Gas Discharge Research Articles

Pulsed processing by cold plasma, applied to industrial emission control.

A promising pollution control technology is cold plasma driven chemical processing. The plasma is a pulsed electric gas discharge inside a near atmospheric-pressure-temperature reactor. The system is energized by a continuous stream of very short high-voltage pulses. The exhaust gas to be treated flows through the reactor. The methods applied involve the development of robust cold plasma systems, industrial applications and measuring technologies. Tests of the systems were performed at many industrial sites and involved control of airborne VOC (volatile organic compound) and odor. Electrical, chemical and odor measuring data were collected with state-of-the-art methods. To explain the test data an approximate solution of global reaction kinetics of pulsed plasma chemistry was developed. It involves the Lambert function and, for convenience, a simple approximation of it. The latter shows that the amount of removal, in good approximation, is a function of a single variable. This variable is electric plasma power divided by gas flow divided by input concentration. In the results sections we show that in some cases up to 99% of volatile pollution can be removed at an acceptable energy requirement. In the final sections we look into future efficiency enhancements by implementation of (sub)nanosecond pulsed plasma and solid state high-voltage technology and by integration with catalyst technology.

88‐2: The Characteristics Analysis for Laser Cutting Process of Multilayers Display Panels

In this study, we analyzed the laser cutting characteristics of pulse transverse electrical discharge in gas at atmospheric pressure (TEA) CO2 and ultraviolet (UV) pulse laser processing in a multilayer display panels. First, the numerical calculation for was performed to confirm the thermal characteristics of each materials and optical field distribution at the interface of different material layers. Also, processing characteristics were experimentally confirmed by measuring cutting profile and adhesion characteristics of layer interface. Experimental results show that the characteristics of multi layers polymer cutting have different trend from those in a single‐layer because of the optical and thermal properties of each layer. In particular, the interface of layers had a substantial affect due to optical field distributions and thermal characteristic difference. Also, the optical absorbance of layers affect adhesion at the interface. The result suggests proper processing condition to enhance the laser ablation processing quality of multilayer display panel. In conclusion, understanding the characteristics of multilayer laser cutting processing is important for determining the optimal conditions for display panel micromachining and enhancing the quality of laser cutting for the cutting edge technology.

Void closure in a pulsed complex plasma in microgravity

A new experimental method for creating void-free complex (dusty) plasmas under microgravity conditions is presented. The method is based on a pulsed operation mode of a four-channel radio frequency generator for plasma sustainment. A dust cloud of micrometer-sized particles can be immersed in the bulk of a low temperature plasma under microgravity conditions. It typically contains a central volume depleted of particles—the void—that prevents the generation of large, continuous clouds. Experiments performed at different neutral gas pressures and discharge volumes during the microgravity phase of a parabolic flight show that the central void is closed completely once the pulsed operation mode is applied. The particle cloud shape and the density distribution within the cloud are practically independent of the pulse period within the investigated parameter range and mainly depend on the overall discharge parameters neutral gas pressure and discharge volume. This indicates that the pulsed operation of the plasma source does not introduce new physical effects on the particles aside from the void closure. The proposed method has great potential for future application in experimental facilities dedicated to fundamental studies of large three-dimensional, homogeneous complex plasma systems in microgravity.

Parameters of dust particle chains levitated vertically in a gas discharge plasma

The structural parameters of the dust particle chains suspended vertically in the electric field of a gas discharge are studied here. The investigations are performed by a numerical multi-block model based on a mean field approximation. The model describes the movement of ions and dust particles under the action of an external electric field, the electric field (Coulomb) of each charged dust particle, and the field of bulk plasma charge (ions and electrons) that screens the charges of dust particles. The gravity and the ion drag forces acting on the dust particles are also taken into account. Self-consistent chain parameters are calculated and compared for different number (1, 3, 5, and 7) and two different diameters (3.4 and 8.94 mcm) of dust particles in the chains. It is shown that an “ion wake” is formed behind the dust structures, and it grows with the number of dust particles and their size. With an increase in the number of dust particles in the chain, the charge of the first (top) dust particle increases. In the case of small dust particles, with an addition of new particles into the chain, the centers of the chains almost remain at the position of a single particle in the vertical direction. The chains of big dust particles move as a whole down in the direction of gravity with an increase in the number of particles.

Electron trapping efficiency of a magnetron sputtering cathode

A common feature of all types of magnetron sputtering (MS) assemblies is an effective confinement of electrons by an appropriate combination of electric and magnetic fields. Therefore, studying the motions of electrons in the fields of magnetron assemblies is of particular importance. Here, we systematically analyze the electrons motions in front of a typical DC MS cathode. We first calculate the profiles of the magnetron’s magnetic field for balanced and two types of unbalanced configurations. Then, we compute the profiles of the cathode’s electric field before the gas discharge and after the plasma formation. A semi-analytical model is utilized to compute the plasma potential. We then track the motions of electrons released from the target and electrons produced through impact ionization of the background gas in the prescribed fields. A Monte Carlo model is implemented to consider electron-gas collisions and a mixed boundary condition is employed to account for electron-wall interactions. The study analyzes the impact of field profiles on the cathode’s efficiency in trapping electron by examining electron escape from the magnetic trap and electron recapture at the target surface. It is shown that the presence of plasma in all configurations leads to a significant increase in the trapping efficiency and the ionization performance, as well as a decrease in the recapture probability. These effects are attributed to the high electric field developed in the cathode sheath. Moreover, we statistically analyze the trapping efficiency by illustrating the spatial distributions of electrons locations in both axial and radial dimensions. It is demonstrated that during their azimuthal drift motion, the electrons released from the middle region at the target surface have the smallest range of axial and radial locations, in all configurations in the absence of plasma. Finally, the impact of field profiles on the average energies of electrons is discussed.

Generation of low-energy abundant electron energy probability functions using a magnetized plasma source

The generation of low-energy electrons is essential for the plasma source of the charge neutralizer system within the ion implanter process of semiconductors and displays, owing to their exceptional capability of being effectively transported along their ion beams. In this study, we propose a method to produce non-Maxwellian electron energy probability functions (eepfs) characterized by low-energy-abundant electrons, specifically below 5 eV, across an electron extraction system. In the electron transport region with an axial magnetic field under conditions of high discharge voltage and gas flow rate, we observed a significant increase in low-energy electrons in eepfs. The simple global model proposed to analyze these results demonstrated that the wall loss of electrons can be reduced by an elevated plasma potential, which is influenced by the ionization rate in the transport region. These results are consistent with the experimentally measured plasma potential and electron density. Additionally, the reduction in wall losses and increased ionization rate within the transport region resulted in the relaxation of the plasma potential gradient. This phenomenon effectively inhibited the cutting of low-energy electrons within the eepfs, thereby facilitating their consequential transport to the target. This study emphasizes the significance of increasing the ionization rate and minimizing the potential gradient for the dual purposes of generating low-energy electrons and directing them towards the target.

A hot, hydrothermally influenced microbial-tidal flat setting in the Palaeoarchaean Moodies Group, Barberton Greenstone Belt, South Africa

Abstract Sandy, microbial-mat-laminated sediments are common in estuarine and tidal environments of the Palaeoarchean Moodies Group (ca. 3.22 Ga); they are interspersed with numerous expressions of mafic to intermediate (sub-) volcanism, including sills, stockwork dykes, lavas, and air-fall tuffs. We describe abundant fluid-escape structures up to 6 m in height associated with this facies in the Saddleback Syncline of the central Barberton Greenstone Belt. The fluid-escape conduits fed small sand volcanoes during prolonged and/or recurring discharge of gases, liquids, and solids. They are filled by sand, sericitic clay, and fine-grained organic matter of former microbial mats. In comparison to the mean composition of adjacent beds of identical composition, the conduits are enriched in Fe, Cr, Ti, and Mg. This suggests that fluid-escape was not only a consequence of overpressure buildup from decaying microbial mats in the shallow subsurface or of water-level fluctuations but also due to periodic or continuous release of hydrothermal fluids circulating in the thermal aureole above the cooling Lomati River Sill of Moodies age. Such an inference is also supported by textures characteristic of in-place argillaceous and sericitic alteration and by Raman spectroscopy of carbonaceous matter (RSCM) indicating temperatures ca. 50 to 100°C above the regional maximum metamorphic temperature of 320 to 380°C. Pre-compaction carbonate and/or silica cementation also preserved the abundant carbonaceous laminae interpreted as benthic microbial mats. Analogue recent hot spring deposits suggest that surficial hydrothermal activity in the medium-energy siliciclastic tidal zone would have significantly boosted microbial growth.

Validation of the thermo-chemical approach to modelling of CO2 conversion in sub-atmospheric pressure microwave gas discharges

The CO 2→ CO + 12 O2 conversion experiment [D’Isa et al 2020 Plasma Sources Sci. Technol. 29 105009] has been compared with thermo-chemical calculations. The experiment is a 2.45 GHz plasma torch with a straight channel in the effluent. The 1.5D model of the CO2/CO/O2/O/C mixture without turbulent transport has been applied with plasma acting only as a prescribed heat source. The parameter range covered is the specific energy input (SEI) 0.3–5 eV/molecule at pressure p = 0.9 bar, and SEI = 0.6–2 eV/molecule at p = 0.5, 0.2 bar. The calculated conversion χ is always close to the experimental values. At the same time, the calculated temperatures T deviate significantly from the experiment, especially for p = 0.2 bar. The calculated T were also found to be sensitive with respect to the uncertain model parameters, but χ is not sensitive. The net conversion in the model is driven to a large extent by the radial diffusion of CO and O from the hot core towards the wall and steep radial temperature gradients. The main factor that reduces the energy efficiency is the re-oxidation of CO at the edge of the hot plasma region and downstream. The 1.5D approximation applied has the principle limitation that the impact of a realistic bulk flow field on the chemical process cannot be studied. Hence, the results must be considered preliminary and have to be confirmed with a more elaborate and accurate model of the vortex-stabilized flow inside the reactor.

A high-efficiency room-temperature surface wave plasma jet based on a rectangular waveguide

Microwave plasma jets have garnered significant attention due to their unique advantages and wide applications in numerous fields. However, the frequent collisions between electrons and neutral particles at atmospheric pressure make it challenging to generate a room-temperature plasma jet and maintain a high energy efficiency at the same time. This paper introduces a new microwave plasma jet based on a rectangular waveguide, which utilizes the surface wave propagating along the plasma jet to sustain the gas discharge. It features a simple structure, low power consumption, high energy efficiency, and strong controllability without the need for any external tuning measures. The minimum power required to ignite and stably maintain the plasma jet at atmospheric pressure is as low as 25 W and the measured lowest gas temperature at the plasma jet tail is approximately 295 K. Meanwhile, experiments show the microwave energy efficiency can be higher than 90% in a large range of input powers and gas inflow rates, while the gas temperature is maintained close to room temperature. These characteristics of our proposed surface wave plasma jet demonstrate tremendous potential in fields such as hemostasis, sterilization, wastewater treatment, semiconductor cleaning, and material processing.

Energy assessment in rural regions of China with various scenarios: Historical–to–futuristic

Approximately 172 million rural households in China in 2022, will still rely on traditional biofuels instead of electricity. This study explores the feasibility of achieving rural electrification in China utilization various Energy origins and assesses its potential impact on climate change mitigation. To do so, we employ the Regional Energy Model (REM) to formulate hypotheses for rural power distribution. Covering the era from 2020 until 2050. We evaluate consequences in terms of greenhouse gas discharges, principal energy consumption, associated expenses by comparing these possibilities with a Business-as-Usual (BU) scenario. Our findings reveal that diesel-based arrangements tend to produce ‘the maximum Carbon Dioxide (CO2) emissions, trailed by network-based solutions. Electrification focused on renewable energy-driven applications has the potential to reduce total CO2 emissions by up to 97 % and primary energy consumption by 43 % in 2050 compared to the BU scenario. We also find that electrification through decentralized diesel systems tends to be the priciest choice. Rural electrification utilizing renewable energy emerges as a cost-effective choice when the majority of end-use applications rely on renewable energy sources. However, it becomes less economical than network expansions when electric end-user appliances are predominant. In summary, this study investigates the viability of renewable energy for rural power distribution and its role in climate change abatement in rural China, offering policy suggestions.

Formation of Black Silicon in a Process of Plasma Etching with Passivation in a SF6/O2 Gas Mixture.

This article discusses a method for forming black silicon using plasma etching at a sample temperature range from -20 °C to +20 °C in a mixture of oxygen and sulfur hexafluoride. The surface morphology of the resulting structures, the autocorrelation function of surface features, and reflectivity were studied depending on the process parameters-the composition of the plasma mixture, temperature and other discharge parameters (radical concentrations). The relationship between these parameters and the concentrations of oxygen and fluorine radicals in plasma is shown. A novel approach has been studied to reduce the reflectance using conformal bilayer dielectric coatings deposited by atomic layer deposition. The reflectivity of the resulting black silicon was studied in a wide spectral range from 400 to 900 nm. As a result of the research, technologies for creating black silicon on silicon wafers with a diameter of 200 mm have been proposed, and the structure formation process takes no more than 5 min. The resulting structures are an example of the self-formation of nanostructures due to anisotropic etching in a gas discharge plasma. This material has high mechanical, chemical and thermal stability and can be used as an antireflective coating, in structures requiring a developed surface-photovoltaics, supercapacitors, catalysts, and antibacterial surfaces.

Evaluating the use of three-dimensional reconstruction visualization technology for precise laparoscopic resection in gastroesophageal junction cancer.

Laparoscopic gastrectomy for esophagogastric junction (EGJ) carcinoma enables the removal of the carcinoma at the junction between the stomach and esophagus while preserving the gastric function, thereby providing patients with better treatment outcomes and quality of life. Nonetheless, this surgical technique also presents some challenges and limitations. Therefore, three-dimensional reconstruction visualization technology (3D RVT) has been introduced into the procedure, providing doctors with more comprehensive and intuitive anatomical information that helps with surgical planning, navigation, and outcome evaluation. To discuss the application and advantages of 3D RVT in precise laparoscopic resection of EGJ carcinomas. Data were obtained from the electronic or paper-based medical records at The First Affiliated Hospital of Hebei North University from January 2020 to June 2022. A total of 120 patients diagnosed with EGJ carcinoma were included in the study. Of these, 68 underwent laparoscopic resection after computed tomography (CT)-enhanced scanning and were categorized into the 2D group, whereas 52 underwent laparoscopic resection after CT-enhanced scanning and 3D RVT and were categorized into the 3D group. This study had two outcome measures: the deviation between tumor-related factors (such as maximum tumor diameter and infiltration length) in 3D RVT and clinical reality, and surgical outcome indicators (such as operative time, intraoperative blood loss, number of lymph node dissections, R0 resection rate, postoperative hospital stay, postoperative gas discharge time, drainage tube removal time, and related complications) between the 2D and 3D groups. Among patients included in the 3D group, 27 had a maximum tumor diameter of less than 3 cm, whereas 25 had a diameter of 3 cm or more. In actual surgical observations, 24 had a diameter of less than 3 cm, whereas 28 had a diameter of 3 cm or more. The findings were consistent between the two methods (χ2 = 0.346, P = 0.556), with a kappa consistency coefficient of 0.808. With respect to infiltration length, in the 3D group, 23 patients had a length of less than 5 cm, whereas 29 had a length of 5 cm or more. In actual surgical observations, 20 cases had a length of less than 5 cm, whereas 32 had a length of 5 cm or more. The findings were consistent between the two methods (χ2 = 0.357, P = 0.550), with a kappa consistency coefficient of 0.486. Pearson correlation analysis showed that the maximum tumor diameter and infiltration length measured using 3D RVT were positively correlated with clinical observations during surgery (r = 0.814 and 0.490, both P < 0.05). The 3D group had a shorter operative time (157.02 ± 8.38 vs 183.16 ± 23.87), less intraoperative blood loss (83.65 ± 14.22 vs 110.94 ± 22.05), and higher number of lymph node dissections (28.98 ± 2.82 vs 23.56 ± 2.77) and R0 resection rate (80.77% vs 61.64%) than the 2D group. Furthermore, the 3D group had shorter hospital stay [8 (8, 9) vs 13 (14, 16)], time to gas passage [3 (3, 4) vs 4 (5, 5)], and drainage tube removal time [4 (4, 5) vs 6 (6, 7)] than the 2D group. The complication rate was lower in the 3D group (11.54%) than in the 2D group (26.47%) (χ2 = 4.106, P < 0.05). Using 3D RVT, doctors can gain a more comprehensive and intuitive understanding of the anatomy and related lesions of EGJ carcinomas, thus enabling more accurate surgical planning.

Analysis and NDT applications of a gas discharge electroacoustic transducer

In this study, a gas discharge electroacoustic transducer (GDEAT) based on a pulsed electric discharge in the air under atmospheric pressure has been investigated. By evaluating acoustic pressure and recording amplitude-frequency characteristics of membranes, the acoustic characteristic of GDEATs have been obtained in the frequency range from 40 Hz to 4 MHz. The electro-thermo-acoustic processes have been studied in gas discharge systems of an open type where the electrode space is in a direct contact with the ambient. Some features of using the above-mentioned GDEATs in nondestructive testing (NDT) of materials have been demonstrated. It has been shown that, on one hand, the wear of both electrodes and insulation limits a work life of a transducer electrode system, but, from the other hand, this may lead to deposition of micro-particles on the surface of an object under test. The wear of electrode systems was evaluated quantitatively, and the results of the chemical analysis of deposited micro-particles have been presented. The use of a GDEATs for non-contact stimulation of local resonant vibrations in subsurface defects and visualizing vibrations by means of laser dopler vibrometry has been shown in the case of NDT of a glass fiber composite.

Properties of the ionization region in a magnetron plasma at gas-aggregation-source-relevant pressure regime explored using a global model

A global (volume averaged) model is developed for the ionization region (IR) of a gas aggregation source (GAS) plasma. The case of using argon gas and a copper target is considered. The model describes the densities of thermal and hot electrons, argon and copper ions, copper atoms and argon atoms in different excited states, the temperature of thermal electrons, the kinetic energies of the ions with which they bombard the target, the sheath width near the target cathode and the energy fluxes by different plasma species to a planar probe in the IR. Also, the fraction of input power is estimated which is dissipated to energize the thermal electrons in the IR. The gas discharge properties are analyzed for different pressures and discharge currents under conditions corresponding to the experimental conditions (Gauter et al 2018 J. Appl. Phys. 124 073301). The calculated pressure- and current-dependences for the GAS properties are used to explain the measured dependences for the deposition rate and the energy flux. It is found that the deposition rate increases with increasing discharge current because of the growth of currents of copper atoms and ions. With increasing pressure, the rate decreases due to drop of the densities of copper atoms and ions because of decreasing the kinetic energies of the ions with which they bombard the target. The model indicates that in the gas-aggregation-source relevant pressure regime, the energy flux by ions dominates over the energy fluxes of other plasma species.

Investigation of the cross sections for electron collision ionization of complex molecules

AbstractAn accurate and computationally efficient determination of the cross sections for electron collision ionization of molecules has various applications, such as plasma physics and atmospheric science. In the case of large molecules, ab initio calculations are often difficult and time‐consuming. Here, we develop a feed forward neural network to predict the electron impact ionization cross sections of complex molecules. The training (predicting) set in the method consists of a series of theoretical ionization cross sections for small (large) molecules obtained from the combined model, which integrates the Binary‐Encounter‐Bethe and Deutsch‐Märk models. Several complex systems or targets involving electron collision ionization are evaluated, including molecules such as CH, CH, CH, CH, C, CHO, and CHO. The root mean square errors of the trained and predicted cross sections by the neural network (compared to the values from the combined model) are found to be approximately .0086 and .0930 (in 10 cm), respectively, (using the CHO molecule as an example), indicating our results are very high accuracy. The excellent agreement between the predicted values and the actual values indicates that the neural network is a practical and powerful tool for determining the electron collision ionization cross sections of complex molecules and can provide valuable insights into the dynamics process. Apart from its fundamental importance, this study has far‐reaching implications for gas discharge, low‐temperature plasmas, and fusion edge plasmas and so forth.

Investigating the impact of X-ray irradiation on the SF6 gas discharge in GIS equipment

ABSTRACT Gas Insulated Switchgear (GIS) is extensively utilized in power grid systems. However, the existence of numerous photoelectrons in the SF6 gas during X-ray non-destructive testing in ultra-high-voltage (UHV) GIS equipment may induce gas streamer discharge in a strong electric field. To address this issue, in this work, the impact of X-ray irradiation on the SF6 gas discharge in GIS equipment was systematically analyzed. Firstly, one GIS engineering mode with a three-dimensional electric field was established, and a physical GIS model was established by the Geant4 and Garfield++ codes. Secondly, the electrons’ ionization, and multiplication processes in SF6 gas during the X-ray irradiation were studied. Finally, a test platform with an equivalent electric field tube, which had the same intensity as in the GIS equipment, was established to verify the physical GIS model. X-ray beams with 0.1 MeV, 0.16 MeV, 0.3 MeV, and 1.25 MeV energy were used during the test process. From our analysis, it was concluded that X-ray irradiation can cause an electron avalanche in SF6 gas and the intensity of the avalanche is low, which is far away from the appearance of the streamer discharge.

Utility of argon as a static charge and wall fouling suppressant in atmospheric gas-solid fluidized beds

This work aimed to study the usability of argon to mitigate electrostatic charging and fouling of polyethylene resin fluidized in a stainless-steel column. Nitrogen, argon, and their binary mixtures of various concentrations were utilized to fluidize polyethylene. Successive and intermittent fluidizations with argon and nitrogen were also carried out to explore the feasibility of using argon in commercial reactors. Fluidization with pure argon resulted in the lowest specific charge and substantially reduced the fouling by 90% relative to pure nitrogen. The results for the mixture trials showed a decreasing non-linear trend as the concentration of argon increased. Even presence of 10 vol% argon in the mixture reduced the wall fouling by 50%. Successive and intermittent fluidization also yielded fouling and specific charge values comparable to pure argon. The results are attributed to argon's relatively low dielectric strength and subsequent localized gas discharge within the particle-dense section of the bed.

Research on the thermal runaway characteristics and risks of square soft lithium‐ion batteries nail penetration

AbstractTo conduct a comprehensive investigation into the nail penetration thermal runaway (TR) characteristics of 16 Ah/5 Ah lithium‐ion batteries (LIBs) and their modules. The study aims to analyze the burst characteristics and examine the variations in TR behavior under specific conditions, with the goal of improving early warning and protection against LIB TR incidents. The research findings demonstrate that mechanical nail penetration can rapidly trigger TR, resulting in the highest temperature 522.3°C within 51.9 s, and the fastest is 20 s. In the case of LIB modules, a secondary temperature rise occurs, exhibiting an increased rate of up to 77%. Notably, when the battery bulges, there is a release of high‐temperature two‐phase heat flow accompanied by a significant discharge of combustible gases. This escalation increases the risk of further explosions. Moreover, the study observes repeated spray fires and the generation of a considerable amount of smoke. Additionally, the study highlights the role of sudden rise in temperature and the release of H2 as early indicators of TR. These findings provide valuable theoretical insights into the characteristics and risks of square soft LIBs, enhance safety measures, and contribute to the development of early warning systems for LIBs.

Mitigating greenhouse gas emissions from sheep production system in China: An integrated approach of data envelopment analysis and life cycle assessment

Over the past decades, the global population has significantly increased, resulting in high demand for food. China, the largest sheep-producing country, has experienced 20 rapid expansions in its sheep industry, which has caused environmental consequences. This study proposes an integrated approach that combines data envelopment analysis (DEA) and life cycle assessment (LCA) to assess the ecological consequences of the sheep production system. Therefore, this work aims to evaluate the energy consumption of the existing production system and identify optimization opportunities to reduce its environmental impacts. Our results demonstrate that sheep production can decrease total energy consumption by 9.82% using optimization. Food production was reported as a critical factor in environmental impact, responsible for 69%. However, the optimized approach led to a decrease of 4,677.64 MJ in energy consumption in sheep production compared to the initial state. The findings of this study showcase the possibility of decreasing energy usage and lessening greenhouse gas (GHG) discharges in sheep farming by implementing optimization strategies.

Determination of gas discharge plasma potential by Langmuir probe using different methods

In a hollow cathode discharge in helium at reduced pressure, the profile of the plasma potential Up in the cathode-anode region was measured with a single Langmuir probe. A digital technique was used to control and analyze the experimental results. The probe current-voltage characteristic was generated by applying a voltage with a spectrum with an equal probability distribution in the measured voltage range. Three methods were compared: (1) differentiation of the probe current-voltage characteristic (IVC) by the Langmuir-Druyvesteyn (LD) method with the Savitsky-Golay (SG) filter; (2) definition of the position of the noise maximum in the experimental IVC; (3) determination of the voltage corresponding to the intersection of the asymptotes of different range of the IVC. Methods (2) and (3) were used both as alternatives to method (1) for measuring the potential Up and as additional ones when choosing free parameters of the SG filter for plasma diagnostics by method (1).