深层治癌重离子束的配送

利用重离子束流治疗深层肿瘤的临床实验将在中国科学院近代物理研究所（IMP）进行。束流配送系统是重离子治癌临床实验的关键系统,输送束流均匀辐照照射野。重离子束流经过回旋加速器初步加速,注入重离子冷却储存环（CSR）的主环（CSRm）,累积、加速后通过共振引出,经深层治癌束运线输送到照射野。针对重离子治癌要求和现场可利用空间,优化设计了束运线,得到了灵活调节束斑尺寸的透镜参数。通过模拟束流扫描过程,验证了扫描系统的可行性。     

300keV,5电极负离子束系统的数值模拟研究

根据负离子-中性束注入器中强流负离子束引出、加速系统的特点,建立了为辅助设计强流负离子束系统而对其进行数值模拟研究的模型和计算程序,计算了负离子束和伴随引出的电子束在系统电、磁场共同作用下的运动行为,研究了系统束流密度、负离子初始温度以及负离子剥离损失和末电极孔位移等相关参数对负离子束光学特性的影响,并对系统的电、磁场位形进行了优化。对300keV,5电极负离子束系统的初步优化结果表明:该系统磁场可将伴随引出的电子束在低能下偏转到作为电子接收极的引出电极上;对引出流密度为21mA·cm~(-2)的H~-离子束,当H~-离子在引出区的剥离损失为20％时,由系统出射的各小束的均方根角度和85％小束的散角可分别达到0.327°和0.460°。     

产额大于1.5×1010n/s中子管引出/加速系统的物理设计

根据高产额(>1.5×1010n/s)中子管对引出/加速系统的要求,完成了在180kV引出/加速电压下,加速离子束流1.1mA的新型屏蔽式引出/加速系统的物理设计,与普通中子管比较,加速电压增加50%,束流增加一个数量级,中子产额增加一个数量级,实现了系统的结构优化.经长期实践考验证明,系统的物理设计合理,为更高产额中子管的研制奠定了基础.     

螺线管透镜对加速管束流匹配的影响研究

螺线管透镜具有轴对称性、结构尺寸小等优点,在束流传输系统中得到了广泛应用,然而螺线管透镜磁场的非线性部分(像差)会导致束流发射度增长,降低束流的传输效率。本文采用TRACK程序模拟,研究了螺线管透镜像差与束流发射度增长的关系,发现束流发射度的增长与磁透镜的磁感应强度有关,同时优化螺线管透镜的磁场均匀性有效抑制了束流发射度增长。此外,基于一种磁场均匀度较高的螺线管透镜研究了离子源引出系统与加速管的束流匹配过程,结果表明相比汇聚入射束和准平行入射束,发散入射束通过加速管后的束流包络较小,束流发散相对较缓慢。     

永磁强流ECR离子源

文章介绍一台2.45 GHz永磁强流ECR离子源,其直径为10 cm,长10 cm,重量不足5 kg,可工作在直流模式和脉冲模式.脉冲模式引出的氢离子束峰值流强大于100 mA,束流密度达到500 mA/cm2;直流模式引出束流达到60 mA,束流密度为300 mA/cm2.两种模式的质子比均达到80%.     

静电单透镜在低能强流离子束输运中的应用

本文介绍北京大学重离子所RFQ组利用静电单透镜进行低能强流离子束束流输运的情况.在北京大学1 MeV ISR RFQ加速器的升级改造中,我们在低能输运段使用了2个静电单透镜进行调束,当引出电压为22kV时,在RPQ入口处得到了归一化均方根发射度为0.12 7× mm·mrad、峰值流强6 mA的脉冲氧离子束(相当于24mA质子束流).以及用静电单透镜聚焦强流氢离子束的初步实验实验.     

HL-2中性束注入器离子束系统的设计计算

在受控核聚变研究中,中性束注入已经成为加热等离子体的有效手段。中性束注入器的关键部分是离子束系统,它的性能决定了中性束注入的效率和效果。文章就大功率中性束注入器离子源及离子引出、加速系统主要工作参数的设计计算方法进行了论述,并给出了HL-2装置中性束注入器离子束系统的计算结果。在强流离子束引出、加速系统束光学特性的数值计算程序中,考虑了离子源等离子体参数、等离子体弥散电子及离子束内部空间电荷效应对束光学性能的影响。计算表明,对于设定的55kev,80A的离子束系统,氢和氘离子束的匹配流密度分别为0.22A·cm~(-2)和0.155A·cm~(-2)。     

用锥形玻璃毛细管聚焦获取MeV能量He~+微米离子束

用锥形玻璃毛细管聚焦离子束方法获取微米离子束成本低、使用方便,我们制备了出口口径35-110μm不等的多种锥形玻璃毛细管,并用其在2×1.7 MV串列加速器上获得了出射束流密度比入射束流密度大的MeV能量He~+微离子束。用金硅面垒探测器(SBD)测量在毛细管与入射束夹角不同条件下出射的微米束的能谱,并对锥形玻璃毛细管聚束的机制做初步定性讨论。     

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。     

增强器共振补偿方案

强流重离子加速器的增强器用于强流重离子的极限累积和加速,其强流束产生的空间电荷效应使束流的工作点分布发散和漂移,并在工作点跨越低阶共振时造成离子束发射度增长甚至带来较大的束流损失。为消除低阶共振对离子束的不利影响,采用多极磁场来对6个低阶共振进行补偿。本文分析了增强器工作点附近的低阶共振,探讨了共振禁带的贡献项及相应的补偿方案,并通过数值模拟验证了增强器的共振补偿方案。结果表明,由增强器色品校正六极场引起的共振增强能通过补偿六极场进行消除,这将有利于增强器强流重离子束的实现。     

Computer investigation of ion beam optics for a Freeman type ion source system

The present work investigates the computer analysis of the ion beam properties produced by a Freeman type system. The extraction for such system is composed of four electrodes that permit to keep a fixed output energy by means of two accelerating gaps and one decelerating gap. The latter allows reducing the beam divergence angle. The combination of the acceleration/deceleration sections provides to keep a low beam emittance at the source outlet. The simulation of single charged argon ion trajectories for a plasma concave of curvature 4 mm was first studied with and without space charge effect using acceleration/deceleration extraction system with the aid of the SIMION computer program. The voltage applied to the accelerating electrode was optimized to accomplish the suitable ion trajectories without hitting the extraction electrode. Then, two additional studies were performed: the influence of the acceleration voltage and extraction voltage on the beam emittance and beam diameter; and the effect of the extraction gap width (distance between the plasma emission surface and the acceleration electrode) on the shape of the ion beam envelope and the position of the ion beam waist. Last, the influence of the space charge on the ion beam envelope was also investigated.     

Numerical research of a 2D axial symmetry hybrid model for the radio-frequency ion thruster

Since the high efficiency discharge is critical to the radio-frequency ion thruster (RIT),a 2D axial symmetry hybrid model has been developed to study the plasma evolution of RIT.The fluid method and the drift energy correction of the electron energy distribution function (EEDF) are applied to the analysis of the RIT discharge.In the meantime,the PIC-MCC method is used to investigate the ion beam current extraction character for the plasma plume region.The beam current simulation results,with the hybrid model,agree well with the experimental results,and the error is lower than 11％,which shows the validity of the model.The further study shows there is an optimal ratio for the radio-frequency (RF) power and the beam current extraction power under the fixed RIT configuration.And the beam extraction efficiency will decrease when the discharge efficiency beyond a certain threshold (about 87 W).As the input parameters of the hybrid model are all the design values,it can be directly used to the optimum design for other kinds of RITs and radio-frequency ion sources.     

Design of an ion extractor system for a prototype ion source experiment for SST-1 neutral beam injector

An ion extractor system has been designed for the steady state superconducting tokamak (SST-1) neutral beam injector (NBI) for an experiment using a prototype ion source with fully integrated regulated high voltage power supply (RHVPS) and data acquisition and control system (DACS) developed at Institute for Plasma Research (IPR) to obtain experience of NB operation. The extractor system is capable of extracting positive hydrogen ion beam of ∼10 A current at ∼20 kV. This paper presents the beam optics study for detailed design of an ion extraction system which could meet this requirement. It consists of 3 grid accel-decel system, each of the grid has 217 straight cylindrical holes of 8 mm diameter. Grids are placed on a specially designed G-10 block; a fiber reinforc plastic (FRP) isolator of outer diameter of 820 mm and 50 mm thickness. Provisions are made for supplying high voltage to the grid system through the embedded feed-throughs. Extractor system has been fabricated, mounted on the SST-1 neutral beam injector and has extracted positive hydrogen ion beam of 4 A at 20 kV till now.     

Negative ion beam extraction in ROBIN

The RF based single driver ?ve ion source experiment test bed ROBIN (Replica Of BATMAN like source in INDIA) has been set up at Institute for Plasma Research (IPR), India in a technical collaboration with IPP, Garching, Germany. A hydrogen plasma of density 5 × 10¹² cm^?3 is expected in driver region of ROBIN by launching 100 kW RF power into the driver by 1 MHz RF generator. The cesiated source is expected to deliver a hydrogen negative ion beam of 10 A at 35 kV with a current density of 35 mA/cm² as observed in BATMAN.In first phase operation of the ROBIN ion source, a hydrogen plasma has been successfully generated (without extraction system) by coupling 80 kW RF input power through a matching network with high power factor (cos θ > 0.8) and different plasma parameters have been measured using Langmuir probes and emission spectroscopy. The plasma density of 2.5 × 10¹¹ cm^?3 has been measured in the extraction region of ROBIN. For negative hydrogen ion beam extraction in second phase operation, extraction system has been assembled and installed with ion source on the vacuum vessel. The source shall be first operated in volume mode for negative ion beam extraction. The commissioning of the source with high voltage power supply has been initiated.     

First results of negative ion extraction with Cs for CRAFT prototype negative beam source

In order to understand the physics and pre-study the engineering issues for radio frequency(RF)negative beam source, a prototype source with a single driver and three-electrode accelerator was developed. Recently, the beam source was tested on the RF source test facility with RF plasma generation, negative ion production and extraction. A magnetic filter system and a Cs injection system were employed to enhance the negative ion production. As a result, a long pulse of 105 s negative ion beam with current density of 153 A m-2 was repeatedly extracted successfully. The source pressure is 0.6 Pa and the ratio of co-extracted electron and negative ion current is around0.3. The details of design and experimental results of beam source were shown in this letter.     

RADI—A RF source size-scaling experiment towards the ITER neutral beam negative ion source

IPP Garching is currently developing a negative hydrogen ion RF source for the ITER neutral beam system. The source demonstrated already current densities in excess of the ITER requirements (>200 A/m² D⁻) at the required source pressure and electron/ion ratio, but with only small extraction area and limited pulse length. A new test facility (RADI) went recently into operation for the demonstration of the required (plasma) homogeneity of a large RF source and the modular driver concept.The source with the dimension of 0.8 m × 0.76 m has roughly the width and half the height of the ITER source; its modular driver concept will allow an easy extrapolation in only one direction to the full size ITER source. The RF power supply consists of two 180 kW, 1 MHz RF generators capable of 30 s pulses. A dummy grid matches the conductance of the ITER source. Full size extraction is presently not possible due to the lack of an insulator, a large size extraction system and a beam dump.The main parameters determining the performance of this “half-size” source are the negative ion and electron density in front of the grid as well as the homogeneity of their profiles across the grid. Those will be measured by optical emission and cavity ring down spectroscopy, by Langmuir probes and laser detachment. These methods have been calibrated to the extracted current densities achieved at the smaller source test facilities at IPP for similar source parameters. However, in order to get some information about the possible ion and electron currents, local single aperture extraction with a Faraday cup system is planned.     

The plume diagnostics of 30 cm ion thruster with an advanced plasma diagnostics system

In order to achieve a better understanding of plume characteristics of LIPS-300 ion thruster, the beam current density, ion energy and electron number density of LIPS-300 ion thruster plume are studied with an Advanced Plasma Diagnostics System(APDS) which allows for simultaneous in situ measurements of various properties characterizing ion thruster, such as plasma density, plasma potential, plasma temperature and ion beam current densities, ion energy distribution and so on. The results show that the beam current density distribution has a double‘wing' shape. The high energy ions were found in small scan angle, while low energy ions were found in greater scan angle. Electron number density has a similar shape with the beam current density distribution.     

在线低能气体离子源

材料中氦和氢积累可引起材料性能的恶化甚至失效。为研究材料内氦和氢的存在形式、氦与氢及缺陷的相互作用、气泡的形成和演变过程以及各种因素的影响,建立一套离子束能量最高20keV的潘宁型气体离子源引出和聚焦系统,与200kV透射电镜联机,在离子注入现场原位观察氦和氢不同注入浓度下材料内部的微观结构及变化过程。对离子源进行氦离子的起弧、引出和聚焦测试。离子源在15–60mA放电电流范围内稳定地工作。在5×10–3Pa和1.5×10–2Pa工作气压下,放电电压约380V和320V。低气压下引出离子束流比高气压下大,且引出束流随放电电流和吸极电压的增加而增加。等径三圆筒透镜有显著聚焦作用,在距透镜出口150cm处,离子束流密度提高一个量级以上。能量10keV左右的氦离子获得束流密度约200nA·cm–2的离子束,可满足多种材料进行在线离子注入和原位电镜观测的需要。     

Experimental Results of Ion Beam Extraction of High-Current Ion Source for EAST Neutral Beam Injector

The first campaign of ion beam extraction tests are completed for EAST NBI high current ion source. The hydrogen ion beam with beam voltage of 80 keV is extracted from tetrode accelerator system. During the experiment, the characteristics of arc discharge and ion beam extraction are studied. The arc power reaches 120 kW and the extracted ion beam power reaches 3 MW. The relationship of some key parameters of arc and beam are investigated, and the details are described in this paper.     

Mass spectrometry improvement on an high current ion implanter

The development of accurate mass spectrometry, enabling the identification of all the ions extracted from the ion source in a high current implanter is described. The spectrometry system uses two signals (x-y graphic), one proportional to the magnetic field (x-axes), taken from the high-voltage potential with an optic fiber system, and the other proportional to the beam current intensity (y-axes), taken from a beam-stop. The ion beam mass register in a mass spectrum of all the elements magnetically analyzed with the same radius and defined by a pair of analyzing slits as a function of their beam intensity is presented. The developed system uses a PC to control the displaying of the extracted beam mass spectrum, and also recording of all data acquired for posterior analysis. The operator uses a LabVIEW code that enables the interfacing between an I/O board and the ion implanter. The experimental results from an ion implantation experiment are shown.