Experimental achievements and outlook(only a few examples to illustrate the achievements and to paint the “road map” for the future)

• Extreme proton-to-neutron ratios• Isospin as a degree of freedom (along N=Z)• The heaviest nuclei• High-spins and exotic excitations• Giant resonances in cold- and hot nuclei

• Developments in instrumentation and facilities

• Isotope Separator On-Line:

• In-Flight Separator:

N=Z

Ge70 Ge72 Ge73 Ge74

Se74

As75

Ge76

Se76 Se77 Se78

Kr78

Br79

Se80

Kr80

Br81

Kr82

Sr84

P

P

P

Ge62 Ge63 Ge64 Ge65

As65

Se65

Ge66

As66

Se66

Ge67

As67

Se67

Ge68

As68

Se68

Ge69

As69

Se69

As70

Se70

Br70

Kr70

Ge71

As71

Se71

Br71

Kr71

As72

Se72

Br72

Kr72

As73

Se73

Br73

Kr73

Sr73

As74

Br74

Kr74

Rb74

Sr74

Ge75

Se75

Br75

Kr75

Rb75

Sr75

As76

Br76

Kr76

Rb76

Sr76

Ge77

As77

Br77

Kr77

Rb77

Sr77

Ge78

As78

Br78

Rb78

Sr78

Y78

As79

Se79

Kr79

Rb79

Sr79

Y79

Br80

Rb80

Sr80

Y80

Kr81

Rb81

Sr81

Y81

Rb82

Sr82

Y82

Rb83

Sr83

Y83 Y84 Y85

34

35

36

37

38

Z = 39

(H. Schatz et al. Phys. Rep. 294 (1998) 167)

possible waiting points

possible rp - process main path

mass excess not yet measured (AME95)

ISOLTRAP measurements2000 - 2002

before 2000

As63 As64

rp-processF. Hertfurth, ISOLTRAP,Hirschegg 2002

Super-allowed Fermi -decay74Rb (T1/2=65 ms)

Extreme proton-to-neutron ratios: masses

ISOLDE

m = 4.5 keV (m/m = 6 10-8)

0

ISOLTRAP

AME95

CSS2 (GANIL)A.S. Lalleman et al., Hyp. Int. 132 (2001) 315

0

20

40

60

80

%

20002002

Q T1/2 R R <Ft>

C uncertainty budget

R =

0.5

%

Ch. Scheidenberger, GSI, Hirschegg 2002

238U fission

• mapping the mass surface• high-precision mass measurements on short-lived isotopes• nuclear structure, astrophysical scenarios, fundamental interactions• g.s. and i.s. properties (cfr. laser spectroscopy, e--RIB intersecting storage rings)

• also at Mistral, SPEG (GANIL),...

0.0

1.0

2.0

3.0

E (

MeV

)

obla

te

prolate

?

Z = 82

N = 126N = 104 (midshell)

188Po 189Po 191Po

186Pb

Triple shape coexistence at low excitation energy

Extreme proton-to-neutron ratios: shapes, symmetries and low-lying excitations

spheri

cal

Hartree-Fock + BCS (Skyrme SLy6 interaction + density dependent zero-range pairing force) (M. Bender, P.H. Heenen)

decay and in-beam studies

52Cr (255 MeV) + 142Nd 190Po + 4n

( )

2 332 332 33

1 33 8

9 01

5 32

0

1 33 8

(1 82 2))(

)( (2 37 6)

)

)(

(

(

(

(

(

)

)

)

)

0 100 200 300 400 500 600 700 8000

2

4

6

8

23

3

484437

36

9

299

Energy / keV

Co

un

ts

10

554

- RP -

T(RP - ) < 10ms

E 190Po decay

190Po

Energy / keV6200 6400 6600 6800 7000 7200 7400 7600

10

102

103

104

190Bi191gBi

191Bi

190Po

188Bi

188Bi191Po

192Po

Co

un

ts

190Po

Extreme proton-to-neutron ratios: shapes, symmetries and low-lying excitations

160 nbarn !!

Recoil Decay Tagging (RDT)

RITU - JYFL

PSSD

Q DQ

Qbeam

target -detectors

Recoil

Decay

Tagging

Extreme proton-to-neutron ratios: shapes, symmetries and low-lying excitations

First results from SPIRAL and REX-ISOLDE

E (keV)

Neutron pick-up of 30Mg (T1/2=0.3 s)

30Mg + 2H 31Mg + 1H10.000 atoms/sec2.23 MeV/u

31Mg

16N (from beam contamination)

REX-ISOLDE - CERN + MINIBALL array

76Kr + 48Ti500.000 atoms/sec2.6 - 4.4 MeV/u

Coulomb excitation of 76Kr (T1/2=14.6 h)

SPIRAL - GANIL + EXOGAM array

• decay- and RTD studies of exotic nuclei• Coulomb excitation and one- or two particle transfer reactions with energetic radioactive beams (e.g. around 132Sn and 100Sn - 78Ni, light Pb nuclei)

2

8

82

20

24O31F

Z

N

Position of the neutron drip line:one extra proton added to the closed Z=8 shell binds 6 extra neutrons!

two-neutron halo

one-neutron halo

one-proton halo

four-neutron halo

3He 4He 5He 6He 7He 8He 9He 10He

2H1H 3H

1n

N=8

N=2

Z=2

• complete kinematics: 6He, 11Li• p-elastic scattering @ relativistic energies• ...• in-beam gamma spectroscopy

Extreme proton-to-neutron ratios: unbound systems and the lightest nuclei

thick target

wedge

36S Gamma-ray detectors

SPEG spectrometer

SISSI target

-high intensity beam (36S at 77.5 MeV/A, I 500pnA)

-thick target 216 mg/cm2 of C and H

-low counting rate in gamma-ray detectors

24F, 25,26Ne, 27,28Na, 29,30Mg

M. Lewitowicz Hirschegg 2002

In-beam gamma-ray spectroscopy

20C

Sn=3.34(23) MeV

Counts

E(keV)

4 6 8 10 12 14 16 181000

2000

3000

4000

5000

6000

7000

C O

N

24O

20CEnerg

y 2

+ (

keV

)

closed shell

2+-0+

Extreme proton-to-neutron ratios: unbound systems and the lightest nuclei

Two-proton decay of 45Fe

• study of neutron skin nuclei, halo nuclei• confirmation of two-proton decay, correlations, map the proton drip line• clustering phenomena in unstable nuclei• increased intensity and beam purity of the second generation facilities is needed

Extreme proton-to-neutron ratios: unbound systems and the lightest nuclei

22 events

Q2p =1.14 MeVT1/2 =3.8 ms

GANILGSI

• isospin symmetry and mirror pairs (extended to heavier masses along the N=Z line): • changes in collectivity: strong overlap between and wave function along the N=Z line• proton-neutron pairing: T=1 versus T=0

quenching of pairing field in neighboring NZ nuclei?

• direct reactions with RIB• high-intensity stable beams and instrumentation (cfr. AGATA)

Isospin as a degree of freedom

LNL - LegnaroGammashpere

19962000

2001

• confirmation element Z=112 (GSI)• chemistry Hs (Z=108) (GSI)• new results from Dubna tentatively assigned to Z=114, 116, 118• gamma- and electron spectroscopy around 245No (e.g. RITU-JYFL)

electron spectrum from 245No (Z=102)

• n-rich RIB on n-rich targets: reach region where decay chain from Z=114, 116,... ends• exploration of the structure of the trans-uranium nuclei• high intensity stable beams, new spectrometers and detectors

The heaviest elements

112277

Hs269

143Eu

SD

ND

E*

NORMAL minimum

SUPER deformed minimum

FEEDING of SD bands

DECAY-OUT of SD bands:Coupling betweenordered and chaotic states

E*

NORMAL minimum

SUPER deformed minimum

FEEDING of SD bands

DECAY-OUT of SD bands:Coupling betweenordered and chaotic states

SD

ND

143Eu

The highest spin and exotic excitations

• Euroball (Legnaro and Strasbourg) Gammasphere• giant dipole resonances on super deformed states• “wobbling mode”: breaking of axial symmetry• magnetic rotation• spontaneous chiral symmetry breaking

• Rising at GSI

• search for hyperdeformed states• need for intense stable beams• gamma-ray tracking (cfr. AGATA)

Giant resonances in cold- and hot nuclei

real photons16O

20O

22O

virtual photons from 500-600 MeV/u 20,22O on Pb

• study the bulk properties of asymmetry in nuclear matter (exotic nuclei): e.g. -skin thickness• high-quality data with (d, 2He), (3He,t),... combined with large scale shell model calculations• elastic- and inelastic electron scattering, scattering on light nuclei and transfer reactions using RIB (intersecting storage rings)

• Strength, centroid energy and width: governed by macroscopic nuclear properties (isoscalar - isovector modes)• Microscopically: coherent 1p-1h excitations / properties depend on the isoscalar and isospin dependence of the effective n-n interaction

• Photo-neutron cross sections for 16, 20, 22O xn strongly fragmented/extended to low energy impact on astrophysical scenarios

GSI

• Neutron-skin thickness can be deduced from Giant resonances (so far stable isotopes only)• Large proton-neutron asymmetry (exotic nuclei) can lead to “soft” collective resonances

Instrumentation and facilities

• ISOL and IF are complementary• Experimental aim of the second generation facilities

figure of merit for the study of exotic nuclei x > 1000• Technological challenge

increase the global selectivity and sensitivity increase the secondary beam intensity

• accelerator developments• target and ion source developments

• detector developments (e.g. AGATA, ...)

• target-ion source developments(e.g. laser ionisation,...)• spectrometer developments

beam energy (MeV/u) 0 - 25up to 100

50 - 1000down to 5

beam quality (emittance) + +/-

intensity (isotope dependent!)

132Sn 78Ni

short-lived nuclei +/- + (down to s)

Instrumentation and facilities

ISOLDE - CERN

GSI-Darmstadt

JYFL-Jyväskylä

GANIL-Caen

CRC-Louvain-la-Neuve

KVI-Groningen

LNL-Legnaro

TSL-Uppsala

FZJ-Jülich

ECT*-Trento

Oak-Ridge, MSU, Triumf and RIA(North-America)

GSI

European Separator On-LineRadioactive Nuclear Beam Facility

RIKEN (Japan)Radioactive Beam Factory

• The last 5 years have witnessed important advances in technical developments and in the understanding of the atomic nucleus. Key issues, that should be addressed, have been identified.• Stable-beam experiments have been the driving force for many decades of nuclear-structure research. This limit of some 300 different beams will be overcome by the second generation radioactive beam facilities and a major part of the chart of nuclei will be available for tailored experiments.• Exotic nuclei are indeed a very selective probe (N/Z variation, neutron skins, coupling to the continuum,...) and the planned developments will bring new, accurate and unique information.

Conclusion and recommendations

Vigorous exploitation of the existing accelerators and instrumentation (including upgrades)

• physics results• R&D for beam production and detector systems• experimental capabilities for the coming 5 to 10 years

Full support for the new GSI accelerator complex and for the EURISOL project• ISOL and IF facilities are both needed (complementary aspects)• the new GSI accelerator complex: full support and start construction• EURISOL: next 5 years full conceptual design should be made and site determined, start construction at the end of this period• multi-users aspect should be incorporated

Very strong support for rebuilding nuclear-structure and nuclear-reaction theory efforts

• provisions for new theoretical groups and expansion of existing groups• support for ECT* maintained and expanded Communicate the highlights to society