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Advanced Gamma–Ray Spectroscopy Techniques with the AGATA Segmented Detectors

Advanced Gamma–Ray Spectroscopy Techniques with the AGATA Segmented Detectors. C ă lin 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

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Advanced Gamma–Ray Spectroscopy Techniques with the AGATA Segmented Detectors

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

  2. 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 ELI NP Workshop Bucharest

  3. Extreme Experimental Conditions FAIR SPIRAL2 SPES REX-ISOLDE EURISOL HI-SIB • Low intensity • High backgrounds • Large Doppler broadening • High counting rates • High g-ray multiplicities High efficiency High sensitivity High throughput Ancillary detectors Need instrumentation ELI NP Workshop Bucharest

  4. Extreme Experimental Conditions FAIR SPIRAL2 SPES REX-ISOLDE EURISOL HI-SIB ELI ? • Low intensity • High backgrounds • Large Doppler broadening • High counting rates • High g-ray multiplicities High efficiency High sensitivity High throughput Ancillary detectors Need instrumentation ELI NP Workshop Bucharest

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

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

  7. Identified interaction points (x,y,z,E,t)i Ingredients of Gamma–Ray Tracking 1 4 Highly segmented HPGe detectors Reconstruction of tracks evaluating permutations of interaction points Pulse Shape Analysisto decomposerecorded waves · · 3 2 Digital electronics to record and process segment signals Reconstructed gamma-rays ELI NP Workshop Bucharest

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

  9. Pulse Shape Analysis Concept A3 A4 A5 (10,10,46) B3 B4 B5 (10,30,46) C3 C4 C5 y B4 C4 CORE measured D4 x A4 F4 E4 791 keV deposited in segment B4 z = 46 mm ELI NP Workshop Bucharest

  10. Pulse Shape Analysis Concept A3 A4 A5 B3 B4 B5 (10,10,46) C3 C4 C5 y B4 C4 CORE measuredcalculated D4 x A4 F4 E4 791 keV deposited in segment B4 z = 46 mm ELI NP Workshop Bucharest

  11. Pulse Shape Analysis Concept A3 A4 A5 B3 B4 B5 (10,15,46) C3 C4 C5 y B4 C4 CORE measuredcalculated D4 x A4 F4 E4 791 keV deposited in segment B4 z = 46 mm ELI NP Workshop Bucharest

  12. Pulse Shape Analysis Concept A3 A4 A5 B3 B4 B5 (10,20,46) C3 C4 C5 y B4 C4 CORE measuredcalculated D4 x A4 F4 E4 791 keV deposited in segment B4 z = 46 mm ELI NP Workshop Bucharest

  13. Pulse Shape Analysis Concept A3 A4 A5 B3 B4 B5 (10,25,46) C3 C4 C5 y B4 C4 CORE measuredcalculated D4 x A4 F4 E4 791 keV deposited in segment B4 z = 46 mm ELI NP Workshop Bucharest

  14. Pulse Shape Analysis Concept A3 A4 A5 B3 B4 B5 (10,30,46) C3 C4 C5 y B4 C4 CORE measuredcalculated D4 x A4 F4 E4 791 keV deposited in segment B4 z = 46 mm ELI NP Workshop Bucharest

  15. Pulse Shape Analysis Concept Result of Grid Searchalgorithm R. Venturelli A3 A4 A5 B3 B4 B5 (10,25,46) C3 C4 C5 y B4 C4 CORE measuredcalculated D4 x A4 F4 E4 791 keV deposited in segment B4 z = 46 mm ELI NP Workshop Bucharest

  16. Pattern of hits Angle/Energy Isolated hits E1st = Eg– 2 mc2 Probability of interaction depth Interaction/Reconstruction Algorithms ~ 100 keV ~1 MeV ~ 10 MeV g-ray energy Photoelectric Compton Scattering Pair Production Algorithms: ClusterTracking, FuzzyTracking, BackTracking, …Reconstruction efficiency limited by Position resolution and Compton profile. ELI NP Workshop Bucharest

  17. A high multiplicity event Eg= 1.33 MeV Mg = 30 27 gammas detected -- 23 in photopeak16 reconstructed -- 14 in photopeak Pulse Shape Analysis Concept Idealized configuration to determinemaximum attainable performance. Ri = 15 cmRo = 24 cm 230 kg of Ge Events simulated using GEANT4 Response of shell at 1.33 MeV: eph = 70% P/T = 77% Reconstruction by Cluster-Tracking Packing Distance: 5 mm Position Resolution: 5 mm (at 100 keV) D. Bazzacco ELI NP Workshop Bucharest

  18. Possible Array Configurations A180 is AGATA’s choice 120 crystals 180 crystals GRETA is for A120C4 ELI NP Workshop Bucharest

  19. The Advanced GAmma Tracking Array Requirements efficiency, energy resolution, dynamic range, angular resolution, timing, counting rate, modularity, angular coverage, inner space ELI NP Workshop Bucharest

  20. 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 Total weight of the 60 clusters of the AGATA-180 configuration ~2.5 tons Mounted on a self-supporting structure ELI NP Workshop Bucharest

  21. Asymmetric AGATA Triple Cryostat - integration of 111 high resolution spectroscopy channels - cold FET technology for all signals Challenges: - mechanical precision - heat development, LN2 consumption - microphonics - noise, high frequencies @1.3 MeV @ 60 keV FWHM [keV] Core 2.10 keV @ 1.3 MeV 1.20 keV @ 60 keV ELI NP Workshop Bucharest

  22. detector detector GTS Preamps Preamps Digitizers Digitizers 7.4 GB/s/det Local processing Local processing 100 MB/s/det PSA PSA 5 MB/s/det Event Builder Tracking On line… Storage … Electronics and DAQ … Fully synchronous system with global100 MHz clock and time-stampdistribution (GTS) clk Digital preamplifier Digitizers: 100 Ms/s, 14 bit Optical fiber read-out of full datastream to pre-processing electronics Local processing triggered by Ge commoncontact. Determine energy and isolate ~ 600 ns of signal around rise-time @ 50 kHz Buffers of time-stamped local events sentto PSA to extract position of interactions Trigger-less system. Global trigger possible. Global event builder and software trigger On-line gamma-ray tracking Control and storage (~1 TB/year), … ELI NP Workshop Bucharest

  23. 5 ClustersDemonstrator The Phases of AGATA 1 Our days Peak efficiency 3 – 8 % @ Mg = 1 2 – 4 % @ Mg = 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 ELI NP Workshop Bucharest

  24. 15 Clusters 1p b = 0 b = 0.5 The Phases of AGATA 2 Near future Recoil velocity The first “real” tracking array To be used at FAIR-HISPEC, SPIRAL2, SPES, … ELI NP Workshop Bucharest

  25. 45 Clusters3p The Phases of AGATA 3 Far future Efficient as a 120 ball (20% at high g multiplicity) Ideal for FAIR and EURISOL ELI NP Workshop Bucharest

  26. 60 Clusters4p The Phases of AGATA 4 Remote future Full ball / full performance Ideal to study extreme deformations and the most exotic nuclear species ELI NP Workshop Bucharest

  27. 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 % @ Mg = 1 Eff. 2 – 4 % @ Mg = 30 Full ACQonline PSA and g–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 ELI NP Workshop Bucharest

  28. First in–beam Test at LNL • Week 12 (March 16-22) • 30Si(@70MeV)+12C 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 ELI NP Workshop Bucharest

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

  30. Doppler Broadening and Position Res. 12.5 keV 40K 1823 keV b~ 5% 11:4217/03/2009 full detector segments (17.7 keV) PSA+tracking Full optimization and analysis – 1 month our target online ELI NP Workshop Bucharest

  31. 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 • Compton imagingof a radioactive source • inverse tracking – from the first 2 interaction points get the position of the source E1 q E2 target g ray Compton scattering E1 E2 q g-source g ray F. Recchia ELI NP Workshop Bucharest

  32. Principles of Compton Imaging q [deg] ELI NP Workshop Bucharest

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

  34. Experimental Setup at LNL Digital DAQ system provided by IFIN – HH Bucharest • 10 x TNT2 NIM Digitizer boards from CAEN with 4ch 14bit /100MHz AGATA prototype detector (one symmetric capsule) 60Co source ELI NP Workshop Bucharest

  35. Comparison with MC Simulations After PSA qprofile of experimental image Projections Experiment q [deg] MC peak FWHM[deg] 5.2 f [deg] position resolution FWHM[mm] fprofile of experimental image Monte Carlo + 5 mm position resolution q [deg] MC peak FWHM[deg] 4.7 position resolution FWHM[mm] ELI NP Workshop Bucharest

  36. 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 60Co, 152Eu and 137Cs • their positions simulate the beam-dump, the beam line and the target M. Doncel & F. Recchia ELI NP Workshop Bucharest

  37. Results E1 = 1173 keV E2 = 1332 keV a) • Spectra of the gamma radiation • assigned to each source position • with the algorithm • Spectra assignment • a) corresponds to the 60Co position • b) corresponds to the 137Cs position • c) corresponds to the 152Eu position • promising results • need more refinement of the method b) E = 661 keV c) E = 344 keV ELI NP Workshop Bucharest

  38. Outlook To exploit the present and future facilities fully and most efficiently, advanced instrumentation and detection equipment is required – NuPECC recommendation The 4p-array of highly segmented Ge detectors AGATA for g-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 assumptionsof the AGATA spectrometer, confirming the feasibility of g-ray tracking AGATA will have astrong impact on nuclear structure studies : lifetime measurements of nuclear states down to fs, angular distribution and polarization measurements Is AGATA or part of it of interest for the ELI project? ELI NP Workshop Bucharest

  39. 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, Camerino, Napoli, Genova Poland: Krakow, Swierk, Warsaw Romania: Bucharest Sweden: Lund, Stockholm, Uppsala Turkey: Ankara, Istanbul UK: Daresbury, Brighton, Keele, Liverpool, Manchester, Paisley, Surrey, York ELI NP Workshop Bucharest

  40. Outlook ELI NP Workshop Bucharest

  41. First in–beam test with STC Position resolution extracted through a comparison to detailed Monte Carlo simulations (FWHM vs. pos. resolution) Symmetric triple cluster ~5.2 mm 4.8 keV 11 keV experiment performed at IKP of Cologne 32 keV Silicon detector ELI NP Workshop Bucharest

  42. 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→ 1fm) • 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 ELI NP Workshop Bucharest

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