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; E ore 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: monochroma c line in the energy spectrum at the energy value
smeared by detector resolu on!
19-24 June 2017 A. Branca - WIN2017 @ UCI 2 Double beta decay (DBD) II CUORE Effec ve 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 m (T1/2) = G (Q, Z) M |h 2 i| | | me
Phase space 5 Nuclear Matrix Element factor ~Q ßß (theore cal 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 viola on (ΔL = 2): a possible source 2 of ma er-an ma er 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 me 0 sens. M ⋅t (also “live me”) T ν ∝i.a.⋅ε ⋅ ( 1/2 ) ΔE ⋅ B Background Detector efficiency Energy resolu on In order to build a high sensi vity 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 resolu on; • 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
Radia on: (E) NTD Ge thermistor: energy deposit 3200 E resis ve thermometer 3000 ΔT = 2800 C(T)
Amplitude [mV] Bolometer: detector and source 2600 readout of 0ν DBD. High efficiency and ΔT 3 2400 ⎛ T ⎞ resolu on; 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 radioac vity from outside the detector:
• cosmic ray muons induced background; • neutron and gamma fluxes; b. natural radioac vity from the detector itself: • long-lived nuclei (40K, 238U, 232Th); • anthropogenic radioac ve isotopes (60Co, 137Cs, 134Cs); • cosmogenical radioac ve isotopes (60Co); c. mechanical vibra on 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); Radioac ve background reduc on:
• minimiza on 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 Resolu on: 5.1 ± 0.3 keV FWHM @ 2615 keV; Resolu on 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 contribu on 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 resolu on without noise op miza on.
19-24 June 2017 A. Branca - WIN2017 @ UCI 16 CUORE Installation CUORE
Towers installa on completed 10 mK Cu shield closed
Lead shield installed
Aug 2016 Cryostat closed Cables rou ng
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 op miza on • 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. Branca - WIN2017 @ UCI 18 CUORE status CUORE Noise op miza on:
• electronic noise a enua on; • reduc on of mechanical vibra on; • tuning of the pulse tube rela ve phase shi ing; Temperature scan:
• scan around the base temperature (Tbase) to choose the value op mizing the signal Preliminary and to set the design thermistors’ value of the resistance;
Working point measurement: “Neutron Transmuta on Doped” (NTD) • current bias (IB) scan to choose the value maximizing the SNR for each thermistor Germanium thermistors to read-out the at the given T ; crystals base Commissioning of the analysis so ware; T0 Tbase Vth Rth = R0e = CUORE started taking data on April 2017 IB
19-24 June 2017 A. Branca - WIN2017 @ UCI 19 Projected exclusion sensitivity CUORE
• Bayesian fit on toy MC background spectra; Preliminary • exclusion sensi vity obtained from the distribu on of the 90% C.I. limits 0ν on T 1/2 for the toy MC experiments for each fixed live me; • values of the BI projec on for CUORE and energy resolu on from CUORE-0 have been considered as input for the computa on;
RESULTS:
ü expected to reach CUORE-0 + Cuoricino sensi vity in few days; 0ν 25 ü expected exclusion sensi vity of T 1/2~ 9×10 yr (90% C.I.) in 5 years of live me;
19-24 June 2017 A. Branca - WIN2017 @ UCI 20 Conclusion CUORE
• November 2016: installa on completed; • Dec 2016 – Jan 2017: successful cooldown of the detector; • 27 Jan 2017: first CUORE pulse; • Feb – Apr 2017: commissioning of the detecor; • April 2017: CUORE started taking data;
Thank you for your a en on!
19-24 June 2017 A. Branca - WIN2017 @ UCI 21 Additional material CUORE
19-24 June 2017 A. Branca - WIN2017 @ UCI 22 List of useful papers CUORE
CUORE Collabora on results in this presenta on:
• Produc on of high purity TeO2 single crystals for the study of neutrinoless double beta decay, J. Cryst. Growth 312 (2010) 2999-3008; • Valida on of techniques to mi gate copper surface contamina on in CUORE, Astropart. Phys. 45 (2013) 13-22; • Search for Neutrinoless Double-Beta Decay of Te-130 with CUORE-0, Phys. Rev. Le . 115, 102502 (2015); • Analysis Techniques for the Evalua on of the Neutrinoless Double-β Decay Life me in Te-130 with CUORE-0, Phys. Rev. C 93, 045503 (2016); • The projected background for the CUORE experiment, arXiv:1704.08970; • CUORE Sensi vity to 0νββ Decay, arxiv:1705.10816;
19-24 June 2017 A. Branca - WIN2017 @ UCI 23 Projected discovery sensitivity CUORE
• Bayesian fit on toy MC background spectra; • discovery sensi vity obtained from 0ν T 1/2 for which the posterior probability Preliminary of the background only hypothesis given the data is smaller than 0.0027 (i.e. 3σ) in 50% of the experiments; • values of the BI projec on for CUORE and energy resolu on from CUORE-0 have been considered as input for the computa on. Also a worse scenario, with 10 keV FWHM, has been considered; RESULTS @ 5 keV FWHM:
ü expected to have a discovery sensi vity greater than CUORE-0 + Cuoricino limit in less than one month; 0ν 25 ü expected discovery sensi vity of T 1/2~ 4×10 yr (3σ) in 5 years of live me; 19-24 June 2017 A. Branca - WIN2017 @ UCI 24 Detector Calibration System CUORE
• Bolometers require independent in situ energy calibration; • For CUORE, we use: • 232Th γ-ray sources every ~month (239 keV to 2615 keV); Source string • Constant-energy pulsers to measure detector stability and location before calibration correct for variations in detector gain; (Motion Box) • Sources are outside cryostat during physics data-taking and lowered into cryostat and cooled to 10 mK for calibration; 300 K • Sources are put on strings and are lowered under their own Stainless steel weight; 40 K bellows • A series of tubes in the cryostat guides the strings; 4 K 4 K Thermalizer 600 mK 50 mK Inner guide tube route 10 mK Kevlar string Outer guide Thoriated tungsten (calibration source) Lead shielding tube route Copper capsule Detector region PTFE heat guide tube shrink tubing 8 mm ~9.2 mm 59 mm
Detector towers 6 mm
19-24 June 2017 A. Branca - WIN2017 @ UCI 25 mββ sensitivity and limits CUORE
3 3 10 10 Mo [meV]
β CUORE-0 + Cuoricino limit (Te)
Assuming: β
m Ge
• BI = 0.01 counts/(keV•kg•yr); 2 2 10 10 CUORE sensitivity (Te) Xe • energy resolu on of 5 keV FWHM; Inverted hierarchy • 5 years live me;
10 10
CUORE expected sensi vity to mββ is:
Normal hierarchy m 50 130 meV ββ < − 1 1
Other isotopes −1 − 1 10 10 10−1 1 10 1002 0.2 0.4 0.6 0.8 1 mlightest [meV]
19-24 June 2017 A. Branca - WIN2017 @ UCI 26 130 Te for 0ν DBD CUORE
• good Q-value (2528 keV) in low β/γ region; • high natural abundance (34.17%);
4500 48 Ca 4000
96 3500 Zr 150Nd 100 82Se Mo 3000 116 Cd 130 136Xe Te 2500 124Sn 76Ge 2000 Q-value [keV] 1500
1000 128Te
0 5 10 15 20 25 30 35 Isotopic Abundance [atomic %]
19-24 June 2017 A. Branca - WIN2017 @ UCI 27 Roman Lead CUORE
• Ancient Roman lead bricks for low-activity shielding;
• Recovered in late ‘80s from shipwreck off Sardinian coast;
• Obtained through agreement between INFN and Italian historical society;
• 270 bricks, 33 kg each = 7 tons (after inscriptions removed);
19-24 June 2017 A. Branca - WIN2017 @ UCI 28