Vacuum Arc Ion Source Research Articles

Study on the properties of deuterium ions in a composite cathode vacuum arc discharge

A vacuum arc discharge with a metal-deuteride cathode can generate a supersonic deuterium ion jet, which finds important applications in vacuum arc ion sources. In this study, a 1D3V spherical particle-in-cell direct simulation Monte Carlo cathode spot model with a titanium-deuteride cathode is developed to investigate the ionization and acceleration of deuterium ions from vacuum breakdown to the steady-arc stage. The effects of cathode deuteration concentration on the deuterium ion fraction and kinetic energy are also analyzed. The results show that the released deuterium atoms start to be ionized at around tens of nanometers from the cathode and then become fully ionized at about 0.4μm as the cathode potential drop gradually builds up. The proportion of deuterium ions in the plasma is slightly higher than the proportion of deuterium atoms in the cathode material. Velocity separation of deuterium and titanium ions occurs due to the acceleration of the electric field during the vacuum breakdown stage; however, the predominant ion–ion Coulomb collisions wipe out this separation in the steady-arc stage. Shifting the deuterium atom concentration in the cathode under a constant arc burning voltage produces an approximately equal current density, and increases the velocities of all ion species. A higher ion kinetic energy is gained by reducing the ohmic heating dissipation, facilitated by the lower plasma resistivity under the increased deuterium ion density.

Preliminary study of a compact pulsed deuterium-deuterium neutron generator with a vacuum arc ion source and a linear induction accelerator

The pulsed neutron beam combined with the time-of-flight (TOF) technique has shown great value in many scientific research and application fields. Most of the neutron-based material identification and interrogation systems require an intense pulsed neutron beam. Time resolved prompt gamma neutron activation analysis (T-PGNAA) is an effective analytical method to greatly suppress interference from the other elements or the neutron shields of the detectors. To develop T-PGNAA method in a compact accelerator neutron source, a novel intense pulsed deuterium-deuterium (D-D) neutron generator based on a linear induction accelerator (LIA) was introduced. The generator has four major components: a vacuum arc ion source with deuterated electrode, a diode accelerator structure, a self-biased voltage secondary electron suppressed structure and a deuterated metal target. The present study characterizes the performance of the neutron generator with respect to neutron yield, the ionic current, beam profile, and beam composition as a function of the acceleration voltage at various discharge currents. Monoenergetic neutrons (2.5 MeV) are produced with a yield of ∼104 n/p and a pulse width of ∼100 ns using about 200 kV of induction acceleration voltage at 10−4 Pa vacuum environment. In this study, we will discuss various physical and technical issues related to the components of the neutron generator and the operation and merits of the novel neutron generator.

Production of Multiply Charged Bismuth Ion Beams in a Vacuum Arc Ion Source with a Submicrosecond Pulse Duration

Production of Multiply Charged Bismuth Ion Beams in a Vacuum Arc Ion Source with a Submicrosecond Pulse Duration

Corrosion, mechanical and biological properties of biodegradable WE43 alloy modified by Al ion implantation

A high-energy metal vapor vacuum arc (MEVVA) ion source was used to implant aluminum (Al) ions into the WE43 alloy (Al-WE43) at a dose of 1 × 1016 ions·cm−2, and the structural composition, mechanical properties, corrosion resistance, and biocompatibility of the alloy before and after implantation were systematically studied. The results showed that an Al2O3/Al thin film was formed on the surface of the WE43 alloy after Al ion implantation, and the dense film caused the corrosion current density (Icorr) of the alloy to decrease from 140.2 ± 9.3 to 17.9 ± 6.1 μA⋅cm−2. Nanoindentation experiments revealed that the elastic model (EIT) and nano-hardness (HIT) of the Al-WE43 alloy were significantly improved due to the surface lattice distortion caused by Al ion implantation. A diluted extract of the Al-WE43 alloy showed higher cell activity, anti-hemolysis and anti-coagulation properties than that of the WE43 alloy. In general, the Al-WE43 alloy can be considered as a promising biodegradable metallic material for cardiovascular stent applications.

Magnetohydrodynamic modeling and simulation of a vacuum arc plasma jet with a ring anode under different external magnetic fields

Supersonic plasma has been widely used. A vacuum arc ion source provides one possible method for generating supersonic plasma. An external magnetic field can effectively avoid the wall loss of the plasma in the ion source and improve the ion yield. In this work, a two-dimensional magnetohydrodynamic model is established, considering different components including ions and electrons. With the help of simulation, we explore the physical characteristics of the supersonic vacuum arc plasma formed from a copper disk cathode. The characteristics that we focus on include plasma composition, current density distribution, plasma velocity, and plasma temperature. These characteristics as well as the ion yield are compared when different magnetic fields generated by solenoids near the cathode are applied, as well as when the arc current is different. The results show that, in the absence of an external magnetic field, ions expand freely with the approximate axial velocity and average ion charge state. With the increase of external magnetic flux density, the wall loss of the plasma will decrease, and the axial velocity and average ion charge state will increase, but the magnetic saturation phenomenon exists. The simulation results are consistent with the experimental results.

Numerical study on variable aperture extraction grids of a titanium hydride cathodic vacuum arc ion source

Titanium hydride cathodic vacuum arc ion sources are widely used in particle accelerators, neutron sources, etc. For the application in neutron sources, higher H+/D+ fraction and higher beam uniformity are preferred. In this work, to improve the beam uniformity of a miniature titanium hydride cathodic vacuum arc ion source, a new scheme of variable aperture extraction grids is proposed. A 2D numerical model is developed for the investigation of the variable aperture extraction grids. Numerical results indicate that the extraction grid plays important roles in the titanium hydride cathodic vacuum arc ion source that can improve the stability of ion source. Moreover, simulated results show that the designed variable aperture extraction grids can reduce the beam nonuniformity to less than ±10%, while the beam nonuniformity of the fixed aperture extraction grids are between ±22% and ±37%. Thus, the presented work can provide a potential reference for the improvement of beam uniformity of the vacuum arc ion sources.

A study on surface-temperature measurement by means of a vacuum-arc cathode under different current conditions

Accurate detection and analysis of the cathode surface temperature delivers an important reference value as regards the prediction of electrode life and corrosion degree, a thorough study of the vacuum-breakdown phenomenon, design and application of the vacuum-arc ion source and vacuum switch. In this paper, multispectral true temperature measurement T of the surface temperature field of pulsed vacuum arc cathode materials under different discharge currents is carried out. Firstly, aiming at solving the problem of synchronous imaging measurement of the temperature field across the cathode of pulsed vacuum arc, a multi-wavelength monochromatic image-acquisition optical path is designed, based upon the image acquisition module of a high-speed monochrome camera. Also, multiple monochromatic spectral radiation images of the target are synchronously acquired on the focal plane of the same monochrome camera detector. As a result, the spectral-radiation image information of multiple wavelengths can be obtained in a single exposure time, which greatly shortens the temperature-field image acquisition time. Secondly, based upon the multispectral true-temperature calculation method, high-speed multispectral imaging measurement of the target temperature field is realized. Finally, the two-dimensional true temperature distribution of the cathode temperature field under different current conditions was studied by setting up an experimental platform for measuring the cathode temperature of the vacuum arc under different current conditions.

Spatial distribution characteristics of vacuum arc plasma with occluded deuterium electrode

There are many kinds of ions in vacuum arc discharge plasma, which have different distributions in space. In this paper, a compact magnetic analyzer is developed for studying the spatial distribution of deuterium ions and metal ions in vacuum arc discharge with occluded deuterium electrode. When the arc current is about 100 A, the device can effectively transfer the ion beam with good secondary electron suppression, and can accurately obtain the ion current intensity. The spatial distribution of deuterium ions and titanium ions in the vacuum arc discharge with TiD electrode are measured by this device. The results show that both deuterium ions and Titanium ions are Gaussian distribution in the radial direction, but deuterium ions are evenly distributed, while titanium ions are relatively concentrated near the axis, resulting in the lowest proportion of deuterium ions near the axis. Along the axis, the number of all ions decreases as a natural exponential function, and the relative magnitudes are approximately equal, so the proportion of deuterium ions is almost constant. The results of this study not only help to understand the plasma expansion process of vacuum arc discharge, but also guide the design of vacuum arc ion source with occluded deuterium electrode and its ion extraction.

Beam test of the ion beam facility based on the metal vapor vacuum arc ion source at Korea multi-purpose accelerator complex

Beam test of the ion beam facility based on the metal vapor vacuum arc ion source at Korea multi-purpose accelerator complex

Power Supply System for Vacuum-Arc Ion Source With Millisecond Pulse Length

This article deals with a vacuum-arc ion source, which generates high-intensity beams of metal ions. The power supply system largely determines the ion source parameters such as accelerating voltage, average current, and pulse current densities of the ion beam. This article proposes the power supply system for the vacuum-arc ion source intended for the generation of pulses with the length up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2000~\mu \text{s}$ </tex-math></inline-formula> at an accelerating voltage up to 50 kV. At the frequency of 50 Hz, the average ion current can reach 50 mA due to long pulses. This article considers the main design solutions for the generation of long pulses. A comparison is given to the novel power supply system based on insulated-gate bipolar transistors (IGBTs) and the earlier thyristor power supply.

Ion Beam Generation in a Vacuum Arc Ion Source with a Multicomponent Cathode

Vacuum arc ion sources are widely used for modifying the properties of various surfaces using ion implantation. The use of cathodes consisting of multicomponent compounds in these sources makes it possible to obtain beams of complex compositions, which expands their technological capabilities. An ion beam generated in a vacuum arc ion source with a two-component cathode made of a copper-chromium composite is studied under the conditions of a magnetic field applied to the discharge gap. It is shown that the charge state distribution of copper and chromium ions in the beam depends on their ratio in the cathode material, and the fractions of these ions in the beam correspond to their atomic content in the cathode. It is shown that the ratio of copper and chromium ions in the plasma, and, accordingly, in the ion beam, is independent of the magnetic field and corresponds to their atomic ratio in the cathode.

Synergistic Effects Under Ion-Beam Modification of Metals

The combined effect of ion and laser beams on physical and mechanical properties of metal and alloy surfaces has been studied. The technique of determining the main parameters of polyenergetic ion implantation using a vacuum-arc ion source is proposed and evaluated. It is found that treatment with titanium ions and the subsequent laser thermal hardening increase microhardness of steel 45 and U8 up to 6 times.

LINAC developments for heavy ion operation at GSI and FAIR

The first cavity of a standalone superconducting (sc) continuous wave (cw) heavy ion Linac as a demonstration of the capability of 217 MHz multi gap Crossbar H-mode structures (CH) has been already commissioned at high acceleration gain. The worldwide first beam test with a superconducting multi gap CH-cavity was a milestone of the R&D work of HIM and GSI in collaboration with Goethe University Frankfurt (GUF) in preparation of the sc cw heavy ion Linac project, substituting GSI-UNILAC as a heavy ion high duty factor Linac. Recently the first two of four fully equipped cw-Linac cryomodules are in procurement. To meet the future FAIR science requirements higher beam intensity has to be achieved in the present GSI-accelerator complex. In the last years ion source developments, in particular for the high current Vacuum Arc Ion Sources (VARIS), were concentrated on heavy elements, as Bi and Pb, aiming for stable routine ion source operation at a sufficient rep. rate and high production efficiency. Stripping is a key technology for all heavy ion accelerators. After upgrade of the supersonic N2-gas jet implementation of high current foil stripping, recently a new H2gas cell, using a pulsed gas regime synchronized with arrival of the beam pulse has been developed. An enhanced stripper gas density as well as a simultaneously reduced gas load results in an increased stripping efficiency, while the beam emittance remains the same. A new record beam intensity (11.1 emA) for238U28+beams at 1.4 MeV/u has been achieved, applying the pulsed high density H2-stripper target to a high intensity238U4+beam from the VARIS ion source. Further ion source developments have been accomplished recently providing for sufficient heavy ion beam intensities at the High Current Injector Linac. A machine investigation program has been performed in 2020. The focus was to optimize the entire FAIR injector chain for high intensity heavy ion beam after the successful implementation of different upgrade measures. Besides a dedicated operation mode applying UNILAC, as a heavy ion Linac, at a synchronous phase significantly lower than 30 degrees for high intensity proton beam, could be established. Thus, UNILAC is able to deliver a sufficient proton beam intensity for the FAIR commissioning phase, when the FAIR-proton Linac is not yet available.

Исследование генерации ионных пучков в вакуумном дуговом ионном источнике с многокомпонентным катодом

Исследование генерации ионных пучков в вакуумном дуговом ионном источнике с многокомпонентным катодом

Некоторые особенности модификации поверхности ионными пучками очень большого размера

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 influence of low energy titanium ion beam irradiation on secondary electron emission of metal materials by electron impact

Argon ion beams with energy from hundreds eV to several keV can suppress the secondary electron emission (SEE) on surface of metal materials by changing surface morphology and chemical composition of the materials through surface sputtering. In this work, it was found that the low-energy titanium ion irradiation with an average energy from 40 keV to 100 keV did not apparently change the surface morphology and chemical composition of the metal materials, but still significantly reduced the secondary electron yield (SEY) of the materials. Pulsed titanium ion beams generated by an ion implanter, which is based on metal evaporation vacuum arc (MEVVA) ion source, were adopted to irradiate oxygen-free copper and stainless-steel samples. The fluence of titanium ions was in the range of 1 × 1015 to 1 × 1017 ions/cm2. By comparing the effects of different titanium ion energies and fluence on the roughness, chemical composition, total SEY of the sample surface, and calculating the ion range, sputtering yield, nuclear stopping power and defect distribution of titanium ions in these materials, it is reasonable to believe that the irradiation damage caused by titanium ion implantation increases the probability of trapping of the low-energy secondary electrons (SEs) by defects, leading to better SEE suppressing.

The vacuum arc ion source for indium and tin ions implantation into phase change memory thin films.

One of the most prospective electrical and optical nonvolatile memory types is the phase change memory based on chalcogenide materials, particularly Ge2Sb2Te5. Introduction of dopants is an effective method for the purposeful change of Ge2Sb2Te5 thin film properties. In this work, we used the ion implantation method for the introduction of In and Sn into Ge2Sb2Te5 thin films by a Multipurpose Test Bench (MTB) at the National Research Center "Kurchatov Institute"-Institute for Theoretical and Experimental Physics. For Sn and In ion implantation into Ge2Sb2Te5, the following MTB elements were used: a vacuum arc ion source, an electrostatic focusing system, and a system for current and beam profile measurements. The MTB parameters for Sn and In ion implantation and its effect on the material properties are presented. Implanted Ge2Sb2Te5 thin films were irradiated by femtosecond laser pulses. It was shown that the ion implantation resulted in a decrease in the threshold laser fluence necessary for crystallization compared to the undoped Ge2Sb2Te5.

Study of ion spectra of a vacuum Arc ion source with titanium-nickel alloy hydride cathode

An experimental study of the ion charge state distribution and mass-charge component of vacuum arc discharging with titanium-nickel alloy hydride by the time-of-flight method is carried out. The study shows that the charging states of titanium ion and nickel ion are 1+, 2+, and 3+. Besides, in the early stage of the discharging process (0–30 μs), the proportion of H+ gradually increases with time and reaches a maximum ratio of 57% at 30 μs, the proportion of Tin+ and Nin+ (n = 1,2,3) gradually decreases with time and reaches a minimum ratio of 43% at 30 μs; In the later stage of the discharging process (30 μs-270 μs), the proportion of H+ begins to decrease rapidly and remains unchanged at around 12% during the period spanning from 75 μs to 270 μs; the proportion of Tin+ and Nin+ (n = 1, 2, 3) gradually increases with time and remains around 88% from 75 μs to 270 μs.

Deuterium ion beam formation in a vacuum arc discharge system with a deuterated cathode

The formation of deuterium ion beams in a vacuum arc with a deuterium-saturated zirconium cathode was studied using a MevvaV.Ru vacuum arc ion source. The multi-aperture ion-optical system of the source was replaced by a string ion-optical system to measure and compare the current–voltage characteristics and current density distributions over the beam cross-section obtained with the two systems. The study shows that the string system with a deuterated cathode provides a beam current 1.4–1.5 times higher than the multi-aperture system does, all other things being equal, and that the beam divergence with the string system is also higher. The total pulse current of deuterium ions in the beam ranges to about 1 A.

Boron vacuum-arc ion source with LaB6 cathode.

We describe a pulsed vacuum arc ion source with a lanthanum hexaboride (LaB6) cathode for high-dose selective implantation of 10B and 11B isotope ions. The design and main parameters of the source and its plasma generator are described, and research data are reported on the formation, transport, and magnetic separation of 10B and 11B ions extracted from the erosion plasma of a vacuum arc discharge. Cathode spots are initiated by flashover across an alumina ceramic block of diameter ∼2.5 mm located at the center of the working cathode. The design of the trigger system provides rather uniform cathode erosion, and the cathode dimensions (diameter of 14 mm, length of ∼15 mm) ensure long-term operation of the source. The plasma generator operates at a pulse repetition rate of up to 10 Hz with a discharge current pulse width of 280 µs. At an arc current of 130 A, the source provides an ion beam of a rectangular cross section of 0.6 × 6 cm2 with an energy of 25 keV and amplitude up to 75 mA. A mass analyzer magnet was used for mass-to-charge separation.