Ion Collection Research Articles

Effects of translation misalignment on ion optics with slit apertures

For ion thrusters, the deflection of the ion beam caused by the relative translation of the grids is one of the primary factors limiting the erosion lifetime of the ion optical system. A two-dimensional (2D) simulation package of the ion optic system is developed to investigate the ion sputtering corrosion due to grid translation misalignment. For benchmark cases, the 2D simulation package shows a reasonable consistency compared to the experimental method in ion beam deflection angle and drain-to-beam current ratio, indicating the effectiveness of the simulation package. The deviation between the simulated deflection angle and the experimental value is within 8.86%. Furthermore, this 2D package is employed to analyze the variation patterns of ion beam, ion collection, and the distribution of ion sputtering rates caused by grid translation. The simulation results indicate that the ion beam deflection occurs in the direction opposite to grid translation. The number of ions collected at different positions on the acceleration grid shows different tendencies. Only the upstream surface Sy− and the aperture surface Sx+ will be subjected to energetic ion impingement. The sputtering of energetic ions on these two surfaces becomes the dominant factor limiting the grid’s ion corrosion lifetime when the grid translation is significant. The sputtering rate of energetic ions can exceed that of charge exchange (CEX) ions by more than 10 times. The proportion of the region where energetic ions contribute to sputtering expands with increasing grid misalignment, reaching up to 52.5% on surface Sx+. Additionally, the downstream surface Sy+ and the aperture surface Sx− are only subjected to CEX ion sputtering regardless of grid translation. Moreover, the CEX ion sputtering regions on surfaces Sx− and Sx+ expand as the grid misalignment distance increases. The peak in the ion sputtering rate distribution profile on surface Sy+ becomes more prominent due to grid translation, with the sputtering rate at the peak position reaching approximately 1.65 times that of the surrounding lower-rate regions. The analysis of the electric field indicates that local electric field variations caused by grid misalignment are the underlying reason for the ion erosion characteristics.

Beam energy recovery in Neutral Beam Injections and related simulations

The Neutral Beam Injectors (NBI) will be used to further increase the plasma temperature for the ignition of the fusion reactions in the ITER project. For future applications of electric energy production, the NBI efficiency is crucial. Since the gas neutralizer gives large residual ion fractions of D+ and D-, adequate energy recovery systems may be necessary. Recently a conceptually simple beam energy recovery based on space charge effects has been proposed; it can also work as an ion dump device, with advantages in removing the residual ions with reduced power dissipation. Preliminary simulation results were evidence of that the proposed device can remove all the residual ions by collecting them at very low energy on proper electrodes. In this contribution, further simulations with more accurate space charge calculations are reported to mostly confirm the high residual ion collection efficiency obtained in the preliminary simulations. The simulated operation voltage is also increased from 20 kV to 500 kV in steps. Higher efficiencies require some increase of the collector length, especially at higher operation voltage, as here discussed. Some design detailed features are also updated.

Comparative study of magnetic field effect on fast plasma flow of heavy and light species investigated by spectroscopic measurement

To understand the effects of magnetic fields on the propagating plasma flows of heavy and light ion species, a laboratory-scale experiment was conducted using a pulsed-power discharge. The plasma drift velocity and electron temperature were estimated by time-of-flight and line-pair methods, respectively, using spectroscopic measurements. Ion current waveforms were measured using an ion collector. When a magnetic field was applied, the plasma drift velocity decreased and the electron temperature increased in both heavy and light plasmas. The magnetic Reynolds number, pressure balance between the plasma and magnetic field, and ion current waveforms show that heavy plasma has a high possibility of deforming the magnetic field and generating accelerated ions through interaction with the magnetic field.

Absolute electron impact ionization cross-sections for CF4: Three dimensional recoil-ion imaging combined with the relative flow technique.

Here we present measurements of dissociative and non-dissociative cross-sections for the electron impact of the CF4 molecule. The present experiments are based on a Recoil Ion Momentum Spectrometer (RIMS), a standard gas mixing setup for CF4, and a reference gas. The measurements were carried out at several electron energies up to 1keV, covering the energy range of previous experiments. We apply the relative flow technique (RFT) to convert the relative cross-sections measured by the RIMS into absolute values. Using the combination of RIMS and RFT, ion collection and calibration errors were minimized. The results were compared with theoretical and experimental studies available in the literature. Previous electron impact experiments present relative cross-sections or use correction terms for the absolute cross-sections due to losses of energetic ions. We elucidate the differences between the new measurement method and the existing ones in the literature and explain why the present method can be considered reliable. Furthermore, we show how reducing correction terms affects the results.

Characterization of electron extraction from a 40.68 MHz radiofrequency inductive plasma source

An electron current is extracted from a 40.68 MHz inductively coupled plasma source, in which a grounded ion collector electrode is installed to maintain the charge neutrality, by applying a positive voltage to a metallic plate located downstream of the source. The ion collector has an exit orifice of either 20 mm or 2.2 mm in diameter, showing a larger electron extraction current for the 2.2 mm-diameter case. The result is discussed with a global model, implying a higher plasma density for the 2.2 mm-diameter case due to the increased neutral pressure in the source. Metallic and insulator exits having a 2.2 mm-diameter orifice are tested, providing a larger electron extraction current for the metallic case despite a small fraction of a change in the total ion collection area. It is speculated that the electron extraction current is affected by the ion collection near the electron extraction hole and the potential distribution.

SiC plasma characterization produced by 3 ns pulse laser at 1010 W/cm2 intensity

A silicon carbide (SiC) plasma has been produced by a Q-switched laser at 1064 nm, 3 ns pulse and 1010 W/cm2 intensity, in high vacuum to investigate the fundamental mechanisms of laser-semiconductor interaction. Although the high hardness and chemical stability restrain the SiC micromachining, it is a valuable semiconductor for devices working under extreme conditions. The plasma has been characterized by using time-of-flight (TOF) measurements of ions detected by an ion collector ring (ICR) and an ion energy analyzer (IEA). Fast CCD camera, quadrupole mass spectroscopy (QMS) and surface profiler have been employed to provide deep insights into the laser-SiC interaction mechanisms. Ion kinetic energies, charge states, plasma expansion velocity, ablation yield per laser pulse, plasma temperature and density have been measured. Applications of the laser-generated plasma are presented and discussed.

Analysis of the ion collection model in the ExB probe

An ExB probe is a pass-band velocity filter for an ion beam. The ExB probe measurement is related to the ion velocity distribution function (IVDF); however, the finite pass-band filter window size leads to differences in the true IVDF and measured ExB probe spectrum. We derive for the first time an analytical ExB probe transmittancy matrix and use it to examine differences in the IVDF and the probe spectrum. The probe spectra are compared to a synthetically defined test IVDF to study how probe geometry and ion species affect the differences. It is found that the difference in the probe spectrum and the true IVDF is dependent on the ion species, and the deviation is larger for heavier ions. The peak velocity of the spectrum was shifted by up to 13%, and the velocity spread was broadened by up to 276%. The relative ion species fraction is calculated from the probe spectra by two different methods and compared to the true fraction. Using the approach of this work, direct integration of the spectrum resulted in a 2% difference, while a more common approach from literature overestimated one ion species by 184%.

Tuning of ion current rectification and ion current saturation of multiple nanochannels in polymeric membrane

The present study gives an insight into ion flow dynamics of aqueous electrolytes via functionalized multiple nanochannels in polyethylene terephthalate (PET) membrane. The selectivity of certain ions (anions/cations) of various electrolyte combinations KCl- KClO4 (S1), KBr-KCl (S2), KBr-KClO4 (S3) over their counter-ions by the nanochannels (generated via swift heavy ion irradiation followed by chemical etching) has been studied. Tuning of the ion transport and ion current rectification has been done using different functionalized nanochannels (with charged carboxyl and protonated amino groups). The impact of ion selectivity of the nanochannels is reflected in the short circuit current and ion current saturation of different systems. The collection of counter ions outside the channels along with the in-built potential due to the flow of ions inside the channels play a crucial role in the ion transport behaviour of the collective system. The cation-selective channels (with charged carboxyl groups) show low rectification ratio compared to the anion-selective channels. The functionalized nanochannels with two -OH polar charge groups (generated through the amino-silane based reagent (3-aminopropyl) trimethoxysilane (APTMS)) exhibit higher current saturation values (S1AP∼31 μA, S2AP∼30 μA and S3AP ∼ 30.5 μA) and higher short circuit current values (S1AP ∼32.3μA, S2AP ∼ 29.6μA and S3AP ∼31.3μA) due to the overlapping of electric double layer (EDL). Systematic study of tuning of ion transport through nanochannels helps to understand the nanofluidic flow and has imminent application in the fabrication of nanoelectronic and bioinspired nanodevices.

Fullerene C20 carbon nucleation induced by IR ns pulsed laser-generated plasma

Intense laser pulses can be employed to generate plasma, carbon aggregates, and nanoparticles. The plasma produced by ns laser pulses impinging on carbon targets in a vacuum generates carbon vapors, atoms nucleation and growth of nano aggregates. Mass quadrupole spectrometry has permitted to analyze the mass of the carbon atoms and molecules produced in a vacuum by laser-generated plasma, discovering that the fullerene C20 and other small carbon aggregates have a high probability of being produced. In this paper, the conditions of C20 aggregate synthetization are presented, and their yield generation is approximately evaluated. It also calculated the process ablation yield, the maximum carbon energy acquired in the plasma, the plasma temperature and density, the adiabatic plasma expansion velocity, and the carbon ion charge state distributions. To this, measurements of time-of-flight (TOF) of ions have been performed using suitable ion collectors and ion energy analyzers.

Ion acceleration from golden mylar film irradiated by visible ns pulsed laser

AbstractA Pulsed ns laser operating at 532 nm wavelength with 150 mJ pulse energy was employed to irradiate micrometric thick mylar films, from 1 to 100 μm thick, covered by 0.05 μm Au in the back face. Protons and light ions have been accelerated by the electric field developed in the non‐equilibrium plasma by the laser pulse in a vacuum at an intensity of the order of 1010 W/cm2. Time‐of‐flight technique, obtained using a Faraday cup and a fast storage oscilloscope, is employed to measure the ion velocity, energy, and yield emitted in backward and forward directions. The yield of the emitted plasma photons is also evaluated. Two ion collectors are used in opposite directions to measure the plasma radiations emitted in backward and forward directions. Data analysis is based on the Coulomb‐Boltzmann‐shifted (CBS) distribution function. The target ablation yield is evaluated in the order of 3.5 μm per laser shot.

Method of kinetic energy reconstruction from time-of-flight mass spectra.

We present a method for the reconstruction of ion kinetic energy distributions from ion time-of-flight mass spectra through ion trajectory simulations. In particular, this method is applicable to complicated spectrometer geometries with largely anisotropic ion collection efficiencies. A calibration procedure using a single ion mass peak allows the accurate determination of parameters related to the spectrometer calibration, experimental alignment, and instrument response function, which improves the agreement between simulations and experiment. The calibrated simulation is used to generate a set of basis functions for the time-of-flight spectra, which are then used to transform from time-of-flight to kinetic-energy spectra. We demonstrate this reconstruction method on a recent pump-probe experiment by Asmussen etal. [Asmussen etal., Phys. Chem. Chem. Phys., 23, 15138, (2021)] on helium nanodroplets and retrieve time-resolved kinetic-energy-release spectra for the ions from ion time-of-flight spectra.

Selective removal of Gallium from mixed metal solutions with Arsenic by ion flotation using the biosurfactant rhamnolipid

Rhamnolipids have received great attention in various environmental applications in terms of metal complexation and recovery. However, the effect of metal ions on interfacial and foaming properties in relation to flotation are not much studied. To assist, this study investigated the effect of metal ions alone and in a mixed metal system containing Gallium (Ga) and Arsenic (As) on these properties of rhamnolipid, along with isothermal titration calorimetry to study rhamnolipid-metal interactions. Further, the potential of rhamnolipid to recover and separate Ga from As was assessed using bioionflotation. Ga alone and in mixed metal system had a remarkable effect on the interfacial and foaming properties of rhamnolipid as compared to As alone. The effect of operating parameters like pH, rhamnolipid concentration, and airflow rate had a significant influence on the separation performance. Nearly 74% Ga was removed at 0.85 mM rhamnolipid concentration, pH 6, and an airflow rate of 80 ml/min. The selectivity index of Ga over As was highest (17.2) at 0.85 mM rhamnolipid concentration, pH 6, and an airflow rate of 40 ml/min. Also, the selective separation of Ga was dependent on the recovery of water from the foam. Altogether, the results provide new insights on the interfacial and foaming properties of rhamnolipid and its efficiency as an ion collector for Ga and showed that the optimized process parameters could be expected to provide very efficient separation and recovery of target metal via ion flotation.

Ion acceleration from aluminised mylar film irradiated by visible ns-pulsed laser

A ns-pulsed laser operating at 532 nm wavelength has been employed to irradiate micrometric mylar films (1–100 μm) with an attached 0.1 μm Al film on its back face. Protons and light ions have been accelerated by the electric field developed in the non-equilibrium plasma generated by the laser pulse in a vacuum at an intensity of the order of 1010 W/cm2. The Time-of-flight (TOF) technique, using a Faraday cup (ion collector) coupled to a fast storage oscilloscope, has been employed to measure the ion velocity, energy and yield. The yield of plasma-emitted photons has been also evaluated. Two ion collectors have been used in opposite directions to measure the maximum ion acceleration by the TOF data acquired in backward and forward directions and the photon yield as a function of the target thickness. The evaluation of the ion energy distribution has been based on the Coulomb-Boltzmann-Shifted (CBS) distribution function.

Ion-collection characteristics of photoplasma for atomic vapor laser isotope separator module in electrostatic fields

The laser-based isotope separation process is currently pursued to enrich precursor medical isotopes like lutetium-176 and ytterbium-176. India has successfully produced radionuclide lutetium-177 for clinical use by neutron activation. Atomic vapor laser isotope separation (AVLIS) is used as the enrichment technology. Understanding the physics and technology of processes, like atomic-beam generation, photoplasma production, and ion collection, is essential to designing any AVLIS module. So, a stand-alone research facility was developed before the production plant. This article describes the facility and the experimental and theoretical studies of ion collection in electrostatic fields using barium as the working element. Two types of ion extractors, plate–photoplasma–plate and plate–photoplasma–grid–plate, were designed and fabricated. A model of photo-ion collection in these electrostatic ion extractors was arrived at. Scaling of the initial photo-ion densities and the electric fields is crucial to photoplasma evolution spanning single-particle to collective regimes. Estimates of ion-collection rates of the Indian AVLIS modules for lutetium-176 and ytterbium-176 were carried out. By invoking plasma physics, the technological aspect of producing enriched isotopes was solved by judiciously integrating the atom source, laser system, photoplasma, and ion-extractor geometries. Limitations of the electrostatic ion extractors were also flagged.

Evaluating Ion Accumulation and Storage in Traveling Wave Based Structures for Lossless Ion Manipulations.

Structures for lossless ion manipulations (SLIM) technology has demonstrated high resolving power ion mobility separation and flexibility to integrate complex ion manipulations into a single experimental platform. To enable IMS separations, trapping/accumulating ions inside SLIM (or in-SLIM) prior to injection of a packet for separations provides ease of operation and reduces the need for dedicated ion traps external to SLIM. To fully characterize the ion accumulation process, we have evaluated the effect of TW amplitudes, ion collection times, and storage times on the "in-SLIM" accumulation process. The study utilized a SLIM module comprising 5 distinct tracks, each with a specific ion accumulation configuration. The effect of the TW conditions on the accumulation process was investigated for a 3-peptide mixture: kemptide, angiotensin II, and neurotensin at a TW speed of 106 m/s. The effect of ion accumulation time/collection time and storage time was investigated, in addition to TW amplitude. Overall, the signal of the analyte ions increased when the ion collection time increased from 49 to 163 ms but decreased when the ion collection time increased further to 652 ms due to the space charge effects. Ion losses were observed at high TW amplitudes (e.g., 15 Vp-p and 20 Vp-p). In addition, under space charge conditions (e.g., collection times of 163 and 652 ms), the signal of the analyte ions decreased with an increase in storage times for all TW amplitudes applied to the trapping region. For ion accumulation, the data indicate that gentler TW conditions must be utilized to minimize ion losses and fragments to benefit from the "in-SLIM" accumulation process. Wider SLIM tracks provided better performance than those with narrower tracks.

Field output correction factors of small static field for IBA razor nanochamber

Purpose. The goal of this work is present results of field output factors (OF) using an IBA CC003 (Razor NanoChamber) and compare these results with PTW 60019 (MicroDiamond) and IBA Razor Diode. The experimental results for IBA CC003 were also compared with Monte Carlo (MC) Simulation, using Penelope and Ulysses programs. In addition, field output correction factors () for IBA CC003 were derived with three different methods: (1) using PTW 60019 and IBA Razor as reference detectors; (2) comparison between MC and experimental measurements; and (3) using only MC.Material and Methods. The beam collimation included in this study were (1) square field size between 10 × 10 and 0.5 × 0.5 cm2 defined by the MLC and jaws and (2) cones of different diameters. For IBA CC003 it was determined the polarity and ion collection efficiency correction factors in parallel and perpendicular orientation.Results. The results indicate (1) the variation of polarity effect with the field size is relevant for the determination of OF using IBA CC003, especially for parallel orientation; (2) there is no significant variation of the ion collection efficiency with the field size using IBA CC003 in parallel orientation; (3) OF differences between IBA CC003 and PTW 60019/IBA Razor, and experimental and MC results, increase with decreasing field size;The results indicate (1) using the first and second method, increase with decreasing field size, which can be related with the influence of the volume effect and (2) using the third method, decrease with decreasing field size, which can be explained by the perturbation effect.Conclusions. Our results demonstrate the need of applying for IBA CC003 for 1 cm, to compensate for volume averaging and perturbations effects.

Cylindrical hot cathode ionisation gauge – The concept and simulations

A novel design of an ionisation vacuum gauge is presented, aiming to achieve predictable sensitivity and high accuracy in high and the ultra-high vacuum range. The proposed design features a belt-like electron beam emitted from a linear filament, following a circular trajectory between two cylindrical electrodes, resembling a cylindrical analyser. The proposed design offers several key upsides: a precisely defined electron beam trajectory with reduced susceptibility to path variations, effective electron collection in a Faraday cup able to contain secondary emissions and backscattered electrons, and the inclusion of a suppressor grid in front of the ion collector to eliminate ion-induced secondary electron emission. These features are expected to secure high stability of the gauge and the low pressure limit. An in-depth description of the design is presented, along with the discussions on simulations of the key components that provide the improved performance.

A self-balanced electron-emissive double Langmuir probe drawing no electron loss from its diagnosed plasma

In this work, a new form of double Langmuir probe (DLP) system, an emissive double Langmuir probe (EDLP), which connects a collecting probe tip and an electron-emitting probe tip to form a DLP system, has been proposed as a replacement of the currently more common asymmetric double Langmuir probes (ADLPs). The EDLP was both computationally and experimentally investigated in this work. Using an emissive probe to provide an emission current I E to balance the electron collection current I C,e, the EDLP can obtain a full I–V trace when I E,TL > I C,es and be used in a similar manner to a single Langmuir probe with the exception that the EDLP, as with the ADLP, does not measure the local plasma potential. I E,TL ≫ I C,es can be realized on an EDLP without needing the much larger ion collection area required by the ADLP, and at I E,TL ∼ 2I C,es the relative error between the EDLP and a single Langmuir probe is ∼15% due to space-charge limited effects, which is better than that of the ADLP at ∼30% under similar conditions. The performance of an EDLP depends on whether its electron emission current sufficiently offsets its electron-collecting current, making it particularly fitting for scenarios where the plasma density is low but a large probe is difficult to employ due to the limited balancing ion current. This makes the EDLP potentially useful on satellites, which operate in very low temperature plasmas with a limited ion loss area to balance a Langmuir probe’s electron-collecting current. With the advances in highly emitting materials, EDLPs are expected to significantly remove the design barriers of Langmuir probes on satellites.

Gallium bioionflotation using rhamnolipid: Influence of frother addition and foam properties

The current study investigated the application of rhamnolipid biosurfactant as an ion collector in bioionflotation. In a top-down approach, the influence of rhamnolipid on gallium (Ga) ion flotation and recovery were investigated followed by detailed studies on the influencing parameters and foam characterization. Rhamnolipid exhibits extensive foaming properties and foam produced by rhamnolipid alone has higher stability making it difficult to collect the flotation concentrates. An addition of 1,2-decanediol introduces instability to this foam and also aids in concentrate collection. Observations during the flotation studies resulted in a series of investigations on rhamnolipid properties such as aggregate size, surface tension, and foam characterization. These results indicated that the addition of Ga and/or 1,2-decanediol affected the molecular aggregation of rhamnolipid. Moreover, the surface activity, foamability, foam drainage, and foam coarsening/coalescence of the rhamnolipid changed in the presence of Ga and/or 1,2-decanediol. In a batch bioionflotation process, rhamnolipid was able to remove nearly 80% Ga at pH 7 in presence of 1,2-decanediol. However, upgrading was higher at pH 6 without 1,2-decanediol, which is important when considering the flotation recovery in presence of other metals. Such biosurfactants have a high potential for wide applications in ion flotation and further optimization of flotation parameters is essential.

Development and numerical investigation of Mach probe model in a hypersonic, low-temperature flowing plasma

This study conducted a numerical simulation around a Mach probe under hypersonic low-temperature plasma. The Mach probe has three ion collection planes: front, side, and back. Under a hypersonic flowing plasma, the front and side planes are practical ion collection areas, and the backplane collects no ion flux. The collected ion current density on the front plane is almost identical to that of the mainstream ion flux. By contrast, the ion current collected on the side plane is affected by the concentration of the electric field at the probe edge. As this edge effect has a different influence on the front and side planes, the ion current density ratio of the side to the front planes is dominated by a non-dimensional parameter—the ratio of electrostatic to kinetic flow energy. Based on this non-dimensional parameter, the calculated ion current density ratio can be fitted using a simple mathematical formula. Therefore, the proposed Mach probe model with non-dimensional parameters extends the conventional Mach probe model validated in sub-to-supersonic high-temperature plasma to hypersonic low-temperature flowing plasma, which is commonly observed in electric propulsions.