0νββ tpc : axel · 2020. 12. 30. · axel u z + w a t m m o x ² t ô ¤ É ç ª Ç á µ p º...

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1 ڀݚ ˙հ 0νββ յ୳ͷΊͷߴѹΩηϊϯΨε TPC ݕ ث: AXEL ։ฃಆ هژେ ཧڀݚՊ ߴΤωϧΪʔཧڀݚ தଜ , [email protected], [email protected] ٢ [email protected] 2020 ( 2 ) 11 12 1 Ίʹ χϡʔτϦϊϚϤϥφΛ൱ͱ ੜΒ 80 Ҏܦɻ༄ɾήϧϚϯΒʹΑ ఏএΕγʔιʔʹߏػΑΔχϡʔτϦϊ ͷݱϨϓτδΣωγεʹΑΔɾඇରশӉ ͷݯىͷઆΕχϡʔτϦϊϚϤϥφͰΔͱΛલఏͱΔΊɼͷݕඇৗʹॏཁͰ ΔɻχϡʔτϦϊΛΘͳೋॏϕʔλյ (0νββ յ) ͷ୳ࡏݱχϡʔτϦϊͷϚϤϥφͷ ݕΛಘΔ΄΅།ҰͷखஈͰΔɻΘΕΘΕͷΈʹ ҎલͷߴΤωϧΪʔχϡʔεͷߘͰઆ [1]ɻ· [2] ͳͲʹ 0νββ յ୳ ʹࡧͷղઆΔɻͰͷ 0νββ յ ΛऔΓרʹگ؆୯ʹड़ ɻ ࡏݱߦதͷ 0νββ յ୳ݧͷ΄ͱΜͲχϡʔ τϦϊ֊ٯߏͰΔ߹ʹΓಘΔҬΛ ͱΛϚΠϧετʔϯͱΔ ( ΕχϡʔτϦϊͷ༗Ͱ m ee = 20 meV ʹର ԠΔ)ɻͱΖͷχϡʔτϦϊৼಈݧͷ ՌΒχϡʔτϦϊॱ֊ߏΛͱ ΕΊΔɻ··Ͱͳ গઌʹͳΓɼ0νββ յ୳ʹݧ ॱ֊ͰΔՄΛߟ m ee = 1 meV ·ͰΛ୳ͰΔΑͳɼΒʹײߴͳݧٻΊΒ ΕΊΔɻΕඇৗʹνϟϨϯδϯάͳཁ ٻͰΓɼͱ 10 ఔͷݱతͳλΠϜεέʔ ϧͰͷײ·Ͱ୳ΑͱΔͱɼτϯϨϕϧ ͷλʔήοτΛ༻ҙɼόοΫάϥϯυϑϦʔͰ ΔͱඞਢͱͳΔɻ·ࠓͰେߴΤωϧΪʔ ղɼ·ΠϕϯττϙϩδʔͷͲΕʹಛԽ ઓͷݧओͰɼকདྷܭըͱ Ge ݕثΛ༻ݧ߹େͷ Ge ݕʹثΑΔ୳ ΛఏҊΓɼେͰͷ୳ͷදͰ KamLAND-Zen ʹݧΤωϧΪʔղΛ ݕظ ث(KamLAND2-Zen) ఏএΕ Γͱɼ·ʹهͷཁٻΛຬݕثͷ ܭըɾ։ਐΊΒΕΔɻͷͻͱͷղͱߴѹ ΩηϊϯΨεΛ༻λΠϜɾϓϩδΣΫγϣϯɾνΣ ϯόʔ (TPC) Δɻ 1.1 AXEL ݕ ثAXEL ߴѹΩηϊϯΨε TPC Ͱɼ0νββ յ୳ʹͳେɾߴΤωϧΪʔղɾڧͳഎ ܠڈͱ 3 ͷཁૉΛͶඋݕثͱ ΘΕΘΕࡏݱܭɾ։ΛߦΔɻ8 ؾѹͷ ߴѹΨεΛ༻ΔͱͰ 2–3m ఔͷେͷݕ ثͰτϯεέʔϧͷେͷյΛอͰΔɻAXEL ͰؾମΩηϊϯߴΤωϧΪʔղΛ ݶ׆ʹɼͷݕग़ʹΞόϥϯγΣ෯Λ ݕग़ͷΘΓʹΤϨΫτϩϧϛωοηϯε (EL ) Λ༻෯ɾݕߏػΛ༻ΔɻΕʹΑ Γ 136 Xe ͷ 0νββ յʹΔ Q ͰΔ 2458 keV Ͱ 0.5%(FWHM) ͱඇৗʹߴΤωϧΪʔղ ΛɻElectroluminescence Light Collection Cell (ELCC) ͱΘΕΘΕݺΜͰ։ΔಡΈग़ ػߏͷཁΛਤ 1 ʹɻELCC ظతʹ։ ηϧঢ়ͷ PTFE (polytetrafluoroethylene) ͷߏ ͷԼΛಉΑʹͷۃͰڬΈɼΒʹη ϧͱʹஔΕݕ ثMPPC(দϗτχΫεɼ S13370-3050CN) ΒΔɻۃʹߴѹΛҹ ՃΔͱͰηϧ෦ʹߴΛܗɼυϦϑτ 122

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Δ 0νββ
ΛΓ
τΔΓΔΛ
Δ)Ζχτ
ΛΔΑΒΒ
ΕΔΕνδ
λοτΛουϑ
ΔΔΤω
ΠττδΕ
ΛΓ
KamLAND-ZenΤωΛ
Τω
ΘΕΘΕΛΔ8
τεΛΔAXEL
ΞγΣΛ
0.5%(FWHM) Τω
ΛElectroluminescence Light Collection Cell
(ELCC) ΘΕΘΕΜΔ
Λ 1ELCC
ΑELΛΔMPPCΑ
ΔΖΜTPCηοτ
ΛΔΓΕΑ
ΔELCC PTFEΛΔ
AXELΤω
Δ [1] ELCC
ΒΒΕΔ
TER AGET ΛΛΛ
(οτ)
σΟετΛ
Δ
ΛετϑΥε 7.5 mmο
ΑΓ 10 mmον
5 mm( 2)Ε
2 180 L
ΘΕΘΕΕ 10 L αΠζΛ
ΛΕΒ
7 8 9 10 11 12 13 pitch [mm]
0.2
0.4
0.6
Simulated energy resolution for 30keV e-
2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7
% F
γγ (8)
ονΛγγ
1.74%(FWHM)Λ
ΔΛΔ
Λ
180 LΔ 180 LΔυ
ϑτΛΔϑΟυδΞ
1500νωΔν
δΕΛΘ
MPPCΑϒ
νωΠΛΔΔ
ϒΛΔνωMPPC
τΤυυAxFEBΛAxFEB
ΕΔΖ EL 200 ns Γ photon equiv-
alent (p.e.)Β 4000 p.e.
150 µsΑMPPCΠΩ
ϒγχλ ns 1 p.e.
μΧτΔ
ΩϑΟλ) ΕΕΛ
ADCΑΛΔαΩϑΟλ
ADCατγ
ΑΛMPPC
[5]Λ
Δ PMT (τχεR8520-406)Λ
ELCCFPCΛ 2019
3Λ 1ϑΣζELCC
ΛΛ4ΩηΨεΛ
124
4
+ – VADJ
VADJ
VADJ
ΛΔDCΧο

Θ
ΜΔ
ΓτϒΕΓΒ
ΕΘΕ)
ΘΕ
1 560 LΩη
ΨεΕ
ΩηΨεΛΔΑ
(500 mL)ΛΑ
ΔΛ
1ΩηΑΓ
ΔΛ
ΓΒΩηΛ
ΛΛ
ΛΒΓΩη
ΛΔΛ
ηοτΛΓ1ηοτγ
ΕΔΩηΛολ
ΛΒΑΓΩη
ΞτΛ
ΕΑΓΛ
RGAΨεΕ

λζ (IBSMB-601HPAL)Β
ΛΔΑ
125
5
Δ

ΨεΛΛ
Γ ΕELCCΛδ
6)
DAQΤDAQ
τϒ 3.1Δ
Α Δ4 22NaΛ
Λ 7 511 keVΤωεϖ
τΔ511 keVΩηX
Entries 400419 A_Escape_Kb 6.04± 13.86 mean_Escape_Kb 0.0± 477.4 sigma_Escape 0.19± 3.25 A_Escape_Ka 6.35± 94.46 mean_Escape_Ka 0.0± 481.2 A_511keV 6.6± 190.4 mean_511keV 0.1± 510.9 sigma_511keV 0.094± 3.235 a_linear 0.038±0.585− const 18.5± 320.9
460 480 500 520 540 560 Energy [keV]
0 20 40 60 80
100 120 140 160 180 200 220
En tri
es /
bin Entries 400419 A_Escape_Kb 6.04± 13.86 mean_Escape_Kb 0.0± 477.4 sigma_Escape 0.19± 3.25 A_Escape_Ka 6.35± 94.46 mean_Escape_Ka 0.0± 481.2 A_511keV 6.6± 190.4 mean_511keV 0.1± 510.9 sigma_511keV 0.094± 3.235 a_linear 0.038±0.585− const 18.5± 320.9
7: 511 keVΤωεϖτ
511 keV ΩηX (30 keV)
ΤεΔ
ΔΤω 511 keV
1.49 ± 0.04% (FWHM) ΛΕ
ΒΛ √ E Q
Δ 0.68% (FWHM)Ε
ΔΒΤω
33.62 keV)Τε (481 keV)ϑ
1.18± 0.01% (FWHM)Λ
)ΓΑΔΤω
(blob)Δ
Γ
Β
Δ
3
ELCCδΔ
ELCC ΛωδΔ
ογΕηΓ
ογ
ογΛεοτΔΛ
εοτογΓ
MPPC ογ (
ΘΕΔMPPC)ηΑΔ1
MPPC MPPCΓ
50−
0
ΘΒΛ vetoνω
Γ
ΠΕΔΒ
ΤωΛ Q
384 keV)22Na(511 keV)137Cs(662 keV)Δ
COVID-19
ϑΟλ (Ωγϒολ)Λ
EEL = 3 kV/cm/barΛΔ
ΓΔ
ΛΧοτυνωοτΔ
2 < z < 9.975 cmοτΔ
ΛELCCγγ
ΕΔz < 2 cmΛ
Δ
ΓΕΒ
Δ 10137CsΛΒΕ
ΜdE/dxΓ blob
ΕΔΘΓ
Number of Photons 0
0
50
50−
0
50
50−
0
ωεϖτΨϑΤ
ΤωΔ
ΓΤωΔ
0 100 200 300 400 500 600 700 Energy [keV]
0
2
4
6
8
10
12
: gamma-ray full peaks onlyEa : including X-ray peaksEa
: including X-ray peaksbE+Ea
ΒΕΓΒΤω
ΔΔΕΛ
Δ
2.3ΤωΔ
ΒΔ
USBΧδΛΠετ
ΠετΧΕ
)ΔΒΒ2.2

Λ ELCCεςο
Λ12χοτ ELCCδ
(672νω) 20 cmϑΟυδΛΠ
λ QΔ 2458 keVΤω
ΔΛΔ
ωτοΩ
ουΛ

129
9
ΑΔΔ
ΕΔ 2458 keV 0.4%
ΤωΔ
Λ DenseNet [6]Λ
σΛγγΑΔΛ
γγΑΔ
ΔΛτεο
υϑΒΕΔ136Xeλ
ΓχτΔ
ΛΔΔ Ε nEXO
NEXTΩηΛ[7]
λAXEL
ΓnEXOΩη
ϒΔΩη
JSPS 15H0208816J0946217J00268
AxFEBKEK Open-It

OBΛ
Τωχε34-4, 287 (2016).
198 (2011).
Τωχε24-3, 182
[3] S. Ban, et. al., Nucl. Instrum. Meth. A. 875,
185 (2017), arXiv.1701.03931.
[4] S. Obara, et. al., Nucl. Instrum. Meth. A. 958,
162803 (2020), arXiv.1909.09343.
[5] K. Z. Nakamura, et. al., IEEE Trans. Nucl. Sci.
67-7, 1772–1776 (2020), arXiv.2001.20104.
[6] G. Huang, et. al.,2017 IEEE Conference on
Computer Vision and Pattern Recognition
(CVPR), Honolulu, HI, 2261–2269 (2017),
arXiv.1608.06993
(2019).
Phys. Rev. Lett. 120, 132504 (2018).
130