Continuous Ion Beam Research Articles

Plasma source atmospheric pressure ionization detection of liquid injection using an ion trap storage/reflectron time-of-flight mass spectrometer

In this work, the capabilities of an ion trap storage/reflectron time-of-flight mass spectrometer (IT/reTOF-MS) combination have been explored for detection of ions generated by liquid injection into plasma source atmospheric pressure ionization mass spectrometry. It is demonstrated herein that the ion trap provides an effective means of storing externally generated ions from 10 μs to 10 s prior to mass analysis via pulsed dc extraction into the reTOF-MS device. The IT/reTOF storage capabilities provide the potential for nearly 100% duty cycle in converting a continuous ion beam into a pulsed source for TOF

Studies of ion structures by photodissociation

In this paper photodissociation studies of ion structures, published since 1988, are reviewed. As in previous years, structures of different types of ions have been studied by measurement of photodissociation spectra and photon-induced decay curves (Sections 5 and 6). In addition, the recent introduction of external ion sources in ion cyclotron resonance spectrometers has opened up the possibility of measuring (ultraviolet) photofragment mass spectra of large ions. Several groups have investigated the possibilities of this method, which is highly comparable with, but more effective than, collisionally-induced dissociation (Section 4). In recent years only a few results obtained with beam spectrometers have been published. This may change in the near future because of recent proposals to use pulsed beam mass spectrometers in combination with pulsed excimer lasers instead of the continuous ion beams and c.w. lasers used before (Section 3).

Wear resistance of ion-implanted metallic materials

The present work is devoted to the study of the effect of ion implantation on the wear resistance of materials. Steel 3 and copper cylinder specimens were irradiated with 40 keV carbon, zirconium, titanium, niobium, lead, molybdenum and chromium continuous ion beams and a 200 keV pulsed carbon ion beam with fluences of 10 17 ions cm -2 and 10 13 ions cm -2 respectively. The loss of mass during friction of the butt surface against the rotating disk was taken as the measure of wear. For materials irradiated with continuous ion beams the depth of the layer with increased wear resistance was about 80–100 μm, which is two orders of magnitude greater than the depth of penetration of the implanted ions. In the case of ion implantation with a pulsed ion beam for a short period of time, a great amount of heat was generated. The speed of its dissipation into the bulk of a specimen depends on the thermal conductivity of the material, and hardening of the wear-surface layer starts with cooling at some speed.

The design of an atmospheric pressure ionization/time-of-flight mass spectrometer using a beam deflection method

A novel time-of-flight (TOF) mass spectrometer configuration has been designed which can be interfaced to a continuous ion beam source produced by atmospheric pressure ionization. The TOF device uses a beam deflection method to sweep the ion beam past a slit placed near the ionization source in order to generate a start pulse for TOF detection. The beam sweep technique is modeled by computer simulation and optimized for the various experimental parameters. Nonvolatile samples are injected into the TOF device using liquid injection into a glow discharge atmospheric pressure ionization source in helium. A resolution of at least 519 at m/z 311 is obtained, which is limited by the experimental parameters available in our experiment. The mass resolution is computer modeled and it is shown that as the mass increases, the experimental constraints become less important, and the resolution will increase. It is predicted that using the correct experimental conditions and with the addition of an ion reflector that resolution of well over 1000 should be obtained.

Beam voltage manipulation for time-of-flight mass analysis of continuous ion beams

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBeam voltage manipulation for time-of-flight mass analysis of continuous ion beamsKenneth A. Cowen, Christopher J. Frank, and James V. CoeCite this: Anal. Chem. 1991, 63, 10, 990–993Publication Date (Print):May 15, 1991Publication History Published online1 May 2002Published inissue 15 May 1991https://doi.org/10.1021/ac00010a011RIGHTS & PERMISSIONSArticle Views43Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (521 KB) Get e-Alerts Get e-Alerts

Li Overlayer Formation, Oxidation and Sputtering Characteristics of Al-Li Alloys and W/Al-Li Composites for Fusion Applications

The next generation of long pulse fusion devices will impose severe requirements on the properties of plasma-facing materials. In devices such as ITER, a divertor design is being considered, using a divertor plate which would be either tungsten or a low-Z material such as graphite or beryllium. Graphite and beryllium have a relatively high light ion erosion rate. Tungsten has a much lower sputtering rate for light ion impact, but it is subject to runaway self-sputtering. Because of its limited thermal conductivity, it must be used as a relatively thin plate which might be subject to damage during a disruption. Strongly segregating lithium alloys have been proposed as a means of producing a self-sustaining low-Z overlayer which lowers plasma Zeff and resists self-sputtering. Aluminum-lithium alloys are among the better-characterized lithium-bearing alloys, and it has been demonstrated that lithium segregates strongly in aluminum. However, aluminum has a relatively low melting point, and for low lithium concentrations, the lithium diffusion rate is too slow to replenish lithium at the rate at which it is eroded by the incoming plasma. It has been suggested previously that the β phase Al-Li alloy (48–54 at.% Li) should have high enough diffusivity to be able to replenish surface lithium, and that incorporation of the β-phase AlLi in a composite with tungsten would provide improved high temperature strength and melt layer stability, along with significantly better thermal conductivity than pure tungsten. Such a composite has been fabricated, as well as a variation containing titanium as a means of controlling oxidation at grain boundaries. The Li overlayer formation, erosion, and replenishment are characterized for the β-phase LiAl alloy, and W-AlLi and W-Ti-AlLi composites. It is found that Li diffusion is extremely rapid, and the composites form an oxygen-free Li overlayer which is stable under continuous ion beam sputtering.

A low cost ion beam profile monitor

An intercepting multiwire ion beam profile monitor, of thickness 0.9 cm and active area 5 × 5 cm, has been developed for use with the low-intensity deuteron beamline at the Fast Neutron Research Facility (FNRF), Chiang Mai University. It has been used to optimise the transport of a continuous ion beam of current up to 200 μA and kinetic energy up to 140 keV. The monitor enables the determination of the two-dimensional beam profile using closely-spaced samples at 1.5 mm, and the measurement of relative beam current. The design incorporates low material and labour costs, elimination of the need for commercial vacuum feedthroughs, a minimal amount of devoted electronics with no need for preamplifiers, and permits quick insertion of the monitors, wherever needed along the beamline, with minimum disruption to neighbouring elements.

A pulsed alkali-ion gun for time-of-flight secondary ion mass spectrometry

A pulsed alkali-ion gun for use in time-of-flight secondary ion mass spectrometry (TOF-SIMS) has been constructed and tested. The ion pulses are formed by rastering a continuous ion beam from a thermionic emitter source across a 0.13-mm slit. The pulses consist of 100–1000 alkali ions having a full-width-at-half-maximum temporal distribution of less than 2.4 ns and a spot size of approximately 1×2 mm. In addition, the angular beam divergence of this ion gun is less than 0.5°, making it also suitable for TOF ion scattering and direct-recoil spectroscopy. The ion gun has been used to obtain a series of cluster ion spectra which show a mass resolution of about 2000 and a mass range of nearly 9000 amu.

CAMAC Data Taking System for Experiments Using Continuous Ion Beams from a Cyclotron

The CAMAC system, composed of a front-end processor and a super minicomputer, was realized for nuclear physics experiments using continuous ion beams from a cyclotron and was found to be applicable to measurements at a high counting rate of up to 100 kB/s by transferring of the block data between the two processors. The large scaled central computer also became useful for on-line analyses of data obtained at a high rate.

Characteristics of Penning ionization gauge type compact microwave metal ion source

A sputtering ion source utilizing both microwave and Penning ionization gauge (PIG) ionizations for the primary ion beam deposition is described. The size of the source is 60 mm in diameter and 80 mm long. The continuous ion beams of refractory metals (Ta, W, Mo) with the ion currents of 100 to 150 μA are obtained for gas pressure on the order of 10−3 Torr in the plasma production chamber, microwave power under 40 W, and PIG discharge power under 80 W. This source has been operated with two different discharge modes, either glow discharge or arc discharge. Operation of both modes becomes quite stable by introducing microwave power. Metal ion production by glow discharge is more efficient in power consumption than that by arc discharge.

Non-mass analysed ion implantation using microwave ion source

To evaluate the usefulness of high-current non-mass-analysed (NMA) ion implantation using a new microwave ion source, the photovoltaic properties of silicon solar cells were studied. When phosphorus vapour is introduced into the ion source, it provides implant current of more than 10 mA for the 5–15 keV energy range. The fraction of neutral phosphorus particles implanted together with ions is typically less than 10% of the total dose. The conversion efficiency of solar cells fabricated by NMA implantation is about 10% without any anti-reflection coating. Changes in implantation energy do not significantly change the values of these efficiencies. Continuous and stable oxygen ion beams of about 110 mA were obtained at 5.0 kV, which is high enough to apply to material modification in metals, insulators and semiconductors.

Interaction of lead fluoride films with alkali halide substrates

When lead(II) fluoride is vacuum deposited onto vitreous silica, sodium borate glass, crystalline CaF 2 or NaF, the UV absorption spectra indicate no abnormal behaviour. However, when the substrates are crystalline NaCl, KCl or KBr, the spectra suggest interpenetration of ions between substrate and film during deposition, and this is supported by the subsurface distributions of these ions as revealed by sputtered secondary ion mass spectrometry and spectrochemical analysis during continuous ion beam ablation of the specimens. The changes occuring in the anionic environment of the Pb 2+ ions as a result of the interaction during deposition and also as a result of heating are discussed.

The temporal evolution of a potential double layer formed by ion beam reflection in a magnetized plasma

The temporal evolution of a potential double layer in a collisionless plasma is observed. The layer is formed by injecting a pulsed ion beam along converging magnetic field lines into a boundary drawing electron current and by applying a pulsed positive potential to the boundary in the presence of a continuous ion beam injection. The formation and destruction processes are reversible in the former case, whereas they are irreversible in the latter case. Diorect measurements of ion beam reflection estimated from spatial profiles of ion density are made at various times to facilitate the understanding of the temporal evolution of double layer formation.

Extraction of information on a continuous ion beam from beam-induced shot noise

A solution is offered to the problem of estimating a beam parameter from random signals induced by a continuous ion beam on sensing electrodes. Two models for such signals are proposed: one is based on a homogeneous Poisson point process, whereas the second employs the concept of a compound Poisson point process. Maximum likelihood estimators for a beam parameter are derived and some suboptimum estimators are presented as well. The theoretical bound on accuracy of a measurement is given in terms of observation time, signal band width and the signal-to-noise ratio. Some possible applications of the results to the development of novel instruments are also briefly discussed.

Reversal ion source: A new source of negative ion beams

We demonstrate a new type of ion source for producing either pulsed or continuous negative ion beams. The source, dubbed the ‘‘reversal ion source,’’ utilizes an electrostatic ‘‘mirror’’ which reverses trajectories in an electron beam, producing electrons at their turning point having a distribution of velocities centered at zero velocity. A gas which attaches zero-velocity electrons is introduced at this turning point. Negative ions are produced by the attachment or dissociative attachment process. The cross section for this process is extremely large, varying as (electron energy)−1/2, or just the s-wave threshold law. The operation of the source is demonstrated for continuous and pulsed production of Cl− beams by dissociative attachment to CFCl3. Estimates of the current density of this source are given, and applications to the production of ions through higher energy resonances are discussed.

Axial magnetic field extraction-type microwave ion source with a permanent magnet

We have developed a new type of microwave ion source which has an axial magnetic field generated by a permanent magnet. By the combination of the permanent magnet and ferromagnetic materials, a closed magnetic circuit is formed through an ion extraction electrode. This axial magnetic field is utilized both for the high-density plasma production by the electron- cyclotron resonance process and for the high efficient ion extraction by transporting the generated ions along the magnetic force lines. The continuous ion beams of 2–3 mA are delivered from the extraction aperture (2 mm in diameter) when various gases (Ar, N2, CO2), metal vapors (Cs, Rb), and reactive gas (O2) are used. Extremely low impurities are present in the extracted ion beam. An ion beam with low emittance of 10−8 m rad order and high brightness of 1011 A m−2 rad−2 order is obtained. The size of this ion source is 50 mm in diameter and 65 mm in height. The discharge power of the microwave with the frequency of 2.45 GHz is 7 to 30 W. Thus, a high-current microwave ion source with compact structure and low power consumption is realized.

Measurement of ion beam parameters with electrostatic induction electrodes

One source of information concerning ion beam parameters is the electromagnetic field which can be sensed in a non-destructive manner by means of electrostatic induction electrodes. It is shown that the response of an electrode system is a solution of the Laplace equation with boundary conditions specified by the weighting function of the system. Electrode systems as integral devices can provide information on the beam intensity, transverse beam coordinates, and some coefficients associated with the beam profile. A new class of electrode systems based on the Walsh weighting functions is introduced. Methods are studied for computing the response of electrode systems of a circular as well as of a rectangular cross section. A lower bound, known as the Cramer-Rao bound, on the performance of a measuring system using an electrode system is presented. A concept of spatial filtering is discussed and a novel closed-loop scan generator is proposed. Finally, a brief discussion on the applications of electrode systems indicates that the systems meet requirements for non-destructive sensors suitable for automated equipment employing continuous ion beams.

Injection and Storage of Singly Charged Ions and Extension of the Principles of Ion Storage to Highly Charged Low Energy Recoil Ions

On-line experiments on low energy multiply charged ions can be performed with high sensitivity and resolution if the ions of interest are caught in flight and are subsequently accumulated in a finite observation volume. The various aspects of injecting singly and multiply charged ions into harmonic and nonharmonic ion trap devices are discussed. Injection of a continuous ion beam into an active trap was evaluated by numerical integration of the Mathieu equations to determine the finite confinement time of the injected ions. Three different modes of operation of the ion trap, namely, the radio-frequency (RF), the Penning, and the combined RF and Penning modes were considered. On the other hand the phase space method was used for a pulsed ion beam injected into the RF quadrupole ion trap for which the RF quadrupole field was switched on after the ion injection. In this way, a high trapping efficiency is reached for a suitable combination of the chosen initial RF voltage phase angle and the delay time after the ion injection. In addition, the trapped ions are confined indefinitely and energy- and mass-selective storage of the injected ions are also possible. The occurrence of ion motion induced side bands in the spectrum of stored ions and their importance for determining the ion temperature are discussed. Scaling relations are given which relate the results obtained for singly charged ions to the storage properties as they pertain to highly charged ions. Use is made of the unique environment of ion traps to speculate about novel collision and high resolution spectroscopy experiments on highly charged ions.

Ion beam co-ordinate monitor

It is shown that the co-ordinate of a continuous low-energy ion beam can be determined by measuring the angle of inclination of an elliptical pattern observed on an oscilloscope whose deflecting plates are driven directly by two noise-like signals induced by the beam on two electrostatic induction electrodes.

Nucleation, growth and transformation of amorphous and crystalline solids condensing from the gas phase

The condensation of solids was investigated from the initial nucleation stage through continuous film growth, using evaporation and high-energy ion-beam sputtering. At all stages the kinetics of the nucleation process and the structural characteristics of the condensed phase (glassy, polycrystalline and monocrystalline) were defined. Although many condensates were explored, the specific system discussed is germanium condensing on a variety of amorphous and crystalline substrates. The kinetic behavior observed in crystalline deposits was found consistent with the accepted atomistic model for nucleation. This allowed determination of such nucleation parameters as: the activation energies of surface diffusion,Q d and adsorption,Q ad ,the critical nucleus size,n *, and others. Values of such parameters were found to be systematic functions of the kinetic energy and flux of incident particles and of the type and temperature of the substrate. Two flux and temperature dependent structural order transitions were observed in the very initial nucleation stages and found to coincide with corresponding transitions inn *. Correlation was also established between these transitions and two structural transitions occurring during continuous film growth. This was aided by the occurrence of all four transitions in intermediate condensation stages, i.e. prior to coalescence of nucleation clusters into continuous film. All results were very distinctly affected by the vapor state of the adsorbates, implying considerable correlation between condensation on solid surfaces and in a vapor.