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RSS2017 Vol. 29, No. 12
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2017,
29: 120101.
doi: 10.11884/HPLPB201729.170396
Abstract:
The scheme of tandem pumping has drawn a lot of interest in fiber laser field for their outstanding characteristics, which include high-brightness, low quantum defect, and great potential for power scaling. The 1018 nm laser can be used as an efficient tandem pumping source for high-power ytterbium fiber laser, but it is difficult to improve signal fiber laser output power. One of the efficiency methods to break through this limitation is beam combining. In this paper, based on 19 single-mode 1018 nm fiber lasers and a 191 fiber combiner, we setup an all-fiber schematic laser combining system, and achieve 5 kW laser output with 1018 nm.
The scheme of tandem pumping has drawn a lot of interest in fiber laser field for their outstanding characteristics, which include high-brightness, low quantum defect, and great potential for power scaling. The 1018 nm laser can be used as an efficient tandem pumping source for high-power ytterbium fiber laser, but it is difficult to improve signal fiber laser output power. One of the efficiency methods to break through this limitation is beam combining. In this paper, based on 19 single-mode 1018 nm fiber lasers and a 191 fiber combiner, we setup an all-fiber schematic laser combining system, and achieve 5 kW laser output with 1018 nm.
2017,
29: 120102.
doi: 10.11884/HPLPB201729.170391
Abstract:
Recent experiments on Shenguang Ⅲ laser facility have explored gas filled hohlraums to create plasma condition that is close to the ignition status. An X-ray framing camera was used to acquire the time-resolved movement images of the gold bubbles. The experimental results are simulated with a phenomenological model very well, demonstrating its validity and rationality.
Recent experiments on Shenguang Ⅲ laser facility have explored gas filled hohlraums to create plasma condition that is close to the ignition status. An X-ray framing camera was used to acquire the time-resolved movement images of the gold bubbles. The experimental results are simulated with a phenomenological model very well, demonstrating its validity and rationality.
2017,
29: 121001.
doi: 10.11884/HPLPB201729.170106
Abstract:
In order to output high frequency modulation, we designed a high frequency modulation system of semiconductor laser which is composed of a signal magnifying circuit, a current modulation circuit, an over current protection circuit and a DC bias circuit with slow start function. The high frequency modulation drive system of semiconductor laser uses a simple structure of the direct modulation method. The direct modulation method controls intensity of semiconductor laser by a signal of adjustable frequency. We simulated the high frequency modulation drive system of semiconductor laser by OrCAD/Pspice. The high frequency modulation system of the semiconductor laser can output laser with frequency of 40.02 MHz and average laser power of 300 mW, and it can output modulation current with DC bias of 493.326 mA and peak value of sine wave modulation of 850 mA.
In order to output high frequency modulation, we designed a high frequency modulation system of semiconductor laser which is composed of a signal magnifying circuit, a current modulation circuit, an over current protection circuit and a DC bias circuit with slow start function. The high frequency modulation drive system of semiconductor laser uses a simple structure of the direct modulation method. The direct modulation method controls intensity of semiconductor laser by a signal of adjustable frequency. We simulated the high frequency modulation drive system of semiconductor laser by OrCAD/Pspice. The high frequency modulation system of the semiconductor laser can output laser with frequency of 40.02 MHz and average laser power of 300 mW, and it can output modulation current with DC bias of 493.326 mA and peak value of sine wave modulation of 850 mA.
2017,
29: 121002.
doi: 10.11884/HPLPB201729.170204
Abstract:
The closed diluted gas cycle chemical oxygen iodine laser (CGC-COIL) was considered as a promising miniaturized laser; however, we havent read any experimental study reports till now. In this study, a simulation experiment setup composed of supersonic nozzle and screw vacuum pump was built, and it was used to study the feasibility and the operation stability of CGC-COIL by means of measuring the inlet and outlet aerodynamic parameters of the supersonic nozzle and screw vacuum pump. The simulation experiments firstly demonstrated the feasibility of this type of laser, and then confirmed the optimal stable operation condition of this type of laser by finding and explicating the phenomenon that a simulation laser cavity pressure inflection point will appear with the increase of the revolving speed of screw pump. The study provides an experimental evidence for CGC-COIL realization and a new technological approach for chemical oxygen iodine laser miniaturization.
The closed diluted gas cycle chemical oxygen iodine laser (CGC-COIL) was considered as a promising miniaturized laser; however, we havent read any experimental study reports till now. In this study, a simulation experiment setup composed of supersonic nozzle and screw vacuum pump was built, and it was used to study the feasibility and the operation stability of CGC-COIL by means of measuring the inlet and outlet aerodynamic parameters of the supersonic nozzle and screw vacuum pump. The simulation experiments firstly demonstrated the feasibility of this type of laser, and then confirmed the optimal stable operation condition of this type of laser by finding and explicating the phenomenon that a simulation laser cavity pressure inflection point will appear with the increase of the revolving speed of screw pump. The study provides an experimental evidence for CGC-COIL realization and a new technological approach for chemical oxygen iodine laser miniaturization.
2017,
29: 123001.
doi: 10.11884/HPLPB201729.170136
Abstract:
For the development demand of the compact high power microwave systems, more compact antenna and feed line come as a solution. A noval Compact TE31-TE11 high power microwave mode convertor was proposed based on the electro-magnetic field distribution characters of the two modes, and a novel sleeve structure with eight mirror imaged long-axis slots was employed to convert TE31 mode generated from relativity magnetron to TE11 mode suitable for directed radiation. By optimization of the geometric parameters of the convertor based on full wave simulation, the conversion efficiency is as high as 99% at the work frequency, and its percent bandwidth is 11% for conversion efficiency higher than 95%. Simulation of the convertor in vacuum shows that its theoretical transient power capacity could be 3.4 GW.
For the development demand of the compact high power microwave systems, more compact antenna and feed line come as a solution. A noval Compact TE31-TE11 high power microwave mode convertor was proposed based on the electro-magnetic field distribution characters of the two modes, and a novel sleeve structure with eight mirror imaged long-axis slots was employed to convert TE31 mode generated from relativity magnetron to TE11 mode suitable for directed radiation. By optimization of the geometric parameters of the convertor based on full wave simulation, the conversion efficiency is as high as 99% at the work frequency, and its percent bandwidth is 11% for conversion efficiency higher than 95%. Simulation of the convertor in vacuum shows that its theoretical transient power capacity could be 3.4 GW.
2017,
29: 123201.
doi: 10.11884/HPLPB201729.170266
Abstract:
In order to solve the problem that the environment E-field intensity is difficult to measure when the radiation susceptibility test is carried out in the reverberation chamber, this article analyzes the statistical characteristics of E-field intensity in reverberation chamber, theoretically derives the representation of E-fields spatial correlation function in lossy reverberation chamber, then verifies the correctness of the representation by simulation analysis. From the representation, we can draw the conclusion that in lossy reverberation chamber the E-fields at two points whose distance is greater than half-wavelength are mutually independent. Therefore in E-field intensity measurement in reverberation chamber, the distance between measurement position and EUT should be greater than 0.5, which can be taken as a selection criterion. Finally, the method of combining numerical calculation with experimental verification is adopted to analyze the relationship between relative error and relative distance, and the criteria is verified. The relative error of distribution parameter () at different relative distances is simulated and analyzed. It is concluded that the relative error can be decreased to 1.5 dB as long as the relative distance is more than 0.5, which can be applied to the actual environment E-field intensity test in reverberation chamber.
In order to solve the problem that the environment E-field intensity is difficult to measure when the radiation susceptibility test is carried out in the reverberation chamber, this article analyzes the statistical characteristics of E-field intensity in reverberation chamber, theoretically derives the representation of E-fields spatial correlation function in lossy reverberation chamber, then verifies the correctness of the representation by simulation analysis. From the representation, we can draw the conclusion that in lossy reverberation chamber the E-fields at two points whose distance is greater than half-wavelength are mutually independent. Therefore in E-field intensity measurement in reverberation chamber, the distance between measurement position and EUT should be greater than 0.5, which can be taken as a selection criterion. Finally, the method of combining numerical calculation with experimental verification is adopted to analyze the relationship between relative error and relative distance, and the criteria is verified. The relative error of distribution parameter () at different relative distances is simulated and analyzed. It is concluded that the relative error can be decreased to 1.5 dB as long as the relative distance is more than 0.5, which can be applied to the actual environment E-field intensity test in reverberation chamber.
2017,
29: 123202.
doi: 10.11884/HPLPB201729.170174
Abstract:
The statistical characteristic of an aircrafts dynamic radar cross section(RCS) is affected by its movement state greatly. The same aircraft in different flying state presents different RCS statistical model. In this paper, the RCS obtained from the surveying radar is analyzed in both states of straight level stable flying and maneuvering flying. The analysis shows that the statistical characteristics of dynamic RCS of the two flight states are different. The statistical characteristic of dynamic RCS of the aircraft that fly straightly and level stably is approximately the same as static RCS. The fluctuant characteristic of dynamic RCS of the aircraft in the state of maneuvering flight is remarkable and stochastic. As the measurement time is long enough, the statistical characteristic of dynamic RCS of the aircraft in the state of maneuvering flight is more close to exponential distribution.
The statistical characteristic of an aircrafts dynamic radar cross section(RCS) is affected by its movement state greatly. The same aircraft in different flying state presents different RCS statistical model. In this paper, the RCS obtained from the surveying radar is analyzed in both states of straight level stable flying and maneuvering flying. The analysis shows that the statistical characteristics of dynamic RCS of the two flight states are different. The statistical characteristic of dynamic RCS of the aircraft that fly straightly and level stably is approximately the same as static RCS. The fluctuant characteristic of dynamic RCS of the aircraft in the state of maneuvering flight is remarkable and stochastic. As the measurement time is long enough, the statistical characteristic of dynamic RCS of the aircraft in the state of maneuvering flight is more close to exponential distribution.
2017,
29: 123203.
doi: 10.11884/HPLPB201729.170196
Abstract:
A thin film model is embedded into the finite difference time domain (FDTD) method to solve the multi-scale problem effectively in the existence of thin carbon fiber composite (CFC) panels in the computational electromagnetics. In this model, the thin film works as a section of transmission line and can be replaced by its admittance matrix in the frequency domain. The digital filter theory and inverse Z transform are used to transform the frequency domain admittance matrix into its time domain form, which could be incorporated into the FDTD method. The embedded model has the advantages of saving computational resources due to the fact that it does not discretize the thin film and relatively large mesh size can be used in the surroundings. In this paper, the embedded model is used to analyze the reflection and transmission performance of a single-layered CFC panel. The results are compared with those from analytical solutions, which validates its accuracy, convergence and effectiveness. In the end, the embedded model is applied to analyze the effects of the electrical parameters of the CFC panel on its shielding performance.
A thin film model is embedded into the finite difference time domain (FDTD) method to solve the multi-scale problem effectively in the existence of thin carbon fiber composite (CFC) panels in the computational electromagnetics. In this model, the thin film works as a section of transmission line and can be replaced by its admittance matrix in the frequency domain. The digital filter theory and inverse Z transform are used to transform the frequency domain admittance matrix into its time domain form, which could be incorporated into the FDTD method. The embedded model has the advantages of saving computational resources due to the fact that it does not discretize the thin film and relatively large mesh size can be used in the surroundings. In this paper, the embedded model is used to analyze the reflection and transmission performance of a single-layered CFC panel. The results are compared with those from analytical solutions, which validates its accuracy, convergence and effectiveness. In the end, the embedded model is applied to analyze the effects of the electrical parameters of the CFC panel on its shielding performance.
2017,
29: 125001.
doi: 10.11884/HPLPB201729.170100
Abstract:
In this paper, a new self-integral Rogowski coil with magnetic core is designed, which has the advantages of high signal-to-noise ratio and wide dynamic range, for the measurement of nanosecond pulse current signal. It has shielding box open air gaps to prevent the eddy current. The outer layer of the shielding box is packaged with polyurethane encapsulation, and the polyurethane layer has a thickness greater than 1.5 mm, which can withstand more than 20 kV pulse voltage. The Rogowski coil is calibrated using a high-voltage square wave generator and a Pearson 4100 coil. The parameters of the Rogowski coil are: sensitivity 0.018 8 V/A, maximum rise time less than 20 ns, square wave pulse width 300 ns, maximum peak current 300 A.
In this paper, a new self-integral Rogowski coil with magnetic core is designed, which has the advantages of high signal-to-noise ratio and wide dynamic range, for the measurement of nanosecond pulse current signal. It has shielding box open air gaps to prevent the eddy current. The outer layer of the shielding box is packaged with polyurethane encapsulation, and the polyurethane layer has a thickness greater than 1.5 mm, which can withstand more than 20 kV pulse voltage. The Rogowski coil is calibrated using a high-voltage square wave generator and a Pearson 4100 coil. The parameters of the Rogowski coil are: sensitivity 0.018 8 V/A, maximum rise time less than 20 ns, square wave pulse width 300 ns, maximum peak current 300 A.
2017,
29: 125002.
doi: 10.11884/HPLPB201729.170402
Abstract:
In the design of pulsed circuit, the configuration of the output pulse waveform and the corresponding structure of the circuit need to be chosen according to the requirements of its application. The design methods of the circuit usually applied in engineering-such as the time-domain waveform superposition and the comparison by parameter-scanning-have a lot of disadvantages in practice, such as making it difficult for the designer to understand the essences of the configuration of the output pulse waveform. In this paper, the design methods of the pulse waveform both in time-domain and frequency-domain are summarized, and the calculation methods of the parameters of the components based on the analysis of the essential characters of the waveform of the circuit output pulse are introduced. The design methods based on the analysis of the frequency domain could help the researcher estimate the parameters of the components by analytic calculation and promote the innovation of circuit design.
In the design of pulsed circuit, the configuration of the output pulse waveform and the corresponding structure of the circuit need to be chosen according to the requirements of its application. The design methods of the circuit usually applied in engineering-such as the time-domain waveform superposition and the comparison by parameter-scanning-have a lot of disadvantages in practice, such as making it difficult for the designer to understand the essences of the configuration of the output pulse waveform. In this paper, the design methods of the pulse waveform both in time-domain and frequency-domain are summarized, and the calculation methods of the parameters of the components based on the analysis of the essential characters of the waveform of the circuit output pulse are introduced. The design methods based on the analysis of the frequency domain could help the researcher estimate the parameters of the components by analytic calculation and promote the innovation of circuit design.
2017,
29: 125101.
doi: 10.11884/HPLPB201729.170123
Abstract:
Beam position as a key parameter of intense electron beam linear induction accelerator，is criterion of electron beam tuning and experiment. The resistive ring monitor(RRM) and B-dot monitor are often used to measure the beam current and position simultaneously. According to the measuring principle, the calibration method and characters of monitor, type A and type B standard uncertainties and least square fit uncertainty were analyzed as the uncertainty sources of beam position monitors RRM and B-dot, and their evaluation were decided. The combined standard uncertainty of Dragon- resistive ring monitor and B-dot is less than 0.1mm based on calibrating data.
Beam position as a key parameter of intense electron beam linear induction accelerator，is criterion of electron beam tuning and experiment. The resistive ring monitor(RRM) and B-dot monitor are often used to measure the beam current and position simultaneously. According to the measuring principle, the calibration method and characters of monitor, type A and type B standard uncertainties and least square fit uncertainty were analyzed as the uncertainty sources of beam position monitors RRM and B-dot, and their evaluation were decided. The combined standard uncertainty of Dragon- resistive ring monitor and B-dot is less than 0.1mm based on calibrating data.
2017,
29: 126001.
doi: 10.11884/HPLPB201729.170240
Abstract:
Efficiency calibration of high purity germanium detector is accurately completed, which is related with accuracy of quantitative analysis for radioactive isotope. The physical model of a well-type high purity germanium detector is constructed by Monte Carlo software MCNP and efficiencies of this detector are determined by sourceless efficiency calibration. For samples with densities of 0.4 gcm-3 and 1.2 gcm-3, efficiencies of gamma rays are simulated by MCNP. When gamma rays energy is larger than 0.10MeV, detection efficiency is mainly related with samples density and gamma ray energy. For samples of soil (density from 0.1 gcm-3 to 1.6 gcm-3 ), aqueous solution (density is 1.0 gcm-3) and oil solution (density is 0.92 gcm-3), combined with the function models, the functions and parameters are determined. Combined with four standard sources, simulations of efficiency are verified, whose efficiencies are in agreement with the experimental values and errors of them are all lower than 3%. It is proved that MCNP code can be used to calculate efficiency of gamma ray for well-type high-purity germanium detector.
Efficiency calibration of high purity germanium detector is accurately completed, which is related with accuracy of quantitative analysis for radioactive isotope. The physical model of a well-type high purity germanium detector is constructed by Monte Carlo software MCNP and efficiencies of this detector are determined by sourceless efficiency calibration. For samples with densities of 0.4 gcm-3 and 1.2 gcm-3, efficiencies of gamma rays are simulated by MCNP. When gamma rays energy is larger than 0.10MeV, detection efficiency is mainly related with samples density and gamma ray energy. For samples of soil (density from 0.1 gcm-3 to 1.6 gcm-3 ), aqueous solution (density is 1.0 gcm-3) and oil solution (density is 0.92 gcm-3), combined with the function models, the functions and parameters are determined. Combined with four standard sources, simulations of efficiency are verified, whose efficiencies are in agreement with the experimental values and errors of them are all lower than 3%. It is proved that MCNP code can be used to calculate efficiency of gamma ray for well-type high-purity germanium detector.
2017,
29: 126002.
doi: 10.11884/HPLPB201729.170247
Abstract:
A system for measuring neutron total cross section, the Photo-Neutron Source (PNS, phase 1), has been developed for the acquisition of nuclear data from the Thorium Molten Salt Reactor(TMSR) at the Shanghai Institute of Applied Physics (SINAP). It is also used in the study of neutron detector and the irradiation material about reactor. The neutron total cross-sections of beryllium were measured in the neutron energy region from 0.007 to 0.100 eV. The present measurement result was compared with the existed experimental and the evaluated data of ENDF/VII.1. The correlated uncertainties were determined by using Geant4 Monte Carlo simulation method. In order to reduce the calculation time, the local weighted method was used in the simulation. The neutron time of flight spectrum and the neutron yield at the detector position in experiment and simulation were compared.
A system for measuring neutron total cross section, the Photo-Neutron Source (PNS, phase 1), has been developed for the acquisition of nuclear data from the Thorium Molten Salt Reactor(TMSR) at the Shanghai Institute of Applied Physics (SINAP). It is also used in the study of neutron detector and the irradiation material about reactor. The neutron total cross-sections of beryllium were measured in the neutron energy region from 0.007 to 0.100 eV. The present measurement result was compared with the existed experimental and the evaluated data of ENDF/VII.1. The correlated uncertainties were determined by using Geant4 Monte Carlo simulation method. In order to reduce the calculation time, the local weighted method was used in the simulation. The neutron time of flight spectrum and the neutron yield at the detector position in experiment and simulation were compared.
2017,
29: 126003.
doi: 10.11884/HPLPB201729.170229
Abstract:
In the design of the radiography system, designers often need to calculate the system performance indexes. In order to improve the product development efficiency, Nuctech Company Limited and Tsinghua University have jointly developed a professional radiography simulation software NucRPD based on Geant4 for the first time in China. NucRPD has established the parameterized models for the often used radiography systems, so that users can simply modify a few parameters from the user interface to quickly build a virtual radiography system, including the geometry, the particle source, the physical processes and the statistical quantities. Then NucRPD can carry out the parallel calculations in the computing cluster to give the simulation results in a short period. NucRPD can also show the results in an intuitive and elegant way to help users to deeply understand the simulation results. We have compared the simulation results of NucRPD with a large set of experiments, and simulation results of the imaging performance and radiation protection performance agree well with those of experiments. NucRPD has been successfully applied to the designs of the radiography products in Nuctech Company Limited, and it has played an increasingly important role in optimizing the imaging performance and radiation protection performance.
In the design of the radiography system, designers often need to calculate the system performance indexes. In order to improve the product development efficiency, Nuctech Company Limited and Tsinghua University have jointly developed a professional radiography simulation software NucRPD based on Geant4 for the first time in China. NucRPD has established the parameterized models for the often used radiography systems, so that users can simply modify a few parameters from the user interface to quickly build a virtual radiography system, including the geometry, the particle source, the physical processes and the statistical quantities. Then NucRPD can carry out the parallel calculations in the computing cluster to give the simulation results in a short period. NucRPD can also show the results in an intuitive and elegant way to help users to deeply understand the simulation results. We have compared the simulation results of NucRPD with a large set of experiments, and simulation results of the imaging performance and radiation protection performance agree well with those of experiments. NucRPD has been successfully applied to the designs of the radiography products in Nuctech Company Limited, and it has played an increasingly important role in optimizing the imaging performance and radiation protection performance.
2017,
29: 126004.
doi: 10.11884/HPLPB201729.170238
Abstract:
The structure of thermal column of the 250 kW TRIGA Mark II reactor, installed at the University of Pavia, was modified to perform BNCT on the explanted liver of patients affected by multiple metastases, which is not suitable for Single Emission Computed Tomography (SPECT) in BNCT. The purpose of this work is to optimize the thermal column of the reactor particularly for SPECT imaging experiment for BNCT. To reduce the computational cost, surface source writing (SSW) capability, which scores the particle information at certain position and can be further used repeatedly, was employed at the thermal column in MCNP6. The neutron energy distribution of the irradiation position in thermal column was investigated with standard method and the SSW approach to validate the feasibility of the SSW approach. To perform the SPECT experiment for BNCT, the thermal column of the reactor was modified to collimate the neutron source to a pencil beam. Here, three materials with four configurations were compared through thermal neutron fluxes and gamma fluxes on beam port and at detector position, which included 40 cm length graphite (5 cm3 cm for beam port), 40 cm length graphite covered by 0.5 cm thickness boral (5 cm3 cm for beam port), 30 cm length natural lithium polyethylene (4 cm in diameter for beam port), and 30 cm length natural lithium polyethylene (5 cm diameter in 20 cm length + 4 cm diameter in 5 cm length + 2 cm diameter in 5 cm length). The results show that the neutron energy distribution obtained using SSW source were comparable with that produced by the original source, which proves the validity and reliability of the SSW approach. With the above four configurations as the beam collimator, the thermal neutron fluxes on beam port were 1.05108#/(cm2s), 2.52107 #/(cm2s), 6.08107 #/(cm2s), and 5.10107 #/(cm2s) respectively. Although the configuration with graphite had a relatively higher neutron source on beam port, however, the neutron flux outside the beam port didnt reduce, representing a higher background for detector. Therefore, lithium polyethylene with a 4 cm diameter has the best performance in terms of the collimation of neutron source and gamma contamination. In conclusion, the SSW approach in MNCP6 showed good performance to reduce the computational resource with good agreement for BNCT-SPECT study. The configuration with 4 cm diameter and 30 cm length lithium polyethylene was selected as the collimator for neutron source.
The structure of thermal column of the 250 kW TRIGA Mark II reactor, installed at the University of Pavia, was modified to perform BNCT on the explanted liver of patients affected by multiple metastases, which is not suitable for Single Emission Computed Tomography (SPECT) in BNCT. The purpose of this work is to optimize the thermal column of the reactor particularly for SPECT imaging experiment for BNCT. To reduce the computational cost, surface source writing (SSW) capability, which scores the particle information at certain position and can be further used repeatedly, was employed at the thermal column in MCNP6. The neutron energy distribution of the irradiation position in thermal column was investigated with standard method and the SSW approach to validate the feasibility of the SSW approach. To perform the SPECT experiment for BNCT, the thermal column of the reactor was modified to collimate the neutron source to a pencil beam. Here, three materials with four configurations were compared through thermal neutron fluxes and gamma fluxes on beam port and at detector position, which included 40 cm length graphite (5 cm3 cm for beam port), 40 cm length graphite covered by 0.5 cm thickness boral (5 cm3 cm for beam port), 30 cm length natural lithium polyethylene (4 cm in diameter for beam port), and 30 cm length natural lithium polyethylene (5 cm diameter in 20 cm length + 4 cm diameter in 5 cm length + 2 cm diameter in 5 cm length). The results show that the neutron energy distribution obtained using SSW source were comparable with that produced by the original source, which proves the validity and reliability of the SSW approach. With the above four configurations as the beam collimator, the thermal neutron fluxes on beam port were 1.05108#/(cm2s), 2.52107 #/(cm2s), 6.08107 #/(cm2s), and 5.10107 #/(cm2s) respectively. Although the configuration with graphite had a relatively higher neutron source on beam port, however, the neutron flux outside the beam port didnt reduce, representing a higher background for detector. Therefore, lithium polyethylene with a 4 cm diameter has the best performance in terms of the collimation of neutron source and gamma contamination. In conclusion, the SSW approach in MNCP6 showed good performance to reduce the computational resource with good agreement for BNCT-SPECT study. The configuration with 4 cm diameter and 30 cm length lithium polyethylene was selected as the collimator for neutron source.
2017,
29: 126005.
doi: 10.11884/HPLPB201729.170235
Abstract:
The whole body counter is used to monitor the contamination of the human body and has a high requirement for the minimum detection limit (MDA). In order to have a better sensitivity for the whole body counter, it is necessary to reduce the background radiation and improve the radiation detection efficiency. Based on MCNP5, the energy response of the NaI detector in the geometric position is simulated. The position of the detector and the angle of the collimator are studied. At the same time, the shielded structure with different thickness is simulated and analyzed. The study shows that when the thickness of the shielded steel plate is 14.9 cm, the background radiation can be reduced to a large extent. In the source structure to detect the cavity collimator angle above 26, when the distance between the detector and the body mold is 20 cm, the detector can get the ideal energy spectrum response and detection efficiency.
The whole body counter is used to monitor the contamination of the human body and has a high requirement for the minimum detection limit (MDA). In order to have a better sensitivity for the whole body counter, it is necessary to reduce the background radiation and improve the radiation detection efficiency. Based on MCNP5, the energy response of the NaI detector in the geometric position is simulated. The position of the detector and the angle of the collimator are studied. At the same time, the shielded structure with different thickness is simulated and analyzed. The study shows that when the thickness of the shielded steel plate is 14.9 cm, the background radiation can be reduced to a large extent. In the source structure to detect the cavity collimator angle above 26, when the distance between the detector and the body mold is 20 cm, the detector can get the ideal energy spectrum response and detection efficiency.
2017,
29: 126006.
doi: 10.11884/HPLPB201729.170231
Abstract:
Large amounts of low and intermediate level radioactive waste (LILW) will be produced and piled up with the nuclear power industry development and the increasing widespread application of radioisotopes. The types of nuclides and the activity of the radioactive waste should be measured before the radioactive waste is disposed. Segmented gamma scanning (SGS) measure is an important technique of quantitative analysis for nuclear scrap and radioactive waste. However, when point source location changes, both the relative attenuation distance and scale efficiency are not corresponding, which causes errors of counts of detectors on activity estimation. This study is based on 12 different positions counts method and through Monte Carlo simulation methods, records waste barrels with uniform filling of polyethylene samples. It will find the max min counts records with Beer-Lambert attenuation law to value the turning radius, so that it can determine the location of radioactive nuclides in the current segment. Thus, the problem of the attenuation distance, scale efficiency non-correspondence of the radionuclide in different location which lead to SGS estimate error of point source activity is solved.
Large amounts of low and intermediate level radioactive waste (LILW) will be produced and piled up with the nuclear power industry development and the increasing widespread application of radioisotopes. The types of nuclides and the activity of the radioactive waste should be measured before the radioactive waste is disposed. Segmented gamma scanning (SGS) measure is an important technique of quantitative analysis for nuclear scrap and radioactive waste. However, when point source location changes, both the relative attenuation distance and scale efficiency are not corresponding, which causes errors of counts of detectors on activity estimation. This study is based on 12 different positions counts method and through Monte Carlo simulation methods, records waste barrels with uniform filling of polyethylene samples. It will find the max min counts records with Beer-Lambert attenuation law to value the turning radius, so that it can determine the location of radioactive nuclides in the current segment. Thus, the problem of the attenuation distance, scale efficiency non-correspondence of the radionuclide in different location which lead to SGS estimate error of point source activity is solved.
2017,
29: 126007.
doi: 10.11884/HPLPB201729.170253
Abstract:
In order to meet the requirements of photon-electron simulations in the practical applications, the photon-electron coupled transport function is researched and developed in JMCT. This function is realized in several different ways so as to satisfy a variety of engineering requirements. Typical photon-electron coupled transport examples are simulated, which verifies the correctness of JMCT photon-electron coupled function. In addition, this function is applied to simulate the detector response functions and flash radiography. It is shown that JMCT will play a more and more important role in the field of experimental nuclear physics and nuclear analysis technology.
In order to meet the requirements of photon-electron simulations in the practical applications, the photon-electron coupled transport function is researched and developed in JMCT. This function is realized in several different ways so as to satisfy a variety of engineering requirements. Typical photon-electron coupled transport examples are simulated, which verifies the correctness of JMCT photon-electron coupled function. In addition, this function is applied to simulate the detector response functions and flash radiography. It is shown that JMCT will play a more and more important role in the field of experimental nuclear physics and nuclear analysis technology.
2017,
29: 126008.
doi: 10.11884/HPLPB201729.170225
Abstract:
In order to obtain a small angle monoenergetic neutron source, the Monte Carlo software is used to design the shield collimating structure of the small 4 neutron source with energy of 2.45 MeV produced by a D-D neutron tube. The shield collimating structure is divided into a collimator and a capture cave. The collimator is made of three layers of iron, boron containing polyethylene and lead, which is used to shield the stray neutrons from the irradiation outside. The main function of the capture cave is to increase the number of elastic scattering in the opposite direction, thus reducing the proportion of the low energy scattered neutrons. The optimum thickness of the material and the size of the aperture and the optimum structure of the capture cave are obtained by MCNP simulation. Finally it is proved that the neutron flux of neutrons with 2.45 MeV energy in the radiation field is three orders of magnitude higher than that outside the radiation field. The low energy neutron flux in the radiation field is one order lower than the 2.45 MeV neutron flux, the total dose rate of both neutron and gamma outside the walls is below 2.5 Gy/h. This research has practical value for small angle neutron source with single energy, and it has important significance for the study of the verification of validity of neutron dosimeter and performance test of neutron monitor.
In order to obtain a small angle monoenergetic neutron source, the Monte Carlo software is used to design the shield collimating structure of the small 4 neutron source with energy of 2.45 MeV produced by a D-D neutron tube. The shield collimating structure is divided into a collimator and a capture cave. The collimator is made of three layers of iron, boron containing polyethylene and lead, which is used to shield the stray neutrons from the irradiation outside. The main function of the capture cave is to increase the number of elastic scattering in the opposite direction, thus reducing the proportion of the low energy scattered neutrons. The optimum thickness of the material and the size of the aperture and the optimum structure of the capture cave are obtained by MCNP simulation. Finally it is proved that the neutron flux of neutrons with 2.45 MeV energy in the radiation field is three orders of magnitude higher than that outside the radiation field. The low energy neutron flux in the radiation field is one order lower than the 2.45 MeV neutron flux, the total dose rate of both neutron and gamma outside the walls is below 2.5 Gy/h. This research has practical value for small angle neutron source with single energy, and it has important significance for the study of the verification of validity of neutron dosimeter and performance test of neutron monitor.
2017,
29: 126009.
doi: 10.11884/HPLPB201729.170268
Abstract:
In this paper, the density distribution of stochastic diffusion equation (SDE) is calculated by the kernel function method, and the statistical fluctuation is reduced by the kernel function. As the density of SDE over time is sparser and sparser, the kernel function is bigger and bigger, i.e., the kernel function is changing over time, and the rule is given by a method called the variable bandwidth kernel function method. Through an instantaneous release of a two-dimensional diffusion problem (with the analytical solution), from the perspective of both qualitative and quantitative comparisons of the variable bandwidth kernel function method and the traditional statistical method in the performance of density distribution statistical difference, this paper discusses the advantages and disadvantages of variable bandwidth kernel function method. The variable bandwidth kernel function method which sacrifices part of the peak can be very good to solve the problem of SDE density distribution statistical fluctuation, and it is worth promoting in engineering applications.
In this paper, the density distribution of stochastic diffusion equation (SDE) is calculated by the kernel function method, and the statistical fluctuation is reduced by the kernel function. As the density of SDE over time is sparser and sparser, the kernel function is bigger and bigger, i.e., the kernel function is changing over time, and the rule is given by a method called the variable bandwidth kernel function method. Through an instantaneous release of a two-dimensional diffusion problem (with the analytical solution), from the perspective of both qualitative and quantitative comparisons of the variable bandwidth kernel function method and the traditional statistical method in the performance of density distribution statistical difference, this paper discusses the advantages and disadvantages of variable bandwidth kernel function method. The variable bandwidth kernel function method which sacrifices part of the peak can be very good to solve the problem of SDE density distribution statistical fluctuation, and it is worth promoting in engineering applications.
2017,
29: 126010.
doi: 10.11884/HPLPB201729.170241
Abstract:
In order to study the influencing factors of detector efficiency and limitation of the liquid gamma monitor XH-3130A on the measurement of radioactive pipe of some nuclear plants, the detector efficiency of peak region and full spectrum region of gamma ray in the range of 0.08-1.5 MeV by XH-3130A is calculated with MCNP5. As for the measurement of Cs-137 gamma source, the calculated results are in line with the experimental data. Meanwhile the paper analyses effects of different sources of gamma ray energy and probe arrangement on the detection efficiency of activity concentration. The simulation results show that the limit of the modified monitor XH-3130A is 1.35103 Bq/cm3 and meets the engineering requirements.
In order to study the influencing factors of detector efficiency and limitation of the liquid gamma monitor XH-3130A on the measurement of radioactive pipe of some nuclear plants, the detector efficiency of peak region and full spectrum region of gamma ray in the range of 0.08-1.5 MeV by XH-3130A is calculated with MCNP5. As for the measurement of Cs-137 gamma source, the calculated results are in line with the experimental data. Meanwhile the paper analyses effects of different sources of gamma ray energy and probe arrangement on the detection efficiency of activity concentration. The simulation results show that the limit of the modified monitor XH-3130A is 1.35103 Bq/cm3 and meets the engineering requirements.
2017,
29: 126011.
doi: 10.11884/HPLPB201729.170236
Abstract:
This paper aims to determine the relationship between the emission of Cerenkov photon number and radiation dose from internal radionuclide and proposes, a potential dosimetry based on Cerenkov radiation for radionuclide therapy. Water and thyroid phantoms were used to simulate the distribution of Cerenkov photon number and dose deposition produced by radionuclide 131I through Geant4 toolkit, and the relationship between Cerenkov photon number and dose deposition was quantitatively analyzed. The calculation results show that the Cerenkov photon number and dose deposition have the same distribution trend in water phantom, and this relative distribution relationship also exists in thyroid phantom. Moreover, the Cerenkov photon number exhibits a specific quantitative relation to dose deposition.
This paper aims to determine the relationship between the emission of Cerenkov photon number and radiation dose from internal radionuclide and proposes, a potential dosimetry based on Cerenkov radiation for radionuclide therapy. Water and thyroid phantoms were used to simulate the distribution of Cerenkov photon number and dose deposition produced by radionuclide 131I through Geant4 toolkit, and the relationship between Cerenkov photon number and dose deposition was quantitatively analyzed. The calculation results show that the Cerenkov photon number and dose deposition have the same distribution trend in water phantom, and this relative distribution relationship also exists in thyroid phantom. Moreover, the Cerenkov photon number exhibits a specific quantitative relation to dose deposition.
2017,
29: 126012.
doi: 10.11884/HPLPB201729.170233
Abstract:
Based on random censoring data whose life follows exponential distribution, unit and system reliability evaluation methods are studied, and a method of estimating the reliability lower limit is proposed in the case of the exponential distribution under random censoring data, which is also applicable to type Ⅰ censoring data and type Ⅱ censoring data. Firstly, the censoring data are complemented into virtual complete data by use of the quantile-filling algorithm. Based on the fiducial inference, the failure rate distribution of each unit is given. According to the characteristics of the exponential distribution, in view of the failure rate, unit failure rate samples are randomly extracted by Monte Carlo method. In addition to system reliability model, the distribution of system failure rate is obtained, therefore the upper limit of the system failure rate at the given confidence level, and the lower confidence limit of the system reliability are obtained.
Based on random censoring data whose life follows exponential distribution, unit and system reliability evaluation methods are studied, and a method of estimating the reliability lower limit is proposed in the case of the exponential distribution under random censoring data, which is also applicable to type Ⅰ censoring data and type Ⅱ censoring data. Firstly, the censoring data are complemented into virtual complete data by use of the quantile-filling algorithm. Based on the fiducial inference, the failure rate distribution of each unit is given. According to the characteristics of the exponential distribution, in view of the failure rate, unit failure rate samples are randomly extracted by Monte Carlo method. In addition to system reliability model, the distribution of system failure rate is obtained, therefore the upper limit of the system failure rate at the given confidence level, and the lower confidence limit of the system reliability are obtained.
2017,
29: 126013.
doi: 10.11884/HPLPB201729.170237
Abstract:
Given the aerospace equipment failure and radiation damage of astronauts caused by spatial high-energy electron, a metal/vacuum sandwich configuration was proposed based on electron return effects induced by magnetic field. The continuous energy spectrum of spatial high-energy electron was simulated and shielding ability of sandwich configuration in magnetic field was investigated by using the Monte Carlo method. Moreover, the influences of magnetic flux density and layer of metal on the shielding property of sandwich systems were investigated by using a female Chinese hybrid reference phantom based on cumulative dose. Results show that the sandwich systems presented have improved shielding ability to electrons and less secondary X-ray transmissions than the conventional systems. The cumulative dose decreased and shielding ability increased with increasing magnetic flux intensity. The Ti/Ti sandwich configuration exhibited superior high-energy shielding performance. Due to its effective high-energy electron shielding ability, this type of shielding system might be used for further space radiation protection in a high-energy electron environment.
Given the aerospace equipment failure and radiation damage of astronauts caused by spatial high-energy electron, a metal/vacuum sandwich configuration was proposed based on electron return effects induced by magnetic field. The continuous energy spectrum of spatial high-energy electron was simulated and shielding ability of sandwich configuration in magnetic field was investigated by using the Monte Carlo method. Moreover, the influences of magnetic flux density and layer of metal on the shielding property of sandwich systems were investigated by using a female Chinese hybrid reference phantom based on cumulative dose. Results show that the sandwich systems presented have improved shielding ability to electrons and less secondary X-ray transmissions than the conventional systems. The cumulative dose decreased and shielding ability increased with increasing magnetic flux intensity. The Ti/Ti sandwich configuration exhibited superior high-energy shielding performance. Due to its effective high-energy electron shielding ability, this type of shielding system might be used for further space radiation protection in a high-energy electron environment.
2017,
29: 126014.
doi: 10.11884/HPLPB201729.170232
Abstract:
(n,2n) cross section can be measured through the direct measurement method with a 4 spherical 3He neutron detector. The neutron beam must be collimated in such experiments. A satisfactory design of the collimator is required to: (1) improve the uniformity of neutron flux at sample position and guarantee enough decreasing amplitude of the border of neutron beam at the same time; (2) reduce the scattered neutron background at low energy region. In this work, using FLUKA and MCNPX codes, the comparison between cylindrical collimator, conical collimator, and three double-truncated conical collimators with different slope on the uniformity of neutron flux and the proportion of low energy neutron was studied. The result shows that the double-truncated conical collimator with low slope can satisfy the experiment requirement. At the same time, the response of the detection system was compared after neutrons collimated by five collimators respectively with and without sample. The result shows that when neutrons are collimated by the double-truncated conical collimator with low slope, the detection system has the higher count rate with sample, and the lower background without sample. In addition, the collimation efficiency affected by the slope of collimator outlet was also compared. The double-truncated conical collimator with low slope was finally chosen as the neutron collimator and the materials of the collimator are red copper, stainless steel, polyethylene and lead. The diameter at the beginning of the collimator aperture is 2.64 cm and its length is 137 cm. The beam diameter after collimation at the sample position is 3.2 cm.
(n,2n) cross section can be measured through the direct measurement method with a 4 spherical 3He neutron detector. The neutron beam must be collimated in such experiments. A satisfactory design of the collimator is required to: (1) improve the uniformity of neutron flux at sample position and guarantee enough decreasing amplitude of the border of neutron beam at the same time; (2) reduce the scattered neutron background at low energy region. In this work, using FLUKA and MCNPX codes, the comparison between cylindrical collimator, conical collimator, and three double-truncated conical collimators with different slope on the uniformity of neutron flux and the proportion of low energy neutron was studied. The result shows that the double-truncated conical collimator with low slope can satisfy the experiment requirement. At the same time, the response of the detection system was compared after neutrons collimated by five collimators respectively with and without sample. The result shows that when neutrons are collimated by the double-truncated conical collimator with low slope, the detection system has the higher count rate with sample, and the lower background without sample. In addition, the collimation efficiency affected by the slope of collimator outlet was also compared. The double-truncated conical collimator with low slope was finally chosen as the neutron collimator and the materials of the collimator are red copper, stainless steel, polyethylene and lead. The diameter at the beginning of the collimator aperture is 2.64 cm and its length is 137 cm. The beam diameter after collimation at the sample position is 3.2 cm.
2017,
29: 126015.
doi: 10.11884/HPLPB201729.170220
Abstract:
This study proposes a novel magnetic-modulated proton therapy, explores tumor and organ doses as functions of the magnetic modulation method, and investigates the application of the magnetic-modulated therapy in curing organ-surrounded tumors. Based on Geant4 Monte Carlo code, we constructed an ideal organ-surrounded structure and an abdominal structure comprising a pancreatic tumor. Bragg peak positions of proton beams were modulated through altering the strengths and directions of the magnetic fields inside the two geometric structures. Following the magnetic-deflected transportation tracks, the proton beams were modulated to bypass the vital organs and irradiate the tumor. For the ideal organ-surrounding configuration, the tumor can be sufficiently covered by 95% relative doses, and the vital organ volume receiving proton irradiations can be controlled to nearly zero. For the abdominal structure comprising the pancreatic tumor, the proton beams modulated by magnetic fields can bypass the spinal cord and left kidney and irradiate the pancreatic tumor. Sufficient coverage of 95% relative doses can be achieved through the magnetic-modulated proton therapy method.
This study proposes a novel magnetic-modulated proton therapy, explores tumor and organ doses as functions of the magnetic modulation method, and investigates the application of the magnetic-modulated therapy in curing organ-surrounded tumors. Based on Geant4 Monte Carlo code, we constructed an ideal organ-surrounded structure and an abdominal structure comprising a pancreatic tumor. Bragg peak positions of proton beams were modulated through altering the strengths and directions of the magnetic fields inside the two geometric structures. Following the magnetic-deflected transportation tracks, the proton beams were modulated to bypass the vital organs and irradiate the tumor. For the ideal organ-surrounding configuration, the tumor can be sufficiently covered by 95% relative doses, and the vital organ volume receiving proton irradiations can be controlled to nearly zero. For the abdominal structure comprising the pancreatic tumor, the proton beams modulated by magnetic fields can bypass the spinal cord and left kidney and irradiate the pancreatic tumor. Sufficient coverage of 95% relative doses can be achieved through the magnetic-modulated proton therapy method.
2017,
29: 126016.
doi: 10.11884/HPLPB201729.170221
Abstract:
The VERA core physics benchmark progression problems proposed by Consortium for Advanced Simulation of LWRs (CASL) provide a method to demonstrate the computational capabilities for reactor physics methods and software. The benchmark is based on actual fuel from the initial core loading of Watts Bar Nuclear unit 1, and consists of 10 problems ranging from a simple 2D pin problem cell to the full cycle depletion and refueling of problem a 3D reactor core configuration. In this paper, the cosRMC code is applied to perform criticality calculation of the VERA benchmark problems and the eigenvalue, assembly power distribution, differential and integral control rod worth and reactivity coefficient are obtained. By comparing the cosRMC data with the referential KENO results, it is found that the two Monte Carlo codes agree with each other well. It indicates that the cosRMC code has the capability of 2D lattice and 3D core modeling with fairly good precision as KENO.
The VERA core physics benchmark progression problems proposed by Consortium for Advanced Simulation of LWRs (CASL) provide a method to demonstrate the computational capabilities for reactor physics methods and software. The benchmark is based on actual fuel from the initial core loading of Watts Bar Nuclear unit 1, and consists of 10 problems ranging from a simple 2D pin problem cell to the full cycle depletion and refueling of problem a 3D reactor core configuration. In this paper, the cosRMC code is applied to perform criticality calculation of the VERA benchmark problems and the eigenvalue, assembly power distribution, differential and integral control rod worth and reactivity coefficient are obtained. By comparing the cosRMC data with the referential KENO results, it is found that the two Monte Carlo codes agree with each other well. It indicates that the cosRMC code has the capability of 2D lattice and 3D core modeling with fairly good precision as KENO.
2017,
29: 126017.
doi: 10.11884/HPLPB201729.170227
Abstract:
Using gold nanoparticles (GNPs) as a radiation sensitizer in radiotherapy is an international research focus.The self-developed nanodosimetry biophysics Monte Carlo code NASIC was used to study both the physical and biological radiosensitization effects of GNPs in the cell environment under the irradiation of photons. GNP-cell models were built in the simulation with single GNP in the nucleus center or four different ideal distributions of multiple GNPs. The influence of photon energy, GNP size and distribution on the energy deposition, DSB number and cell survival fraction were studied. The results show that the enhancement effect of energy deposition occurs in the vicinity (~2 m) of GNP, which is mainly due to the increase of photon interactions in the GNP. The variation trends of the total energy deposition in the nucleus, DSB number and cell survival fraction with photon energy and GNP diameter are similar, but the enhancement factors decrease with the largest values as 1.55, 1.32 and 1.14 respectively. 40 keV photon energy, 100 nm GNP diameter and GNPs distributing on the nucleus surface have advantage over other parameter values in physical and biological radiosensitization effect.
Using gold nanoparticles (GNPs) as a radiation sensitizer in radiotherapy is an international research focus.The self-developed nanodosimetry biophysics Monte Carlo code NASIC was used to study both the physical and biological radiosensitization effects of GNPs in the cell environment under the irradiation of photons. GNP-cell models were built in the simulation with single GNP in the nucleus center or four different ideal distributions of multiple GNPs. The influence of photon energy, GNP size and distribution on the energy deposition, DSB number and cell survival fraction were studied. The results show that the enhancement effect of energy deposition occurs in the vicinity (~2 m) of GNP, which is mainly due to the increase of photon interactions in the GNP. The variation trends of the total energy deposition in the nucleus, DSB number and cell survival fraction with photon energy and GNP diameter are similar, but the enhancement factors decrease with the largest values as 1.55, 1.32 and 1.14 respectively. 40 keV photon energy, 100 nm GNP diameter and GNPs distributing on the nucleus surface have advantage over other parameter values in physical and biological radiosensitization effect.
2017,
29: 126018.
doi: 10.11884/HPLPB201729.170234
Abstract:
The fission matrix acceleration method can accelerate the convergence of source distribution in the Monte Carlo(MC) criticality calculation. The inner-outer iteration is introduced to analyze the effect of the mesh division on the fission matrix acceleration method. Its pointed out that the convergence rate increases with a refined mesh to tally the fission matrix but the refined mesh method has its limitation with the consideration of the stability of method. To solve this problem, the mesh changing method is proposed, which can improve the performance of the fission matrix acceleration method further without the increase of order of fission matrix. The improvement is verified by a 1D slab model.
The fission matrix acceleration method can accelerate the convergence of source distribution in the Monte Carlo(MC) criticality calculation. The inner-outer iteration is introduced to analyze the effect of the mesh division on the fission matrix acceleration method. Its pointed out that the convergence rate increases with a refined mesh to tally the fission matrix but the refined mesh method has its limitation with the consideration of the stability of method. To solve this problem, the mesh changing method is proposed, which can improve the performance of the fission matrix acceleration method further without the increase of order of fission matrix. The improvement is verified by a 1D slab model.
2017,
29: 122001.
doi: 10.11884/HPLPB201729.170178
Abstract:
Cryogenic target is one of the critical component in inertial confinement fusion, which is assembled inside a hohlraum needed to be filled by fill tubes. In this paper, a microchannel model is established based on the analysis of the big difference between the microchannel and the conventional channel on flow and heat transfer characteristics. The modeling is implemented with FLUENT software and the correction of Navier-Stokes equations is inserted through UDF. From the results of simulation, the effect of gravity can be neglected while that of surface tension should be taken into consideration. Velocity slip and temperature jump are also calculated for their significant influence on flow and heat transfer in the microchannel. Three different fill tube models are compared to provide a suitable type for experiment design. Choosing different boundary conditions, certain filling of fuel could be confirmed. During the filling process, the temperature and pressure of inlet should be increased gradually with the increasing temperature and pressure of outlet to guarantee continuous controlled filling.
Cryogenic target is one of the critical component in inertial confinement fusion, which is assembled inside a hohlraum needed to be filled by fill tubes. In this paper, a microchannel model is established based on the analysis of the big difference between the microchannel and the conventional channel on flow and heat transfer characteristics. The modeling is implemented with FLUENT software and the correction of Navier-Stokes equations is inserted through UDF. From the results of simulation, the effect of gravity can be neglected while that of surface tension should be taken into consideration. Velocity slip and temperature jump are also calculated for their significant influence on flow and heat transfer in the microchannel. Three different fill tube models are compared to provide a suitable type for experiment design. Choosing different boundary conditions, certain filling of fuel could be confirmed. During the filling process, the temperature and pressure of inlet should be increased gradually with the increasing temperature and pressure of outlet to guarantee continuous controlled filling.
2017,
29: 129001.
doi: 10.11884/HPLPB201729.170145
Abstract:
The thermal blockage effect caused by plasma (produced by mega-watt laser ablation of C/C composite target) absorption laser beam energy is studied in this paper. First, based on the inverse bremsstrahlung absorption theory, a propagation model of laser through plasma generated by ablating the target is built. Then, based on the theory of magnetic fluid, wave equations of plasma in the form of electromagnetic caused by mega-watt laser and thermal blockage effect model caused by the plasma absorption laser energy are introduced. Finally, numerical simulation gives the total density of particles in the ablation process, absorption coefficient, changes of target surface equivalent heat flux and whether thermal blockage effect is taken into account, the differences of the temperature field curve along the vertical direction of the target surface. The results show that because of the plasma formation, the thermal blockage effect is obvious to the laser. It weakens the burning effect of laser on the target, and makes the total particle density, the absorption coefficient, the equivalent heat flow on target surface and temperature field vertical to target surface all change nonlinearly.
The thermal blockage effect caused by plasma (produced by mega-watt laser ablation of C/C composite target) absorption laser beam energy is studied in this paper. First, based on the inverse bremsstrahlung absorption theory, a propagation model of laser through plasma generated by ablating the target is built. Then, based on the theory of magnetic fluid, wave equations of plasma in the form of electromagnetic caused by mega-watt laser and thermal blockage effect model caused by the plasma absorption laser energy are introduced. Finally, numerical simulation gives the total density of particles in the ablation process, absorption coefficient, changes of target surface equivalent heat flux and whether thermal blockage effect is taken into account, the differences of the temperature field curve along the vertical direction of the target surface. The results show that because of the plasma formation, the thermal blockage effect is obvious to the laser. It weakens the burning effect of laser on the target, and makes the total particle density, the absorption coefficient, the equivalent heat flow on target surface and temperature field vertical to target surface all change nonlinearly.
