New developments in design and applications for pelletron accelerators

Most of the developments over the last several years related to Pelletron accelerator are in the field of accelerator mass spectrometry (AMS) and other low beam current applications with the exception of a very high DC electron recirculation Pelletron. High precision AMS systems based on tandem Pelletrons from 500 kV to 5 MV terminal potential are now in use for routine high precision AMS measurements. Their performance will be reported. In addition, there has been significant advancement in the design of the multi-cathode SNICS source for the use of both gas and solid samples within a single source. The latest performance of these sources will be discussed. New diagnostics is being developed for very low beam currents. The latest design of the low current beam profile monitor (LCBPM) will also be presented.     

A high resolution AMS-injector for the Pelletron in Lund

A high resolution injector system has recently been installed at the Lund 3 MV tandem Pelletron accelerator. The new injector, designed mainly for ²⁶Al ions, will increase the experimental potential of the Lund AMS facility considerably. High quality energy- and mass-resolution is obtained by using a 90° spherical electrostatic analyzer followed by a 90° magnetic analyzer. The injector is equipped with a high intensity sputtering source with a spherical ionizer. A new analytical technique for acceptance calculations as well as PC-based computational methods have been used in the design of the ion optical system of the new injector. Compared to our old injector system which has a magnetic analyzer with a bending angle of only 15°, the new system has a more than ten times better resolution. The beam optics of the new system is also better designed to match the accelerator acceptance. In this way the ion transmission from the ion source to the detector, for different ions of interest in our AMS programme, has been increased.     

Frontier applications of electrostatic accelerators

Electrostatic accelerator is a powerflfl tool in many research fields, such as nuclear physics, radiation biology, material science a.rchaeology and earth sciences. Two electrostatic accelerators, one is the single stage Vail de Gi＇aaff with terminal voltage of 4.5 MV and another one is tile EN tamteIn with terminal voltage of 6 MV, were installed in 1980s and had been put into operation since the early 1990s at tile Institute of Heavy Ion Physics. Marly applications have been carried out since then. These two accelerators are described and summaries of the most important applications on neutron physics and technology, radiation biology and material science, as well as accelerator mass spectrometry （AMS） are presented.     

一种测量重核素的小型高压型加速器控制系统的研制

为满足中国原子能科学研究院最新研制的400 kV小型重核素加速器质谱（AMS）装置的自动控制的需求,设计并实现了针对该装置的自动控制系统。从硬件和软件两个方面描述了系统结构。虚拟仪器LabWindows/CVI9.0、PLC、数据库、组态软件等的相结合,既组建了友好的人机交互界面,又提高了系统的可靠性。自主设计的具有较高自动化水平的气体剥离器控制,实现了同步监测、控制气体流量和真空度。自动换靶控制的零位指示和靶号显示相配合,更精确地实现换靶功能,提高了装置自动化程度。经长时间测试,该测控系统满足了加速器质谱系统的自动控制及就地操作需求。     

加速器质谱测量182Hf的效率研究

182Hf是长寿命放射性核素,其半衰期约为9×106 a. 测量环境样品中的182Hf对核天体物理学和核工程的研究具有重要的意义. 加速器质谱(AMS)作为一门超高灵敏核分析技术,可以测量样品中极其微量的182 Hf. 本工作在中国原子能科学研究院HI 13串列加速器核物理国家实验室的AMS装置上对182 Hf的AMS效率进行了测量,得到了初步的测量结果.     

Ein Beschleuniger für schwere Ionen

A heavy ion accelerator on the basis of the multiple-stage operation of a small tandem-generator is proposed. The ions will be accelerated in the first half of the tandem in a charge state equilibrated in a foil stripper and then slowed down in the second half of the tandem in a charge state equilibrated in a gas atmosphere where the average charge is much lower than in a solid. One passage through the tandem results in a gain of energy of (Z _solid-Z _gas)·eU MeV. The gain expected for the acceleration of iodine ions will be of the order of 4 MeV for potentials at the high voltage electrode of about 1 MV. The application of many of these systems in line or the application of a magnet system bending the ions many times through the same electric field and stripper will allow to accelerate very heavy ions up to energies of about 1000 MeV. The transmission of this accelerator as a function of scattering, solid angle and final particle energy is estimated.     

Status report on the folded tandem ion accelerator at BARC

The folded tandem ion accelerator (FOTIA) facility set up at BARC has become operational. At present, it is used for elemental analysis studies using the Rutherford backscattering technique. The beams of¹H, ⁷Li, ¹²C, ¹⁶O and ¹⁹F have been accelerated up to terminal voltages of about 3 MV and are available for experiments. The terminal voltage is stable within ±2 kV. In this paper, present status of the FOTIA and future plans are discussed.     

Design of an accelerating tube for electrostatic accelerators

An accelerating tube has been designed and fabricated. Ion optical properties with different input beam geometries for 25 keV protons have been studied. An optimum voltage gradient in the first few sections required to obtain a focussed beam is determined. The tube has been installed in the 2 MV tandem accelerator built at Trombay and the performance of the tube is discussed.     

First experiments and future prospects at the Daresbury On-Line Isotope Separator

The Daresbury On-Line Isotope Separator (DOLIS) has recently been commissioned, in conjunction with the Nuclear Structure Facility (NSF) 20 MV tandem accelerator, and a³He-⁴He dilution refrigerator. First experiments are concentrating on a study of the decay of the neutron deficient iodine isotopes, extracted from a FEBIAD ion source and implanted at 60 keV into an iron host at 15 mK. As well as measuring iodine magnetic moments, the role of proton excitations across the Z=50 shell gap is being investigated in the even-even tellurium daughter nuclei. An on-line laser facility is also being developed, and first measurements have been made for unstable samarium isotopes     

A simple post-accelerator foil stripper assembly for atomic collision experiments

A multiple foil holder for use in ultra high vacuum (UHV) environment as a post accelerator ion stripper has been designed and fabricated. It is used to produce beams of an ion in different charge states at a given energy from a 14 MV pelletron accelerator. These ions are required in several types of atomic collision experiments. The assembly is tested with³²S ions at various energies.     

Folded tandem ion accelerator facility at trombay

The folded tandem ion accelerator (FOTIA) project at BARC has been commissioned. The analysed carbon beams of 40 nA(3⁺) and 25 nA(4⁺), at terminal voltage of 2.5 MV with N₂ + CO₂ as insulating gas, were obtained. The beams were characterized by performing the Rutherford back scattering (RBS) on gold, tin and iron targets. The beam energy of 12.5 MeV for ¹²C⁴⁺ was consistent with the terminal voltage of 2.5 MV. The N₂ + CO₂ mixture is being replaced by SF₆ gas in order to achieve 6 MV on the terminal. In this paper, some of the salient features of the FOTIA and its present status are discussed.     

Low energy repetitive miniature plasma focus device as high deposition rate facility for synthesis of DLC thin films

Diamond-like carbon (DLC) films were deposited on Si (1 0 0) substrate using a low energy (219 J) repetitive (1 Hz) miniature plasma focus device. DLC thin film samples were deposited using 10, 20, 50, 100 and 200 focus shots with hydrogen as filling gas at 0.25 mbar. The deposited samples were analyzed by XRD, Raman Spectroscopy, SEM and XPS. XRD results exhibited the diffraction peaks related to SiO₂, carbon and SiC. Raman studies verified the formation amorphous carbon with D and G peaks. Corresponding variation in the line width (FWHM) of the D and G positions along with change in intensity ratio (I_D/I_G) in DLC films was investigated as a function of number of deposition shots. XPS confirmed the formation sp² (graphite like) and sp³ (diamond like) carbon. The cross-sectional SEM images establish the 220 W repetitive miniature plasma focus device as the high deposition rate facility for DLC with average deposition rate of about 250 nm/min.     

Mechanical design of the recirculating, terminal pumping in the lund pelletron, and experimental experience

A recirculating terminal pumping system has been installed in the 3 MV Pelletron tandem accelerator in Lund. An extremly limited space in the high voltage terminal and the absence of electrical power in the terminal, forced us to provide a unique design for the installation and powering of the new pumps. Details of the technical design, as well as experience of the use of the new system for accelerator mass spectrometry, will be given.     

An upgraded external beam PIXE setup for multielemental analysis of atmospheric aerosol samples

The external beam particle‐induced X‐ray emission (PIXE) setup has been upgraded by introducing a new silicon drift detector with the aim of obtaining better minimum detection limits (MDLs) at the 2 × 1.7 MV Tandetron accelerator of the Beijing Normal University in China. The upgraded external beam PIXE setup is equipped with two silicon drift detectors for PIXE analysis of low and high Z elements. A surface barrier detector for Rutherford backscattering spectrometry monitors beam and helium flow. Two kinds of aerosol filter samples (quartz fiber filters and Teflon filters) were studied. A 200‐μm thick Mylar absorber in front of the medium‐high energy X‐rays detector was adopted, and it got the best MDLs for atmospheric aerosol samples analysis. Multielemental analysis of quartz fiber filter aerosol samples was achieved. For more accurate and better MDLs of low Z elements in PIXE analysis, it is necessary to keep sufficient helium flow behind the thin samples.     

Progress in neutron diagnostics at JET

In the ITER tokamak, diagnosing the plasma neutron emission will be essential to characterise fusion burning process and determine the performance of the machine. JET, currently the world largest tokamak, is the most suitable test bed for development of the fusion-relevant neutron diagnostics due to its plasma parameters and unique tritium operation capability. Current works aim at improving the spatial and spectral characteristics of the neutron measurements at JET, as well as on technological tasks. The present enhancements of neutron diagnostics and data analyses at JET make-together with new fast particle measuring techniques and tritium retention studies-part of the “burning plasma” diagnostic developments towards reactor-grade fusion facilities.     

小型加速器质谱系统研制及分析技术研究

加速器质谱(AMS)是测量长寿命放射性核素灵敏度最高的分析技术,在环境、地质、考古、物理等领域有着广泛应用。近年来,AMS装置的小型化在国际上得到了很大发展。为了研发小型化AMS装置及其分析技术,中国原子能科学研究院分别自主研制了加速电压为0.2 MV的单极型AMS装置和端电压为0.3 MV的串列型AMS装置。基于研制的单极型AMS装置,成功开展了14C的高效传输和本底排除技术研究,实现了14C的高灵敏测定,14C/12C的测量灵敏度达到2×10–15;利用研制的串列型AMS装置,开展了低能量下129I的气体剥离条件、本底排除和探测方法研究,建立了129I的高效传输和高灵敏测量方法,129I/127I的测量灵敏度为1×10–14。这是国内首次研制成功小型AMS装置,为AMS国产化奠定基础。     

In situ observation of cascade damage under heavy ion irradiation

Abstract

Collision cascades initiated from high energy PKAs produce defect clusters in crystalline solids irradiated with fast neutrons or energetic ions. They will affect not only an early stage of microstructural evolution but that at high fluence by changing free defect survival rate. To elucidate fundamental processes of cascade damage evolution, in situ observation of microstructure in FCC metals under heavy ion irradiation has been carried out using a combined facility of a 400 kV accelerator and a 200 kV transmission electron microscope installed in the University of Tokyo, Tokai. Defect clusters produced by individual energetic ions are observed during irradiation to examine subcascade formation, interaction of point-defects from cascade damage and related point-defect processes.     

用20—1020 keV单能质子刻度CR-39固体核径迹探测器

用北京师范大学2×1.7MV串列加速器和400 kV高压倍加器产生的20—1020 keV单能质子束对CR-39固体核径迹探测器进行了刻度.为了保证质子的单能性和固体核径迹探测器上径迹密度不能超过10⁶/cm²的要求,对两台加速器分别采用了不同方法控制质子辐照数量.在串列加速器上采用了狭缝加转盘的方法,在高压倍加器上采用了100 ns单次高压脉冲扫描束流的方法,既保持了质子的单色性,又达到了质子注量小于10⁶/cm²的 关键词： 单能质子 固体核径迹探测器 CR-39     

HI－13串列加速器的改进

本文总结了ＨＩ－１３串列加速器投入运行以来所做的各项改进工作及国产化情况． Imptovements on HI-13 tandem accelerator which have been made since 1986 are summerized. Modifications and home made components for the injector, the vacuum system, the foil stripper system,the laddertron charsing system and beam lines are described.     

PIXE analysis of a painting by Giorgio Vasari

Among ion beam analysis (IBA) techniques, particle induced x‐ray emission (PIXE) is the most widely used in the field of cultural heritage, providing the elemental composition of materials in a non‐invasive and non‐destructive way. This paper reports on the analysis by PIXE performed at one of the external beamlines of the 3 MV Tandetron accelerator of the LABEC laboratory (Istituto Nazionale di Fisica Nucleare (INFN)—Florence) on a wood painting by Giorgio Vasari, belonging to the altar‐piece ‘Pala Albergotti’ (church of Sts Flora and Lucilla, Arezzo). The measurements were taken in the framework of a campaign of scientific investigations, promoted by the Soprintendenza of Arezzo, preliminary to the restoration of the whole altar‐piece. PIXE was used to identify the elemental composition of the original materials and to characterise the alteration layer visible on the surface of the painting. Measurements on the same spot with proton beams of different energies (differential PIXE) also allowed us to get information on the depth distribution of elements and on the structure of layers without the need of picking up samples. Copyright © 2009 John Wiley & Sons, Ltd.