Calculation of Plasma Radiation in Electrothermal-Chemical Launcher简

A numerical model of radiation has been adopted for electrothermM-chemical （ETC） launcher, in which Monte Carlo method and statistical physics are employed to simulate the process of a capillary plasma source in an ETC launcher. The effect on propellant grains with different average absorption coefficients is discussed. The plasma-propellant interaction is also discussed when combined with a thermal model. Results show that the strong instantaneous radiation is responsible for the transmission of energy to the propellant grains leading to ignition. The efficiency of energy absorption in the propellant bed always maintains a high level. Radiant energy caused by plasma is concentrated around the plaslna injector. And the ＂hot zone＂ efficiency is mainly affected by the properties of propellant grains within a small field around the plasma injector.     

Characterization of Nitrogen Glow Discharge Plasma via Optical Emission Spectrum Simulation

Optical emission spectroscopy in nitrogen glow discharge plasma is simulated, and the collision excitations and characteristic emissions of the species （N2, N2^＋, N^＋, N） are investigated by a Monte Carlo model for nitrogen molecular gas discharge. The excitation rates of the main excited states are calculated and the corresponding relation and relative magnitude between the distribution of excitation rate of a certain excited state and the distributions of the emission rates of various lines originating from this excited level are also explored. The simulated results are compared with the experimental measurements in two typical discharge conditions. The luminescence mechanism of the line N2^＋： 391.4 nm is explained based on the microscopic plasma processes. The cathode glow in N2 discharge is found to be mainly caused by N^＋ impact excitation and the intensity of cathode glow decreases with the voltage. The corresponding relation between the emission rate or intensity of the 391.4 nm line and the production rate and the density of N2^＋ is also examined.     

Kinetic Monte Carlo Simulation of Deposition of Co Thin Film on Cu（001）

A kinetic Monte Carlo （kMC） simulation is conducted to study the growth of ultrathin film of Co on Cu（001） surface. The many-body, tight-binding potential model is used in the simulation to represent the interatomic potential. The film morphology of heteroepitaxial Co film on a Cu（001） substrate at the transient and final state conditions with various incident energies is simulated. The Co covered area and the thickness of the film growth of the first two layers are investigated. The simulation results show that the incident energy influences the film growth and structure. There exists a transition energy where the interracial roughness is minimum. There are some void regions in the film in the final state, because of the influence of the island growth in the first few layers. In addition, there are deviations from ideal layer-by-layer growth at a coverage from 0 - 2 monolayers （ML）.     

Calculation of Electron Swarm Parameters of SF6/N2 in a Uniform Field Using an Improved Monte Carlo Collision Simulation Method

The electron swarm parameters of SF6/N2 are calculated in the present study using an improved Monte Carlo collision simulation method （MCS）. And some improved sampling techniques are also adopted. The simulation results show that the improved simulation method can provide more accurate results.     

Dosimetric Analyses of Single Particle Microbeam in Cell Irradiation Experiment

Single particle microbeam （SPM） is uniquely capable of delivering precisely the predefined number of charged particles to determined individual cells or sub-cellular targets in situ. It has been recognized as a powerful technique for unveiling ionization irradiation mechanisms of organism. This article describes some investigations on the irradiation quality of SPM of major world laboratories by means of Monte Carlo method based on dosimetry and microdosimetry. Those parameters are helpful not only to improve SPM irradiating cell experiments but also to study the biological effects of cells irradiated by SPM.     

Geant4 simulation of plastic scintillators for a prototype μSR spectrometer

The experimental muon source on China Spallation Neutron Source(CSNS) is expected to be a high intensity(105μ+/s) surface muon source with a small beam spot of 4-cm diameter.For a practical application of this muon source,we are devoting to develop the first pulsed μSR spectrometer in China.In this paper,the performance of plastic scintillators in the μSR spectrometer is studied by Monte Carlo simulation.The processes such as positron energy deposition,scintillation photons production,light propagation and photon-electron conversion are carefully considered.According to the results,an optimal dimension of the plastic scintillator is proposed using for our future spectrometer,which has a long-strip shape with the dimension variation range of 50–60 mm length,5–8 mm height,and 10–12 mm width.Finally,we can build a spectrometer with a count rate up to 104e+/s by 100–120 forward and backward segmental detectors in total.The simulation could serve as an important guide for spectrometer construction.     

点源γ光子穿越特定形状屏蔽层的Monte Carlo计算与模拟

采用Monte Carlo方法对点源γ光子穿越球壳形屏蔽层的问题进行了蒙特卡罗计算与模拟,并用VC 编写了软件对光子运行过程进行模拟,通过对模拟结果γ能谱的分析,显示模拟结果能较好地反映实际光子的运动过程。利用所编软件对不同材料不同厚度的介质进行模拟,可得出厚度为4cm的铅做介质对光子的屏蔽效果较好。     

Plasma Activation of Integrated Carbon Nanotube Electrodes for Electrochemical Detection of Catechol

In this study, integrated multi-wall carbon nanotube （MWCNT） electrodes were prepared in the holes of glass directly by microwave plasma chemical vapour deposition （MWPCVD）. The electrochemical behaviour of catechol at the integrated MWCNT electrodes was investigated. The oxygen plasma treated CNT electrodes had better electrochemical performance for the analysis of catechol than that of as-synthesized CNT electrodes. Both the as-synthesized CNTs and plasma treated CNTs were characterized by TEM（transmission electron microscopy, XPS（X-ray photoelectron spectroscopy） and Raman spectroscopy. The results revealed that the oxygen plasma activation is an effective method to enhance the electrochemical properties of CNT electrodes.     

基于蒙特卡罗抽样的活化中子能谱测量不确定度分析

不确定度分析是活化法测量中子能谱的关键环节。本文针对SAND-Ⅱ活化中子解谱过程,给出了一种基于先验谱、活化率和截面协方差的中子能谱测量不确定度蒙特卡罗分析方法。首先,建立了基于线性变换的截面协方差抽样方法;然后,利用MCNP计算了误差,使用迭代方法估计了先验谱不确定度;最后,结合活化率的测量不确定度,利用蒙特卡罗抽样算法计算了中子能谱的不确定度。利用锎源自发裂变谱对该方法进行了验证,与传统方法相比,不确定度分析结果更为准确。对西安脉冲堆某次中子能谱测量结果进行了测量不确定度分析,结果表明该方法更具保守性。     

Range distribution of fluorine in F-implanted LiNbO3

Depth profiles of fluorine in ¹⁹F⁺implanted LiNbO³ have been accurately measured using the ₁₉F(p, γ)¹⁶O resonant nuclear reaction at E_R = 872.1 keV, with Γ = 4.2 keV. A proper convolution calculation method was used to extract the true distribution of fluorine from the experimental excitation yield curves. The experimental range distribution parameters, R_p and ΔR_p, were compared with those obtained by Monte Carlo simulation using a computer code developed recently in this group and with results obtained using the TRIM90 code. It shows that the experimental R_p values agree with the Monte Carlo simulation values very well, while the experimental ΔR_p values are larger than those obtained from the simulations. The simulation with our computer code improves the agreement between the experimental and calculated range straggling, ΔR_p.     

A Monte Carlo Simulation of an Actual Segmented Calorimeter: A Study of Calorimeter Performance at High Energies

The computer code system CALOR has been used to simulate data taken with a large segmented liquid argon/iron calorimeter at Fermilab. The resulting energy and angular distributions along with the longitudinal and transverse shower shapes are compared to experimental data in the range 1-38 GeV. Results are presented extending the Monte Carlo simulations to 125 GeV. The energy resolution of an incident hadron can be determined with a resolution ?E/E = (7.6 + 29.2/?E)% and its direction with a resolution of ?(?) = 22.7 + 390/E) mrad (where E is in GeV).     

Uncertainty evaluation of blackout initiated accident sequences of a typical PHWR

Probabilistic Safety Assessment (PSA) is a systematic and comprehensive methodology to evaluate risk associated with a complex engineered technological entity. Accuracy of PSA is influenced greatly by methodology, uncertainties in data/models, unjustified assumptions and incompleteness in analysis. The Risk Analysis (RA) model attempts to simulate reality, thus it is inevitable that there will be simplifying assumptions and idealizations of rather complex processes and phenomena. These simplifications and idealizations will generate uncertainties. The impact of these uncertainties must be addressed if the RA is to serve as a tool in the decision making process.Present work involves uncertainty analysis for station blackout initiated accident sequence. We have compared PSA study results of two codes, FaultTree+ (Isograph Inc.), a commercial software, and PMC (Program for Monte Carlo), developed in-house. Both these codes are based on Monte Carlo methods.We have developed another code, PFA (Program for Fuzzy Arithmetic) for PSA study. It is based on fuzzy arithmetic principle. We have compared Monte Carlo and Fuzzy arithmetic method by using PMC and PFA results. A comparative performance is reported in this work.     

Thermal Analysis and Optimization for Cryopanel of NBI Cryocondensation Pump

Excellent vacuum performance ensures a high beam transmission efficiency of the neutral beam injector （NBI）. The vacuum performance is mainly determined by the cryoperformance of the cryopanel of the cryocondensation pumps which are the main vacuum pumps of NBI. In order to optimize the cryoperformance, the requirements for the temperature distribution and the heat load of the cryopanel are analysed and the factors that affect the cryopanel＇s temperature distribution are studied. The results indicate that the temperature difference of the cryopanel can be reduced by fabricating the cryopanel with high thermal conductivity material, increasing its thickness and cutting the distance between the two upward cooling pipes. The results may be applied to a cryopanel cooled by forced flow liquid helium.     

The analog linear interpolation approach for Monte Carlo simulation of PGNAA: The CEARPGA code

The analog linear interpolation approach (ALI) has been developed and implemented to eliminate the big weight problem in the Monte Carlo simulation code CEARPGA. The CEARPGA code was previously developed to generate elemental library spectra for using the Monte Carlo – library least-squares (MCLLS) approach in prompt gamma-ray neutron activation analysis (PGNAA). In addition, some other improvements to this code have been introduced, including (1) adopting the latest photon cross-section data, (2) using an improved detector response function, (3) adding the neutron activation backgrounds, (4) generating the individual natural background libraries, (5) adding the tracking of annihilation photons from pair production interactions outside of the detector and (6) adopting a general geometry package. The simulated result from the new CEARPGA code is compared with those calculated from the previous CEARPGA code and the MCNP code and experimental data. The new CEARPGA code is found to give the best result.     

Physics Analysis and Optimization Studies for a Fusion Neutron Source Based on a Gas Dynamic Trap

To further investigate the fusion neutron source based on a gas dynamic trap （GDT）, characteristics of the GDT were analyzed and physics analyses were made for a fusion neutron source based on the GDT concept. The prior design of a GDT-based fusion neutron source was optimized based on a refreshed understanding of GDT operation. A two-step progressive development route of a GDT-based fusion neutron source was suggested. Potential applications of GDT are discussed. Preliminary analyses show that a fusion neutron source based on the GDT concept is suitable for plasma-material interaction research, fusion material and subcomponent testing, and capable of driving a proof-of-principle fusion fission hybrid experimental facility.     

Development of 5 T NbTi Superconducting Magnet with 160 mm Warm Bore for Magnetic Separation

A wide-bore 5 T NbTi superconducting magnet, for magnetic separator, with an operational current of 106 A is designed and fabricated. This magnet with a Ф60 mm roomtemperature bore is installed in a vacuum cryostat and immersed in liquid helium. A two-stage 4 K Gifford-McMahon （GM） cryocooler is used to maintain the cooling shield at 70 K and the condenser at 4 K in order to achieve the zero vaporization loss of liquid helium. The cooling power of the GM cryocooler is 1.5 W. In this paper, the design, heat leakage, stress analysis, quench protection characteristics and preliminary test results are presented.     

Analysis of Arc Characteristics and Flow Field in Arc Chamber of High-Voltage SF6 Auto-Expansion Circuit Breaker

A new magnetic hydro-dynamics model for nozzle arc emphasizing the interaction of arc with PTFE （polytetrafluorethylene） vapour is established based on the conservation equations. The interruption of auto-expansion circuit breaker is simulated numerically by finite element method and the influence of PTFE vapour on the arc is analysed with this model. The results reveal that the flow field inside the arc chamber is determined by the arc current, the arcing time, the nozzle arc and the clogging of its thermal boundary. The establishment of quenching pressure relies on both SF6 gas and PTFE vapour that absorbed arc energy in the nozzle. The PTFE vapour leads to an increase in the pressure of nozzle arc obviously, and a decrease in the temperature of arc. But it enhances the temperature of arc at zero current and slows down the decreasing rate of arc temperature as the current decreases.     

Kinematics Simulation and Structure Optimization of Tilting and Lifting Mechanism of ITER Tractor

The ITER （international thermonuclear experimental reactor） tractor is an in-cask remote handling equipment, its tilting and lifting mechanism is important for the tractor operated with forty-five-ton plug in front of the ports of Hot Cell and VV （vacuum vessel） successfully. In order to better analyse the movement of this mechanism and decide the key design parameters accurately, a mathematical model of 7-1ink complicated plane mechanism was built up, and the calculation of design and kinematics simulation were implemented. The established mathematical model was proved to be valid by comparing the calculated result with that of kinematics simulation. Finally, the structure analysis and the optimization of its key part, tilting and lifting frame, were performed to guarantee the frame＇s strength in bearing the heavy load of plug.     

Application of quasirandom points for simulation of gamma radiation transfer

We have considered, a photon transport problem for two configuration types often encountered in nuclear geophysics. The usual Monte Carlo algorithm was modified so that the photon trajectories were constructed with the aid of uniformly distributed LP_τ sequences and their length were restricted. An improvement in the rate of convergence was achieved and the truncation error was estimated. An attempt was made to compare numerically the rate of convergence of the modified algorithm and the usual Monte Carlo that uses pseudo-random numbers.     

Preliminary Design and Analysis of ITER In-Wall Shielding

ITER in-wall shielding （IIS） is situated between the doubled shells of the ITER Vacuum Vessel （IVV）. Its main functions are applied in shielding neutron, gamma-ray and toroidal field ripple reduction. The structure of IIS has been modelled according to the IVV design criteria which has been updated by the ITER team （IT）. Static analysis and thermal expansion analysis were performed for the structure. Thermal-hydraulic analysis verified the heat removal capability and resulting temperature, pressure, and velocity changes in the coolant flow. Consequently, our design work is possibly suitable as a reference for IT＇s updated or final design in its next step.