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AGATA detector characterization : Quick 3D scanning system

AGATA detector characterization : Quick 3D scanning system. N. Saito and J. Gerl GSI. Concept. Side detector. Reduce a time to scan by taking data for all required positions at same time Define directions of g -ray by measuring one of 511 keV g -rays from a 22 Na source

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AGATA detector characterization : Quick 3D scanning system

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  1. AGATA detectorcharacterization:Quick 3D scanning system N. Saito and J. Gerl GSI

  2. Concept Side detector • Reduce a time to scan by taking data for all required positions at same time • Define directions of g-ray by measuring one of 511 keV g-rays from a 22Na source • Define interaction position in Ge by measuring a scattering g-ray on the side detector and energy deposit in Ge. 511g Ge Collimator (slits) 511g Collimator (holes) 22Na g source Scinti. Fiber

  3. Simulation 4.5 cm 5 cm • GEANT4 • Ge cylindrical shape • Radius: 4 cm, length: 9cm • 6x6 seg. (1, 1, 1.75, 1.75, 1.75, 1.75 cm) • Collimator surrounding Ge • Pb cylinder • Slits width: 2 mm length: 5 cm • Inner r. = 4.5 cm • Side detector • Scintillator (Plastic, NaI, or BGO) • Source collimator • Pb ball inner r. = 4 cm, thickness 2cm • 9 x 6 holes, f 1 mm • Scint. Fiber • f 0.82 mm, 5 -10 cm length • Edge 4cm from the source (correspond f 2 mm at the Ge surface) 10 cm Slits 2 mm 4 cm Fiber f 0.82 mm

  4. Position distribution : XY plane for each Ge layer

  5. Position distribution : XZ plane for each Ge layer

  6. Rate estimation Condition • 10MBq 22Na source • Detector efficiency from the simulation • Side detector : 12 x 6 BGO (EuroBall inner ball) • Fiber length : 5 cm • Threshold on Fiber energy 100 keV : 0.69 • Energy gate for Ge ~220 keV to reduce multi-interaction events Rate Ge Layer Coincidence events on a reference position [ / day] #1 270 #2 170 #3 100 #4 61 #5 26 #6 12

  7. Investigation • Multiple interaction in a Ge segment • 33% without energy gate on Ge • 15% with energy gate on Ge • 7% with energy gate on Ge and side detector divided • Multiple hit on Fiber detectors • 0.5 % with a Pb ball thickness of 1 cm • 0.4 % with a Pb ball thickness of 2 cm • 0.1 % with a Pb ball thickness of 5 cm • Side detector • Side detector efficiency (relative to BGO case) : 65% NaI, 26% Plastic • Energy above 50 keV : 99% BGO, 85% NaI, 56% Plastic

  8. Discussion • Reference points • 3 rings (q = 4, 8, 12 deg) • Side : 1 or 2 ? • Source position • 10 cm away from detector • Side detectors • BGO or NaI Radii at surface: ~7, 14, 21 mm

  9. Discussion • Reference points • 3 rings (q = 4, 8, 12 deg) • Side : 1 or 2 ? • Source position • 10 cm away from detector • Side detectors • BGO or NaI Radii at surface: ~7, 14, 21 mm

  10. Discussion • Reference points • 3 rings (q = 4, 8, 12 deg) • Side : 1 slit for each sector • Up and down for detailed scanning (4 or 5 steps) ? • Source position • 10 cm away from detector • Side detectors • BGO or NaI Radii at surface: ~7, 14, 21 mm

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