Abstract
To determine the range, spread-out Bragg peak (SOBP) width, and output of a passive-scattering proton beam with a liquid scintillator detector, without the need for quenching correction. The depth-light profiles of 3 beam energies (140, 160, and 180 MeV) with 6 SOBP widths at each energy, produced in a 20 × 20 × 20-cm3 liquid scintillator tank, were collected by a charge-coupled device camera. By defining landmarks on the light signals, measured ranges and SOBP widths were acquired. A linear dependence was found between nominal and measured properties, and calibration factors were obtained by comparing those properties. The daily output stability and reproducibility of the liquid scintillator detector were studied by conducting 8 repeated measurements over 2 weeks in a 60Co beam. The beam ranges were determined with submillimeter accuracy without the need for any correction. The maximum difference between the measured and nominal range was 1.0 mm. The mean difference between the measured and nominal SOBP widths after correction was 0.1 mm (σ = 1.8 mm), with a maximum difference of 3.5 mm. The light output was reproducible with an SD of 0.14%. The method described here makes it possible to quickly and accurately determine the range and SOBP width of a passive-scattering proton beam in a liquid scintillator, without the need for quenching correction. In addition, the detector proved to be reliable over time, showing good output consistency with a high degree of precision.
Highlights
By imaging a large volume of organic scintillator during proton irradiation, it is possible to image proton beams with high spatial resolution in nearly real time
Scintillator detectors exhibit a combination of characteristics, including high spatial resolution, water equivalence, and 3-dimensional dimensionality, which are advantageous for proton beam measurements [1, 2]
Measurements of beam range, spread-out Bragg peak (SOBP) modulation, and beam output are an important component of regular quality assurance for passive-scattering proton facilities
Summary
By imaging a large volume of organic scintillator during proton irradiation, it is possible to image proton beams with high spatial resolution in nearly real time. Scintillator detectors exhibit a combination of characteristics, including high spatial resolution, water equivalence, and 3-dimensional dimensionality, which are advantageous for proton beam measurements [1, 2]. Solid plastic scintillators were used to verify proton beam range [3], and large, liquid-scintillator detectors were used to measure the range and lateral profiles of proton beams [4]. Measurements of beam range, spread-out Bragg peak (SOBP) modulation, and beam output are an important component of regular quality assurance for passive-scattering proton facilities. Bragg peak determining by liquid scintillator wheels makes it difficult to measure these beam properties on a regular basis. Multilayer ionization chambers are useful tools for rapidly performing such measurements, but they are expensive and have relatively coarse spatial resolution
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