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DISCRIMINATION METHOD FOR GAMMA RAY DOSES IN NEUTRON FIELDS USING AN IONIZATION CHAMBER WITH ATTENUATION FILTERS
R Ogawara1, M Suda1, T Hagihara1
1National Institute of Radiological Sciences, National Institute for Quantum and Radiological Science and Technology, Chiba, Japan.
Radiation Protection Dosimetry
|February 7, 2019
Summary
This study presents a new method to distinguish fast neutron and gamma ray doses in mixed radiation fields using an ionization chamber and filters. The technique accurately quanties gamma ray contamination, crucial for assessing biological effects of neutrons.
Area of Science:
- Medical Physics
- Radiation Detection and Measurement
- Nuclear Physics
Background:
- Accelerator-driven neutron sources produce mixed radiation fields of fast neutrons and gamma rays.
- Accurate estimation of biological effects from fast neutrons requires precise evaluation of gamma ray dose contamination.
- Existing methods may lack the precision needed for differentiating dose contributions in mixed fields.
Purpose of the Study:
- To develop and validate a novel discrimination technique for separating absorbed doses of fast neutrons and gamma rays.
- To quantify gamma ray dose contributions in neutron fields generated by specific nuclear reactions.
- To establish a reliable method for absorbed dose assessment in mixed radiation environments.
Main Methods:
- Utilized an ionization chamber with varying polyethylene attenuation filters (0-350 mm) to measure dose attenuation.
- Employed a two-component exponential function to fit the dose attenuation curves and distinguish radiation components.
- Validated the technique against reference measurements using CR-39 plastic nuclear track detectors for neutron fields from 9Be(p,n) and 9Be(d,n) reactions.
Main Results:
- The developed technique successfully discriminated between fast neutron and gamma ray absorbed doses.
- Dose attenuation coefficients for fast neutrons showed minimal differences (1.5-1.7%) compared to CR-39 detector results.
- Gamma ray absorbed dose contributions were quantified as 30.2 ± 3.24% for 9Be(p,n) and 20.4 ± 5.16% for 9Be(d,n) reactions.
Conclusions:
- The ionization chamber-based discrimination technique provides accurate separation of fast neutron and gamma ray doses.
- This method is effective for evaluating gamma ray contamination in mixed radiation fields from accelerator-driven sources.
- The findings are critical for precise biological effect estimations and radiation protection protocols in neutron therapy and research.
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