8li + x 反応断面積測定 - research.kek.jp research...
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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
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
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