A source biasing and variance reduction technique for Monte Carlo radiation transport modeling of emission tomography problems

Kilby, Seth; Jin, Zhongmin; Avachat, Ashish; Kanies, Bryant; Woolstenhulme, Nicholas; Lee, Hyoung-Koo; Graham, Joseph

doi:10.1007/s10967-019-06457-1

Cited by 8 publications

(4 citation statements)

References 10 publications

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“…The geometry and material composition of the collimator should be carefully considered during the beginning stages of creating a spectroscopic system since they have a significant impact on the system's performance. MC simulations are frequently used to produce outcomes with the potential for high accuracy [8] [9] [10]. For instance, for an isotopically emitting point source positioned directly in front of the collimator opening, the likelihood of a gamma ray reaching the opposite opening is on the order of 10 −9 for a collimator with a square slit that is 80 cm long and 0.1 cm wide.…”

Section: Introductionmentioning

confidence: 99%

“…As a result, MC approaches need a lot of photons to be sampled, which can be time-consuming if no special variance reduction techniques are used, such as those proposed by. The Monte Carlo radiation transport code MCNP6 is used to model a mono-directional source, and correction factors are added to account for the effects of a cylindrical aperture and solid-angle effects of isotropic emission [10] [11].…”

Section: Introductionmentioning

confidence: 99%

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Assessment of Modeling Collimator Designs for Gamma-Ray Transmission of Uranium Oxide Spectrometry Using HPGe Detectors

El-Tayebany,

Elbegawy

2023

WJET

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Many scientific domains use gamma-ray spectrometry, but non-destructive gamma scanning and gamma emission tomography of radioactive fuel in particular. In the experimental setting, a collimator is frequently employed to focus on a particular location of interest in the fuel. Predictive models for the transmitted gamma-ray intensity through the collimator are required for both the optimization of instrument design and the planning of measurement campaigns. Gamma-ray transport accuracy is frequently predicted using Monte Carlo radiation transport methods, but using these tools in low-efficiency experimental setups is challenging due to the lengthy computation times needed. This study focused on the full-energy peak intensity that was transmitted through several collimator designs, including rectangle and cylinder. The rate of photons arriving at a detector on the other side of the collimator was calculated for anisotropic source of SNM (U 3 O 8 ). Some geometrical assumptions that depended on the source-to-collimator distance and collimator dimensions (length, radius or length, height, and width) were applied to achieve precise findings.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Assessment of Modeling Collimator Designs for Gamma-Ray Transmission of Uranium Oxide Spectrometry Using HPGe Detectors

El-Tayebany,

Elbegawy

2023

WJET

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“…The performance of a spectroscopic system is strongly impacted by the collimator design and therefore its geometric layout and material composition should be carefully evaluated during the initial stages of designing a spectroscopy system. Monte Carlo (MC) simulations are often used to provide results with the potential for good accuracy [8][9][10] . However, the MC technique exhibit the disadvantage of requiring large computational efforts to obtain sufficient statistical precision, especially if the collimator slit is narrow and long, causing a low probability for gamma rays to reach the detector.…”

Section: Introductionmentioning

confidence: 99%

“…For the parts of a fuel object that are not directly in front of the opening, or further away, the probability of penetration can be substantially smaller. Consequently, MC techniques require a large number of sampled photons and may become prohibitively time consuming, unless dedicated variance reduction schemes are applied, such as suggested by [10]. In [10], a mono-directional source is modelled with the Monte Carlo radiation transport code MCNP6.2, and correction factors are introduced to solid-angle effects of isotropic emission and effects of finite volume in view of a cylindrical aperture.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of gamma-ray transmission through rectangular collimator slits for application in nuclear fuel spectrometry

Senis

Rathore

Anastasiadis

et al. 2021

Nuclear Instruments and Methods in Physics Research Section A:

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Gamma-ray spectrometry is widely applied in several science fields, and in particular in non-destructive gamma scanning and gamma emission tomography of irradiated nuclear fuel. Often, a collimator is used in the experimental setup, to selectively interrogate a region of interest in the fuel. For the optimization of instrument design, as well as for planning measurement campaigns, predictive models for the transmitted gamma-ray intensity through the collimator are needed. Commonly, Monte Carlo radiation transport tools are used for accurate prediction of gamma-ray transport, however, the long computation time requirements when used in low-efficiency experimental setups present challenges.In this work, the full-energy peak intensity transmitted through a rectangular collimator slit was examined. A uniform planar surface source emitting isotropically was considered, and the rate of photons reaching an ideal counter plane on the opposite side of the collimator was evaluated by analytical integration. To find a closed-form primitive function, some idealizations were required, and thereby parametric models were obtained for the optical field of view, dependent on slit dimensions (length, height and width) and source-to-collimator distance. It was shown that the count rate in the detector is independent of the collimator-to-source distance. For contributions from outside the optical field of view, where a closed-form expression cannot be found, instead fast numerical integration methods were proposed.The results were validated using the Monte Carlo code MCNP6.2. For the analytical method, deviations were larger, the shorter the collimator, with up to 25% of underestimation obtained for the shortest examined collimator of 10 cm length. However, the longer the collimator, the better the observed agreement. This accuracy is deemed to be sufficient for instrument design and measurement planning, where often the order of magnitude of the count rate is not a priori known. For the numerical method, the results showed an agreement within 3% for all evaluated collimator settings.The methods are planned for use in iterative optimization routines in the design of Gamma Emission Tomography devices, as well as for the prediction of gamma spectra obtained in the planning of fuel inspections. An application of the proposed method was demonstrated in spectrum prediction for a short cooling-time fuel rod test from the Halden reactor.

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Active interrogation of Special Nuclear Material containers using AmBe quasi-forward biased directional source and PGNAA

Paaren

Kilby

Lee

2020

Applied Radiation and Isotopes

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A source biasing and variance reduction technique for Monte Carlo radiation transport modeling of emission tomography problems

Cited by 8 publications

References 10 publications

Assessment of Modeling Collimator Designs for Gamma-Ray Transmission of Uranium Oxide Spectrometry Using HPGe Detectors

Assessment of Modeling Collimator Designs for Gamma-Ray Transmission of Uranium Oxide Spectrometry Using HPGe Detectors

Evaluation of gamma-ray transmission through rectangular collimator slits for application in nuclear fuel spectrometry

Active interrogation of Special Nuclear Material containers using AmBe quasi-forward biased directional source and PGNAA

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