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RSS2013 Vol. 25, No. 01
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2013,
25: 1-2.
doi: 10.3788/HPLPB20132501.0001
Abstract:
A self-made 15 ns, 10 mJ pulsed optical parametric oscillator was used as the pump source, peaking at 756.3 nm, with a bandwidth more than 0.5 nm. The 75 mm long gain medium was filled with metallic Rb and 67 kPa Ar at room temperature. When the temperature of gain medium reaches 136 ℃, we obtain Rb laser at 780 nm, and the output energy increases with temperature.
A self-made 15 ns, 10 mJ pulsed optical parametric oscillator was used as the pump source, peaking at 756.3 nm, with a bandwidth more than 0.5 nm. The 75 mm long gain medium was filled with metallic Rb and 67 kPa Ar at room temperature. When the temperature of gain medium reaches 136 ℃, we obtain Rb laser at 780 nm, and the output energy increases with temperature.
2013,
25: 3-4.
doi: 10.3788/HPLPB20132501.0003
Abstract:
The paper presents experimental results of the propagation performance of incoherent combined beams of six 100-watt single-mode fiber lasers. The waist size of each laser beam increases from 9 mm to 90 mm when it propagates through the beam expander. The six optical axes of fiber lasers in an array are controlled using individually controlled tip-tilt mirrors. The laser array is propagated to the target at a range of 470 m by a 440-mm beam director in strong and weak atmospheric turbulence. With the decrease in the intensity of turbulence, the ratio of the power in bucket to the total power on the target increases. And the increase ratio due to tip-tilt correction is about 1.7.
The paper presents experimental results of the propagation performance of incoherent combined beams of six 100-watt single-mode fiber lasers. The waist size of each laser beam increases from 9 mm to 90 mm when it propagates through the beam expander. The six optical axes of fiber lasers in an array are controlled using individually controlled tip-tilt mirrors. The laser array is propagated to the target at a range of 470 m by a 440-mm beam director in strong and weak atmospheric turbulence. With the decrease in the intensity of turbulence, the ratio of the power in bucket to the total power on the target increases. And the increase ratio due to tip-tilt correction is about 1.7.
2013,
25: 5-6.
doi: 10.3788/HPLPB20132501.0005
Abstract:
An experiment of coherent beam combination of a polarization maintaining(PM) ytterbium doped fiber amplifier (YDFA) and a non-PM YDFA is carried out. The adaptive polarization control based on the stochastic parallel gradient descent (SPGD) algorithm is obtained in the non-PM YDFA to make the output light polarization stable. The single frequency dithering algorithm is taken to compensate the phase errors in the system. The contrast of the far-field pattern increases remarkably from 80.1% to 87.2%. A scalable architecture for coherent beam combining of two styles of fiber amplifiers is also proposed.
An experiment of coherent beam combination of a polarization maintaining(PM) ytterbium doped fiber amplifier (YDFA) and a non-PM YDFA is carried out. The adaptive polarization control based on the stochastic parallel gradient descent (SPGD) algorithm is obtained in the non-PM YDFA to make the output light polarization stable. The single frequency dithering algorithm is taken to compensate the phase errors in the system. The contrast of the far-field pattern increases remarkably from 80.1% to 87.2%. A scalable architecture for coherent beam combining of two styles of fiber amplifiers is also proposed.
2013,
25: 7-11.
doi: 10.3788/HPLPB20132501.0007
Abstract:
A novel composite grating based on flat mage modulation is proposed to enlarge the measuring range of the Fourier transform profilometry (FTP). A sinusoidal image and a flat image without stripes are modulated into the grating to restrain the zero component in the Fourier spectrum. Compared with the composite grating based on the phase-shifting technique, the spectrum of the proposed grating becomes simpler because only DC component is introduced by the flat image. So the modulated information is easier to be filtered and the measuring accuracy is improved. The intensity calibration of the flat image demodulated from the composite grating is simpler than the sinusoidal image because only mean value calibration is involved. Moreover, the intensity of the demodulated flat image is proportional to the reflectance of the measuring object, which has some application in the practice. The Matlab is used to simulate the proposed method, and the experiment is performed to verify the feasibility of the proposed grating. Both of them demonstrate the flat image can be used to restrain the zero component and enlarge the measuring range of the FTP, and the measurement accuracy is improved.
A novel composite grating based on flat mage modulation is proposed to enlarge the measuring range of the Fourier transform profilometry (FTP). A sinusoidal image and a flat image without stripes are modulated into the grating to restrain the zero component in the Fourier spectrum. Compared with the composite grating based on the phase-shifting technique, the spectrum of the proposed grating becomes simpler because only DC component is introduced by the flat image. So the modulated information is easier to be filtered and the measuring accuracy is improved. The intensity calibration of the flat image demodulated from the composite grating is simpler than the sinusoidal image because only mean value calibration is involved. Moreover, the intensity of the demodulated flat image is proportional to the reflectance of the measuring object, which has some application in the practice. The Matlab is used to simulate the proposed method, and the experiment is performed to verify the feasibility of the proposed grating. Both of them demonstrate the flat image can be used to restrain the zero component and enlarge the measuring range of the FTP, and the measurement accuracy is improved.
2013,
25: 12-16.
doi: 10.3788/HPLPB20132501.0012
Abstract:
A theoretical model is established to investigate the influences of the group delay ripples (GDRs) of the fiber Bragg grating (FBG) on the characteristics of microwave-photonic filters using a coherent light source or an incoherent light source. Based on this theoretical model, the amplitude-frequency response and phase-frequency response of the microwave-photonic filter are investigated, while random and measured GDR distributions are employed. Results are then achieved for both coherent light source based and incoherent light source based microwave filters. For the coherent light source based filters, the GDRs result in a frequency shift to the notches of amplitude-frequency response. While for the incoherent light source based filters, the distortions to the profile of amplitude-frequency response and to the linear phase are observed due to the existence of GDRs. In addition, for the multi-tap microwave filters, the side-band suppression ratio and the extinction ratio are degraded under the influence of GDRs.
A theoretical model is established to investigate the influences of the group delay ripples (GDRs) of the fiber Bragg grating (FBG) on the characteristics of microwave-photonic filters using a coherent light source or an incoherent light source. Based on this theoretical model, the amplitude-frequency response and phase-frequency response of the microwave-photonic filter are investigated, while random and measured GDR distributions are employed. Results are then achieved for both coherent light source based and incoherent light source based microwave filters. For the coherent light source based filters, the GDRs result in a frequency shift to the notches of amplitude-frequency response. While for the incoherent light source based filters, the distortions to the profile of amplitude-frequency response and to the linear phase are observed due to the existence of GDRs. In addition, for the multi-tap microwave filters, the side-band suppression ratio and the extinction ratio are degraded under the influence of GDRs.
2013,
25: 17-21.
doi: 10.3788/HPLPB20132501.0017
Abstract:
To study the effect of the wheel-arc error on large-scale rectangular axisymmetric aspheric machining, the grating parallel grinding method is adopted and the mathematical model of wheel-arc error separation is built. The factors that affect the surface accuracy are analyzed and it is found that the wheel-arc error is the most sensitive in the factors. According to the grinding and measurement method, the wheel-arc error is separated. Using the new wheel-arc radius modified by separated wheel-arc error and the new compensation data subtracted from wheel-arc error, the separating error compensation grinding is carried out and proves effective. The experimental results show that the aspheric surface error decreases by 14% and 35% after separating error compensation grinding in rough and fine grinding conditions. The error model can separate the wheel-arc error effectively and the accuracy of the aspheric surface is improved.
To study the effect of the wheel-arc error on large-scale rectangular axisymmetric aspheric machining, the grating parallel grinding method is adopted and the mathematical model of wheel-arc error separation is built. The factors that affect the surface accuracy are analyzed and it is found that the wheel-arc error is the most sensitive in the factors. According to the grinding and measurement method, the wheel-arc error is separated. Using the new wheel-arc radius modified by separated wheel-arc error and the new compensation data subtracted from wheel-arc error, the separating error compensation grinding is carried out and proves effective. The experimental results show that the aspheric surface error decreases by 14% and 35% after separating error compensation grinding in rough and fine grinding conditions. The error model can separate the wheel-arc error effectively and the accuracy of the aspheric surface is improved.
2013,
25: 22-26.
doi: 10.3788/HPLPB20132501.0022
Abstract:
Most existing study on non-line-of-sight solar-blind ultraviolet communication single scatter models use the prolate-spheroidal coordinates to obtain solutions. In the solving process, the effective scattering volume must undergo the difficult numerical integration and the three groups of integral limits which determine the volume can be calculated. The widely adopted yet complex single-scatter channel model is significantly simplified by means of a closed-form expression for tractable analysis in this paper. And the path loss is given as a function of transceiver geometries as well as scattering and absorption coefficient. The simulation results of transmission distance and path loss show that the approximated path loss matches that from direct numerical integration very well. Using the closed-form expression of path loss, the influence of atmospheric visibility on the path loss and bit-error-rate of the ultraviolet communication system is simulated. The simulation results show that: the better weather and the higher visibility do not result in greater system performances, but when the visibility equals 9-10 km, the best performance can be obtained.
Most existing study on non-line-of-sight solar-blind ultraviolet communication single scatter models use the prolate-spheroidal coordinates to obtain solutions. In the solving process, the effective scattering volume must undergo the difficult numerical integration and the three groups of integral limits which determine the volume can be calculated. The widely adopted yet complex single-scatter channel model is significantly simplified by means of a closed-form expression for tractable analysis in this paper. And the path loss is given as a function of transceiver geometries as well as scattering and absorption coefficient. The simulation results of transmission distance and path loss show that the approximated path loss matches that from direct numerical integration very well. Using the closed-form expression of path loss, the influence of atmospheric visibility on the path loss and bit-error-rate of the ultraviolet communication system is simulated. The simulation results show that: the better weather and the higher visibility do not result in greater system performances, but when the visibility equals 9-10 km, the best performance can be obtained.
2013,
25: 27-30.
doi: 10.3788/HPLPB20132501.0027
Abstract:
An optical parameter oscillator (OPO) based on a Nd:YAG laser and two pieces of KTiOPO4 (KTP) nonlinear crystal that could be tuned from 750-800 nm was built for alkali vapor lasers high-intensity pumping experiment. It can provide 113 mJ each pulse at the central wavelength of 780.2 nm with a duration of 15.43 ns. This means the peak power could be as high as 7 MW. The spectral line width is about 0.38 nm and the beam diameter is 5.5 mm. Clear fluorescence can be observed when the signal light passes through the 10 cm long Rb cell with Ar buffer gas at a temperature of 120 ℃, which demonstrates the validity of this OPO system to be used in alkali laser studies.
An optical parameter oscillator (OPO) based on a Nd:YAG laser and two pieces of KTiOPO4 (KTP) nonlinear crystal that could be tuned from 750-800 nm was built for alkali vapor lasers high-intensity pumping experiment. It can provide 113 mJ each pulse at the central wavelength of 780.2 nm with a duration of 15.43 ns. This means the peak power could be as high as 7 MW. The spectral line width is about 0.38 nm and the beam diameter is 5.5 mm. Clear fluorescence can be observed when the signal light passes through the 10 cm long Rb cell with Ar buffer gas at a temperature of 120 ℃, which demonstrates the validity of this OPO system to be used in alkali laser studies.
2013,
25: 31-36.
doi: 10.3788/HPLPB20132501.0031
Abstract:
Based on the extended Huygens-Fresnel principle and matrix methods in optics, the scintillation properties of the polarized and partially coherent laser beam at the receiver are studied, and the effect of the atmospheric turbulence both on the laser beam as it propagates to the target and on the scattered field as it propagates back to the receiver is considered. The combination of the Jones matrix of the wave plate and the ABCD ray-transfer matrix is considered. The fourth moment of the wave field is focused on and the expression of the scintillation index is derived. The influences of the refractive-index structure constant, the wavelength, the spot radius and the spatial correlation length of the beam on the scintillation index are discussed. The numerical results show that the scintillation index of the polarized and partially coherent laser beam increases to peak at first and then decreases gradually with the increase of distance between the target and transmitter. The beam whose coherence property is poor induces a small scintillation index, and a large change on the scintillation index follows a little change on the spatial correlation length, while the beam with good coherence property induces a big scintillation index, and the scintillation index does not change with change on the spatial correlation length.
Based on the extended Huygens-Fresnel principle and matrix methods in optics, the scintillation properties of the polarized and partially coherent laser beam at the receiver are studied, and the effect of the atmospheric turbulence both on the laser beam as it propagates to the target and on the scattered field as it propagates back to the receiver is considered. The combination of the Jones matrix of the wave plate and the ABCD ray-transfer matrix is considered. The fourth moment of the wave field is focused on and the expression of the scintillation index is derived. The influences of the refractive-index structure constant, the wavelength, the spot radius and the spatial correlation length of the beam on the scintillation index are discussed. The numerical results show that the scintillation index of the polarized and partially coherent laser beam increases to peak at first and then decreases gradually with the increase of distance between the target and transmitter. The beam whose coherence property is poor induces a small scintillation index, and a large change on the scintillation index follows a little change on the spatial correlation length, while the beam with good coherence property induces a big scintillation index, and the scintillation index does not change with change on the spatial correlation length.
2013,
25: 37-41.
doi: 10.3788/HPLPB20132501.0037
Abstract:
A background suppression algorithm based on the wave atom transform (WAT) is proposed to remove the complex background clutter in the detection technique of dim and small targets in infrared images. WAT is used to decompose the input image, and to extract multi-scale and multi-direction detail features of the original image. According to the difference between the target and background clutter signal, each coefficient of the WAT decomposed level is modified by the frequency domain adjustment function, then the predicted background image is reconstructed using wave atom inverse transform. Finally, the result image is obtained by subtracting the background image from the original image. Experimental results demonstrate that the proposed algorithm can highlight targets, improve signal-to-clutter ratio, and suppress complicated background clutter in infrared images with dim and small targets effectively when compared with the max-median and wavelet algorithms.
A background suppression algorithm based on the wave atom transform (WAT) is proposed to remove the complex background clutter in the detection technique of dim and small targets in infrared images. WAT is used to decompose the input image, and to extract multi-scale and multi-direction detail features of the original image. According to the difference between the target and background clutter signal, each coefficient of the WAT decomposed level is modified by the frequency domain adjustment function, then the predicted background image is reconstructed using wave atom inverse transform. Finally, the result image is obtained by subtracting the background image from the original image. Experimental results demonstrate that the proposed algorithm can highlight targets, improve signal-to-clutter ratio, and suppress complicated background clutter in infrared images with dim and small targets effectively when compared with the max-median and wavelet algorithms.
2013,
25: 42-46.
doi: 10.3788/HPLPB20132501.0042
Abstract:
The optical field of a Lorentz-Gaussian beam propagating in a gradient-index medium is derived. Based on the second-order moment of the intensity distribution, the analytical expressions of the half beam width and its changing rate are also presented. The influence of the gradient-index coefficient on the propagation properties of the Lorentz-Gaussian beam is mainly analyzed. The numerical results show that the variation of the normalized intensity distribution, the half beam width and its changing rate are periodic, and the period is times the gradient-index coefficient. The maximum on-axis intensity appears at the half period. The gradient-index coefficient nearly doesnt affect the normalized intensity distribution and the half beam width, but it influences the changing rate of the half beam width.
The optical field of a Lorentz-Gaussian beam propagating in a gradient-index medium is derived. Based on the second-order moment of the intensity distribution, the analytical expressions of the half beam width and its changing rate are also presented. The influence of the gradient-index coefficient on the propagation properties of the Lorentz-Gaussian beam is mainly analyzed. The numerical results show that the variation of the normalized intensity distribution, the half beam width and its changing rate are periodic, and the period is times the gradient-index coefficient. The maximum on-axis intensity appears at the half period. The gradient-index coefficient nearly doesnt affect the normalized intensity distribution and the half beam width, but it influences the changing rate of the half beam width.
2013,
25: 47-51.
doi: 10.3788/HPLPB20132501.0047
Abstract:
A method using scanning filter to improve the contrast of chirped pulse is proposed, and the principle of this method is analyzed. The scanning filter is compared with the existing pulse-picking technique and nonlinear filtering technique. The scanning filter is a temporal gate that is independent on the intensity of the pulses, but on the instantaneous wavelengths of light. Taking the electro-optic birefringence scanning filter as an example, the application of scanning filter methods is illustrated. Based on numerical simulation and experimental research, it is found that the electro-optic birefringence scanning filter can eliminate a prepulse which is several hundred picoseconds before the main pulse, and the main pulse can maintain a high transmissivity.
A method using scanning filter to improve the contrast of chirped pulse is proposed, and the principle of this method is analyzed. The scanning filter is compared with the existing pulse-picking technique and nonlinear filtering technique. The scanning filter is a temporal gate that is independent on the intensity of the pulses, but on the instantaneous wavelengths of light. Taking the electro-optic birefringence scanning filter as an example, the application of scanning filter methods is illustrated. Based on numerical simulation and experimental research, it is found that the electro-optic birefringence scanning filter can eliminate a prepulse which is several hundred picoseconds before the main pulse, and the main pulse can maintain a high transmissivity.
2013,
25: 52-56.
doi: 10.3788/HPLPB20132501.0052
Abstract:
The flow fields of two typical DC plasma arcs, namely the transferred free burning arc and the non-transferred arc were simulated by solving hydrodynamic equations and electromagnetic equations. The effects of the Lorentz force on the characteristics of the flow fields of these two typical DC plasma arcs were estimated. Results show that in the case of the free burning arc, the Lorentz force due to the current self-induced magnetic field has significant impact on the flow fields, as the self-induced magnetic compression is the main arc constraint mechanism. However, in the case of the non-transferred arc generated in a torch with long and narrow inter-electrode inserts and an abruptly expanded anode, the Lorentz force has limited impact on the flow fields of the plasma especially at the downstream of the inter-electrode inserts, compared with the strong wall constraints and relatively high aerodynamic force. This is because the ratio of the electromagnetic force to the aerodynamic force is only about 0.01 in this region. When the main consideration is outlet parameters of the wall stabilized non-transferred DC arc plasma generator, in order to improve the efficiency of the numerical simulation program, the Lorentz force could be neglected in the non-transferred arc in some cases.
The flow fields of two typical DC plasma arcs, namely the transferred free burning arc and the non-transferred arc were simulated by solving hydrodynamic equations and electromagnetic equations. The effects of the Lorentz force on the characteristics of the flow fields of these two typical DC plasma arcs were estimated. Results show that in the case of the free burning arc, the Lorentz force due to the current self-induced magnetic field has significant impact on the flow fields, as the self-induced magnetic compression is the main arc constraint mechanism. However, in the case of the non-transferred arc generated in a torch with long and narrow inter-electrode inserts and an abruptly expanded anode, the Lorentz force has limited impact on the flow fields of the plasma especially at the downstream of the inter-electrode inserts, compared with the strong wall constraints and relatively high aerodynamic force. This is because the ratio of the electromagnetic force to the aerodynamic force is only about 0.01 in this region. When the main consideration is outlet parameters of the wall stabilized non-transferred DC arc plasma generator, in order to improve the efficiency of the numerical simulation program, the Lorentz force could be neglected in the non-transferred arc in some cases.
2013,
25: 57-61.
doi: 10.3788/HPLPB20132501.0057
Abstract:
Radiation pulse shaping for indirect-drive laser fusion ignition targets was studied in detail with numerical simulation. A four-step pulse was shaped first, according to the description of Lindl about low-entropy compression of DT fuel, requiring that the DT ice is compressed by four shocks that coalesce near the inside surface of the fuel. But the fuel entropy is quite high driven with this pulse. The causation is that an additional strong shock is produced during the acceleration phase. Then a new pulse was shaped to compress the fuel well. It includes three steps and rises to top temperature by two slopes. This pulse changed the time and the pressure of the fourth shock, which could effectively avoid the production of the additional strong shock. The entropy increase which happens because of terminating the pulse too early in order not to ablate the ablator too much is also described in this work. The new pulse presented here resolves this problem well by controlling the time when the pulse reaches the top temperature.
Radiation pulse shaping for indirect-drive laser fusion ignition targets was studied in detail with numerical simulation. A four-step pulse was shaped first, according to the description of Lindl about low-entropy compression of DT fuel, requiring that the DT ice is compressed by four shocks that coalesce near the inside surface of the fuel. But the fuel entropy is quite high driven with this pulse. The causation is that an additional strong shock is produced during the acceleration phase. Then a new pulse was shaped to compress the fuel well. It includes three steps and rises to top temperature by two slopes. This pulse changed the time and the pressure of the fourth shock, which could effectively avoid the production of the additional strong shock. The entropy increase which happens because of terminating the pulse too early in order not to ablate the ablator too much is also described in this work. The new pulse presented here resolves this problem well by controlling the time when the pulse reaches the top temperature.
2013,
25: 62-66.
doi: 10.3788/HPLPB20132501.0062
Abstract:
Aiming at the difficulties and high-precision detection demand for assembly error inspection of micro-capsule in inertial confinement fusion(ICF) device, the measurement system for assembly parameters detection of laser target is developed. A compound measuring method based on laser probe and CCD is proposed. The mathematical model for data fusion of the compound probe is established by calibrating their spatial location relationship. Thus, high-precision 3D inspection is realized. The inspection method of micro-capsule assembly error is discussed in two cases. The experimental results demonstrate the validity of these two approaches. Furthermore, the measurement precision of such two approaches is compared and their limit errors are both within 3 m.
Aiming at the difficulties and high-precision detection demand for assembly error inspection of micro-capsule in inertial confinement fusion(ICF) device, the measurement system for assembly parameters detection of laser target is developed. A compound measuring method based on laser probe and CCD is proposed. The mathematical model for data fusion of the compound probe is established by calibrating their spatial location relationship. Thus, high-precision 3D inspection is realized. The inspection method of micro-capsule assembly error is discussed in two cases. The experimental results demonstrate the validity of these two approaches. Furthermore, the measurement precision of such two approaches is compared and their limit errors are both within 3 m.
2013,
25: 67-70.
doi: 10.3788/HPLPB20132501.0067
Abstract:
The interaction physics between energetic particle and plasma are introduced. The energy loss and energy needed by single particle and pass through time on energetic C, Si, Ar, Au and U in equimolar DT plasma at 1000 g/cm3 in density and 50 m in diameter and room temperature were calculated by Monte Carlo method. The feasibility of ICF ignition by swift heavy ions irradiation were proved. In theory, heavier ion mass ensures better ICF ignition. The heavy ions beam intensity and single ion energy needed by ignition are about MA and over GeV, respectively. The duration is several picoseconds.
The interaction physics between energetic particle and plasma are introduced. The energy loss and energy needed by single particle and pass through time on energetic C, Si, Ar, Au and U in equimolar DT plasma at 1000 g/cm3 in density and 50 m in diameter and room temperature were calculated by Monte Carlo method. The feasibility of ICF ignition by swift heavy ions irradiation were proved. In theory, heavier ion mass ensures better ICF ignition. The heavy ions beam intensity and single ion energy needed by ignition are about MA and over GeV, respectively. The duration is several picoseconds.
2013,
25: 71-76.
doi: 10.3788/HPLPB20132501.0071
Abstract:
A T-shaped microchannel is efficient for monodispersed droplet formation. In order to get a better understanding, the droplet formation process was investigated by numerical simulation and experiment. Silicon oil and precursory sol for hollow glass microspheres were used as the continuous phase and the dispersed phase respectively. A numerical model of the droplet formation was established on the basis of force analysis for a single droplet. Effects of the flow rates on the droplet size were investigated. The results show that the droplet diameters can be controlled by adjusting the flow rates of both phases. Droplet diameters decrease with the increase of continuous phase flow rate at a given dispersed phase flow rate. There is a range beyond which the effect of the continuous phase flow rate becomes weak. The droplet diameters increase with the increase of dispersed phase flow rate. Droplet diameters calculated by the numerical model are close to those by experiment with a deviation around 10%. Based on the simulation and the video, the droplet experiences two phases, namely, the droplet growing under a quasi-steady situation and the stripping. The results help with a better understanding about the droplet formation in a T-shaped microchannel. They also provide good reference for size control of gel microspheres fabricated by sol-microemulsion-gel process.
A T-shaped microchannel is efficient for monodispersed droplet formation. In order to get a better understanding, the droplet formation process was investigated by numerical simulation and experiment. Silicon oil and precursory sol for hollow glass microspheres were used as the continuous phase and the dispersed phase respectively. A numerical model of the droplet formation was established on the basis of force analysis for a single droplet. Effects of the flow rates on the droplet size were investigated. The results show that the droplet diameters can be controlled by adjusting the flow rates of both phases. Droplet diameters decrease with the increase of continuous phase flow rate at a given dispersed phase flow rate. There is a range beyond which the effect of the continuous phase flow rate becomes weak. The droplet diameters increase with the increase of dispersed phase flow rate. Droplet diameters calculated by the numerical model are close to those by experiment with a deviation around 10%. Based on the simulation and the video, the droplet experiences two phases, namely, the droplet growing under a quasi-steady situation and the stripping. The results help with a better understanding about the droplet formation in a T-shaped microchannel. They also provide good reference for size control of gel microspheres fabricated by sol-microemulsion-gel process.
2013,
25: 77-81.
doi: 10.3788/HPLPB20132501.0077
Abstract:
A 1-D photonic crystal (PC) mirror of the optical resonator for THz free electron lasers (FELs) is designed theoretically with central frequencies from 1 to 3 THz. The relationship between the reflection spectrum and structural parameters of 1-D PC, such as dielectric thickness, number of layers, and refraction index, is studied. A systematical method to design PC mirrors with high reflectivity is proposed. The out-couplers in the presence of defect layers in PC structure is simulated. It is shown that the out-coupling ratio of the resonator is dynamically tunable by careful adjustment and design of the defect layers. A practical tuning method for THz FELs using PC mirrors is proposed. Moreover, the shift of the whole reflection spectrum is also viable by adjusting the dielectric layer thickness, which extends the tuning range of high reflection PC mirrors and out-couplers.
A 1-D photonic crystal (PC) mirror of the optical resonator for THz free electron lasers (FELs) is designed theoretically with central frequencies from 1 to 3 THz. The relationship between the reflection spectrum and structural parameters of 1-D PC, such as dielectric thickness, number of layers, and refraction index, is studied. A systematical method to design PC mirrors with high reflectivity is proposed. The out-couplers in the presence of defect layers in PC structure is simulated. It is shown that the out-coupling ratio of the resonator is dynamically tunable by careful adjustment and design of the defect layers. A practical tuning method for THz FELs using PC mirrors is proposed. Moreover, the shift of the whole reflection spectrum is also viable by adjusting the dielectric layer thickness, which extends the tuning range of high reflection PC mirrors and out-couplers.
2013,
25: 82-86.
doi: 10.3788/HPLPB20132501.0082
Abstract:
The mode competition of an open resonant cavity with iris structure is analyzed by using the cold cavity method. The design of a cavity for a W-band third-harmonic gyrotron operating at the TE61 mode is presented. PIC simulation results show that a single-mode third-harmonic radiation with a power of 20 kW can be expected at a beam voltage of 45 kV and current of 3 A, and the corresponding electron efficiency is 14.8%.
The mode competition of an open resonant cavity with iris structure is analyzed by using the cold cavity method. The design of a cavity for a W-band third-harmonic gyrotron operating at the TE61 mode is presented. PIC simulation results show that a single-mode third-harmonic radiation with a power of 20 kW can be expected at a beam voltage of 45 kV and current of 3 A, and the corresponding electron efficiency is 14.8%.
2013,
25: 87-92.
doi: 10.3788/HPLPB20132501.0087
Abstract:
An S-band tunable relativistic magnetron with axial diffraction output, which contains the structure of 10-cavity rising-sun magnetron and the modified structure of axial diffraction output, is investigated. The softwares of high-frequency field analysis and particle simulation are used to analyze and optimize the operating performance of the device. Simulation results show that more than 530 MW output power and more than 20% power conversion efficiency can be obtained within 20% relative bandwidth (about 700 MHz). The maximum power conversion efficiency can reach 40.19%, with a operating voltage of 350 kV and a magnetic field of 0.3 T.
An S-band tunable relativistic magnetron with axial diffraction output, which contains the structure of 10-cavity rising-sun magnetron and the modified structure of axial diffraction output, is investigated. The softwares of high-frequency field analysis and particle simulation are used to analyze and optimize the operating performance of the device. Simulation results show that more than 530 MW output power and more than 20% power conversion efficiency can be obtained within 20% relative bandwidth (about 700 MHz). The maximum power conversion efficiency can reach 40.19%, with a operating voltage of 350 kV and a magnetic field of 0.3 T.
2013,
25: 93-98.
doi: 10.3788/HPLPB20132501.0093
Abstract:
The theoretical analysis to the RF cavity at China Spallation Neutron Source (CSNS), a typical ferrite-loaded coaxial resonant cavity operating in swept condition by using the coaxial transmission line theory is presented. The modeling method of the cavity in the CST three-dimensional simulation software is also described in details, especially about the use of ceramic insulators representing resonant capacitors. The characteristics of the cavity obtained by the coaxial transmission line method, the CST simulations and the measurements have been compared, and are consistent. The parasitic mode induced by the Busbar has been studied by the CST simulations and the measurements, and different improvement methods over the prototype cavity are given. The impact of the filling factor of ferrite rings on the frequency tuning in the cavity has also been analyzed, and it turns out that a larger tuning range for the bias current is needed for a shorter cavity.
The theoretical analysis to the RF cavity at China Spallation Neutron Source (CSNS), a typical ferrite-loaded coaxial resonant cavity operating in swept condition by using the coaxial transmission line theory is presented. The modeling method of the cavity in the CST three-dimensional simulation software is also described in details, especially about the use of ceramic insulators representing resonant capacitors. The characteristics of the cavity obtained by the coaxial transmission line method, the CST simulations and the measurements have been compared, and are consistent. The parasitic mode induced by the Busbar has been studied by the CST simulations and the measurements, and different improvement methods over the prototype cavity are given. The impact of the filling factor of ferrite rings on the frequency tuning in the cavity has also been analyzed, and it turns out that a larger tuning range for the bias current is needed for a shorter cavity.
2013,
25: 99-103.
doi: 10.3788/HPLPB20132501.0099
Abstract:
The target material can be heated to the warm dense matter (WDM) state by irradiation with a 20 MeV, 2.5 kA, 70 ns electron beam, and the measurements of equation of state, electrical conductivity and opacity can be carried out. The beam and target interaction for WDM research on DRAGON-Ⅰ linear induction accelerator and diagnostic technologies are introduced in this paper. Simulation results of the electron energy deposition and hydrodynamic response of 0.3-mm-diameter and 1-mm-length target wires made of different metals are presented. The results show that the temperature rise in the target wires increases and the uniformity of the temperature distribution decreases, as the atomic number increases. For metal with relatively high atomic number, such as tantalum, the temperature in the wire could rise to about 1.6 eV at 40 ns.
The target material can be heated to the warm dense matter (WDM) state by irradiation with a 20 MeV, 2.5 kA, 70 ns electron beam, and the measurements of equation of state, electrical conductivity and opacity can be carried out. The beam and target interaction for WDM research on DRAGON-Ⅰ linear induction accelerator and diagnostic technologies are introduced in this paper. Simulation results of the electron energy deposition and hydrodynamic response of 0.3-mm-diameter and 1-mm-length target wires made of different metals are presented. The results show that the temperature rise in the target wires increases and the uniformity of the temperature distribution decreases, as the atomic number increases. For metal with relatively high atomic number, such as tantalum, the temperature in the wire could rise to about 1.6 eV at 40 ns.
2013,
25: 104-108.
doi: 10.3788/HPLPB20132501.0104
Abstract:
This paper introduces the features of the compact cyclotron CYCIAE-100 and some key physical issues in the design, including the vertical focusing of straight sector magnet structure, design of the special-shape RF resonator, space charge effect, etc. For the main magnet of CYCIAE-100, the straight sector magnet is adopted in the design to reduce the difficulties of fabricating the magnet as well as the RF cavity. Meanwhile, given the fact that the vertical focusing decreases at large radii for the straight sector magnet, the variable hill gap technology is adopted to effectively improve the vertical focusing. Space charge effect study have been carried out with the independently developed code OPAL-CYCL based on the PIC technology, and the result shows that the current limit for CYCIAE-100 is 10 mA. In-depth study results on the beam test of the machine are also described in the paper, including the tuning scheme, diagnostics device layout, beam data measured from the radial probe, and physical figures.
This paper introduces the features of the compact cyclotron CYCIAE-100 and some key physical issues in the design, including the vertical focusing of straight sector magnet structure, design of the special-shape RF resonator, space charge effect, etc. For the main magnet of CYCIAE-100, the straight sector magnet is adopted in the design to reduce the difficulties of fabricating the magnet as well as the RF cavity. Meanwhile, given the fact that the vertical focusing decreases at large radii for the straight sector magnet, the variable hill gap technology is adopted to effectively improve the vertical focusing. Space charge effect study have been carried out with the independently developed code OPAL-CYCL based on the PIC technology, and the result shows that the current limit for CYCIAE-100 is 10 mA. In-depth study results on the beam test of the machine are also described in the paper, including the tuning scheme, diagnostics device layout, beam data measured from the radial probe, and physical figures.
2013,
25: 109-113.
doi: 10.3788/HPLPB20132501.0109
Abstract:
Based on turn-by-turn (TBT) signal processing, the paper emphasizes on the optimization of system timing and implementation of digital automatic gain control, slow application (SA) modules. Beam position including TBT, fast application (FA) and SA data can be acquired. On-line evaluation on Shanghai Synchrotron Radiation Facility (SSRF) shows that the processor is able to get the multi-rate position data which contain true beam movements. When the storage ring is 174 mA and 500 bunches filled, the resolutions of TBT data, FA data and SA data achieve 0.84, 0.44 and 0.23 m respectively. The above results prove that the design could meet the performance requirements.
Based on turn-by-turn (TBT) signal processing, the paper emphasizes on the optimization of system timing and implementation of digital automatic gain control, slow application (SA) modules. Beam position including TBT, fast application (FA) and SA data can be acquired. On-line evaluation on Shanghai Synchrotron Radiation Facility (SSRF) shows that the processor is able to get the multi-rate position data which contain true beam movements. When the storage ring is 174 mA and 500 bunches filled, the resolutions of TBT data, FA data and SA data achieve 0.84, 0.44 and 0.23 m respectively. The above results prove that the design could meet the performance requirements.
2013,
25: 114-118.
doi: 10.3788/HPLPB20132501.0114
Abstract:
In order to solve the traditional detectors shortcomings of low speed and weak precision, to detect small sophisticated devices, and meet the demand of reconstructed images with high spatial resolution in low-energy X-ray microfocus CT systems, a small interval signal acquisition system is proposed. The system takes X-CARD 0.2-256G as the detector, which is highly integrated with fast scanning speed and only 0.2 mm pixel size, Cyclone EP1C3T as the core logic control module, and LXT972A as the Ethernet chip. The whole hardware and logic designations are described clearly in terms of the performance of reliable, stable and high efficiency. Then the dynamic range of the system is tested. Experimental results show that the proposed system has a dynamic range larger than 4000, can collect and transport the signal quickly and accurately, and can satisfy the requirements of ICT transmission sufficiently.
In order to solve the traditional detectors shortcomings of low speed and weak precision, to detect small sophisticated devices, and meet the demand of reconstructed images with high spatial resolution in low-energy X-ray microfocus CT systems, a small interval signal acquisition system is proposed. The system takes X-CARD 0.2-256G as the detector, which is highly integrated with fast scanning speed and only 0.2 mm pixel size, Cyclone EP1C3T as the core logic control module, and LXT972A as the Ethernet chip. The whole hardware and logic designations are described clearly in terms of the performance of reliable, stable and high efficiency. Then the dynamic range of the system is tested. Experimental results show that the proposed system has a dynamic range larger than 4000, can collect and transport the signal quickly and accurately, and can satisfy the requirements of ICT transmission sufficiently.
2013,
25: 119-122.
doi: 10.3788/HPLPB20132501.0119
Abstract:
The laser system based on Q-switched technique of acousto-optical modulation is all-fiber using passive fibers as media to generate supercontinuum, which can output different-width supercontinuum only by adjusting the pump power and repetition rate. With higher pump power, lower repetition rate, longer passive fiber, a wider supercontinuum is obtained. The supercontinuum range can be extended by splicing a passive fiber, and the supercontinuum width exceeds 700 nm when the passive fiber is 200 m long at 1 kHz modulation frequency, 1.0% duty and 4.68 W pump power. The all-fiber nanosecond pulsed laser has simple configuration with fully fiberized cavities without the need for free-space components, allowing for robust and compact system designs. Its parameters can be easily adjusted by the acousto-optical modulator, which greatly extends the applications in industrial deployment.
The laser system based on Q-switched technique of acousto-optical modulation is all-fiber using passive fibers as media to generate supercontinuum, which can output different-width supercontinuum only by adjusting the pump power and repetition rate. With higher pump power, lower repetition rate, longer passive fiber, a wider supercontinuum is obtained. The supercontinuum range can be extended by splicing a passive fiber, and the supercontinuum width exceeds 700 nm when the passive fiber is 200 m long at 1 kHz modulation frequency, 1.0% duty and 4.68 W pump power. The all-fiber nanosecond pulsed laser has simple configuration with fully fiberized cavities without the need for free-space components, allowing for robust and compact system designs. Its parameters can be easily adjusted by the acousto-optical modulator, which greatly extends the applications in industrial deployment.
2013,
25: 123-126.
doi: 10.3788/HPLPB20132501.0123
Abstract:
The 1∶4 transmission line transformers (TLTs) made of the good flexible coaxial cable and the high-permeability iron-based amorphous magnetic material were put forward, and applied to the output transform devices. Related high voltage pulse experimental research was carried out. The optimum impedance matching and the wave aberration because of the impedance mismatching in actual project were deduced and obtained based on the transmission line theory and the principle of the reflection and refraction of traveling waves. Also, the response of the magnetic core material to the pulse was analyzed. The results show that the TLTs have good response to the output pulse, including the improvement of rising time, and the decrease of energy consumption, and that the test result is consistent with the theoretical calculation result.
The 1∶4 transmission line transformers (TLTs) made of the good flexible coaxial cable and the high-permeability iron-based amorphous magnetic material were put forward, and applied to the output transform devices. Related high voltage pulse experimental research was carried out. The optimum impedance matching and the wave aberration because of the impedance mismatching in actual project were deduced and obtained based on the transmission line theory and the principle of the reflection and refraction of traveling waves. Also, the response of the magnetic core material to the pulse was analyzed. The results show that the TLTs have good response to the output pulse, including the improvement of rising time, and the decrease of energy consumption, and that the test result is consistent with the theoretical calculation result.
2013,
25: 127-132.
doi: 10.3788/HPLPB20132501.0127
Abstract:
The analytic expression of the purely resistive load output voltage is derived by using the Laplace transform to solve the process that a two-stage coaxial Blumlein line discharges a resistive load. The influence of switch inductance, resistive load inductance and loop inductance on the resistive load main pulse is analyzed. Comparing the result simulated by PSpice with the suppositional expression of load voltage, we find they fit well. The result indicates that the pulse rising time is mainly determined by switch inductance and the trend of the flat part is mainly determined by loop inductance .The smaller the switch inductance is, the less the rising time is; the larger the loop inductance is, the higher the pulse voltage and the energy efficiency are. The conclusion is significant to the design of two-stage coaxial Blumlein lines.
The analytic expression of the purely resistive load output voltage is derived by using the Laplace transform to solve the process that a two-stage coaxial Blumlein line discharges a resistive load. The influence of switch inductance, resistive load inductance and loop inductance on the resistive load main pulse is analyzed. Comparing the result simulated by PSpice with the suppositional expression of load voltage, we find they fit well. The result indicates that the pulse rising time is mainly determined by switch inductance and the trend of the flat part is mainly determined by loop inductance .The smaller the switch inductance is, the less the rising time is; the larger the loop inductance is, the higher the pulse voltage and the energy efficiency are. The conclusion is significant to the design of two-stage coaxial Blumlein lines.
2013,
25: 133-137.
doi: 10.3788/HPLPB20132501.0133
Abstract:
A bounded-wave simulator with ellipse-arc transitional section structure is proposed and designed. The electric field waveform in the simulator is simulated and compared with the tapered transitional section simulator by using the electromagnetic-field simulating software CST. The double exponential pulse with rise time 2 ns, full-width at half-maximum (FWHM) amplitude 25 ns and the step pulse with rise time 2 ns, duration about 80 ns are obtained in the experiment. And a comparison is carried out between the two simulators. The results of simulation and experiment both indicate that the bounded-wave simulator eliminates the interference effectively coming from the discontinuity at the junction of the transitional section and parallel-plate section.
A bounded-wave simulator with ellipse-arc transitional section structure is proposed and designed. The electric field waveform in the simulator is simulated and compared with the tapered transitional section simulator by using the electromagnetic-field simulating software CST. The double exponential pulse with rise time 2 ns, full-width at half-maximum (FWHM) amplitude 25 ns and the step pulse with rise time 2 ns, duration about 80 ns are obtained in the experiment. And a comparison is carried out between the two simulators. The results of simulation and experiment both indicate that the bounded-wave simulator eliminates the interference effectively coming from the discontinuity at the junction of the transitional section and parallel-plate section.
2013,
25: 138-142.
doi: 10.3788/HPLPB20132501.0138
Abstract:
A new method is proposed to simulate the scattered photons in high energy X-ray radiography fast and precisely. The problem of X-ray radiography is turned into an effective pure photon transport problem, and an iterative solution to the photon transport equation is designed. Then, the solution is turned into a discrete version and realized in a computer program. After, the Monte Carlo N-particle transport code MCNP is used to measure the effective photon scattering function and other parameters needed in the discrete method. Finally, the new computer program is compared with MCNP in a radiography example as a check of the method. It is consistent with MCNP for the radiography of thin objects, but shows large deviation for thick ones. The current computer program can be used in qualitative analysis.
A new method is proposed to simulate the scattered photons in high energy X-ray radiography fast and precisely. The problem of X-ray radiography is turned into an effective pure photon transport problem, and an iterative solution to the photon transport equation is designed. Then, the solution is turned into a discrete version and realized in a computer program. After, the Monte Carlo N-particle transport code MCNP is used to measure the effective photon scattering function and other parameters needed in the discrete method. Finally, the new computer program is compared with MCNP in a radiography example as a check of the method. It is consistent with MCNP for the radiography of thin objects, but shows large deviation for thick ones. The current computer program can be used in qualitative analysis.
2013,
25: 143-146.
doi: 10.3788/HPLPB20132501.0143
Abstract:
There is growing interest worldwide in very high temperature gas cooled reactors as candidates for next generation reactor systems. For design and analysis of such reactors with double heterogeneity introduced by the coated particle fuels that are randomly distributed in graphite pebbles, stochastic transport models are becoming essential. Several models were reported in the literature, such as coarse lattice models, fine lattice stochastic(FLS) models, random sequential addition (RSA) models, metropolis models. The principles and performance of these stochastic models are described and compared in this paper. Compared with the usual fixed lattice methods, sub-FLS modeling allows more realistic stochastic distribution of fuel particles and thus results in more accurate criticality calculation. Compared with the basic RSA method, sub-FLS modeling requires simpler and more efficient overlapping checking procedure.
There is growing interest worldwide in very high temperature gas cooled reactors as candidates for next generation reactor systems. For design and analysis of such reactors with double heterogeneity introduced by the coated particle fuels that are randomly distributed in graphite pebbles, stochastic transport models are becoming essential. Several models were reported in the literature, such as coarse lattice models, fine lattice stochastic(FLS) models, random sequential addition (RSA) models, metropolis models. The principles and performance of these stochastic models are described and compared in this paper. Compared with the usual fixed lattice methods, sub-FLS modeling allows more realistic stochastic distribution of fuel particles and thus results in more accurate criticality calculation. Compared with the basic RSA method, sub-FLS modeling requires simpler and more efficient overlapping checking procedure.
2013,
25: 147-149.
doi: 10.3788/HPLPB20132501.0147
Abstract:
Based on Monte Carlo simulation method, we apply the multigroup calculation code of the MCNP to simulate the neutron transport equation. A coupled code of the MCNP code and the lattice homogeneous code WIMS is proposed to realize the coupled calculation of criticality and burnup. The specific process is as follows: firstly, the energy group is extended to 69-group owing to the extension of the multigroup calculation character of the MCNP code; secondly, we utilize the interface program to generate 69-group resonance and to transform the self-shield macroscopic neutron cross-section produced by the WIMS code into the multigroup cross-section of ACE format; thirdly, the new cross-section is supplied to the MCNP to finish criticality and burnup calculation; lastly, we use the coupled code to simulate benchmarks and the opposite experiment. The results indicate that the coupled code is correct and rational.
Based on Monte Carlo simulation method, we apply the multigroup calculation code of the MCNP to simulate the neutron transport equation. A coupled code of the MCNP code and the lattice homogeneous code WIMS is proposed to realize the coupled calculation of criticality and burnup. The specific process is as follows: firstly, the energy group is extended to 69-group owing to the extension of the multigroup calculation character of the MCNP code; secondly, we utilize the interface program to generate 69-group resonance and to transform the self-shield macroscopic neutron cross-section produced by the WIMS code into the multigroup cross-section of ACE format; thirdly, the new cross-section is supplied to the MCNP to finish criticality and burnup calculation; lastly, we use the coupled code to simulate benchmarks and the opposite experiment. The results indicate that the coupled code is correct and rational.
2013,
25: 150-152.
doi: 10.3788/HPLPB20132501.0150
Abstract:
In order to decrease the fluctuation of electrons record at imaging plane in MCNPs simulation of X-ray radiography, a new method was tried for creating virtual X-ray source with pointing probability method. The virtual X-ray source may generate the next main electrons which has contribution to the detector. This method can not only increase the possibility of the electron, but also make a history contribute pixels as much as possible. The comparision of the results whether using the proposed method or not was carried out. The results show that the using of the method could decrease the fluctuation of the electrons contribution effectively, improve the presion of the result, and develop the simulation capability of MCNP for X-ray radiography.
In order to decrease the fluctuation of electrons record at imaging plane in MCNPs simulation of X-ray radiography, a new method was tried for creating virtual X-ray source with pointing probability method. The virtual X-ray source may generate the next main electrons which has contribution to the detector. This method can not only increase the possibility of the electron, but also make a history contribute pixels as much as possible. The comparision of the results whether using the proposed method or not was carried out. The results show that the using of the method could decrease the fluctuation of the electrons contribution effectively, improve the presion of the result, and develop the simulation capability of MCNP for X-ray radiography.
2013,
25: 153-157.
doi: 10.3788/HPLPB20132501.0153
Abstract:
In order to simulate the yields of low-energy electrons induced DNA strand breaks, according to D. Emfietzoglous dielectric response theory and Borns correction model, we calculated the inelastic reaction cross sections for low-energy electron transport in liquid water. The physic module on the basis of the Geant4-DNA was established, and also the pre-chemical, chemical, DNA damage analysis modules were established. The yields of DNA strand breaks caused by the different energy electrons uniformly irradiating DNA were simulated, and the simulation results are in good agreement with the published experimental data.
In order to simulate the yields of low-energy electrons induced DNA strand breaks, according to D. Emfietzoglous dielectric response theory and Borns correction model, we calculated the inelastic reaction cross sections for low-energy electron transport in liquid water. The physic module on the basis of the Geant4-DNA was established, and also the pre-chemical, chemical, DNA damage analysis modules were established. The yields of DNA strand breaks caused by the different energy electrons uniformly irradiating DNA were simulated, and the simulation results are in good agreement with the published experimental data.
2013,
25: 158-162.
doi: 10.3788/HPLPB20132501.0158
Abstract:
A particle transport code JMCT, which has independent intellectual property rights, is introduced. The code is developed on the JCOGIN infrastructure with multilayer modules. JMCT is capable to simulate the collision of particles with multi-group energy or continue energy. Two forms of parallelism are supported in JMCT, which are the domain decomposition and domain replication, with good scalability and communication capability. JMCT is equipped with a visualization CAD software which helps to model. The method for simulating the collision of particle with multi-group energy is described in detail. And calculation results of models are consistent with those obtained using the MCNP code. The speed of JMCT is three times faster than the MCNP code and the efficiency of parallelism can get up to 70% on 20 480 CPU cores in simulating 2109 particles.
A particle transport code JMCT, which has independent intellectual property rights, is introduced. The code is developed on the JCOGIN infrastructure with multilayer modules. JMCT is capable to simulate the collision of particles with multi-group energy or continue energy. Two forms of parallelism are supported in JMCT, which are the domain decomposition and domain replication, with good scalability and communication capability. JMCT is equipped with a visualization CAD software which helps to model. The method for simulating the collision of particle with multi-group energy is described in detail. And calculation results of models are consistent with those obtained using the MCNP code. The speed of JMCT is three times faster than the MCNP code and the efficiency of parallelism can get up to 70% on 20 480 CPU cores in simulating 2109 particles.
2013,
25: 163-168.
doi: 10.3788/HPLPB20132501.0163
Abstract:
A collision mechanism based on material rather than nuclide is added in the 3D Monte Carlo neutron and photon transport parallel code MCMG. Geometry cells and surfaces can be dynamically extended. The period of the random number is extended to 261. Combination of multigroup and continuous cross-section transport is developed. The multigroup scattering is expanded to P5 and the upper scattering is considered. Various multigroup libraries can be easily equipped in the code. The same results with the experiments and the MCNP code are obtained for a series of modes. The computation speed of MCMG is 2-4 times faster than the MCNP code.
A collision mechanism based on material rather than nuclide is added in the 3D Monte Carlo neutron and photon transport parallel code MCMG. Geometry cells and surfaces can be dynamically extended. The period of the random number is extended to 261. Combination of multigroup and continuous cross-section transport is developed. The multigroup scattering is expanded to P5 and the upper scattering is considered. Various multigroup libraries can be easily equipped in the code. The same results with the experiments and the MCNP code are obtained for a series of modes. The computation speed of MCMG is 2-4 times faster than the MCNP code.
2013,
25: 169-172.
doi: 10.3788/HPLPB20132501.0169
Abstract:
Geant4 software can not only simulate the interaction processes of rays and material but also the following transportation of optical photons produced by these processes. In this study, the Geant4 particle transport simulation platform was established. The optical coupling efficiency calculation model of the nuclear fusion -ray energy-time joint spectrum detection system was constructed. The optimization method employing the genetic algorithm to call Geant4 code was proposed. The parameters of optical coupling structure were optimized by the genetic algorithm using the gap length in the front of the grid lens, the length of the grin lens, and the gap length at the rear of the grin lens as the independent variables and using the coupling efficiency as the fitness function. Optimization results show that the coupling efficiency between the scintillator and optical fiber could be improved with this method, which is about 4.77%.
Geant4 software can not only simulate the interaction processes of rays and material but also the following transportation of optical photons produced by these processes. In this study, the Geant4 particle transport simulation platform was established. The optical coupling efficiency calculation model of the nuclear fusion -ray energy-time joint spectrum detection system was constructed. The optimization method employing the genetic algorithm to call Geant4 code was proposed. The parameters of optical coupling structure were optimized by the genetic algorithm using the gap length in the front of the grid lens, the length of the grin lens, and the gap length at the rear of the grin lens as the independent variables and using the coupling efficiency as the fitness function. Optimization results show that the coupling efficiency between the scintillator and optical fiber could be improved with this method, which is about 4.77%.
2013,
25: 173-176.
doi: 10.3788/HPLPB20132501.0173
Abstract:
This paper introduces a software infrastructure named J combinatorial geometry Monte Carlo particle transport infrastructure (JCOGIN). The architecture and data structure of JCOGIN and the optimization of computing on the combinatorial geometry are present. Based on JCOGIN, a program used for simulating 3D neutron-photon coupling transport named J Monte Carlo transport (JMCT) is developed, with its performance tested. Results show that JMCT reaches the parallel efficiency 70% in the simulation of 2 billion particles on 20 480 cores for an outside source.
This paper introduces a software infrastructure named J combinatorial geometry Monte Carlo particle transport infrastructure (JCOGIN). The architecture and data structure of JCOGIN and the optimization of computing on the combinatorial geometry are present. Based on JCOGIN, a program used for simulating 3D neutron-photon coupling transport named J Monte Carlo transport (JMCT) is developed, with its performance tested. Results show that JMCT reaches the parallel efficiency 70% in the simulation of 2 billion particles on 20 480 cores for an outside source.
2013,
25: 177-181.
doi: 10.3788/HPLPB20132501.0177
Abstract:
The model of Z-pinch driven fusion imaging diagnosis system was set up by a Monte Carlo code based on the Geant4 simulation toolkit. All physical processes that the reality involves are taken into consideration in simulation. The light image of low neutron yield (about 1010) pill was obtained. Three types of image reconstruction algorithm, i.e. Richardson-Lucy, Wiener filtering and genetic algorithm were employed to reconstruct the neutron image with a low signal to noise ratio (SNR) and yield. The effects of neutron yields and the SNR on reconstruction performance were discussed. The results show that genetic algorithm is very robust for reconstructing neutron images with a low SNR. And the index of reconstruction performance and the image correlation coefficient using genetic algorithm, are proportional to the SNR of the neutron coded image.
The model of Z-pinch driven fusion imaging diagnosis system was set up by a Monte Carlo code based on the Geant4 simulation toolkit. All physical processes that the reality involves are taken into consideration in simulation. The light image of low neutron yield (about 1010) pill was obtained. Three types of image reconstruction algorithm, i.e. Richardson-Lucy, Wiener filtering and genetic algorithm were employed to reconstruct the neutron image with a low signal to noise ratio (SNR) and yield. The effects of neutron yields and the SNR on reconstruction performance were discussed. The results show that genetic algorithm is very robust for reconstructing neutron images with a low SNR. And the index of reconstruction performance and the image correlation coefficient using genetic algorithm, are proportional to the SNR of the neutron coded image.
2013,
25: 182-188.
doi: 10.3788/HPLPB20132501.0182
Abstract:
A new mathematical phantom, the Chinese MIRD (CMIRD), was developed based on the high-resolution data set of Visible Chinese Human (VCH). The position and size of organs were obtained from the voxel-based VCH model, using the minimal 3D bounding box method. According to the equations of the ORNL adult phantom, the original CMIRD based on that anatomic information was constructed and the method of proportional deformation was adopted in order to compare the external radiation dose of different height models for different radiation directions and particles with MCNPX. The stimulation results obtained from CMIRD present comparable to those published dose values. The analysis of the discrepancies indicates that the shape, location and mass of organs have great influence on radiation dose especially at low energies. The comparison of the effective doses for models with different size shows that the size of the model is important, and the smaller models receive larger doses. Also, the deeper organs present more sensitive to the organ size than the shallower ones. In addition, the mathematical model is superior in speed of the radiation dose calculation, which requires simpler definition and less memory space.
A new mathematical phantom, the Chinese MIRD (CMIRD), was developed based on the high-resolution data set of Visible Chinese Human (VCH). The position and size of organs were obtained from the voxel-based VCH model, using the minimal 3D bounding box method. According to the equations of the ORNL adult phantom, the original CMIRD based on that anatomic information was constructed and the method of proportional deformation was adopted in order to compare the external radiation dose of different height models for different radiation directions and particles with MCNPX. The stimulation results obtained from CMIRD present comparable to those published dose values. The analysis of the discrepancies indicates that the shape, location and mass of organs have great influence on radiation dose especially at low energies. The comparison of the effective doses for models with different size shows that the size of the model is important, and the smaller models receive larger doses. Also, the deeper organs present more sensitive to the organ size than the shallower ones. In addition, the mathematical model is superior in speed of the radiation dose calculation, which requires simpler definition and less memory space.
2013,
25: 189-192.
doi: 10.3788/HPLPB20132501.0189
Abstract:
For 24Na activity measurement of human body activated by neutron irradiation in the supercritical accident, the MCNP code is used to create a Monte Carlo simulation model. Two--ray total-energy peak detection efficiency of 24Na decay using different types of NaI detectors, and total -ray number detection efficiency of 24Na decay using plastic scintillator detector are simulated. The simulation results show that, for the 1.38 MeV and 2.76 MeV rays of 24Na decay, the efficiency of the well-type NaI detector is 4.30 times and 4.11 times that of the cylindrical one; the -ray detection efficiency of 24Na decay using the plastic scintillator detector is 1.72 times the 24Na ray detection efficiencyusing the NaI detector. Meanwhile, a rough calculation of the relationship between the detector counts and the neutron irradiation dose of human body is carried out.
For 24Na activity measurement of human body activated by neutron irradiation in the supercritical accident, the MCNP code is used to create a Monte Carlo simulation model. Two--ray total-energy peak detection efficiency of 24Na decay using different types of NaI detectors, and total -ray number detection efficiency of 24Na decay using plastic scintillator detector are simulated. The simulation results show that, for the 1.38 MeV and 2.76 MeV rays of 24Na decay, the efficiency of the well-type NaI detector is 4.30 times and 4.11 times that of the cylindrical one; the -ray detection efficiency of 24Na decay using the plastic scintillator detector is 1.72 times the 24Na ray detection efficiencyusing the NaI detector. Meanwhile, a rough calculation of the relationship between the detector counts and the neutron irradiation dose of human body is carried out.
2013,
25: 193-195.
doi: 10.3788/HPLPB20132501.0193
Abstract:
The convolution core is the key factor to calculate dose with the convolution method in single-photon emission computed tomography (SPECT) diagnosis. The Monte Carlo (MC) technology was used to investigate the dose characteristic of the SPECT diagnosis with the radioactive isotope 131I. The expression of the 131I decay was given and was used to achieve the simulation of the electron and the photon of one decay of the 131I. The SPECT object is a spherical water phantom. The MC simulation results not only show that 131I can cure the hypothyroid caner and almost has no harm to the normal tissue, but also verify that the requirement of the self-adaption convolution core is met, for the relationship between the deposited energy and the areal mass is nothing to the density. The convolution core is gained by the MC simulation and is very useful to fast dose calculation.
The convolution core is the key factor to calculate dose with the convolution method in single-photon emission computed tomography (SPECT) diagnosis. The Monte Carlo (MC) technology was used to investigate the dose characteristic of the SPECT diagnosis with the radioactive isotope 131I. The expression of the 131I decay was given and was used to achieve the simulation of the electron and the photon of one decay of the 131I. The SPECT object is a spherical water phantom. The MC simulation results not only show that 131I can cure the hypothyroid caner and almost has no harm to the normal tissue, but also verify that the requirement of the self-adaption convolution core is met, for the relationship between the deposited energy and the areal mass is nothing to the density. The convolution core is gained by the MC simulation and is very useful to fast dose calculation.
2013,
25: 196-200.
doi: 10.3788/HPLPB20132501.0196
Abstract:
The removal cross section method and the buildup factor method have been used to calculate the dose equivalent distribution of neutron and gamma rays permeating through the primary shielding layer of underwater radiator respectively. With this distribution, Cherenkov light spectrum and flux distribution in 3 m water layer radiator after -rays permeating through secondary shielding layer and follow-up water layer have been simulated with Geant4. In addition, considering the geometry dilution and water attenuation for Cherenkov light propagating through some thickness of the pure water layer, the size of Cherenkov light spot and the intensity distribution were obtained.
The removal cross section method and the buildup factor method have been used to calculate the dose equivalent distribution of neutron and gamma rays permeating through the primary shielding layer of underwater radiator respectively. With this distribution, Cherenkov light spectrum and flux distribution in 3 m water layer radiator after -rays permeating through secondary shielding layer and follow-up water layer have been simulated with Geant4. In addition, considering the geometry dilution and water attenuation for Cherenkov light propagating through some thickness of the pure water layer, the size of Cherenkov light spot and the intensity distribution were obtained.
2013,
25: 201-206.
doi: 10.3788/HPLPB20132501.0201
Abstract:
Combining MCNP5 simulation with mathematical computation and utilizing the axial symmetry of detector-crystal geometry, a source-less efficiency calibration method to an HPGe detector is established. The computer code based on this method can calibrate the efficiency of point sources and coaxial cylinder sources without need for MCNP5 in its using process and its runtime is 1 s-1 min. The applicable energy range is 50 keV-3 MeV. Comparing self-written codes result with experimental data and MCNP5s simulation result, the error is below 12 percent and 7 percent respectively, which proves the method is feasibility.
Combining MCNP5 simulation with mathematical computation and utilizing the axial symmetry of detector-crystal geometry, a source-less efficiency calibration method to an HPGe detector is established. The computer code based on this method can calibrate the efficiency of point sources and coaxial cylinder sources without need for MCNP5 in its using process and its runtime is 1 s-1 min. The applicable energy range is 50 keV-3 MeV. Comparing self-written codes result with experimental data and MCNP5s simulation result, the error is below 12 percent and 7 percent respectively, which proves the method is feasibility.
2013,
25: 207-210.
doi: 10.3788/HPLPB20132501.0207
Abstract:
A Faraday cup is an absolute measuring equipment used to measure the accelerator beam intensity, so the calculation of the collection efficiency is of the utmost importance. The Monte Carlo simulation is one of the important methods for simulating the particle transport process and analyzing the energy deposition. A Faraday cup to be installed around the analysis magnet AM2 in the linac of BEPCII, was simulated using the Monte Carlo program, FLUKA. The curves of collection efficiency vs the different parts of Faraday cup structure wereobtained, the energy deposition distribution and the charged particle distribution of the incident electrons were also simulated, and finally the optimization designed size of the Faraday cup was given.
A Faraday cup is an absolute measuring equipment used to measure the accelerator beam intensity, so the calculation of the collection efficiency is of the utmost importance. The Monte Carlo simulation is one of the important methods for simulating the particle transport process and analyzing the energy deposition. A Faraday cup to be installed around the analysis magnet AM2 in the linac of BEPCII, was simulated using the Monte Carlo program, FLUKA. The curves of collection efficiency vs the different parts of Faraday cup structure wereobtained, the energy deposition distribution and the charged particle distribution of the incident electrons were also simulated, and finally the optimization designed size of the Faraday cup was given.
2013,
25: 211-214.
doi: 10.3788/HPLPB20132501.0211
Abstract:
The Monte Carlo models for studying the quantum efficiency and the split pixel event of PI-LCX: 1300charge coupled device (CCD) were set up. The X-ray transport in the CCD chips was simulated using the Monte Carlo code Geant4 in the energy range of 0.5~30.0 keV. The energy deposit spectra of X-ray in CCD chips were investigated, the subsequent quantum efficiency obtained is in good agreement with that offered by the manufacturer. Simulation results show that the efficiency increase with increasing the thickness of the Si layer and this effect is not obvious for high energy X-rays. The deposited energy spread in multi-pixels was studied. It shows that the surrounding pixels split the incident photon energy by deriving from the characteristic and Rayleigh scattering X-rays, which are generated in the central pixel but escape from it. In the range of 5~30 keV, the energy deposit efficiency and the effect of the multi-pixel pollution decrease as the X-ray energy increases.
The Monte Carlo models for studying the quantum efficiency and the split pixel event of PI-LCX: 1300charge coupled device (CCD) were set up. The X-ray transport in the CCD chips was simulated using the Monte Carlo code Geant4 in the energy range of 0.5~30.0 keV. The energy deposit spectra of X-ray in CCD chips were investigated, the subsequent quantum efficiency obtained is in good agreement with that offered by the manufacturer. Simulation results show that the efficiency increase with increasing the thickness of the Si layer and this effect is not obvious for high energy X-rays. The deposited energy spread in multi-pixels was studied. It shows that the surrounding pixels split the incident photon energy by deriving from the characteristic and Rayleigh scattering X-rays, which are generated in the central pixel but escape from it. In the range of 5~30 keV, the energy deposit efficiency and the effect of the multi-pixel pollution decrease as the X-ray energy increases.
2013,
25: 215-218.
doi: 10.3788/HPLPB20132501.0215
Abstract:
In energy dispersive X-ray fluorescence (EDXRF) techniques, the inter-element effect can influence the analysis accuracy seriously. The Monte Carlo simulation method was adopted to simulate the Si(PIN) detector based EDXRF system, and a new Gaussian broadening algorithm was established for the flux spectrum. As compared with the experiment energy spectra of Fe and Ni, the flux spectrum after broadening fits the K characteristic X-ray spectrum much better. The relationship curve between normalized count and content of each element is obtained. Results show that this method can correct inter-element effect automatically and provide theoretical intensity of the K line characteristic X-ray spectrum.
In energy dispersive X-ray fluorescence (EDXRF) techniques, the inter-element effect can influence the analysis accuracy seriously. The Monte Carlo simulation method was adopted to simulate the Si(PIN) detector based EDXRF system, and a new Gaussian broadening algorithm was established for the flux spectrum. As compared with the experiment energy spectra of Fe and Ni, the flux spectrum after broadening fits the K characteristic X-ray spectrum much better. The relationship curve between normalized count and content of each element is obtained. Results show that this method can correct inter-element effect automatically and provide theoretical intensity of the K line characteristic X-ray spectrum.
2013,
25: 219-222.
doi: 10.3788/HPLPB20132501.0219
Abstract:
This paper describes repeat geometry structure function and its application to reactor analysis Monte Carlo codes. Common repeat structure output and implementation is introduced using MCNP and RMC (RMC is a reactor Monte Carlo code developed by REAL team in Department of Engineering Physics, Tsinghua University) as examples, and three speed-up methods for layer geometry structure and repeat geometry structure in RMC are presented. Examples of the Daya Bay reactor are calculated for comparison between MCNP and RMC, and results show that RMC speeds up by 3-9 times, compared with MCNP.
This paper describes repeat geometry structure function and its application to reactor analysis Monte Carlo codes. Common repeat structure output and implementation is introduced using MCNP and RMC (RMC is a reactor Monte Carlo code developed by REAL team in Department of Engineering Physics, Tsinghua University) as examples, and three speed-up methods for layer geometry structure and repeat geometry structure in RMC are presented. Examples of the Daya Bay reactor are calculated for comparison between MCNP and RMC, and results show that RMC speeds up by 3-9 times, compared with MCNP.
2013,
25: 223-226.
doi: 10.3788/HPLPB20132501.0223
Abstract:
Calculating the dose around radioactive source by simulation is an important way of radiation analysis and application. It is widely used in engineering. The paper uses a simple decay cascade to analyze the Pu-238 source, and obtains the varying trends of atomic number and activity for the source and its daughters. In view of the above-mentioned situation, it sets up an elaborate model by MCNP code, calculating the radioactive field and the problem about shield and getting the gamma and neutron energy spectra around the source. The result agrees with the reference, the shield used can reduce the dose effectively. Concretely, the dose of gamma is reduce to about 0.1%, and the neutron, 13%~17%.
Calculating the dose around radioactive source by simulation is an important way of radiation analysis and application. It is widely used in engineering. The paper uses a simple decay cascade to analyze the Pu-238 source, and obtains the varying trends of atomic number and activity for the source and its daughters. In view of the above-mentioned situation, it sets up an elaborate model by MCNP code, calculating the radioactive field and the problem about shield and getting the gamma and neutron energy spectra around the source. The result agrees with the reference, the shield used can reduce the dose effectively. Concretely, the dose of gamma is reduce to about 0.1%, and the neutron, 13%~17%.
2013,
25: 227-232.
doi: 10.3788/HPLPB20132501.0227
Abstract:
High temperature gas cooled reactor-pebble bed module (HTR-PM) adopts the coated particle spherical fuel elements, during the reactor's running, the constantly discharged spent fuel spheres will be loaded into the spent fuel tank. The spent fuel tank should use proper materials and thicknesses to shield gammas and neutrons effectively, and guarantee the dose limit not to be exceeded outside the tanks. Both relaxation length method and Monte Carlo simulation method were employed to study the neutrons' shielding capabilities of the spent fuel tank. Iron and borated polyethylene were chosen to be the shielding materials. The shielding capabilities of iron and borated polyethylene with different B4C contents (mass fraction 0, 5%, 10% and 15%) were calculated. The effect of the spent fuel spheres self-absorption to the dose rate outside the tank was also considered, when the tank was full of the spent fuel spheres. The calculation results of these two methods are in good agreement, and provide important guiding suggestions for the shielding design in the practical engineering.
High temperature gas cooled reactor-pebble bed module (HTR-PM) adopts the coated particle spherical fuel elements, during the reactor's running, the constantly discharged spent fuel spheres will be loaded into the spent fuel tank. The spent fuel tank should use proper materials and thicknesses to shield gammas and neutrons effectively, and guarantee the dose limit not to be exceeded outside the tanks. Both relaxation length method and Monte Carlo simulation method were employed to study the neutrons' shielding capabilities of the spent fuel tank. Iron and borated polyethylene were chosen to be the shielding materials. The shielding capabilities of iron and borated polyethylene with different B4C contents (mass fraction 0, 5%, 10% and 15%) were calculated. The effect of the spent fuel spheres self-absorption to the dose rate outside the tank was also considered, when the tank was full of the spent fuel spheres. The calculation results of these two methods are in good agreement, and provide important guiding suggestions for the shielding design in the practical engineering.
2013,
25: 233-236.
doi: 10.3788/HPLPB20132501.0233
Abstract:
In order to develop the research on 129I transmutation in the thermal reactor, 127I target was irradiated in Xian pulsed reactor(XAPR) to explore the condition for experiment in XAPR. The Monte Carlo method was used in the calculation of 127I target transmutation rate, and the results were compared with the experimental data. The NJOY software was used to generate 127I ace format neutron cross section at XAPR operating temperature based on ENDF/B VII.0 library. New cross section was compared with old ENDF/B VI library and developed in the unresolved resonance region. MCNP was used to modify the 127I cross section of ORIGEN2 by adopting a new cross section, then transmutation of 127I target was calculated to analyze changes of transmutation rate and nuclides, also the influence of neutron spectrum and irradiating time on transmutation was studied. The CINDER90 software, a depletion mode of MCNPX, was also used to model the transmutation condition, the analytical result was consistent with ORIGEN2, but was a little different from the experimental data (2%-3% error) because of the deviation from the MCNP model in neutron flux calculation.
In order to develop the research on 129I transmutation in the thermal reactor, 127I target was irradiated in Xian pulsed reactor(XAPR) to explore the condition for experiment in XAPR. The Monte Carlo method was used in the calculation of 127I target transmutation rate, and the results were compared with the experimental data. The NJOY software was used to generate 127I ace format neutron cross section at XAPR operating temperature based on ENDF/B VII.0 library. New cross section was compared with old ENDF/B VI library and developed in the unresolved resonance region. MCNP was used to modify the 127I cross section of ORIGEN2 by adopting a new cross section, then transmutation of 127I target was calculated to analyze changes of transmutation rate and nuclides, also the influence of neutron spectrum and irradiating time on transmutation was studied. The CINDER90 software, a depletion mode of MCNPX, was also used to model the transmutation condition, the analytical result was consistent with ORIGEN2, but was a little different from the experimental data (2%-3% error) because of the deviation from the MCNP model in neutron flux calculation.
2013,
25: 237-240.
doi: 10.3788/HPLPB20132501.0237
Abstract:
The neutron flux density plays a very important role in reactor kinetics. The Monte Carlo code MCNP is used to calculate the neutron generation time of Xian Pulsed Reactor. First the decay of neutron flux density is simulated with MCNP and then the neutron generation time is calculated based on the point-reactor kinetics equation. In the slightly subcritical reactor, the effect of subcriticality, count region and distribution of the neutron source on the results are studied. The calculation indicates that the subcriticality, count region and distribution of the neutron source affect the neutron generation time very little. The dominant error is that the decay of prompt neutron density cannot be precisely described with the point-reactor kinetics equation.
The neutron flux density plays a very important role in reactor kinetics. The Monte Carlo code MCNP is used to calculate the neutron generation time of Xian Pulsed Reactor. First the decay of neutron flux density is simulated with MCNP and then the neutron generation time is calculated based on the point-reactor kinetics equation. In the slightly subcritical reactor, the effect of subcriticality, count region and distribution of the neutron source on the results are studied. The calculation indicates that the subcriticality, count region and distribution of the neutron source affect the neutron generation time very little. The dominant error is that the decay of prompt neutron density cannot be precisely described with the point-reactor kinetics equation.
2013,
25: 241-244.
doi: 10.3788/HPLPB20132501.0241
Abstract:
Bremsstrahlung X-rays are generated when the ultra-short ultra-intense laser interacts with solid targets. The transport of hot electrons in solid targets and the generation of bremsstrahlung X-rays were simulated using Monte Carlo method. Simulation results of the bremsstrahlung produced by 1 MeV electrons interacting with targets show that the slopes of high energy part of bremsstrahlung spectra can not be influenced obviously by target thickness and target material. Simulation of Maxwellian distribution and mono-energetic electron beams interacting with a 30 m thick Cu target shows that the bremsstrahlung photon spectra from these two electron sources are in agreement with each other. A scaling method of hot electron temperature according to the slope of high energy part of the bremsstrahlung spectrum is presented. The bremsstrahlung energy and number angular distributions were studied for different hot electron temperatures. The results indicate that the forward peaking trait of angular distributions can be enhanced by increasing the electron temperature, thus another scaling method based on this relation is proposed.
Bremsstrahlung X-rays are generated when the ultra-short ultra-intense laser interacts with solid targets. The transport of hot electrons in solid targets and the generation of bremsstrahlung X-rays were simulated using Monte Carlo method. Simulation results of the bremsstrahlung produced by 1 MeV electrons interacting with targets show that the slopes of high energy part of bremsstrahlung spectra can not be influenced obviously by target thickness and target material. Simulation of Maxwellian distribution and mono-energetic electron beams interacting with a 30 m thick Cu target shows that the bremsstrahlung photon spectra from these two electron sources are in agreement with each other. A scaling method of hot electron temperature according to the slope of high energy part of the bremsstrahlung spectrum is presented. The bremsstrahlung energy and number angular distributions were studied for different hot electron temperatures. The results indicate that the forward peaking trait of angular distributions can be enhanced by increasing the electron temperature, thus another scaling method based on this relation is proposed.
2013,
25: 245-247.
doi: 10.3788/HPLPB20132501.0245
Abstract:
Anomalous transport of inertial Levy flight subject to nonlinear friction in force-free potential is studied. By introducing velocity-dependent nonlinear friction, long-jump Levy particles are constrained, and the dynamical behavior of the particles is changed to normal diffusion. It is observed that velocity probability distribution shows bimodal model distribution. Moreover, the bimodal model is connected with Levy index and nonlinear index.
Anomalous transport of inertial Levy flight subject to nonlinear friction in force-free potential is studied. By introducing velocity-dependent nonlinear friction, long-jump Levy particles are constrained, and the dynamical behavior of the particles is changed to normal diffusion. It is observed that velocity probability distribution shows bimodal model distribution. Moreover, the bimodal model is connected with Levy index and nonlinear index.
2013,
25: 248-252.
doi: 10.3788/HPLPB20132501.0248
Abstract:
Based on the linear nuclide chain method and the burn-up features of reactors, the depletion nuclide database is established and the densities of all the nuclides in the burnup system are calculated using the backtracking algorithm. The depletion code can solve the burn-up problem independently and have integrated output form, which makes it convenient to couple with the Monte Carlo program by the interface module to do the coupling transport-depletion calculation for reactor systems. The benchmark burn-up of the first core of China Experimental Fast Reactor(CEFR) is calculated with the transport-depletion code to verify the function correctness. The comparison with the results obtained already using other codes shows that the new depletion program can calculate the density of actinides with high fidelity, including fissionable nuclides and some minor actinides with puny yields. There is difference with the inventory of Pu241. This should be analyzed further to determinate whether the difference comes from the depletion program or from the related cross section data. The calculation results of fission products and reactivity tally with the designed results well.
Based on the linear nuclide chain method and the burn-up features of reactors, the depletion nuclide database is established and the densities of all the nuclides in the burnup system are calculated using the backtracking algorithm. The depletion code can solve the burn-up problem independently and have integrated output form, which makes it convenient to couple with the Monte Carlo program by the interface module to do the coupling transport-depletion calculation for reactor systems. The benchmark burn-up of the first core of China Experimental Fast Reactor(CEFR) is calculated with the transport-depletion code to verify the function correctness. The comparison with the results obtained already using other codes shows that the new depletion program can calculate the density of actinides with high fidelity, including fissionable nuclides and some minor actinides with puny yields. There is difference with the inventory of Pu241. This should be analyzed further to determinate whether the difference comes from the depletion program or from the related cross section data. The calculation results of fission products and reactivity tally with the designed results well.
2013,
25: 253-258.
doi: 10.3788/HPLPB20132501.0253
Abstract:
D-T neutron source model is developed according to the neutron spectrum and the neutron angular distribution of D-T reaction. A standard calibration well model is built. The transports of D-T neutron and -ray in the well are simulated using MCNP code. Mixed -spectrum and inelastic -spectrum in the NaI detector are obtained for different distance and different density. The data of the mixed gamma count in the energy range of 2.5 to 4.5 MeV as a function of distance show that the detector should be located in the space of 20-80 cm. The nonlinear relationships between the density and the mixed gamma count are presented. The data of the inelastic gamma count in the energy range of 1.0 to 8.0 MeV as a function of distance show that the detector should be located in the space of 20-40 cm or in the neighborhood of 80 cm. The relationships between the density and the inelastic gamma count can be approximatively expressed as a linear function.
D-T neutron source model is developed according to the neutron spectrum and the neutron angular distribution of D-T reaction. A standard calibration well model is built. The transports of D-T neutron and -ray in the well are simulated using MCNP code. Mixed -spectrum and inelastic -spectrum in the NaI detector are obtained for different distance and different density. The data of the mixed gamma count in the energy range of 2.5 to 4.5 MeV as a function of distance show that the detector should be located in the space of 20-80 cm. The nonlinear relationships between the density and the mixed gamma count are presented. The data of the inelastic gamma count in the energy range of 1.0 to 8.0 MeV as a function of distance show that the detector should be located in the space of 20-40 cm or in the neighborhood of 80 cm. The relationships between the density and the inelastic gamma count can be approximatively expressed as a linear function.
2013,
25: 259-262.
doi: 10.3788/HPLPB20132501.0259
Abstract:
Detecting total quantity and depth profile of tritium for volume phase of metal tritiated compound is a key problem in behavior research of tritium. In this paper, depth profiling of tritium is studied by the tritium beta decay to induce X ray spectrum(??IXS),and a mechanics model for depth profiling of tritium calculating in tritium film target is established. Inversion of depth profile of tritium is performed by Tikhonov regularization method. The inversion results indicated that the regularization method can avoid ill-condition inverse problems, and the method can enhance effectively the resolution in heterogeneity of normal direction of the tritium film target.
Detecting total quantity and depth profile of tritium for volume phase of metal tritiated compound is a key problem in behavior research of tritium. In this paper, depth profiling of tritium is studied by the tritium beta decay to induce X ray spectrum(??IXS),and a mechanics model for depth profiling of tritium calculating in tritium film target is established. Inversion of depth profile of tritium is performed by Tikhonov regularization method. The inversion results indicated that the regularization method can avoid ill-condition inverse problems, and the method can enhance effectively the resolution in heterogeneity of normal direction of the tritium film target.
2013,
25: 263-268.
doi: 10.3788/HPLPB20132501.0263
Abstract:
Non-equilibrium systems have been observed at almost all levels of natural and manmade systems, which are characterized by non-zero continuous traffic currents. The totally asymmetric simple exclusion process (TASEP) has been regarded as a paradigm for modeling and simulation of such non-equilibrium dynamic systems. These TASEP systems are simulated with Monte Carlo methods and analyzed using mean field approaches in this paper. Some interesting physical phenomena such as spontaneous symmetry breaking, finite-size effect, and flipping process, were observed via Monte Carlo simulations, and are discussed in detail. More careful Monte Carlo simulations are suggested to confirm the finite-size effect argued in the literature.
Non-equilibrium systems have been observed at almost all levels of natural and manmade systems, which are characterized by non-zero continuous traffic currents. The totally asymmetric simple exclusion process (TASEP) has been regarded as a paradigm for modeling and simulation of such non-equilibrium dynamic systems. These TASEP systems are simulated with Monte Carlo methods and analyzed using mean field approaches in this paper. Some interesting physical phenomena such as spontaneous symmetry breaking, finite-size effect, and flipping process, were observed via Monte Carlo simulations, and are discussed in detail. More careful Monte Carlo simulations are suggested to confirm the finite-size effect argued in the literature.
