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Experimental achievements and outlook (only a few examples to illustrate the achievements

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- Isotope Separator On-Line:
- In-Flight Separator:

ISOL

IF

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

dC uncertainty budget

dR = 0.5%

ISOL

Q

T1/2

R

dR

<Ft>

Extreme proton-to-neutron ratios: masses

rp-process

F. Hertfurth, ISOLTRAP,

Hirschegg 2002

Super-allowed Fermi b-decay

74Rb (T1/2=65 ms)

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

ISOLDE

IF

Ch. Scheidenberger, GSI, Hirschegg 2002

238U fission

- also at Mistral, SPEG (GANIL),...

- 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)

3.0

2.0

E (MeV)

1.0

?

oblate

prolate

0.0

186Pb

ISOL

IF

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

N = 126

N = 104 (midshell)

188Po

189Po

191Po

Z = 82

decay and in-beam studies

spherical

Triple shape coexistence

at low excitation energy

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

190Po

190Bi

191gBi

104

a

g - RP - a

103

191Bi

188Bi

Ea190Po decay

DT(RP - a) < 10ms

190Po

191Po

188Bi

102

192Po

Counts

10

6200 6400 6600 6800 7000 7200 7400 7600

IF

Energy / keV

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

Recoil Decay Tagging (RDT)

RITU - JYFL

Recoil

Q

D

Q

beam

Decay

Q

target

g-detectors

PSSD

Tagging

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

s 160 nbarn !!

190Po

REX-ISOLDE - CERN + MINIBALL array

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

30Mg + 2H 31Mg + 1H

10.000 atoms/sec

2.23 MeV/u

31Mg

16N (from beam contamination)

ISOL

E (keV)

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

First results from SPIRAL and REX-ISOLDE

SPIRAL - GANIL + EXOGAM array

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

76Kr + 48Ti

500.000 atoms/sec

2.6 - 4.4 MeV/u

- 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)

ISOL

IF

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

Position of the neutron drip line:

one extra proton added to the closed Z=8 shell binds 6 extra neutrons!

one-proton halo

8

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

20

31F

24O

Z

2

one-neutron halo

8

2

N

two-neutron halo

four-neutron halo

N=8

N=2

Z=2

3He

4He

5He

6He

7He

8He

9He

10He

3H

2H

1H

1n

IF

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

In-beam gamma-ray spectroscopy

Sn=3.34(23) MeV

wedge

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

2+-0+

Counts

thick target

20C

SISSI target

36S

SPEG spectrometer

Gamma-ray detectors

E(keV)

- 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

7000

C

6000

O

5000

Energy 2+ (keV)

4000

24O

3000

2000

20C

M. Lewitowicz Hirschegg 2002

1000

4

6

8

10

12

14

16

18

closed shell

N

Q2p =1.14 MeV

T1/2 =3.8 ms

IF

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

Two-proton decay of 45Fe

22 events

- 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

GANIL

GSI

Isospin as a degree of freedom

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

LNL - Legnaro

Gammashpere

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

quenching of p-n pairing field in neighboring NZ nuclei?

IF

The heaviest elements

1996

- 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)

2000

2001

- 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

electron spectrum from 245No (Z=102)

143Eu

143Eu

SD

ND

SD

ND

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)

IF

Giant resonances in cold- and hot nuclei

- 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

16O

real photons

- 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

20O

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

22O

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

GSI

- study the bulk properties of p-n asymmetry in nuclear matter (exotic nuclei): e.g. n-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)

ISOL

IF

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

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

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

- accelerator developments
- target and ion source developments

EURISOL

European Separator On-Line

Radioactive Nuclear Beam Facility

GSI

ISOL

IF

Instrumentation and facilities

TSL-Uppsala

KVI-Groningen

JYFL-Jyväskylä

CRC-Louvain-la-Neuve

FZJ-Jülich

GANIL-Caen

GSI-Darmstadt

ISOLDE - CERN

LNL-Legnaro

Oak-Ridge, MSU, Triumf and RIA

(North-America)

RIKEN (Japan)

Radioactive Beam Factory

ECT*-Trento

Conclusion and recommendations

- 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.

- 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