First results from the AGATA

Demonstrator

Francesco RecchiaUniversità di Padova

XCVII Congresso Nazionale SIFL'Aquila, 26 - 30 Settembre, 2011

Neutron-rich heavy nuclei (N/Z → 2)

• Large neutron skins (rn-rp→ 1fm)

• New coherent excitation modes

• Shell quenching

132+xSn

Nuclei at the neutron drip line (Z→25)

• Very large proton-neutron asymmetries

• Resonant excitation modes

• Neutron Decay

Nuclear shapes

• Exotic shapes and isomers

• Coexistence and transitions

Shell structure in nuclei

• Structure of doubly magic nuclei

• Changes in the (effective) interactions

48Ni

100Sn

78Ni

Proton drip line and N=Z nuclei

• Spectroscopy beyond the drip line

• Proton-neutron pairing

• Isospin symmetry

Transfermium nucleiShape coexistence

Challenges in Nuclear Structure

Experimental conditions and challenges

• Low intensity

• High backgrounds

• Large Doppler broadening

• High counting rates

• High γ-ray multiplicities

High efficiencyHigh sensitivityHigh throughputAncillary detectors

FAIRSPIRAL2SPESEURISOLECOS

Need of advancedinstrumentation

Tracking Arrays based onPosition Sensitive Ge Detectors

Gamma Arrays based on ComptonSuppressed Spectrometers

ε ~ 50 — 25 %( Mγ=1 — Mγ=30)

ε ~ 10 — 7 %( Mγ=1 — Mγ=30)

GAMMASPHEREEUROBALL GRETAAGATA

AGATA detectors

• Symmetric detectors

– 3 in use since 3 years

– Used as single or in a

triple cluster

• Asymmetric detectors

– 19 ordered

– 10 accepted

– 3 triple clusters ready

90 mm

~2 kg

80

mm

6x6 fold segmented cathode

Pulse Shape Analysis concept

B4 B5B3

C4 C5C3

CORE

A4 A5A3

C4

D4

E4 F4

A4

B4

x

y

z = 46 mm791 keV deposited in segment B4

(10,10,46)

measured

(10,30,46)

Pulse Shape Analysis concept

B4 B5B3

C4 C5C3

CORE

A4 A5A3

C4

D4

E4 F4

A4

B4

x

y

z = 46 mm791 keV deposited in segment B4

(10,10,46)

measured

calculated

Pulse Shape Analysis concept

B4 B5B3

C4 C5C3

CORE

A4 A5A3

C4

D4

E4 F4

A4

B4

x

y

z = 46 mm791 keV deposited in segment B4

(10,15,46)

measured

calculated

Pulse Shape Analysis concept

B4 B5B3

C4 C5C3

CORE

A4 A5A3

C4

D4

E4 F4

A4

B4

x

y

z = 46 mm791 keV deposited in segment B4

(10,20,46)

measured

calculated

Pulse Shape Analysis concept

B4 B5B3

C4 C5C3

CORE

A4 A5A3

C4

D4

E4 F4

A4

B4

x

y

z = 46 mm791 keV deposited in segment B4

(10,25,46)

measured

calculated

Pulse Shape Analysis concept

B4 B5B3

C4 C5C3

CORE

A4 A5A3

C4

D4

E4 F4

A4

B4

x

y

z = 46 mm791 keV deposited in segment B4

(10,30,46)

measured

calculated

Result of

Grid Search

algorithm

Pulse Shape Analysis concept

B4 B5B3

C4 C5C3

CORE

A4 A5A3

C4

D4

E4 F4

A4

B4

x

y

z = 46 mm791 keV deposited in segment B4

(10,25,46)

measured

calculated

Tracking of radiation

Very energetic particles with high density of charge deposition “continuous tracks”

Huge detectors for “one” experiment

Physics derived from the study of “complete” events

Cascades of “many” low energy (0.01 -- 10 MeV) neutral transitionwith low density of energy deposition

“General-purpose” detectors for a large variety of experiments

Physics derived from large number of incomplete events

in High Energy Physics in Nuclear Spectroscopy

Tracking of E~0.1÷10 MeV γ-rays

cosθ1cm

E1

EE

2

0

γ

γ

γ'

Mg = 30

MC simulation of a high-multiplicity event Efficiency depends on position resolution

6660 high-resolution digital electronics channels

Pulse Shape Analysis position sensitive operation mode

γ-ray tracking algorithms to achieve maximum efficiency

Coupling to ancillary detectors for added selectivity

180 hexagonal crystals 3 shapes60 triple-clusters all equal

Inner radius (Ge) 23.5 cmAmount of germanium 362 kgSolid angle coverage 82 %36-fold segmentation 6480 segmentsSingles rate ~50 kHz

Efficiency: 43% (Mg=1) 28% (Mg=30)

Peak/Total: 58% (Mg=1) 49% (Mg=30)

AGATAAdvanced GAmma Tracking Array

The AGATA DemonstratorObjective of the final R&D phase 2003-2010

1 symmetric triple-cluster

5 asymmetric triple-clusters

15 36-fold segmented crystals

540 segments

555 high resolution digital-channels

Eff. 3 – 8 % @ Mγ = 1

Eff. 2 – 4 % @ Mγ = 30

Operate in real time ACQ,

Pulse Shape Analysis and γ-ray Tracking

Hosting site:

LNL 2008-2011

Doppler correction capabilities

F

O

N

C

B

Be

a

Li

No Dopp CorrCrystal CentersSegment CentersPSA+Tracking

16O

TKE (MeV)

dE

(M

eV)

Inelastic scattering 17O @ 20 MeV/u on 208Pb

Nicolini Mengoni

gg capabilities

138Sm6 gates on:347keV,545keV,686keV,775keV,552keV,357keV

871keV 22+ - 20+

The performance of AGATA using g-ray tracking iscomparable to conventional arrays with a much largernumber of crystals

32S 110Pd 135 MeV

6 AGATA crystals only

Orbital migrations

T. Otsuka et al., PRL87, 082502 (2001);

T. Otsuka et al., PRL 95, 232502 (2005)

Proton-neutron spin-flip interaction

Tensor force

rfYssVT

22

2121

rfV

Energies of the orbitals depend on the occupancy of the “partner” orbitals

neutrons

pro

ton

s

Neutron

drip-line

Lifetime measurement of the 6.792MeV state in 15O

n-rich

nuclei

Lifetime measurementin neutron-rich

Ni, Cu and Zn isotopes

Lifetime measurements of the neutron-rich Cr isotopes

Order-to-chaos transition in warm rotating 174W nuclei

Lifetimes near the island of inversion

The Experimental Campaign at LNL

Pygmy and GQR states

Neutron-rich nuclei populated by fission

N=51 nuclei

Lifetime of 136Te

Neutron-rich nuclei in the vicinity of 208Pb

Proton

drip-line

N=84 isotone 140Ba

Molecular structure of 21Ne

Coulomb Excitation of 42Ca

Isospin Mixingin 80Zr

Octupole-deformedRa and Th nuclei

Conclusions

• One-year-long commissioning campaign

• Physics campaign from Feb. 2010 to Dec. 2011

• Analysis of the experiments performed so far is ongoing, more exciting results soon .

Performance of the array is satisfactory, mostly in coupling with several ancillary

detectors.

2010 LNL5TC

2012 GSI/FRS≥8TC

2014 GANIL/SPIRAL2 ~15TC

AGATA D.+PRISMA AGATA D. + VAMOS+ EXOGAM

AGATA D. @ FRS

Total Eff. > 10%

AGATA Demonstrator/1π

Experimental Program

Total Eff. > 20% Total Eff. ~6%

1

23

4

5

The AGATA Collaboration

Bulgaria: Sofia

Denmark: Copenhagen

Finland: Jyväskylä

France: GANIL, Lyon, Orsay, Saclay, Strasbourg

Germany: Berlin, Bonn, GSI, Darmstadt, Jülich, Köln, München

Hungary: Debrecen

Italy: Padova, Milano, LNL, Firenze, Napoli, Genova

Poland: Krakow, Swierk, Warsaw

Romania: Bucharest

Spain: Valencia, Madrid, Salamanca

Sweden: Göteborg, Lund, Stockholm, Uppsala

Turkey: Ankara, Istanbul

UK: Brighton, Daresbury, Edinburgh, Keele, Liverpool, Manchester, Paisley, Surrey, York