First results from the AGATA Demonstrator. Francesco Recchia Università di Padova

Transcription

1 First results from the AGATA Demonstrator Francesco Recchia Università di Padova XCVII Congresso Nazionale SIF L'Aquila, Settembre, 2011

2 Challenges in Nuclear Structure Shell structure in nuclei Structure of doubly magic nuclei Changes in the (effective) interactions Shape coexistence Transfermium nuclei Proton drip line and N=Z nuclei Spectroscopy beyond the drip line Proton-neutron pairing Isospin symmetry Nuclear shapes Exotic shapes and isomers Coexistence and transitions 48 Ni 100 Sn 78 Ni 132+x Sn Neutron-rich heavy nuclei (N/Z 2) Large neutron skins (r n -r p 1fm) New coherent excitation modes Shell quenching Nuclei at the neutron drip line (Z 25) Very large proton-neutron asymmetries Resonant excitation modes Neutron Decay

3 Experimental conditions and challenges FAIR SPIRAL2 SPES EURISOL ECOS Low intensity High backgrounds Large Doppler broadening High counting rates High γ-ray multiplicities Need of advanced instrumentation High efficiency High sensitivity High throughput Ancillary detectors

4 Gamma Arrays based on Compton Suppressed Spectrometers Tracking Arrays based on Position Sensitive Ge Detectors EUROBALL GAMMASPHERE AGATA GRETA ε ~ 10 7 % ( M γ =1 M γ =30) ε ~ % ( M γ =1 M γ =30)

5 80 mm AGATA detectors 90 mm ~2 kg 6x6 fold segmented cathode 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

6 Pulse Shape Analysis concept A3 A5 (10,10,46) B3 B5 C3 C5 (10,30,46) y CORE measured D4 x 791 kev deposited in segment E4 F4 z = 46 mm

7 Pulse Shape Analysis concept A3 A5 B3 B5 C3 C5 (10,10,46) y CORE measured calculated D4 x 791 kev deposited in segment E4 F4 z = 46 mm

8 Pulse Shape Analysis concept A3 A5 B3 B5 C3 C5 (10,15,46) y CORE measured calculated D4 x 791 kev deposited in segment E4 F4 z = 46 mm

9 Pulse Shape Analysis concept A3 A5 B3 B5 C3 C5 (10,20,46) y CORE measured calculated D4 x 791 kev deposited in segment E4 F4 z = 46 mm

10 Pulse Shape Analysis concept A3 A5 B3 B5 C3 C5 (10,25,46) y CORE measured calculated D4 x 791 kev deposited in segment E4 F4 z = 46 mm

11 Pulse Shape Analysis concept A3 A5 B3 B5 C3 C5 (10,30,46) y CORE measured calculated D4 x 791 kev deposited in segment E4 F4 z = 46 mm

12 Pulse Shape Analysis concept A3 B3 A5 B5 Result of Grid Search algorithm C3 C5 (10,25,46) y CORE measured calculated D4 x 791 kev deposited in segment E4 F4 z = 46 mm

13 Tracking of radiation in High Energy Physics in Nuclear Spectroscopy 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 ( MeV) neutral transition with low density of energy deposition General-purpose detectors for a large variety of experiments Physics derived from large number of incomplete events

14 Tracking of E~ MeV γ-rays E γ' 1 E γ 2 0 m c E γ 1 cosθ MC simulation of a high-multiplicity event Efficiency depends on position resolution M g = 30

15 AGATA Advanced GAmma Tracking Array 180 hexagonal crystals 3 shapes 60 triple-clusters all equal Inner radius (Ge) 23.5 cm Amount of germanium 362 kg Solid angle coverage 82 % 36-fold segmentation 6480 segments Singles rate ~50 khz Efficiency: 43% (M g =1) 28% (M g =30) Peak/Total: 58% (M g =1) 49% (M g =30) 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

16 The AGATA Demonstrator Objective of the final R&D phase symmetric triple-cluster 5 asymmetric triple-clusters fold segmented crystals 540 segments 555 high resolution digital-channels Eff. 3 8 M γ = 1 Eff. 2 4 M γ = 30 Operate in real time ACQ, Pulse Shape Analysis and γ-ray Tracking Hosting site: LNL

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19 de (MeV) Doppler correction capabilities Inelastic scattering MeV/u on 208 Pb 16 O O F No Dopp Corr Crystal Centers Segment Centers PSA+Tracking N C B Be Li a TKE (MeV) Nicolini Mengoni

20 gg capabilities The performance of AGATA using g-ray tracking is comparable to conventional arrays with a much larger number of crystals 32 S 110 Pd 135 MeV 6 AGATA crystals only 138 Sm 6 gates on: 347keV,545keV,6 86keV,775keV,55 2keV,357keV 871keV

21 Orbital migrations V Proton-neutron spin-flip interaction f r Tensor force 2 s s Y f r 2 V T T. Otsuka et al., PRL87, (2001); T. Otsuka et al., PRL 95, (2005) Energies of the orbitals depend on the occupancy of the partner orbitals

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24 protons The Experimental Campaign at LNL Isospin Mixing in 80 Zr Coulomb Excitation of 42 Ca Molecular structure of 21 Ne Neutron-rich nuclei in the vicinity of 208 Pb Pygmy and GQR states Proton drip-line Octupole-deformed Ra and Th nuclei n-rich nuclei Neutron drip-line Order-to-chaos transition in warm rotating 174 W nuclei Lifetime of 136 Te N=84 isotone 140 Ba N=51 nuclei Neutron-rich nuclei populated by fission Lifetime measurements of the neutron-rich Cr isotopes Lifetimes near the island of inversion Lifetime measurement in neutron-rich Ni, Cu and Zn isotopes neutrons Lifetime measurement of the 6.792MeV state in 15 O

25 Conclusions One-year-long commissioning campaign Physics campaign from Feb to Dec 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.

26 AGATA Demonstrator/1π Experimental Program 2010 LNL 5TC 2012 GSI/FRS 8TC 2014 GANIL/SPIRAL2 ~15TC AGATA D.+PRISMA Total Eff. ~6% AGATA FRS Total Eff. > 10% AGATA D. + VAMOS + EXOGAM Total Eff. > 20%

27 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