H. Ueno, A. Yoshimi, T. Nagatomo, T. Sugimoto, Y. Kobayashi H. Watanabe, M. Ishihara

Tokyo Institute of Technology K. Asahi, D. Nagae, M. Takemura, K. Shimada, K. Takase, T. Inoue, G. Kijima, T. Arai, S. Suda, S. Kagami, N. Hatakeyama

Rikkyo University J. Murata, H. Kawamura

Production of spin-polarized radioactive-ion beams via the projectile fragmentation reaction

D. Kameda RIKEN Nishina Center

XIIth International Workshop on Polarized Sources, Targets & PolarimetryPSTP2007, Sept. 10-15 at Brookhaven National Laboratory

Outline

1. What is Projectile Fragmentation reaction?2. Production of spin-polarized fragments in

PF reaction– Mechanism– Feature of polarization phenomena in PF

reaction3. Application of polarized Radioactive-Ion

(RI) beams– Nuclear moment measurements in RIKEN

4. Summary

PSTP2007 Sept. 10-15 at BNL

Projectile Fragmentation Reaction

0.4v/c

Powerful source of producing RI beams: LISE/GANIL, A1900/NSCL, FRS/RFS, RIPS/RIKEN, …

Geometrical overlap is the essential part

Projectile

Target

Overlap

Typical velocity of projectile nucleus:

Fermi velocity of nucleus:

0.26F /cv

PSTP2007 Sept. 10-15 at BNL

target

projectile fragment

projectile

J. Gosset et al., Phys. Rev. C16 (1977) 629.

sec. 10 23t

NNttSAP targproj) (

Thickness of the overlap region[fm-2 ]

A

j

AA

kkkjj

A

j

AA

kkkjj

A

j

AA

kkkjj

AA

kk

A

jj

prprPRR

prRprR

prprL

PPppP

spec.parti.parti.spec.parti.

spec.spec.

parti.parti.

proj.

spec.parti.proj.

)(

)()(

0

L LF = 0

Fragment-induced spin polarization

target

projectilefragment

RP

-P

L=-RxP

Position vector of the participant portion

Sum of the lost Fermi momenta

Angular momentum left in the fragment part

K.Asahi et al., PLB 251, 499 (1990)

kinematical model:

Participant

Spectator

Rparti

rj parti

Rspec.

rkspec.

Projectile rest flame:

Pspec.0

Goldhaber distribution:

PSTP2007 Sept. 10-15 at BNL

.0 ,0 If F LL

First observation

K. Asahi et. al., Phys. Lett. B 251 (1990) 488

PSTP2007 Sept. 10-15 at BNL

15N+Au 15N+41Nb 15N+Nb 15N+13Al14N+79Au

12B 13B 13B 13B 13B

Dependence of polarization on Targets

DetectorDetector

Large-Z target Small-Z target

near-sidetrajectory

far-sidetrajectory

H. Okuno et al., PL B335,29 (1994)

PSTP2007 Sept. 10-15 at BNL

Projectile-fragmentation induced polarization

Advantages on applications :• Fastest method• Chemical independent

ground states excited states

Data are taken from“Table of nuclear magnetic dipole and electric quadrupole moments”, N.J. Stone, 2001

The polarization is typically 1~10 %, but strongly depends on

1) the emission angle and outgoing momentum of the fragments

2) target-Z numbers ( competition of far-side and near-side trajectories)

3) removed-nucleon numbers

PSTP2007 Sept. 10-15 at BNL

• g-Factors measured at RIKEN– Boron isotopes : 14B, 15B, 17B– Carbon isotopes : 9C, 15C, 17C– Nitrogen isotopes : 17N, 18N, 19N– Oxygen isotopes : 13O– Fluorine isotopes : 21F– Aluminum isotopes : 23Al, 30Al, 32Al

• Q-moments measured at RIKEN– Boron isotopes : 14B, 15B, 17B– Nitrogen isotopes : 18N– Oxygen isotopes : 13O– Magnesium isotopes : 23Mg– Aluminum isotopes : 31Al, 32Al

Study of the p- and sd- shell nuclei through their nuclear moments

TITech / RIKEN

Osaka / RIKEN

Spin-parity assignment

Reduction of E2 effective charges

Effect of neutron excess on the magnetic moment

Study on the island of inversion

PSTP2007 Sept. 10-15 at BNL

I = 0

g-factor known

Neutron-rich Al isotopes- northern-side of the island of inversion- good examples

N=20

μ or Q known (a few years ago)

PSTP2007 Sept. 10-15 at BNL

Production of spin-polarized RI beam with RIKEN Projectile fragment Separator (RIPS)

RIPS

K=540 RIKEN Ring Cyclotron Isotope separationmagnetic analysis (A/Z)

+momentum-loss analysis (A2.5/Z1.5)

Production of spin polarizationscattering-angle selection

+momentum analysis

RIPS

0

0.5

1

-6 -4 -2 0 2 4 6 8

30Al

(p-p0)/p0 (%)

Yie

ld (

a.

u.)

0

0.5

1

-7 -5 -3 -1 1 3 5 7

32Al

(p-p0)/p0 (%)

40ArE=95AMeV

93Nb targett=150, 450μm

θLab[AAl]≧ 1.3°

PSTP2007 Sept. 10-15 at BNL

β-NMR apparatus

(1+AP)(1-AP)

(U/D)RFoff =e- e-e-

e-

e-e-

(U/D)RFoff =(1-AP)(1+AP

)

e-e-e-e-

e- e-

RF coil

NMR

β-ray angular distribution:W(θ)=1+APcosθ

A: Asymmetry parameterP: Polarization

β-NMR method: K. Sugimoto et al., J. Phys. Soc. Japan 21 (1966) 213.

q (3cos∝ 2θc-1) = 0

c-axis

α-Al2O3 (sapphire) single crystal

θc-axis = 55°

PSTP2007 Sept. 10-15 at BNL

μ [[30-30-

3232Al]Al]

|g[31Al]|=1.529(3) |g[32Al]|=1.951(5)mb 5.4~ eQ mb eQ 75.0~

|μ (30AlGS;3+)|=3.010(7)

error & correction

Δν /ν 0 (fitting) ～ 0.21 (%)Δν /ν 0 (F.G. control) ～ 0.014 (%)ΔB0/B0 ～ 0.06 (%)Δν Q/ν 0 ～ 0.09 (%)chemical shift < 0.00002 (%)

30, 32Al: H. Ueno et al., PLB 615, 186 (2005)

30Al 31Al 32Al

31Al: D. Borremans et al., PLB 537, 45 (2002)

PSTP2007 Sept. 10-15 at BNL

2 /Q e qQ

32( Al)Q

Q [31Al, 32Al] measurements

Q[31Al] = 104(9) mb(preliminary)

Q[32Al] = 24(2) mb

D. Kameda et al., to be published

νQ (kHz)

(U/D

) R

F-o

n /

(U/D

) RF

-off

D. Kameda et al., Phys. Lett. B 647, 93 (2007)

PSTP2007 Sept. 10-15 at BNL

Systematic comparison with shell model calculations

(ep,en)=(1.3,0.5)

|Q| m

omen

t (e

mb)

| m

omen

t (

N)

Present results

The conventional shell model calculation with the full sd model space well reproduce Q(32Al), while the sd model overestimates Q(31Al) by 45%. The reported Q-moments of 26-28Al are consistent with the sd shell model.

The -moments are well reproduced by the conventional sd-shell model.

The Monte Carlo shell model calculations predict that the Q-moments of 33Al and 34Al are significantly enhanced by the mixing of the pf-intruder configurations.

Experimentally, there is no evidence for the pf-intruder structure in the ground states of N=18-19 Al isotopes.

J 5+ 5/2+ 3+ 5/2+ 5/2+ 5/2+1+3+

PSTP2007 Sept. 10-15 at BNL

SummaryThe polarization is typically 1~10%, which strongly

depends on 1) emission angle and outgoing momentum of the

fragment2) target-Z numbers ( competition of far-side and near-

side trajectories)3) removed-nucleon numbers in the fragmentationFrom recent measurements 1) Sufficient polarization induced by A~10

fragmentations2) The nuclear moments provide useful information

about nuclear structure far from the stability, island of inversion. Future:

RI beam Factory in RIKEN

PSTP2007 Sept. 10-15 at BNL

Thank you.

Isospin-dependent effective chrages

Polarization charges:

V1/V0MeVMeV=

j orbit with Woods-saxon potential

Nuclear structure Vol. IIAage Bohr, Ben R. Mottelson

The overestimation of Q(31Al) is reduced. In the other Al isotopes, the consistency between experiment and theory is preserved, except for the case of 28Al.

Isopin-dep. (ep, en)Further analysis is now in progress.

PSTP2007 Sept. 10-15 at BNL

Measurements of the Q moments

124

13

2

1cos3 2axisc

22

II

IImQqeHQ

)12(8

)1cos3)(12(3 axisc2

1

II

mQLmm

h

qQeQ

2

RF sweeps for One Q-moment data point

eqQZeeman

63ms

31AlIπ=5/2+

α-Al2O3

ν L∼7MHz∆ν [eqQ]∼100kHz

α-Al2O3 (sapphire) single crystal

PSTP2007 Sept. 10-15 at BNL