Search

Herein, we investigated the effect of a dielectric film on the transmission spectrum of a bar-type flat cutoff probe (BCP). By conducting electromagnetic wave simulations, we found that placing a dielectric film with a thickness of 1 mm or less on the sensor did not affect the measurement of the BCP under thin sheath condition. However, a film thickness of 1 mm or more results in a low-frequency shift in the cutoff frequency. The shift in the cutoff frequency was related not only to the film thickness, but also to the dielectric constant of the film and sheath width, which could be understood through a circuit model of the BCP. The calculated results were experimentally validated using alumina plates of various thicknesses. Consequently, our findings demonstrate that measuring the electron density on a BCP is feasible even when a dielectric film is deposited, thereby improving the accuracy of the measurement. [ABSTRACT FROM AUTHOR]

Electrical and fast imaging measurements are performed on an experimental device designed to study the dynamics of electric arcs in the DC regime. The work presented here investigates the relationship between electrical fluctuations and material ejection from the electrode surface. Cross-analysis of the electrical and imaging data reveals a significant correlation between electrical fluctuations in the kHz range and particle emission from the electrode surface. Different types of ejection are presented and a study of the dynamics of the ejected particles is carried out through the analysis of a statistically significant number of trajectories. [ABSTRACT FROM AUTHOR]

A new method is proposed for measuring the electron plasma temperature at the GOL-NB facility. The method is based on measuring the ratio between the intensities of the spectral lines emitted by the fast atoms injected into the plasma. The beams of fast hydrogen atoms used for heating the plasma at the GOL-NB facility contain not only atoms with a full energy (E) but also atoms with fractional energies (E/2, E/3, E/18) that appear as a result of the dissociation of the H , H , and H2O+ molecular ions. The spectral lines of the beam components with these energies (and, in particular, the hydrogen Hα line) can be resolved due to the Doppler shift caused by the difference between the atom speeds. For atoms with low energy, the excitation that leads to the photon emission occurs only due to their collisions with thermal electrons, while for atoms with high energy, a sufficient deposition into their excitation is given by their collisions with the plasma ions. This is why the ratio between the intensities of the lines of different beam components depends on the plasma electron temperature, and thus, it can be used to measure this temperature. At the beam energy of 24 keV, the proposed method can be used to measure the electron temperature in the range of up to 40 eV, which is of interest for the current experiments conducted at the GOL-NB facility. Note that measurement of the electron temperature higher than 20 eV requires that the ratio between the spectral line intensities be measured with an accuracy of the order of one percent, and that the attenuation of the neutral beam that passes through the plasma be measured with the same accuracy. The proposed method can be used at other fusion facilities that use fast hydrogen atom injection to measure the temperature of the edge plasma. [ABSTRACT FROM AUTHOR]

In this paper, the Magnetically Stabilized Gliding Arc Discharge (MSGAD) system was constructed to produce non-thermal plasma using argon gas under atmospheric pressure. A gliding plasma discharge was stabilized by a magnetic field for the purpose of a planned investigation. The emission spectra of the generated plasma using a gliding arc discharge system were recorded under atmospheric pressure, with a constant value of alternating voltage (4 kV) and at different gas flow rates of) 0.5–2.5 (L/min. The plasma parameters, including electron temperature (Te), electron density (ne), plasma frequency, Debye length and electron temperature, were calculated. The electron temperature was measured using the Boltzmann plot method, and the electron density was determined using the Stark broadening method. The results show an increase of the electron temperature from 1.138 to 1.277eV and electron density from 2.78×1017 to 3.48×1017 cm-3 as the gas flow increased from 0.5 to 2.5 L/min. Also, the spectral line intensity increases with the increase of the gas flow rate. [ABSTRACT FROM AUTHOR]

Abstract The wide variety and ever-growing applications of plasma processes in research and industry require an equally growing diversity and accessibility of suitable plasma diagnostics. The plasma parameters and the tailoring thereof strongly influence the outcome of thin film deposition, plasma etching, or surface treatments, to name only a few. To further enhance the determination of different fluxes of species, their energies, and behaviour influencing a surface process, a custom-built combination of two commonly used diagnostics was developed. With a retarding field energy analyzer, one can obtain the ion energy distribution in a plasma by measuring the current at the collector depending on the applied voltage at the scan grid. A passive thermal probe determines the energy flux density coming from a process plasma by measuring the temperature change of a dummy substrate. In this study, we present a retarding field energy analyzer where a passive thermal probe substitutes the collector. By doing so, we can determine the energy distribution of the charged ions, their energy flux density at a certain potential, and the power deposited onto a substrate. Another advantage is that the thermal probe can even measure the power deposited by incoming (fast) neutrals and of the background gas when the grids keep away the ions. Hence, combining these two powerful diagnostics yields information neither can deliver on their own. The probe has been tested in three different plasma environments: ion beam source, magnetron sputtering and radio frequency discharge plasma.

This study aims to investigate the aluminum (Al) arc plasma parameters generated through the explosive strip technique. The research involves the measurement of key plasma characteristics such as plasma frequency (fp), Debye length, and Debye number. The electron temperature (Te) and electron density (ne) of the plasma were calculated utilizing the Boltzmann plot and Stark expansion method. Analysis of the optical emission spectrum revealed distinctive peaks corresponding to oxygen, Al, and zinc oxide (ZnO) within the plasma. The outcomes of the study demonstrated a noteworthy correlation between the applied current and the electron temperature and density. Specifically, as the current increases, both electron temperature and density increase. The electron temperature of the Al plasma increased from the range of 0.852 eV to 0.92404 eV, accompanied by a corresponding elevation in electron density from 13.1x 1017 cm-3 to 15.2x 1017 cm-3. Furthermore, the detonation of the Al strip within a ZnO suspension led to even more pronounced changes. In this case, the electron temperature surged from 0.92885 eV to 1.1012 eV, and the electron density experienced an increase from 37.7 x 1017 cm-3 to 44.7 x 1017 cm-3. [ABSTRACT FROM AUTHOR]

diagnostics of the plasma electron component by the metho d of Thomson scattering Te(R, t) of laser radiation makes it possible to reliably measure the spatial distributions of the electron temperature and density. One of the obstacles to the implementation of TS diagnostics in thermonuclear reactors is the distortion of the spectral characteristics of the optical system due to radiation-induced absorption and contamination of optical elements with erosion products of the first wall. As a consequence, the reliability of measurements by the TS method will decrease over time. The paper describes the method of multi-laser Thomson scattering, which will solve this problem. The results of the first experiments on the Globus-M2 tokamak are also presented. [ABSTRACT FROM AUTHOR]

The wide variety and ever-growing applications of plasma processes in research and industry require an equally growing diversity and accessibility of suitable plasma diagnostics. The plasma parameters and the tailoring thereof strongly influence the outcome of thin film deposition, plasma etching, or surface treatments, to name only a few. To further enhance the determination of different fluxes of species, their energies, and behaviour influencing a surface process, a custom-built combination of two commonly used diagnostics was developed. With a retarding field energy analyzer, one can obtain the ion energy distribution in a plasma by measuring the current at the collector depending on the applied voltage at the scan grid. A passive thermal probe determines the energy flux density coming from a process plasma by measuring the temperature change of a dummy substrate. In this study, we present a retarding field energy analyzer where a passive thermal probe substitutes the collector. By doing so, we can determine the energy distribution of the charged ions, their energy flux density at a certain potential, and the power deposited onto a substrate. Another advantage is that the thermal probe can even measure the power deposited by incoming (fast) neutrals and of the background gas when the grids keep away the ions. Hence, combining these two powerful diagnostics yields information neither can deliver on their own. The probe has been tested in three different plasma environments: ion beam source, magnetron sputtering and radio frequency discharge plasma. [ABSTRACT FROM AUTHOR]

Sputtering is the process of depositing thin films on the surface of a material using plasma. Plasma is created by adding extremely high energy to a surrounding gas, which turns into plasma. The plasma is directed towards the material on which you want to deposit the films, and the plasma particles interact with the material to form a thin film of the desired material. Oxygen plasma has many important applications in industry. When adding a small percentage of it, it can change the properties of the plasma significantly. In this research, the spectrum of the plasma generated from the application of different energies (175,200,250,300) watts of direct current was studied on a mixture of argon and oxygen gases in a ratio of (9: 1). The spectrum emitted from the plasma was measured Within the wavelength range (400-800) nm, the plasma parameters (Te, ne, λD, ND) were diagnosed by examining the spectrum corresponding to the applied power using optical emission spectroscopy (OES). The results showed an increase in the electron temperature and electron density with the increase in the applied power. Where the highest and lowest values for the electron temperature and density were respectively (1.645-1.305) eV, (26.03-25.36) x 1017/cm3.

The incorporation of oxygen and/or nitrogen into the titanium lattice has garnered significant attention due to the broad spectrum of intermediate properties that can be achieved between TiN and TiO2. This article delves into the investigation of surface modification of titanium through plasma-assisted thermochemical treatments employing H2-N2-O2 mixtures. The flow rate of the reducing gas (H2) remained constant at 24 sccm, while the flow rates of N2 and O2 were adjusted to yield a total flow rate of 60 sccm. Analysis using GIXRD, Raman spectroscopy, and XPS demonstrated that TiN exhibits stability exclusively in an oxygen-free atmosphere, while TiO2, in contrast, necessitates an oxygen flux equal to or exceeding 18 sccm for stability. Furthermore, it was found that the presence of nitrogen in the plasma atmosphere resulted in a greater expansion of the α-titanium lattice, although the solubility of interstitials decreased. These findings highlight the potential for a controlled approach to producing solid solutions or titanium oxynitrides.

Copyright of Al-Mustansiriyah Journal of Science is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper aims to design and construct a Langmuir probe diagnostic system for plasma parameters measurement in the Iranian Inertial Electrostatic Confinement Fusion (IR-IECF) device. For this purpose, a Langmuir probe diagnostic system is designed and constructed to determine the plasma parameters such as temperature, ion and electron density, and potential. Considering the characteristic of the plasma source of IR-IECF, the electrode selected for the probe is a tungsten wire with a diameter and length of 0.3 and 1.5mm, respectively, protected by an alumina ceramic tube with an inner diameter of 0.7cm. The connections and probe holder base on the vacuum chamber are stainless steel. The electrical circuit of the probe provides voltage and current of 500v and 1mA, respectively. The obtained results demonstrate that between two electrodes and at a distance of 25mm from the external electrode, the electron temperature, the electron density, the plasma potential, and the ion density are 50.1 eV, 3.1×1015 1/m3, 198V, and 0.4×1015 1/m3, respectively.

This work introduces a method for plasma state supervision, based on a frequency-modulated continuous wave radar sensor and a suitable signal evaluation enabling a continuous supervision method for the plasma state. Highly precise phase evaluation of the signal allows us to detect and visualize smallest changes in the plasma state. Assuming the plasma to act like a frequency-dependent dielectric material, the propagation of the electromagnetic wave depends on the plasma state and hence, also the measured phase. Broadband measurements are carried out at center frequencies of 80 and 140 GHz in a low-pressure plasma. The radar-based setup can be used for a very flexible application, capable for spatially resolved measurements in the plasma bulk. At the same time, the high measurement rate allows for quasi real-time monitoring, so that transient processes in the plasma are recorded. Due to the simple setup, this approach is most suitable for industrial applications to improve process control. The chosen different frequencies will show a change in the influence of the plasma on the electromagnetic wave demonstrating the advantages of multi-frequency approaches in future applications. [ABSTRACT FROM AUTHOR]

Among the characteristics of the low-temperature plasma often used in semiconductor processes, electron density plays an important role for understanding the plasma physics. Therefore, various studies involving invasive and non-invasive methods have been conducted to measure the electron density. This study aims to verify the possibility of measuring the electron density by simultaneously utilizing the characteristics of both invasive and non-invasive methods using a reflectometer attached to a commercial Wi-Fi antenna on a wafer in the vacuum chamber. The electron density was additionally measured using an interferometer and a single Langmuir probe under the same experimental conditions to assess the reliability of the reflectometer results, and the results were compared. The experiments were performed by increasing the 13.56 MHz radio frequency power applied to generate the plasma discharge in the 300 mm inductively coupled plasma bevel etcher equipment from 200 W to 400 W and 600 W, respectively. The electron densities measured using the three measurement methods (reflectometer/interferometer/single Langmuir probe) were confirmed to be in excellent agreement. Hence, the in-situ reflectometer on the wafer was verified to produce reliable results. [ABSTRACT FROM AUTHOR]

The construction and operation of the first generation of magnetically controlled nuclear fusion power plants require the development of proper physics and the engineering bases. The analysis of data, recently collected by the actual largest and most important tokamak in the world JET, that has successfully completed his second deuterium and tritium campaign in 2021 (DTE2) with a full ITER like wall main chamber, has provided an important consolidation of the ITER physics basis. Thermonuclear plasmas are highly nonlinear systems characterized by the need of numerous diagnostics to measure physical quantities to guide, through proper control schemes, external actuators. Both modelling and machine learning approaches are required to maximize the physical understanding of plasma dynamics and at the same time, engineering challenges have to be faced. Fusion experiments are indeed extremely hostile environments for plasma facing materials (PFM) and plasma-facing components (PFC), both in terms of neutron, thermal loads and mechanical stresses that the components have to face during either steady operation or off-normal events. Efforts are therefore spent by the community to reach the ultimate goal ahead: turning on the first nuclear fusion power plant, DEMO, by 2050. This editorial is dedicated at reviewing some aspects touched in recent studies developed in this dynamic, challenging project, collected by the special issue titled "New Challenges in Nuclear Fusion Reactors: From Data Analysis to Materials and Manufacturing". [ABSTRACT FROM AUTHOR]

Providing energy from fusion and finding ways to scale up the fusion process to commercial proportions in an efficient, economical, and environmentally benign way is one of the grand challenges for engineering. Controlling the burning plasma in real-time is one of the critical issues that need to be addressed. Plasma Position Reflectometry (PPR) is expected to have an important role in next-generation fusion machines, such as DEMO, as a diagnostic to monitor the position and shape of the plasma continuously, complementing magnetic diagnostics. The reflectometry diagnostic uses radar science methods in the microwave and millimetre wave frequency ranges and is envisaged to measure the radial edge density profile at several poloidal angles providing data for the feedback control of the plasma position and shape. While significant steps have already been given to accomplish that goal, with proof of concept tested first in ASDEX-Upgrade and afterward in COMPASS, important, ground-breaking work is still ongoing. The Divertor Test Tokamak (DTT) facility presents itself as the appropriate future fusion device to implement, develop, and test a PPR system, thus contributing to building a knowledge database in plasma position reflectometry required for its application in DEMO. At DEMO, the PPR diagnostic's in-vessel antennas and waveguides, as well as the magnetic diagnostics, may be exposed to neutron irradiation fluences 5 to 50 times greater than those experienced by ITER. In the event of failure of either the magnetic or microwave diagnostics, the equilibrium control of the DEMO plasma may be jeopardized. It is, therefore, imperative to ensure that these systems are designed in such a way that they can be replaced if necessary. To perform reflectometry measurements at the 16 envisaged poloidal locations in DEMO, plasma-facing antennas and waveguides are needed to route the microwaves between the plasma through the DEMO upper ports (UPs) to the diagnostic hall. The main integration approach for this diagnostic is to incorporate these groups of antennas and waveguides into a diagnostics slim cassette (DSC), which is a dedicated complete poloidal segment specifically designed to be integrated with the water-cooled lithium lead (WCLL) breeding blanket system. This contribution presents the multiple engineering and physics challenges addressed while designing reflectometry diagnostics using radio science techniques. Namely, short-range dedicated radars for plasma position and shape control in future fusion experiments, the advances enabled by the designs for ITER and DEMO, and the future perspectives. One key development is in electronics, aiming at an advanced compact coherent fast frequency sweeping RF back-end [23–100 GHz in few μs] that is being developed at IPFN-IST using commercial Monolithic Microwave Integrated Circuits (MMIC). The compactness of this back-end design is crucial for the successful integration of many measurement channels in the reduced space available in future fusion machines. Prototype tests of these devices are foreseen to be performed in current nuclear fusion machines. [ABSTRACT FROM AUTHOR]

• At present, there is no diagnostic for measuring electron temperature in the divertor region (i.e. among the X-point and the target plate) on the experimental advanced superconducting tokamak (EAST) device. It is motivated to develop a new diagnostics for the measurement electron temperature in the divertor region. In this work, a multi-spectral EUV imaging (MEUVI) diagnostics based on mirror arrays for electron temperature measurement by using line intensity ratio is proposed and being developed on the EAST. The MEUVI system can measure specific impurity emission lines. • In the commissioning phase, it is installed to monitor the plasma from the low-field side to the high-field side along the major radius rather than the divertor region. In this manuScript, we would like to report the first imaging data obtained by MEUVI during the commissioning in the 2024 experiment campaign. • In addition, the electron temperature derived from the MEUVI data is higher than that given by the helium beam emission (He-BES) spectroScopy system since the ne VIII emission is mainly located inside the last closed surface region. However, the tendency of the evolution of the electron temperature is consistent each other, which are given by these two systems. • These results verify that the MEUVI diagnostics can work as a potential tool for the measurement of edge plasma temperature and monitoring of impurities. A multi-spectral extreme ultraviolet imaging (MEUVI) diagnostics to measure impurity line emissions on the Experimental Advanced Superconducting Tokamak (EAST) is proposed and being developed to measure the electron temperature at the edge region. It makes use of multi-channel multilayers Schwarzschild telescope, coupled with a micro-channel plate (MCP) equipped with a P46 phosphor screen, and a high-speed camera with a CMOS sensor to image the selected line emissions, i.e., C IV lines (312.4 Å, 419.7 Å), W XLVI line (127 Å), Ne VIII lines (88.1 Å, 103 Å), and Ne VII Line (465.2 Å), at the edge region in two dimensions with high spatial and temporal resolutions simultaneously. The MEUVI diagnostics is installed on the EAST horizontal J port to monitor plasma and first imaging data is obtained during the commissioning of the system in the 2024 experiment campaign. It is in good agreement with that measured by the traditional extreme ultraviolet (EUV) spectrometer. In addition, the electron temperature derived from the MEUVI data is higher than that given by the Helium beam emission (He-BES) spectroscopy system since the Ne VIII emission is mainly located inside the last closed surface region. However, the tendency of the evolution of the electron temperature is consistent each other, which are given by these two systems. These results verify that the MEUVI diagnostics can work as a potential tool for the measurement of edge plasma temperature and monitoring of impurities. [ABSTRACT FROM AUTHOR]

The importance of the symmetric as well as non-symmetric ion-atom absorption processes in broad spectral region within a model of solar photosphere and also within the corresponding sunspot models, has been previously emphasized. This motivated us to study the photo-association, charge-exchange and photo-dissociation absorption processes in the cases of non-symmetric and symmetric systems involving hydrogen and potassium atoms, ions, molecules and molecular-ions. We have calculated the data for molecules and molecular state characterizations needed for current computation. We determined the partial and average cross-sections and corresponding spectral absorption rate coefficients, as the functions of wavelengths, and temperatures (100 nm ⩽ λ ⩽ 1000 nm, 400 K ⩽ T ⩽ 10 000 K). Our calculations are performed for conditions that exist in different layers of weakly ionized stellar atmospheres. The obtained data are potentially of high impact and may have broad further applications, e.g., for modelling of laboratory plasmas and various astrophysical objects including geocosmical ones. [ABSTRACT FROM AUTHOR]

We calculate hydrogen line shapes resulting from the simultaneous Stark effect of the plasma microfield and an oscillating electric field. Like laboratory plasmas, many kinds of space plasmas are affected by oscillating electric fields with a magnitude similar to that of the microfield. Here we focus on conditions where we expect that the effect of ion dynamics and oscillating electric are both significant. The combined effect of their dynamics on the quantum emitter is retained by a computer simulation coupled to a numerical integration of the Schrödinger equation. Our calculations are applied for conditions and transitions where significant changes in the line shape allow for a diagnostic of the plasma and oscillating field. [ABSTRACT FROM AUTHOR]

Porous alumina (PA) films have been investigated for selective optical surface application. In this work, we use pulsed plasma electrolytic oxidation (PPEO) to produce porous surfaces in aluminum. During the PPEO processing, image of plasma on the samples and active species present in micro-discharges were documented using CCD camera and standard optical emission spectroscopy (OES) technique. Porosity was controlled by varying the pulsewidth ($T_{\mathrm {on}}$) and treatment time, keeping the pulse repetition time ($T_{\mathrm {off}}$) constant. The optical reflectance and thermal efficiency of the samples were investigated for samples with different microstructure, crystalline phase and chemical composition. It is shown that coatings produced by shorter pulses ($T_{\mathrm {on}}$) with smaller time of treatment resulted in smallest pore size and more uniform distribution. These results positively influenced the reflectance and thermal efficiency of the surfaces. [ABSTRACT FROM AUTHOR]

The construction and operation of the first generation of magnetically controlled nuclear fusion power plants require the development of proper physics and the engineering bases. The analysis of data, recently collected by the actual largest and most important tokamak in the world JET, that has successfully completed his second deuterium and tritium campaign in 2021 (DTE2) with a full ITER like wall main chamber, has provided an important consolidation of the ITER physics basis. Thermonuclear plasmas are highly nonlinear systems characterized by the need of numerous diagnostics to measure physical quantities to guide, through proper control schemes, external actuators. Both modelling and machine learning approaches are required to maximize the physical understanding of plasma dynamics and at the same time, engineering challenges have to be faced. Fusion experiments are indeed extremely hostile environments for plasma facing materials (PFM) and plasma-facing components (PFC), both in terms of neutron, thermal loads and mechanical stresses that the components have to face during either steady operation or off-normal events. Efforts are therefore spent by the community to reach the ultimate goal ahead: turning on the first nuclear fusion power plant, DEMO, by 2050. This editorial is dedicated at reviewing some aspects touched in recent studies developed in this dynamic, challenging project, collected by the special issue titled “New Challenges in Nuclear Fusion Reactors: From Data Analysis to Materials and Manufacturing”.

This research aims to investigate parameters for magnesium (Mg) carbon (C), and carbon/magnesium plasma produced by the exploding electrical wire (EEW) technique. In this work, C and Mg nanoparticles were synthesized. The plasma spectra with three different current values (50, 75 and 100A) were recorded using optical emission spectroscopy (OES). The plasma electron temperature (Te), electron density (ne), plasma frequency (fp), Debye length (ℷD), and Debye number (ND) provided by arc discharge plasma were calculated. Boltzmann plots were used to calculate the electron temperature (Te); electron density (ne) was calculated by Stark broadening . The results showed that the electron temperature and electron density increased with the increase of current. For carbon plasma, Te increased from (1.243 to 1.533) eV, and ne increased from (8.762 to 9.857) cm-3. Te for magnesium plasma increased from (0.508 to 0.724)eV and ne increased from(6.700 to 10.420) cm-3. When the magnesium strip was exploded in carbon suspension, Te increased from (0.744 to 0.851) eV, and electron density was raised from (5.738 to 9.304)cm-3. [ABSTRACT FROM AUTHOR]

Microwave Interferometer in the Limiter Shadow (MILS) is a new diagnostic, installed on ASDEX Upgrade for electron density measurements in the far Scrape‐Off Layer (SOL). At the chosen frequency of 47 GHz, the region of measurements varies within several centimetres before and after the limiter, depending on the density. 200 kHz bandwidth allows resolving transient events such as edge localized modes filaments and turbulence filaments. The measured quantities, phase shift, and power decay of the microwave beam, which crosses the plasma, are directly connected to the density and do not depend on any other plasma quantity. In this work, we analyse the influence of a filamentary perturbation on MILS signals. Simple representation of a filament is adopted, with parameters relevant to experimental filament properties, reported for ASDEX Upgrade. Forward modelling is done in COMSOL software by using RAPLICASOL, to study the response of the MILS synthetic diagnostic to the presence of a filament. Qualitative and quantitative dependencies are obtained and the boundaries of MILS sensitivity to filaments, or to the density perturbation in far SOL in general, are outlined. [ABSTRACT FROM AUTHOR]

The goal of this work is to study plasma parameters for Fe plasma generated by exploding wire (EEW) in carbon nanotubes-water colloid with three current values (50, 100 and 150)A. In this research, the plasma electron temperature (Te), the electron density (ne), electron density (ne), plasma frequency(f p), Debye length (λD) and Debye number (ND) were found for Fe produced by Arc discharge plasma. Boltzmann plot was used to calculate the plasma electron temperature (Te);electron density (ne) was calculated from Stark broadening. It was found that the electron temperature values increased from (0.4134 _ 0.415) eV and the electron density increased from( 0.93 - 1.16)× 1017cm-3 . [ABSTRACT FROM AUTHOR]

During the last decade a new probe design for active plasma resonance spectroscopy, the multipole resonance probe (MRP), was proposed, analyzed, developed, and characterized in two different designs: the spherical MRP (sMRP) and the planar MRP (pMRP). The advantage of the latter is that it can be integrated into the chamber wall and can minimize the perturbation of the plasma. Both designs can be applied for monitoring and control purposes of plasma processes for industrial applications. As usual for this measurement technique, a mathematical model is required to determine plasma parameter (electron density, electron temperature, and collision frequency of electrons with neutral atoms) from the measured resonances. Based on the cold plasma model a simple relationship between the resonance frequency and the electron density can be derived and leads to excellent measurement results. However, a simultaneous measurement of the electron temperature in low-pressure plasmas requires a kinetic model, because the half-width of the resonance peak is broadened by kinetic effects. Such a model has been derived and first results show the broadening of the spectra as expected. Deriving a relation between the half-width and the electron temperature will allow the simultaneous measurement and an improvement of monitoring and control concepts. [ABSTRACT FROM AUTHOR]

Recent advances in acquisition equipment are providing experiments with growing amounts of precise, yet affordable sensors. At the same time, an improved computational power, coming from new hardware resources [GPU, field-programmable gate array (FPGA), adaptive compute acceleration platform (ACAP)] has been made available at relatively low costs. This led us to explore the possibility of completely renewing the chain of acquisition for a fusion experiment, where many high-rate sources of data, coming from different diagnostics, can be combined in a wide framework of algorithms. If, on the one hand, adding new data sources with different diagnostics enriches our knowledge about physical aspects, on the other hand, the dimensions of the overall model grow, making relations among variables more and more opaque. A new approach for integrating such heterogeneous diagnostics, based on the composition of deep variational autoencoders, could ease this problem, acting as a structural sparse regularizer. This has been applied to RFX-mod experimental data, integrating the soft X-ray linear images of plasma temperature with the magnetic state. However, to ensure a real-time signal analysis, these algorithmic techniques must be adapted to run in well-suited hardware. In particular, it is shown that, attempting a quantization of neuron transfer functions, such models can be adapted to run in an embedded programmable logic device. The resulting firmware, approximating the deep inference model to a set of simple operations, fits well with the simple logic units that are largely abundant in FPGAs. This is the key factor that permits the use of affordable hardware with complex deep neural topology and operates them in real-time. [ABSTRACT FROM AUTHOR]

This journal article shows our recent research about the validity of the double-curling method while a film deposition occurs. Curling probe is one of the microwave resonators mainly utilized to measure the electron density in plasma. The double-curling probe method is an application of the probe that allows us to make in-situ measurements of both electron density and deposited film thickness on the probe using the two different-sized curling probes. In this journal article, we firstly researched the validity of the method in a simulated condition where the probes were in argon plasma and where the probe surface is covered with a polyimide film (12.5–50 μ m thickness). This first research showed that the electron density and the film thickness derived with the method were decently close to the values measured with the Langmuir probe and micrometer, respectively. We then researched the validity of the double-curling probe method in the situation where the hydrogenated-amorphous-carbon film deposition occurs on the probe surface. This second measurement demonstrated that the double-curling probe method can derive a constant electron density and a growing film while the film was depositing. These overall results verified the decent validity of the double-curling probe method for making an in-situ measurement of both electron density and depositing film thickness. [ABSTRACT FROM AUTHOR]

The ITER Core Plasma Thomson Scattering (CPTS) diagnostic system is designed to measure the electron temperature and density with an accuracy of 10 % and 5 %, respectively, at the Tokamak plasma core with a spatial resolution of 66 mm. A 1064 nm laser is injected into the vacuum vessel during the plasma pulse, where the laser light is scattered by the plasma electrons due to Thomson Scattering. The scattered light is collected and analysed to determine the electron temperature and density. The CPTS diagnostic PDR design proposes a complete, detailed and robust preliminary design, compliant with the system requirements and nuclear regulations. [ABSTRACT FROM AUTHOR]

The W Environment in Steady-state Tokamak was designed and built to test ITER-like tungsten plasma facing components in a long pulse (∼ 1000 s) scenario. Recently, a multi-energy soft x-ray diagnostic (MESXR) was installed in the WEST (W Environment in Steady-state Tokamak), to understand the sources, transport and confinement of high-Z impurities. The purpose of this work is to describe the engineering challenges posed by the long pulse scenario for the integration of the MESXR diagnostic and how they were addressed and solved. The calculations of vacuum and thermal stress as well as heat transfer are presented and discussed. [ABSTRACT FROM AUTHOR]

The experimental studies of active plasma source are presented. The plasma was formed by an incomplete discharge on the surface of ferroelectric BaTiO 3 samples. The spectrum of the discharge was received using the optical emission spectroscopy method. The spectrum lines corresponded to the atoms and ions of elements related to the ferroelectric (Ba, Ti, O) and residual gas (N). The intensity of the spectrum lines depended on the discharge current and varied slightly depending on the residual gas in the pressure range of 10−5-10−3 Torr. An increase in the gas pressure results in the slight increase in the electron temperature of excited atoms of the discharge plasma. The ion emission in a plasma source at a negative bias voltage has been studied. [ABSTRACT FROM AUTHOR]

• The dispersion interferometer based on CO 2 laser was developed for Globus-M2 tokamak. • Time resolution = 20 μs, spatial resolution = 0.02 m, measurement accuracy ≤ 1017 m −2. • During the year long operation, DI has proven to be reliable diagnostic at Globus-M2. • It is planned to use DI measurements for plasma density stabilizing in Globus-M2. The dispersion interferometry diagnostic (DI) based on the CO 2 -laser was commissioned at the Globus-M2 tokamak for absolute measurements of the line-integrated electron density (IED) along the chord in the equatorial plane. IED measurement error corresponding to the intrinsic noise of the acquisition device was below 1017 m −2 with time and spatial resolution 20µs and 2 cm, respectively. Inference of the IED using the second harmonic interference was done by means of spectral algorithm. Execution of the algorithm is performed at the FPGA in real-time mode. During the year long operation, DI was proven to be reliable and robust IED diagnostic at Globus-M2. [ABSTRACT FROM AUTHOR]

Featured Application: Over the last decade electric propulsion devices have evolved from laboratory units to qualified space hardware. Due to the diversity of concepts numerous electric thruster technologies are available on the new space market. Each technology has a specific working principle which implies a wide variety of plasma discharges and ion beams. Currently, it is still difficult to compare, without bias, these plasmas to each other with standard devices and procedures. This work aims at contributing to the effort towards standardization of a specific type of plasma diagnostic called a Faraday cup. This instrument is of great importance as it measures the ion current density in electric thruster plumes. This physical quantity provides information on key parameter for thruster development and production such as thrust, beam divergence, ionization degree and propellant use. In this contribution we describe and validate the optimization of a Faraday cup collimator in the case of Hall thrusters. A Faraday cup (FC) is an instrument dedicated to current measurement in beams, jets and plasmas. It consists of a set of polarized electrodes mounted in such a way plasma sheath effect can be neglected, yielding accurate and reliable results. A FC is composed of three main parts, namely a collector or cup, which collects the current, a collimator, which defines the collection area and can contribute to limit electrons from entering the cup and a housing which protects the instrument from perturbation caused by the surrounding medium. In this paper, we provide experimental results of the effect of the collimator upon the measured ion current within the beam of a low-power Hall thruster. Different collimator materials, aperture diameters and polarization voltages are studied to determine the optimum design. Minimum dimension as well as appropriate materials are given as a conclusion in the case of low-power Hall thruster beam investigation. [ABSTRACT FROM AUTHOR]

The RFX-mod2 Nuclear Fusion experiment is an upgrade of RFX-mod, which was shutdown in 2016. Among the other improvements in the machine structure and diagnostics, a larger number of electromagnetic probes (EMs) is foreseen to provide more information about plasma instabilities and to allow an improved real-time plasma control. An analog-to-digital converter (ADC) architecture able to provide, at the same time, both transient recording and real-time streaming, as well as field-programmable gate array (FPGA)-based time integration of the inputs, is foreseen in RFX-mod2. Transient recording provides full-speed data acquisition (up to 1 MSample/s) by recording data in local memory and reading memory content after the plasma discharge. Real-time streaming of the subsampled data is required for active control. The chosen technology is based on the XILINX Zynq architecture that provides, in the same chip, a multicore Advanced RISC Machines (ARM) processor tightly coupled to an FPGA. Time-critical functions are carried out by the FPGA, such as the management of the circular data buffer, low-pass filtering for subsampling of the samples to be streamed, and digital integration. Other functions are carried out by the processor, such as the management of the configuration setting, received via Transmission Control Protocol (TCP)/IP or Hypertext Transfer Protocol (HTTP), the data readout of acquired samples in transient recording buffers, and network data streaming of data collected for active real-time plasma control. [ABSTRACT FROM AUTHOR]

Abstract Active Plasma Resonance Spectroscopy (APRS) is a well known diagnostic method, where a radio frequency probe is immersed into a plasma and excites plasma oscillations. The response of the plasma is recorded as frequency dependent spectrum, in which resonance peaks occur. By means of a mathematical model plasma parameters like the electron density or the electron temperature can be determined from the detected resonances. The majority of all APRS probes have in common, that they are immersed into the plasma and perturb the plasma due to the physical presence of the probe. Thus, they are invasive and can at least influence the homogeneity of the plasma. To overcome this problem, the planar Multipole Resonance Probe (pMRP) was invented, which can be integrated into the chamber wall of a plasma reactor. Within this paper, the first analytic model of the pMRP is presented, which is based on a cold plasma description of the electrons. The general admittance of the probe-plasma system is derived by means of functional analytic methods and a complete orthonormal set of basis functions. Explicit spectra for an approximated admittance including a convergence study are shown. The determined resonance frequencies are in good agreement with former simulation results.

Since the 1940s, Microwave Cavity Resonance Spectroscopy (MCRS) has been used to investigate a variety of solids, gases, and low-pressure plasmas. Recently, the working terrain of the diagnostic method has been expanded with atmospheric-pressure plasmas. This review discusses the advancements that were required for this transition and implications of studying highly collisional, with respect to the probing frequencies, plasmas. These developments and implications call for a redefinition of the limitations of MCRS, which also impact studies of low-pressure plasmas using the diagnostic method. Moreover, a large collection of recommendations concerning the approach and its potential for future studies is presented. [ABSTRACT FROM AUTHOR]

Diagnostic pressure gauges (DPGs) shall provide measurements of the neutral gas pressure in various locations of the International Thermonuclear Experimental Reactor (ITER) vacuum vessel. This parameter is essential for the basic control of ITER operation as well as for input to physics models of the plasma boundary. The hot cathode (filament) is the component of the DPG sensor that is exposed to most demanding loads. In order to reach the required electron emission from the filament, it has to be heated to high temperatures by a direct current. As a result, thermal stresses appear, and in the presence of a magnetic field, additional mechanical stresses caused by Lorentz forces arises. On the one hand, due to a large number of pulses foreseen in ITER, this load will be cyclic, which may result in filament failure caused by fatigue. On the other hand, the longest pulses in ITER are expected to be in the order of 30 min, and thus, filaments could fail due to creep. In order to verify that the filament of the DPG sensor can withstand fatigue and creep dedicated experiments have been conducted. Results of these tests are discussed in this article. [ABSTRACT FROM AUTHOR]

A digital holography device is currently undergoing development at the Oak Ridge National Laboratory for the purpose of measuring surface topography, with the goal of deployment as a real-time plasma-facing component diagnostic for the study of materials that could be utilized in a nuclear fusion device. The holography system utilizes one or two lasers depending on the scale of surface features under measurement. Measurements of surface roughness were performed in a single-laser mode and compared with the data from profilometry, with a linear correlation of increased holographic measurement fidelity as surfaces became smoother. Characterization of the dual-laser operating mode has been performed via surface measurement of stainless steel targets with “stair-step” features in various sizes. Results demonstrated that surface features with known sizes as small as $25.4~\mu \text{m}$ could be resolved. Measurements were within $\sim 55~\mu \text{m}$ or less deviation from the actual sizes, and measurement accuracy was improved as feature size was increased, corresponding to the effect of noise becoming less pronounced. A target exposed to plasma generated by an electrothermal (ET) arc source was analyzed with flat-field correction and averaging of sequential image frames to demonstrate the improved measurement quality in preparation for future use of holography on ET arc-exposed targets. [ABSTRACT FROM AUTHOR]

Thin amorphous films of LiPON solid electrolyte were prepared by anodic evaporation of lithium orthophosphate Li3PO4 in an arc discharge with a self-heating hollow cathode at a nitrogen pressure of 1 Pa. Distribution of the arc current between two electrodes having an anode potential provided independent control of the evaporation rate of Li3PO4 and the density of nitrogen plasma. Stabilization of the evaporation rate was achieved using a crucible with multi-aperture cover having floating potential. The existence of a threshold value of discharge current (40 A) has been established, which, upon reaching ionic conductivity over 10−8 S/cm, appears in the films. Probe diagnostics of discharge plasma were carried out. It has been shown that heating the films during deposition by plasma radiation to a temperature of 200 °C is not an impediment to achieving high ionic conductivity of the films. Dense uniform films of LiPON thickness 1 μm with ionic conductivity up to 1 × 10−6 S/cm at a deposition rate of 4 nm/min are obtained.

Lanthanum hexaboride hollow cathodes represent a viable option for high power Hall effect thruster applications, under development for the next generation of manned and robotic interplanetary missions. In this scenario, SITAEL and the University of Pisa are actively developing high current hollow cathodes capable of providing discharge current in the range 10–100 A to be coupled with high power Hall effect thrusters. The cathode design is based on an in-house theoretical model of the internal sections of the cathode, recently integrated with a simplified model of the cathode plume. Despite the application of hollow cathodes on flight and laboratory model Hall effect thrusters, many questions remain unsolved. In particular, issues related to onset of instabilities, due to plume mode or ion acoustic turbulence, are still unclear, while it is known that they can affect the overall performance of the cathode and thruster unit. This paper focuses on the experimental investigation of the cathode plume by means of measurements of the main plasma parameters, at different operating conditions and for different cathode geometry. Two cathodes were investigated, namely HC20 and HC60, designed to be coupled with SITAEL's HT5k and HT20k (5 kW- and 20 kW-class) Hall effect thrusters. The cathodes were mounted in stand-alone configuration with an auxiliary cylindrical anode. The experimental campaign was performed using triple Langmuir probes as plasma diagnostic system. The probes were mounted on scanning mechanisms to measure the plume parameters at various radial and axial distances from the keeper exit. General trends of electron temperature, plasma potential and plasma density are reported in terms of discharge current, mass flow rate and cathode orifice geometry. The results highlight that the cathode plate orifice selection affects the plume mode onset, giving the possibility to extend the stable mode of cathode operation in the current range required by the thruster.

An 85 W class Hall thruster with inner and outer electromagnetic coils was developed, and its thrust performance and plume characteristics were experimentally evaluated. The 85-W Hall thruster required a maximum magnetic flux density along the channel centerline above 24.3 mT to achieve stable and efficient operation above a discharge voltage of 225 V. A specific impulse of 1050 s, thrust-to-power ratio of 59.5 mN/kW, and anode efficiency of 0.306 were achieved at a discharge voltage of 225 V and a discharge power of 88.9 W under a background pressure of 7.9 × 10−4 Pa. Moreover, the thruster achieved throttling at a discharge power of 47.6–118.5 W with stable operation. The low anode efficiency of the 85-W Hall thruster was due to low propellant utilization and a large beam divergence. The short effective length for the propellant ionization owing to the narrow channel is deduced to be the cause for the low anode efficiency in low-power Hall thrusters. The mass utilization efficiency of the 85-W Hall thruster improved as the anode mass flow density increased. Therefore, an increase in the anode mass flow density is required to improve the performance of the 85-W Hall thruster. • An 85-W Hall thruster with inner and outer coils was developed and evaluated. • The thruster required >24.3 mT to achieve efficient operation above 225 V. • Anode efficiency was low because of low mass utilization and beam efficiencies. [ABSTRACT FROM AUTHOR]

Featured Application: Plasma-aerosol systems open new potential opportunities in a wide range of applications including agriculture, combustion control, nanotechnology, medicine and cosmetics. The interaction of plasmas and liquid aerosols offers special advantages and opens new perspectives for plasma–liquid applications. The paper focuses on the key research challenges and potential of plasma-aerosol interaction at atmospheric pressure in several fields, outlining opportunities and benefits in terms of process tuning and throughputs. After a short overview of the recent achievements in plasma–liquid field, the possible application benefits from aerosol injection in combination with plasma discharge are listed and discussed. Since the nature of the chemicophysical plasma-droplet interactions is still unclear, a multidisciplinary approach is recommended to overcome the current lack of knowledge and to open the plasma communities to scientists from other fields, already active in biphasic systems diagnostic. In this perspective, a better understanding of the high chemical reactivity of gas–liquid reactions will bring new opportunities for plasma assisted in-situ and on-demand reactive species production and material processing. [ABSTRACT FROM AUTHOR]

The roadmap to the realization of fusion energy describes a path towards the development of a DEMO tokamak reactor, which is expected to provide electricity into the grid by the mid of the century (Romanelli, 2013). The DEMO diagnostic and control (D&C) system must provide measurements with high reliability and accuracy, not only constrained by space restrictions in the blanket, but also by adverse effects induced by neutron, gamma radiation and particle fluxes. In view of the concept development for DEMO control, an initial selection of suitable diagnostics has been obtained (Biel et al., 2019). This initial group of diagnostic consists of 6 methods: Microwave diagnostics, thermo-current measurements, magnetic diagnostics, neutron/gamma diagnostics, IR interferometry/polarimetry, and a variety of spectroscopic and radiation measurement systems. A key aspect for the implementation, performance and lifetime assessment of these systems on DEMO, is mainly attributable to their location, that must be well protected, and meet their own set of specific requirements. With this in mind, sightline analysis, space consumption and the evaluation of optical systems are the main assessment tools to obtain a high level of integration, reliability and robustness of all this instrumentation; essential features in future commercial fusion power nuclear plants. In this paper we concentrate on spectroscopic and radiation measurement systems that require sightlines over a large range of plasma regions and inner reactor surfaces. Moreover, this paper outlines the main results and strategies adopted in this early stage of DEMO conceptual design to assess the feasibility of this initial set of diagnostic methods based on sightlines and the integration of these needed for DEMO D&C. [ABSTRACT FROM AUTHOR]

The present paper deals with the surface heat flux estimation with thermocouples (TC) and fiber Bragg grating (FBG) embedded in the plasma facing components (PFC) of the WEST tokamak. A 2D heat transfer model combined with the conjugate gradient method and the adjoint state is used to estimate the plasma heat flux deposited on the PFC. The plasma heat flux is characterized by the time evolution of its amplitude and spatial shape on the target (heat flux decay length λ q t , power spreading in the private flux region S t and the strike point location x 0). As a first step, five ohmic pulses have been investigated with different magnetic configuration and divertor X-point height varying from 44 to 68 mm from the surface. Despite an outboard shift, the relative displacements of the outer strike point as well as the heat flux decay length derived from the TC/FBG systems are consistent with the magnetic equilibrium reconstruction. [ABSTRACT FROM AUTHOR]

• Electron density profile is measured with Li-BES diagnostic on EAST. • The whole optical system of Li-BES diagnostic has been shifted outwards. • It's confirmed that transmissivities of APD channels in the edge region are improved. • Electron density profile behaviors during fast transient events on EAST are observed. Lithium Beam Emission Spectroscopy (Li-BES) diagnostic has been developed on the Experimental Advanced Superconducting Tokamak (EAST), aiming at providing the edge electron density profile and density fluctuation. This system has been upgraded to 32 × 4 (radial × poloidal) channels since the 2016 campaign with a radial observation range of about 30 cm at the midplane on the low field side. The spatial resolution of Li-BES diagnostic is about 1 cm. The whole optical system of Li-BES diagnostic has been shifted 9 cm away from the tokamak axis perpendicular to the flange at horizontal D-port on EAST since the 2017 campaign. It's confirmed that transmissivities of Avalanche PhotoDiode (APD) channels in the edge region are improved by comparing the relative light intensity calibration factors of the same row of APD channels before and after the shift. Spatial calibration and relative light intensity calibration of this system have been performed. Based on Schweinzer's algorithm [J. Schweinzer et al., Plasma Phys. Control. Fusion 34, 1173 (1992)], the edge electron density profile is reconstructed and shown to be consistent with those provided by other diagnostics on EAST. The electron density profile evolution during the plasma current ramp-down process is observed with Li-BES diagnostic in both SOL region and pedestal region. With an injected Li-beam under the high frequency chopping control, the temporal resolution of the reconstructed electron density profile can be up to 10 μ s , which reveals temporal behaviors of fast transient events on EAST, such as the L-H transition and ELM crashes. [ABSTRACT FROM AUTHOR]

A Faraday cup (FC) is an instrument dedicated to current measurement in beams, jets and plasmas. It consists of a set of polarized electrodes mounted in such a way plasma sheath effect can be neglected, yielding accurate and reliable results. A FC is composed of three main parts, namely a collector or cup, which collects the current, a collimator, which defines the collection area and can contribute to limit electrons from entering the cup and a housing which protects the instrument from perturbation caused by the surrounding medium. In this paper, we provide experimental results of the effect of the collimator upon the measured ion current within the beam of a low-power Hall thruster. Different collimator materials, aperture diameters and polarization voltages are studied to determine the optimum design. Minimum dimension as well as appropriate materials are given as a conclusion in the case of low-power Hall thruster beam investigation.

The paper presents comparison of two silicon drift detectors (SDD), one made by Amptek, USA, and the second one by PNDetector, Germany, which are considered for a soft X-ray diagnostic system for W7-X. The sensitive area of the first one is 7 mm2 × 450 μm and the second one is 10 mm2 × 450 μm. The first detector is cooled by a double-stage Peltier element, while the second detector is cooled by single-stage Peltier element. Each one is equipped with a field-effect transistor (FET). In the detector from Amptek, the FET is mounted separately, while in the detector from PNDetector, the FET is integrated on the chip. The nominal energy resolution given by the producers of the first and the second one is 136 eV@5.9 keV (at -50°C) and 132 eV@5.9 keV (at -20°C), respectively. Owing to many advantages, the investigated detectors are good candidates for soft X-ray measurements in magnetic confinement devices. They are suitable for soft X-ray diagnostics, like the pulse height analysis (PHA) system for the stellarator Wendelstein 7-X, which has been developed and manufactured at the Institute of Plasma Physics and Laser Microfusion (IPPLM), Warsaw, in collaboration with the Max Planck Institute for Plasma Physics (IPP), Greifswald. The diagnostic is important for the measurements of plasma electron temperature, impurities content, and possible suprathermal tails in the spectra. In order to choose the best type of detector, analysis of technical parameters and laboratory tests were done. Detailed studies show that the most suitable detector for the PHA diagnostics is the PNDetector.

This paper shows the theoretical predictions of the outer-shell ionization effect on the positions of Kα1,2, Kβ1,3, and K β2 X-ray lines for some 4d-transition metals (molybdenum and palladium) and 4f rare-earth elements (dysprosium and ytterbium). The ionization energy shifts have been evaluated using the multiconfiguration Dirac-Fock method, containing Breit interaction and quantum electrodynamic (QED) corrections. The presented results are important for obtaining the information about some parameters of plasma generated by different sources, especially by pulsed power machine and short-pulse lasers.