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Ion beam surface modification is typically carried out in a laboratory environment where the processing rate is not a big concern. Nevertheless, it is interesting to consider the possibilities that might allow substantial increase (orders of magnitude) in the processing rate, possibly for industrial application. Here we consider two possible approaches to very large scale ion beam surface modification – the use of very broad beam vacuum arc ion sources and the use of ion sources that have been developed to provide intense neutral beams as part of the world controlled fusion research effort. These sources can provide beam intensities in the tens of amperes range, and quasi-dc operation has been demonstrated. A third possibility is scale-up of the Plasma Immersion Ion Implantation approach, and some relevant work has been done along these lines. These approaches to giant ion beam surface modification systems, and the implied parameters and features of such systems, as well as the highly related concern of the necessary accompanying electrical systems, are briefly considered here.

The goal of this study was to determine the critical ion-radiation conditions under which heavy ion beams can induce DNA double-strand breaks. Helium, nitrogen and argon-ion beams in the energy range of 20 eV to 2 keV were used to irradiate naked DNA plasmid pGFP to fluences of 1, 2 and 4 × 1015 ions/cm2. The topological forms of DNA were subsequently analyzed using gel electrophoresis. The DNA forms were changed from the original supercoiled to damaged relaxed and linear forms, depending on the ion mass, energy, fluence and inertia. We found ion energy and fluence thresholds above which direct double-strand breaks can occur. The threshold is discussed in terms of the areal ion-energy density and the cross-section.

Ion implantation provides an important technology for the modification of material surface properties. The vacuum arc ion source is a unique instrument for the generation of intense beams of metal ions as well as gaseous ions, including mixed metal–gas beams with controllable metal:gas ion ratio. Here we describe our exploratory work on the application of vacuum arc ion source-generated ion beams for ion implantation into polymer textile materials for modification of their biological cell compatibility surface properties. We have investigated two specific aspects of cell compatibility: (i) enhancement of the antibacterial characteristics (we chose to use Staphylococcus aureus bacteria) of ion implanted polymer textile fabric, and (ii) the “inverse” concern of enhancement of neural cell growth rate (we chose Rat B-35 neuroblastoma cells) on ion implanted polymer textile. The results of both investigations were positive, with implantation-generated antibacterial efficiency factor up to about 90%, fully comparable to alternative conventional (non-implantation) approaches and with some potentially important advantages over the conventional approach; and with enhancement of neural cell growth rate of up to a factor of 3.5 when grown on suitably implanted polymer textile material.

This paper provides a confirmation of the effectiveness of the recently suggested ab initio approach to the theoretical prediction of phase transformations which may be induced in metallic alloys by metal plasma immersion and ion implantation processing. The approach is based on an assumption that at certain concentrations of the implanted species, the relaxation of the exited electronic state of the implanted structure should be accompanied by the rearrangement of atoms leading to the formation of a new phase. Recently, on the basis of density functional theory calculations of the energetic characteristics of the electronic subsystems of the implanted Mg–Ag system, it was predicted that concentrations of the implanted Ag ions within the range from ∼18 to 23 at% Ag, favor transition to the phase e′-Ag17Mg54. Our transmission electron microscopy observations and electron diffraction analysis of the Mg-based alloy subjected to the implantation of Ag ions at dose of ∼5×1015 ion/cm2 confirmed that the formati...

The authors present here a summary of their investigations of ultrathin films formed by gold nanoclusters embedded in polymethylmethacrylate polymer. The clusters are formed from the self-organization of subplantated gold ions in the polymer. The source of the low energy ion stream used for the subplantation is a unidirectionally drifting gold plasma created by a magnetically filtered vacuum arc plasma gun. The material properties change according to subplantation dose, including nanocluster sizes and agglomeration state and, consequently also the material electrical behavior and optical activity. They have investigated the composite experimentally and by computer simulation in order to better understand the self-organization and the properties of the material. They present here the results of conductivity measurements and percolation behavior, dynamic TRIM simulations, surface plasmon resonance activity, transmission electron microscopy, small angle x-ray scattering, atomic force microscopy, and scanning...

Low-energy ion beam biotechnology has seen rapid development worldwide in recent years. This is an important expansion of studies on ion beam modification of solid materials, vastly different from and more complex than the latter. Among other novelties, we have focused our interest on ion beam bombardment effects on plant and bacterial cell envelopes and tried to understand mechanisms involved in ion beam-induced gene transfer. Through a comprehensive investigation, we have discovered ion beam-induced formation of nanocrater-like structures in the cell envelope, a general phenomenon of ion beam bombardment of cells; these structures may act as pathways for exogenous macromolecule transfer. We have also quantitatively obtained abnormally great penetration depth and sputtering of ions in the cell envelope. All these results are significantly advantageous for ion beam processing of biological cells.

We review some novel developments of the electrostatic plasma lens and some new plasma devices based on the plasma-optical idea of magnetic insulation of electrons and equipotentialization along magnetic field lines. The plasma lens configuration of crossed electric and magnetic fields provides an attractive and simple method in establishing a stable plasma discharge at low pressure and has been used to develop some cost-effective low-maintenance plasma devices for ion cleaning, surface activation, and polishing of substrates prior to film deposition. Recent embodiments of these devices use permanent magnets and possess considerable flexibility with respect to spatial configuration.

A specialized bioengineering ion beam line has recently been completed at Chiang Mai University to meet rapidly growing needs of research and application development in low-energy ion beam biotechnology. This beam line possesses special features: vertical main beam line, low-energy (30 keV) ion beams, double swerve of the beam, a fast pumped target chamber, and an in-situ atomic force microscope (AFM) system chamber. The whole beam line is situated in a bioclean environment, occupying two stories. The quality of the ion beam has been studied. It has proved that this beam line has significantly contributed to our research work on low-energy ion beam biotechnology.

A program in ion beam bioengineering has been established at Chiang Mai University (CMU), Thailand, and ion beam induced transfer of plasmid DNA molecules into bacterial cells (Escherichia coli) has been demonstrated. However, a good understanding of the fundamental physical processes involved is lacking. In parallel work, onion skin cells have been bombarded with Ar+ ions at energy 25 keV and fluence1–2 × 1015 ions/cm2, revealing the formation of microcrater-like structures on the cell wall that could serve as channels for the transfer of large macromolecules into the cell interior. An in-situ atomic force microscope (AFM) system has been designed and installed in the CMU bio-implantation facility as a tool for the observation of these microcraters during ion beam bombardment. Here we describe some of the features of the in-situ AFM and outline some of the related work.

The formation of a new phase of composition Mg 54 Al 28 Ag 18 was observed as a result of plasma immersion ion implantation of Ag into the compound Mg 17 Al 12 . The new structure was characterized using a micro-beam diffraction technique. It was found that the implantation-induced phase transition occurs when the retained dose of the implanted ions is within the range of about 10 15 –10 16 ions/cm 2 . The implanted system has been studied theoretically by means of density-functional electronic structure calculations and a new ab initio approach has been developed to evaluate the specific concentrations of the implanted ions that might cause the phase transition effect in the implanted matrix. The theoretically estimated values of concentrations are in good agreement with experimental observations.

Ion beam bombardment of biological material has been recently applied for gene transfer in both plant and bacterial cells. A consistent physical mechanism for this significant result has not yet been developed. A fundamental question about the mechanism is the possible formation of pathways due to ion bombardment that are responsible for the gene transfer. We have carried out investigations of the effects of low-energy bombardment by both gaseous and metallic ion species of onion skin cells on their surface microstructure. Our experimental results reveal evidence demonstrating that the formation of micro-crater-like structures on the plant cell envelope surface is a general phenomenon consequent to ion bombardment, no matter what ion species, under certain ion beam conditions. The micro-craters are about 0.1–1 μm in size (diameter) and a few tens of nanometers in depth. The micro-crater formation process seems to be unrelated to the chemical composition of and rapid water evaporation from the cell envelope, but is associated with the special microstructure of the cell wall.

The vacuum arc ion source has evolved over the past 20 years into a standard laboratory tool for the production of high current beams of metal ions, and is now used in a number of different embodiments at many laboratories around the world. The primary application of this kind of source has evolved to be ion implantation for material surface modification. Another important use is for injection of high current beams of heavy metal ions into the front ends of particle accelerators, and much excellent work has been carried out in recent years in optimizing the source for reliable accelerator application. The source also provides a valuable tool for the investigation of the fundamental plasma physics of vacuum arc plasma discharges. As the use of the source has grown and diversified, at the same time, the ion source performance and operational characteristics have been improved in a variety of different ways also. Here we review the growth and status of vacuum arc ion sources around the world and summarize some of the applications for which the sources have been used.

Mechanisms responsible for current oscillations at the ion branch of the probe characteristic are investigated experimentally and theoretically. A comparison between experiment and theory shows that the oscillations in a hollow-cathode discharge in a longitudinal magnetic field are most likely related to the onset of helical instability.

A vacuum arc ion source based metal ion implantation facility is built and in operation at TUBITAK (The Scientific and Technical Research Council of Turkey), Izmir, Turkey and a surface modification research and development program is being carried out here. The system is similar to the one in Lawrence Berkeley Laboratory, which was first built and developed by Brown et al. The broad-beam ion source can be repetitively pulsed at rates up to ∼50 pulses per second and the extracted ion beam current can be up to ∼1 A peak or ∼10 mA time averaged. The ion source extraction voltage can be increased up to 110 kV. Additionally, mixed metal and gas ion beams were generated by a magnetic field, which was obtained through a magnet coil located in front of anode plate and by adding gas in the discharge region. This modified system was used to form buried layers of mixed metal–gas species such as Ti+N (on 316 SS and Ti alloy samples) and Zr and W (316 SS and Ti alloy samples, respectively) of which their hardness, coefficient of friction and wear volumes were measured and their RBS results were obtained. The anodic electrochemical tests showed that the corrosion resistance of Ti implanted 304 SS samples was increased with the dose. Micro structures of Ti implanted surfaces of 304 SS samples were examined with SEM before and after the corrosion tests and the results showed that the pittings were formed mostly in the areas where implanted Ti concentration was less. Recently, the system is equipped with TOF for measuring the charge state distribution of ions. R&D work is planned for the purpose of forming tribologically enhanced materials for industrial applications by using ion implantation, PVD coating, plasma nitriding and their combinations. The results showed that the hardness and performance of ion implanted (with various metals and N) PVD coated cutting inserts increased remarkably. The use of ion implantation techniques in modifying the properties of textile and other materials and optimising the performance of textile and other industrial machine parts and tools is also being investigated and some of the results are presented in this work.

We have developed a code STOPPO which can be used to modify the more-widely used ion implantation codes to more accurately predict the mean nuclear and electronic stopping power, preferential sputtering and range of heavy ions in monatomic target materials. In our simulations an effective atomic number and effective atomic mass are introduced into conveniently available analytical stopping cross-sections and a better fitting function for preferential sputtering yield is carefully evaluated for each ion implantation. The accuracy of the code confirmed experimentally by comparison with measured Rutherford backscattering spectrometry (RBS) concentration profiles for 130 keV Zr ions implanted into Be to fluences of 1 × 1017, 2 × 1017 and 4 × 1017 ions/cm2. We find a steady increase in the mean nuclear and electronic stopping powers of the target; the increase in nuclear stopping power is much greater than the increase in electronic stopping power.

Ion bombardment of living cellular material is a novel subfield of ion beam surface modification that is receiving growing attention from the ion beam and biological communities. Although it has been demonstrated that the technique is sound, in that an adequate fraction of the living cells can survive both the vacuum environment and energetic ion bombardment, there remains much uncertainty about the process details. Here we report on our observations of onion skin cells that were subjected to ion implantation, and propose some possible physical models that tend to support the experimental results. The ion beams used were metallic (Mg, Ti, Fe, Ni, Cu), mean ion energy was typically 30 keV, and the implantation fluence was in the range 10 14 –10 16 ions/cm 2 . The cells were viewed using Atomic Force Microscopy, revealing the formation of microcrater-like structures due to ion bombardment. The implantation depth profile was measured with Rutherford backscattering spectrometry and compared to the results of the TRIM, T-DYN and PROFILE computer codes.

Low-energy ion beam bombardment of biological materials for genetic modification purposes has experienced rapid growth in the last decade, particularly for the direct DNA transfer into living organisms including both plants and bacteria. Attempts have been made to understand the mechanisms involved in ion-bombardment-induced direct gene transfer into biological cells. Here we summarize the present status of the application of low-energy ions for genetic modification of living sample materials.

Formation of intermetallic compounds within the Mg matrix as a result of implantation of Ag by plasma immersion ion implantation technology was investigated. Transmission electron-microscopy studies of the implanted samples revealed the appearance of nanoparticles of binary phase Mg-Ag. A model based on the classical mechanisms of propagation of accelerated ions through the metal matrix was suggested for the explanation of the experimental observations. Ab initio calculations of the electronic sub-systems proved to be helpful in providing theoretical prediction of the structural changes, which may be induced in the implanted system.

Summary form only given, as follows. There is a need for an alternative to traditional vacuum ion optic systems for the case of high-current beams, particularly for moderate energy (10-100 keV) heavy ion beam manipulation, when space charge forces are large. The axially-symmetric electrostatic plasma lens provides an attractive and unique alternative. Use of a plasma lens in this way was successful demonstrated by a series of experiments. Here we briefly review the plasma lens fundamentals, peculiarities of focusing heavy ion beams, and summarize some recent developments (experiments, computer simulations, theory). We show that there is a very narrow range of low magnetic field for which the optical properties of the lens improve markedly. This opens up possibilities for creation of a new-generation compact lens based on permanent magnets. The first experimental results obtained at Kiev and Berkeley about the operation of a permanent magnet plasma lens for manipulating wide aperture high-current heavy ion beams will be presented and summarized.

This study investigates the depth of ion penetration in plant cell wall material. Based on the biological structure of the plant cell wall, a physical model is proposed which assumes that the wall is composed of randomly orientated layers of cylindrical microfibrils made from cellulose molecules of C6H12O6. With this model, we have determined numerical factors for ion implantation in the plant cell wall to correct values calculated from conventional ion implantation programs. Using these correction factors, it is possible to apply common ion implantation programs to estimate the ion penetration depth in the cell for bioengineering purposes. These estimates are compared with measured data from experiments and good agreement is achieved.

Recent developments in the field of ion beam bioengineering, for example our own work demonstrating ion beam-induced transfer of exogenous macromolecules into the interior cell region, have underscored the need for a better understanding of the effects of ion bombardment on the cell wall material. We describe here, our investigations of ion beam sputtering of plant cell wall material and ion beam-induced damage to the cell wall. The presently available ion implantation simulation programs are not adequate, and experimental results are not available, either. We have indirectly estimated the surface sputtering yield of plant cell wall composed of C6H12O6-compound by remodeling the cell wall material so as to use partial mass densities and surface binding energies in the available ion implantation programs. For bombardment with a 30-keV Ar-ion beam, the sputtering yield from the cell wall is estimated to be approximately 10 atoms/ion, which is somewhat greater than the value predicted by direct program simulation, but in good agreement with experimental results. We have also performed electron microscopy on the ion-bombarded cell walls. The micrographs show novel microcrater-like structures on the cell wall subsequent to ion bombardment, which could be the ion beam-generated pathways for exogenous macromolecule transfer.

The goal of the work described here was to study ion beam interactions with bacteria and thus develop an understanding of the mechanisms involved in ion bombardment-induced direct gene transfer into bacterial cells. Ar ion beams at an energy of 26 keV and fluences ranging from 5×10 14 to 4×10 15 ions/cm 2 were used to bombard bacterial cells of Escherichia coli strain DH5α. The bacteria were able to survive the low-temperature and low-pressure treatment conditions for at least a few hours. The ion bombardment created novel crater-like structures on the surface of the bacterial cell envelope, as observed by scanning electron microscopy. Four variously sized DNA plasmids carrying the ampicillin resistance gene were transferred and expressed in E. coli cells bombarded with ion fluences of 1×10 15 and 2×10 15 ions/cm 2 . The dependence of the DNA transfer on the plasmid DNA size, ion fluence and incubation time all suggests that the ion beam-induced surface crater-like structures provide the pathway for the mechanism that is responsible for the ion beam-induced DNA transfer.

Characteristics of plasmas formed by repetitively-pulsed electrical discharges in sodium chloride and barium chloride saline solutions are reported. Spectroscopic observations in conjunction with an analysis of the voltage and current behavior of the discharge lead to a model in which the liquid is vaporized and ionized to form a plasma containing excited water fragments H* and OH* as well as ions and neutrals from the salt. For typical conditions under which plasma is formed, the plasma density is estimated to be of order 10/sup 12/ cm/sup -3/ and the electron temperature about 4 eV.

We have investigated the electrostatic charging effects of dielectric substrate materials during plasma immersion ion implantation. The results demonstrate that the time-dependent surface potential (negative) may be reduced in magnitude due to the charging effect of the dielectric surface, leading in turn to a reduction in the energy of the incident ions and a broadening of the implanted ion energy spectrum. The charging effect is greater during the plasma immersion bias pulse rise-time, and the electrostatic potential charging may be as large as 75% of the total applied (pulse) potential. This is due to abundant charge movement both of ions and secondary electrons, and has been confirmed by computer simulation. The plasma sheath capacitance has a small influence on the surface potential, via the bias pulse rise-time. Processing parameters, for example voltage, pulse duration, plasma density, and pulse rise-time, have a critical influence on the charging effects. Short pulse duration, high pulse frequency and low plasma density are beneficial from the viewpoint of maximizing the implantation ion energy.

AISI D3 tool steel was ion implanted with zirconium and the improvement in surface tribological properties investigated. The Zr ion implantation was done using a metal vapor vacuum arc (Mevva) broad-beam ion source, with a mean ion energy of 130 keV and at doses of 3.6×10 16 , 5×10 16 and 1×10 17 ions/cm 2 . Wear, friction and hardness of the implanted samples were measured and compared to the performance of unimplanted steel. The wear resistance was increased by about a factor of two, the friction remained about the same or was possibly increased by a small amount and the near-surface hardness was improved by a factor of five or more by the ion implantation. We also investigated the effect on the Zr implantation profile of the multi-component energy distribution of the ion beam.

For a heavy ion fusion induction linac driver, a source of heavy ions with charge states 1+–3+, ≈0.5 A current beams, ≈20 μs pulse widths and ∼10 Hz repetition rates is required. Thermionic sources have been the workhorse for the Heavy Ion Fusion (HIF) program to date, but suffer from heating problems for large areas and contamination. They are limited to low (contact) ionization potential elements and offer relatively low ion fluxes with a charge state limited to 1+. Gas injection sources suffer from partial ionization and deleterious neutral gas effects. The above shortcomings of the thermionic ion sources can be overcome by a vacuum arc ion source. The vacuum arc ion source is a good candidate for HIF applications. It is capable of providing ions of various elements and different charge states in short and long pulse bursts and high beam current density. Under a Phase-I STTR from DOE, the feasibility of the vacuum arc ion source for the HIF applications was investigated. We have modified an existing vacuum arc ion source at LBNL to produce a gadolinium (A≈158) ion beam with >0.5 A beam current, 120 keV beam energy, ≈6 cm diameter extraction aperture and ≈20 μs pulse width. The average beam current density at the extraction grids was ≈17 mA/cm2. We have measured that >85% Gd ions were in the 3+ charge state, the beam current fluctuation level (rms) was ≈3%, pulse-to-pulse variation of the beam (rms) was about 3%, the uniformity of the beam density over its 6 cm diameter was ⩾98% and the ion longitudinal energy spread was ⩽1%. Additional measurements were made to improve charge state purity by using other materials and employing an axial magnetic field close to the cathode. Yttrium (A≈89), lead (A≈207), and Ba (A≈137) were tested at similar current parameters with Ba delivering nearly a pure charge state with >95% being in 2+ state. The results of the experiments indicate that the vacuum arc ion source is a good candidate for HIF applications.

Mo and S ions were simultaneously implanted into 9Cr18 stainless steel samples. The frictional properties of the implanted samples were assessed using a pin-on-disk tester and the elemental depth profiles were measured by Auger electron spectroscopy. The hardness of the samples was also measured. We find that this dual-element implantation process reduces the coefficient of friction by a factor of 2 and increases the low-friction lifetime by a factor of 4 compared to the 9Cr18 surface with Mo or S implantation alone. This enhancement is related to the synergistic coexistence of the implanted elements at the same place. We have also investigated the process using computer simulation. The simulation results help disclose the characteristics of the modified layer and explain the effects of dual-element ion implantation.

Ion charge state distributions of vacuum arc ion sources are correlated to the arc operating voltage. Recent research has shown that an enhancement of ion charges via an increase of the arc voltage can be achieved utilizing the transient processes that accompany an arc current spike. The idea investigated is to further enhance the ion charge states by multiple current pulses. It is shown that although the ion charge states are enhanced compared to quasi-dc operation, the application of a sequence of pulses does not lead to the desired additional increase in charge states. This can be attributed to the additional plasma production that is caused by higher arc currents: The additional power supplied to the plasma is distributed over a larger number of plasma particles. One can expect that in the limiting case of many current spikes, the ion charges state distribution approaches the one known for arc plasmas at higher discharge current.

For high-dose metal ion implantation, the use of plasma immersion offers the high-rate advantage, but the simultaneous formation of a surface film along with the sub-surface implanted layer is sometimes a detriment. In this work, we describe a metal . plasma immersion approach in which pure and macro-particle free implantation metal andror gas ions , pure deposition without ion implantation, or dynamic metal ion beam assisted deposition and gaseous plasma immersion ion implantation DIBAD metal . and gas plasma immersion can be obtained. We have demonstrated the technique by carrying out Ti and Ta implantation at .

A high-current plasma lens has been used to focus a large area energetic ion beam and thereby to increase the ion current density by a factor of up to 30, providing a convenient, simple and quick way of carrying out high-dose ion implantation. Here we review the characteristics and performance of the plasma lens, and describe demonstration experiments in which broad beams of carbon and cobalt ions (separately), formed from a vacuum arc ion source, were implanted into silicon test substrates. The carbon implantation was done at an ion energy of 30 keV and to a dose of 5×10 17 cm −2 , and the cobalt implantation was done at a mean Co ion energy of 50 keV and to a dose of 2×10 17 cm −2 . The carbon-implanted samples were annealed in an inert atmosphere to produce epitaxial β-SiC, and the cobalt-implanted samples were annealed to produce polycrystalline CoSi 2 . The recrystallization reactions were monitored using X-ray diffraction. The experiments demonstrate that high-current ion beams can be focused by a plasma lens in this way, providing a tool for compressing the ion beam current density by over an order of magnitude. The plasma lens offers a relatively simple ion beam tool for applications calling for high-implanted ion concentrations.

We have carried out some investigations of the mixing of thin metal films into diamond by energetic metal ion bombardment. Free-standing diamond films were made by microwave plasma-assisted CVD, onto which films of Nb or Ta, approximately 100-A thick, were deposited using a filtered vacuum arc plasma technique. The metalized diamond was then bombarded with a Ta and Nb ion-beam, respectively, at an energy of 150 keV and to an applied dose of ∼7×10 16 ions/cm 2 . The Nb and Ta depth profiles were measured by 2 MeV He + Rutherford backscattering spectrometry. Intense intermixing was produced between the original metal overlay, the diamond matrix, and the implanted atoms; and the concentration depth profiles were found to be well-described by the predictions of the TRIM code. Here, we outline the techniques used for diamond synthesis and the preparation of free-standing films, the vacuum arc plasma deposition of Nb and Ta thin films, and the Ta and Nb ion implantations; and we describe our observations of the ion-mixed films formed in this way.

The formation of sub-surface oxide layers by hybrid metal–gas co-implantation into steel and other metals can improve their tribological properties. In this report, we compare the wear and friction performance of previously studied Al + O hybrid implants with that produced by single species oxygen ion (O+) implantation under similar conditions. The substrates were AISI 304L stainless steel discs polished to a final mirror finish using 1 μm diamond paste, and the ion implantation was done using a conventional swept-beam technique at ion energies of 70 or 140 keV and doses of up to 1×10 17 cm−2. The wear and friction behaviour of the implanted and unimplanted material was measured with a pin-on-disc tribometer. Here we describe the experimental procedure and results, and discuss the improvement relative to that achieved with surface layers modified by metal–gas co-implantation.

Vacuum arc or cathodic arc metal plasma sources are attractive and convenient for depositing high-quality thin metal films and metallurgical coatings. It is a common practice to use a curved magnetic filter duct to eliminate macroparticle contamination and to bias the duct wall with a positive voltage to enhance the throughput of the metal plasma. The metal plasma usually consists of several charge states and time-of-flight (TOF) experiments show that the mean charge state of the metal ions decreases with increasing bias and magnetic field applied to the filter duct. We also derive the throughput of ions with different charge states at different bias voltage and magnetic field by the particle-in-cell (PIC) method. The ion trajectory is simulated neglecting the influence of electron charge. Our results show that the simulated mean charge state displays a similar decreasing trend as the bias voltage and magnetic field strength are increased. Phenomena such as reduction of the mean charge state at high magnetic field strength and bias can be explained in terms of standalone multiply charged metal ions under the influences of magnetic and electric forces inside the filter duct.

Ion implantation techniques were used to improve the hardness and wear resistance of sputtered hydrogenated amorphous carbon films and cathodic-arc non-hydrogenated amorphous carbon films. Conventional ion implantation and plasma immersion ion implantation and deposition techniques were used to implant the films with Si, Ti, Hf and W ions of mean energies in the ranges of 28–72 and 3–6 keV, respectively, and doses between 1×1015 and 1×1017 cm−2. Nanohardness measurements demonstrated an increase in the apparent film hardness, depending on the type, kinetic energy, and dose of implanted ions. The effect of the ion dose on the microstructure characteristics of implanted carbon films was studied by Raman spectroscopy. Continuous sliding tests and non-contact profilometry revealed an appreciable increase in the wear resistance of the ion implanted films. Differences in the hardness of implanted films are interpreted in terms of microstructural changes caused by competing mechanisms responsible for film densification, irradiation damage and increase of tetrahedral (sp3) bond configurations. It is shown that, under certain conditions, ion implantation post-processing techniques may significantly improve the nanohardness and sliding wear resistance of amorphous carbon films.

Low energy high-dose Plasma Immersion Ion Implantation, combining both ion and recoil implantation (dynamic ion mixing), was used to enrich thin surface layers of high-performance polymers with an appropriate amount of specially selected reactive metal element such as Al. Both oxygen plasma and fast (E∼2–3 eV) atomic oxygen (FAO) beam have been used as aggressive environments for testing the implanted polymers. The modified materials successfully survived these test environments, including FAO, which is the main danger for carbon-based materials in space, in low Earth orbit. The retained doses of implanted and recoil implanted elements were controlled by RBS. The content, structure and morphology of the modified protective surface layers were examined by XPS and scanning electron microscopy (SEM). It was shown that protective oxide(s)-based surface structures were formed. Implantation and conversion conditions were found for which the appearance and important thermo-optical properties of treated polymer films, such as solar absorptance and thermal emittance, were practically unchanged.

In this paper we report the effects of transmission through a 90/spl deg/ solenoidal magnetic filter on the ion charge state distribution of a vacuum arc plasma as a function of the magnetic field strength and the injection distance between the cathode and filter entrance. The mean ion charge state, measured using the time of flight technique, increased compared with the unfiltered value at low magnetic fields and then steadily decreased as the filter field was increased. At high fields, it was significantly lower than the unfiltered value.

An important technique used for the grading of voltage drop along high voltage ceramic insulators is to provide some surface conduction to bleed off accumulated surface charge. We have used metal ion implantation to modify the surface of high voltage ceramic vacuum insulators to provide a uniform surface resistivity of order 10 10 Ω/square. A vacuum arc ion source based implanter was used to implant Pt at an energy of about 125 keV to a dose of order 10 16 ions/cm 2 into the surface of ceramic rods used to support the ion focusing system of the Columbia

Vacuum arc plasmas with discharge currents of 300 A and duration 250 μs have been produced in strong magnetic fields up to 4 T. Ion charge state distributions have been measured for C, Al, Ag, Ta, Pt, Ho, and Er with a time-of-flight charge-mass-spectrometer. Our previous measurements have been confirmed which show that ion charge states can be considerably enhanced when increasing the magnetic field up to about 1 T. The new measurements address the question of whether or not the additional increase continues at even higher magnetic field strength. It has been found that the increase becomes insignificant for field strengths greater than 1 T. Ion charge state distributions are almost constant for magnetic field strengths between 2 and 4 T. The results are explained by comparing the free expansion length with the freezing length. The most significant changes of charge state distributions are observed when these lengths are similar.

We point out that energetic ion beams can be produced from a plasma-based ion source using a conventional multi-electrode extractor system to form the ion beam, or by using a less conventional approach in which a single grid (wire mesh) is used and the beam is formed across the high voltage sheath formed there. There are requirements on the mesh size with respect to the plasma density (the sheath must be large compared to the mesh dimension) in order for energetic ion beam to be formed. When this condition is not met it is possible for the configuration to behave in a "plasma-immersion mode," and although the system does not then form an energetic ion beam, ion implantation can, under some circumstances, nevertheless be brought about by another coincidental mechanism.

The vacuum arc ion source has evolved into a more or less standard laboratory tool for the production of high-current beams of metal ions, and is now used in a number of different embodiments at many laboratories around the world. Applications include primarily ion implantation for material surface modification research, and good performance has been obtained for the injection of high-current beams of heavy-metal ions, in particular uranium, into particle accelerators. As the use of the source has grown, so also have the operational characteristics been improved in a variety of different ways. Here we review the principles, design, and performance of vacuum arc ion sources., Comment: 19 pages, contribution to the CAS-CERN Accelerator School: Ion Sources, Senec, Slovakia, 29 May - 8 June 2012, edited by R. Bailey, CERN-2013-007

Ion energy of the beam formed by an ion source is proportional to extractor voltage and ion charge state. Increasing the voltage is difficult and costly for extraction voltage over 100 kV. Here we explore the possibility of increasing the charge states of metal ions to facilitate high-energy, broad beam ion implantation at a moderate voltage level. Strategies to enhance the ion charge state include operating in the regimes of high-current vacuum sparks and short pulses. Using a time-of-flight (TOF) technique we have measured charge states as high as 7 + (73 kA vacuum spark discharge) and 4 + (14 kA short pulse arc discharge), both for copper, with the mean ion charge states about 6.0 and 2.5, respectively. Pulsed discharges can conveniently be driven by a modified Marx generator, allowing operation of “Magis” with a single power supply (at ground potential) for both plasma production and ion extraction.

The production of energetic metal ion beams by vacuum arc ion sources is a subfield of ion beam science and technology that has experienced rapid growth and a great deal of research activity in the last decade or so. Interest in this kind of ion source derives from the high current of metal ions that can be produced-these are the defining and key properties of the source, and they open up areas of application that have not previously been readily accessible. We present a concise history of this field of activity. The background, history, and recent research and development are discussed.

The plasma-generating parts of ion sources including their power supplies are usually floated to high potential (ion extraction voltage), thus requiring great insulation efforts and causing high costs for high-energy ion beams. A new concept for pulsed ion sources is presented in which a single power supply is used to simultaneously produce the plasma and high extractor voltage via a modified Marx generator. Proof-of-principle experiments have been performed with high-current spark discharges in vacuum where multiply charged ions are produced with this Marx-generator-based ion source ("Magis"). Using "Magis", it has been demonstrated that pulsed ion beams of very high energies can be obtained with relatively low voltage. For copper, ions of charge states up to 7+ have been found whose energy was 112 keV for a charging voltage of only 10 kV.

Plasma-immersion ion implantation (PIII) is an emerging technology for the surface engineering of semiconductors, metals, and dielectrics. It is inherently a batch-processable technique that lends itself to the implantation of large numbers of parts simultaneously. It thus offers the possibility of introducing ion implantation into manufacturing processes that have not traditionally been feasible using conventional implantation.In PIII the part to be treated is placed in a vacuum chamber in which is generated a plasma containing the ions of the species to be implanted. The plasma based implantation system does not use the extraction and acceleration methods of conventional mass-analyzing implanters. Instead the sample is (usually) repetitively pulsed at high negative voltages (in the 2–300 kV range) to implant the surface with a flux of energetic plasma ions as shown in Figure 1. When the negative bias is applied to a conducting object immersed in a plasma, electrons are repelled from the surrounding region toward the walls of the vacuum chamber, which is usually held at ground potential. Almost all the applied voltage difference occurs across this region, which is generally known as a sheath or cathode fall region. Ions are accelerated across the sheath, producing an ion flux to the entire exposed surface of the work-piece. Because the plasma surrounds the sample and because the ions are accelerated normal to the sample surfaces, implantation occurs over all surfaces, thereby eliminating the need for elaborate target manipulation or masking systems commonly required for beam line implanters. Ions implanted in the work-piece must be replaced by an incoming flow of ions at the sheath boundary, or the sheath will continue to expand into the surrounding plasma.Plasma densities are kept relatively low, usually between 108 and 1011 ions per cm3. Ions must be replenished near the workpiece by either diffusion or ionization since the workpiece (in effect) behaves like an ion pump. Gaseous discharges with thermionic, radio-frequency, or microwave ionization sources have been successfully used.Surface-enhanced materials are obtained through PIII by producing chemical and microstructural changes that lead to altered electrical properties (e.g., semiconductor applications), and low-friction and superhard surfaces that are wear- and corrosion-resistant. When PIII is limited to gaseous implant species, these unique surface properties are obtained primarily through the formation of nitrides, oxides, and carbides. When applied to semiconductor applications PIII can be used to form amorphous and electrically doped layers. Plasma-immersion ion implantation can also be combined with plasma-deposition techniques to produce coatings such as diamondlike carbon (DLC) having enhanced properties. This latter variation of PIII can be operated in a high ionenergy regime so as to do ion mixing and to form highly adherent films, and in an ion-beam-assisted-deposition (IBAD)-like ion-energy regime to produce good film morphology and structure.

We have investigated the charge state distributions of metal ions produced in a high current vacuum arc plasma located in a strong magnetic field. The arc current was varied over the range 200 A to 4 kA and the magnetic field was from zero up to 10 kG. In general, the effect of both high arc current and high magnetic field is to push the distribution to higher charge states-the mean ion charge state is increased and new high charge states are formed. These effects are explained in terms of increased power input (higher plasma temperature) and delayed freezing of the charge state distribution during the plasma expansion process.

We have operated a vacuum arc ion source in such a way as to form beams of purely gaseous ions. The vacuum arc configuration that is conventionally used to produce intense beams of metal ions was altered so as to form gaseous ion beams, with only minimal changes to the external circuitry and no changes internally to the ion source. In our experiments we formed beams from oxygen (O+ and O2+), nitrogen (N+ and N2+), argon (Ar+), and carbon dioxide (C+, CO2+, O+, and O2+) at extraction voltage of 2–50 kV. We used a pulsed mode of operation, with beam pulses ∼50 ms long and repetition rate 10 pulses per second, for a duty cycle of about 50%. Downstream ion beam current as measured by a 5 cm diameter Faraday cup was typically 0.5 mA pulse or about 250 μA time averaged. This time averaged beam current is very similar to that obtained for metal ions when the source is operated in the usual vacuum arc mode. Here we describe the modifications made to the source and the results of our investigations.

We have investigated the dislocation structures formed in the near surface region of ion implanted coarse-grained copper (grain size 460 μm) using transmission electron microscopy. Ti and Zr ions were implanted into copper using a vacuum arc ion source. The ion energy was about 100 keV and the applied (incident) dose was 1 × 10 17 cm −2 . We find that Ti and Zr ion implantations produce a developed dislocation structure in the Cu subsurface layers. The dislocation structure changes form cell-net and cell dislocation structures at shallow depth to individual randomly distributed dislocations at greater depth. The maximum dislocation density in copper is 6.1 × 10 9 cm −2 for Ti and 11.4 × 10 9 cm −2 for Zr. The thickness of the modified copper layer with high dislocation density is up to 20 μm for Ti and 50 μm for Zr. Microhardness measurements vs. depth and dopant concentration profiles are presented. The long range effect is explained in terms of a model of static and dynamic mechanical stresses formed in the implanted surface layer.

Vacuum arc plasma deposition combined with magnetic filtering of the plasma to remove macroparticles is a promising technique for the production of metallic, compound and hard amorphous carbon thin films. High efficiency of the magnetic filter is a crucial parameter for the application of this technique. We report investigations of the influence of different filter designs, magnetic field configurations and electric potentials on the filter efficiency. We analyse the transport mechanisms on which the flow of plasma through the filter is based, and describe and discuss the occurrence of instabilities in magnetic filters. With an optimum filter arrangement we were able to obtain a filter output of 25% of the total number of ions produced by the vacuum arc discharge.

The vacuum arc ion source is unique among the arsenal of ion sources available to the experimenter in its capabilities for producing high current beams of metal ions, thereby providing a tool valuable especially for ion implantation and for accelerator injection applications. The source also provides a convenient approach to the investigation of fundamental vacuum arc phenomena via analysis of the ions formed within the metal plasma. First introduced several decades ago, this kind of ion beam generator is by now a relatively mature and widely used technology. Here we review the basic approach to vacuum arc ion source design, source embodiments that have been made and used around the world, their applications in several fields, and the vacuum arc plasma physics that has been explored using this kind of device as a diagnostic tool.

Plasma immersion ion implantation and deposition is a novel process for surface modification. By combining plasma deposition and ion implantation and using filtered vacuum arc plasmas, thin film formation, direct and recoil ion implantation, and ion‐beam‐assisted intermixing of the film and substrate can be accomplished simultaneously. The implications of this technique in tribology of magnetic recording media have been investigated experimentally. Surfaces of Al2O3‐TiC heads were modified with silver, carbon, and titanium ions at doses of 3×1016 ions/cm2 and mean implantation energies between 2.0 and 4.2 keV. Simulation results indicated that the modified regions exhibited high concentrations of implanted species in the top 2–3 nm, atomically mixed interfaces, and thicknesses between 10 and 25 nm. Surface imaging with an atomic force microscope and nanoindentation testing revealed that the modified heads possessed smoother topographies and increased hardnesses. Contact start‐stop and continuous sliding e...