Study of talcum charging status in parallel plate electrostatic separator based on particle trajectory analysis

Electrostatic separation has been extensively used in mineral processing, and has the potential to separate gangue minerals from raw talcum ore. As for electrostatic separation, the particle charging status is one of important influence factors. To describe the talcum particle charging status in a parallel plate electrostatic separator accurately, this paper proposes a modern images processing method. Based on the actual trajectories obtained from sequence images of particle movement and the analysis of physical forces applied on a charged particle, a numerical model is built, which could calculate the charge-to-mass ratios represented as the charging status of particle and simulate the particle trajectories. The simulated trajectories agree well with the experimental results obtained by images processing. In addition, chemical composition analysis is employed to reveal the relationship between ferrum gangue mineral content and charge-tomass ratios. Research results show that the proposed method is effective for describing the particle charging status in electrostatic separation.     

带电粒子轨迹的随机跟踪与图形分析

为了真实地描述带电粒子束的光学特性,文章对粒子轨迹跟踪中粒子初始条件的随机抽样进行了探讨。粒子的发射面包括平面、圆柱面和球面;分布函数既可由解析形式表示,又可由数值形式给出。其次,为了有效地利用轨迹跟踪结果对带电粒子束特性进行系统的分析,文章还探讨了粒子轨迹的图形处理和分析,内容包括轨迹的样条拟合、轨迹和束包络图形的绘制、象的尺寸及其位置的确定,以及任意横截面上粒子分布图形的绘制。     

磁四极透镜的Lie代数分析--三级近似

用Ｌｉｅ代数方法分析了带电粒子在四极透镜中的运动，得到六维相空间中粒子轨迹的三级近似解，并包含了运动的相对论效应。当需要时，还可以推展到更高级像差。     

Computer simulation of polarization characteristics of channeling radiation for relativistic electrons

A computation method for the polarization characteristics of relativistic particle radiation in a crystal has been developed. This method is based on the computer simulation of particle trajectories. Formation of the total radiation spectrum and the Stokes parameters by averaging over the possible electron trajectories under planar channeling has been analyzed. A comparison with experimental data has been made.     

二极磁铁的三级Lie映射

用Ｌｉｅ代数方法分析了带电粒子在二极磁铁中的运动，得到在六维相空间中相对论凿子的三级近似轨迹。     

An electrostatic iris for use in quadrupole SIMS instruments

A simple modification to a SIMS energy analyser which allows the flux entering the mass spectrometer to be controlled is described. This enables multi-element analysis for matrix and impurity species from both insulating samples under simultaneous electron charge compensation and conducting samples. In contrast to the technique of applying a voltage offset to the target to suppress high intensity signals the modification allows the field between the sample and the analyser to remain constant so that discharging electron beams on insulators, and low energy ion beams are not deflected from the analysis region by a large change in sample potential when switching from an impurity to a matrix channel.     

Deflection of high-energy charged particles in quasi-channeling states in bent crystals

Planar quasi-channeling of high-energy charged particles in a bent crystal is studied using a computer analysis of particle trajectories. It is discovered that for a small crystal bend, far from the critical one, quasi-channeled particles are deflected to the side opposite to the bend, i.e., a “volume reflection” of the particles (positive and negative) by the field of the bent atomic planes takes place. Moreover, it is shown that the volume capture of quasi-channeled particles into the channeling regime in a bent crystal due to multiple scattering by crystal electrons and nuclei, which was already known for positive particles, also occurs for negative particles, and the probability is even higher than for positive ones.     

Tagged Particles in Monte Carlo Calculations of Radiation Transfer Using the Prizma Computer Program

The additional possibilities due to the introduction into the PRIZMA program, intended for performing Monte Carlo calculations of linear radiation transfer problems, of a particle tagging technique are studied. In calculations, it is often necessary to estimate the contribution of particles which were in some particular situation. The tagged-particle method was developed to obtain such results. A particle is tagged with a marker and the results are recorded as a function of whether or not the particle is tagged. To solve multivariant problems, arising in the calculation of the effects due to small perturbations, a special method was developed for simulating trajectories using tagged particles. This method makes it possible to obtain in a single calculation correlated results for all variants of the problem. The possibilities of the tagged-particle method and the special method of simulation are illustrated for numerical examples.__________Translated from Atomnaya Energiya, Vol. 98, No. 5, pp. 386–393, May 2005.     

A simple model for straggling evaluation

Some straggling models had largely been abandoned in favor of Monte Carlo simulations of straggling which are accurate but time consuming, limiting their application in practice. The difficulty of simple analytic models is the failure to give accurate values past 85% of the particle range. A simple model is derived herein based on a second order approximation upon which rapid analysis tools are developed for improved understanding of material charged particle transmission properties.     

Analog Computer for Quadrupole Magnet Design

In the design of particle accelerators, magnets are sometimes used to bend the paths of charged particles in linear accelerators for focusing and defocusing purposes. These magnets, in the present case, are known as quadrupoles. Their design hinges on the solution of certain mathematical expressions of particle trajectories. A computer of the analog type was constructed to solve the equations and so facilitate magnet design. The analog computer for this application has dials labeled "L", "?", and "?". The settings of these dials represent the design parameters under study. The operator can set the dials of each stage to any of thousands of different combinations of L, ?, and ?. The results of his settings may be observed on a CRO screen. He can then proceed to search for the best combination of control settings with regard to their effect on particle trajectories. Once having found a satisfactory combination, the corresponding magnet design parameters are obtained from the settings of the controls. Three features of construction required special consideration. These were: the high gain, minimum phase shift, and minimum crosstalk. These items and others are discussed in the article from the practical as well as the theoretical point of view.     

辐射法制备Fricke凝胶剂量计

辐射剂量验证技术是肿瘤放射治疗过程中的关键技术,Fricke凝胶剂量计因其制备简单、组织等效性好正逐步成为研究的热点。本研究采用辐射交联"一步法"制备Fricke凝胶剂量计,利用傅里叶红外光谱仪(Fourier transform infrared spectrometer,FTIR)、X线衍射仪(X-ray diffractometer,XRD)与热重分析仪(Thermo-gravimetric analyser,TGA)等仪器对凝胶样品的化学结构和成分进行了分析,利用分子动力学模拟研究了亚铁离子在凝胶剂量计中的扩散行为,并在医用加速器下对凝胶进行辐照,利用多功能酶标仪测定凝胶的辐射剂量响应。结果表明,辐射法制备的Fricke凝胶剂量计中,聚丙烯酸链可以抑制亚铁离子在凝胶样品中的扩散行为,添加二甲酚橙(Xylenol orange,XO)可以改善Fricke凝胶剂量计的剂量敏感性。     

The design and thermohydraulics study of the HTR-10 High Temperature Helium Experimental Loop

A High Temperature Helium Experimental Loop (HTHEL) for the purpose of studying the transportation and deposition behavior of solid fission products in high-temperature helium coming from the steam generator (SG) in the 10 MW High Temperature Gas-cooled Test Reactor (HTR-10) is studied and designed. Through the optimal design based on thermohydraulics analysis, the three-sleeve structure of deposition sampling device (DSD) could realize full-length temperature control evenly and simulate the physical environment of the heat transfer tube of SG in the HTR-10 in the sense of thermohydraulics, which could be used to study the original source term in the primary circuit. The simulation of the graphite dust particle trajectories in the DSD are shown and it is elucidated that DSD could also be used to study the behavior of graphite dust in the high temperature helium in the SG of HTR, which will provide deeper understanding for the analysis of source terms of HTR-10.     

均匀二极磁场的李代数分析

用要代数方法分析了带电粒子在二级磁场中的传输及其像差问题。     

An ab initio Monte Carlo study of low energy positron and electron implantation in elemental metals and multilayers

A Monte Carlo code developed at Brookhaven to study positron and electron implantation in solids will be discussed. This code models the trajectories of a large number of positrons or electrons as they move through the material and uses this information to calculate stopping profiles, backscattered fractions and transmitted fractions. The particle-atom interactions are incorporated via elastic and inelastic scattering cross-sections. The incident particle energies vary from 1 to 10 keV and the simulation stops when the particle energy goes down to 25 eV or if the particle is backscattered. Main results of our Monte Carlo simulations of the mean implantation depth and implantation profiles for both semi-infinite metallic elements and multilayers will be discussed.     

Screener3D:a gaseous time projection chamber for ultra-low radioactive material screening

In experiments searching for rare signals,back-ground events from the detector itself are some of the major factors limiting search sensitivity.Screening for ultra-low radioactive detector materials is becoming ever more essential.We propose to develop a gaseous time projection chamber(TPC)with a Micromegas readout for radio screening.The TPC records three-dimensional tra-jectories of charged particles emitted from a flat sample placed in the active volume of the detector.The detector can distinguish the origin of an event and identify the particle types with information from trajectories,which significantly increases the screening sensitivity.For a particles from the sample surface,we observe that our proposed detector can reach a sensitivity higher than 100 p Bq m-2 within two days.     

Formation of spectral characteristics of channeling radiation from 800 to 2000 MeV electrons and positrons in a thin silicon crystal

The influence of the tails of particle trajectories on planar channeling radiation (CR) spectra from relativistic (800-2000 MeV) electrons and positrons in a thin silicon crystal is investigated. It is shown that the trajectory tails significantly change the CR spectra from electrons and positrons in specific parts of the spectra compared to calculations which do not take into account this effect.     

用于粒子鉴别的布喇格曲线谱学探测器

在重离子反应中,气体电离室广泛地用于离子鉴别,这是由于它制造简单、成本低、便于维护,特别是可设计成不同长度,厚度均匀,相对于半导体探测器而言还有附加的优点,如无辐照损伤、无脉冲幅度亏损等。这类电离室通常有阳极、阴极和栅极三个电极,所施加的电场是平行于入射粒子轨迹的。     

远东地区核风险厂址释放的气载放射性污染物长距离迁移的模拟

气载放射性物质在大气中的长距离迁移问题逐渐受到关注。我们开发建立了轨迹模式TraModel和粒子扩散模式ParModel,用以模拟计算气载物质的迁移轨迹和扩散影响,并利用欧洲示踪实验(ETEX)数据对模式进行验证,同时也与国外同类模式进行了比对。结果表明,本研究所开发的模式具有较高的精度。利用美国国家环境预测中心(NCEP)的气象数据进行模拟计算,将其用于模拟我国田湾、秦山核电站以及俄罗斯远东Vladivostok(海参崴)核风险厂址释放的放射性物质的跨国界迁移。模拟结果表明,相对于等熵轨迹,三维轨迹能更真实地反映污染物的实际迁移,对于长距离迁移问题的概率分析,等熵轨迹和三维轨迹的模拟结果基本相同。释放高度对大气迁移途径有显著影响,故由一个释放高度得到的模拟结果用于其它释放高度时应当慎重。此外,由于在中国东部沿海地区气象场的复杂性,特别是受东亚季风的影响,释放点不同地理位置的影响结果也是很不相同的。这些模式、方法今后可用于开展远东核风险厂址大气迁移的概率风险分析以及事故后果评价。     

Wave packet evolution of the valence state of a hyperthermal sodium ion impinging on a copper surface

One electron transfer in hyperthermal energy collisions of Na⁺ ions with clean Cu(1 0 0) surfaces is studied using a wave-packet propagation algorithm based on a semi-empirical model potential. Three specific collision events are considered in which the Na particle comes out either reflecting off the surface or after multiple scattering processes within the target. The evolution operator, depending parametrically on the trajectories of the atoms leaving the sample, is discretized via a split approximation and a three-point differentiation scheme. In this way, the time-reversed state of the projectile is calculated and projected onto the initially filled states of the target to obtain the neutralization probability of the scattered atomic level. The calculations are consistent with literature values [8].