PST05, Nov 14-17, 2005, Tokyo

RIKEN

Production of spin-oriented unstable nuclei via the projectile-fragmentation reaction

H. Ueno @RIKEN

RIKEN

Measurement of & Q moments

Known nuclear moments

ground states

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

RIKEN

Ground states

Excited states (Isomer)

Method vs lifetime

1(fs) 1(ps) 1(ns) 1(μ s) 1(ms) 1(s)

TF

TDPAD

β-NMR

stbl

AB

IPACTDPAC

1(M) 1(H)1(D)

NMR

IPAD, RIGV

ME

CFBLS

onlin

e

offli

ne

RIKENISOL based RIBs

•ISOL based RIBs–target fragmentation, fission, and spallation– extraction –low energies

○ high production rates × slow process (lifetime τ limitation)× limited to chemically active elements (Z limitation)

• ARENAS, Louvain-la-Neuve• ATLAS, Argonne• EXCYT, Catania• HRIBF, Oak Ridge• ISAC, TRIUMF• ISOLDE, CERN• PIAFE, ILL• SPIRAL, GANIL• TRIAC, KEK• TWINSOL, Notre Dame • ……..

Isotope-Separation On Linetarget fragmentatione.g. p+UCx

RIKENFragmentation based RIBs

•Fragmentation based RIBs

–projectile fragmentation–high (intermediate) energies

○ no limitation from τ and Z× large spread of momentum & beam divergence

• RIPS, RIKEN• FRS, GSI• A1900, NSCL• LISE, GANIL

RIKENTechniques of μ & Q measurements for ISOL and PF based RIBs

• Ground states– Tilted-foil– Optical pumping

(Laser)

• Excited states– Coulomb

excitation

• Ground states– Fragmentation

• Excited states– Coulomb

excitation– Fragmentation

ISOL PF

PST05, Nov 14-17, 2005, Tokyo

RIKEN

Ground-state nuclear moments

RIKEN

Mechanism of the spin-polarization in P. F. reaction

target

fragment(spectator)

at the reaction(participant—spectator model)

R

Lspectator = 0 - Lparticipant

after the reaction

Fragment with High p

+L

Fragment with Low p

―L

p

p

participant

Lparticipant= x pR

RIKEN

Behavior of the spin-polarization in the P. F. reaction

Detector

Large-Z target

Near-side trajectory

Detector

Small-Z target

Far-side trajectory

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

1. Spin-polarization can be produced simply by selecting p and Θ of outgoing fragments.

2. Size of polarization is typically 1-5 %.

3. Independent of chemical properties.

4. Fragments can be deeply implanted into the stopper material.

× 11Be, 19C (s1/2 nature)

Properties of the fragment-induced polarization

14,15N→12,13B

Au AlNbNbAu

RIKENβ -NMR

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

A: Asymmetry parameterP: Polarization

(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

Required # of nucleiConventional NMR: ~1020

β-NMR : ~104

High sensitivity → RIB application

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

RIKEN

Optical pumping

1) Production of atomic polarization by laser

2) This polarization is transfered to the nuclear spin via hfi

Experimental setup at ISOLDE

Taken from ISOLDE web site

RIKEN

ISOLDE

31Mg11Be

RIKENRecent ground-state μ &Q-measurements of the unstable nuclei

• RIKEN – Discovery of spin-polarization in PF K.Asahi et al., PLB 251, 499 (1990)– 10 μ –moments & 5 Q–moments in the neutron-rich p-shell Osaka Gr. & TITech Gr.– μ [30, 32Al] H. Ueno et al., PLB 615, 186 (2005)– Q [31, 32 Al] (TITech Gr.)

• GANIL– μ [ 32Cl] W.F. Rogers et al., PRC 62, 044312 (2000)– 27Na, 31Al polarization D. Borremans et al., PRC 66, 054601 (2002)– μ [ 31Al] D. Borremans et al., PLB 537, 45 (2002)

• MSU– Spin-polarized RIBs @MSU P.F. Mantica et al., PRC 55, 2501 (1997) – 37K polarization in single-proton pickup reaction @E=150AMeV

D.E. Groh et al., PRL 23, 202502 (2003)• GSI

– 37K polarization @E=500AMeV 　　 M. Schaefer et al., PRC 57 2205 (1998)

• ISOLDE– μ &Q [ 11Li ] E.Arnold et al. PLB 281, 16 (1992)– μ [ 11Be ] W. Geithner et al., PRL 83, 3792 (1999)– μ [ 31Mg] G. Neyens et al., Phys.Rev.Lett. 94, 022501 (2005)

Fragment induced spin-polarization + β-NMR method

Optical pumping + β-NMR method

PST05, Nov 14-17, 2005, Tokyo

RIKENIsomer-state (τ ∼ μs) nuclear moments

γ -ray detectors

beam

W(θ) W(θ + • t )

target

spin-alignment produced in the Coulomb excitation reaction

B0 field

stopper material

gμ NB0

ℏ

TDPAD

RIKEN

Spin-alignment in the PF reaction

K. Asahi et al., Phys. Rev. C 43, 456 (1991)

• Spin-alignment is produced as a function of ejectile momentum

46Ti(E=500 AMeV) + Be→ 43Sc

W.-D. Schmidt-Ott et al., Z.Phys. A350, 215 (1994)

RIKEN

Isomer ratio in the PF reaction

F: fraction of the isomeric states

F = Nisomer

Ntotal

B.M. Young et al., Phys. Lett. B 311, 22 (1993)

PF is better way to produce spin-aligned RIBs

RIKEN

TDPAD exp. at GANIL

G. Georgiev et al., Eur. Phys. J. A 20, 93-94 (2004)

76Ge(E=61.4 AMeV)+Be→ 67mNi (t1/2=13.3μ s), 69mCu(t1/2=0.35μ s),

Spin-alignment produced in PF reaction

PST05, Nov 14-17, 2005, Tokyo

RIKENShort-lived excited state (τ ∼ ps)

γ -ray detectors

ferromagnet

beam

W(θ) W(θ+θTF)

1st target

Transient-field method

RIKEN

Low erengies• LBL

– First g factor measurement with RI beams (76Kr) −K.-H. Speidel et al., Eur. Phys. J. A 25, s01, 203{304 (2005)

• ISOLDE– g-Factor measurements of 132, 134, 136 Te

Intermediate energies (PF reaction)• RIKEN

– BTF strength @v ～ Zv0 H. Ueno et al., Hyperfine Int. 136/137, 2 (2001)

A. Yoshimi et al., Nucl. Pys. A 738, 519 (2004)

• MSU– v/Zv0 distribution→ discussion on the BTF strengths @v ≥Zv0

A.E. Stuchbery PRC69, 064311 (2004)

– g factor measurements of − 38, 40S produced in the PF reactionsA.D. Davis, A.E. Stuchbery, P.F. Mantica et al., DNP2005

Transient Filed: τ ～ ps

Status of μ (21+) measurements for unstable nucle

i

RIKEN1st TF expeiment with RIB

MgGdTa

Mg

Beam

N. Benczer-Koller et al., Eur. Phys. J. A 25, s1.203-s1.304 (2005)

1st RIB-expeiment

76Kr(T1/2 = 14.8 h) @ LBL

I = 106 cps x 5 days74Se(α, 2n)76Kr @E=38MeV

Magnetic Moments of Coulomb Excited 21+

States for Radioactive Beams of 132, 134, 136Te Isotopes at REX-ISOLDE

RIKEN

TF exp. at MSU

                                      A User's Perspective

The Transient-Field Technique in a New RegimeAndrew Stuchbery, Australian

High energy RIBs (PF reaction)

38S and 40Sthe first 2+ states (τ∼ps)

Au (355 mg/cm2)

Fe (110 mg/cm2)38,40S (E=40 AMeV)

38,40S*

RIKENBTF at v > Zv0

5 10 15 20

1

2

3

high-velocity region: vion> Zv0

N.K.B. Shu et al., PRC21, 1828 (1980)

BTF=4π Z·v0/vion·μ BNp

G. Hagelberg et al., Z. Phys. D17, 17 (1990)

VSE (eproj e⇄ GdQfree)

24Mg+Gd

Ion velocity v/vion

BT

F (

kT

)

0

low-velocity region: vion≲ Zv0

Eberhardt et al.Hyp. Int. 3, 195 (1977) Empirical BTF=a·Z·vion/v0

(a Fe =12, a Gd =17)

?? F. Hagelberg et al., PRC48, 2230 (1993)

VSE (eionic-shell e⇄ GdLocalized)

BTF=p1s x q1s

p1s prediction

RIKEN

• 6” NaI x 4• Target Au+Gd

Target ladder cooled toT∼100K• Coil (Bext = 300 Gauss)

Bext Up & Down in every 15 sec.• 30 plastic scintillators for particle coincidence

targetladder

liq.N2

container

RIKEN-setup for TF experiments

RIKEN

Comparison with the systematic

K.-H. Speidel et al.PLB324(1994)130

BTF=a Z vion/v0

a=12 (Fe)a=17 (Gd)

Stopping power > 4.5 MeV/μm

BTF=1.2(2) kT

Mg (Gd)

BTF values of 28Si and 24Mg

deviation but substantial magnitude

PST05, Nov 14-17, 2005, Tokyo

RIKEN

Recent measurement of ground-state nuclear moments at RIKEN

RIKEN

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

RIPS

K=540 RIKEN Ring Cyclotron

RIKEN

NMR apparatus

β -NMR:w(θ)=1+APcosθ

(U/D)off = (1+AP)/(1-AP)(U/D)on = (1- AP)/(1+AP)

NMR technique: the AFP method

e-e-e-e-

e- e-e-e-e-

e-

RIKEN

• g-Factors measured at RIKEN– Boron isotopes : 14B, 15B, 17B– Carbon isotopes : 9C, 15C, 17C– Nitrogen isotopes : 17N, 18N, 19N– Oxygen isotopes : 13O

• Q-moments measured at RIKEN– Boron isotopes : 14B, 15B, 17B– Nitrogen isotopes : 18N– Oxygen isotopes : 13O

Study of the p-shell nuclei through their nuclear moments

TITech / RIKEN

Osaka / RIKEN

Spin-parity assignment

Reduction of E2 effective charges

RIKEN

I = 0

g-factor known

Recent μ -measurements in the sd shell

Island of inversion

N=20

GANILISOLDE

RIKEN

RIKEN

Neutron-rich Al isotopes (theory)

E. Caurier et al., PRC58(1998)2033 Y. Utsuno et al., PRC 64(2001)011301(R)

33Al31Al 32Al 33Al 34Al

• 33Al is turning point of the inversion between 0p-0h and 2p-2h configurations along N=20

• decreases from 31Al(30Al)→33Al• E0p0h-E2p2h > 0 for Al isotopes, but similar to Mg, Na, Ne

Al: near the border line of Island of Inversion

RIKENμ -moments of 30Al & 32Al

• The result provides a promising prospect that substantial polarizations are obtained for the other sd-shell nuclei

H. Ueno et al., PL B615, 186 (2005)

RIKEN

Comparison with shell model prediction

In both 30Al and 32Al cases, no disagreement is observed between μ exp and μ SM(USD)

Amplitude of intruder configurations is larger for 32Al ?

H. Ueno et al., Phys. Lett. B 615, 186-192 (2005)

RIKEN

Precisionmeasurement

Wide-rangescan

Q [32Al] (preliminary)

RIKEN

Q [31Al] (preliminary)

Wide-rangescan

Precisionmeasurement

3.5σ statistics

RIKENSummary

• Grond-state nuclear moments have been measured in RIB facilities.• Measurements for the excited states have started.

at RIKEN

• Nuclear moments have been measured in the p-shell region by means of the β-NMR method + fragment-induced polarization.– μ-moments enhancement of (sd)2+, J π assignment– Q-moments reduction of the E2 effective charges

• In the sd-shell μ [30,32 Al] and Q [31,32 Al] have been measured.– 40Ar→30Al (10-nucleon removal) was spin-polarized: P ～ 1%– Next: 33, 35Si, Q(33Al), μ (34,35Al), 33-37P, 33Mg

RIKENCollaboration

K. Asahi, M. Takemura, G. KijimaK. Shimada, D. Nagae, M. Uchida, T. Ar

aiH. Miyoshi, G. Kato, K. Emori, M. TsukuiTokyo Institute of Technology

H. Ueno, D. Kameda, A. Yoshimi, T. Haseyama, Y. Kobayashi, H. Sato, H. Okuno, N. Aoi, K. Yoneda, N.Imai, N. Fukunishi, A. Yoshida, T. Kubo, M. Ishihara RIKEN

T. KawamuraRikkyo Univ.

H. OgawaAIST

H. WatanabeAustralian National Univ.

H. Izumi, W. Sato, T. ShimodaOsaka University

H. Miyatake, Y.X. WatanabeKEK

W.-D. Schmidt-OttUniversitaet Goettingen

G. Neyens, S. TeughelsLeuven