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Radiation Protection & Shielding
The Radiation Protection and Shielding Division is developing and promoting radiation protection and shielding aspects of nuclear science and technology — including interaction of nuclear radiation with materials and biological systems, instruments and techniques for the measurement of nuclear radiation fields, and radiation shield design and evaluation.
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Nuclear Science and Engineering
Fusion Science and Technology
What is involved in radiation protection at accelerator facilities?
Particle accelerators have evolved from exotic machines probing hadron interactions to understand the fundamentals of our world to widely used instruments in research and for medical and industrial use. For research purposes, high-power machines are employed, often producing secondary particle beams through primary beam interaction with a target material involving many meters of shielding. The charged beam interacts with the surrounding structures, producing both prompt radiation and secondary radiation from activated materials. After beam termination, some parts of the facility remain radioactive and potentially can become radiation hazards over time. Radiation protection for accelerator facilities involves a range of actions for operation within safe boundaries (an accelerator safety envelope). Each facility establishes fundamental safety principles, requirements, and measures to control radiation exposure to people and the release of radioactive material in the environment.
Brock Jolicoeur, Norbert Hugger, David Medich
Nuclear Technology | Volume 209 | Number 11 | November 2023 | Pages 1819-1825
Regular Research Article | doi.org/10.1080/00295450.2023.2204988
Articles are hosted by Taylor and Francis Online.
We investigate the image quality and beam intensity of thermal neutron radiography after replacing a standard single-channel neutron collimator with a compact array of microcollimators. In this study, the MCNP6 Monte Carlo computer code was used to simulate a 2 × 2-cm-area isotropic thermal neutron source, which then was collimated by an array of micron-sized neutron collimators that measured 29.8 μm in diameter and with lengths that varied from 0.6 to 3 mm. These microcollimators were spaced 30 μm apart and assembled into a 2 × 2-cm array.
The image quality of the neutron beams produced by the resulting collimator arrays was assessed by imaging the edge of a very thin (~0.01-mm) gadolinium foil to obtain the image Modulation Transfer Function (MTF). The MCNP6 resulting flux map from each simulation then was converted into a grayscale .tiff image and the image’s resulting MTF obtained using the ImageJ computer program with the imaging beam geometric unsharpness, which is a limiting factor in the image resolution determined at the 10% value of the MTF curve.
In this study, we found that a 2 × 2× 0.298-cm microcollimator, corresponding to a length-to–hole diameter ratio of 100:1 and a collimator length of 2.98 mm produced a beam with a geometric unsharpness of 32 μm. Compared to a standard single-channel collimator with a 2 × 2-cm aperture, the single-channel collimator would need to be 660 cm long to produce an equivalent geometric sharpness. Yet because of its shorter length, the imaging beam intensity from our 2.98-mm-thick collimator array was approximately 50 times greater than that of an equivalent single-channel collimator.