Advanced GAmma Tracking Array Performance of an AGATA

Advanced GAmma Tracking Array Performance of an AGATA prototype detector estimated by Compton-imaging techniques Francesco Recchia INFN - Legnaro on behalf of the AGATA collaboration

The g-ray spectrometer AGATA Rint = 23 cm 180 HPGe Design values: 5 mm of position resolution assumed Rext = 32 cm Efficiency: 43% (Mg=1) 28% (Mg=30) Peak/Total: 58% (Mg=1) 49% (Mg=30) today’s arrays ~10% today ~55% 5% 40% Angular Resolution: ~1º FWHM (1 Me. V, v/c=50%) ~ 6 ke. V today o o Triple cluster o ~40 ke. V 180 large volume 36 -fold segmented Ge crystals packed in 60 triple-clusters Digital electronics and sophisticated Pulse Shape Analysis algorithms Operation of Ge detectors in position sensitive mode for g-ray tracking

Ingredients of g-ray tracking Identified interaction points 1 Highly segmented HPGe detectors · · ·· g · · · (x, y, z, E)i Pulse Shape Analysis to decompose recorded waves 4 Reconstruction of scattering sequence from Compton vertices 3 2 Digital electronics to record and process segment signals Reconstructed gamma-rays

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 A 4 E 4 F 4 z = 46 mm x

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 D 4 A 4 E 4 F 4 z = 46 mm x

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 D 4 A 4 E 4 F 4 z = 46 mm x

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 D 4 A 4 E 4 F 4 z = 46 mm x

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 D 4 A 4 E 4 F 4 z = 46 mm x

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 D 4 A 4 E 4 F 4 z = 46 mm x

Pulse Shape Analysis concept A 3 A 4 A 5 B 3 B 4 B 5 C 3 C 4 C 5 Result of Grid Search algorithm (10, 25, 46) y CORE C 4 measured calculated 791 ke. V deposited in segment B 4 D 4 A 4 E 4 F 4 z = 46 mm x

The position resolution required for the AGATA detectors Simulations suggest that the overall performance depends on the attainable position resolution A test-beam experiment has been performed to measure this parameter in realistic experimental conditions

Setup of the in-beam experiment Symmetric triple cluster d(48 Ti, 49 Ti)p BEAM 48 Ti TARGET 48 Ti 100 Me. V + 2 H 220 μg/cm 2 Thickness: 300 μm Si detector DSSSD 32 rings, 64 sectors AGATA symmetric triple-cluster experiment performed at IKP of Cologne Digitizers: 30 XIA DGF 4 c cards 40 MHz 14 bit Silicon detector

Doppler correction using PSA results 32 ke. V Full statistics used

Doppler correction using PSA results 11 ke. V 32 ke. V Full statistics used

Doppler correction using PSA results 4. 8 ke. V 11 ke. V 32 ke. V Full statistics used PSA algorithm: Grid Search

Simulation vs Experiment Recursive Subtraction Matrix Method Miniball Algorithm Grid Search Results obtained with different PSA algorithm

Why Compton imaging? o o o 15 days of beam-time to perform the test experiment 1 year of analysis PSA will be on-line Need for a simpler procedure Need an prompt feed-back from on-line analysis

Compton imaging o In-beam experiment: n o typical conditions of future use E 1 n inverse tracking E 2 target Compton imaging of a radioactive source q E 1 g-source q E 2

Error on Compton identification of source direction from: o Position resolution (axis) o Energy resolution (scattering angle) o Compton profile (scattering angle) angular error [deg] Compton imaging performance scattering angle [deg]

Imaging setup at LNL AGATA prototype detector TNT 2 Digitizers: 4 ch 14 bit 100 MHz 60 Co source

Outline of analysis/simulation DAQ MC Event selection PSA Smearing (position resolution) Image formation Position resolution

Comparison to simulation Simple back-projections MCE+ E res MC ≈ MC + E, p E res + pos res Exp ≈

q profile of experimental image Experiment peak FWHM [deg] q [deg] Comparison to MC simulation position resolution FWHM [mm] f profile of experimental image Monte Carlo + 5 mm position resolution peak FWHM [deg] q [deg] f [deg] 5. 2 4. 7 position resolution FWHM [mm]

CONCLUSIONS o o Position resolution extracted by in-beam experiment and Compton imaging is 5 mm FWHM. This value is in line with the design assumptions of the AGATA spectrometer, confirming the feasibility of g-ray tracking. AGATA will have a huge impact on nuclear structure studies (first phase of AGATA: LNL 2009…) Possible applications of g-ray tracking detectors to imaging.

Basic implementation of LMML 0 1 20 6

Compton imaging application