Advanced GammaRay Spectroscopy Techniques with the AGATA Segmented

Advanced Gamma–Ray Spectroscopy Techniques with the AGATA Segmented Detectors Călin A. Ur* for the AGATA Collaboration INFN – Sezione di Padova *On leave from IFIN–HH Bucharest

Layout • Principles of the AGATA gamma–ray tracking array • Building phases of the array • The AGATA Demonstrator • First tests at the National Laboratories of Legnaro • Compton imaging with segmented detectors 01/02/2010 ELI NP Workshop Bucharest 2

Extreme Experimental Conditions FAIR SPIRAL 2 SPES REX-ISOLDE EURISOL HI-SIB • • • Low intensity High backgrounds Large Doppler broadening High counting rates High -ray multiplicities Need instrumentation 01/02/2010 High efficiency High sensitivity High throughput Ancillary detectors ELI NP Workshop Bucharest 3

Extreme Experimental Conditions FAIR SPIRAL 2 SPES REX-ISOLDE EURISOL HI-SIB • • • Low intensity High backgrounds Large Doppler broadening High counting rates High -ray multiplicities ELI ? Need instrumentation 01/02/2010 High efficiency High sensitivity High throughput Ancillary detectors ELI NP Workshop Bucharest 4

The New Concept of Tracking Arrays Gamma Arrays based on Compton Suppressed Spectrometers Compton rejected AC Full energy accepted AC EUROBALL GAMMASPHERE Tracking Arrays based on Position Sensitive Ge Detectors AGATA e ~ 10 — 7 % e ~ 50 — 25 % ( Mg=1 — Mg=30) 01/02/2010 GRETA ( Mg=1 — Mg=30) ELI NP Workshop Bucharest 5

Analogue vs Digital Electronics Present Arrays E ADC t TDC CFD DAQ Detector (Germanium) Shaping Amplifier AGATA NSR Filters Segment 01/02/2010 ELI NP Workshop Bucharest t t x, y, z Detector E DAQ FADC E Tracking Detector (Germanium) E PSA MWD t Array 6

Ingredients of Gamma–Ray Tracking 1 4 Highly segmented HPGe detectors Reconstruction of tracks evaluating permutations of interaction points · Pulse Shape Analysis to decompose recorded waves · 3 2 Digital electronics to record and process segment signals 01/02/2010 Reconstructed gamma-rays ELI NP Workshop Bucharest 7

Position Determination – PSA Calculation of the signals induced on the contacts using the weighting field method FEM-model of detector · ·· · · · net charge signals Calculate weighting fields * transient signals · · · · Th. Kröll, NIM A 463 (2001) 227 01/02/2010 ELI NP Workshop Bucharest 8

Pulse Shape Analysis Concept A 3 A 4 A 5 (10, 46) B 3 C 3 B 4 C 4 B 5 C 5 (10, 30, 46) y CORE C 4 B 4 measured D 4 791 ke. V deposited in segment B 4 01/02/2010 ELI NP Workshop Bucharest x A 4 E 4 F 4 z = 46 mm 9

Pulse Shape Analysis Concept A 3 A 4 A 5 B 3 B 4 B 5 C 3 C 4 C 5 (10, 46) y CORE C 4 measured calculated 791 ke. V deposited in segment B 4 01/02/2010 ELI NP Workshop Bucharest B 4 D 4 x A 4 E 4 F 4 z = 46 mm 10

Pulse Shape Analysis Concept A 3 A 4 A 5 B 3 B 4 B 5 C 3 C 4 C 5 (10, 15, 46) y CORE C 4 measured calculated 791 ke. V deposited in segment B 4 01/02/2010 ELI NP Workshop Bucharest B 4 D 4 x A 4 E 4 F 4 z = 46 mm 11

Pulse Shape Analysis Concept A 3 A 4 A 5 B 3 B 4 B 5 C 3 C 4 C 5 (10, 20, 46) y CORE C 4 measured calculated 791 ke. V deposited in segment B 4 01/02/2010 ELI NP Workshop Bucharest B 4 D 4 x A 4 E 4 F 4 z = 46 mm 12

Pulse Shape Analysis Concept A 3 A 4 A 5 B 3 B 4 B 5 C 3 C 4 C 5 (10, 25, 46) y CORE C 4 measured calculated 791 ke. V deposited in segment B 4 01/02/2010 ELI NP Workshop Bucharest B 4 D 4 x A 4 E 4 F 4 z = 46 mm 13

Pulse Shape Analysis Concept A 3 A 4 A 5 B 3 B 4 B 5 C 3 C 4 C 5 (10, 30, 46) y CORE C 4 measured calculated 791 ke. V deposited in segment B 4 01/02/2010 ELI NP Workshop Bucharest B 4 D 4 x A 4 E 4 F 4 z = 46 mm 14

Pulse Shape Analysis Concept A 3 A 4 Result of A 5 Grid Search algorithm B 3 C 3 B 4 C 4 B 5 C 5 R. Venturelli (10, 25, 46) y CORE C 4 measured calculated 791 ke. V deposited in segment B 4 01/02/2010 ELI NP Workshop Bucharest B 4 D 4 x A 4 E 4 F 4 z = 46 mm 15

Interaction/Reconstruction Algorithms ~ 100 ke. V Photoelectric Isolated hits ~1 Me. V Compton Scattering Angle/Energy ~ 10 Me. V -ray energy Pair Production Pattern of hits E 1 st = E – 2 mc 2 Probability of interaction depth Algorithms: Cluster. Tracking, Fuzzy. Tracking, Back. Tracking, … Reconstruction efficiency limited by Position resolution and Compton profile. 01/02/2010 ELI NP Workshop Bucharest 16

Pulse Shape Analysis Concept Idealized configuration to determine maximum attainable performance. Ri = 15 cm Ro = 24 cm 230 kg of Ge A high multiplicity event Eg = 1. 33 Me. V Mg = 30 Events simulated using GEANT 4 Response of shell at 1. 33 Me. V: eph = 70% P/T = 77% Reconstruction by Cluster-Tracking Packing Distance: 5 mm Position Resolution: 5 mm (at 100 ke. V) 1. 33 Me. V Mg = 1 Mg = 30 eph (%) 65 36 P/T(%) 85 60 01/02/2010 27 gammas detected -- 23 in photopeak 16 reconstructed -- 14 in photopeak ELI NP Workshop Bucharest D. Bazzacco 17

Possible Array Configurations A 180 is AGATA’s choice Configuration 120 crystals 180 crystals 01/02/2010 A 120 F A 120 C 4 A 180 Crystals (shapes) 120 (2) 120 (6) 120 (2) 180 (3) Clusters (shapes) 40 (2) 30 (1) 60 (2) Ge solid angle (%) 71. 0 77. 8 78. 0 81. 6 Ge weight (kg) 232 225 230 363 Centre to Ge (cm) 19. 7 18 18. 5 23. 5 Electronics channels 4440 6660 Eff. at M = 1 (%) 32. 9 36. 4 43. 3 Eff. at M = 30 (%) 20. 5 22. 0 22. 1 28. 1 P/T at M = 1 (%) 52. 9 53. 0 51. 8 58. 2 P/T at M = 30 (%) 44. 9 43. 7 43. 4 49. 1 GRETA is for A 120 C 4 ELI NP Workshop Bucharest 18

The Advanced GAmma Tracking Array Requirements efficiency, energy resolution, dynamic range, angular resolution, timing, counting rate, modularity, angular coverage, inner space Quantity Specified for Target Value Eγ = 1 Me. V, Mγ = 1, < 0. 5 50 % Eγ = 1 Me. V, Mγ = 30, < 0. 5 25 % Eγ = 10 Me. V, Mγ = 1 10 % Peak-to-total ratio (P/T) Eγ = 1 Me. V, Mγ = 1 60 - 70 % Eγ = 1 Me. V, Mγ = 30 40 - 50 % Angular resolution ( ) E/E < 1% Maximum event rates Mγ = 1 Mγ = 30 Photo-peak efficiency (eph) Inner space for ancillaries 01/02/2010 better than 1 3 MHz 300 k. Hz > 170 mm ELI NP Workshop Bucharest 19

Construction of the AGATA Array Ge crystals: Hexaconical shape 90 -100 mm long 80 mm max diameter 36 segments Al encapsulation: 0. 4 mm spacing 0. 8 mm thickness Triple clusters: 3 encapsulated crystals Al end-cap: 2. 0 mm spacing 1. 0 mm thickness 111 cold FET preamplifiers Distance between faces of crystals: in same cluster ~2. 5 mm in adjacent clusters ~9. 0 mm 01/02/2010 Total weight of the 60 clusters of the AGATA 180 configuration ~2. 5 tons Mounted on a self-supporting structure ELI NP Workshop Bucharest 20

Asymmetric AGATA Triple Cryostat - integration of 111 high resolution spectroscopy channels - cold FET technology for all signals Challenges: - mechanical precision - heat development, LN 2 consumption - microphonics - noise, high frequencies FWHM [ke. V] @1. 3 Me. V @ 60 ke. V Core 2. 10 ke. V @ 1. 3 Me. V 1. 20 ke. V @ 60 ke. V 01/02/2010 ELI NP Workshop Bucharest 21

Electronics and DAQ Fully synchronous system with global 100 MHz clock and time-stamp distribution (GTS) Digitizers: 100 Ms/s, 14 bit Optical fiber read-out of full data stream to pre-processing electronics GTS detector clk Preamps ital lifier g i D amp pre. Digitizers Local processing triggered by Ge common contact. Determine energy and isolate ~ 600 ns of signal around rise-time Buffers of time-stamped local events sent to PSA to extract position of interactions Digitizers 7. 4 GB/s/det Local processing 100 MB/s/det @ 50 k. Hz PSA 5 MB/s/det Trigger-less system. Global trigger possible. Global event builder and software trigger Event Builder On-line gamma-ray tracking Tracking Control and storage (~1 TB/year), … On line… Storage … 01/02/2010 ELI NP Workshop Bucharest … 22

The Phases of AGATA 1 5 Clusters Demonstrator Our days Peak efficiency 3 – 8 % @ M = 1 2 – 4 % @ M = 30 Main issue is Doppler correction capability coupling to beam and recoil tracking devices Improve resolution at higher recoil velocity Extend spectroscopy to more exotic nuclei 01/02/2010 ELI NP Workshop Bucharest 23

The Phases of AGATA 2 Near future 15 Clusters 1 p b=0 The first “real” tracking array b = 0. 5 Recoil velocity To be used at FAIR-HISPEC, SPIRAL 2, SPES, … 01/02/2010 ELI NP Workshop Bucharest 24

The Phases of AGATA 3 45 Clusters 3 p Far future Efficient as a 120 ball (20% at high multiplicity) Ideal for FAIR and EURISOL 01/02/2010 ELI NP Workshop Bucharest 25

The Phases of AGATA 4 60 Clusters 4 p Remote future Full ball / full performance Ideal to study extreme deformations and the most exotic nuclear species 01/02/2010 ELI NP Workshop Bucharest 26

The AGATA Demonstrator Objective of the R&D phase 2003 -2008 5 asymmetric triple-clusters 36 -fold segmented crystals 540 segments 555 digital-channels Eff. 3 – 7 % @ M = 1 Eff. 2 – 4 % @ M = 30 Full ACQ online PSA and –ray tracking Cost ~5 M€ Present status 3 asymmetric triple-clusters mounted&tested at INFN LN Legnaro +1 in delivery Undergoing commissioning runs detectors, DAQ, PSA, online Physics campaign to start in ~1 month 01/02/2010 ELI NP Workshop Bucharest 27

First in–beam Test at LNL • Week 12 (March 16 -22) • 30 Si(@70 Me. V)+12 C fus. –evap. reaction in inverse kinematics • The system included – full AGATA DAQ chain – PSA and tracking performed in real time (online) • Goal – test the whole system under real data taking conditions – test Doppler correction capability of the AGATA detectors 01/02/2010 ELI NP Workshop Bucharest 28

Doppler Broadening and Position Res. Position resolution Dq q Angular resolution g ray Recoil Beam Energy resolution 01/02/2010 ELI NP Workshop Bucharest 29

Doppler Broadening and Position Res. 11: 42 17/03/2009 40 K 1823 ke. V b ~ 5% 12. 5 ke. V full detector segments (17. 7 ke. V) PSA+tracking Full optimization and analysis – 1 month our target online 01/02/2010 ELI NP Workshop Bucharest 30

Compton Imaging Compton scattering – a tool for testing the position resolution • In-beam experiment – given the position of the target we track the g rays E 1 E 2 target g ray Compton scattering • Compton imaging of a radioactive source – inverse tracking – from the first 2 interaction points get the position of the source 01/02/2010 E 1 g-source E 2 g ray ELI NP Workshop Bucharest F. Recchia 31

[deg] Principles of Compton Imaging 01/02/2010 ELI NP Workshop Bucharest 32

angular error [deg] Compton Imaging Performance Sources of error in the identification of the source direction: • Position resolution (axis) • Energy resolution (scattering angle) • Compton profile (scattering angle) 01/02/2010 ELI NP Workshop Bucharest scattering angle [deg] 33

Experimental Setup at LNL Digital DAQ system provided by IFIN – HH Bucharest • 10 x TNT 2 NIM Digitizer boards from CAEN with 4 ch 14 bit /100 MHz 60 Co 01/02/2010 source ELI NP Workshop Bucharest AGATA prototype detector (one symmetric capsule) 34

Comparison with MC Simulations profile of experimental image Projections Experiment peak FWHM [deg] After PSA 5. 2 position resolution FWHM [mm] f profile of experimental image Monte Carlo + 5 mm position resolution peak FWHM [deg] f [deg] MC MC 4. 7 position resolution FWHM [mm] 01/02/2010 ELI NP Workshop Bucharest 35

Gamma Background Rejection characterize the capability of the AGATA detectors to discriminate different gamma source locations using Compton imaging algorithm Experimental Setup: 3 g–ray sources 60 Co, 152 Eu and 137 Cs their positions simulate the beam-dump, the beam line and the target M. Doncel & F. Recchia 01/02/2010 ELI NP Workshop Bucharest 36

Results a) E 1 = 1173 ke. V E 2 = 1332 ke. V Spectra of the gamma radiation assigned to each source position with the algorithm Spectra assignment a) corresponds to the 60 Co position b) corresponds to the 137 Cs position c) corresponds to the 152 Eu position • promising results • need more refinement of the method 01/02/2010 b) E = 661 ke. V c) ELI NP Workshop Bucharest E = 344 ke. V 37

Outlook To exploit the present and future facilities fully and most efficiently, advanced instrumentation and detection equipment is required – Nu. PECC recommendation The 4 p-array of highly segmented Ge detectors AGATA for -ray detection and tracking is part of this effort First measurements in-beam and with sources show that the position resolution is ~ 5 mm FWHM; this value is in line with the design assumptions of the AGATA spectrometer, confirming the feasibility of -ray tracking AGATA will have a strong impact on nuclear structure studies : lifetime measurements of nuclear states down to fs, angular distribution and polarization measurements Is AGATA or part of interest for the ELI project? 01/02/2010 ELI NP Workshop Bucharest 38

The AGATA Collaboration Bulgaria: Denmark: Finland: France: Germany: Hungary: Italy: Poland: Romania: Sweden: Turkey: UK: 01/02/2010 Sofia Copenhagen Jyväskylä GANIL, Lyon, Orsay, Saclay, Strasbourg Berlin, Bonn, GSI, Darmstadt, Jülich, Köln, München Debrecen Padova, Milano, LNL, Firenze, Camerino, Napoli, Genova Krakow, Swierk, Warsaw Bucharest Lund, Stockholm, Uppsala Ankara, Istanbul Daresbury, Brighton, Keele, Liverpool, Manchester, Paisley, Surrey, York ELI NP Workshop Bucharest 39

Outlook 01/02/2010 ELI NP Workshop Bucharest 40

First in–beam test with STC Position resolution extracted through a comparison to detailed Monte Carlo simulations (FWHM vs. pos. resolution) ~5. 2 Symmetric triple cluster mm 4. 8 ke. V 11 ke. V experiment performed at IKP of Cologne 32 ke. V 01/02/2010 Silicon detector ELI NP Workshop Bucharest 41

New Challenges from the RIB Facilities Shell structure in nuclei • Structure of doubly magic nuclei • Changes in the (effective) interactions 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 Neutron rich heavy nuclei (N/Z → 2) • Large neutron skins (rn-rp→ 1 fm) • Shell quenching Nuclear Astrophysics • Properties of r and rp process nuclei Nuclei at the neutron drip line (Z→ 25) • Very large proton-neutron asymmetries • Resonant excitation modes • Neutron Decay 01/02/2010 ELI NP Workshop Bucharest 42