Studies of an Expanded Plasma Front Duoplasmatron Ion Source

A new and more flexible ion source assembly has been built for continued study of a duoplasmatron with an expanded plasma front and a cylindrical Pierce-electrode extraction geometry. Studies of conditions necessary for the formation of an expanded plane plasma boundary are discussed, and progress toward the achievement of an aberration-free parallel beam of several hundred mA of protons is reviewed. Recent studies suggest that a duoplasmatron with an expanded plasma front and a diverging Pierce-electrode extraction geometry would produce significantly higher aberration-free beam currents than can be obtained with the present cylindrical geometry. The information necessary for the design of lens optics for matching such a source, or any source which produces a diverging aberration-free beam, to an accelerator or plasma containment device is provided in a convenient and comprehensive form by beam characteristic curves which give beam radius and divergence as functions of perveance at some convenient measuring plane close to the extractor for several fixed values of arc current. Data provided by a constant perveance experiment establish practical limits on obtainable beam current at the chosen design points on the characteristic curves.     

A Study of a Duoplasmatron Ion Source with an Expansion Cup

This work describes a study of the Duoplasmatron ion source for the purpose of investigating the conditions necessary to improve its performance. First a general review is made of theoretical considerations involved in the source's plasma mechanism and the geometry of the extraction system. Then the experimental work deals with the arc discharge characteristics as well as the source's performance when the beam is extracted with a simple Pierce extracting electrode. Through an invar anode insert a 70 mA was obtained at 35 kV. The main improvement was then due to beam extraction from an expansion cup which rendered a 300 mA beam at a lower voltage of 18 kV. The use of different anode materials has indicated the influence of magnetic field penetration on plasma focusing within the expansion cup. A beam current reaching 1 ampere was noticed when a non-magnetic anode was used.     

Surface Ionization Ion Sources

Recent achievements with iridium surface ionization ion sources are discussed. These sources can be used to produce ion beams of elements with ionization potentials from 5-1/2 to 6 V, e. g., the IILA metals (Al, Ga, In and Tl), the rare earths, the heavier alkaline earths, and Li, in addition to the usual heavier alkalis. Ion beams of Li, Al, Ga, and In have been produced here. Ionization efficiencies, critical temperatures, current densities, and beam purities as measured by magnetic mass separation are discussed. An ion source design being employed for the IIIA metals is described briefly.     

高电荷态ECR离子源

综述了中国科学院院近代物理研究所近几年来高电荷态ＥＣＲ离子源的最新进展。     

Electron Cyclotron Resonance Multiply Charged Ion Sources

We describe three ion sources working in our laboratory that deliver multiply charged ion beams. All of them are E.C.R. ion sources and are characterized by the fact that the electrons are emitted by the plasma itself and are accelerated to the adequate energy through electron cyclotron resonance (E.C.R.). They can work without interruption during several months in a quasi-continuous regime. (Duty cycle: <.5). Their charge state distributions (C.S.D.) depend on the size and the characteristics of the plasma. For the smallest source the performances are comparable to those of P.I.G. sources. For the biggest source, the C.S.D. tend towards those obtained by EBIS-type sources. Experimental results and guiding ideas concerning these three ion sources are reviewed.     

Review of the JINR Electron Beam Ion Sources

A review of the electron beam sources of highly-stripped ions, developed at the Joint Institute for Nuclear Research during 1967-75, is given. The effective experimental ionization cross sections of positive C, N. Ar, and Xe ions by electron impact are presented. Possible fields of application of electron beam ion sources are indicated.     

Power Supplies for Cold Cathode Penning Discharge Ion Sources

For the generation of heavy ions at high charge states, the cold-cathode Penning discharge ion source requires a power supply capable of both the high potential essential for striking an arc and the high current for sustaining it. A series-regulated power supply developed at Oak Ridge provides up to 6 kV of striking voltage and up to 12 amperes of arc current. The power supply operates in a constant current mode with the arc voltage dependent on the gas pressure in the ion source. With this source in ORIC, the typical operating conditions are 5 to 10 amperes arc current, 600 to 2000 volts arc potential, and 5 to 20 kW power dissipation in the arc. A larger power supply is planned for extending the arc current to about 25 amperes. Various arrangements, including pre-regulators and multiple power supplies, are under consideration to reduce power dissipation in the series regulator tubes.     

Survey of Multicharged Ion Sources Physics and Some Extraction Problems

A review is given of fundamental processes leading to the production of multicharged ions by electron-atom collision : direct electron ejection, Auger process, electron shake-off. Results concerning ionization crosssections by electron impact are discussed. Some approximate methods allowing to a good knowledge of the ionic population in different types of ion sources (hot plasma devices, laser ion source, electron bombardment and discharge sources). At the end, some problems concerning emittance and brightness of heavy multicharged ion sources are examined.     

A Comparison of Heavy Ion Sources Used in Cosmic Ray Simulation Studies of VLSI Circuits

A comparison has been made between the heavy ions from the ALICE cyclotron and Californium-252. The results of SEU cross-section measurements support the use of the CASE system (Californium-252 Assessment of Single-event Effects) to simulate cosmic ray effects in VLSI circuits.     

Simulation,Design, Construction of Duoplasmatron and Diagnostic Neutral Beam System for Alborz Tokamak

Diagnostic Neutral Beam (DNB) has been used for measuring plasma parameters of tokamaks such as ion and electron temperature, safety factor, impurity concentration and etc. Ion source and electrical power supply specification are the main part of DNB. Arc discharge current value is affected by filament current and anode voltage. Beam current changes with arc current signal in our experiment that agree with theoretical relations. Sixty milli-ampere (60 mA) pulse beam current is because of arc current of about 40 A and extraction voltage of about 20 kV. The increase of beam current with arc current has been reported experimentally and effect of arc current on beam current has been investigated for several high extraction voltages. Optimum condition, which means having a telescopic beam (minimum divergence) for specific parameters of duoplasmatron, has been simulated and verified with experimental test. The best extraction voltage for these parameters has been found to be about 16-kV. The ratio of the perpendicular velocity to parallel velocity has been calculated to be about 0.012. It has been shown experimentally with optical emission spectroscopy that increase in arc current and magnetic current increase proton content of beam.     

Negative Ion Confinement in the Multicusp Ion Source

To optimize the negative ion source and generate intense beams of negative ions, understanding of transport properties of both electrons and negative ions is indispensable. Transport process of negative hydrogen ions (H^?) in a multicusp H^? source, has been simulated by three-dimensional Femlab simulation software. Multipolar plasma confinement is known to result in enhanced plasma density, homogeneous plasma of a large volume, and quiescent plasmas. The effect of plasma confinement by applying multi-polar magnetic field was investigated. Results are obtained for ten different configurations of permanent magnet and discussed. Full line cusps are found to give optimum plasma density. Negative ions created on the sidewall hardly can reach the center of the source due to trapping by the multicusp magnetic field. As a result, H^? ions created on the sidewall do not have a significant effect on the H^? current.