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Compton imaging with AGATA and SmartPET for DSPEC

Compton imaging with AGATA and SmartPET for DSPEC. Steven Moon , A.J. Boston, H. Boston, J. Cresswell, L. Harkness, D. Judson, P.J. Nolan. PSD9, Aberystwyth, Wales 12-16 th September 2011. • Overview. DSPEC SmartPET AGATA Compton reconstruction Pulse Shape Analysis (PSA)

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Compton imaging with AGATA and SmartPET for DSPEC

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  1. Compton imaging with AGATA and SmartPET for DSPEC Steven Moon, A.J. Boston, H. Boston, J. Cresswell, L. Harkness, D. Judson, P.J. Nolan PSD9, Aberystwyth, Wales 12-16th September 2011

  2. • Overview • DSPEC • SmartPET • AGATA • Compton reconstruction • Pulse Shape Analysis (PSA) • AGATA B009 + SmartPET 1 – A DSPEC test bed • Results • Further work

  3. • DSPEC – What is it? • DESPEC (DEcay SPECtroscopy) is a spectrometer designed to analyse the decay of exotic nuclei • Will sit at focal plane of FAIR (Facility for Antiproton and Ion Research), Germany • DSPEC consists of (a) a particle tracker, (b) a pixelated implantation detector (AIDA), surrounded by (c) gamma tracking detector array • Configuration of tracking detectors is still under consideration (S. Tashenov, J. Gerl, NIM A 586 (2008) 224-228)

  4. • DSPEC – Why is it needed? • Background rejection Imaging determines pixel of origin in AIDA, which coupled to other tagging signal, reduces background by a factor of 10 • Prompt flash reduction High granularity = quick recovery from prompt gamma flash  higher count rates and less dead time achievable • Geometry coverage Designed for AIDA  excellent solid angle coverage

  5. • AGATA B009 + SmartPET1 – A DSPEC testbed

  6. • SmartPET Double Sided HPGe Strip Detectors • 60mm x 60mm x 20mm active area • 7mm x 20mm guard ring • 12 x 12 orthogonal strips • - 5mm pitch • - 5mm x 5mm x 20mm voxels • 1mm Aluminium entrance window • Thin contact technology • Fast charge sensitive preamplifiers Energy resolution (FWHM): 1.5 keV@122 keV & 3.25keV@511keV Intrinsic photopeak effic. - 19% at 511keV

  7. • AGATA • AGATA – Advanced GAmmaTracking Array • 180 Coaxial HPGe Detectors, tapered to asymmetric hexagonal end → 36-fold Segmentation • 3 types of AGATA detector (all asymmetric) • RED most asymmetric • GREEN • BLUE least asymmetric • Arranged into ‘ball’, i.e. 4π ‘Spherical Honeycomb’ structure, around beam-target interaction position • Final array will consist of 60 ‘Triple-clusters’ 6 5 4 3 D 2 C E 1 F B A (Images adapted from M. R. Dimmock, PhD Thesis, 2008)

  8. • Liverpool Scan Table • Scan detector on 1mm2 grid with collimated ɣsource • Demand full photon energy deposited in single pixel/segment (Image adapted from M. R. Dimmock, PhD Thesis, 2008)

  9. AC01 AC12 • SmartPET – Detector structure DC12 DC1 • 60 keV collimated gamma rays with 2 minutes of data per position.

  10. • AGATA– Detector structure

  11. • AGATA– Detector structure

  12. • Compton Reconstruction AGATA θ SmartPET θ ɣ-ray Source

  13. • Pulse Shape Analysis - Risetime • To accurately obtain θ, we need accurate interaction positions in each detector → Pulse Shape Analysis → Use rise time of pulse to determine radial interaction position (or depth of interaction in SmartPET) 1 2 2 ns samples (Images adapted from C. Unsworth, Private Comm., 2010)

  14. e e e e e h h h h h • Pulse Shape Analysis – Image Charge Asymmetry ICA varies as a function of lateral interaction position

  15. • AGATA B009 + SmartPET1 – A DSPEC testbed

  16. • AGATA B009 + SmartPET1 – A DSPEC testbed

  17. • AGATA B009 + SmartPET1 – Results (Preliminary) • 137Cs point source – (effectively) a monoenergetic gamma emitter @ 662 keV • Data collected at 2 positions independently, 6 cm apart • 19116 full energy events reconstructed at position 1 xFWHM = 55mm yFWHM = 44mm

  18. • AGATA B009 + SmartPET1 – Results (Preliminary) • 137Cs point source – (effectively) a monoenergetic gamma emitter @ 662 keV • Data collected at 2 positions independently, 6 cm apart • 19116 full energy events reconstructed at position 1 • 11083 full energy events reconstructed at position 2 yFWHM = 46mm xFWHM = 44mm

  19. • AGATA B009 + SmartPET1 – Results (Preliminary)

  20. • AGATA B009 + SmartPET1 – Results (Preliminary) • Data collected for 3 x point sources at same time - 137Cs, 152Eu and 60Co • Sources placed in isosceles triangle configuration approximately 3.5 to 5 cm apart • Gate on energy and image • Normalise and sum

  21. • AGATA B009 + SmartPET1 – Further work • Implement Pulse Shape Analysis to improve resolution of Compton reconstruction (Biggest improvement expected from AGATA PSA) • Simulate experiment using GAMOS (Geant 4 derivative) and compare with experiment

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