第四代ECR(电子回旋共振)离子源高场Nb3Sn磁体1/2长度样机的研制

中国科学院近代物理研究所正在研发第四代ECR(电子回旋共振)离子源FECR(first 4th generation ECR ion source).以20 kW/45 GHz微波加热运行为目标,需要研制Nb3Sn超导磁体以实现对所加热等离子体的有效磁场约束.作为首台采用Nb3Sn超导磁体技术的ECR离子源,FECR的主磁场线圈由4套独立的轴向螺线管线圈与1套径向六极线圈所构成,且均采用单股Nb3Sn线绕制而成,这给线圈的加工、冷体装配、磁体的失超保护等环节带来一系列挑战.为使磁体能在高场、高应力作用下安全稳定运行,项目采用基于铝壳体结构与bladder & key的预紧应力控制技术,完成了一套半尺寸冷体样机的研发.该样机已完成4.2 K低温测试.本项研究的核心关键问题与挑战是如何在复杂的高精度机械装配与高电流强磁场励磁过程中实现对易碎Nb3Sn导线的有效保护.本篇文章中,我们将阐述如何设计、研制、装配及测试工作于复杂磁场与应力环境的高性能Nb3Sn六极磁铁.针对于单个六极线圈的测试,我们设计研发了一种称为\"Mirror\"结构的测试工装.论文中会详细论述基于壳层结构与bladder & key的装配预紧技术在半尺寸样机上的应用效果.同时,论文对在半尺寸样机上观察到的强烈磁通跳跃现象和它对失超探测保护的严峻挑战问题及相关解决或规避方案进行相关论述.     

SECRAL在18GHz频率下产生强流高电荷态离子束的初步结果

A Superconducting ECR ion source with Advanced design in Lanzhou (SECRAL) was successfully built to produce intense beams of highly charged ions for Heavy Ion Research Facility in Lanzhou (HIRFL).The ion source has been optimized to be operated at 28GHz for its maximum performance.The superconducting magnet confinement configuration of the ion source consists of three axial solenoid coils and six sextupole coils with a cold iron structure as field booster and clamping.For 28GHz operation,the magnet assembly can produce peak mirror fields on axis 3.6T at injection,2.2T at extraction and a radial sextupole field of 2.0T at plasma chamber wall.A unique feature of SECRAL is that the three axial solenoid coils are located inside of the sextupole bore in order to reduce the interaction forces between the sextupole coils and the solenoid coils. During the ongoing commissioning phase at 18GHz with a stainless steel chamber,tests with various gases and some metals have been conducted with microwave power less than 3.2kW and it turned out the performance is very promising.Some record ion beam intensities have been produced,for instance,810eμA of O~(7 ),505eμA of Xe~(20 ),306eμA of Xe~(27 ),21eμA of Xe~(34 ),2.4eμA of Xe~(38 ) and so on.To reach better results for highly charged ion beams,further modifications such as an aluminium chamber with better cooling,higher microwave power and a movable extraction system will be done,and also emittance measurements are being prepared.     

Quantitative ARXPS investigation of systems with ultrathin aluminium oxide layers

Angle‐resolved x‐ray photoelectron spectroscopy (ARXPS) is a non‐destructive method to investigate the near‐surface structure of specimens with a flat surface. For interpretation of the electron intensities emitted from different depth regions, model calculations are necessary. Based on an earlier algorithm we have developed a program for ARXPS studies of thin multilayers. In our model calculation the sample structure is treated as consisting of several layers (one to three) on the substrate, whereas the top layer can be incomplete. Emitted electrons are assumed to be attenuated exponentially in the layers. Different atomic volumes, electron attenuation lengths (including consideration of elastic scattering) and assumptions on stoichiometry are taken into account for the particular layers. As an application of our model calculations we present a study of a set of Al samples that were oxidized by different methods, i.e. natural and plasma oxidation (plasma obtained by electron cyclotron resonance). The oxide layers produced by plasma oxidation were protected by a 2 nm thick Co film, before exposing the samples to the air. Additionally, in order to check our results of the ARXPS model calculation, x‐ray reflectometry (XRR) analysis was used. Copyright © 2004 John Wiley & Sons, Ltd.     

电子回旋共振微波等离子体技术及应用

 电子回旋共振微波等离子体技术(ECR-MP)在表面处理、等离子体刻蚀和薄膜制备,尤其是高品质的激光惯性约束聚变薄膜靶的制备中有着重要的应用。综述了ECR-MP的基本原理、反应装置、实验研究、理论研究和应用情况的发展现状,同时分析了其今后可能的发展趋势。     

SECRAL超导磁体系统的结构分析

An advanced superconducting ECR ion source named SECRAL has been constructed at Institute of Modern Physics of Chinese Academy of Sciences,whose superconducting magnet assembly consists of three axial solenoid coils and six sextupole coils with a cold iron structure as field booster and clamp.In order to investigate the structure of sextupole coils and to increase the structural reliabilities of the magnet system, global and local structural analysis have been performed in various operation scenarios.Winding pack and support structure design of magnet system,mechanical calculation and stress analysis are given in this paper. From the analysis results,it has been found that the magnet system is safe in the referential operation scenarios and the configuration of the magnet complies with design requirements of the SECRAL.     

DECRIS-4离子源的初步测试结果

The ECR ion source DECRIS-4 has been designed and constructed at the FLNR JINR to be used as a second injector of heavy multiply charged ions for the U-400 cyclotron.The design of the magnetic structure of the source was based on the idea of the so-called\"magnetic plateau\".The axial magnetic field is formed by three independent solenoids enclosed in separated iron yokes.As a result the superposition of the coils and hexapole magnetic fields creates the enlarged resonance volume.The first experiments showed that the source was able to produce more than 300eμA of Ar~(8 ) when only 100W of microwave power was used. During the last experiment almost 500eμA of Ar~(8 ) was extracted with the same power.In this paper we will present the preliminary results with other gaseous ions,such as oxygen,krypton and xenon.     

第三代和第四代ECR离子源:未来展望

Since the end of’70s the Electron Cyclotron Resonance ion sources(ECRIS)allowed to increase both the energy and intensity of the beams available from different types of accelerators;perspectives for the future are still optimistic.It is commonly agreed that only some ECRIS parameters have been fully exploited, whether some others are still not efficiently used,or not understood.The developments in the last 20 years have followed the so called Standard Model and the availability of higher frequency generators and higher field magnets have permitted relevant increase;the use of Nb_3Sn may extend the range.The availability of new schemes of microwave coupling to plasma is promising,and the focusing of the electromagnetic wave towards the chamber axis may improve the density of warm electron population.The paper will also describe some critical point of the 3~(rd) generation ECRIS(including technological troubles and limits)and the scenario for future 4~(th) generation ECRIS,operating at f=56—75GHz,to be built in 2010s.     

KVI-AECR离子源的现状报告

In this paper the first results of the new ECR source at the KVI are presented.The source has been built following the design of Jyv(?)skyl(?) University,which is based on the AECR-U of LBNL.As the commissioning is going on,it seems that the extraction and analysing systems inherited from the old source are the limiting factors for the performance of the new source.Beam currents achieved with the source are at the moment a factor of 3 lower than the AECR source used at the Jyv(?)skyl(?) University.Further modifications to improve the source performance will be discussed.     

Argonne国家实验室ECR离子源在固体材料离子束流产生方面的研究进展

Development work with solid materials at the Argonne National Laboratory ECR ion sources has been focused on two areas-introduction of materials with low vapour pressures,and increasing the beam intensities of heavy beams(i.e.-lead and uranium).An induction oven,with a demonstrated operating temperature extending to 2000℃,has been utilized to produce a Ti-50 beam with an intensity of 5.5eμA (12 ).In addition,a refinement of the sputter technique has been employed which has resulted in a 42% improvement in lead beam intensities.Details of the induction oven as well as the refined sputter technique will be presented.     

ECR离子源束流发射度的实验研究

利用最新自行研制的电扫描发射度探测系统, 在ECR离子源上进行了一系列关于ECR离子源引出束流发射度的研究. 这套电扫描发射度探测系统安装在中国科学院近代物理研究所(兰州)的LECR3试验平台的束运线上. 试验中, 通过测量相关参数, 研究了磁场、微波、掺气效应及负偏压效应等对引出束流发射度的影响. 利用实验所得的结果与关于ECR等离子体和离子源束流发射度的半经验理论, 分析推导了离子源各可调参数与ECR等离子体的直接关系, 这为分析探索ECR离子源的工作机制提供了一定的参考依据.