0νββ Searcheswith Low-Temperature
Thermal Calorimeters
Yong-Hamb Kim
Center for Underground Physics
Institute for Basic ScienceUGAP 2022Outline

1.

0νββ physics

2.

Low-Temperature Thermal Calorimeters

Yong-Hamb Kim

for 0νββ experiments
3.

The AMoRE project4.

R&D challenges for LT 0νββ searches

2UGAP 20220νββ and ν (brief intro.)

Yong-Hamb Kim• 0νββ decay can only happen if neutrinos are massive
Majoanana particles (own anti-particles).
 fundamental understanding of particle physics
 0νββ search is the only practical technique to answer.
• The 0νββ decay rate (T0ν) is closely related to the mass ofneutrinos.
 Most sensitive measurement method (if Majorana particle)• The 0νββ decay can only happen if Lepton number
conservation is violated.
 New physics beyond the standard model

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Yong-Hamb Kim

Double beta decay
35 0νββ nuclei are found.

• 2nd order weak process• ββ(2ν) decay is detectable if 1storder β decay is not allowed.

Nuclear masseven mass number
N, Z oddforbidden
ββ -ββ +N, Z evenZ−2Z−1Z

Z+1

Atomic number

Z+2

ββ-decay nuclei
with Q > 2 MeVQ(MeV)

Abund.
(%)

48Ca → 48Ti

4.271

0.187

76Ge → 76Se

2.040

7.8

82Se → 82Kr

2.995

9.2

96Zr → 96Ru

3.350

2.8

100Mo → 100Ru

3.034

9.7

110Pd → 110Cd

2.013

11.8

116Cd → 116Sn

2.802

7.5

124Sn → 124Ge

2.228

5.8

130Te → 130Xe

2.528

34.2

136Xe → 136Ba

2.479

8.9

150Nd → 150Sm

3.367

5.6
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Double beta decay w. & wo. ν emission

2ν mode• A conventional• 2nd order weak process in NP

Yong-Hamb Kim

0ν mode• A hypothetical process only ifmv≠0, v ꞊ v, |∆L| ꞊ 20νββ (ideal detection)2νββ0νββ signal characteristics- A peak at Q
- Two electrons from vertex(𝐸𝐸1 + 𝐸𝐸2)/𝑄𝑄

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Yong-Hamb Kim

Search for 0νββ

Double Beta Decay with two neutrinos

Double Beta Decay with no neutrino

𝐸𝐸tot/𝑄𝑄

0νββ discovery answers- Majorana (ν = ν ) particles not Dirac (ν ≠ ν )0ν2- Mass scale of neutrinos ( 1 T1/ 2 ∝ mν )- Lepton number violation
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Yong-Hamb Kim

0νββ decay rate0ν
1/ 2Γ0ν = 1 T

2

2= G0 v M 0 v mββ<standard process> G0ν : Phase space factor: Calculable
Atomic physics
 |M0ν| : Nuclear matrix element: Uncertain by 2~3 times,
Nuclear physics
 mββ : Effective neutrino mass: Interesting
Particle physics

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UGAP 20220νββ Experiments
Methods

Loaded Liquid Scintillators
Ge semiconductors
TPCs (liquid, gas)

Low-temperature thermal
calorimeters

Yong-Hamb Kim

Isotopes
130Te: SNO+, JUNO

136Xe: KamLAND-Zen
76Ge: GERDA, Majorana Demonstrator

LEGEND, CDEX

136Xe: EXO200, nEXO

NEXT
PandaX-III, R2D2

48Ca: CANDLES-LT R&D
82Se: CUPID-0

100Mo: AMoRE, CUPID-Mo, CUPID
130Te: CUORE

Tracking chambers

82Se: SuperNEMO

Inorganic scintillators

48Ca: CANDLES8UGAP 2022

Yong-Hamb Kim

Common strategies to increase sensitivity
0ν
1/ 2T

M ⋅ time∝bkg ⋅ ∆E<background case>T10/ ν2 ∝ M ⋅ time<background-free case> Increase M : Large detector mass, Enriched ββ elements  budget
 Increase ‘time’ : up to a few years
 Smaller ∆E : Better energy resolution  detector tech. LT thermal calorimeters
 Bkg. : Minimize background events in ROI
 Underground facility (w. controls on Rn, n, dust, long-lived cosmogenics)
 Radio-assay equipment and protocols- Controls on natural occurring radioactive materials (U, Th, etc. ) In-situ bkg. identification- Alphas, gammas, ββ(2ν), μ- and n- induced, ν-e scatterings
 PSD, Heat/L or Charge/L detection, Veto, Shield, Topology, ΔE, Δt
 Etc. LT thermal calorimeters
9LTDs for 0νββ search
Sensors & Detection Technologies

UGAP 2022

Yong-Hamb Kim

Low Temperature Thermal Calorimeters“Calorimetric measurement of heat signals at mK temperatures”

Energy absorption  Temperature
Thermometer

Thermal link

AbsorberHeat sink < 100 mK

Choice of thermometers for 0νββ searches•••••

Thermistors (NTD Ge) CUORE, CUPID
MMC (Metallic Magnetic Calorimeter) AMoRE CANDLES-LT
TES (Transition Edge Sensor) Light detector
KID (Kinetic Inductance Device) CALDER
etc.
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Yong-Hamb Kim

Thermistors•••••

Doped semiconductors- Neutron transmuted doped (NTD) Ge thermistors- Ion implantation doped Si thermistors
R(T) : 1 MΩ ∼100 MΩ
Readout: (cold) JFETHigh resolution + High linearity + Wide dynamic range +Absorber friendly
Require very low bias current(sensitive to micro-phonics andelectromagnetic interference), Slow response

2.1 kg
TeO2<Current bias and read voltage >fig. from Cardani et al arXiv.1106.0568
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UGAP 2022••••

Yong-Hamb Kim

Metallic Magnetic Calorimeter (MMC)
Paramagnetic alloy in a magnetic fieldAu:Er(300-1000 ppm), Ag:Er(300-1000 ppm)
 Magnetization variation with temperature
Readout: SQUIDHigh resolution + High linearity + Wide dynamic range +Absorber friendly + No bias heating + Relatively fast + MUXMore wires & materials needed for SQUIDs and MMCs

fig. from SY Oh et al SuST 2017targetcrystal

MMC

Phonon collector
gold wires
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•

••
•
•

Transition Edge Sensor (TES)

Yong-Hamb Kim

Superconducting strip at Tc- Elemental superconductors: Ti, Ir, W- Proximity bilayers: Mo/Au, Mo/Cu, Al/Ag, Ir/Au, Ir/Pt, etc.
RN : 10 mΩ ∼1 Ω
Readout: SQUIDHigh energy resolution + Low energy threshold + Fast + MUXLimited linearity and limited dynamic range, Absorber selective (or chip carrier)workingpoint
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Kinetic Inductance Detectors

Yong-Hamb Kim<Nature 425 (2003) 817 >

•

•
•
•
•

Pair breaking superconducting detector:
Quasiparticles are electron-like excitations insuperconductors from breaking Cooper pairs
Superconductor as the inductor in a LC resonance circuit
Breaking pairs changes the Kinetic inductance
Easy to MUX (on one chip)Non-equilibrium detector~ GHz frequency comb
HEMT15UGAP 2022

Sensor performance (example)

Yong-Hamb Kim“Superior dynamic range with high resolution”
Am241 full spectrum
MMC with gold foil absorberwith C ~ 0.3kg CaMoO4
PTB SQUIDGold foilabsorber<2013 KRISS>KRISS MMC

0.3 keV FWHM
for 60keV γ

0.9 keV FWHM Gaussian widthfor 5.5MeV α

 A test result with an MMC.
 NTD Ge thermistors also have similar performance.

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Yong-Hamb Kim

High resolution detection of heat signals

 Crystal target- Many DBD nuclei can be used whenfound in a crystal form

 Many ββ nuclei test Qββ > 2.6 MeV possible for 48Ca, 82Se,100Mo, etc.
 Low env. γ bkg.

Heat (Phonon)
sensor

Absorber crystal
containing DBD nuclei
TeO2 Li2MoO4 CaMoO4
CdWO4 ZnSe, CaF2 etc.

Environmental γ
background17

Yong-Hamb Kim

UGAP 2022

Simultaneous phonon-scintillation detection

Heat (Phonon)
sensorLight (Scintillation)
sensorScintillation

 Scintillating crystal as target material

Scintillator

Scintillating crystal 
Active bkg. Rejection
using L/H ratio and PSD

L/H Ratio

Li2MoO4 CaMoO4CdWO4 ZnSe, CaF2 etc.

2.6MeV

Phononβ/γ signals

2.6MeVEnergy(Phonon)18

LT 0νββ Projects
 This is a short introduction for LT 0νββ searches.
 The summary may not cover all of those 0νββ
project using LTDs.

UGAP 20220νββ Experiments
Methods

Loaded Liquid Scintillators
Ge semiconductors
TPCs (liquid, gas)

Low-temperature thermal
calorimeters

Yong-Hamb Kim

Isotopes
130Te: SNO+, JUNO

136Xe: KamLAND-Zen
76Ge: GERDA, Majorana DemonstratorLEGEND, CDEX

136Xe: EXO200, nEXO

NEXT
PandaX-III, R2D248Ca: CANDLES-LT R&D
82Se: CUPID-0

100Mo: AMoRE, CUPID-Mo, CUPID
130Te: CUORE

Tracking chambers

82Se: SuperNEMO

Inorganic scintillators

48Ca: CANDLES20UGAP 2022

30 years of 0νββ searches @LNGS

CUORICINO
2003-2008
62 TeO2 crystals(11 kg 130Te)

CUORE-0
2013-1552 TeO2 crystals(11 kg 130Te)

Yong-Hamb Kim

CUORE
2016743kg TeO2 crystals(206 kg 130Te)

fig. from S. Dell’Oro’ talk in DBD Shanghai 201721

UGAP 2022

TeO2 for 130Teββ-decay nuclei
with Q > 2 MeV

Q(MeV)

Abund.
(%)

48Ca → 48Ti

4.271

0.187

76Ge → 76Se

2.040

7.8

82Se → 82Kr

2.995

9.2

96Zr → 96Ru

3.350

2.8

100Mo → 100Ru

3.034

9.6

110Pd → 110Cd

2.013

11.8

116Cd → 116Cd

2.802

7.5

124Sn → 124Ge

2.228

5.8

130Te → 130Xe

2.528

34.2

136Xe → 136Ba

2.479

8.9

150Nd → 150Sm

3.367

5.6

Yong-Hamb Kim

130Te

 Q = 2528 keV (between 208Tl line (2615 keV)and its Compton edge) Large natural abundance : 34.2%
TeO2 crystals Debye Temp. ~ 230 K
 High crystal quality can be achieved.
 Low radio contaminants
 Do not scintillate  Particle ID not allowed

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From CUORICINO, To CUORE, & ..

CUORICINO

CUORE-0

CUORICINO
2003-2008
62 TeO2 crystals(11 kg 130Te)
T1/2 > 2×1024 y

CUORE-0
2013-1552 TeO2 crystals(10.9 kg 130Te)
T1/2 > 4×1024 y

Yong-Hamb Kim

CUORE
2016743kg TeO2 crystals(206 kg 130Te)

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UGAP 2022

Yong-Hamb Kim

CUORE Tech for 0νββ search wih LTD<I.Nutini ν-2022>

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Yong-Hamb Kim

CUORE Result (130Te 0νββ ) <I.Nutini ν-2022>• CUORE aims to collect 3 t·yr of TeO2
• CUPID is the follow up.

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Evoluion from CUORE to CUPID

Yong-Hamb Kim

CUORE: Cryogenic Underground Observatory for Rare Events
CUPID: CUORE Upgrade with Particle IDentification
CUPID0Zn82Se (5.17kg 82Se)
CUORE
743kg TeO2 crystals(206 kg 130Te)- Successful ton scale DBD
at 10 mK
- No particle ID- NTD- ZnSe Scintillating crystal- Q = 2995 keV- Successful partile ID withlight detectors- NTD

CUPID-Mo
Li2100MoO4 (2.26kg 100Mo)

CUPID
Li2100MoO4(240kg 100Mo)- Li2MoO4 Scintillating crystal- 100MoEnrichment > 95%- NTD- Li2MoO4 Scintillating crystal- Q = 3.34 keV- Good resolution, Particle ID- Low background, easy to grow
- NTD

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UGAP 2022

Yong-Hamb Kim

CUPID-0 with Zn82Se
82Se

Pulse shape of light signals

 Q = 2995 keV > 208Tl line
(2615 keV) Natural abundance: 9.2%
ZnSe scintillates at LT.

Fully mounted CUPID-0 detector
to a wet DR in LNGS

<L.Pagnanini ν-2022>

T1/2 > 4.7 × 1024 y (90% C. I. limit)
mββ < 276-570 meV

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CUPID-Mo100Mo

 Q = 3034 keV > 208Tl line (2615 keV) Natural abundance : 9.7%
 T1/2 (2ν) = 7.1×1018 y: the largest ββ decay rate

Yong-Hamb Kim<A.Zolotarova ν-2022>
7.4 keV FWHM at Q

Li2MoO4 : Scintillating molybdates, Selected
NTD Ge, Cold JFETEDELWEISS cryostat

20 modules

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UGAP 2022

CUPID-Mo Results

Yong-Hamb Kim<A.Zolotarova ν-2022>

T1/2 (0𝜈𝜈) > 1.8×1024 y (90% C. I. limit)mββ < 280-490 meV
 Best limit on 100Mo 0𝜈𝜈ββ half- life The most precise measurement of 100Mo 2𝜈𝜈ββ29

UGAP 2022

CUPID

Yong-Hamb Kim<A.Zolotarova ν-2022>• Heat-Light detection: Li2100MoO4 + NTD• Particle Identification• 100Mo Enrichment > 95%• 1596 crystals and 240 kg of 100Mo• FWHM <10 keV at Q (3034 keV)
• CUORE cryostat

Background goal: 10-4 ckky
Discovery sensitivity at 3𝛔𝛔:T1/2(100Mo 0νββ) = 1027 year
mββ ~12-20 meV30

UGAP 2022

Yong-Hamb Kim

AMoRE

AMoRE: Advanced Mo-based Rare process Experiment
100Mo

 Q = 3034 keV > 208Tl line (2615 keV) Natural abundance : 9.7%
 T1/2 (2ν) = 7.1×1018 y: the largest ββ decay rate
40Ca100MoO : enriched 100Mo and depleted 48Ca
4: Selected for a pilot and AMoRE-1’: High Debye temperature: TD = 438 K

Li2100MoO4: Selected for AMoRE-II
MMC for heat and light detection

L/H ratio

PSD

10keV FWHM
for 2.6 MeV

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UGAP 2022

AMoRE Progress

Yong-Hamb Kim

Single module
AMoRE-Pilot- 2018

AMoRE-I
Now

AMoRE-II
Being prepared32UGAP 2022

AMoRE Pilot result

Yong-Hamb Kim• 48deplCa100MoO4: 6 crystals 1.9 kg (0.9kg 100Mo)• Proof of the AMoRE detection principle• Understanding of the background components &reduction of them.
• Background level of ~0.5 ckky at 2.8-3.2 MeV- n-induced γ, Internal bkg, rock/air-radon γ- Internal background— arXiv:2107.07704• T1/2 (0ν) > 3.2×1023 years at 90% CL.

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UGAP 2022

AMoRE Pilot  AMoRE-I

Yong-Hamb Kim• 18 crystals: 13 48deplCa100MoO4 (4.58 kg) + 5 Li2100MoO4 (1.61 kg)• Total crystal mass 6.19 kg (3.0 kg 100Mo)• MMC sensor: Au:Er ➔ Ag:Er• Using same cryostat + two stage temperature control: ⟨ΔT⟩ < 1 μK
• Shielding enhancements:- Outer Pb: 15 ➔ 20 cm; neutron shields- boric acid silicon + more PE / B-PE
- More muon counter coverage- More supply of Rn-free air.

at 12 mK, σ(ΔT) = 0.58μK

30 days, 1Hz sampling

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AMoRE-I (Preliminary) Results

Yong-Hamb Kim<YM Oh ν-2022>
Data taking• Data taking (Science) started Dec./2020• Data for 1.67 kg 100Mo exposure is analyzed.
• To be continued till 2023.
• 10 – 30 keV FWHM@2.6MeV (15 keV average)

T1/2 (0𝜈𝜈) > 1.2×1024 y (90% CL.)with 1.67 kg 100Mo exposure

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AMoRE-II in prepration

Yong-Hamb Kim• In a new underground lab (Yemilab)• With new cryostat and new shields

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AMoRE-II Cryogenics

Yong-Hamb Kim• Three PTRs (PT420 RM)• Dilution refrigerator (delivered)- 5.4 mK base temperature- 7 uW at 10 mK50 K4K1K50 mK10 mK3.4 ton• Spring Suspended Still with Eddy
Current Damper• Independent holding structure fordetector tower••••

1 m diameter M.C plate
26 cm thick inner Pb shield
450 detector towers
Li100MoO4 (~ 100 kg 100Mo at final stage)

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UGAP 2022

AMoRE-II from chips to the house

Yong-Hamb Kim

582mm

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AMoRE-II Background budgets

Yong-Hamb Kim

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AMoRE-II goals

Yong-Hamb Kim• AMoRE-II for T > ~5×1026 years by 100 kg of 100Mo × 5 years running.
• Reduction of background level down below 10-4 ckky.

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UGAP 2022

CANDLES-LT

Yong-Hamb Kim

48Ca Q = 4271 keV. The highest Q
 Natural abundance : 0.187%
CaF2 , CaF2(Eu)

Low Temp. R&D : Osaka Univ. + IBS/KRISS41UGAP 2022

Heat & Light detection with CaF2

Yong-Hamb Kim• Promissing demostration for heat-light detection with
MMCs from CaF2 crystals at 10-20 mK• Clear particle identifcation

Tetuno 2020 J Phys Conf. 1468 012132<CANDLES-LT>• Poor energy resolution due to position dependence

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UGAP 2022

Heat & Light detection with CaF2Yong-Hamb Kim

30 mBq of 226Ra (U-chain) within an R&D crystal
Delayed coincidence (222Rn → 218Po → 214Pb)
Δt < 3 min• High resoltuion with position dependencecorrection• Further R&D should continue.

<CANDLES-LT>

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R&D challenges

UGAP 2022

Technical tasks and challenges

Yong-Hamb Kim

 Unresolved pileups.
 Single-site event selection.
 Resolve position dependence (for fast sensors) Multiplexing capability

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UGAP 2022

Yong-Hamb Kim

Unresolved pileups of 100Mo 2νββ signals•1 kg 100Mo  ~20 mBq of 2νββ•Timing resolution for pileup rejection:~ 40 μs for 10-5 ckky in a Ø50×50 LMO (in most conservative way)

T1/2 (2νββ 100Mo) > 7.1×1018 year

With heat-signal rise-time only.
120 μs at 10 mK, 60 μs at 40 mKLight signals: τfast~200 μs
 ~ 100 μs rejection possibility

Astroparticle Phys. 91:105 (2017)•Should improve τ of light (heat) signals•

Likelihood pileup rejections should be implemented.
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UGAP 2022

Yong-Hamb Kim

R&D proposal to multi-site event rejection<Hansen ν-2022>

fast light signals

R&D result for fast heat signals(IBS)

singlemulti
fast phonon signals• Fast heat & light signals.
• Finite phonon speed: ~105 cm/s
• PSD with time dependence can bestudied.

R&D setup forfast phononphoton signals:
30 us rise time
(Heidelberg)
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UGAP 2022

Yong-Hamb Kim

SWOT for LT Detectors in 0νββ searchStrengths
 High energy resolution
 Particle ID
 Proven technology

Weaknesses Surface effect Unresolved pileups Bkg from copper Number of channels

Opportunities Use of Cherenkov light New crystal targets
 Single-site selection Multiplexing Possible collaboration

Threats
 Isotope production
 Crystal growing Purification

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UGAP 2022

Closing remarks

Yong-Hamb Kim 0νββ search projects with LT detectors are well established experiments.
 The technology provides promising performance in energy resolution,
background reduction method, and scalability of the detector size.
 Those LT projects aim to investigate 0νββ process in many nuclei.

Stay tuned !

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