Extraction Voltage Research Articles

Study on the Design and Application of the Three-electrode Ionization Particle Sensor

Accurate detection is the foundation of haze governance. The existing particle concentration detection methods and instruments have many shortcomings, such as complex structure, high cost, easy blockage, short life, and significant impact of environmental changes. Therefore, this paper proposes a silicon micropillar three-electrode ionization particle sensor based on the gas discharge principle and studies the sensor's sensitivity to PM2.5 particles. Three-electrode comprises a cathode with micro silicon pillars grown on the surface, an extracting electrode, and a collecting electrode. It shows that the cathode current of the sensor increases linearly with extraction voltage and nonlinearly with temperature. As the cathode material of the sensor, the silicon micropillar is compared with the carbon nanotube to solve the burn problem of the nanotube rising from positive ions bombardment during gas discharge. The collecting current of the sensor shows a decreasing trend with the increase in particle concentration. The collecting current and sensitivity of the sensor are much higher in radio frequency excitation than in direct current excitation. The sensor developed in this paper displays the advantages of simple technology, high integration, low cost, and high sensitivity, and it exhibits great application potential.

Influence of ion species on extraction characteristics of mixed ion beams

Abstract The spatial distributions of different kinds of ions are usually not completely the same in the process of extracting. In order to study the reason for the different characteristics of ion extraction, a simplified simulation model of Cu+ and Cr+ ions extraction process was established by 2D3V (two-dimensional in space and three-dimensional in velocity space) particle-in-cell (PIC) method. The effects of different extraction voltages from 0 V to 500 V on the density distribution of Cu+ and Cr+ ions and the change of plasma emission surface were analyzed. On the basis of this model, the ion density distribution characteristics of Cu+ ions mixed with Li+, Mg+, K+, Fe+, Y+, Ag+, Xe+, Au+, and Pb+ ions respectively under 200-V extraction voltage are further simulated, and it is revealed that the atomic mass of the ions is the key reason for different ion density distributions when different kinds of ions are mixed and extracted, which provides support for further understanding of ion extraction characteristics.

An efficient microchip electromembrane extraction online with high-performance liquid chromatography for the measurement of nicotine in high consumption vegetables.

Nicotine, a highly addictive substance, is naturally produced in the Solanaceae family of plants, particularly tobacco. The presence of nicotine in plant foods has adverse effects on the lungs, kidneys, heart, and reproductive system. A novel three-phase microchip flat electromembrane coupled with online high-performance liquid chromatography (HPLC) was developed to analyze nicotine in tomato, mushroom, eggplant, bell pepper, and red pepper. The microchip was connected to the HPLC in online mode. All effective variables were optimized to achieve the best extraction response. The use of electric potential and 2-nitrophenyl octyl ether -5% di(2-ethylhexyl) phosphate as a modified supported liquid membrane (SLM) increased the sensitivity and selectivity. The optimal extraction voltage, extraction time, and ion balance were 40 V, 10 min and 0, respectively. The dynamic linear range was 0.5-1000 ng g-1. The obtained recovery, relative standard deviation, and enrichment factor were 98%, 7%, and 35, respectively. The limits of detection 0.4 ng g-1 and the limits of quantification were obtained 1.3 ng g-1. The highest (105.0 ng g-1) and lowest (3.4 ng g-1) concentrations of nicotine were obtained for eggplant and tomato, respectively. Selective electromembrane extraction of nicotine from the donor phase to the acceptor phase was performed by optimizing the main variables influencing the method mechanism. The new channel design in this analytical system and online injection increased efficiency, stability, and repeatability. The results revealed that this method is capable for the efficient determination of trace amount of nicotine in edible vegetables.

A low-energy MHz repetition rate short-pulse electron gun

An electron gun that can produce MHz repetition rates and nanosecond pulses is described. The gun uses a Pierce grid in combination with an anode to extract electrons from a tungsten filament cathode. The electrons emerging from the anode are accelerated and focused using two triple-aperture lenses to form a beam. By applying a high slew rate grid pulse that transitions through the extraction voltage region of the grid/anode combination, pulses of electrons are produced from the gun that have temporal widths less than 5 ns. The pulsed beams are produced at both the rising and falling edges of the driving pulse. The characteristics of the emerging electron beams have been determined using an (e, 2e) coincidence spectrometer, and examples where they are used for time of flight decay measurements are presented.

The Child Langmuir Illusion

A Particle in Cell (PIC) model of ion beam extraction from a plasma provides strong evidence that the origin of the observed V(3/2) relationship between the applied extraction voltage and beam current is caused by meniscus shape and collimation on the extraction electrode, not by space charge limited extraction. Excellent correlation between the PIC model, a gun code and experiment is shown for 100 µA Ar+ beams. The s-shape in the emittance phase space is shown to be caused by the radial electric field created by the external edge of the plasma electrode.

Intense vanadium ion beam production for super-heavy element research experiments

Long-term production of an intense 51V13+ ion beam was imperative for synthesizing a new element (Z=119) at RIKEN. We systematically measured the beam intensity as a function of microwave power and material consumption rate for effectively producing an intense beam. Consequently, we generated a 1 emA of 51V13+ ion beam at an injected microwave power and extraction voltage of 3.5 kW and 12.6 kV, respectively.

Experimental Validation of Comprehensive Calculation for High-Resolution Linear MALDI-TOF Mass Spectrometry.

This work discusses the effectiveness of the previously developed comprehensive calculation model to optimize linear MALDI-TOF mass spectrometers. The model couples space- and velocity-focusing to precisely analyze the flight-time distribution of ions and predict optimal experimental parameters for the highest mass resolving power. Experimental validation was conducted using a laboratory-made instrument to analyze CsI3 and angiotensin I ions in low to medium m/z range. The results indicate that the predicted optimal extraction voltage and delay were reasonably accurate and effective. In the low m/z range, the peak width obtained using optimal parameters reached the sub nanosecond range, corresponding to a mass resolving power of 10 000-17 000, or 20 000-34 000 if shot-to-shot random fluctuations were minimized by the dynamic data correction method. The observed optimal mass resolving power in the current experiment is 4.8-7.8 times that of commercial instruments. Practical limitations resulting in the gap between the observed and theoretical ultimate mass resolving power are discussed.

Study on stray electrons ejecting from a long-pulse negative ion source for fusion

The negative ion based neutral beam injection is a desirable plasma heating and current drive method for the large-scale magnetic fusion devices. Due to the strict requirements and difficult development of the negative ion source for fusion, a long-pulse negative ion source has been developed under the framework of the Comprehensive Research Facility for Fusion Technology in China. This negative ion source consists of a single radio frequency (RF) driver plasma source and a three-electrode accelerator. The typical extraction and acceleration voltage are 4–8 kV and 40–50 kV, respectively. During one shot of the long-pulse (∼100 s) beam extraction, the gas pressure in the vacuum vessel increased sharply and the temperature of the cryopump rise from 8 K to 20 K. Moreover, the vessel wall appeared a high temperature after several long-pulse shots. A self-consistent simulation of beam-gas interaction revealed that the heat loads on the vessel wall should be caused by the stray electrons ejecting from the accelerator. Those stray electrons are mainly generated via the stripping or ionization collisions and strongly deflected by the downstream side of the deflection magnetic field for the co-extracted electron. The location of hot spots measured by infrared thermography is consistent with the simulation results. To solve this problem, a series of electron dumps are designed to avoid the direct impinging of the ejecting electrons on the cryopump and the vessel wall. And the results suggest that the hot spots are almost eliminated.

Dextrin-assisted gel electromembrane extraction of chiral drugs: Improving the extraction efficiency and investigation of enantioselectivity of extraction

The present study investigates the use of dextrins (maltodextrin, β-cyclodextrin, and hydroxypropyl-β-cyclodextrin) to improve the efficiency of the agarose-based gel electromembrane extraction technique for extracting chiral basic drugs (citalopram, hydroxyzine, and cetirizine). Additionally, it examines the enantioselectivity of the extraction process for these drugs. To achieve these, dextrins were incorporated into either the sample solution, the membrane, or the acceptor solution, and then the extraction procedure was performed. Enantiomers were separated and analyzed using a capillary electrophoresis device equipped with a UV detector. The results obtained under the optimal extraction conditions (sample solution pH: 4.0, acceptor solution pH: 2.0, gel membrane pH: 3.0, agarose concentration: 3 % w/v, stirring rate: 1000 rpm, gel thickness: 4.4 mm, extraction voltage: 62.3 V, and extraction time: 32.1 min) indicated that incorporating dextrins into either the sample solution, membrane or the acceptor solution enhances extraction efficiency by 17.3–23.1 %. The most significant increase was observed when hydroxypropyl-β-cyclodextrin was added to the acceptor solution. The findings indicated that the inclusion of hydroxypropyl-β-cyclodextrin in the sample solution resulted in an enantioselective extraction, yielding an enantiomeric excess of 6.42–7.14 %. The proposed method showed a linear range of 5.0–2000 ng/mL for enantiomers of model drugs. The limit of detection and limit of quantification for all enantiomers were found to be < 4.5 ng/mL and <15.0 ng/mL, respectively. Intra- and inter-day RSDs (n = 4) were less than 10.8 %, and the relative errors were less than 3.2 % for all the enantiomers. Finally, the developed method was successfully applied to determine concentrations of enantiomers in a urine sample with relative recoveries of 96.8–99.2 %, indicating good reliability of the developed method.

Fatty Alcohol-Assisted Electro-Driven Liquid Membrane Multi-Stage Extraction Technology for Selective Separation and Purification of 3,4-Dihydroxybenzaldehyde from Salvia miltiorrhiza Bge.

3,4-Dihydroxybenzaldehyde (DHB) is a highly effective water-soluble compound in the traditional Chinese medicine Salvia miltiorrhiza Bge. Which demonstrates clear therapeutic effects against a variety of diseases. Therefore, the development of a selective approach for the separation of 3,4-dihydroxybenzaldehyde is of great significance. In this study, electro-driven extraction combined with multi-stage extraction technology was employed for the first time to separate 3,4-dihydroxybenzaldehyde from S. miltiorrhiza Bge. Decoction (Recovery ≥ 46.09%). Five long-chain fatty alcohols were selected as the supported liquid membrane (SLM) in the electro-driven extraction. Factors influencing extraction efficiency, including pH, voltage, and extraction time, were optimized using a design of experiments. Under the optimal conditions, the linearity of 3,4-dihydroxybenzaldehyde ranged from 0.01 to 100 μg·mL−1), with limits of detection (LOD) and quantification (LOQ) of 5 and 17 ng·mL−1, respectively. The precision of electro-driven liquid membrane extraction for 3,4-dihydroxybenzaldehyde was below 8.42%. This paper reports novel electro-driven liquid membrane extraction for selectively isolating 3,4-dihydroxybenzaldehyde from S. miltiorrhiza Bge.

High current field emission from Si nanowires on pillar structures

We investigate the influence of the geometry and doping level on the performance of n-type silicon nanowire field emitters on silicon pillar structures. Therefore, multiple cathodes with 50 by 50 pillar arrays (diameter: 5 μm, height: 30 μm, spacing: 50 μm) were fabricated and measured in diode configuration. In the first experiment, we compared two geometry types using the same material. Geometry 1 is black silicon, which is a highly dense surface covering a forest of tightly spaced silicon needles resulting from self-masking during a plasma etching process of single crystal silicon. Geometry 2 are silicon nanowires, which are individual spaced-out nanowires in a crownlike shape resulting from a plasma etching process of single crystal silicon. In the second experiment, we compared two different silicon doping levels [n-type (P), 1–10 and &amp;lt;0.005 Ω cm] for the same geometry. The best performance was achieved with lower doped silicon nanowire samples, emitting 2 mA at an extraction voltage of 1 kV. The geometry/material combination with the best performance was used to assemble an integrated electron source. These electron sources were measured in a triode configuration and reached onset voltages of about 125 V and emission currents of 2.5 mA at extraction voltages of 400 V, while achieving electron transmission rates as high as 85.0%.

A very low energy ion beam extraction system design of the GTS ECR ion source at GANIL

The GTS ion source, operated at 14.5GHz, provides multiply charged heavy ion beams for the ARIBE facility at GANIL. The facility variety is limited by the efficiency of the extraction especially in the few keV/q domain. In order to improve the ion source, the extraction system was upgraded numerically using IBSimu. The shape of the plasma and the puller electrodes was changed. It causes the increase of the electric field near the plasma meniscus and allows the use of lower extraction voltages at constant total ion beam current. The required beam parameters were taken from the experimental data. The opportunity of effective low energy beam formation (at a few keV/q or several hundreds eV/q beam energy) was studied. The high current and low energy ion beam production will provide new possibilities for ARIBE facility users.

Integrated multichip field emission electron source fabricated by laser-micromachining and MEMS technology

In this work, high-current field emission electron source chips were fabricated using laser-micromachining and MEMS technology. The resulting chips were combined with commercially available printed circuit boards (PCBs) to obtain a multichip electron source. By controlling the separate electron sources using an external current control circuit, we were able to divide the desired total current evenly across the individual chips deployed in the PCB-carrier. In consequence, we were able to show a decreased degradation due to the reduced current load per chip. First, a single electron source chip was measured without current regulation. A steady-state emission current of 1 mA with a high stability of ±1.3% at an extraction voltage of 250 V was observed. At this current level, a mean degradation slope of −0.7 μA/min with a nearly perfect transmission ratio of 99% ± 0.4% was determined. The measurements of a fully assembled multichip PCB-carrier electron source, using a current control circuit for regulation, showed that an even distribution of the desired total current led to a decreased degradation. This was determined by the increase in the required extraction voltage over time. For this purpose, two current levels were applied to the electron source chips of the PCB-carrier using an external current control circuit. First, 300 μA total current was evenly distributed among the individual electron source chips followed by the emission of 300 μA per electron source chip. This allows the observation of the influence of a distributed and nondistributed total current, carried by the electron source chips. Thereby, we obtained an increase in the mean degradation slope from +0.011 V/min (300 μA distributed) to +0.239 V/min (300 μA per chip), which is approximately 21 times higher. Moreover, our current control circuit improved the current stability to under 0.1% for both current levels, 300 μA distributed and 300 μA per chip.

Influence of extraction voltage on electron and ion behavior characteristics

The characteristics of the extracted ion current have a significant impact on the design and testing of ion source performance. In this paper, a 2D in space and 3D in velocity space particle in cell (2D3V PIC) method is utilized to simulate plasma motion and ion extraction characteristics under various initial plasma velocity distributions and extraction voltages in a Cartesian coordinate system. The plasma density is of the order of 1015 m−3–1016 m−3 and the extraction voltage is of the order of 100 V–1000 V. The study investigates the impact of various extraction voltages on the velocity and density distributions of electrons and positive ions, and analyzes the influence of different initial plasma velocity distributions on the extraction current. The simulation results reveal that the main reason for the variation of extraction current is the space-charge force formed by the relative aggregation of positive and negative net charges. This lays the foundation for a deeper understanding of extraction beam characteristics.

Exploring the Potential of a Thermionic LaB6 Virtual Source Mode Electron Gun for a High Angular Current Density and a Narrow Energy Distribution.

To date, lanthanum hexaboride (LaB6) thermionic electron sources have not been able fully to capitalize on their inherent potential, resulting in an ambiguous position within the application area. Although they exhibit higher brightness compared with a tungsten filament source, they still fall short of the performance of Schottky electron sources. This study aims to explore the capabilities of the LaB6 electron source under different operating conditions to bridge the gap, ultimately to realize its untapped potential. Simulations in virtual source mode indicated enhanced beam brightness and a reduced beam half-angle with an increase the extraction voltage, promising up to tenfold times higher beam brightness compared with the crossover mode. The energy distribution measured using a prelens retarding field energy analyzer revealed an energy distribution of 0.55 eV and a high angular current density of 33 mA/sr in the virtual source mode. Therefore, the virtual source mode of LaB6 can provide a narrow energy distribution akin to that of a ZrO/W Schottky electron gun (1600 K) while having an angular current density over 2,000 times higher. In addition, the stability of the virtual source mode is ±0.022%, while that of the crossover mode is ±0.138%.

Influences of coupling magnetic field of 2 cm electron cyclotron resonance ion thruster on plume neutralization

An electron cyclotron resonance ion thruster (ECRIT) has advantages of long service life and simple structure. The external coupling magnetic field of the ECRIT is one of factors that influences the plume neutralization process and coupling voltage of the neutralizer. The coupling magnetic field varies with the installation direction of the ion source and neutralizer as well as the direction of the internal magnetic pole. Calculating the distribution law of the coupling magnetic field and experimentally studying the influence of the coupling magnetic field on plume neutralization are very important. This paper focuses on two power rates and two flow rates of the ion source and conducts experiments on neutralization within the acceleration voltage range of 350 to 1 450 V to study the influence of changes in the direction and position of the ion source and the influence of the neutralizer′s magnetic pole on the ion beam extraction and maximum coupling voltage. The results indicate that the ion beam extraction is not influenced by the direction of the magnetic pole and the installation direction of the ion source and neutralizer. When the ion source is installed relatively perpendicular to the neutralizer, its coupling voltage is reduced. At the same time, changing the direction of the magnetic pole of the neutralizer into the opposite of the direction of the magnetic pole of the ion source also reduces the coupling voltage of the neutralizer. When the ion source is installed perpendicular to the magnetic pole of the neutralizer in the opposite direction, the coupling voltage is the lowest.

Improvement of miniaturized 2.45 GHz ECR plasma flood gun at PKU

In an ion implanter, plasma flood gun (PFG) is used to provide electrons to neutralize the accumulated charge on the wafer surface to avoid breakdown damage. With the development of ion implantation technology, four key requirements have been put forward for PFG. They are simple structure, plasma with high density and low electron temperature, no metal contamination and long life. The existing PFG, such as the filament type PFG, can hardly meet the above requirements at the same time. 2.45 GHz ECR ion source with the advantages of high beam density, high stability, long life time and no filament metal contamination, has shown great potential to work as PFG. Recently, a miniaturized 2.45 GHz permanent magnet electron cyclotron resonance PFG (PMECR-PFG) has been developed at Peking University (PKU). In our previous test, 8.8 mA electron extraction current was obtained with argon gas. In this work, by optimizing the magnetic field configuration to a resonant configuration, the performance of this ECR-PFG was greatly improved. With 100 W microwave power, an 80 mA electron current load was obtained under the extraction voltage of 0.1 kV. To minimize the metal contamination, a three-slit graphite plasma electrode was fabricated and a 50 mA load was generated at only 30 W RF power. During all tests, the gas consumption rate is lower than 0.6 sccm, which is beneficial to maintain the vacuum of implanter beamline.

N-SiOx/graphite/rGO-CNTs@C composite with dense structure for high performance lithium-ion battery anode

SiOx has become one of the most promising anode materials for lithium ion batteries due to its high specific capacity, abundant natural resources and suitable lithium insertion and extraction voltage. However, the low conductivity and the poor cycle performance seriously hinder its practical application. In here, a simple and effective method is proposed to disperse SiOx between carbon materials including flake graphite, reduced graphene oxide (rGO) and carbon nanotubes (CNTs), and then micron-sized N-SiOx/graphite/rGO-CNTs@C (N-SiOx/C@C) composite with dense structure is prepared by coating and pyrolysis of pitch. The synergistic effect of various carbon materials is beneficial to improve the conductivity of the material, and maintain the structural integrity during the cycle. The obtained N-SiOx/C@C anode exhibits high reversible capacity (980.2 mAh·g−1), excellent cycle stability (70 % capacity retention after 500 cycles at 0.5 A·g−1) and excellent rate performance (491.9 mAh·g−1 specific capacity of at 5 A·g−1). The strategy provided here effectively improves the electrochemical performances of SiOx, and the prepared materials show great application potential in the field of lithium ion batteries.

Critical assessment of the applicability of the Child-Langmuir law to plasma ion source extraction systems

Applicability of the classical one-dimensional and the recently developed multi-dimensional Child-Langmuir (CL) laws to plasma ion source extraction systems is studied. Experiments with a filament-driven multicusp ion source using a simplified extraction system, and comprehensive simulations with two different software packages, suggest that ion beams, which are typically assumed to be space charge or CL limited, are actually divergence-limited. In addition, it was observed that the dynamic plasma meniscus and geometric effects of the extraction system have a greater impact on the ion beam behavior than the effects predicted by the multi-dimensional CL law. Nevertheless, it was found that ion beams produced by the ion source exhibit space charge limited behavior, the beam current scaling with the extraction voltage as , provided that the entire beam is measured and its divergence is kept small and constant for each extraction voltage. This implies that the applicability of the CL law on a specific extraction system cannot be resolved by a straightforward voltage sweep and beam current measurement but instead, the plasma parameters must be adjusted for each extraction voltage. By shifting the focus from the CL limited framework to the divergence-limited framework, a clearer interpretation of the beam current–voltage characteristics of extraction systems can be achieved. This shift in perspective may also lead to the development of new design paradigms that can further enhance the performance of plasma ion source extraction systems.

First H- beam extracted from the non-caesiated external RF-coil ion source at ISIS

A high power, high duty-cycle, non-caesiated negative hydrogen ion source is in development at the ISIS pulsed spallation neutron and muon facility. Stable operation of an inductively-coupled plasma pulsing at 50 Hz, 1 ms, 70 kW has been perfected with no apparent lifetime issues. Novel features compared to similar H- sources include a very low power microwave ignition gun, an adjustable permanent magnet filter field and multiple large 3D-printed components. This paper details the initial commissioning efforts required to generate a beam. An H- beam current of 10 mA was extracted on the first try in pure volume-production mode. Parameter sweeps and optimisation to reach the required 35 mA were put on hold to address ancillary equipment problems. Mitigation of RF pickup required major mechanical changes such as additional screening and magnetic shielding. Extraction voltage holding capabilities were investigated to cope with co-extracted electron current loading in excess of 0.7 A. Preliminary studies of the biased plasma electrode current showed that co-extracted electrons could be suppressed by increasing the magnetic filter field and gas flow.