nupecc – bucharest – oct. 2007 nuclear spectroscopy at the department of nuclear physics –...

NUPECC – Bucharest – Oct. 2007

NUCLEAR SPECTROSCOPY AT THE DEPARTMENT OF NUCLEAR PHYSICS – TANDEM

BUCHAREST


• 1974 – 7 MV• 2007 – 9 MV

• 3 ion sources: - duoplasmatron (HVEC) - sputtering (NEC) - AMS ultraclean (sputtering)

• beams: p to Au (no noble gases)

(~ 3600 hours/year)

• foil and gas stripping

• 7 beamlinesSince 2006 Refurbishing process:

- Vacuum equipment √- Electrical power supplies √- Voltage charging system (Pelletron) √ - Sputtering ion source √ - Automatic control of ion optics & diagnosis- Beam pulsing system


Experimental Nuclear Spectroscopy program at the Bucharest Tandem accelerator

• Medium / high-spin γ-ray spectroscopy with heavy-ion fusion-evaporation reactions

( check of structure models: shell model, IB(F)M )

• Low-spin γ-ray spectroscopy with p/α beams (quasicomplete level schemes, DSAM lifetimes)

• Beta decay studies ( tests of critical point symmetries )

• Reactions of astrophysical interest [ (α,γ) ]


Heavy-ion fusion-evaporation reactions


139CeLow spins – quasicomplete low-spin scheme 139La(p,nγ) reaction , Ep = 5-6 MeV

High spins – 130Te(12C,3nγ), 50 MeV

D.Bucurescu et al, Eur. Phys. J. A27 (2006) 301


2.22/4 R

GeZn 6464 ,

E(5): critical point of transition

U(5) (sph. vibr.) to O(6)(γ -soft)

(2.00, -1.0) (2.50,-2.0)

39.1S

C.Mihai et al, Phys. Rev. C75(2007)044302

gE

EEEES

2

2334

50 Sn

48 Cd

R4/2

S4

-

46 Pd

- -

- -

(2.11) -

44 Ru

- -

(2.29) -

(2.24) -

(2.14) -

42 Mo

- -

(2.34) -

2.23 -

2.11 -

40 Zr

- -

(2.85) -

2.56 -

2.34 -0.26

2.22 (-0.42)

2.02 -

38 Sr

- -

- -

(2.81) -

2.54 (-0.43)

2.32 -0.35

2.23 (-0.07)

2.07 -

36 Kr

- -

(1.86) -

2.22 -

2.44 (-0.68)

2.46 (-0.72)

2.33 -0.28

2.34 (-0.37)

2.38 -

34 Se

- -

(2.27) -

2.16 -

1.9 -

2.15 -0.61

2.38 -0.24

2.45 0.34

2.55 0.45

2.65 0.4

32 Ge

- -

(2.27) (-1.78)

2.27 (-0.59)

2.23 -0.24

2.07 -0.37

2.07 -0.73

2.46 (0.12)

2.5 (0.08)

2.54 (0.3)

(2.64) -

30 Zn

2.18 -

2.29 -0.23

2.33 -1.45

2.36 (-0.74)

(2.24) (-1.09)

2.02 (-1.63)

- -

(1.92) -

(2.16) -

- -

Z

28 Ni

28 30 32 34 36 38 40 42 44 46 48 50

N

ZnGapnCFe 64/641254 ),(

12C: 36 MeV, 3 pnA, t=250 s, 54Fe: 13mg/cm2, 99%

3HPGe detectors ~30% eff.

E(5) Candidates


)20;2(

)20;2(

13

23

EB

EB

64Zn 66Zn 68Zn

1054 0.53 -

<0.66 210(75) >430

E(5)

)20;2(

)20;2(

12

22

EB

EB 0

0

0.12

32


50 100 150 200 250 300 350 4000

1000

2000

3000

0

1000

2000

3000

4000

*

**

300

184

93

Foil #2E = 5.994 MeV

Co

un

ts

E (keV)

*

*

*

*

63Cu(,)67Ga

Cu(,)Ga, E = 6.3 MeV

5 foil (~ 1.0 mg/cm2) - stack

300

184

93

Foil #4E = 4.923 MeV

5 6 7 8 9 10 1110-10

10-9

10-8

10-7

63Cu()67Ga

Yie

ld

E (MeV)

present measurements M.S. Basunia (PRC 75/2007) GNASH-FKK (OM pot.: Avrigeanu) NONSMOKER

2 3 4 5 6 7 8 9 1010-4

10-3

10-2

10-1

100

101

63Cu()67Ga

(,)

(mb

)

E (MeV)

present Basunia et al. GNASH-FKK NONSMOKER


Multi-purpose gamma-miniarray

3 new HPGe (pop-top) (eff.: 2 x 60%; 1 x 30%) + 3 older ~30% + clover (to come) + …

Under installation:2007-2008: 6 Osiris detectors with anticompton shields

Under execution: Plunger device (“Kőln”)


European Collaborations

• Collaborations with different Labs and Universities

(bilateral and governmental collaboration agreements)

• EURONS (AGATA, EXOCHAP, ISIBHI, EWON)

• EURISOL (fission target; safety&radioprotection;

physics&instrumentation)

• FAIR (NUSTAR)

Padova – Legnaro ; GANIL


Collaboration with Lab. Naz. Legnaro 1) The heaviest even-even N=Z and odd-A N=Z+1

nuclei ( A > 80, 100Sn) Fusion-evaporation reactions.

GASP (γ); ISIS (charged particles); N-ring (n)


• T=0 np pairing in N=Z nuclei (?)

• Evolution of collectivity (along N=Z line)

• Critical point symmetry (X(5) at N ≈ Z ≈ 38,40 ?)

• Spin-gap isomers (close to N=Z=50)

• Shell model description (test current resid. inter.)

• T=0 np pairing in N=Z nuclei (?)


J=0 T=1

J=1…2j T=0

Signature of T=0 np pairing ?Delayed Alignment in N=Z Nuclei

N.Marginean et al, Phys. Rev. C63 (2001) 031303(R); C65(2002)051303(R)


2) Spectroscopy of neutron-rich nuclei

Multi-fragmentation reactions. CLARA (γ); PRISMA (product nuclei)

• 58Cr: yrast line – E(5) symmetry vs shell model

• Neutron-rich Fe nuclei (A = 61 to 66) – test of “fpg” residual interaction in large-scale SM calculations

• Spherical n-rich 89Rb, 92,93Y – test of “gwbxg” residual interaction


D.Bucurescu et al, Phys. Rev. C, in press

89Rb


3) High-spin states of light nuclei (sd shell)

• Tests of large scale shell model calculations (sdfp residual interaction)• Isospin symmetry

> Large MED between ~pure sp (f7/2) analog states;

> Different E1 decay pattern of analog pos. parity states:

importance of multipole Coulomb & electromagneticspin-orbit terms.

F. Della Vedova et al, Eur. Phys. J. A27 (2006) 301


3) Nuclear moment measurements – ns-μs isomers

- g-factors - TDPAD method, H- g-factors - TDPAD method, Hextext; ; - electric quadrupole moments (Qelectric quadrupole moments (Qs) – Electric Field Gradients) – Electric Field Gradients

(noncubic crystalline lattices)(noncubic crystalline lattices)

• High K isomers: Iπ=14+ in 176W : well defined K=14, deformed pure 4-qp state;

anomalous decay due to K mixing in lower K states.

• Qs for normal and intruder states in 192,194Pb (11-, 12+): shape mixing

• Qs for magnetic rotational bandhead in 193Pb• Qs for magnetic rotational bandhead in 193Pb


Qs 29/2- magnetic rotational bandhead in 193Pb

|Qs | (exp) Qs(PQTAC) β2

29/2 (1i13/21) ( 1i13/2 1h9/2) 2.84 (26) eb –2.8 eb – 0.12

21/2 (1i13/22 ) 3p1/2 0.22(2) eb +0.26 eb +0.02

33/2 (1i13/23) 0.45(4) eb +0.46 eb +0.03

EFG Hg crystalline lattice T=170 K

M. Ionescu-Bujor et al., Phys. Rev. C 70, 034305 (2004) and to be published

21/2- E=184 keV

29/2-

E=213 keV

T1/2 = 9 ns T1/2 = 22 ns T1/2 = 180 ns

33/2+ E=532 keV


On proton-rich side: Discovery of Doubly Magic 48Ni

Two-Proton Radioactivity of 45Fe

First Observation of 55, 56Zn

First observation of 54Zn and its decay by two-

proton

emission

On neutron-rich side:

Evidence for 34Ne, 37Na in a search for 40Mg (not

observed)

deduced particle instability of 33Ne, 36Na

Contributions to Nuclear Structures Studies at GANIL

Search for new nuclei and new decay modes


Focal plane γ-spectroscopy: β-decay and new isomers

β-delayed γ-n spectroscopy (with TONNERRE coupled to clover detectors) of very neutron rich nuclei around N=20 and N=28:

β-decay of 32,33Mg and level scheme of 32,33Al. limits of the island of inversion located around N=20 are not well defined.

neutron-rich nuclei around N=28: new lifetimes for 12 nuclei, new Pn probabilities, new transitions in 45,46Ar.

New Island of μs Isomers in Neutron-Rich Nuclei Around Z = 28 and N = 40: study of 71Co, 73Co, 76Ni, 67Fe, 72Ni

New Shape Isomer in the Self-Conjugate Nucleus 72Kr (0+ isomer measured with combined γ – CE spectroscopy)

Observation of 0+ isomer in 44S (shape coexistence)

TONNERRE multidetector, built jointlyby IFIN-HH and LPC-Caen; used inGANIL and ISOLDE/CERN



Combined CE- spectroscopy of isomers populated in fragmentation

0+ isomer observed in 44S, and known isomer in 43S -- interpreted as shape coexistence evidence in neutron rich N=28 nuclei

44S =2.3±0.3 μs

Gre

vy e

t al., E

PJA

(EN

AM

04)

Sarazin et al.,PRL 84(2000)5062

Nummela et al.,PRC 63(2001)044316


Fragmentation reactions (double fragmentation) to populate excited states in extremely far from stability nuclei. ( SPEG spectrometer and Chateau de Cristal)

Search for neutron excitations across the N = 20 shell gap in 25-29Ne

N = 14 and 16 shell gaps in neutron-rich oxygen isotopes

Structure of the neutron-rich 37, 39P and 43, 45Cl nuclei

Shape evolution in heavy sulfur isotopes and erosion of the N=28 shell closure

Recent experiment for 42Si and 36Ca (collapse of N=28

magicity)

In-beam γ– ray spectroscopy

Recent experiment for 42Si and 36Ca (collapse of N=28 magicity)


E (

2+

) M

eV

Collapse of N=28 Shell Closure in 42Si

B. Bastin et al., PRL99(2007)022503

40Si42Si

E

M/Q

Identification after 2nd fragmentation using SPEG spectrometer Chateau de Cristal -

detector

44S secondary beam

New experimental results and shell model calculations indicate that 42Si is best described by a well deformed oblate rotor


Research group: senior researchers: 8 researchers: 5 PhD students: 6


188Pb triple shape coexistence

188Pb triple shape coexistence

12 spherical 11– oblate 8– prolate (1i13/2)2 (1i13/2 1h9/2) (1i13/2 1h9/2

1)

G.D.Dracoulis et al., Phys.Rev. C 67, 051301(R) (2003)

Static moment experiments - in progress at LNL


New Island of μs Isomers in Neutron-Rich Nuclei Around the Z = 28 and N = 40 Shell Closures

Beta-decay of 71Co and 73Co

Evidence for an isomer in 76Ni

Isomeric decay of 67Fe -- Evidence for deformation

Low energy levels in 72Ni

New Shape Isomer in the Self-Conjugate Nucleus 72Kr (0+ isomer measured with combined – CE spectroscopy)


Focal plane γ– spectroscopy. β-decay and New Isomers



-delayed n- spectroscopy with TONNERRE

TONNERRE installed in focal plane ofLISE-III Spectrometer

TONNERRE was built joint by IFIN-HH and LPC-Caen.It has ~ 50% angular coverage and 25% typical intrinsic resolution for few MeV neutrons. The threshold corresponds to about 300 keV neutron energy.

TONNERRE was used in GANIL and ISOLDE/CERN.

32Mg decay

Typical implantation setup allowsmeasurements of --n coincidences.


F. Della Vedova et al, Eur. Phys. J. A27 (2006) 301

> Large MED between ~pure sp (f7/2) analog states;

> Different E1 decay pattern of analog pos. parity states:

importance of multipole Coulomb & electromagneticspin-orbit terms.


4) Nuclear moment measurements4) Nuclear moment measurements isomers isomers ns - µsns - µs

• Home Home new isomers, new isomers, gg, , QQs s →→ nuclei near stability

• INFN INFN LNL g, Qg, Qss → → neutron deficient nuclei

A180 K isomers , shape coexistence in Pb

• GSI GSI RISING collaboration RISING collaboration gg →→ neutron rich nuclei

Dedicated experimentsDedicated experiments Hyperfine interactions Hyperfine interactions TDPAD method TDPAD method

g factors Hext

Qs Vzz EElectric FField GGradients noncubic crystalline lattices


LNL LNL 164164Dy(Dy(1616O,4n)O,4n)176176W W 83 MeV

Pulsed beam T=2 ns Trep=800 ns

g Qs 176W I= 14+ high K isomer

B. Crowell et al., PRL 72, 1164 (1994)

High K states E transitions

= ΔK – degree of K forbiddenness

f= (T1/2 /T1/2

W) 1/

Anomalous decay f

917 keV 2.3 714 keV 3.0 945 keV 3.6 fν 100 normal decay

T1/2=41(1) ns


M. Ionescu-Bujor et al., Phys. Lett. B 495, 289 (2000) Phys. Lett. B 541, 219 (2002)

g factor Hext = 27.5 kG Qs EFG Tl crystalline lattice

gexp = + 0.462

(11)

|Qs | = 6.0 (7) eb 7/2+ [404] 9/2- [514] 5/2- [512] 7/2+ [633]

2 (14+) =

0.29(4)

• deformed pure four – quasiparticle configuration

• well defined K = 14

• anomalous decay due to K mixing in the lower K states

176W I =14+


11- → 2.9 (3) eb 3.6(4) eb

12+ → 0.32 (4) eb 0.48 (3) eb

M. Ionescu-Bujor et al., Phys. Lett. B 650, 141 (2007)

T1/2 = 758 ns T1/2 = 133 ns

T1/2 = 370 ns T1/2= 1080 ns

Qs normal and intruder states in 192,194Pb 12 (1i13/2 )2

11 1i13/21h9/2

1212++

---- PQ---- PQ TAC

2 + 0.02

2 –0.12 1111

IBMHFB

Qo (11, 192Pb) shape mixing

EFG Bi crystalline lattice

nupecc – bucharest – oct. 2007 nuclear spectroscopy at the department of nuclear physics –...

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