric light detectors for double beta decay searches", NIM A 559 (2006) 361–363 • L. Gironi etal., "CdWO4 bolometers for double beta decay search", Optical Materials, Vol. 31, Issue 10, Aug. 2009, pp. 1388-1392 • C. Arnaboldi et al., "CdWO4 scintillating bolometer for Double Beta Decay: Light and heat anticorrelation, light yield and quenching factors ", Astroparticle Physics, Volume 34, Issue 3, October 2010, Pages 143-150 • J.W. Beeman et al., "ZnMoO4: A promising bolometer for neutrinoless double beta …", Astroparticle Physics 35 (2012) 813–820

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