LAPECR2离子源在320kV高压平台上的试运行

The high charge state all permanent Electron Cyclotron Resonance Ion Source(ECRIS)LAPECR2 (Lanzhou All Permanent magnet ECR ion source No.2)has been successfully put on the 320kV HV platform at IMP and also has been connected with the successive LEBT system.This source is the largest and heaviest all permanent magnet ECRIS in the world.The maximum mirror field is 1.28T(without iron plug)and the effective plasma chamber volume is as large as (?)67mm×255mm.It was designed to be operated at 14.5GHz and aimed to produce medium charge state and high charge state gaseous and also metallic ion beams.The source has already successfully delivered some intense gaseous ion beams to successive experimental terminals.This paper will give a brief overview of the basic features of this permanent magnet ECRIS.Then commissioning results of this source on the platform,the design of the extraction system together with the successive LEBT system will be presented.     

兰州全永磁ECR离子源——LAPECR1

The Lanzhou All Permanent magnet ECR ion source NO.1(LAPECR1)is the first all permanent magnet multiple ECRIS made in IMP.This ECRIS is running at 14.5GHz and can provide intense low charge state ion beams(varying from several to hundreds of eμA)or medium charge state ion beams(varying from several to tens of eμA).The size of source body is (?)102mm×296mm,the compactness and economical features enable the source suitable to be put on a HV platform or equipped by a small laboratory.This article gives the main parameters of the ion source.     

不同磁路电子回旋共振离子源引出实验

空间推进所用的电子回旋共振离子源(ECRIS)应具有体积小、效率高的特点. 本文研究的ECRIS使用永磁体环产生磁场, 有效减小了体积, 该离子源利用微波在磁场中加热电子, 电子与中性气体发生电离碰撞产生等离子体. 磁场在微波加热电子的过程中起关键作用, 同时影响离子源内等离子体的约束和输运. 通过比较四种磁路结构离子源的离子电流引出特性来研究磁场对10 cm ECRIS性能的影响. 实验发现: 在使用氩气的条件下, 特定结构的离子源可引出160 mA的离子电流, 最高推进剂利用率达60%, 最小放电损耗为120 W·A^-1; 所有离子源均存在多个工作状态, 工作状态在微波功率、气体流量、引出电压变化时会发生突变. 离子源发生状态突变时的微波功率、气体流量的大小与离子源内磁体的位置有关. 通过比较不同离子源的引出离子束流、放电损耗、气体利用率、工作稳定性的差异, 归纳了磁场结构对此种ECRIS引出特性的影响规律, 分析了其中的机理. 实验结果表明: 保持输入微波功率、气体流量、引出电压不变时, 增大共振区的范围、减小共振区到栅极的距离, 离子源能引出更大的离子电流; 减小共振区到微波功率入口、气体入口的距离能降低维持离子源高状态所需的最小微波功率和最小气体流量, 提高气体利用率, 但会导致放电损耗增大. 研究结果有助于深化对此类离子源工作过程的认识, 为其设计和性能优化提供参考.     

Specific boundary conditions for the simulation of extraction for ECRIS,LIS, and H−-sources

The necessity of a three-dimensional simulation of the extraction has been accepted for electron cyclotron resonance ion sources (ECRIS) as well as for negative ion sources. For an ECRIS, the magnetic hexapole together with the solenoidal mirror field defines a minimum B structure which confines the plasma. Depending on the magnetic flux density distribution, the plasma density in front of the extraction electrode might be non-homogeneous. In H^?-sources, magnetic filter fields are used to separate electrons with different energies or to separate electrons from negative ions. These magnetic filters influence the ions as well. Besides these asymmetry effects other quantities have to be considered, namely the correct formulation of initial conditions of all present charged particles. For ECRIS the initial conditions for ions are assumed to be in the electronvolt range, whereas it can be in the kilo electronvolt range for laser ion sources. Another quantity of interest is the electron energy and the distribution of electrons in real space and their movability if magnetic fields are present.     

LBNL14GHz离子源AECR-U的最新进展

A radial sputter probe has been developed for the AECR-U as an additional method of producing metal ion beams.Negative voltage is applied to the probe to incite collisions with target atoms,thereby sputtering material into the plasma.The sputter probe is positioned through one of the 6 radial access slots between the permanent hexapole structure of the AECR-U.The probe position can be varied with respect to the inner edge of the hexapole magnet structure.Charge state distributions and peak beam intensities at bias voltages up to-5kV were obtained for gold samples at varying distances of the probe with respect to the plasma.For high charge states production the radial position with respect to the plasma was more sensitive than for the medium and lower charge states.For high charge state ion production the probe was optimized at a distance of 0.6cm inside the chamber wall(4.1cm from the center of the chamber).Stable beams with peak intensities of up to 28eμA of Au~(24 ) and 1.42eμA of Au~(41 ) have been produced using the sputter probe technique. In addition,a solid state circuit under development by Scientific Solutions,Inc which provides a bandwidth up to 100MHz was used to drive the 14GHz klystron amplifier for the LBNL AECR-U ion source.Various broadband and discrete heating modes were tested and the results for high charge state ion production were compared with single frequency heating.     

超导ECR离子源DECRIS-SC2

A new compact version of the"liquid He-free"superconducting Electron Cyclotron Resonance Ion Source,to be used as an injector for the U-400M cyclotron,is presently under construction at the FLNR in collaboration with LHE(JINR).The axial magnetic field of the source is created by the superconducting magnet,and the NdFeB hexapole is used for the radial plasma confinement.The microwave frequency of 14GHz will be used for ECR plasma heating.The DECRIS-SC2 superconducting magnet is designed for the induction of a magnetic field on the axis of the source of up to 1.4T(extraction side)and 1.9T(injection side) at nominal current of 75A.Cooling of the coils is carried out by CM cryocooler with cooling power of 1W at the temperature 4.5K.The basic design features of the superconducting magnet and of the ion source are presented.The main parts of the source are in production.The first beam test of the source is expected in the beginning of 2007.     

LECR2离子源的改造及初步运行结果

The Latest developed LECR2M (Lanzhou ECR No.2 Modified)source is the updated one of LECR2(Lanzhou ECR No.2)source at IMP.It has been assembled on the low energy ion beam experimental platform to produce MCI beams for atomic physics and material pllysics experimental research.In our updating program,the structure of injection and extraction components has been modified to make the source structure more simple and effective.The hexapole magnet has also been replaced by a new hexapole magnet with higher radial field and larger inner diameter.With this updating,stronger magnetic field confinement of the ECR plasma is possible and better base vacuum condition is also achieved.LECR2M was designed to be operated at 14.5GHz.During the preliminary test.1.3emA O6 beam was extracted with the injected rf power of 1.1kW.The source has been used to deliver intense MCI beams for different experiments.After some discussion of the main features of this newly updated source,some of the typical commissioning test results of LECR2M will be presented.     

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.     

微波技术对ECR离子源性能的影响

The coupling between microwave generators and ECR ion sources(ECRIS)is a key point for the design of the new generation ECRIS as well as for the optimization of the existing ones.The electromagnetic characterization of the plasma chamber where the ionization phenomena take place is a fundamental starting point to understand and model such process.In such effort the complex structures of the injection and extraction flanges together with the large dimensions of the chamber and the high frequencies that are typically used make impossible an analytical solution and also create great difficulties in the modelling even with state-of- art electromagnetic simulators(CST,HFSS),In the following paper the results of some numerical calculations for the optimum plasma chamber excitation will be presented along with the experimental measurements carried out with the SERSE ion source at INFN-LNS.A campaign of measurements is also planned to further investigate the microwave coupling and the mode excitation,which determines the efficiency of the ECR plasma heating.     

RIKEN超导ECR离子源磁体系统的设计

Superconducting magnet system for a 28GHz ECR ion source has been designed.The maximum axial magnetic fields are 4T at the rf injection side and 2T at the beam extraction side,respectively.The hexapole magnetic field is about 2T on the inner surface of the plasma chamber.The superconducting coils consist of six solenoids and six racetrack windings for a hexapole field.Two kinds of coil arrangements were investigated:one is an arrangement in which the hexpole coil is located in the bore of the solenoids,and another is the reverse of it.The coils use NbTi-Copper conductor and are bath-cooled in liquid helium.The six solenoids are excited with individual power supplies to search for the optimal axial field distribution.The current leads use high Tc material and the cryogenic system is operated in LHe re-condensation mode using small refrigerators.The thermal insulated supports of the cold mass have also been designed based on the calculated results of the magnetic force.The heat loads to 70K and LHe stages were estimated from the design of the supports,the current leads and so on.     

Milliampere He2+ beam generator using a compact GHz ECRIS

Multi-charged helium ion beam He2+ is useful for helium accelerator to obtain a higher energy with lower cost and for deuterium accelerator to avoid neutron activation during machine commissioning.An attempt to generate milliampere multi-charged helium He2+ion beam with a 2.45 GHz electron cyclotron resonance ion source(ECRIS) was tested recently.A design using a specfic permanent magnet 2.45 GHz ECRIS(PMECRIS) source(ERCIS) is reported and the He2+beam production ability is described.With this source,we produced a total helium beam of 40 mA at 40 kV with 180 W of net microwave power and a gas flow of less than 0.5 sccm.At steady state the He2+beam intensity is 4.4 mA,that being the fraction of multi-charged helium ion beam is at approximately 11%.     

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.     

RIKEN 18GHzECR离子源上金属离子的产生

At RIKEN,three ECR ion sources(10GHz ECRIS,18GHz ECRIS and liquid He-free SC-ECRIS) are operated as external ion sources of heavy ion accelerators.In the last year,multi-charged uranium ion beam was produced from 18GHz ECRIS by using UF_6 and the ~(238)U ion was successfully accelerated by the accelerator complex which consists of the RFQ linear accelerator,RIKEN heavy ion linear accelerator(RILAC)and RIKEN ring cyclotron accelerator(RRC).The typical beam intensity of~(238)U~(14 ) was about 2pμA on faraday cup after analysing magnet.~(70)Zn beam was still supplied for the new super-heavy element search experiment with insertion method.Intense beam of~(70)Zn~(16 ) was produced for long term(～43 days)without vacuum break and remarkably low material consumption rate(～100μgr/h).We already supplied Zn beam longer than 200 days for this experiment.~(48)Ca ion was also produced by insertion method using~(48)CaO rod for the nuclear physics experiment.In this contribution,we will present ion source parameter and techniques for production of each of the metal ions.     

对ECR离子源多极磁场结构的改进

Experiments have shown that especially the radial magnetic field component plays a crucial role in the production of highly charged ions with Electron Cyclotron Resonance Ion Sources(ECRIS).However, in several room temperature operating ECRISs the radial magnetic field strength is below the optimum value, mainly due to the limits in permanent magnet technology.Remarkable radial magnetic field improvement can be reached with a relatively simple and cost-effective idea called Modified MultiPole Structure(MMPS).The MMPS differs strongly from the former structures because here the magnetic field is increased only locally without affecting the plasma size.The idea was studied experimentally with a new MMPS plasma chamber prototype,which was designed and constructed for the JYFL 6.4GHz ECRIS.The new chamber is versatile and made it possible to perform several new types of measurements.These showed that the MMPS is especially applicable to increase very high charge-state ion production.Typically the ion current increases more than a factor of 2 in the case of highly charged ions such as Ar~(16 ).     

Magnet design and beam dynamics in computed fields for the DC-350 cyclotron

The DC-350 is an isochronous cyclotron designed in the Flerov Laboratory of Nuclear Reaction (FLNR). It is intended for accelerating ions with a mass-to-charge ratio A/Z within an interval of 5–10 and with an energy of 3–12 MeV/u at the extraction radius. These ion beams will be used in nuclear and applied physics experiments. The paper describes the results of a 3D magnet simulation. The cyclotron magnet and IM90 analiziting-bend magnet of the axial injection channel are studied here. The influence of correction coils on the cyclotron magnet is calculated. All magnet fields were calculated by MERMAID 3D code [1]. The text was submitted by the authors in English.     

Design of a conduction-cooled 4 T superconducting racetrack for a multi-field coupling measurement system

A conduction-cooled superconducting magnet producing a transverse field of 4 T has been designed for a new generation multi-field coupling measurement system,which will be used to study the mechanical behavior of superconducting samples at cryogenic temperatures and intense magnetic fields.A compact cryostat with a two-stage GM cryocooler is designed and manufactured for the superconducting magnet.The magnet is composed of a pair of flat racetrack coils wound by NbTi/Cu superconducting composite wires,a copper and stainless steel combinational former and two Bi_2Sr_2CaCu_2O_v superconducting current leads.The two coils are connected in series and can be powered with a single power supply.In order to support the high stress and attain uniform thermal distribution in the superconducting magnet,a detailed finite element(FE) analysis has been performed.The results indicate that in the operating status the designed magnet system can sufficiently bear the electromagnetic forces and has a uniform temperature distribution.     

The superconducting magnet system with a cryocooler for the ion source Decris-SC

A superconducting magnet system (SMS) for the multicharged ion source DECRIS-SC was designed and manufactured at the Joint Institute for Nuclear Research. Successful tests of the SMS were conducted in late 2003 and early 2004. The peculiarities of this system are stipulated by the use of a cryocooler 1 W in power for the cryostating of the magnet and also by the special configuration of the magnetic field demanded for the source of ions. Four coils ensure the induction of a magnetic field on the axes of the source of up to 3 T (the stopper ratio of ～6), which considerably extends the possibilities of the ion source from the point of view of producing intense highly charged ion beams. The problem of compensating the large forces of interaction between the coils and surrounding iron yoke in this magnet has been successfully solved, and a reliable suspension of the magnet in a cryostat realized. To compound the windings, which work in vacuum at indirect cryostating, prepreg (thermosetting fiberglass fabric impregnated with epoxide) is used. A new technology of superconducting magnet protection has been applied with the help of sectionalized windings, using passive elements of protection based on “cold” diodes and resistances. A new technology of active protection has also been applied, with normal zone detectors and heaters.     

NIRS的ECR离子源现状

Four ECR ion sources have been operated in National Institute of Radiological Sciences(NIRS). Two ECR ion sources supply various ion species for the Heavy Ion Medical Accelerator in Chiba(HIMAC). The 10GHz NIRS-ECR ion source mainly produces C~(2 ) ions for the heavy-ion therapy.Ions of Si,Ar,Fe,Kr and Xe are usually produced by the 18GHz NIRS-HEC ion source for physical and biological experiments.The other two compact ECR ion sources with all permanent magnet configuration have been developed for the new generation carbon therapy facility.One of these,the Kei-source,is a prototype which has been installed to the NIRS-930 cyclotron for axial injection.The other source,Kei2-source,is a demonstration source and utilized for the new generation Linac.In addition,both Kei sources have been used to study fundamental properties. In this paper,present status of the ion sources and recent developments are reported.     

Diode-lasers based apparatus and method for single-mode fibers spectral splice loss measurements

Arc-discharge fusion splicing is widely used in the telecommunication industry for joining single-mode optical fibers to Er-doped fiber coils. These coils are used as the gain medium in erbium-doped amplifiers (EDFAs). The quality and integrity of splicing these coils to fibers can impact key EDFA performance parameters. This article describes an automated splice loss and Er-doped fiber absorption measurement system. The measurement system is equipped with 1310, 1550 and 1563 nm DFB lasers, broadband light source, InGaAs detectors and fiber-optic internal standards. Furthermore, the article describes a method for measuring splice loss between Er-doped fiber and the fibers spliced to coil ends. The system controls splice loss between SM-28 or HI980 fiber and Er-doped fiber to 0.094 ± 0.052 dB at 1550 nm. Moreover, the system can measure accurately Er-doped fiber absorption to within ±3.19% at 1563 nm.