Nuclear moment studies with spin polarized radioactive beams from fragmentation reaction
Daisuke Kameda
Department of Physics, Tokyo Institute of Technology
Plan of the talk1. Introduction of the nuclear-moment measurement 2. g factor measurements of 17C and 19N3. Summary
Spin and Quantum Structure in Hadrons, Nuclei and Atoms
(SQS04 at TIT)
Nuclear-moments measurement around light mass region
by using the spin-polarized Radio Isotope (RI) beam
H. Ogawa et al., Phys.Rev. C 67 (2003) 064308
µ l, j of the valence orbitalQ effective charge, deformation
The principle of β-NMR experiment
Aβ : Asymmetry factor of β-ray emissionP : Polarization
The principle of production for spin polarized RI beam from fragmentation reaction
p||
Emission angle
Momentum distribution of projectile fragments
The projectile fragment should be selected1, in the momentum distribution2, in the emission angle
= P0
Production of spin polarized RI beamRIKEN Projectile-fragment Separator (RIPS)
RRC
Detector setup to detect the spin polarization of RI
22Ne, 110 MeV/u
Confirmation of the spin polarization
Beam pulsing & β -ray counting
Spin-rotation
Adiabatic Field Rotation Method
17C,T1/2 = 193(13)ms 19N,T1/2=0.27(6) s
Primary Beam Ne, 110 MeV/u Ne, 110 MeV/u
Target Nb, 778 mg/cm2natC, 546 mg/cm2
Bz 370 Gauss 420 Gauss
Aβ P (net) -1.2 ±0.4 % 0.28 ±0.09 %
Emission angle 2.3°～ 5.3° 2.6°～ 6.0°
Momentum Accep. 7.21～7.66 GeV/c 8.18～8.69 GeV/c
Stopper Pt ( at 75 K ) Pt ( at 15 K )
Spin-pol. RI beamMomentum Acceptance17C : 1.00 P0 ± 3 %19N : 1.03 P0 ± 3 %
The β-NMR experiment for 17C
Effective Field Nuclear spin
ω0 − ∆ω
ω0 + ∆ωω0
Adiabatic Fast Passage method
ω0 = γ Β0( γ = µN g /
h )
RF coil
40 msTime
The β-NMR spectrum of 17C
|g (17Cg.s.) |= 0.5054(24)
Spin parity assignment of 17C
I π (17C) = 3/2+
This experimental result
E.K. Warburton and D.J. Millener, Phys. Rev. C39 (1989) 1120
MK MK3
J.P. Dufour, et al., Z. Phys. A 324 (1986) 487
I π =(1/2+, 3/2+, 5/2+)
PSDWBT35% | π(p1/2)-2 ν(d5/2)2(2s1/2)1 > + 31% | π(p1/2)-2 ν(d5/2)3 > + ……
PSDMKSimilar result to PSDWBT
3/2[211]
5/2[202]
1/2[220]
1/2[211]
10
ε 2 : Quad. Deformation parameter
ε 2 ~ 0.95 β 2
17C 19O 21Ne 23Mg
ε2 ∼ 0.4 ε2 ∼ 0.4
Spin parity of isotone N=11
Although I π(15C, 19C)=1/2+ ,
Nilsson diagram in prolate deformation region16C : deformed nucleusβ 2 = 0.93(21)
Recently reported by N. Imai in RIKENPhys. Rev. Lett. In print(2004)
Deformation ?
Further research of 17Cwill be needed.
Ref. NPA193(1972)372 for 21NeNPA140(1970)333 for 23Mg
Deformation parameter (ε2 )
Mag
netic
mom
ent (
n.m
.)
B
A
C
D
A : Bare g factor , κ = 0.08B : Bare g factor, κ = 0.10C : Effective g factor, κ=0.08D : Effective g factor, κ=0.10
Effective g factor for 1d orbitgs = -3.339,gl = -0.0749
The β-NMR experiment for 19N
Experimental Condition• Graphite stopper at room
temperature– This material was used in g-factor
measurement for 17N.
• Pulsing time : 50ms for beam
700ms for β counting
• Beam Intensity : 5 kpps
• β-ray yield : 500 cps
• RF magnetic field : 10.0 [Gauss]
Beam
0 100 200 300 400 500 600 700
Time for β-ray count (ms)
Cou
nts /
2m
s( lo
g s c
a le )
T1/2 = 298 ± 13 ms g = 0.58～0.64 (3.3 σ )
Magnetic moments of odd-mass Nitrogen Isotopes
Conditions for 19N in the calc.• Model Space : p, sd shell
core : 4Hep-shell : 10~11 nucleonssd-shell : 4~5 nucleons
• Bare gp, gn factor
Future perspective
x 10 2
x 10 3
x 10 4
x 10 5
pps
95 MeV/nucleon60 pnA
Beam Intensity for spin-polarized RI Beam
Program code : intensity_34
Target : Nb
Island of Inversion
Summary
• Confirmed Polarization for 17C and 19N produced from fragmentation reaction by using the new spin-flip method (Adiabatic Field Rotation) as
17C : - 1.2 ±0.4 % in Pt stopper at 75 K19N : 0.28 ±0.09 % in Pt stopper at 15 K
• The g factor for 17C and 19Ng.s. by using the b-NMR method as17Cg.s. : |g | = 0.5054 ±0.0024 19Ng.s. : |g | = 0.58 ～ 0.64 (preliminary)
• The assignment of spin parity for 17C : I π (17C) = 3/2+
Indication of the large deformation of 17C
• Anomalous change of the g factor for 19N compared with the shell model predictions
Acknowledgements
K. Asahi, H. Ogawa, H. Miyoshi, K. Shimada, G. Kato, S. Emori,
G. Kijima, T. Suga, K. Ohno, K. Yogo, K. Sakai
Department of Physics, Tokyo Institute of Technology
H. Ueno, A. Yoshimi, H. Watanabe, T. Haseyama, Y. Kobayashi,
W. Sato, K. Yoneda, J. Murata, A. Yoshida, T. Kubo,
and M. Ishihara
The Institute of Physical / Chemical Research, RIKEN
N. Imai
Department of Physics, The University of Tokyo
The time spectrum of β-ray countFitting function :
N exp( -t/τ ) + Const.Result : χ2 = 1.002
T1/2 = 298 ± 13 msS/N = 4.5The β-rays form daughter nuclei, 19 O(T1/2=26.91s), were treated as constant-background noise.
The observed half life is consistent with the value reported by P.L.Reeder in 1991.
Half life of 19N
Time (ms)
This exp.
1. J.P. Dufour, et al,. Z. Phys. A324 (1986) 4872. M. Samuel, et al., PRC37 (1988) 13143. J.P. Dufour, et al., AIP Conf. Proc. (1988) 3444. P.L. Reeder, et al., PRC44 (1991) 14355. Table of isotope 8th edition
1.2.
3.
4.5.
0 100 200 300 400 500 600 700
Time for β-ray count (ms)
Cou
nts /
2m
s( lo
g s c
a le )
Shell model calculations
• Model Space : p, sd shellp-shell : 11 nucleonssd-shell : 4 nucleons
• Interaction : PSDMK, PSDWBT• gp, gn factor : bare
The opposite sign of the off-diagonal M1 matrix element between the spin partner with d-orbital was found inPSDMK(WBP) and PSDWBT
interaction.
