軽い中性子過剰核領域での軽い中性子過剰核領域での軽い中性子過剰核領域での(((ααα, n), n), n)天体核天体核天体核

反応率の直接測定反応率の直接測定反応率の直接測定

石山博恒

高エネルギー加速器研究機構

Y. Hirayama1, N. Imai1, Y. X. Watanabe1, H. Miyatake1, M. H. Tanaka1, N. Yoshikawa1, Y. Fuchi1, S. C. Jeong1, I. Katayama1, T. Ishikawa2, K. Nakai2, T.

Hashimoto3, S. Mitsuoka3, K. Nishio3, M. Matsuda3, S. Ichikawa3, H. Ikezoe3, P. K. Saha3, A. Sato4, T. Shimoda4, S. K. Das5, Y. Mizoi5, T. Fukuda5

1IPNS KEK, 2Tokoyo University of Science, 3JAEA, 4Osaka University, 5Osaka Electro-Communication University

超新星爆発時の反応ネットワーク

p

n

D

3He

T

4He

6Li 7Li

7Be

8B

9Be

10B

11C

10Be 11Be

11B 12B

12C 13C 14C

13N 14N 15N

15O 16O

15C

16N

17O 18O 19O

9Li

6He 8He

11Li

12Be

13B 14B 15B

16C 17C

17N 18N 19N

20O 21O 22O

18F 19F 20F 21F 22F 23F

8Li

Neutron

Prot

on

STABLE

RNB > 103 pps

8Li,12B,16N(α, n) ⇒　測定終了

Supernova Explosion

T9=3Alpha & Neutron

Core

T9=10Neutron & Proton

T9=1Neutron & Seed

α-process

r-process

17B 19B

18C 19C 20C

20N 21N

軽い中性子過剰核の反応率の系統測定(α, n)反応

RNB: JAEA-RMSDetector: MSTPC + Neutron counters

T9=2.5-5

T9 = 2.5-2

T9 = 2–0.5

Direct Measurement of (α,n) reaction

E=1~2 MeV/uI=103～104pps

RNB

Detector

MSTPC & Neutron counter

ExperimentExperimentExperiment

MCP Start counter (PPAC) MSTPC

Counter gas + target gasHe+CO2

n

　　　　　　　　efficiencyεneutron ～ 40%∆Ωneutron 31.4% of 4πεMSTPC 100%ΩMSTPC 100% of 4π

Radio-active Nuclear BeamProduction

8Li,12B(α ,n)Reaction cross section

Neutron counter

Radioactive Nuclear beam (RNB) production (RMS)

ExperimentExperimentExperimentExperimentExperimentExperiment

primary beam => transfer reaction => RNBto suppress particles of the primary beam

=> JAERI-RMS

primary beam ⇔ RNB

velocity filter

(Eρ + Bρ)

RNB E [MeV] Primary Production Intensity Purity6He 10 7Li 9Be(7Li, 6He) 5.9×103 70%8Li 14.6 7Li 9Be(7Li, 8Li) 4.8×104 99%12B 24 11B d(11B, 12B) p 2.0×104 98%16N 32 18O d(18O, 16N)α 9.4×104 98%

Detector system for measurement of (α,n) reaction

E=1~2 MeV/uI=103～104pps

RNB

Start counter (PPAC)MCP

MSTPCCounter gas + target gasHe+CO2, CH4

Neutron counter

n　　　　　　　　efficiencyεneutron ～ 50%∆Ωneutron 31.4% of 4πεMSTPC 100%ΩMSTPC 100% of 4π

dE/d

xReaction point

Instruments for (Instruments for (αα, n) experiment, n) experiment

AnalysisAnalysisAnalysisReaction events ⇔ Background

dE/PAD ↑> 30 keV

∆E-E plot

Elastic scattering event

Event selection gates1. Multiple-track2. Momentum3. Difference of scattering angle

etc…Typical 8Li(α, n) reaction event

ResultResultResult

g.s.2.12 MeV

4.44, 5.02

6.74, 6.79,7.297.98,8.56,8.92

8Li(α, n)11B反

Ex in 11B averaged branching ratio(MeV) present previous

0.0 20.1(21) 24.3(126)2.12 6.6(12) 15.2(104)4.44 10.1(22) 4.2(72)5.02 17.8(27) 6.1(57)

6.74+6.79 18.9(27) 13.0(80)7.29 13.2(15) 12.5(104)7.98 11.7(12) 10.6(71)8.56 2.4(05) 0.0(21)8.92 - 14.2(67)

present: Ecm = 0.7 - 2.6 MeVprevious: Ecm = 1.5 - 7.0 MeV

励起関

T. Hashimoto, Dr. thesis

0

200

400

600

800

1000

0 0.5 1 1.5 2 2.5 3

PresentR. N. Boyd, et al.X. Gu, et al.Y. Mizoi, et al.S. Cherubini, et al.Suranjan

Cro

ss se

ctio

n (m

b)

Energy (MeV)

T9=1

T9=2

T9=3

Ex = 10.88 MeV

Branching ratio of 10.88 MeV

g.s 1st 2nd 3rd 4th+5th

25(8) 7(4) 23(7) 5(5) 37(23)

Ex = 10.88 MeV

E(8Li) = 14.6 ⇒ 12.5 MeVp = 220 Torr ⇒ 140 Torr

8Li(α, n)11B反応

S. K. Das, Dr. thesis

Reaction rate of 8Li(α, n)11B Result of network calculationCalculated by T. Sasaqui

8Li(n, γ)9Li

Present τ=0.005sec:Ypresent/Yinclusive=1.04τ=0.05sec:Ypresent/Yinclusive=1.80

PresentInclusive measurementsInclusive

)21()(4

)exp()()(8

22

0

2/3

AvvZZ

E

dEEE

TkEESTk

Av

jig

g

bb

ηπ

πσ

=

−−>=< ∫∞

−

12B(α, n)15N reaction

Known Level of 16NEx Ecm G[keV]

1 11.61 1.51 22011.70 1.60 <1211.75 1.65 <50

2 11.92 1.82 39012.09 1.99

3 12.39 2.29 2904 12.57 2.47 1805 12.88 2.78 1556 12.97 2.87 1757 13.11 3.01

13.83 3.73

12

3

4

5

67

g.s 1-2nd 3rd 4-6th 7-8th

3(3) 14(7) 52(14) 16(7) 15(10)Branching ratio at Ecm=1.45 MeV

T. Ishikawa, Dr. thesis

103

104

105

106

107

108

109

1 1.5 2 2.5 3 3.5 4 4.5 5

present (exp.)Fowler(model)Wagoner (model)

Rea

ctio

n ra

te [c

m3/

sec/

mol

]

T9

( )31

915 45.28exp1004.3 −−×>=< TvN A σ

天体核反応率天体核反応率 1212B(B(αα, n), n)

ネットワーク計算で用いているWagonerの模型値との比較

dEkTEE

kTvNa ∫

∞⎟⎠⎞

⎜⎝⎛−>=<

0exp

)()2(

423

21 σ

πµσ

TRIAC ; Tokai Radioactive Ion Accelerator Complex

2000

4000

6000

8000

1 104

1.2 104

0 100 200 300 400 500 600 700 800

Cou

nts

Channel

8LiE = 3.7 MeV∆E/E = 2%

FromJune 2005

2005年12月13-15日、2005年12月19-21日8Li beam : I = 2×105 pps on target (MAX)E = 6, 4.8, 3.9, 2.4 MeVEcm = 1.2, 0.96, 0.78, 0.48 MeV

Reaction beam process detector status 8Li(α, n)11B TRIAC(105) r-, IM MSTPC + n 0.4-2.7 MeV測定終了8Li(p, α) TRIAC(105) r-, IM SSD8Li(d, t)7Li TRIAC(105) r-, IM SSD 0.5 – 1.5 MeV8Li(d, p)9Li TRIAC(105) r-, IM SSD8Li(d, α)6He TRIAC(105) r-, IM SSD 0.5 – 1.5 MeV8Li(d, n)9Be TRIAC(105) r-, IM GEM-MSTPC + n8B(α, p)11C RMS(104) pp, rp- GEM-MSTPC + SSD12B(α, n)15N RMS(104) r- MSTPC + n 1.1 – 3.7 MeV11C(α, p)14N RMS(104) rp- GEM-MSTPC + SSD15C(α, n)18O RMS(103) r- MSTPC + n16,17,18C(α, n) ? r- MSTPC + n16N(α, n)19F RMS(104) r- MSTPC + n 1.3 – 3.6 MeV (Isomer)9C(α, p) ? rp- GEM-MSTPC + SSD13O(α, p) ? rp- GEM-MSTPC + SSD22Mg(α, p)25Al TRIAC? rp- GEM-MSTPC + SSD 26Si(α, p)29P TRIAC? rp- GEM-MSTPC + SSD 30S(α, p)33Cl TRIAC? rp- GEM-MSTPC + SSD34Ar(α, p)47K TRIAC? rp- GEM-MSTPC + SSD

(α, p), 8Li(d, n)反応の直接測定

8Li beam ; 104 pps1.05 MeV/u

trigger counterMCPMSTPCCD4 gas p = 50 Torr

Neutron detector array

8Li(d, n)9Beσ～ 5 mb, 8Li beam ; 104 pps

Yield = 15.1 cnts/ 10 days, 200keV bin

問題点MSTPC ⇒空間電荷飽和　 beam intensity < 2×104 pps⇒　次世代MSTPC開発

Summary

軽い中性子過剰核の(α, n)反応断面積の系統測定　(@JAEA-RMS)　　MSTPC+Neutron counter

8Li(α, n)11B, T9 = 1-312B(α, n)15N, T9 = 2-5引き続き15C(α, n), 16N*(α, n)反応測定

8Li(d, p), (d, t), (d, α)反応断面積(@TRIAC) 8Li(d, n)反応断面積の測定(@TRIAC)

MSTPC+Neutron counter次世代MSTPCの開発

8B(α, p), 11C(α, p)反応断面積(@JAEA-RMS)