A New Three-Dimensional Code for Simulation of Ion Beam Extraction： Ion Optics Simulator

A new thee-dimensional code, ion optics simulator （IOS）, to simulate ion beam extraction is developed in visual C＋＋ language. The theoretical model, the flowchart of code, and the results of calculation as an example are presented.     

Measurement of Ion Parameters by Ion Sensitive Probe in ECR Plasma

Ion parameters in electron cyclotron resonance (ECR) microwave plasma were measured by ion sensitive probe and were compared with the electron parameters obtained by double Langmuir probe. The effects of gas pressure and microwave power on the ion temperature and density were analyzed. The spatial distribution of the ion parameters was also investigated by the ion sensitive probes with a tunable radial depth installed on different probe windows along the chamber axis. Results showed that the ion density measured by the ion sensitive probe was in good agreement with the electron density measured by the double Langmuir probe. The influence of gas pressure on the ion parameters was stronger than that of microwave power. With the increase in working pressure, the ion temperature decreased monotonously with a decreasing rate larger than that at higher pressure. The ion density first increased to a peak (42.3?1010cm-3) at 1 Pa and then decreased. The ion temperature and density increased little with the increase in the microwave power from 400 W to 800 W. The plasma far away from the resonant point is found to be radially uniform.     

Study on Integral Expression in Measurement of Average Ion Velocity by Multi-Grid Probe

In order to improve the interference rejection performance in the measurement of average ion velocity by multi-grid probe, an integral expression is proposed. The integral expression, differing from other expressions for probe measurement, avoids the differential operation on the I-V characteristics of multi-grid probe measurement; and by this method, the ion average velocity can be figured out directly by the I-V characteristics of multi-grid probe measurement.     

串列加速器升级工程重离子束流能量计算

采用电荷剥离分布公式和稳定核质量数经验公式，对串列加速器升级工程提供的重离子束流能量和电荷剥离效率进行计算。计算结果对根据物理实验需要在高能量与束流强度之间进行取舍有一定的指导意义。     

TEPC壁对重离子束微剂量学测量及相对生物学效应计算的影响

组织等效正比计数器（TEPC）广泛应用于重离子束微剂量学测量,提供用于计算相对生物学效应（RBE）的基础数据。为研究TEPC壁对重离子束微剂量学测量及RBE计算的影响,在蒙特卡罗（MC）模拟中引入理想组织等效正比计数器（Ideal-TEPC）,精确计算得到碳离子束不同水等效深度处的微剂量学量及RBE。Ideal-TEPC和常规TEPC的计算结果表明：TEPC壁会使碳离子束产生较大的辐射场畸变,且会使TEPC测量结果及RBE计算结果产生较大偏差,该偏差随贯穿深度的增加而增大。将TEPC壁视为具有固定水等效厚度的水层可在数值上抵消TEPC壁对RBE计算的影响,但在展宽Bragg峰（SOBP）后端会产生过修正现象。Ideal-TEPC结合MC模拟能有效避免TEPC壁效应及TEPC壁引起的辐射场畸变对重离子束微剂量学量和RBE计算的影响。     

聚焦重离子束溅射制备同位素靶的材料利用率及均匀性研究

研究了聚焦重离子束溅射制备同位素靶的材料利用率和均匀性。通过实验确定了两种溅射距离(7 mm和14 mm)下沉积靶的纵向和横向厚度分布,确定了提高靶均匀性的有效方法——基衬公转和沉积1/2厚度后基衬调头,确定了匹配材料利用率和均匀性的最佳几何参数。制备了5种同位素氧化物靶和9种高熔点金属同位素靶,应用于核物理测量实验。实验表明,源-衬距离为7 mm和14 mm时,在9 mm×10 mm成膜区域内,基衬中心距靶(源)材料水平界面垂直距离为9 mm和11 mm时可获得均匀的靶膜和最高的材料利用率。     

CSR ns级重离子束动力学研究

采用束团在纵向相空间快速旋转的非绝热压缩方法研究了在兰州重离子加速器冷却储存环(HIRFL-CSR)上获取高能ns量级短脉冲重离子束的可行性,利用K-V包络方程对能量为250MeV/u、初始纵向束团长度为200ns、初始动量分散为5×10-4的238U72+离子束团的非绝热压缩过程进行了束流动力学模拟,给出了在束团压缩过程中束流相关参数的变化。结果表明,在CSR上可取得最短为16ns长度的238U72+离子束团,可满足用于高能量密度物理研究的50ns束团长度的要求。     

Power Consumption in Positive Ion Beam Converter with Electrostatic Electron Suppressor

The power recovery characteristics of an in-line direct beam converter provided with electrostatic electron suppressor were studied numerically by tracing the orbits of fast primary ions and secondary charged particles generated along their beam path by collision with background gas molecules. It is shown that, in reference to the electrostatic field potential at the point of impact, the energy distribution of secondary ions impinging on the suppressor has two peaks—one corresponding to a zone of high positive potential surrounding the collector and the other to one of slightly negative potential around the electron suppressor. Secondary electron emission from the suppressor is ascribed mainly to the latter peak, associated with impingement of slower secondary ions. Far much power consumed in secondary particle acceleration is spent for emitting electrons from the suppressor than for secondary ions generated by beam-gas collision. The upper limit of background pressure is discussed on the basis of criteria prescribed for restricting the power consumed in this secondary particle acceleration, as for practical convenience of electrode cooling. Numerical examples are given of calculations based on particle trajectory analysis of both primary ions and secondary particles, for the case of a 100 keV-proton sheet beam 10 cm thick of 35mA/cm² current density.     

脉冲离子束轰击靶的热效应数值模拟

分析了脉冲离子轰击靶膜和衬底的热效应,在能量较低的情形下,离子轰击处理为靶膜表面热流输入。采用有限元程序,对能量为600keV、束流为12mA的不同束斑半径的脉冲离子流轰击Cu基Ti靶的热传导进行了数值计算,得到了热传导清晰物理图象。     

脉冲离子束流聚焦装置的研制

用小型化的质量分析系统进行脉冲离子束流实验研究时,从真空弧离子源中引出的束流脉冲幅度大、能量低,由于空间电荷效应使脉冲束流发散度很大,使得离子束流成分分析的不确定度增大。为克服在有限的空间范围内脉冲离子束流聚焦的困难,研制了一种新的双限束光阑三膜片透镜离子束流聚焦装置。双限束光阑着重减少束流发射度,三膜片透镜则适合小尺度空间的脉冲束流聚焦。计算机模拟的结果符合这种大脉冲离子束流聚焦的设计思想。磁质谱仪应用该聚焦装置后,发散到质量分析器分析盒上的脉冲离子束流幅值从未加聚焦前的115 mA减少至0.06 mA,脉冲离子束流质量分析的不确定度降低。     

重离子束水吸收剂量的电离法实验研究

重离子束水吸收剂量是开展重离子束治疗最基本的物理量。在开展重离子束水吸收剂量的量值复现研究前,需用间接测量的方法开展相关工作以熟悉实验条件。本文用传统电离法开展了能量400 MeV/u、具有6 cm展宽Bragg峰的碳离子束的水吸收剂量测量研究,并评价了重离子束条件下的相关电离室的极化、离子复合修正因子。在电离室的极化和离子复合修正项方面,重离子束水吸收剂量测量的相关不确定度分量显著大于60Co γ辐射水吸收剂量的相关值。用不同电离室测量重离子束水吸收剂量的结果在不确定度允许的范围内符合。以电离室测量为基础,开展更深入的包括量热法绝对测量在内的辐射剂量学研究,对进一步优化重离子束水吸收剂量测量的不确定度至关重要。     

Experimental Study for Absorbed dose to Water of Heavy Ion Beam via Ionization Method

The absorbed-dose to water of heavy ion beam is a fundamental quantity for heavy ion therapy. It is necessary to perform the relevant work with in-direct measurement prior to the study of the reproduction for the absorbed-dose to water of heavy ion beam. The absorbed-dose to water of a carbon ion beam, whose incident energy was 400 MeV/u and spread-out Bragg peak was 6 cm, was studied with conventional ionization method. The correction factors of polarity and ion recombination for the ionization chambers were evaluated with the incident heavy ion beam. The uncertainty components for the measurement of the absorbed-dose to water of heavy ion beam are significantly larger than that of the 60Co γ radiation, in terms of the corrections for the polarity and ion recombination of the ionization chambers. The absorbed-dose to water of heavy ion beam deduced from different ionization chambers is consistent within the acceptance of uncertainty. Based on the measurement with ionization chambers, it is crucial to conduct more intensive research activities of radiation dosimetry including the absolute measurement with calorimetric facility, with the purpose of further optimizing the uncertainty in the measurement for the absorbed-dose to water of heavy ion beam.     

重离子加速器数字电源回读系统

为提高数字电源回读数据的精确性、抑制噪声、降低成本,开发设计了全数字化回读系统。在本系统中,发送端的数字电源控制器通过光纤模块,按专用协议以2 kHz频率发送4种数据;接收端的数字信号采集设备接收、存储每台电源的回读数据,并标记以时间戳。系统采用有效机制保证每条数据通路的时钟同步,并提供了数据分析图形化界面。经现场测试,验证了系统的性能,达到了设计目的,使全数字化回读首次在重离子医用加速器励磁电源系统上得到成功应用。基于其较好的抗干扰性和经济性,未来可在重离子加速器中推广应用。     

重离子肿瘤治疗中的PET设计

文章简单描述HIRFL重离子肿瘤治疗装置布局和PET（正电子断层影像）的总体设计。详细叙述组成PET探测单元的结构，晶体、光纤、MAPMT的选择，读出线路的研制及一些初步测试结果。      

真空弧离子源引出束流在加速空间的分布

采用数码相机直接照相的方法来确定真空弧离子源引出束流在加速空间的分布。实验在动态真空实验系统中进行,系统真空度优于2×10-3 Pa。在离子源脉冲工作的条件下,采用数码相机拍摄到离子源引出束流在加速空间的积分图像,得到引出束流的幅亮度在拍摄平面上的相对分布,然后再通过Abel转换得到引出束流在加速空间的径向分布。实验结果表明:真空弧离子源引出束流近似高斯分布,离子源出口处的束流比靶入口处的束流强40%。     

重离子治癌电源调节器的嵌入式系统

为满足HITFiL重离子治癌装置中对扫描铁电源精确控制的需求,基于EDA技术构建了嵌入式实时控制系统,采用高级RISC微处理器(ARM)+现场可编程门阵列(FPGA)+DA/AD技术实现对磁铁电源系统数字调节器的设计。经现场测试,本套系统运行稳定可靠,达到了设计要求,为今后重离子治癌专用装置的建设应用提供了可靠的技术保障。     

Numerical Study on the Two-Dimensional Temperature Fields of Titanium/Aluminum Double-Layer Target Irradiated by High-Intensity Pulsed Ion Beam

Interaction between high-intensity pulsed ion beam (HIPIB) and a double-layer target with titanium film on top of aluminum substrate was simulated. The two-dimensional nonlinear thermal conduction equations, with the deposited energy in the target taken as source term, were derived and solved by finite differential method. As a result, the two-dimensional spatial and temporal evolution profiles of temperature were obtained for a titanium/aluminum double-layer target irradiated by a pulse of HIPIB. The effects of ion beam current density on the phase state of the target materials near the film and substrate interface were analyzed. Both titanium and aluminum were melted near the interface after a shot when the ion beam current density fell in the range of 100A/cm2 to 200A/cm2.     

湍流模型在堆芯热工水力性能分析中的应用

针对正三角形布置堆芯棒束燃料通道内冷却剂充分发展湍流流场模拟,对比分析了计算流体动力学软件湍流模型对复杂流道内湍流流场模拟结果的影响。结果表明：湍流模型选取的不同对模拟结果有着显著影响,由于堆芯几何结构复杂,冷却剂流动为复杂三维流动,湍流呈高度各向异性。基于各向同性假设的湍流模型不能准确捕捉堆芯内冷却剂的二次流现象。基于求解雷诺应力输运方程的雷诺应力模型（RSM）能够较好地预测复杂流道内的二次流。本工作的研究结果为复杂流道流动换热模拟及深入研究分析堆芯热工水力性能提供了一定借鉴和指导。     

重离子加速器同步定时触发系统的实现

同步定时触发系统是重离子同步加速器的控制核心,控制磁场电源对带电离子束进行同步加速,其对可靠性和定时精度要求高。在重离子治癌、材料辐照等领域的发展中,为了满足这些领域对重离子同步加速器小型化的需求,本文以NIOSII为核心处理器,结合FPGA上的可编程片上系统（SOPC）,实现了一种基于可编程硬件的同步定时触发系统。该系统可控制延时精度,且使用灵活、可靠,易升级,向小型化的同步加速器及重离子治癌等应用工程提供了切实可行的方案。     

快重离子电子能损引起的缺陷产生及其后续效应

快重离子与凝聚态物质相互作用是核物理研究的重要领域之一,近年不断有新的现象发现。文章综述了快重离子电子能损效应研究的历史和概况,重点介绍了快重离子辐照引起的缺陷产生和退火、潜径迹的形成、塑性形变、相变等现象以及相关理论模型,对该领域未来发展趋势给出展望。