Present Status of the DCBA Experiment H. Iwase (KEK) on behalf of - - PowerPoint PPT Presentation

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Apr 06, 2023 355 likes •617 views

"Double Beta Decay and Neutrinos" (DBD11), Osaka Japan Present Status of the DCBA Experiment H. Iwase (KEK) on behalf of the DCBA collaboration 1 Double beta decay experiments Scintillation/Cal n/Calorimetry (source = dete =

SLIDE 1

Present Status of the DCBA Experiment

H. Iwase (KEK)
n behalf of the DCBA collaboration

"Double Beta Decay and Neutrinos" (DBD11), Osaka Japan

SLIDE 2

Double beta decay experiments

Scintillation/Cal n/Calorimetry (source = dete

= detector)

ionization COBRA (130Te, 116Cd, etc.) Majorana(76Ge) GERDA(76Ge) scintillation CANDLES(48Ca) XMASS(136Xe) KamLAND-Zen(136Xe) bolometry CUORE(130Te) GERDA(76Ge) KamLAND-Zen(136Xe) SNO+(150Nd)

ionization+scintillation

EXO(136Xe) Combination (source ≠ detector) NEMO3 (100Mo, 82Se,150Nd, etc.) Super NEMO (100Mo, 82Se, 150Nd, etc.) Tracking (source ≠ detector) DCBA (100Mo, 150Nd, etc.)

SLIDE 3

DCBA method

pickup anode circle cosine curve

→ →

y-z 投影

y

cathod anode cathod

x y

→

B

p (MeV/c) momentum, T (MeV) k. energy, r (cm) radius, me (MeV/c2) rest mass of e- B (kG) magnetic flux density, λ pitch angle

Y-Z surface X-Y surface pickup

SLIDE 4

DCBA experiment

DCBA-T3

DCBA-T2-detector in T3 (=T2.5)

higher resolution higher event rates 5 24h operation

2005

DCBA

charge dividing

2007

DCBA-T2

6 mm pitch wires (xy + xz)
100Mo source (natural Mo 30g)
0.6 - 0.8 kG magnetic field
conducting magnet: 9h/day (Mo. - Fr.)

2011

present DCBA-T2.5

6 mm pitch wires (xy + xz)
100Mo source (natural Mo 30g)
0.8 kG magnetic field
super-conducting magnet:

24h nonstop operation

2013

DCBA-T3

3 mm pitch wires (xy + xz)x6
150Nd (natural Nd2O3)
maximum 3 kG

2017

MTD

(tentative name) • 150Nd (condensed, several 10 kg)

SLIDE 5

DCBA T-2 results

SLIDE 6

Energy resolution of DCBA T-2

Measurement

Energy spectra of internal conversion electrons 0.48 (1.5%), 0.56 (0.6%), 0.98 (7.0%) and 1.05 MeV (2.4%) from 207Bi

chamber conditions

He (90%) + CO2 (10%) 1 atm
B = 0.8 kG
wire pitch = 6 mm

SLIDE 7

214Po half-life measurement by T-2

214Bi β-decay 214Po α-decay 214Po 半減期評価

T1/2 = 144 ± 46 μs

(ref. 164.3 μs)

e- e-

214Bi β-decay → 214Po α-decay detection and the 214Po half-life 214Po half-life

vertex point vertex point

SLIDE 8

DCBA T-2 result

SLIDE 9

DCBA T-3

SLIDE 10

Super conducting magnet for T-3

coolant-less
GM refrigerator

for DCBA T-3

B = 0.2 T ± 0.5% (ΔE ~ 80 keV )
φ600mm x L600mm

SLIDE 11

SLIDE 12

center 12

Magnetic field uniformity of DCBA-T3

2000 G

SLIDE 13

DCBA T-2.5

DCBA-T2 T3 superconducting magnet

SLIDE 14

present result of DCBA T-2.5

SLIDE 15

DCBA T-2.5 events

SLIDE 16

against noise events

> additional veto counter

whole veto counter inside the magnet

> move to underground

SLIDE 17

recent DCBA time table & ββ events

× × ββ event

β1 = 0.82 MeV β2 = 0.67 MeV

hour day

6 12 18 24 2011/07/02 2011/08/01 2011/08/31 2011/09/30 2011/10/30

analysed not analysed

× × × × × × × × × ββ event (not included in

the final graph)

SLIDE 18

DCBA data analysis - raw data

X-Y surface X-Z surface

SLIDE 19

DCBA data analysis

SLIDE 20

DCBA data analysis

SLIDE 21

DCBA (T-2 + T-2.5) 100Mo ββ results

β1 + β2 single β

SLIDE 22

MTD - the next DCBA

27 source plates

SLIDE 23

Summary

DCBA ββ-decay data taking was started by T-2
21 2νββ candidate events found by T-2
DCBA-T3 super conducting magnet was finished
T-2 chamber in T-3 s.c. magnet (T-2.5) is in operation
24h data taking
T-3 is under development for higher

energy resolution and source amount

SLIDE 24

SLIDE 25

recent DCBA time table & ββ events

6 12 18 24 7/2 7/5 7/8 7/11 7/14 7/17 7/20 7/23 7/26 7/29 8/1 8/4 8/7 8/10 8/13 8/16

analyzed not analyzed

× × ×

1week

× ββ event

β1 = 0.82 MeV β2 = 0.67 MeV β1 = 1.07 MeV β2 = 0.50 MeV β1 = 0.45 MeV β2 = 0.43 MeV