In recent years,graphics processing units(GPUs)have been applied to accelerate Monte Carlo(MC)simulations for proton dose calculation in radiotherapy.Nonetheless,current GPU platforms,such as Compute Unified Device Ar...In recent years,graphics processing units(GPUs)have been applied to accelerate Monte Carlo(MC)simulations for proton dose calculation in radiotherapy.Nonetheless,current GPU platforms,such as Compute Unified Device Architecture(CUDA)and Open Computing Language(OpenCL),suffer from cross-platform limitation or relatively high programming barrier.However,the Taichi toolkit,which was developed to overcome these difficulties,has been successfully applied to high-performance numerical computations.Based on the class II condensed history simulation scheme with various proton-nucleus interactions,we developed a GPU-accelerated MC engine for proton transport using the Taichi toolkit.Dose distributions in homogeneous and heterogeneous geometries were calculated for 110,160,and 200 MeV protons and were compared with those obtained by full MC simulations using TOPAS.The gamma passing rates were greater than 0.99 and 0.95 with criteria of 2 mm,2%and 1 mm,1%,respectively,in all the benchmark tests.Moreover,the calculation speed was at least 5800 times faster than that of TOPAS,and the number of lines of code was approximately 10 times less than those of CUDA or OpenCL.Our study provides a highly accurate,efficient,and easy-to-use proton dose calculation engine for fast prototyping,beamlet calculation,and education purposes.展开更多
The coupling between the Monte Carlo (MC) method and geometrical optics to improve accuracy is investigated. The results obtained show improved agreement with previous experimental data, demonstrating that the MC me...The coupling between the Monte Carlo (MC) method and geometrical optics to improve accuracy is investigated. The results obtained show improved agreement with previous experimental data, demonstrating that the MC method, when coupled with simple geometrical optics, can simulate multiple scattering with enhanced fidelity.展开更多
In this paper, multipath temporal spreading distributions of laser pulses are calculated when they travel through the seawater. Individual photon is followed in Monte Carlo calculation A modified Henyey-Greenstein (H...In this paper, multipath temporal spreading distributions of laser pulses are calculated when they travel through the seawater. Individual photon is followed in Monte Carlo calculation A modified Henyey-Greenstein (HG) function is applied to represent the scattering phase function of seawater. This paper proposes a new scaling method, which uses the effective scattering thickness τd to replace the optical thickness used in the traditional scaling technique. This paper compares the temporal spreading distributions of photons on conditions of different attenuation coefficients and target depths. The experiments reveal that these mutual deviations are changing in the range from 0.5% to 5%, so long as the corresponding effective scattering thicknesses τd remains the same. Therefore, a conclusion can be obtained, that the temporal spreading distribution is only dependent on the effective diffusion thickness τd .展开更多
In this paper, an importance sampling maximum likelihood(ISML) estimator for direction-of-arrival(DOA) of incoherently distributed(ID) sources is proposed. Starting from the maximum likelihood estimation description o...In this paper, an importance sampling maximum likelihood(ISML) estimator for direction-of-arrival(DOA) of incoherently distributed(ID) sources is proposed. Starting from the maximum likelihood estimation description of the uniform linear array(ULA), a decoupled concentrated likelihood function(CLF) is presented. A new objective function based on CLF which can obtain a closed-form solution of global maximum is constructed according to Pincus theorem. To obtain the optimal value of the objective function which is a complex high-dimensional integral,we propose an importance sampling approach based on Monte Carlo random calculation. Next, an importance function is derived, which can simplify the problem of generating random vector from a high-dimensional probability density function(PDF) to generate random variable from a one-dimensional PDF. Compared with the existing maximum likelihood(ML) algorithms for DOA estimation of ID sources, the proposed algorithm does not require initial estimates, and its performance is closer to CramerRao lower bound(CRLB). The proposed algorithm performs better than the existing methods when the interval between sources to be estimated is small and in low signal to noise ratio(SNR)scenarios.展开更多
The small angle neutron scattering (SANS) instrument is presently being constructed at Chinese Spal- lation Neutron Source (CSNS) in China, and the biological shielding design is needed to prevent the instrument f...The small angle neutron scattering (SANS) instrument is presently being constructed at Chinese Spal- lation Neutron Source (CSNS) in China, and the biological shielding design is needed to prevent the instrument from causing excessive dose rates in accessible locations. In this paper, the study of shielding design for SANS that relies on Monte Carlo simulation is introduced. Beam line shielding calculations are performed considering both scenarios of closed versus open TO chopper. The basic design scheme of the beam stop is discussed. The size of the TO chopper rotor is also estimated.展开更多
Purpose With the aim of determining mass yield distributions of primary fission products,a one-arm spectrometer was developed based on kinetic energy and time-of-flight correlation measurement technique.Methods An axi...Purpose With the aim of determining mass yield distributions of primary fission products,a one-arm spectrometer was developed based on kinetic energy and time-of-flight correlation measurement technique.Methods An axial grid ionization chamber(GIC)was designed for energy detecting.In order to minimize energy losses and straggling,a thin silicon nitride film with a thickness of 100 nm was performed as the entrance window of the GIC.The energy resolution is 0.38%for 80 MeV ^(63)Cu particles.Two-timing detectors based on the detection of secondary emission electrons by microchannel plates(MCPs)constitute the time pick-off system,and the time-of-flight resolution is better than 200 ps(FWHM)measured with a ^(241)Amαsource.With a flight path length of 47.6 cm,the path length resolution is 0.21%.Results and conclusion The first result of mass distribution from ^(252)Cf spontaneous fission was reported.Energy losses of fragments in dead layers of the spectrometer were corrected event-by-event depend on the Monte Carlo calculation.The mass resolution for light fission fragments peak A107 amu is 1.3 aum.展开更多
基金supported by the National Natural Science Foundation of China (Nos.11735003,11975041,and 11961141004)。
文摘In recent years,graphics processing units(GPUs)have been applied to accelerate Monte Carlo(MC)simulations for proton dose calculation in radiotherapy.Nonetheless,current GPU platforms,such as Compute Unified Device Architecture(CUDA)and Open Computing Language(OpenCL),suffer from cross-platform limitation or relatively high programming barrier.However,the Taichi toolkit,which was developed to overcome these difficulties,has been successfully applied to high-performance numerical computations.Based on the class II condensed history simulation scheme with various proton-nucleus interactions,we developed a GPU-accelerated MC engine for proton transport using the Taichi toolkit.Dose distributions in homogeneous and heterogeneous geometries were calculated for 110,160,and 200 MeV protons and were compared with those obtained by full MC simulations using TOPAS.The gamma passing rates were greater than 0.99 and 0.95 with criteria of 2 mm,2%and 1 mm,1%,respectively,in all the benchmark tests.Moreover,the calculation speed was at least 5800 times faster than that of TOPAS,and the number of lines of code was approximately 10 times less than those of CUDA or OpenCL.Our study provides a highly accurate,efficient,and easy-to-use proton dose calculation engine for fast prototyping,beamlet calculation,and education purposes.
文摘The coupling between the Monte Carlo (MC) method and geometrical optics to improve accuracy is investigated. The results obtained show improved agreement with previous experimental data, demonstrating that the MC method, when coupled with simple geometrical optics, can simulate multiple scattering with enhanced fidelity.
基金Supported by the National Natural Science Foundation of China (60572015)
文摘In this paper, multipath temporal spreading distributions of laser pulses are calculated when they travel through the seawater. Individual photon is followed in Monte Carlo calculation A modified Henyey-Greenstein (HG) function is applied to represent the scattering phase function of seawater. This paper proposes a new scaling method, which uses the effective scattering thickness τd to replace the optical thickness used in the traditional scaling technique. This paper compares the temporal spreading distributions of photons on conditions of different attenuation coefficients and target depths. The experiments reveal that these mutual deviations are changing in the range from 0.5% to 5%, so long as the corresponding effective scattering thicknesses τd remains the same. Therefore, a conclusion can be obtained, that the temporal spreading distribution is only dependent on the effective diffusion thickness τd .
基金supported by the basic research program of Natural Science in Shannxi province of China (2021JQ-369)。
文摘In this paper, an importance sampling maximum likelihood(ISML) estimator for direction-of-arrival(DOA) of incoherently distributed(ID) sources is proposed. Starting from the maximum likelihood estimation description of the uniform linear array(ULA), a decoupled concentrated likelihood function(CLF) is presented. A new objective function based on CLF which can obtain a closed-form solution of global maximum is constructed according to Pincus theorem. To obtain the optimal value of the objective function which is a complex high-dimensional integral,we propose an importance sampling approach based on Monte Carlo random calculation. Next, an importance function is derived, which can simplify the problem of generating random vector from a high-dimensional probability density function(PDF) to generate random variable from a one-dimensional PDF. Compared with the existing maximum likelihood(ML) algorithms for DOA estimation of ID sources, the proposed algorithm does not require initial estimates, and its performance is closer to CramerRao lower bound(CRLB). The proposed algorithm performs better than the existing methods when the interval between sources to be estimated is small and in low signal to noise ratio(SNR)scenarios.
基金Supported by National Natural Science Foundation of China(91026009,11174358,11075203)
文摘The small angle neutron scattering (SANS) instrument is presently being constructed at Chinese Spal- lation Neutron Source (CSNS) in China, and the biological shielding design is needed to prevent the instrument from causing excessive dose rates in accessible locations. In this paper, the study of shielding design for SANS that relies on Monte Carlo simulation is introduced. Beam line shielding calculations are performed considering both scenarios of closed versus open TO chopper. The basic design scheme of the beam stop is discussed. The size of the TO chopper rotor is also estimated.
基金This work was supported by the National Natural Science Foundation of China under Grant 11790322.
文摘Purpose With the aim of determining mass yield distributions of primary fission products,a one-arm spectrometer was developed based on kinetic energy and time-of-flight correlation measurement technique.Methods An axial grid ionization chamber(GIC)was designed for energy detecting.In order to minimize energy losses and straggling,a thin silicon nitride film with a thickness of 100 nm was performed as the entrance window of the GIC.The energy resolution is 0.38%for 80 MeV ^(63)Cu particles.Two-timing detectors based on the detection of secondary emission electrons by microchannel plates(MCPs)constitute the time pick-off system,and the time-of-flight resolution is better than 200 ps(FWHM)measured with a ^(241)Amαsource.With a flight path length of 47.6 cm,the path length resolution is 0.21%.Results and conclusion The first result of mass distribution from ^(252)Cf spontaneous fission was reported.Energy losses of fragments in dead layers of the spectrometer were corrected event-by-event depend on the Monte Carlo calculation.The mass resolution for light fission fragments peak A107 amu is 1.3 aum.