RIKEN
Production of spin-oriented unstable nuclei via
the projectile-fragmentation reaction
H. Ueno @RIKEN
PST05, Nov 14-17, 2005, Tokyo
Measurement of m & Q moments
RIKEN
Known nuclear moments
ground states
excited states
Data are taken from
“Table of nuclear magnetic dipole
and electric quadrupole moments”,
N.J. Stone, 2001
Method vs lifetime
1(fs)
1(ps)
1(ns)
RIKEN
1(μs)
1(ms)
1(s)
1(M) 1(H) 1(D)
stbl
TF
online
Excited states
(Isomer)
IPAD, RIGV
TDPAD
AB
Ground states
β-NMR
IPAC
offline
TDPAC
CFBLS
NMR
ME
ISOL based RIBs
RIKEN
•ISOL based RIBs
Isotope-Separation On Line
target fragmentation
e.g. p+UCx
–target fragmentation,
fission, and spallation
– extraction
–low energies
○ high production rates
× slow process (lifetime τ
limitation)
× limited to chemically active
elements (Z limitation)
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ARENAS, Louvain-la-Neuve
ATLAS, Argonne
EXCYT, Catania
HRIBF, Oak Ridge
ISAC, TRIUMF
ISOLDE, CERN
PIAFE, ILL
SPIRAL, GANIL
TRIAC, KEK
TWINSOL, Notre Dame
……..
Fragmentation based RIBs
•Fragmentation based
RIBs
–projectile fragmentation
–high (intermediate)
energies
○ no limitation from τ and Z
× large spread of momentum &
beam divergence
RIKEN
•
•
•
•
RIPS, RIKEN
FRS, GSI
A1900, NSCL
LISE, GANIL
Techniques of μ & Q measurements for ISOL and PF based RIBs
ISOL
• Ground states
– Tilted-foil
– Optical pumping
(Laser)
• Excited states
– Coulomb excitation
PF
• Ground states
– Fragmentation
• Excited states
– Coulomb excitation
– Fragmentation
RIKEN
RIKEN
Ground-state nuclear moments
PST05, Nov 14-17, 2005, Tokyo
Mechanism of the spin-polarization in P. F. reaction
at the reaction
(participant—spectator model)
after the reaction
Lspectator = 0 - Lparticipant
+L
fragment
(spectator)
p
R
Fragment with High p
p
participant
target
―L
Fragment with Low p
Lparticipant=
R
xp
RIKEN
Behavior of the spin-polarization in the P. F. reaction
Far-side trajectory
Near-side trajectory
Detector
Large-Z target
Detector
Properties of the fragmentinduced polarization
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
Small-Z target
14,15N→12,13B
Au
Au
Nb
Nb
Al
RIKEN
(s1/2 nature)
H. Okuno et al., PL B335,29 (1994)
β-NMR
RIKEN
Required # of nuclei
Conventional NMR: ~1020
β-NMR
: ~104
β-ray angular distribution:
W(θ)=1+APcosθ
A: Asymmetry parameter
P: Polarization
High sensitivity → RIB application
(U/D)RFoff = (1+AP)
(1-AP)
e-
(U/D)RFoff = (1-AP)
(1+AP)
e- e- e-
e-
e-
NMR
e-
e-
e - e- e - e-
RF coil
β-NMR method: K. Sugimoto et al., J. Phys. Soc. Japan 21 (1966) 213.
Optical pumping
RIKEN
Experimental setup at ISOLDE
1)
2)
Production of atomic polarization
by laser
This polarization is transfered to
the nuclear spin via hfi
Taken from ISOLDE web site
ISOLDE
RIKEN
31Mg
11Be
Recent ground-state μ&Q-measurements of the unstable nuclei
Fragment induced spin-polarization + β-NMR method
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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.
30,
32
– μ[
Al]
H. Ueno et al., PLB 615, 186 (2005)
31,
32
– Q[
Al] (TITech Gr.)
GANIL
– μ [ 32Cl]
W.F. Rogers et al., PRC 62, 044312 (2000)
27
31
–
Na, Al polarization
D. Borremans et al., PRC 66, 054601 (2002)
31
– μ [ Al]
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
GSI
–
D.E. Groh et al., PRL 23, 202502 (2003)
37K
polarization @E=500AMeV
M. Schaefer et al., PRC 57 2205 (1998)
Optical pumping + β-NMR method
•
ISOLDE
– μ &Q [ 11Li ]
– μ [ 11Be ]
– μ [ 31Mg]
E.Arnold et al. PLB 281, 16 (1992)
W. Geithner et al., PRL 83, 3792 (1999)
G. Neyens et al., Phys.Rev.Lett. 94, 022501 (2005)
RIKEN
Isomer-state (τ ∼ μs) nuclear moments
RIKEN
TDPAD
γ-ray detectors
B0 field
target
beam
W(θ)
W(θ + gμNB0 • t )
ℏ
stopper material
spin-alignment produced
in the Coulomb excitation
reaction
PST05, Nov 14-17, 2005, Tokyo
Spin-alignment in the PF reaction
RIKEN
• Spin-alignment is produced as a function of
ejectile momentum
46Ti(E=500
AMeV) + Be
→ 43Sc
K. Asahi et al., Phys. Rev. C 43, 456 (1991)
W.-D. Schmidt-Ott et al., Z.Phys. A350, 215 (1994)
Isomer ratio in the PF reaction
RIKEN
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
TDPAD exp. at GANIL
RIKEN
Spin-alignment produced in PF reaction
76Ge(E=61.4
AMeV)+Be
→ 67mNi (t1/2=13.3μs),
69mCu(t =0.35μs),
1/2
G. Georgiev et al., Eur. Phys. J. A 20, 93-94 (2004)
Short-lived excited state (τ ∼ ps)
RIKEN
Transient-field method
ferromagnet
1st target
beam
γ-ray detectors
W(θ)
W(θ+θTF)
PST05, Nov 14-17, 2005, Tokyo
Status of μ(21+) measurements for unstable nuclei
Transient Filed: τ～ps
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 reactions
A.D. Davis, A.E. Stuchbery, P.F. Mantica et al., DNP2005
RIKEN
1st TF expeiment with RIB
RIKEN
1st RIB-expeiment
76Kr(T
Mg
Beam
1/2 =
14.8 h) @ LBL
Mg Gd Ta
I = 106 cps x 5 days
74Se(α, 2n)76Kr @E=38MeV
N. Benczer-Koller et al., Eur. Phys. J. A 25, s1.203-s1.304 (2005)
Magnetic Moments of Coulomb Excited 21+
States for Radioactive Beams of 132, 134, 136Te
Isotopes at REX-ISOLDE
TF exp. at MSU
RIKEN
High energy RIBs (PF reaction)
A User's Perspective
Au (355
mg/cm2)
38,40S*
The Transient-Field Technique in a New Regime
Andrew Stuchbery, Australian
38,40S
38S and 40S
the first 2+ states (τ∼ps)
Fe (110 mg/cm2)
(E=40 AMeV)
BTF at v > Zv0
RIKEN
BTF (kT)
low-velocity region: vion≲ Zv0
3
Eberhardt et al.Hyp. Int. 3, 195 (1977)
Empirical BTF=a·Z·vion/v0
24Mg+Gd
(a Fe =12, a Gd =17)
high-velocity region: vion> Zv0
2
N.K.B. Shu et al., PRC21, 1828 (1980)
BTF=4πZ·v0/vion·μBNp
?
1
G. Hagelberg et al., Z. Phys. D17, 17 (1990)
VSE (eproj⇄eGdQfree)
F. Hagelberg et al., PRC48, 2230 (1993)
VSE (eionic-shell⇄eGdLocalized)
p1s prediction
0
5
10
15
Ion velocity v/vion
20
BTF=p1s x q1s
RIKEN-setup for TF experiments
• 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
RIKEN
liq.N2
container
target
ladder
Comparison with the systematic
RIKEN
BTF values of 28Si and 24Mg
Mg (Gd)
BTF=a Z vion/v0
a=12 (Fe)
a=17 (Gd)
BTF=1.2(2) kT
deviation but substantial magnitude
Stopping power > 4.5 MeV/μm
K.-H. Speidel et al.
PLB324(1994)130
RIKEN
Recent measurement of ground-state
nuclear moments at RIKEN
PST05, Nov 14-17, 2005, Tokyo
Production of spin-polarized RI beam with
RIKEN Projectile fragment Separator (RIPS)
RIPS
K=540 RIKEN Ring Cyclotron
RIKEN
NMR apparatus
RIKEN
β-NMR:
w(θ)=1+APcosθ
(U/D)off = (1+AP)/(1-AP)
(U/D)on = (1- AP)/(1+AP)
e-e ee-
e-
e-
- e-e-ee
- -
NMR technique:
the AFP method
Study of the p-shell nuclei through their nuclear moments
• g-Factors measured at RIKEN
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–
Boron isotopes
Carbon isotopes
Nitrogen isotopes
Oxygen isotopes
: 14B, 15B, 17B
: 9C, 15C, 17C
: 17N, 18N, 19N
: 13O
RIKEN
TITech / RIKEN
Osaka / RIKEN
Spin-parity
assignment
• Q-moments measured at RIKEN
– Boron isotopes
– Nitrogen isotopes
– Oxygen isotopes
: 14B, 15B, 17B
: 18N
: 13O
Reduction of E2
effective charges
Recent μ-measurements in the sd shell
I=0
RIKEN
N=20
g-factor known
RIKEN
GANIL
ISOLDE
Island of inversion
Neutron-rich Al isotopes (theory)
33Al
Y. Utsuno et al., PRC 64(2001)011301(R)
•
is turning point of the
inversion between 0p-0h and 2p2h configurations along N=20
33Al
RIKEN
31Al
32Al
33Al
34Al
E. Caurier et al., PRC58(1998)2033
• 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
μ-moments of 30Al & 32Al
RIKEN
• 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)
Comparison with shell model prediction
RIKEN
Amplitude of intruder configurations is larger for 32Al ?
In both 30Al and 32Al cases, no disagreement is
observed between μexp and μSM(USD)
H. Ueno et al., Phys. Lett. B 615, 186-192 (2005)
Q [32Al] (preliminary)
Wide-range
scan
Precision
measurement
RIKEN
Q [31Al] (preliminary)
RIKEN
Wide-range
scan
Precision
measurement
3.5σ
statistics
Summary
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Grond-state nuclear moments have been measured in RIB facilities.
Measurements for the excited states have started.
at RIKEN
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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+, Jπ 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
RIKEN
Collaboration
RIKEN
K. Asahi, M. Takemura, G. Kijima
K. Shimada, D. Nagae, M. Uchida, T.
Arai
H. Miyoshi, G. Kato, K. Emori, M.
Tsukui
H. Watanabe
Tokyo Institute of Technology
Osaka University
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
H. Miyatake, Y.X. Watanabe
RIKEN
T. Kawamura
Rikkyo Univ.
H. Ogawa
AIST
Australian National Univ.
H. Izumi, W. Sato, T. Shimoda
KEK
W.-D. Schmidt-Ott
Universitaet Goettingen
G. Neyens, S. Teughels
Leuven