Development of an electrostatic high-brightness slow positron beam apparatus for positron scattering experiments

A new apparatus for the study of positron scattering on gaseous target is presented. The apparatus uses electrostatic lens elements and a remoderator in a reflection geometry for the brightness enhancement. The system will provide a high quality positron beam with a small diameter and a small angular divergence, even at low energies.     

Design and performance of the pulsed positron beam at Chalmers University of Technology

A slow monoenergetic pulsed positron beam at Chalmers University of Technology has been built. The system consists mainly of chopper, buncher and accelerator. The achieved positron energy range is in range between 230 eV and 15 keV. The FWHM of the beam resolution function is around 700 ps. The beam intensity is around 10³ cps.     

High-intensity variable-energy positron beam for surface and near-surface studies

We report on the construction and performance of a magnetically confined slow positron beam. The beam is designed for surface physics and near-surface disorder studies and it operates in ultrahigh vacuum with a base pressure of 3 nPa. The beam uses a Co-58 source with a backscattering W(110) single crystal moderator. We get 4.7 × 10⁶ slow positrons per second striking the sample using a 300 mCi source corresponding to a fast-to-slow positron conversion efficiency 0.28 ± 0.02%. The energy of the incident positrons can be varied from 1 eV to 35 keV. Some applications concerning positron re-emission and diffusion as well as positronium desorption from a surface state are shown.     

Commissioning of the first KSTAR neutral beam injection system and beam experiments

The neutral beam injection (NBI) system was designed to provide plasma heating and current drive for high performance and long pulse operation of the Korean Superconducting Tokamak Advanced Research (KSTAR) device using two co-current beam injection systems. Each neutral beam injection system was designed to inject three beams using three ion sources and each ion source has been designed to deliver more than 2.0 MW of deuterium neutral beam power for the 100-keV beam energy. Consequently, the final goal of the KSTAR NBI system aims to inject more than 12 MW of deuterium beam power with the two NBI for the long pulse operation of the KSTAR. As an initial step toward the long pulse (～300 s) KSTAR NBI system development, the first neutral beam injection system equipped with one ion source was constructed for the KSTAR 2010 campaign and successfully commissioned. During the KSTAR 2010 campaign, a MW-deuterium neutral beam was successfully injected to the KSTAR plasma with maximum beam energy of 90 keV and the L-H transition was observed with neutral beam heating. In recent 2011 campaign, the beam power of 1.5 MW is injected with the beam energy of 95 keV. With the beam injection, the ion and electron temperatures increased significantly, and increase of the toroidal rotation speed of the plasma was observed as well. This paper describes the design, construction, commissioning results of the first NBI system leading the successful heating experiments carried in the KSTAR 2010 and 2011 campaign and the trial of 300-s long pulse beam extraction.     

A gold and aluminium implanted standard for ion beam experiments

The status of the Rutherford backscattering standards project comprising a dual implant of Au and Al in a vitreous carbon substrate is reported. The absolute Au and Al contents have been measured by Rutherford backscattering independently of the charge Q on the target, or the solid angle Ω, by depositing absolutely calibrated thin uniform evaporated layers over the implanted targets. Photon activation analysis has also been used as an independent check on the implanted contents. High resolution Rutherford backscattering by electrostatic analysis has been used to deduce the range and profile of the implanted species and the effect of reversing the implantation sequence is reported.     

The external beam microprobe facility in Florence: Set-up and performance

An external beam microprobe facility, based on a quadrupole doublet supplied by Oxford Microbeam Ltd, has been installed on a new beamline at the 3 MV single-ended Van de Graaff accelerator in Florence. The goal was to obtain a beam with a spot size on target of 10–20 μm and a current in the order of at least 1 nA, in order to allow PIXE, PIGE and RBS elemental analysis in air or in a helium atmosphere. The beam was extracted from the vacuum lines through a 0.1 μm thick Si₃N₄ window to minimise lateral straggling. The design goals have been successfully achieved; the measurements of the beam spot characteristics in vacuum as well as in air and in helium atmosphere, are here reported.     

The corrosion of AA2037 aluminum alloy in alkaline aqueous solution studied using slow positron beam spectroscopy

Corrosion behavior of AA2037 T8 Al alloy in a1 M Na OH aqueous solution was investigated using slow positron beam, together with microscopy techniques and electrochemical tests. The alloy was homogenized at 510℃ for 2 h and 30 s, respectively, before final peak aging, so that one Sample A had more dispersoids than Sample B after homogenization. It was found that S parameter of the Doppler-broadened annihilation was significantly decreased near the surface in both samples in the alkaline solution. With increasing the dissolution time,Sample A showed a slower decrease rate than Sample B,which might imply that the preexistence of more dispersoids might hinder the corrosion process in Sample A.Scanning electron microscopy and atomic force microscopy observations found that the surfaces of both samples were uniformly thinned due to intense chemical dissolution by the attack of OH-. With increasing the dissolution time,Sample B was corroded more substantially and produced more and larger pits in a short dissolution time than Sample A. Furthermore, polarization curves showed that Sample A had a lower corrosion current and corrosion rate than Sample B, which revealed that the presence of the dispersoids was responsible for the better corrosion resistance in the alloy.     

对束流均匀化扫描装置的性能改进方法

介绍了对束流均匀化扫描装置三角波电流功率源性能的改进，通过对设备电路改进和设备结构的改造，在重离子对作物种子的诱变育种，生物效应研究以及用重离子束注入处理金属，塑料等使其表面变性的实验中，取得了很好的效果。     

A decade of experiments and recent upgrading at the AMS facility in Bucharest

The Bucharest AMS facility has been in operation since 1998. We shortly present the performed experiments, the major upgrade of the AMS facility at NIPNE – Bucharest and the ongoing progress resulting since. We mounted a new ion source, of NEC 40 sample MC-SNCIS type and we reinforced the vacuum on the injector deck. Computer control on all parameters of the injector deck was implemented through a build-in-house electronic set-up. By converting the Tandem accelerator from a belt-driven charging system to a Pelletron and by introducing a modern GVM we have obtained a reduction of the fluctuations of the terminal voltage by at least two orders of magnitude.     

Investigation by slow positron beam of defects in CLAM steel induced by helium and hydrogen implantation

Hydrogen and helium ion beams delivering different doses are used in the ion implantation, at room temperature, of China Low Activation Martensitic (CLAM) steel and the induced defects studied by Doppler broadening of gamma-rays generated in positron annihilation. Defect profiles are analysed in terms of conventional S and W parameters, measures of relative contributions of low and high-momentum electrons in the annihilation peak, as functions of incident positron energies E up to 30 keV. The behaviours of the S-E, W-E and S-W plots under different implantation doses indicate clearly that the induced defect size has obvious variation with depth, taking values that interpolate between surface and bulk values, and depend mainly on helium ion fluences. The S-W plot indicates that two types of defects have formed after ion implantation.     

重离子束辐射生物学效应研究热点及其进展

随着生物学技术的发展,重离子束辐射生物学效应的研究在研究手段和研究对象上都经历着由表型到基因型、定性到定量的转变,逐步深入到分子层次。在分子水平上,生命物质对重离子束辐射具有特定的损伤、修复行为,而相应数学物理模型的构建可实现重离子束辐射生物学效应的定量评估,同时,重离子束辐射诱导旁观者效应的研究对于减轻病灶周围健康组织在重离子放疗中的损伤具有重要意义。     

Lifetime and dimensions of electron (or positron) beam in a storage ring at low current

This article gives the results of experiments on the lifetime and dimensions of the beam for currents at which these quantities are independent of the number of particles. They are studied in relation to energy, voltage on the resonator, etc. Good agreement is obtained between experiment and theory.Translated from Atomnaya Énergiya, Vol. 22, No. 3, pp. 200–203, March, 1967.     

Piping system response induced by thermal-hydraulic transient: A review of recent analysis methods and experiments

Complete thermal-hydraulic and structural dynamic response analysis of piping systems subjected to a thermal hydrodynamic transient, such as a safety/relief valve (S/RV) opening, is a complex multi-step process. The four links of this analysis chain are thermal-hydraulic analysis, mechanical loads calculation, structural dynamics analysis, and transient thermal stress analysis. This paper presents summaries of the individual analysis steps, guidelines for the performance of these analyses, and a review of recent experimental versus analytical prediction comparison studies. Finally, research needs are discussed.     

C—N多晶的离子束合成及分析

介绍了用离子束合成法研制新型材料β－Ｃ３Ｎ４的条件及过程，用ＲＢＳ、ＸＲＤ等手段分析研究该方法生成物的配比、结构和物相，观察到ＣＮ化合物多晶。     

Production of radioactive 9C ion beam and its optimization

1IntroductionCarbonionbeamhasattractedgrowinginterestintumortreatmentinthepastdecade.Thisisattrib-utedtoexcellentphysicalcharacteristicsofcarbonbeamlikedoselocalizationintheBraggpeakandhighrelativebiologicaleffectivenessoverthepeak.Toenhancetheefficacyofheavyionbeamsintreatingtumors,wehaveevenproposedanovelideausingdelayedβ-particledecaybeamssuchas9Cand8Bfortumortreatment.Theseradioactiveionscanisotropi-callyemitlowenergyα-particlesand/orprotonsaftertheir+β-decay.Besideslocalizingionsinbo…