Low Background NAA: A powerful tool for Physics of Rare Experiments and Environmental Sciences

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1 UNIMIB - Dipartimento di Fisica G. Occhialini INFN Sezione di Milano Bicocca UNIPV- LENA UNIMIB-DISAT Low Background NAA: A powerful tool for Physics of Rare Experiments and Environmental Sciences Massimiliano CLEMENZA; Giovanni BACCOLO 4 th INCC - 14 September 2014 Massimiliano Clemenza 1

2 Overview Definition Low Background Neutron Activation Analysis Radioactive backround: Sample correlated and without sample Radioactive background reduction methods Low Background counting system in Milano Bicocca LBNAA Application Glaciology - Measurements on Lys and Antartica Ice core LBNAA Application - Physics of Rare Events Experiments: CUORE Th in Copper, Lead Conclusions 4 th INCC - 14 September 2014 Massimiliano Clemenza 2

3 Low Background Neutron Activation Analysis Instrumental Neutron Activation Analysis (INAA) is a common method of trace element analysis whose Sensitivity depends, as with almost all the analytical techniques used in the various fields of research, from: Signal to Noise ratio S/N S Neutrons Fluence, irradiation-waiting-measuring times, detector efficiency, sample mass, Neutron Capture Cross Section N interference from other trace elements (and in some case from minor and major elements!) in the sample, or by interference from environmental background radiation to the detection system The Low Background Neutron Activation Analysis (LBNAA) foresee to minimize all sources of noise that limit the sensitivity of the technique 4 th INCC - 14 September 2014 Massimiliano Clemenza e Giovanni Baccolo

4 Radiaoctive Background Radioactive Background Sample correlated Without Sample Activations of Trace, Minor (and in some cases or major elements Detector Radioactive Background: Cosmic Rays and 232 Th, 238 U, 40 K, Radon, 210 Pb.in shieldings, detector materials, and laboratory Main limitation in INAA Main limitation in low background gamma spectroscopy 4 th INCC - 14 September 2014 Massimiliano Clemenza e Giovanni Baccolo

5 Radioactive background rejection methods Active veto detector in different configuartions - coincidence ( cascade kev 208 Tl ( 232 Th) Co - anti-coincidence (usually with plastic scintillatosr for cosmic rays reduction and anti-compton system) venting the detector with air or N 2 radon-free in order to reduce 214 Bi, 212 Bi, 214 Pb 212 Pb, 208 Tl, 10 Pb Passive Shieldings with high Z, density materials Deep Underground Laboratory Detector Radio-pure materials selection In particular for LBRNAA: Radiochemical treatments in order to separate interference s from Radionuclides of interest. Materials selections of supports, Vial..etc 4 th INCC - 14 September 2014 Massimiliano Clemenza e Giovanni Baccolo

6 Low Background Neutron Activation counting systems in Milano Bicocca TRIGA MARK UNIPV 250 kw Irradiations Facilities: Central: (n cm 2 sec -1 ) Rabbit: (n cm 2 sec -1 ) Lazy Susan: (n cm 2 sec -1 ) HpGe LOW BACKGROUND WELL LARAMIB UNIMIB Close to 4 geometry efficiency 400 cm 3 active volume 15cm low 210 Pb content Lead 10cm OFHC copper 65% relative efficiency equivalent Absolute >95% Hole: 12mm 40 mm depth 4 th INCC - 14 September 2014 Massimiliano Clemenza e Giovanni Baccolo

7 Environmental Sciences: Measurements on Lys and Antartica Ice core Windblown mineral aerosol (dust) plays a key role in the climate system, and permits the quantitative estimation of direct and indirect effects of dust on climate and environment and on the global energy balance. Glaciers and ice sheets from polar areas are unique natural archives for atmospheric dust. Site selection Ice core drilling Sample preparation in clean cold rooms Paleoclimatic studies For further informations see G. Baccolo Poster

8 Environmental Sciences: Measurements on Lys and Antartica Ice core Extraction of Ice Cores Decontamination Filtering melted Ice Elemental Charaterizations of DUST depositated on filter 4 th INCC - 14 September 2014 Massimiliano Clemenza e Giovanni Baccolo

9 Environmental Sciences: Measurements on Lys and Antartica Ice core Colle del Lys 200 ppm of DUST Dust events (i.e.saharian events) 1-10 ppm of DUST Winter background ANTARTICA: 100 ppb main events - 1 ppb background!!!! Analytical Requests are extremely low!!!! femtograms For furher informations see G. Baccolo Poster 4 th INCC - 14 September 2014 Massimiliano Clemenza e Giovanni Baccolo

10 Environmental Sciences: Measurements on Lys and Antartica Ice core All the "background" sources must to be minimized Clean room Cleaning equipment MilliQ water and Hyper pure acids Extraction of filter from Irradiated vial Reduction of filter s intrinsic contaminations:: Material selection Cleaning treatments 4 th INCC - 14 September 2014 Massimiliano Clemenza e Giovanni Baccolo

11 Environmental Sciences: Measurements on Lys and Antartica Ice core PES - Polyethersulfone PVDF - Polyvinylidene fluoride PTFE - Polytetrafluoroethylene Materials selection LCR PTFE - Liquid Chromatography Reagent Polytetrafluoroethylene PC - Polycarbonate MilliQ water HNO 3 5% Selection of Cleaning treatments MilliQ water Stand-alone 4 th INCC - 14 September 2014 Massimiliano Clemenza e Giovanni Baccolo

12 Environmental Sciences: Measurements on Lys and Antartica Ice core counts counts counts 32 P t 1/2 = 14 days 1500 sec live time measurements spectrums

13 Environmental Sciences: Measurements on Lys and Antartica Ice core PE Vial Winter bkg DUST event 1500 sec live time measurements PTFE FILTER + water HNO 3 5% Characterized more than 30 different elements Blank For further informations see G. Baccolo Poster sec live time measurements spectrums

14 Physics of Rare Events: materials selection Rare Events are phenomena characterized by: Low counting rate Waek signal compared to radioactive background Decreasing spourious counts Rare Events Physics and applications: CUORE EXPERIMENT Double beta decay (0 ) (neutrino mass) Solar (oscillations) Dark Matter (observation) Environmental radioactivity (low contaminations) Radiometric Dating methods 2 Now in construction at LNGS

15 Physics of Rare Events In experiments on Rare Events Physics: double beta decay search solar neutrinos non baryonic dark matter research Very pure materials are needed to minimize Experimental Radioactive Background counts Gamma region kev Future Double Beta Decay Experiments in the Region Of Interest require Radioactive background: <0,01 count/(kev kg year) 4 th INCC - 14 September 2014 Massimiliano Clemenza e Giovanni Baccolo

16 Physics of Rare Events Environmental gamma radiation Surrounding materials Primordial Nuclei and their radioactive chains: 232 Th, 238 U, 235 U, 40 K 208 Tl 214 Bi Radioactivity present in the experimental apparatus Alluminum (238U), Glass ( 238 U, 232 Th, 40 K), Copper (OFHC), Plastic materials, Electronics, Internal and surface contamination of the Detector: Shielding Materials Lead: 210 Pb, 210 Bi, 210 Po Copper: 232 Th, 238 U, 210 Po. Experimental Radioactive Background Cosmic Rays Muons: hard component Electrons, Gamma: soft component Radon and his progeny 220 Rn, 222 Rn Daughters gamma emitters : 214 Pb e 214 Bi 4 th INCC - 14 September 2014 Massimiliano Clemenza e Giovanni Baccolo

17 Physics of Rare Events Experimental Radioactive Background External Environmental gamma radioactivity Cosmic Rays Internal Radio contamination of materials used for experimental set up (copper) Heavy Shieldings Materials with High Z and density (Lead and Copper) Underground Laboratories 1400 m of rock shield (3500 m water equivalent ) [cosmic ray reduced~ 10 6 ] It is necessary to select radio purity materials

18 Low Level counting techniques for bulk measurements Underground facilities may shields experiments from the background induced by cosmic radiation, but isolating the physics process from radioactive background due to the experimental apparatus itself, remains one of the crucial challenge. What is considered Low Contamination? For future 0 decay experiments we consider for some materials: 232 Th < g/g (< 3 ubq/kg) 238 U < g/g (< 12 ubq/kg) Bulk measurements: rays spectrometry with Ultra low bkg HPGe HR-ICP-MS (High Resolution Inductive Coupled Plasma Mass Spectroscopy) RNAA (Radiochemical Neutron Activation Analysis)... 4 th INCC - 14 September 2014 Massimiliano Clemenza 18

19 Low Background Neutron Activation Measurement Analytical requests: 232 Th in High Purity Copper e Lead g/g for copper e g/g for lead Pb Portovesme NOSV Copper OFHC Copper Pb Cometa Pb Romano I (very rare ancient Pb with virtually zero 210 Pb content ) Pb Romano II (very rare ancient Pb with virtually zero 210 Pb content ) Old Limits 5x10-11 g/g for all lead types 4 th INCC - 14 September 2014 Massimiliano Clemenza 19

20 Low Background Neutron Activation Measurement Activation of the Copper 22,6 m 27 d 64 Cu t 1/ h 66 Cu t 1/2 5.1 m Activation of the trace elements in the Copper 75 Se t 1/2 120 d 192 Ir t 1/2 74d Separation of the activated element with Ion Exchange Resins CHELEX100 for Copper and Actinide for concentrate 233 Pa 198 Au t 1/2 2,7d 124 Sb t 1/2 60d 110m Ag t 1/2 250d 60 Co t 1/2 1925d 4 th INCC - 14 September 2014 Massimiliano Clemenza 20

21 Low Background Neutron Activation Measurement Cu + HNO 3 Cu + HNO 3 + STD 233 Pa CHELEX100 CHELEX100 Elution Elution ACTINIDE ACTINIDE 4 th INCC - 14 September 2014 Massimiliano Clemenza 21

22 Low Background Neutron Activation Measurement Pb+ HNO 3 Pb + HNO 3 + STD 233 Pa Elution Elution ACTINIDE ACTINIDE 4 th INCC - 14 September 2014 Massimiliano Clemenza 22

23 Low Background Neutron Activation Measurement Results: Limit < 2x10-12 for both NOSV and OFHC Copper Pb Portovesme: Pb Cometa: Pb Romano I: Pb Romano II: (1,3 ±0,2) x10-11 g/g (2,9 ±0,3) x10-11 g/g <8,2 x10-12 g/g 95% cl <8,5 x10-12 g/g 95% cl Pb Portovesme for external shieldings Pb Romano for internal shieldings 4 th INCC - 14 September 2014 Massimiliano Clemenza 23

24 Low Background Neutron Activation Measurement Thank you for the attention 4 th INCC - 14 September 2014 Massimiliano Clemenza e Giovanni Baccolo

25 Low Background Neutron Activation Measurement 4 th INCC - 14 September 2014 Massimiliano Clemenza e Giovanni Baccolo