The Advanced Gamma Tracking Array detector characterisation http://www.gsi.de/agata/ Andy Boston ajboston@liv.ac.uk
Ingredients of γ-tracking Ulaanbaatar Conference on Nuclear Physics and Applications γ Highly segmented HPGe detectors Digital electronics to record and process segment signals Identified interaction points (x,y,z,e,t) i Pulse Shape Analysis to decompose recorded waves 2 3 4 Reconstruction of tracks e.g. by evaluation of permutations of interaction points 3 e e 3 θ Eγ Eγ 2 0 2 Eγ θ 2 e 2 reconstructed γ-rays
AGATA st symmetric capsule Hexaconical Ge crystals 90 mm long 80 mm max diameter 36 segments Al encapsulation 0.6 mm spacing 0.8 mm thickness 37 vacuum feedthroughs
Detector assembly
EU Workshop Padua Italy 2007
AGATA detector status Symmetric detectors 3 delivered Asymmetric detectors 9 ordered (9 accepted, 4 in test, 2 not accepted, 4 to be delivered) Preamplifiers available Core (Cologne); Segment (Ganil & Milano) Test cryostats for characterisation 5 delivered Triple cryostats 5 ordered complete, 2 being assembled, 2 ordered
B002 FWHM [kev].6.4.2 0.8 0.6.6 0.4.4 0.2.2 59,6 kev Single 59.6 kev Triple Specification low energy 3 332,5 kev Single 332,5 kev Triple Specification high energy 2.5 2.5 3 59.6 kev Single 59.6 kev Triple Specification low energy 332,5 kev Single 332,5 kev Triple Specification high energy 0.5 2.5 0 2 0 C002 FWHM [kev] A4 A5A6 B B2B3 B4 B5B6 C C2C3 C4 C5C6 D D2D3 D4 D5D6 E E2E3 E4 E5E6 F F2F3 F4 F5F6 Core A A2A3 A4 A5A6 B B2B3 B4 B5B6 C C2C3 C4 C5C6 D D2D3 D4 D5D6 E E2E3 E4 E5E6 F F2F3 F4 F5F6.5 3 59,6 kev Single 59,6 kev Triple Specification low energy 332,5 kev Single 332,5 kev Triple Specification high energy 0.5 2.5 0 2 A4 A5A6 B B2B3 B4 B5B6 C C2C3 C4 C5C6 D D2D3 D4 D5D6 E E2E3 E4 E5E6 F F2F3 F4 F5F6 Core A A2A3 A4 A5A6 B B2B3 B4 B5B6 C C2C3 C4 C5C6 D D2D3 D4 D5D6 E E2E3 E4 E5E6 F F2F3 F4 F5F6 A A2A3 A A2A3 Core Core 0.8 0.6.6 0.4.4 0.2.2 0.5 0.5 0 A4 A5A6 B B2B3 B4 B5B6 C C2C3 C4 C5C6 D D2D3 D4 D5D6 E E2E3 E4 E5E6 F F2F3 F4 F5F6 Core A A2A3 A4 A5A6 B B2B3 B4 B5B6 C C2C3 C4 C5C6 D D2D3 D4 D5D6 E E2E3 E4 E5E6 F F2F3 F4 F5F6 A A2A3 Core 0.8 0.6 0.4 0.2 0 Triple Cluster Energies: Single vs Triple Resolution 60keV line Resolution.33MeV line A00 FWHM [kev]
Ingredients of γ-tracking γ Highly segmented HPGe detectors Digital electronics to record and process segment signals Identified interaction points (x,y,z,e,t) i Pulse Shape Analysis to decompose recorded waves 2 3 4 Reconstruction of tracks e.g. by evaluation of permutations of interaction points 3 e e 3 θ Eγ Eγ 2 0 2 Eγ θ 2 e 2 reconstructed γ-rays
Detector Characterisation and PSA Calibrate detector response function Comparison of real and calculated pulse shapes Coincidence scan for 3D position determination Validate codes How well your basis fits your real data
AGATA detector scanning AGATA PSD8 Glasgow
Azimuthal Position Information Image Charge Asymmetry (ICA) ICA = A A anticlockwise anticlockwise + A A clockwise clockwise
Depth Information Vertical Image Charge Asymmetry Sectors C and D ICA = A A above above + A A below below Sectors C and D Back view
AGATA Coincidence scanning
AGATA Coincidence scanning 6 radial scans + 4 azimuthal scans Line 3 Line 2 Line Line 6 Line 4 Line 8 Azimuth 3 Line 7 F Line 8 Line 5 A Azimuth 4 E Line 9 0 o Azimuth 2 Line 7 Line 3 B D Azimuth C Line 6 Line 2 Line Line 0 Line 4 Line 5 r,θ grid adopted 200 positions
Azimuthal detector sensitivity r = 24mm z = 7.3mm θ = 7.9 o A B F C E D 0 o
Electric Field Simulations : MGS I Geometry II Potential Elec field III Drift velocities AGATA symmetric crystal simulation IV Weighting fields Electric field simulations have been performed and detailed comparisons have been made with experimental pulse shape data.
Superpulse generation
Experiment vs Theory Performance
Status of the PSA 3 types of codes: Whole crystal with multi-hits per segment Genetic algo. (Padova, Munich) Swarm algo. (Munich) Adaptative grid search (Padova) Matrix method (Orsay) Single-hit in one segment Binary search (Darmstadt) Neural network (Munich, Orsay) Determination of the number of hits Recursive subtraction (Milan) Matrix method (Orsay)
Pulse-Shape Analysis: current status Results from the analysis of an in-beam test with the first triple module, e.g. Doppler correction of gamma-rays using PSA results d( 48 Ti,p) 49 Ti, v/c ~6.5% counts per channel 20000 5000 0000 5000 E = 382 kev γ Detector fwhm 32 kev PSA fwhm 5 kev Segment fwhm 3 kev 0 340 360 380 400 420 energy [kev] Results obtained with Grid Search PSA algorithm (R.Venturelli et al.) Position resolution ~4.4mm
The Advanced Gamma Tracking Array detector characterisation http://www.gsi.de/agata www.gsi.de/agata/ Andy Boston ajboston@liv.ac.uk