Excited State Search for Neutrinoless Double-­‐Beta Decay with CUORE Proposed CUORE excited-­‐state search for Neutrino less Double-­‐ Beta Decay of 130Te to the first excited 0+ State in 130Xe (with parHal enrichment ?) Frank Avignone, Jeff Wilson & Rick Creswick University of South Carolina nuMass MeeHng, Universita` Di Milano Biccocca, February 4-­‐7, Milano, Italy 2013 A coincidence Experiment: Decay to 1st Excited 0+ State in 130Xe at 1793.5-­‐keV •  Eventually this experiment could be with an Isotopically enriched inner core, or totally enriched in 130Te. •  The experiment would be performed first with the natural abundance CUORE (34.08% 130Te). •  A significant amount of socware development is required and much has already been done. •  Now that all of the CUORE U.S. crystals are produced, we are working with SICCAS on a cooperaHve R&D program to determine the technical feasibility and cost, of enriching the inner seven towers. Decay Scheme of the Double-­‐Beta Decay of 130Te gamma #1: 1257.41-­‐keV Gamma #2: 536.09-­‐keV; Q(1793.5, 0+)=2527.518-­‐1793.5=734.03-­‐keV Coincidence Scenarios Analyzed for CUORICINO Eff. #1= 0.44% Eff. #2 1.77% Eff. #3=1.09% T
(
Te,130Xe*) > 1.0 x 1024y (90%C.L.) ov1/2 130
Background acer N(130Te) x t =9.5 x 1025y A.  Expected peak at 1257.41-­‐keV B.  Expected peak at 1270.0-­‐keV C.  Expected peak at 1991.0-­‐keV R&D to Enrich the Inner Volume of CUORE There are 19 towers of 13 modules high and each module has 4 bolometers for a total of 988 bolometers. Inside there are 7 towers 11 modules high and 4 bolometers per module or 308 bolometers completely surrounded by other modules. Let us enrich these to >90% in 130Te. b a c d One of many possible configuraHons of a real event Obvious coincidence background event Analysis Procedures & Event SelecHon 1.  Select the sample of all coincidence events 2.  From this sample select only those with total deposited energy of 2527-­‐keV (add uncertainHes to all cuts). 3.  PlaHnum event: 734-­‐keV in one detector, 536-­‐keV in a near detector, and 1237-­‐keV in a second near detector 4.  Golden event: 734-­‐keV in one detector and 1793-­‐keV in several near detectors. 5.  Silver event: 1270-­‐keV in one detector, and 1257-­‐keV distributed in one or more near detectors. 6.  A Bronze event 1991-­‐keV in one detector and 536-­‐keV distributed in one or more near detectors. 7.  Etc., etc. The TheoreHcal EsHmaHon of the Half Life The nuclear matrix element was calculated by Jouni Suhonen using a quasi-­‐parHcle random-­‐phase (QRPA) approximaHon. Calculated SensiHvity to the EffecHve Majorana Mass of the Electron Neutrino T1/2 ~ 1027 y <mv> = 100-­‐mev Petr Vogel states that the raHo of phase spaces for 0+ ground state to first 0+ excited state excited state in 130Xe is G (0+)/G (0+)= 38 gs
ex
Proposed ParHal Enrichment of CUORE Seven internal towers of TeO2 enriched to >90% in 130Te. Seven towers, 11-­‐modules high; each module has 4-­‐
bolometers; each tower has 44-­‐bolometers. Accordingly, there are 308 enriched bolometers, 0.76-­‐kg each, or 234-­‐kg of TeO2 Containing 188-­‐kg of Te. At an enrichment of 93% 130Te, the total mass of 130Te in the inner enriched volume is 175-­‐kg. EsHmated Cost of the Enriched Bolometers The Cost of the 130Te used was the cost of the 10-­‐kg purchased in 2010 which was $17,000/kg of metal. Assume a 75% yield in detectors of input material to fabricate the array; 225-­‐kg will be needed cosHng $3,830,667. Recycling could lead to a factor of two for the crystal costs, or $10,000 per crystal for 308 crystals or $3,080,000. The esHmated total bolometer cost will be ~ $7,000,000. Add 30% conHngency; the cost will be ~ $9,100,000. Status of the Enriched Crystal Project with SICCAS • The R&D at SICCAS was postponed unHl all of the CUORE crystals were delivered. AcHon is started again. • ~500-­‐g of Te, enriched to 93% in 130Te metal was sent to SICCAS •  It was converted to TeO2 at Kunshan and sent back to SICCAS. • It is being blended with natTeO2 to form 5-­‐kg of TeO2 at 40% 130Te. • A crystal is being grown and samples cut to determine if the abundance is uniform. • Three 5x5x5 cm3 crystals will be grown, polished and sent to LNGS for tesHng. • If all goes well, the maximum number of 5x5x5 cm3 will be prepared and the yield and cost will be determined. Details of the Te Chemistry and PurificaHon Journal of Crystal Growth 312 (2010) 2999-­‐3008 Chemistry to convert Te Metal to TeO2 Te + HNO3 2Te + 9HNO3 Te2O3(OH)NO3 +8NO2 +4H2O Te2O3(OH)NO3 2TeO2 + HNO3 Wash TeO2 HNO3 : Nitric Acid, OH: Hydroxyl Group, NO3: Nitrate, NO2: Nitrite Chemical PurificaHon of the 130TeO2 TeO2 + HCl TeO2 + 4HCl TeCl4 + 2H2O [TeCl4 ] FILTER [TeCl4 ] TeCl4 + 4NH4OH Te(OH)4 + 4NH4Cl Te(OH)4 TeO2 +H2O WASH and DRY (TeO2 ) [TeO2 , 99.999%] NH4OH (Ammonium Hydroxide) NH4Cl (Ammonium Chloride) Crystal Growth and PurificaHon Steps [99.999% TeO2] [CalcinaHon] [1st crystal Growth] [Grind ~ 35% for Reprocess] [TeO2 + 4HCl [ TeCl4 + H2O ] [Filtering TeCl4 ] [TeCl4 + 4NH4OH Te(OH)4 + 4NH4Cl] [Te(OH)4 TeO2 + H2O] [TeO2 ] [Wash, Dry , Calcinate] [2nd Crystal Growth] AcHon Items to Needed for this Project 1.  NegoHate with SICCAS to do R&D to determine feasibility and yield in detector mass. (Done) 2. Obtain Funds from the NSF for the R&D etc. (Done) 3. Purchase 10-­‐kg of Te metal enriched to 93% in 130Te ( Done, the metal is at LBNL and has been measured for radioacHvity.) 4. Use CUORE Monte-­‐Carlo Code to model the various scenarios and determine the detecHon efficiencies for each. (ComputaHons of 1,2,3,&4 crystal events are complete) 5. Apply this code to the inner 308 bolometers of the normal abundance CUORE (in process). 6. Produce and test the enriched test detectors for background and bolometric performance (the steps towards the producHon of these bolometers has started). 7. Organize the results of these studies for publicaHon, and for wriHng a major proposal. Conclusions •  Neutrino less double-­‐beta decay of 130Te to the 1st excited 0+ state in 130Xe could have zero-­‐background. •  The raHo Ggs(0+)/Gex(0+)=38 (Petr Vogel) •  The nuclear matrix elements very uncertain. •  The coincidence efficiency thus far > 34%. •  Enrichment to 93% in 130Te is under invesHgaHon. •  This would be equivalent to reducing background by a factor of 7.45, of from .01 to 0.0013. •  ComputaHons of coincidence scenarios conHnue. •  A full invesHgaHon of the feasibility of enrichment is underway with the Shanghai InsHtute of Ceramics of the Chinese Academy of Science (SICCAS).