Determination of the Radial Potential Profile in the Modified Penning Discharge with a Heavy Ion Beam Probe

A heavy ion beam probe is used to examine the radial electrostatic potential profile in the Modified Penning Discharge. The plasma potential in the discharge violates the usual constraint on the ion beam energy in that the primary probing beam energy undergoes large changes in its energy while passing through the plasma. In order to determine the radial potential profile, the primary beam trajectories are calculated to agree with measured trajectories by parametric variation of a potential model in the trajectory calculating program. This iteration calculation provides a first approximation to the profile. This profile can be used to predict observation of secondary ions, and observation of such ions provides a confirmation and cross check on the potential profile model found by the primary beam.     

Penning Ion Source Discharge Modes for Pulsed and Continuous Power Supplies

Technical Physics - We have analyzed the pressure dependences of the discharge and extracted currents for a Penning ion source (PIS) for continuous and pulsed power supplies. We have investigated...     

Discharge Characteristics of the Penning Plasma Source

The results of investigation of discharge characteristics of the Penning plasma source are presented. Volt-ampere characteristics (VAC), energy distribution, and mass-charge composition of ions emitted from the discharge under different modes of its combustion were measured. The connection between the discharge current bursts and increase in the potential drop (up to 50% of the anode voltage) is established. The measured VACs agree well with the theoretical dependencies. It is shown that the content of atomic hydrogen ions increases from 5 to 10% with an increase in the anode voltage from 1 to 3.5 kV and the power applied in the discharge (from 0.2 to 3 W).     

Ion bunch stacking in a Penning trap after purification in an electrostatic mirror trap

The success of many measurements in analytical mass spectrometry as well as in precision mass determinations for atomic and nuclear physics is handicapped when the ion sources deliver “contaminations”, i.e., unwanted ions of masses similar to those of the ions of interest. In particular, in ion-trapping devices, large amounts of contaminant ions result in significant systematic errors—if the measurements are possible at all. We present a solution for such cases: The ions from a quasi-continuous source are bunched in a linear radio-frequency-quadrupole ion trap, separated by a multi-reflection time-of-flight section followed by a Bradbury–Nielsen gate, and then captured in a Penning trap. Buffer-gas cooling is used to damp the ion motion in the latter, which allows a repeated opening of the Penning trap for a stacking of mass-selected ion bunches. Proof-of-principle demonstrations have been performed with the ISOLTRAP setup at ISOLDE/CERN, both with ¹³³Cs⁺ ions from an off-line ion source and by application to an on-line beam of ¹⁷⁹Lu⁺ ions contaminated with ¹⁶³Dy¹⁶O⁺ ions. In addition, an optimization of the experimental procedure is given, in particular for the number of ion bunches captured as a function of the ions’ lifetimes and the parameters of the experiment .     

Production and investigation of multiply charged metal clusters in a Penning trap

Singly charged gold cluster ions from a laser-vaporization source are transferred into a Penning trap and subjected to electron bombardment. The charged reaction products are analyzed by time-of-flight mass spectrometry after axial ejection from the trap. They include singly charged cluster fragments, multiply charged clusters of the initial size and multiply charged cluster fragments. The multiply charged clusters are selected and further investigated by collision induced dissociation. Two types of reactions can be distinguished: Dissociation into several charged fragments and evaporation of neutrals. Several features of multiply charged clusters relevant for future investigations are reviewed.This work comprises part of the dissertation of J. Ziegler.     

Corpuscular Diagnosis of the Plasma of Penning Ion Sources

The results of the studies of the energy distribution and atomic-molecular composition of the ions emitted from two Penning ion sources are presented. The transitions between different discharge modes, when the operating pressure and voltage on the anode are changed, are investigated. The energy spectra and mass-charge spectra are measured and the dependences of the fraction of atomic ions on the discharge parameters are determined.     

Use of a Glow Discharge in a Magnetic Field for Production of Broad Ion Beams for Technological Applications

The results of investigations of the conditions of existence and ion-emission properties of a plasma of the high-current variety of a low-pressure glow discharge with a hollow cathode in a magnetic field are given. It has been shown that an applied weak magnetic field (10^–3 T) not only reduces the minimum threshold gas pressure, but also makes the radial distribution of the plasma density more uniform (10%). A decrease in statistical straggling of the delay time to breakdown (10² times) and in discharge formative time (10 times) with increasing pulse repetition rate has been revealed to occur as a result of the transition to multielectron discharge initiation. The mass constitution of the discharge and the charge state of ions have been investigated and ways of lowering the content of the basic types of impurities have been determined. The influence of the parameters of the space charge cathode layer on the beam formation by electrostatic ion optics was investigated. The design of a source of gas ions possessing an increased lifetime and high reliability is described. The source is capable of producing an ion beam of cross section 100 cm² with an energy of ions of up to 40 keV at an average current density of up to 1 mA/cm².     

The Electron Cloud Produced by Intense Ion Beam in Penning Trap

When an ion beam pass through the Penning trap an electron cloud is produced.The distributions of the electron density,electron temperature,drift angular velocity of electrons,diffusion flow density of electrons and electric potential in the electron cloud are discussed by means of the fluid equations of the motion of electrons.     

Atom and Ion Temperatures in a Hollow Cathode Discharge

Abstract

The excitation temperatures of atoms and ions /Ar I, Ar II, V I, V II, Cr I, Cr II, Cu I, and Si I/ have been measured in the hollow cathode discharge. The Ar I high energy levels have been found to be overpopulated. The electron density has been estimated. The ionization-excitation mechanism has been discussed.     

A Unidirectional Ion Source Discharge

An asymmetric axial plasma potential gradient would be useful for creating an efficient unidirectional ion source. A weak inhomogeneous axial magnetic field has been employed to enforce such plasma density and potential gradients. An alternative technique has been studied by computational methods and involves a differential vacuum pumping which introduces a strong axial dependence into the electron-gas ionization rate.     

Effect of Discharge Voltage on an Ion Sheath Formed at a Grid in a Multi-Dipole Discharge Plasma

It is experimentally demonstrated that a relatively strong ion-rich sheath formed at a fixed negative bias of the grid can be changed to a rather weak ion sheath （sheath potential weakly retards electrons） only by increasing the discharge voltage in the system. At sufficiently high negative grid bias, an increase of discharge voltage enhances the ion collection current at the grid. An explanation is put forward in support of this experimental observation. A slight density enhancement with a fall in plasma electron temperature is also observed with the increasing negative grid bias.     

Technological Ion Sources Based on a Vacuum Arc Discharge

Technological ion sources of the TITAN type have been developed at the Institute of High Current Electronics, RAS, for the last ten years. These sources generate wide-aperture high-current beams of gas or metal ions and also mixed two-component gas-metal ion beams with a controllable component ratio. This is possible due to two discharge systems combined into one discharge system of the source. Metal ions are obtained with a vacuum arc discharge and gas ions are generated with a constricted hollow-cathode low-pressure arc discharge. This paper describes the principle and peculiarities of operation of the given sources, their design, parameters, and fields of application. A modified version of the Mevva ion source is considered. The design of this version is based on the results of studies conducted using the TITAN source.     

Ion density limitation in a Penning trap due to the combined effect of asymmetry and space charge

The limitation to the density of an ion cloud confined in a Penning trap is not well understood till now. Our experiments show that this limitation results from the combined effect of the trap asymmetry and the space charge. The main features of this effect are described by a simplified calculation.     

Hot Ion Plasma Heating Experiments in SUMMA

Initial empirical results are presented for the hot-ion plasma heating experiments conducted in the new SUMMA (Superconducting Magnetic Mirror Apparatus) at NASA Lewis Research Center. A discharge was formed by applying a radially inward DC electric field near the mirror throats. Data were obtained at midplane magnetic flux densities from 1.0 to 3.5 tesla. Charge-exchange neutral particle energy analyzer data were reduced to ion temperatures using a plasma model that included a Maxwellian energy distribution super-imposed on an azimuthal drift, finite ion orbits, and radial variations in density and electric field. Using this plasma model, the highest ion temperatures computed were 5 keV, 1.2 keV, and 1 keV for He+, H2+, and H+, respectively. These were obtained at a mid-plane magnetic flux density of 1.6 T. Ion temperature was found to scale roughly as (P/B)n, where P/B is the ratio of power input to magnetic flux density and n is about 1 for hydrogen and 2 for helium. Optical spectroscopy line-broadening measurements yielded ion temperatures about 15 percent higher than the charge-exchange neutral particle analyzer results for hydrogen and about 50 percent higher for helium. Spectroscopically obtained electron temperatures ranged from 3 to 30 eV.     

Axial Distribution of the Ion Mass-to-Charge State in a Magnetron Discharge Plasma

Russian Physics Journal - The axial distribution of the ion mass-to-charge state in planar magnetron plasma has been studied. Copper is used as a target material, and argon was used as an operating...     

大功率多磁极会切场离子源的弧放电特性分析

为了在HL-2A上实现3MW的中性束注入,我院自主研制了直径为260ram,高度为240ram的大功率多磁极会切场离子源.目前,它的性能已达到并超过了最初设计指标,放电脉冲为ls时,最大离子流密度为0.44A/cm2;放电脉冲为3s时,等离子体离子流密度0.24A/cin2;等离子体非均匀性都在5%-7%范围之内.目?它是我国国内等离子体密度最高,放电功率最大的长脉冲桶式离子源.本文通过实验数据与理论相结合的方式对弧放电特性进行分析.     

Operation of a planar Penning trap

We demonstrate experimentally the confinement of electrons in a novel planar Penning trap. Measurement of the eigenfrequencies of the trapped electron cloud exhibits similar behaviour as in conventional 3-dimensional penning traps. The trap may be of future use in quantum computing schemes using single cold electrons.     

大功率多磁极会切场离子源的弧放电特性分析

为了在HL-2A上实现3MW的中性束注入, 我院自主研制了直径为260mm, 高度为240mm的大功率多磁极会切场离子源. 目前, 它的性能已达到并超过了最初设计指标, 放电脉冲为1s时, 最大离子流密度为0.44A/cm²; 放电脉冲为3s时, 等离子体离子流密度0.24A/cm²; 等离子体非均匀性都在5%—7%范围之内. 目前, 它是我国国内等离子体密度最高, 放电功率最大的长脉冲桶式离子源. 本文通过实验数据与理论相结合的方式对弧放电特性进行分析.     

Motional frequencies in a planar Penning trap

A Penning trap consisting of concentric ring electrodes on a substrate and a magnetic field perpendicular to the substrate plane has been loaded with electrons. In order to demonstrate the performance of the trap we have measured the motional frequencies of the trapped electrons. Frequencies, line shape and width agree well with simulations. Miniaturization of the device is at hand which opens novel possibilities for application in quantum computing. Contribution presented at the TCP06, Vancouver Island, 2006-09-21     

Propagation and Diagnostic of Ion Acoustic Waves in a Low Pressure Argon Discharge

In a dc argon discharge column of pressure 5 × 10^?4 torr, ion acoustic waves are studied experimentally. Plasma parameters obtained from the phase velocity of waves are compared with the Langmuir probe measurements. The wave diagnostic method yields the electron temperature lower than the probe method by a factor of 3…?5, if the atomic argon ion is assumed as a dominant ion species. The axial profiles of ion drift velocity show the presence of ions flowing toward the anode along the potential drop in flont of it. Also it is found that the surface condition of the cathode sensitively affects the propagation of ion acoustic waves through the changes in discharge parameters.