The start up of the CUORE experiment at LNGS CUORE Photo credit: Yury Suvorov Antonio Branca @ INFN Padova On behalf of the CUORE Collaboration WIN2017 @ UC Irvine – 19-24 June 2017 Double beta decay (DBD) CUORE 2ν DBD: (A, Z) → (A, Z + 2)+ 2e− + 2ν 0ν DBD: (A, Z) → (A, Z + 2)+ 2e− - proposed in 1935 by - proposed in 1937 by Maria Goeppert-Mayer; Eore Majorana; - 2nd order process allowed - requires pHysics beyond in the Standard Model; Standard Model; τ ~ 1019−21 yr τ >1024−25 yr Energy spectrum of the two electrons in DBD 0ν DBD Signature: monocHromac line in the energy spectrum at the energy value smeared by detector resoluOon! 19-24 June 2017 A. Branca - WIN2017 @ UCI 2 Double beta decay (DBD) II CUORE EffecOve Majorana mass m = f (Δm , Δm , m ,α ,α ,δ) THe 0ν DBD Half-life: ββ 1,2 2,3 1 1 2 2 0⌫ 1 0⌫ 0⌫ 2 mββ (T1/2)− = G (Q, Z) M |h 2 i| | | me PHase space 5 Nuclear Matrix Element factor ~Q ßß (theoreOcal uncertainty ~2-3) (accurately calculable) ISM | 9 IBM ν 0 QRPA-T |M 8 QRPA-J Physics consequences if 0ν DBD is observed: PHFB GCM 7 6 • proof of the Majorana nature of neutrino; 5 • constrain on the neutrino mass HierarcHy and scale; 4 3 • lepton number violaon (ΔL = 2): a possible source 2 of maer-anOmaer asymmetry in the universe; 1 0 48Ca 76Ge 82Se 96Zr 100Mo 116Cd 124Sn 128Te 130Te 130Xe 150Nd 19-24 June 2017 A. Branca - WIN2017 @ UCI 3 Sensitivity CUORE Half-life corresponding to the minimum number of detectable signal events above background at a given C.L. Isotopic abundance Detector mass Measuring Ome 0 sens. M ⋅t (also “live Ome”) T ν ∝i.a.⋅ε ⋅ ( 1/2 ) ΔE ⋅ B Background Detector efficiency Energy resoluon In order to build a HigH sensiOvity experiment: • select 0v DBD candidates with HigH natural isotopic abundance or enricHed; • HigH detector mass; • good detector stability over a long period; • extremely HigH energy resoluOon; • extremely low background environment; 19-24 June 2017 A. Branca - WIN2017 @ UCI 4 Bolometric technique in CUORE CUORE (A) Copper frame: A 10 mK Heat sink (B) PTFE holders: D weak thermal coupling (D) Si joule heater: C reference pulses (C) TeO2 crystal: E B energy absorber RadiaEon: (E) NTD Ge thermistor: energy deposit 3200 E resisOve thermometer 3000 ΔT = 2800 C(T) Amplitude [mV] Bolometer: detector and source 2600 readout of 0ν DBD. HigH efficiency and ΔT 3 2400 ⎛ T ⎞ resoluOon; C(T) = ⎜ ⎟ 2200 ⎝ϑ D ⎠ 2000 Low temperature needed: 1800 J mK @T =10mK ⇒ C ~ 10−9 ; ΔT = 0.1 ; τ ~ 1s; 1600 0 0.5 1 1.5 2 2.5 3 3.5 4 K MeV Time [s] 19-24 June 2017 A. Branca - WIN2017 @ UCI 5 A rare event search CUORE 24−25 SearcHing for a rare event (0ν DBD): ………………………τ >10 yr Extremely important to reduce as mucH as possible backgrounds: a. natural radioacOvity from outside the detector: • cosmic ray muons induced background; • neutron and gamma fluxes; b. natural radioacOvity from the detector itself: • long-lived nuclei (40K, 238U, 232Th); • anthropogenic radioacOve isotopes (60Co, 137Cs, 134Cs); • cosmogenical radioacOve isotopes (60Co); c. mecHanical vibraon noise: • cryogenic system and seismic noise; 19-24 June 2017 A. Branca - WIN2017 @ UCI 6 CUORE installed @ LNGS CUORE CUORE @ Hall A • average depth: ~3600 m.w.e. • muon flux: ~3×10-8 μ/(s cm2) • neutron flux: < 4×10-6 n/(s cm2) • gamma flux: ~0.73 γ/(s cm2) 19-24 June 2017 A. Branca - WIN2017 @ UCI 7 Suspension System CUORE Abatement of vibrations: detector mechanical Y-Beam decoupling from the outside environment: • detector hung by the Y-Beam through Minus-K cables made of stainless steel tie bars, Kevlar ropes and copper bars (damping the MSP horizontal oscillations); • 3 minus-K springs connect the Y-Beam to the Main Support Plate, MSP (attenuating the noise of ~35 dB); Lead sHield • elastometers at the structure basis (seismic H3BO3 isolators); panels Radioactive background reduction: Polyethylene • outer neutron shield: polyethylene + borated powder; • outer gamma shield: lead shield; Elastometers 19-24 June 2017 A. Branca - WIN2017 @ UCI 8 Cryogenic System CUORE Specifics: • Fast Cooling System: T down to ~40 K; • 5 Pulse Tubes cryocooler: T down to ~4 K; • Dilution Refrigerator: T operations 10 mK; • Nominal cooling power: 3 µW @ 10 mK; • Cryogen-free cryostat: high duty cycle; Cool down ~15 tons @ T < 4 K and ~1.5 tons @ T = 10 mK in a few weeks. Radioactive background reduction: • material screening and accurate selection to ensure radiopurity; • lead shielding (Roman and modern Pb); 19-24 June 2017 A. Branca - WIN2017 @ UCI 9 The CUORE “core” CUORE 988 TeO2 crystals arranged in 19 towers (13 floors - 52 crystals eacH): • 130Te for 0v DBD: good Q-value (2528 keV) in low β/γ region, higH natural abundance (34.17%); • total TeO2 mass of 742 kg (206 kg of 130Te); RadioacOve background reducOon: • minimizaon of material/ surface facing the crystals; • developed a stringent protocol for the tower assembly and All 19 towers installed material cleaning (tested on between July-August 2016 predecessor CUORE-0); A single CUORE tower 19-24 June 2017 A. Branca - WIN2017 @ UCI 10 CUORE0: the first CUORE tower CUORE First detector tower built using the new tecHniques and assembly line developed for CUORE: • operated from 2013 to 2015 in old Cuoricino cryostat; • proof of concept for CUORE; • 0ν DBD searcH by itself; ) 6 ) 4 σ σ 4 2 2 0 0 –2 −2 −4 Residual ( Residual –4 Residual ( −6 18 2560 2570 2580 2590 2600 2610 2620 2630 2640 2650 0.25 208 2 Summed calibration data Tl γ 16 χ /NDF = 43.9/46 4 Projected fit 14 0.2 10 12 0.15 3 Te X-ray 10 10 escapes 8 0.1 102 Events / (2 keV) Events 6 4 0.05 2 10 Counts / (0.5 keV) Event RAte (counts/(keV kg yr)) (counts/(keV RAte Event 0 0 2470 2480 2490 2500 2510 2520 2530 2540 2550 2560 2570 1 Reconstructed Energy (keV) 2560 2570 2580 2590 2600 2610 2620 2630 2640 2650 RESULTS: Reconstructed Energy (keV) 24 Ø 0νββ upper limit: T1/2(0ν) > 4×10 yr (@ 90% C.L.) combined CUORE0 + Cuoricino results; ü ROI background: 0.058 ± 0.004 c/(keVkgyr); ü ResoluOon: 5.1 ± 0.3 keV FWHM @ 2615 keV; ResoluOon consistent with the CUORE goal of 5 keV. 19-24 June 2017 A. Branca - WIN2017 @ UCI 11 Material cleaning and assembling CUORE Production of the TeO2 crystals: • by Shanghai Institute of Ceramics, Chinese Academy of Science (SICCAS); • two successive crystal growths starting from high purity synthetized TeO2 powder; • cutting, orienting and shaping from raw ingots and surface polishing and packaging; • all operations performed in a dedicated clean room and following strict controls to limit radioactive contamination; Cleaning of copper surfaces (tower parts and 10 mK cryostat shield): • new cleaning techniques developed at LNL; • tumbling, electropolishing, chemical etching, magnetron plasma aimed at the removal of a thin layer of material (from 1 µm to 100 µm); 19-24 June 2017 A. Branca - WIN2017 @ UCI 12 Material cleaning and assembling CUORE Strict protocol adopted for each step of the CUORE towers construction: all in N2 atmosphere and within glove boxes to avoid radioactive recontamination; 1. sensors gluing 2. tower assembly 3. wire bonding 4. tower storage 19-24 June 2017 A. Branca - WIN2017 @ UCI 13 Background reduction effectiveness CUORE β/γ dominated α dominated 208Tl 210Po 190Pt 234U/226Ra/230Th 238 222Rn U 218Po Comparison of the background in Cuoricino and CUORE-0 238 232 Background indexes (counts/(keV•kg•yr)) • Material cleaning: U and Th α lines reduced (~ factor of 7); 0ν DBD region α region (2.47-2.58 MeV) (2.7-3.9 MeV) • Tower assembly in N2 atmospHere: 238U γ lines reduced (~ factor 2/3); Cuoricino 0.169 ± 0.006 0.110 ± 0.001 • Same Cuoricino cryostat: 232Th γ lines CUORE-0 0.058 ± 0.004 0.016 ± 0.001 not reduced; 19-24 June 2017 A. Branca - WIN2017 @ UCI 14 CUORE background projection CUORE Main background index in the 0ν DBD region expected for the various components of CUORE Measured in Preliminary CUORE-0 Material expected screening dominant contribuOon from the Cu of the towers structure LNGS Fluxes Projected total BI in the 0ν DBD region is consistent with CUORE background goal (10-2 counts/(keV•kg•yr)): counts BI = (1.02 ± 0.03(stat.)+0.23 (syst.))⋅10−2 (Preliminary) −0.10 kev⋅ kg⋅ yr 19-24 June 2017 A. Branca - WIN2017 @ UCI 15 Cryostat commissioning CUORE Commissioning completed in MarcH 2016: 300 K • stable base T = 6.3 mK over 70 days (no 40 K detector, full load); • full detector read-out cHain (electronics, DAQ) 4 K test, temperature stability with Mini-Tower (8 crystal tower); 600 mK 50 mK 10 mK Mini-Tower resoluOon without noise opOmizaon. 19-24 June 2017 A. Branca - WIN2017 @ UCI 16 CUORE Installation CUORE Towers installaon completed 10 mK Cu shield closed Lead sHield installed Aug 2016 Cryostat closed Cables rouOng Sep – Nov 2016 Nov 2016 19-24 June 2017 A. Branca - WIN2017 @ UCI 17 CUORE cooldown and commissioning CUORE • cooldown started on Dec 5, 2016; • lasted about 3.5 weeks (without taking A•er the cooldown into account tecHnical stops for system started a pHase of debugging); detector opOmizaon • on Jan 26, 2017 reached a base temperature of T = 7 mK; Diode thermometer at 10mK plate First pulse observed on Jan 27, 2017 cryogenics debugging 102 electronics debugging T (K) 10 12/05-12:16 12/22-14:10 01/08-16:04 01/25-17:59 Time 19-24 June 2017 A.