Plasma Ionization Mass Research Articles

Abnormal magnetic field topology in the beam-plasma instability driven by ion dynamics

We report on abnormal topological structures in the particles and electromagnetic field distributions induced by current filamentation instability, with emphasis on the effects of plasma ions. In the plasma filament (PF) situation, the transverse magnetic field reaches its maximum at the edge of the plasma filaments, in contrast to the case of beam filament (BF, i.e., the magnetic field reaches the maximum at the edge of the beam filaments). An analytical model is proposed to estimate the response time of the beam electrons and plasma ions, which is essential to determine the criterion of PF occurrence. With increase in beam energy and density, and decrease in plasma ion mass, the transition from BF to PF can be observed. The results are also confirmed by detailed electromagnetic particle-in-cell simulations. Moreover, the influence of PF on the synchrotron photon emission power is also discussed.

Wide-energy programmable microwave plasma-ionization for high-coverage mass spectrometry analysis

Although numerous ambient ionization mass spectroscopy technologies have been developed over the past 20 years to address diverse analytical circumstances, a single-ion source technique that can handle all analyte types is still lacking. Here, a wide-energy programmable microwave plasma-ionization mass spectrometry (WPMPI-MS) system is presented, through which MS analysis can achieve high coverage of substances with various characteristics by digitally regulating the microwave energy. In addition, ionization energy can be rapidly scanned using programmable waveforms, enabling the simultaneous detection of biomolecules, heavy metals, non-polar molecules, etc., in seconds. WPMPI-MS performs well in analyzing real samples, rapidly analyzing nine toxicological standards in one drop of serum, and demonstrating good quantification and liquid chromatography coupling capability. The WPMPI-MS has also been used to detect soil extracts, solid pharmaceuticals, and landfill leachate, further demonstrating its robust analytical capabilities for real samples. The prospective uses of the technology in biological and chemical analysis are extensive, and it is anticipated to emerge as a viable alternative to commercially available ion sources.

On the rate of energy deposition by an ion ring velocity beam

Using a novel three-dimensional electromagnetic hybrid code, XHYPERS, we simulate the generation of lower hybrid oscillations in a magnetized plasma by a heavy ion beam with a ring-shaped velocity distribution over much longer periods of time compared to previous simulations. We introduce a phenomenological (effective) electron damping to represent the induced scattering of lower-hybrid waves to whistlers and the loss of energy through whistler propagation out of the turbulent region. We demonstrate the effective electron damping to be a crucial factor in increasing the efficiency of energy deposition by an ion ring velocity beam into plasma turbulence and investigate the efficiency of beam energy extraction as a function of the electron damping rate and beam to plasma ion mass ratio.

Possibility of measuring the plasma main ion mass by plasma polarimetry in tokamak similarity experiments

In the context of tokamak diagnostics, and considering a geometry involving line of sights inserted in a poloidal plane, The polarimetry measurements, i.e. the Faraday rotation and Cotton-Mouton ellipticity are very useful because they give quantitative evaluations of the poloidal magnetic field and plasma density respectively. In certain conditions, i.e. in plasma similarity experiments, they can give information on the plasma ion mass and this could be surprising being the polarimetry derived by anisotropy of the index of refraction which is a property related mainly to the electron dynamics. These conditions are verified when similarity experiments are done changing the mass of the main ion. The subject of this paper is the demonstration that indeed the polarimetry measurements depend on the ion mass and this can be detected with the present technology.

Numerical Study of Electron Cyclotron Drift Instability: Application to Hall Thruster

We study the cross-field electron transport in Hall thruster induced by ExB cyclotron drift instability. The investigation tool, consisting of one-dimensional Particle-in-Cell model in the azimuthal drift direction, has been subjected to a convergence study to verify the effects of numerical parameters. The instability evolves keeping the discrete nature of its cyclotron harmonics only for low wavenumbers. A resonance broadening mechanism induced by the electron heating and velocity distribution deformation makes the high-wave numbers disappear in the long non-linear stage. A large wavelength modulation, comparable to the entire azimuthal domain considered is always superimposed. The saturation mechanism is conducted by ions that, due to friction with electrons and trapping in the potential well, heat up and rotate along the electron drift direction. With the best numerical parameters found, the scaling of anomalous mobility with the most important physical quantities (gas and plasma density, magnetic field, accelerating axial electric field and ion mass) has been obtained. Results show that the electron cross-field mobility has a strong dependence from the plasma density and ion mass: for large plasma density, the system undergoes an abrupt change entering in a mode dominated by fluctuation-induced transport, while lighter ions present larger mobility. The scaling of the dominant wavelength detected is compatible with the first harmonic and no transition towards ion acoustic like instability has been observed.

(Invited) Particle Formation Mechanisms in Low Temperature Plasmas

Low temperature plasmas, in particular when they are operated in molecular (organic) gases, are rather complex systems. Their distinct non equilibrium nature, characterized by low neutral gas temperatures (close to room temperature) and relatively high electron temperatures (easily reaching values up to several eV) make them a breeding place for a great variety of different species and depending on the precursor gas and the process conditions even a source for nanoparticles. The formation of nanoparticles has been observed in various discharge types operated in different kinds of gases or gas mixture as e.g.in silane, in fluorocarbons such as CF4 or C2F6 or in hydrocarbons as e.g. acetylene. The formation of nanoparticles in a plasma is either an unwanted side effect, occurring for example during the plasma based deposition of thin films (or the etching of microstructures) or it is the deliberate result of a process used e.g. for the production of nanoparticle deposits. In either way the understanding of the underlying mechanisms which are eventually responsible for the nanoparticle formation in low temperature plasmas is indispensable for the control of the whole process. However, the plasma based formation of nanoparticles is a rather complex procedure, which involves different plasma species, various timescales and several physical and chemical processes. The process starts with the dissociation of the original parent molecule due to electron impact reactions. These reactions are responsible for the initial formation of molecular fragments which can induce subsequent polymerization reactions leading by and by to the formation of larger and larger molecules and eventually to the formation of nanometer sized clusters. These initial protoparticles can further grow due to coagulation and/or accretion processes till they reach a size of some 10 nanometer. Once the particles have reached this size they become rapidly negatively charged and their further growth is mainly governed by the collection of positive ions and neutral radicals. In contrast to CVD processes which are mainly driven by neutral molecules and radicals plasma based processes involve also charged species, namely electrons and different kinds of ions. Depending on the precursor gas used for the given process this ionic component can include positive as well as negative ions. This contribution will focus on the nanoparticle formation in two exemplary systems: discharges operated in argon/acetylene and argon/aniline mixtures. While acetylene plasma are frequently used for the production of DLC films, the use of aniline discharges has been intensively studied for the (conformal) deposition of (ultra) thin polyaniline films or the production of polyaniline nanoparticle deposits. In particular the latter material class possess interesting potential applications in the field of biosensors and for the production of supercapacitors. Based on various in-situ plasma diagnostics (plasma ion mass spectroscopy, in-situ multi-pass FTIR spectroscopy, microvawe interferometry, laser light scattering and optical emission spectroscopy) and different discharge designs the particle formation in both systems is studied aiming to understand the underlying formation mechanisms in order to either promote or prevent the generation of nanoparticles. Special emphasis is paid to the role of the negative ion component. In non-pulsed discharges (low energy) negative ions are trapped in the positive plasma potential inside the plasma bulk and while not contributing to the flux of species reaching the wall of the plasma chamber they can be a dominant species inside the plasma volume. They may play therefore an important role in the initial formation of protoparticles i.e. in the early nucleation phase. Acknowledgments The authors would like to acknowledge the support obtained by the French National Research Agency via the project PlasmaBond. This work has received also funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 730872 (CALYPSO plus for the work at the HZB BESSY II synchrotron, Berlin) and under grant agreement No766894 FETOPEN project PEGASUS.

Relativistic Doppler-boosted \u03b3-rays in High Fields

The relativistic Doppler effect is one of the most famous implications of the principles of special relativity and is intrinsic to moving radiation sources, relativistic optics and many astrophysical phenomena. It occurs in the case of a plasma sail accelerated to relativistic velocities by an external driver, such as an ultra-intense laser pulse. Here we show that the relativistic Doppler effect on the high energy synchrotron photon emission (~10 MeV), strongly depends on two intrinsic properties of the plasma (charge state and ion mass) and the transverse extent of the driver. When the moving plasma becomes relativistically transparent to the driver, we show that the γ-ray emission is Doppler-boosted and the angular emission decreases; optimal for the highest charge-to-mass ratio ion species (i.e. a hydrogen plasma). This provides new fundamental insight into the generation of γ-rays in extreme conditions and informs related experiments using multi-petawatt laser facilities.

Study of the plasma performance of the EFD apparatus for the CSES mission

The Electric Field Detector (EFD) for space ionosphere electric field measurement is described. The EFD is one of the payloads of the China Seismo-Electromagnetic Satellite (CSES) space mission. The EFD measures the variation of the ionosphere electric field due to perturbations from solar, seismic and anthropic phenomena in a wideband from dc up to 3.5 MHz. The EFD will fly on board of the CSES, scheduled to be launched in February 2018. In order to investigate plasma performance of the EFD, the plasma parameters are measured with a Langmuir Probe(LP) and Retarding Potential Analyzers(RPA) in a simulated ionospheric plasma environment. The relevant quantities are obtained as a function of the plasma parameters (i.e. plasma density, electron temperature and ion mass) and system parameters like the orbital velocity, the probe dimensions, the photoelectron current emission and the bias current injected into the probes by the internal constant current source. Here is presented plasma characteristics of the EFD probe. The plasma coupling currents of the EFD probe are calculated analytically. The potential of the EFD probe is measured and calculated analytically.

Role of impurities in modifying isotope scaling law of ion temperature gradient turbulence driven transport in tokamak

Tokamak experiments show that the plasma empirical energy confinement scaling law varies with plasma ion mass (Ai) in a certain range under conditions of different plasma parameters or different devices. In order to understand such a modification of the empirical energy confinement scaling law, the isotope mass dependence of ion temperature gradient (ITG, including impurity modes) turbulence driven transport in the presence of tungsten impurity ions in tokamak plasma is studied by employing the gyrokinetic theory. The effect of heavy (tungsten) impurity ions on ITG and impurity mode is revealed to modify significantly the isotope mass dependence and effective charge effect. As the charge number of impurity ions (Z) or impurity charge concentration (fz) changes, the theoretical scaling law of ITG turbulence transport varies substantially in a relatively large range. The maximum growth rate of ITG mode scales as Mi-0.48 -0.12, whilst that of impurity mode scales as Mi-0.46 -0.3. Here, Mi is the mass number of primary ion in the plasma. In both cases the fitting index with Mi deviates further away from -0.5 when impurity charge concentration fz increases. The isotope mass dependence of ITG turbulence gradually weakens when the effective charge number Zeff increases. The isotope mass dependence of impurity mode turbulence also weakens with Zeff increasing for the same impurity ion charge number (Z). In contrast, the isotope mass dependence gradually strengthens with effective charge number Zeff increasing for the same impurity charge concentration (fz). On average, the maximum growth rates of impurity mode scale roughly as max~Mi-0.35Zeff1.5 and max~Mi-0.4Zeff1, respectively, for Zeff 3 and Zeff 3. The reason for the deviation of isotope scaling law from the normal case is investigated deliberately, and it is demonstrated that the isotope scaling index deviates from -0.5 more or less due to the fact that the impurity species, charge number and impurity concentrations vary in a certain range. These results demonstrate that it is impossible to deduce a unique isotope scaling law due to the variety of micro-instabilities and various plasma parameter regimes in tokamak plasma, which is consistent with the experimental observations. These results may contribute to the transport study involving heavy (tungsten) impurity ions in ITER discharge scenario investigation.

Nanoparticle formation in a low pressure argon/aniline RF plasma

The formation of nanoparticles in low temperature plasmas is of high importance for different fields: from astrophysics to microelectronics. The plasma based synthesis of nanoparticles is a complex multi-scale process that involves a great variety of different species and comprises timescales ranging from milliseconds to several minutes. This contribution focuses on the synthesis of nanoparticles in a low temperature, low pressure capacitively coupled plasma containing mixtures of argon and aniline. Aniline is commonly used for the production of polyaniline, a material that belongs to the family of conductive polymers, which has attracted increasing interest in the last few years due to the large number of potential applications. The nanoparticles which are formed in the plasma volume and levitate there due to the collection of negative charges are investigated in this contribution by means of in-situ FTIR spectroscopy. In addition, the plasma is analyzed by means of plasma (ion) mass spectroscopy. The experiments reveal the possibility to synthesize nanoparticles both in continuous wave and in pulsed discharges. The formation of particles in the plasma volume can be suppressed by pulsing the plasma in a specific frequency range. The in-situ FTIR analysis also reveals the influence of the argon plasma on the characteristics of the nanoparticles.

Time resolved measurements of hydrogen ion energy distributions in a pulsed 2.45 GHz microwave plasma

A plasma diagnostic study of the Ion Energy Distribution Functions (IEDFs) of H+, H2+, and H3+ ions in a 2.45 GHz hydrogen plasma reactor called TIPS is presented. The measurements are conducted by using a Plasma Ion Mass Spectrometer with an energy sector and a quadrupole detector from HIDEN Analytical Limited in order to select an ion species and to measure its energy distribution. The reactor is operated in the pulsed mode at 100 Hz with a duty cycle of 10% (1 ms pulse width). The IEDFs of H+, H2+, and H3+ are obtained each 5 μs with 1 μs time resolution throughout the entire pulse. The temporal evolution of the plasma potential and ion temperature of H+ is derived from the data. It is shown that the plasma potential is within the range of 15–20 V, while the ion temperature reaches values of 0.25–1 eV during the pulse and exhibits a fast transient peak when the microwave radiation is switched off. Finally, the ion temperatures are used to predict the transverse thermal emittance of a proton beam extracted from 2.45 GHz microwave discharges.

SiNx Coatings Deposited by Reactive High Power Impulse Magnetron Sputtering: Process Parameters Influencing the Nitrogen Content.

Reactive high power impulse magnetron sputtering (rHiPIMS) was used to deposit silicon nitride (SiNx) coatings for biomedical applications. The SiNx growth and plasma characterization were conducted in an industrial coater, using Si targets and N2 as reactive gas. The effects of different N2-to-Ar flow ratios between 0 and 0.3, pulse frequencies, target power settings, and substrate temperatures on the discharge and the N content of SiNx coatings were investigated. Plasma ion mass spectrometry shows high amounts of ionized isotopes during the initial part of the pulse for discharges with low N2-to-Ar flow ratios of <0.16, while signals from ionized molecules rise with the N2-to-Ar flow ratio at the pulse end and during pulse-off times. Langmuir probe measurements show electron temperatures of 2-3 eV for nonreactive discharges and 5.0-6.6 eV for discharges in transition mode. The SiNx coatings were characterized with respect to their composition, chemical bond structure, density, and mechanical properties by X-ray photoelectron spectroscopy, X-ray reflectivity, X-ray diffraction, and nanoindentation, respectively. The SiNx deposition processes and coating properties are mainly influenced by the N2-to-Ar flow ratio and thus by the N content in the SiNx films and to a lower extent by the HiPIMS frequencies and power settings as well as substrate temperatures. Increasing N2-to-Ar flow ratios lead to decreasing growth rates, while the N content, coating densities, residual stresses, and the hardness increase. These experimental findings were corroborated by density functional theory calculations of precursor species present during rHiPIMS.

Estimation of magnetospheric plasma ion composition for 1956–1975 by using high time resolution geomagnetic field data created from analog magnetograms

AbstractThis study addresses the ion composition in the magnetosphere before the satellite era. We estimate the plasma ion mass for 1956–1975 from the period of low‐latitude Pi2 pulsations found in digital geomagnetic field data that are created from analog magnetograms at Kakioka. The period of investigation covers most of solar cycle 19 and the whole solar cycle 20. To consider long‐term variation, the moving average of the estimated plasma ion mass is calculated with a 1 year time window. We find that 1 year moving average of the plasma ion mass changed by a factor of ∼2 during one solar cycle (i.e., between ∼1.1 amu and ∼2.4 amu for solar cycle 19 and between ∼1.1 amu and ∼2.0 amu for solar cycle 20). The correlation coefficient between the 1 year moving average of the plasma ion mass and that of the F10.7 index is 0.86. This result supports the idea that in long‐term variation, solar radiation increases the density and the temperature of O+ ions in the ionosphere, leads to the outflow of O+ ions, and contributes to the enhancement of the plasma ion mass in the nightside magnetosphere. The digital data created from analog magnetograms provide an important clue to know the space environment in old days and are advantageous for studies of the space weather and space climate.

Solidification paths in the iron-rich part of the Fe–Ti–B ternary system

Iron-rich alloys in the Fe–Ti–B system are being studied for their potential as a new generation of lightened steel-matrix composites reinforced by titanium diborides. In this work, the iron-rich corner of the Fe–Ti–B ternary system was investigated at temperatures between 1150 °C and 1400 °C. For this purpose, fourteen key alloys containing up to 5 mass % Ti and B were selected on the basis of preliminary thermodynamic calculations and processed in an induction furnace by melting the starting materials at 1630 °C for 1 h. Two types of experiments were performed: (i) long-duration annealing experiments, involving a liquid phase, performed by the electromagnetic phase separation technique at temperatures between 1175 °C and 1250 °C and (ii) differential thermal analysis of samples during heating up to 1400 °C and cooling with different cooling and heating rates (2, 5 and 10 °C min−1).Samples were characterized by X-ray diffraction, scanning electron microscopy, field electron gun scanning electron microscopy and complementary chemical analysis, combining electron microprobe analysis, inductively coupled plasma and secondary ion mass spectrometry, were performed. On the basis of an analysis of the solidification paths of the fourteen alloys as well as solid/liquid equilibria investigations, a partial liquidus projection in the investigated region was proposed. Moreover, the composition and melting temperature of the γFe–TiB2–Fe2B ternary eutectic alloy are determined with good accuracy. This study is a first step towards an extended experimental work on the iron-rich corner of the Fe–Ti–B ternary system.

Simulation study of the plasma-brake effect

Abstract. Plasma brake is a thin, negatively biased tether that has been proposed as an efficient concept for deorbiting satellites and debris objects from low Earth orbit. We simulate the interaction with the ionospheric plasma ram flow with the plasma-brake tether by a high-performance electrostatic particle in cell code to evaluate the thrust. The tether is assumed to be perpendicular to the flow. We perform runs for different tether voltage, magnetic-field orientation and plasma-ion mass. We show that a simple analytical thrust formula reproduces most of the simulation results well. The interaction with the tether and the plasma flow is laminar (i.e. smooth and not turbulent) when the magnetic field is perpendicular to the tether and the flow. If the magnetic field is parallel to the tether, the behaviour is unstable and thrust is reduced by a modest factor. The case in which the magnetic field is aligned with the flow can also be unstable, but does not result in notable thrust reduction. We also correct an error in an earlier reference. According to the simulations, the predicted thrust of the plasma brake is large enough to make the method promising for low-Earth-orbit (LEO) satellite deorbiting. As a numerical example, we estimate that a 5 km long plasma-brake tether weighing 0.055 kg could produce 0.43 mN breaking force, which is enough to reduce the orbital altitude of a 260 kg object mass by 100 km over 1 year.

Motion of the plasma critical layer during relativistic-electron laser interaction with immobile and comoving ion plasma for ion acceleration

We analyze the motion of the plasma critical layer by two different processes in the relativistic-electron laser-plasma interaction regime (a0&amp;gt;1). The differences are highlighted when the critical layer ions are stationary in contrast to when they move with it. Controlling the speed of the plasma critical layer in this regime is essential for creating low-β traveling acceleration structures of sufficient laser-excited potential for laser ion accelerators. In Relativistically Induced Transparency Acceleration (RITA) scheme, the heavy plasma-ions are fixed and only trace-density light-ions are accelerated. The relativistic critical layer and the acceleration structure move longitudinally forward by laser inducing transparency through apparent relativistic increase in electron mass. In the Radiation Pressure Acceleration (RPA) scheme, the whole plasma is longitudinally pushed forward under the action of the laser radiation pressure, possible only when plasma ions co-propagate with the laser front. In RPA, the acceleration structure velocity critically depends upon plasma-ion mass in addition to the laser intensity and plasma density. In RITA, mass of the heavy immobile plasma-ions does not affect the speed of the critical layer. Inertia of the bared immobile ions in RITA excites the charge separation potential, whereas RPA is not possible when ions are stationary.

Cluster ion formation during sputtering processes: a complementary investigation by ToF-SIMS and plasma ion mass spectrometry

Plasma ion mass spectrometry using a plasma process monitor (PPM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) have been complementarily employed to investigate the sputtering and ion formation processes of Al-doped zinc oxide. By comparing the mass spectra, insights on ion formation and relative cross-sections have been obtained: positive ions as measured during magnetron sputtering by PPM are originating from the plasma while those in SIMS start at the surface leading to large differences in the mass spectra. In contrast, negative ions originating at the surface will be accelerated through the plasma sheath. They arrive at the PPM after traversing the plasma nearly collisionless as seen from the rather similar spectra. Hence, it is possible to combine the high mass resolution of ToF-SIMS to obtain insight for separating cluster ions, e.g. Znx and ZnOy, and the energy resolution of PPM to find fragmentation patterns for negative ions. While the ion formation processes during both experiments can be assumed to be similar, differences may arise due to the lower volume probed by SIMS. In the latter case, there is a chance of small target inhomogeneities being able to be enhanced and lower surface temperatures leading to less outgassing and, thus, retention of volatile compounds.

Survey of the H-mode power threshold and transition physics studies in ASDEX Upgrade

An overview of the H-mode threshold power in ASDEX Upgrade which addresses the impact of the tungsten versus graphite wall, the dependences upon plasma current and density, as well as the influence of the plasma ion mass is given. Results on the H–L back transition are also presented. Dedicated L–H transition studies with electron heating at low density, which enable a complete separation of the electron and ion channels, reveal that the ion heat flux is a key parameter in the L–H transition physics mechanism through the main ion pressure gradient which is itself the main contribution to the radial electric field and the induced flow shearing at the edge. The electron channel does not play any role. The 3D magnetic field perturbations used to mitigate the edge-localized modes are found to also influence the L–H transition and to increase the power threshold. This effect is caused by a flattening of the edge pressure gradient in the presence of the 3D fields such that the L–H transitions with and without perturbations occur at the same value of the radial electric field well, but at different heating powers.

Plasma ion composition measurements for Europa

Jupiter magnetospheric interactions and surface composition, both important to subsurface ocean detection for the Galilean icy moons Europa, Ganymede, and Callisto, can be measured using plasma ion mass spectrometry on either an orbiting spacecraft or one designed for multiple flybys of these moons. Detection of emergent oceanic materials at the Europa surface is more likely than at Ganymede and Callisto. A key challenge is to resolve potential intrinsic Europan materials from the space weathering patina of iogenic species implanted onto the sensible surface by magnetospheric interactions. Species-resolved measurements of pickup ion currents are also critical to extraction of oceanic induced magnetic fields from magnetospheric interaction background dominated by these currents. In general the chemical astrobiological potential of Europa should be determined through the combination of surface, ionospheric, and pickup ion composition measurements. The requisite Ion Mass Spectrometer (IMS) for these measurements would need to work in the high radiation environment of Jupiter's magnetosphere between the orbits of Europa and Ganymede, and beyond. A 3D hybrid model of the moon-magnetosphere interaction is also needed to construct a global model of the electric and magnetic fields, and the plasma environment, around Europa. Europa's ionosphere is probably usually dominated by hot pickup ions with 100–1000eV temperatures, excursions to a “classical” cold ionosphere likely being infrequent. A field aligned ionospheric wind driven by the electron polarization electric field should arise and be measurable.

Highly-selective wettability on organic light-emitting-diodes patterns by sequential low-power plasmas

Patterned organic light-emitting-diode substrates were treated by oxygen (O2) and tetrafluoromethane (CF4) radio-frequency (rf, 13.56 MHz) plasmas of low-power (close to 1 W) that were capacitively-coupled. An unexpected wettability contrast (water contact angle difference up to 90°) between the indium-tin-oxide anode and the bank resist regions was achieved, providing excellent conditioning prior to the ink-jet printing. This selectivity was found to be adjustable by varying the relative exposure time to the O2 and CF4 sequential plasmas. Static contact angle measurements and extensive x-ray photoelectron spectroscopy analyses showed that the wetting properties depend on the carbon and fluorine chemical functional groups formed at the outermost surface layers, whereas atomic force microscopy images did not show a morphological change. Plasma optical emission spectroscopy and ion mass spectroscopy suggested that surface functionalization was initiated by energy transfer from ionic species (O+, O2+, CF+, CF2+, and CF3+) and excited neutrals (O∗ and F∗). The absolute ion fluxes measured on the substrates were up to 1014 cm−2 s−1 and the ion energies up to 20 eV, despite the low powers applied during the process.