Computer simulation of ion beam analysis: Possibilities and limitations

Quantitative application of ion beam analysis methods, such as Rutherford backscattering, elastic recoil detection analysis, and nuclear reaction analysis, requires the use of computer simulation codes. The different types of available codes are presented, and their advantages and weaknesses with respect to underlying physics and computing time requirements are discussed. Differences between different codes of the same type are smaller by about one order of magnitude than the uncertainty of basic input data, especially stopping power and cross section data. Even very complex sample structures with elemental concentration variations with depth or laterally varying structures can be simulated quantitatively. Laterally inhomogeneous samples generally result in an ambiguity with depth profiles. The optimization of ion beam analysis measurements is discussed, and available tools are presented.     

Commissioning and first results of the ITER-relevant negative ion beam test facility ELISE

The test facility ELISE which was constructed in the last three years at the Max-Planck-Institut für Plasmaphysik (IPP), Garching, is an important intermediate step of the development of the neutral beam system for ITER. ELISE allows gaining an early experience of the performance and operation of large RF driven sources for negative hydrogen ions and will give an important input for the commissioning and the design of the SPIDER and MITICA test facilities at Padua and the ITER neutral beam system. ELISE has gone recently into operation with first plasma and beam pulses. The experiments aim at the demonstration of an ion beam at the required parameters within 2 years of operation until end of 2014, the end of the service contract with F4E for the establishment and exploitation of ELISE.     

BEPC试验束描迹多丝正比室

描述了BEPC试验束e、π描迹用的多丝正比室．阳极触发阴极感应重心读出．介绍了室结构、制造工艺和性能研究。     

重离子束辐照细胞研究的文献计量学分析

应用文献计量学方法和相应的应用软件,借助Web of Science平台对重离子束辐照细胞这一研究主题的相关文献、作者、期刊、机构以及关键词进行定量和系统考察。结果显示,重离子束辐照细胞研究在1990年之后日益活跃并深入;不同品质的重离子束辐照诱导不同类型细胞会产生不同的生物学效应、旁观者效应及其机制、重离子束辐照细胞生物学效应评估模型、重离子束治疗癌症过程中辐照品质选择与控制模型以及相应的计算机程序是该研究主题的重要内容;引入特定指数推测所得该研究主题重要学术期刊与Nature,Proceedings of the National Academy of Sciences of the United States of America,Cancer Research等期刊之间有较高的共被引频次,表明更多科学前沿的突破性成果和思路应用于该主题研究中;此外,该研究主要集中于少数国家、少数机构、少数作者,并且合作相对较少。     

Recent advances for ion beam therapy accelerators using synchrotrons

Ion beam therapy has evolved a lot during the last years. After more than a decade of successful clinical studies and first treatment in hospital environment, the carbon beam treatment, which always relies on a synchrotron as main accelerator, has clearly shown its own potential. The clinical success of carbon beam treatment is indicated by the growing number of new fully clinical based facilities. There is a lot of improvement potential for these facilities in order to increase their treatment quality, functionality and capacity as well as the cost effectiveness of the patient treatment. This article focuses on the currently ongoing investigations to fully explore this potential. It can be concluded that synchrotron based ion beam facilities are improving into many directions. This will further improve their impact on the cancer treatment and consequently their benefit to the whole society.     

重离子辐照柠檬酸菌株的诱变选育

应用不同剂量重离子束12C+6对黑曲霉出发菌株4﹟进行辐照选育,选育出的高产酸菌株进行发酵试验,应用酸碱中和法测定发酵液中柠檬酸的含量。结果表明:当重离子12C+6的辐照剂量为60 Gy时,正突变率最大,为21%。诱变后的菌株通过酸斑法初筛、摇瓶复筛选育出1株菌株H4002,其发酵液中柠檬酸含量比出发菌株4﹟提高了18%。这说明利用重离子束12C+6辐照处理黑曲霉产生菌可以得到高产柠檬酸突变菌株,其诱变效果显著。     

The new external ion beam analysis setup at the Demokritos Tandem accelerator and first applications in cultural heritage

At the 5.5 MV Tandem VdG accelerator of the Institute of Nuclear Physics of N.C.S.R. “Demokritos”, Athens, Greece, an external ion-beam set-up has been recently developed and installed. The aim of this development was to integrate the analytical capabilities of the PIXE, RBS and PIGE ion beam techniques in one experimental set-up, so that to attain a complete elemental and near surface structural characterization of samples in an almost non-destructive way and without any limitation concerning their size or conductive state. A careful 3D mechanical drawing optimized the set-up experimental parameters achieving probe dimensions at the millimeter range (1 mm²) and fulfilling the special requirements imposed for optimum performance of the aforementioned techniques, including the possibility to use heavier, than protons, ion beams. For the digital pulse processing of the X-ray, γ-ray and charged particle detector signals, novel hardware and software tools were developed based on a custom FPGA configuration.The first applications were focused in the quality control of materials that have been intentionally contaminated with a particular tracer-element (“tagged” materials). The tagged materials which were developed and tested are technologically authentic replicas of ancient attic ceramics with black glazed decoration. Analytical diagnostic studies were carried out for a few representative paintings of contemporary Greek painters in order to identify and document materials/pigments and techniques and eventually to prevent trade of fakes. Finally, ancient glass beads were also examined with respect to the sodium concentration and its in-depth homogeneity.     

Development of function-graded proton exchange membrane for PEFC using heavy ion beam irradiation

The graded energy deposition of heavy ion beam irradiation to polymeric materials was utilized to synthesize a novel proton exchange membrane (PEM) with the graded density of sulfonic acid groups toward the thickness direction. Stacked Poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) films were irradiated by Xe⁵⁴⁺ ion beam with the energy of 6 MeV/u under a vacuum condition. The induced trapped radicals by the irradiation were measured by electron spin resonance (ESR) spectroscopy. Irradiated films were grafted with styrene monomer and then sulfonated. X-ray photo-electron spectroscopy (XPS) spectra showed that the densities of sulfonic acid groups were controlled for injection “Surface” and transmit “Back” sides of the fabricated PEM. The membrane electrode assembly (MEA) fabricated by the function-graded PEM showed improved fuel cell performance in terms of voltage stability. It was expected that the function-graded PEM could control the graded concentration of sulfonic acid groups in PEM.     

无损检测用加速器束流稳定性分析系统的研制

介绍了单道脉冲幅度分析系统对电子直线加速器每个宏脉冲内产生的电子束流稳定性的实时测量方法和对打靶产生的X射线剂量率进行动态监测的分析处理系统的研制与开发。介绍了单道分析器的原理和硬件组成。后端软件使用面向对象的Visual C^ .net开发完成,软件采用图形化软面板,所有控制和结果显示在计算机屏幕上。系统具有可靠性好、精度高、测量直观、应用软件的界面友好等优点。     

BEPC试验束数据获取系统改进及离线数据分析

运行在BEPC电子直线加速器上的试验束,主要利用在线探测器和离线数据分析选择单粒子事例,满足多种单粒子束流试验.本文介绍了试验束改进后的数据获取系统,以及离线数据分析中的飞行时间谱分析,单粒子判选和粒子击中位置定位等.     

Proton beam writing of long, arbitrary structures for micro/nano photonics and fluidics applications

The last decade has seen proton beam writing maturing into a versatile lithographic technique able to produce sub-100 nm, high aspect ratio structures with smooth side walls. However, many applications in the fields of photonics and fluidics require the fabrication of structures with high spatial resolution that extends over several centimetres. This cannot be achieved by purely magnetic or electrostatic beam scanning due to the large off-axis beam aberrations in high demagnification systems. As a result, this has limited us to producing long straight structures using a combination of beam and stage scanning. In this work we have: (1) developed an algorithm to include any arbitrary pattern into the writing process by using a more versatile combination of beam and stage scanning while (2) incorporating the use of the ubiquitous AutoCAD DXF (drawing exchange format) into the design process. We demonstrate the capability of this approach in fabricating structures such as Y-splitters, Mach-Zehnder modulators and microfluidic channels that are over several centimetres in length, in polymer. We also present optimisation of such parameters as scanning speed and scanning loops to improve on the surface roughness of the structures. This work opens up new possibilities of using CAD software in PBW for microphotonics and fluidics device fabrication.     

Criticality in the fabrication of ion extraction system for SST-1 neutral beam injector

For the heating of plasma in steady-state superconducting tokamak (SST-1) (Y.C. Saxena, SST-1 Team, Present status of the SST-1 project, Nucl. Fusion 40 (2000) 1069–1082; D. Bora, SST-1 Team, Test results on systems developed for the SST-1 tokamak, Nucl. Fusion 43 (2003) 1748–1758), a neutral beam injector is provided to raise the ion temperature to 1 keV. This injector has a capability of injecting hydrogen beam with the power of 0.5 MW at 30 keV. For the upgrade of SST-1, power of 1.7 MW at 55 KeV is required. Further, beam power is to be provided for a pulse length of 1000S. We have designed a neutral beam injector (S.K. Mattoo, A.K. Chakraborty, U.K. Baruah, P.K. Jayakumar, M. Bandyopadhyay, N. Bisai, Ch. Chakrapani, M.R. Jana, R. Onali, V. Prahlad, P.J. Patel, G.B. Patel, B. Prajapati, N.V.M. Rao, S. Rambabu, C. Rotti, S.K. Sharma, S. Shah, V. Sharma, M.J. Singh, Engineering design of the steady-state neutral beam injector for SST-1, Fusion Eng. Des. 56 (2001) 685–691; A.K. Chakraborty, N. Bisai, M.R. Jana, P.K. Jayakumar, U.K. Baruah, P.J. Patel, K. Rajasekar, S.K. Mattoo, Neutral beam injector for steady-state superconducting tokamak, Fusion Technol. (1996) 657–660; P.K. Jayakumar, M.R. Jana, N. Bisai, M. Bajpai, N.P. Singh, U.K. Baruah, A.K. Chakraborty, M. Bandyopadhyay, C. Chrakrapani, D. Patel, G.B. Patel, P. Patel, V. Prahlad, N.V.M. Rao, C. Rotti, V. Sreedhar, S.K. Mattoo, Engineering issues of a 1000S neutral beam ion source, Fusion Technol. 1 (1998) 419–422) satisfying the requirements for both SST-1 and its upgrade. Since intense power is to be transported to SST-1 situated at a distance of several meters from the ion source, the optical quality of the beam becomes a primary concern. This in turn, is determined by the uniformity of the ion source plasma and the extractor geometry. To obtain the desired optical quality of the beam, stringent tolerances are to be met during the fabrication of ion extractor system.

SST-1 neutral beam injector is based on positive ion source. The extraction system consists of three grids, each having extraction area of (width) 230 mm × (height) 480 mm and 774-shaped apertures of 8-mm diameter. To obtain horizontal focal length of 5.4 m and vertical of 7 m, each grid consists of two halves with 387 apertures. Two halves are inclined at an angle of 1.07 ± 0.01°. For long pulse operation, active water cooling is provided by in-laid down of dense network of 22 wavy semicircular (r = 1.1 ± 0.05 mm) cooling channels in the space available between the apertures. The required flatness of the copper plate is 100 μm and positioning tolerance of aperture is ±60 μm. The measurement obtained after fabrication is compared with the specifications. It is pointed out that fabrication within set tolerance limit could be achieved only through process of fabrication and high-resolution measurements.     

Development of a novel reaction chamber for ion beam analysis of large samples

A novel vacuum chamber for ion beam analysis of large-size industrial samples - whose analysis are not feasible in conventional ion beam analysis reaction chambers - has been designed, fabricated and successfully tested. Using the newly developed chamber, both PIXE and RBS analyses could be carried out at the same time and on the same point of the samples. Ion beam analysis using this novel chamber lacks the disadvantages of external beam analysis and benefits the advantages of in-vacuum analysis. This has been achieved by designing a tiny open port in the wall of the reaction chamber to be sealed with a small flat area of sample body where its analysis is of interest. As a case study, two samples of gas turbine blades, a corroded one at highly corrosive environment and a refurbished one after application of certain coatings are analysed using the novel chamber. Experimental results confirm the performance and capability of the reaction chamber.     

Validation of R5 assessment procedure for ITER test blanket module by finite element analysis

Part of the ITER experimental setup will be testing of the first wall blanket module built from EUROFER 97 steel. Lifetime of this component should be predicted with help of defect assessment procedure. This work verifies the application of the R5 assessment code on the 2D test blanket module geometry by using finite element simulations. Verification is based on the evolution of C(t) parameter. Results exhibit good correspondence in predictions provided by R5 and finite element method for different thermo-mechanical loading conditions. These results therefore show applicability of R5 procedure on such complex geometries.     

Design of the reflection magnet and its shielding effect analysis for the neutral beam injector of EAST

In this paper,a reflection magnet to be installed in the EAST neutral beam injection system is simulated and designed.The field intensity of reflection magnet of 42-cm maximum bending radius is about 1.539×10-1 T for 100 keV deuterium beam.The shielding cage is formed by rods.Using the ANSOFT software,the magnetic shielding effect was estimated at about 3% at the magnet pole region.     

Micro-fluidic target chamber machined by proton beam writing for the in situ analysis of gas absorption in synthetic crystals

Many synthetic crystals used for chemical and industrial applications have special internal structures, e.g. nano-pores, which allow separating different gases and fluids. Ion beam analytical methods can be used to study the gas diffusion and absorption in these materials in situ and to visualize their inner surfaces which affect these processes. For this purpose, a small target chamber was constructed in PMMA (polymethyl methacrylate) using proton beam writing (PBW). This micro-fluidic structure enables the establishment of a defined atmosphere around a crystal and allows the simultaneous ion beam analysis. In order to confine the gas from the high vacuum in the measurement chamber Si₃N₄-windows of 200 nm thickness were thermally bonded to the structured PMMA block yielding a closed target chamber with the possibility to accomplish PIXE and RBS measurements. In addition, two capillaries were connected to the chamber for gas inlet and evacuation. First tests showed that the construction is leak-proof and allows to establish a defined atmosphere. After that, the Argon gas diffusion into Zn(tbip)-crystals was studied. These measurements have shown unexpectedly high nickel concentrations in the host crystal which reduces the Argon density in these areas after absorption, because the Ni atoms decrease the pore size by replacing Zn-atoms in the Zn(tbip)-lattice. It could be demonstrated that gas diffusion and absorption in organic crystals can be studied in situ with high lateral resolution using ion beam analysis in a dedicated target chamber machined by PBW.     

Gate/Geant4-based Monte Carlo simulation for calculation of dose distribution of 400 MeV/u carbon ion beam and fragments in water

The applications of carbon ion beam in tumor therapy have attracted more attention in recent years.Monte Carlo simulation is an important approach to obtain accurate radiotherapy parameters. In this work, a400 Me V/u carbon ion beam incident on water phantom was simulated with Gate/Geant4 tools. In methods, the authors set up a carbon ion beam source according to the experiment parameters of Haettner, defined the geometries and materials, set up the physics processes, and designed the means of information collection. In results,the authors obtained the longitudinal dose distribution, the lateral dose distribution, and the relative uncertainty of dose. The dose contributions of all kinds of fragments were calculated detailedly and compared with the Francis results. This work is helpful for people's understanding of the dose distributions produced by carbon ion beam and fragments in water. The simulation method is also significative for radiotherapy treatment planning of carbon ion beam, and it is easy to extend. For obtaining a special result, we may change the particle energy, particle type,target material, target geometry, physics process, detector,etc.     

AC operation of large titanium sublimation pumps in a magnetic field: Results of the test stand for the W7-X neutral beam injectors

A neutral beam injection (NBI) system is being built for the Stellarator experiment Wendelstein 7-X (W7-X) currently under construction at IPP Greifswald. The NBI system consists of two injectors which are essentially a replica of the system present in the Tokamak experiment ASDEX-Upgrade at IPP Garching. A vacuum system with high pumping speed and large capacity is required to ensure proper vacuum conditions in the neutral beam line. For this purpose, large titanium sublimation pumps (TSP) are installed inside the NBI boxes, consisting of 4 m long hanging wires containing Ti and the surrounding condensation walls. The wires are DC ohmically heated up with 142 A to Ti sublimation temperature. A TSP system has been operated since many years in the AUG-NBI system, sublimating Ti in the pauses between the plasma discharges, when no magnetic field is present. However, at W7-X the superconducting coils generate a magnetic field permanently during experimental campaigns, whose stray B field with a maximum of 30 mT, affects the TSPs. Operated with DC, the wires would be deflected against the surrounding panels due to the Lorentz force. A simple possible solution is heating with AC, which reduces the wire deflection amplitude, inducing a risky wire oscillation. The feasibility of the AC operation in an equivalently strong B field such as the stray B field around W7-X has been demonstrated in a test stand for different AC waveforms and frequencies. Several test campaigns have shown no qualitative difference in the pumping properties between AC and DC operation of the TSP and no critical dynamic behaviour of the wires.     

A segmented conical electric lens for optimization of the beam spot of the low-energy muon facility at PSI: a Geant4 simulation analysis

The low-energy muon facility at PSI provides nearly fully polarized positive muons with tunable energies in the keV range to carry out muon spin rotation (LE-μSR)experiments with nanometer depth resolution on thin films,heterostructures,and near-surface regions.The low-energy muon beam is focused and transported to the sample by electrostatic lenses.In order to achieve a minimum beam spot size at the sample position and to enable the steering of the beam in the horizontal and vertical direction,a special electrostatic device has been implemented close to the sample position.It consists of a cylinder at ground potential followed by four conically shaped electrodes,which can be operated at different electric potential.In LEμSR experiments,an electric field at the sample along the beam direction can be applied to accelerate/decelerate muons to different energies (0.5-30 keV).Additionally,a horizontal or vertical magnetic field can be superimposed for transverse or longitudinal field μSR experiments.The focusing properties of the conical lens in the presence of these additional electric and magnetic fields have been investigated and optimized by Geant4 simulations.Some experimental tests were also performed and show that the simulation well describes the experimental setup.