CCD质子辐照损伤效应的三维蒙特卡罗模拟

针对空间质子诱发CCD性能退化问题,开展了CCD质子辐照效应的三维蒙特卡罗模拟研究。采用三维蒙特卡罗软件Geant4模拟计算了不同能量质子在Si和SiO₂中的射程及Bragg峰,分析了不同能量质子在材料中能量沉积的过程,并将模拟结果与相关数据进行对比,模拟误差在5%以内。根据质子与材料相互作用的物理过程,选取了合适的Lindhard分离函数,添加合适的物理过程,模拟计算了不同能量质子在SiO₂中的电离能量损失和Si中的非电离能量损失,并将结果与国外相关数据进行对比。根据CCD的生产工艺参数,建立了单个像元的三维模拟模型,确定了质子辐照损伤的灵敏体积,模拟计算了不同能量质子在像元灵敏体积内的电离能量沉积与非电离能量沉积,分析了CCD不同能量质子的辐照损伤差异产生的机理。结合粒子输运计算结果与CCD质子辐照实验结果,分析了质子辐照诱发CCD辐射敏感参数退化的物理机制。     

高能质子在散裂靶中的能量沉积计算与实验验证

高能质子在散裂靶中的能量沉积是散裂靶中子学研究的重要内容之一,准确掌握高能质子在散裂靶中引起的能量沉积分布与瞬态变化是开展散裂靶热工流体设计的重要前提.本文采用MCNPX,PHITS与FLUKA三种蒙特卡罗模拟程序,计算并比较了高能质子入射重金属铅靶、钨靶的能量沉积分布及不同粒子对总能量沉积的占比贡献;针对高能质子入射金属钨靶的能量沉积实验数据空白,采用热释光探测器阵列测量了250 MeV质子束入射厚钨靶的能量沉积分布,实验结果表明蒙特卡罗模拟程序在散裂靶中能量沉积的计算结果具有较高的可靠性.     

GEANT4SPE质子屏蔽和半导体材料辐射效应模拟

利用蒙特卡罗软件GEANT4模拟太阳宇宙射线中能量为1 MeV~10 GeV质子对航天飞行器的影响,透射质子对半导体材料的损伤效应,计算外壳铝层对质子能谱的屏蔽效应.模拟结果表明,质子在介质中的线性能量转移、射程等和参考数据吻合较好;沿质子轨迹纵向能量沉积出现Bragg峰,且非弹性作用是影响能量沉积Bragg曲线的重要因素;对于半导体Si材料,反冲原子主要分布在质子轨迹线周围,并沿轨迹线横向‘扩散’,浓度降低;Al层屏蔽使入射质子能谱硬化,当Al层厚度超过10 mm时,厚度增加对屏蔽效果的改善不明显,反而次级粒子辐射增强效应变大.     

加速器电水锤数值模拟与实验研究

强流加速器水介质形成线放电或击穿形成的冲击波对陶瓷真空界面具有破坏作用。为获得该冲击载荷的信息,应用通用软件ANSYS/LS-DYNA建立了一种水下爆炸有限元模型,将电弧放电等效为爆炸源,模拟得到了冲击波传播时序、压力历史曲线及陶瓷板的加速度响应;为验证模型的有效性,应用"针-板"电极水开关在输出电脉冲40～50 ns、幅值100～300 kV可调的10级陡化前沿Marx发生器上开展了电水锤缩比实验研究。实测了不同击穿电压下冲击波峰压、波速和主脉冲宽度,并依据经验公式计算了放电沉积能量和冲击波能量,平均约17%的间隙放电能量转换为冲击波机械能。对冲击波能量与峰压关系进行了拟合,并与数值模拟结果进行了比较,二者变化趋势基本一致,量级上吻合较好。     

300 eV—1GeV质子在硅中非电离能损的计算

非电离能损(NIEL)引起的位移损伤是导致空间辐射环境中新型光电器件失效的主要因素.引起质子在硅中NIEL的作用机理有库仑相互作用和核相互作用,质子能量范围从位移损伤阈能到1 GeV.当质子能量位于低能区时,库仑相互作用占主导地位,采用解析方法和TRIM程序计算NIEL;当质子能量位于高能区时,NIEL主要来自质子与靶原子核的弹性和非弹性相互作用,使用MCNPX/HTAPE3X进行模拟仿真计算由核反应引起的NIEL.实现了能量范围为300 eV—1 GeV的质子入射硅时NIEL的计算.计算结果表明,MCNPX/HTAPE3X可用于计算高能质子在材料中产生的反冲核所引起的NIEL,结合解析方法和TRIM程序可计算得到由于库仑相互作用引起的NIEL.     

电子束横向泵浦柱形KrF系统时电子能量沉积的数值计算与物理分析

本文对电子束横向泵浦柱形Ar、Kr、F₂混合物时电子能量沉积用SANDYL程序作了数值计算,得到了能量沉积效率与混合物总压力,电子能量和混合物成份比的关系。另外,我们还用阻止本领公式对电子、质子能量沉积效率作了粗估,并为了质子束泵浦的准分子激光的理论模拟而进行了电子、质子能量损失的比较。     

质子和中子在硅中位移损伤等效性计算

基于蒙特卡罗软件Geant4,探讨质子与硅的库仑散射和核反应及中子与硅的核反应产生反冲原子沉积非电离能量的过程,建立质子和中子在硅中的非电离能量阻止本领计算方法。在此方法中,描述了原子间库仑散射的物理过程,模拟带电粒子与晶格原子之间的屏蔽库仑散射。计算得到不同能量质子和中子在硅中因库仑散射和核反应产生反冲原子的非电离能量沉积及阻止本领的等效性,计算结果与中子ASTM标准及文献计算得到的质子数据符合很好。     

非弹性核反应对质子束能量沉积的影响

提出了一种比较精确且又省时的质子穿透的解析算法,并给出了考虑核反应后50—250MeV质子在水中的能量沉积,与Monte-Carlo方法的结果进行了比较.结果表明:1)非弹性核反应对质子的能量沉积有明显的影响,特别是对较高能量的质子束入射情况;2)该方法计算效率比Monte Carlo方法高百倍以上.因此,本文方法解决了质子能量沉积计算中效率和精度之间的矛盾,有可能在质子束放射治疗中得到实际应用. 关键词： 质子能量沉积 核反应 截面     

E_p≤3GeV质子入射铅、铋引起的中子产生双微分截面的模拟(英文)

加速器驱动次临界系统(ADS)液态Pb-Bi散裂靶的设计中,需要可靠的理论计算工具精确地预言几个GeV能量范围的质子引起的散裂反应产生的各种粒子和核素。利用蒙特卡罗模拟软件包Geant4计算研究了800 MeV至3 GeV质子入射铅、铋材料引起的中子产生双微分截面。比较了Geant4不同物理模型得到的模拟结果与现有的实验数据。其中,Geant4的QGSP BERT和QGSP INCL ABLA物理模型模拟结果很好地再现了实验数据。本工作证实了Geant4蒙特卡罗模拟软件包适合用于能量高达3 GeV的质子入射铅、铋引起的中子产生双微分截面的模拟计算。     

质子入射AlxGa1–xN材料的位移损伤模拟

氮化镓材料由于优良的电学特性以及耐辐照性能,其与不同含量Al_xGa_1–xN材料组成的电子器件,有望应用于未来空间电子系统中.然而目前关于氮化镓位移损伤机理研究多关注于氮化镓材料,对于Al_xGa_1–xN材料位移损伤研究较少.本文通过两体碰撞近似理论模拟了10 keV—300 MeV质子在不同Al元素含量的Al_xGa_1–xN材料中的位移损伤机理.结果表明质子在Al_xGa_1–xN材料中产生的非电离能损随质子能量增大而下降,当质子能量低于40 MeV时,非电离能损随着Al含量的增大而变大,当质子能量升高时该趋势相反;分析由质子导致的初级撞出原子以及非电离能量沉积,发现不同Al_xGa_1–xN材料初级撞出原子能谱虽然相似,然而Al元素含量越高,由弹性碰撞产生的自身初级撞出原子比例越高;对于质子在不同深度造成的非电离能量沉积,弹性碰撞导致的能量沉积在径迹末端最大,而非弹性碰撞导致的能...     

Laser-accelerated protons with energy-dependent beam direction

The spatial distribution of protons, accelerated by intense femtosecond laser pulses interacting with thin target foils under oblique irradiation are investigated. Under certain conditions, the proton beams are directed away from the target normal. This deviation is towards the laser forward direction, with an angle that increases with the level and duration of the amplified spontaneous emission pedestal before the main laser pulse. In addition, for a given laser pulse, this beam deviation increases with proton energy. The observations are discussed in terms of different electron acceleration mechanisms and target normal sheath acceleration, in combination with a laser-controllable shock wave locally deforming the target rear surface.     

The formation of an intense secondary pulsed molecular beam and obtaining accelerated molecules and radicals in it

A method for obtaining an intense secondary pulsed molecular beam is described. The kinetic energy of molecules in the beam can be controlled by vibrational excitation of the molecules in the source under high-power IR laser radiation. A compression shock (shock wave) is used as a source of secondary beams. The shock wave is formed in interaction between an intense pulsed supersonic molecular beam (or flow) and a solid surface. The characteristics of the secondary beam were studied. Its intensity and the degree of gas cooling in it were comparable with the corresponding characteristics of the unperturbed primary beam. Vibrational excitation of molecules in the shock wave and subsequent vibrational-translational relaxation, which occurs when a gas is expanded in a vacuum, allow the kinetic energy of molecules in the secondary beam to be substantially increased. Intense [≥10²⁰ molecules/(sr s)] beams of SF₆ and CF₃I molecules with kinetic energies approximately equal to 1.5 and 1.2 eV, respectively, were generated in the absence of carrier gases, and SF₆ molecular beams with kinetic energies approximately equal to 2.5 and 2.7 eV with He (SF₆/He=1/10) and H₂ (SF₆/H₂=1/10) as carrier gases, respectively, were obtained. The spectral and energy characteristics of acceleration of SF₆ molecules in the secondary beams were studied. The optimal conditions were found for obtaining high-energy molecules. The possibility of accelerating radicals in secondary molecular beams was demonstrated.     

Monoenergetic proton beams accelerated by a radiation pressure driven shock

We report on the acceleration of impurity-free quasimononenergetic proton beams from an initially gaseous hydrogen target driven by an intense infrared (λ=10 μm) laser. The front surface of the target was observed by optical probing to be driven forward by the radiation pressure of the laser. A proton beam of ～MeV energy was simultaneously recorded with narrow energy spread (σ～4%), low normalized emittance (～8 nm), and negligible background. The scaling of proton energy with the ratio of intensity over density (I/n) confirms that the acceleration is due to the radiation pressure driven shock.     

Frequency conversion and amplification by stimulated electromagnetic shock radiation (SESR)

The coherent response of a polarizable medium to the radiation stimulated by the interaction of an incident coherent electromagnetic wave with a charged-particle beam, moving with greater than critical speed, results in intense electromagnetic radiation in the form of one or more shock fronts. The shock frequencies are shifted significantly from that of the incident wave and are tunable by parametric variation of the incident beams. The mechanism for this new effect (SESR) differs fundamentally from the laser mechanism. Production of intense quasi-coherent x-ray radiation by SESR obviates the need for x-ray mirrors and is not inhibited by the large spontaneous emission rates at these frequencies. Substantial fraction of the particle-beam energy can be converted into frequency-shifted radiation, with intensity larger than that of the incident wave, because of quadratic dependence on the interaction distance in the medium of the energy radiated into SESR, as compared to the linear dependence of Cerenkov radiative energy. Specific shock frequencies cross from below to above a given resonance frequency of the medium as the relevant two level populations become inverted. This dynamical dependence of the shock frequencies on the level populations provides the basis for new pumping and amplification mechanisms. An example of a possible SESR-based transducing-amplification system is described.     

脉冲宽度对准单能质子能量的影响

使用1维粒子模拟程序LPIC+模拟了不同脉冲宽度的P极化超短强激光脉冲与稠密冷等离子体靶的相互作用.模拟结果表明:激光有质动力首先推动表层等离子体形成无碰撞激波,然后激波向靶内传播,俘获靶内的质子并将其反射加速,反射质子的速度约为离子声速的2倍.当使脉冲宽度与靶厚互相匹配时,也就是靶厚等于离子声速与激光脉冲宽度的乘积时...     

强流重离子束驱动的高能量密度物理研究进展

强流高能离子束可以准等容加热任何高密度样品,制备出尺度大、状态均匀、内部无冲击波的高能量密度物质,为实验室研究高能量密度物理提供了一种独特的新手段。介绍了国内外典型的强流重离子加速器装置及其与高能量密度物理相关的关键参数设计和研究规划;展示了基于粒子和流体模拟的离子束驱动高能量密度物质产生和状态演化规律进展;介绍了一套兼具高时空分辨和高穿透力的高能电子成像诊断技术;分析了中低能区离子束与等离子体相互作用过程中的碰撞和电荷交换微观机制,以及激光加速超短超强离子束在等离子体中的非线性输运和欧姆能损机制。     

金刚石探测器用于C-ADS注入器Ⅱ束损探测的模拟研究

加速器驱动次临界系统C-ADS 注入器Ⅱ采用强流超导质子直线加速器,设计流强达到10 mA。强流质子束产生的束流损失有可能损伤超导腔,需要专用的束流损失监测系统进行监测,束流损失探测器(BLM) 需要在高能量沉积导致超导腔失超之前提供警报。通过MCNPX 模拟计算10 MeV 质子在半波谐振腔(HWR)不同位置损失产生的辐射场,比较选取超导腔管道进出口处4 个位置为推荐束损探测器放置的位置,结合HWR腔结构和束损探测器选择的影响因素,计算了次级辐射在金刚石探测器中的能量沉积以及1° ~ 5°不同质子入射角度对探测的影响。结果表明,根据不同位置处探测器的能量沉积关系可以推断出束损点;不同入射角度不会影响生成粒子的能量分布,只轻微影响生成粒子的数目。The Chinese Accelerator Driven Subcritical System (C-ADS) injector II consists of super-conduction accelerating section which is half wave resonator (HWR), the designed beam intensity is 10 mA. To avoid the damage to the resonator due to proton beam loss, special Beam Loss Monitor (BLM) system is essential. BLM system could provide alarm signal when high energy deposition occurs which may cause the resonator quenching. Radiation field of 10 MeV proton lost at different point of the HWR are simulated with MCNPX, BLM could be set at proper positions based on the simulation. Considering the structure of HWR and the BLM detector selecting influence factor, radiation energy deposition in the diamond detector are simulated with MCNPX when the proton incidence angle change from 1°  5°, Possible beam loss point can be deduced from the relationship of energy deposition in detectors at different locations. The results indicate that energy spectra of secondary particles are independent with incidence angle; the number of secondary particles may be influenced slightly.     

Effect of proton and ion beam treatment on cyclic olefin copolymer parts prepared via injection molding

The aim of this study is to analyze the effect of proton and ion beam treatment on injection molded plastic parts. We employed cyclic olefin copolymers (COCs) as a resin for the manufacturing. A light guide panel was designed and fabricated via injection molding. The size and fluence of ions were changed for the analysis. The physical and chemical properties of the samples irradiated with proton and nitrogen ion beams were investigated through UV–Vis spectroscopy, FT-IR, differential scanning calorimetry (DSC), nanoindentation, residual stress, and electrical analyses. The penetration behavior of ion beams was modeled numerically, and the injection molding process was simulated. The finding showed that the irradiation of proton and nitrogen ion beams led to a change in the chemical structure and energy level of the samples. We anticipate that this study could provide a meaningful strategic way to engineer a polymeric part for broader applications using proton and ion beams.     

聚酯材料在脉冲电子束辐照下的动力学效应与材料参数

对聚酯材料在电子束辐照下的动力学效应进行了研究。采用Monte Carlo方法,计算了脉冲电子束在聚酯材料中的能量沉积;采用流体动力学方法,对聚酯材料在电子束辐照下的热击波和喷射冲量进行了数值模拟;采用将喷射冲量和热击波压力的数值结果与实验测量结果进行逼近的方法,得到了聚酯材料的升华能约为1.1 kJ/g,Grüneisen系数的常态值约为0.2。     

辐射烧蚀铝箔数值模拟研究

 利用一维多群辐射输运程序RDMG数值模拟神光II条件下辐射烧蚀铝箔的实验研究,详细描述了X光在铝箔中的辐射输运过程,清楚地显示了辐射热波在铝箔中的传播,给出铝等离子体温度密度的时空分布、铝箔背面出射的X光能谱及出射X光各能区能流随时间的变化,分析出射X光的能区对测量结果的影响,对神光II条件下辐射烧蚀铝箔的厚度范围进行初步的探讨。数值结果与实验结果相吻合。