TY - JOUR
T1 - Ratio of germanium detector peak efficiencies at photon energies of 4.4 and 11.7 MeV
T2 - Experiment versus simulation
AU - Carson, Spencer
AU - Iliadis, Christian
AU - Cesaratto, John
AU - Champagne, Art
AU - Downen, Lori
AU - Ivanovic, Marija
AU - Kelley, John
AU - Longland, Richard
AU - Newton, Joseph R.
AU - Rusev, Gencho
AU - Tonchev, Anton P.
PY - 2010/6/1
Y1 - 2010/6/1
N2 - Full-energy peak efficiencies of germanium detectors are frequently investigated at γ-ray energies below 4 MeV using calibrated radioactive sources, while very accurate peak efficiencies for higher photon energies are essentially non-existent. Peak efficiencies in the energy range of E γ = 4212 MeV are crucial for a number of applications, including nuclear astrophysics measurements of fusion reactions and resonance fluorescence experiments. We report on a novel method, using the 163 keV resonance in the 11 B(p, γ)12C reaction, of measuring accurately the ratio of full-energy peak efficiencies at 4.44 and 11.66 MeV. We derive this ratio for three different detector-target distances (3, 12 and 26cm) directly from measured peak intensities and demonstrate that corrections are small (γ-ray branching ratios, angular correlations, coincidence summing). Our measured full-energy peak efficiency ratios have a precision of 1.4-1.6%. Another important goal of our study was to determine to what precision full-energy peak efficiencies at high γ-ray energies can be predicted using the simulation codes Geant3 and Geant4. We imaged our detector using computed tomography and radiographs in order to extract reliable detector crystal dimensions. Based on these results, extensive computer simulations are performed. We find that the simulation results agree with the measured peak efficiency ratios within an uncertainty of 1.6% for Geant4 and 2.6% for Geant3. Our results are useful for assigning uncertainties when peak efficiencies are extrapolated from low energy data to high energies based on simulations only.
AB - Full-energy peak efficiencies of germanium detectors are frequently investigated at γ-ray energies below 4 MeV using calibrated radioactive sources, while very accurate peak efficiencies for higher photon energies are essentially non-existent. Peak efficiencies in the energy range of E γ = 4212 MeV are crucial for a number of applications, including nuclear astrophysics measurements of fusion reactions and resonance fluorescence experiments. We report on a novel method, using the 163 keV resonance in the 11 B(p, γ)12C reaction, of measuring accurately the ratio of full-energy peak efficiencies at 4.44 and 11.66 MeV. We derive this ratio for three different detector-target distances (3, 12 and 26cm) directly from measured peak intensities and demonstrate that corrections are small (γ-ray branching ratios, angular correlations, coincidence summing). Our measured full-energy peak efficiency ratios have a precision of 1.4-1.6%. Another important goal of our study was to determine to what precision full-energy peak efficiencies at high γ-ray energies can be predicted using the simulation codes Geant3 and Geant4. We imaged our detector using computed tomography and radiographs in order to extract reliable detector crystal dimensions. Based on these results, extensive computer simulations are performed. We find that the simulation results agree with the measured peak efficiency ratios within an uncertainty of 1.6% for Geant4 and 2.6% for Geant3. Our results are useful for assigning uncertainties when peak efficiencies are extrapolated from low energy data to high energies based on simulations only.
KW - Computed tomography
KW - Full-energy peak efficiencies
KW - Gamma-ray spectrometry
KW - HPGe detector
KW - High γ - Ray energy
KW - Monte Carlo simulations
KW - Radiography
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U2 - 10.1016/j.nima.2010.02.128
DO - 10.1016/j.nima.2010.02.128
M3 - Article
AN - SCOPUS:77958468146
SN - 0168-9002
VL - 618
SP - 190
EP - 198
JO - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
JF - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
IS - 1-3
ER -