Application of Unfolding Technique to HPGe Detector Using Response Functions Calculated with the EGS4 Monte Carlo Code

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概要

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• The EGS4 Monte Carlo simulation technique was used to obtain the energy spectra of photons arriving at a detector from the pulse height distributions measured by the same detector. First, the measured pulse height distribution for incident photons from several radiation sources such as ^<60>Co, ^<137>Cs, ^<152>Eu and ^<207>Bi with a collimator are compared with those calculated using the EGS4 code to investigate the feasibility of the simulation. The comparison showed good agreement of 98.7% for ^<60>Co, 92.5% for ^<207>Bi on the total counts. Second, the pulse height distributions were measured in the open space and then unfolded. The measurement of the distributions was done with changing the source to detector distance (SDD) from 10cm to 100cm for ^<60>Co and ^<137>Cs respectively. In the unfolding process, response functions of a high purity Ge (HPGe) detector were calculated using the EGS4 code. The calculated pulse height distributions were then normalized to the measured ones at the peaks of the incident photon energies. The ratio of the sum of counts of the main peaks to the total count in the unfolded spectra for ^<60>Co varied from 5.4 to 5.7 times greater than those in the measured pulse height distributions, while from 2.5 to 2.9 times for ^<137>Cs. Electron contribution to the unfolded spectra for ^<137>Cs decreased as the source to detector distance increased, becoming negligible above 50cm. The pulse height distributions at the center of the reference plane at 100cm from the ^<60>Co and ^<137>Cs dummy sources located inside each irradiator were also measured and unfolded to obtain the real pulse height distribution. In the unfolded spectra, the photons scattered from the surrounding materials were reduced to approximately one fourth of those measured in the open space due to the small size of apertures of the irradiators. The ratio of the sum of counts for the main peaks to the total count was larger than those in the measured pulse height distributions by the factor of 5.0 for ^<60>Co and 3.4 for ^<137>Cs. The uncertainties estimated in the unfolding processes were around 0.1% for ^<60>Co and 0.07% for ^<137>Cs.

• 日本放射線影響学会の論文
• 2006-03-31

著者

• Chun Kook

  Center For Ionizing Radiation Korea Res. Inst. Of Standards And Sci.

• Hah Suck

  Ionizing Radiation Group Division Of Materials Evaluation And Chemistry Korea Research Institute Of

• Kim Hyun

  Ionizing Radiation Group Division Of Materials Evaluation And Chemistry Korea Research Institute Of

• Yoo Gwang

  Div. Of General Education Daebul Univ.

• CHUN Kook

  Ionizing Radiation Group, Division of Materials Evaluation and Chemistry, Korea Research Institute o

• YOO Gwang

  Department of Computer Engineering, Daebul University

関連論文

• Dosimetry Parameters of the IRH10 ^Ir High Dose Rate Brachytherapy Source
• Application of Unfolding Technique to HPGe Detector Using Response Functions Calculated with the EGS4 Monte Carlo Code

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