The β-decay half-life of 46Cr
Y. Wakabayashi
JAEA
(Japan Atomic Energy Agency)
Collaborators
CNS, Univ. of Tokyo
S. Kubono, H. Yamaguchi, T. Hashimotoa, S. Hayakawaa,
Y. Kurihara, D.N. Binh, K. David
RIKEN
Y. Gono, S. Nishimura
Osaka Univ. Y. Fujita
Univ. of Tsukuba T. Komatsubara
CSIC University
B. Rubio
Physics Department, University of Surey
W. Gelletly
Thanks for Clover Ge detectors
Tohoku Univ.
T. Shinozuka, T. Koike, S. Izumi
Scientific motivation
・The Gamow-Teller (GT) transition of proton-rich pf-shell nuclei
are interesting in nuclear physics as well as astrophysics.
・In the neutrino induced process
at the time of core-collapse of type II supernovae,
the GT transitions up to high excitation energies play important roles.
・Experimental knowledge for the GT transitions of unstable pf-shell nuclei
is know not well and required.
Study of  - decay for the proton-rich pf-shell nuclei
How to study?
Charge exchange (CE) reaction
・ Strong interaction
・ possible to measure
highly excited GT states
・ Relative B(GT) values.
 - decay
・ Weak interaction
・ B(GT) values from ft values.
・ difficult to measure
highly excited states.
・Measurement of accurate T1/2 and branching ratios in β- decay
・Deduce the B(GT) values
from the combination with β- decay and (3He,t ) measurements
-decay measurement of 46Cr
0+
46Cr
QEC = 7.603(20) MeV
T1/2 = 260 (60) ms, 240(140) ms
2.978
2.699
2.461
1.433
+
1 0.993
0+
0.0
?
g?
bGT = 0.216(50)
To determine
g
46V
T1/2 = 422.50(11) ms
Ref : T. Adachi et al. : PRC73, 024311 (2006)
T.K. Onishi et al. : PRC72, 024308 (2005)
Y. Fujita et al. : PRL95, 212501 (2005)
J. Zioni et al. : NPA181, 465 (1972)
1)Total half life with < 5 % error
2)Branching ratio (bGT)
3)New branches (g rays)
Experiment List
・Test experiment of production w/wo Gas, F1 deg., WF, etc..
(1) Apr. 2006 (1 day)
(2) May. 2006 (2 days)
(3) Sep. 2006 (2 days)
(4) Mar. 2007 (2 days)
・Development of 46Cr production and Ion Chamber
46Cr
(5) Jul. 2007 (2 days)
(6) Nov. 2007 (2 days)
(7) Apr. 2008 (2 days)
intensity Purity
1.3 cps
0.6 % at F2
1.7 cps
0.8 % at F3
2.4 cps
1.2 % at F3
・Half-life measurement of 46Cr β-decay
(8) Oct. 2008 (8 days)
5.6 cps
1.8 %
at F3
Beta-decay measurement of 46Cr
12C+36Ar
→ 46Cr + 2n
Primary target
CRIB
12C
target (0.56 mg/cm 2)
Primary beam
36Ar
Havar (2.2 um)
36Ar (3.0 MeV/u)
PPAC
(3.6 MeV/u)
80 pnA
Beam on/off : 500/700 ms
I.C. + DSSD(0.5mm)+SSD
PPAC
Clover Ge detectors
Use at a H.V. of 85 kV
MCP
Figure of experimental set-up at F3
DSSD(40x40) (X,Y,T,E)
500um
Beam
(～1.2 MeV/u)
Clover Ge
SSD (1.5mm)
MCP (X,Y,T)
(0.7um Mylar Window)
MCP : Beam monitor
I.C + DSSD : DE-E detector
DSSD, SSD : -ray detector
Ge : g ray detector
Clover Ge
Co-axial Ge
On(500ms) : On*MCP*DSSD
Off(700ms) : Off*(DSSD,SSD,Ge)
Ion Chamber (I.C)
Clover Ge 1.1um Mylar Widow
iso-Butane(25Torr)
Particle identification at F3
46Cr17+
(2%, 6 pps)
@80pnA
46Cr
46V
45Ti
46Ti
43Sc
36Ar
Purity(%)
2
9
2
16
5
51
Rate(pps)
6
27
7
49
14
157
260ms
422.4ms
184.8min
stable
3.891h
stable
Nuclide
Half life
Experimental Result
Decay spectrum of -decay events
Considered only 46V + 46Cr decay component
・45Ti : 3.08 h, 43Sc : 3.89 h >> 700ms (Beam-off )
・46Ti , 36Ar are stable nuclei
T1/2 of 46Cr was determined to 232(9) ms.
(Previous data：260(60) ms and 240(140) ms)
F(t) = Na(0) (1－
λb
λa－λb
+ Na(0)
)λa exp(－λat)
λaλb
λa－λb
exp(－λbt) + Nb(0) λb exp(－λbt) + Const
Na(0), Nb(0) : Number of 46Cr, 46V at t=0
λa, λb ： Decay constant of 46Cr, 46V
・λb (46V) can be fixed as 422.50(11) ms.
(cited in Nuclear Data Sheet)
Publication List
(1) Workshop
・Y. WakabayashiA, H. YamaguchiA, T. HashimotoA, S. HayakawaA,
Y. KuriharaA, D.N. Binh A, D. Kahl A, S. KubonoA, S. Nishimura B, Y. GonoB,
M .SugaC, Y. FujitaC
CNS, Univ. of TokyoA, RIKENB, Osaka Univ.C
「Half-life measurement of 46Cr」
SSRI2008, Osaka, Japan, Dec. 2008
(2) JPSJ meeting
・ Y. Wakabayashi A, H. Yamaguchi B, T. Hashimoto B, S. Hayakawa B,
Y. Kurihara B, D.N. Binh B, D. Kahl B, S. Kubono B, S. Nishimura C, Y. Gono C,
M. Suga D, Y. Fujita D
JAEA.A, CNS, Univ. of TokyoB, RIKENC, Osaka Univ.D
「Beta-decay measurement of 46Cr」
The third meeting of the nuclear physics divisions of APS and JPS, Hawaii, USA, Oct. 2009
(3) Journal
・The paper for this study of 46Cr will be submitted in this summer.
Summary
・The β-decay half-life measurement of 46Cr produced by 36Ar+12C
fusion reaction was carried out using CRIB of CNS.
・The half life of 46Cr was determined accurately, 232(9) ms.
(much better than previous data of 260(60) ms and 240(140) ms)
・This accurate half-life allows to use the merged analysis
in order to deduce B(GT) values by combining with (3He,t) measurement.