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

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

8. Liverpool Scan Table Scan detector on 1mm 2 grid with collimated ɣ source Demand full photon energy deposited in single pixel/segment (Image adapted from M. R. Dimmock, PhD Thesis, 2008)

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

10. AGATA– Detector structure

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

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

15. AGATA B009 + SmartPET1 – A DSPEC testbed

17. AGATA B009 + SmartPET1 – Results (Preliminary) 137 Cs 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 x FWHM = 55mm y FWHM = 44mm

18. AGATA B009 + SmartPET1 – Results (Preliminary) 137 Cs 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 y FWHM = 46mm x FWHM = 44mm

19. AGATA B009 + SmartPET1 – Results (Preliminary)

20. Data collected for 3 x point sources at same time - 137 Cs, 152 Eu and 60 Co 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