Plasma Radiation Research Articles

Stabilization of liquid tin surfaces under D plasma irradiation by a capillary porous system

Liquid metal divertors are discussed as a potential alternative to divertor components made entirely of solid materials such as tungsten. However, liquid metal interaction with H isotope plasmas poses entirely new challenges, including the stability of the liquid surface. In this article, the interaction of low-temperature D plasmas with both free liquid tin surfaces, and the liquid metal confined in a capillary porous system (CPS) is presented. Free surfaces showed intolerable instabilities due to formation of gas bubbles in the melt, as opposed to a strong stabilizing effect of the CPS. A tendency of liquid tin to well up and entirely cover the surface of the CPS may be beneficial in terms of quickly re-establishing a tin surface after depletion by transient overloading. On the other hand, this appears to counteract efforts to fully suppress superficial bubble formation and bursting, and the resulting ejection of tin droplets by designing a CPS with very small pores.

ICRH-related impurity source and control across experiments in H, D, T plasmas at JET-ILW

The experimental and theoretical analysis were focused on experiments conducted to assess the effect of plasma isotopes, protium (H), deuterium (D), and tritium (T) on ion cyclotron resonance heating (ICRH) related plasma wall interactions. Comparison of L-mode discharges with N = 1 3He and N = 1 H minority ICRH heating scenarios were done for different isotopes. For the selected pulses, the behaviour of high-Z, mid-Z and low-Z intrinsic impurity and radiated power behaviour was investigated based on data from VUV, visible spectroscopy, and bolometry diagnostic at Joint European Torus. It was found that for N = 1 3He scenario during radiofrequency antennas operation, core W, Ni content, Be source and the radiated power are higher for π/2 in comparison to dipole antenna phasing. Lowest core Ni, W content and radiated power is clearly observed for H plasmas in comparison to D and T, where for this ICRH scenario behaviour was similar. However, lower Be photon flux is observed for T in comparison to D plasmas. Be sputtering by He particles is responsible for such an effect. Additionally, several computer simulations were conducted using the COREDIV code. The difference in the electron temperature was due to the difference in the isotope masses. Increased temperature in the central plasma in the case of T plasmas leads to higher radiation in the central plasma in comparison to H plasmas. As a result, the power across separatrix is lower and the temperature on the divertor plate decreases with the increase of the isotope mass. At these temperatures on the divertor plate, W is not sputtered by the main plasma ions H, D and T and by He. For the N = 1 H ICRH scenario clear difference between D and T plasma was observed with higher metallic impurity content for T plasma in comparison to D. Impurity content in the plasmas is found to be sensitive to the power balance between the antenna straps. Its minimum is observed for the maximum of P cen/P tot.

Lithography-Free Nanofabrication on Various Semiconductors by the Codeposition Etching Technique.

Nano-/microstructures can be formed with the aid of small amounts of impurities during deposition with noble gas plasma irradiation, which is referred to as codeposition etching. This can be a new method for lithography-free semiconductor nanofabrication. Here, the codeposition etching method was employed with argon plasma and molybdenum (Mo) impurities on various semiconductors. Structures can be formed only on substrates that have a lower sputtering yield than the seed impurity. The density, area, and height of structures are related to both the impurity deposition rate and the substrate material. Moreover, two mechanisms of impurity nucleation are proposed according to time dependence results for the formation of the structures.

Studies on the motion and radiation of interior plasmas in gas-filled hohlraums with different laser entrance hole sizes

An experiment on 100 kJ laser facility is performed to study the motive features and radiation properties of plasmas from different areas inside gas-filled cylindrical hohlraums. These hohlraums are designed to possess one open end and one laser entrance hole (LEH) with different diameters, which would or not result in the blocking of the LEH. An x-ray streak camera that is set at 16 degrees with respect to the hohlraum axis is applied to acquire the time-resolved x-ray images from the open end. Based on the images, we can study the evolutions of the wall plasma, corona bubble plasma and LEH plasma simultaneously through an equivalent view field of hohlraum interior. Multi-group flat response x-ray detectors are applied to measure the x-ray fluxes. In order to understand these characteristics, our two-dimensional radiation hydrodynamic code is used to simulate the experimental results. For the accuracy of reproduction, dielectronic recombination and two parameter corrections are applied in our code. Based on the comparison between experiments and simulations, we quantitatively understand the blocking process of LEH and the motion effects of other plasmas. The calibrated code is beneficial to design the gas-filled hohlraum in a nearby parameter space, especially the limit size of LEH.

Impact of nuclear heating distribution on the structural behavior of ITER first wall panel 11

The ITER blanket system safeguards the Tokamak's Vacuum Vessel and ex-vessel components from thermal and nuclear loads induced by the plasma. It comprises two parts: the First Wall panel facing the plasma and the Shield Block that provides the bulk of the shielding. The First Wall panels consist of Beryllium tiles on a CuCrZr layer, supported by stainless-steel structures which are cooled using a pressurized water circuit at 40 bar with an inlet temperature of 70 °C.Fusion for Energy has updated the thermal and mechanical analyses of ITER First Wall Panel 11 in preparation for the serial manufacturing. The panel will face heat flux up to 2 MW/m2 from plasma radiation, in addition to the volumetric nuclear heating, and the electromagnetic loads. A model with an enhanced detailed 3D geometry and heterogeneous materials indicates a 25% reduction of the deposited heating compared to the previous 2D model, from 625.4 kW (2D) to 455.4 kW (3D).The study embraces numerous thermal and mechanical analyses using Ansys software v19.2, incorporating 2D and 3D nuclear heating data. Responses are then compared and thus the possible impact of the two distributions on the thermal and mechanical behavior of the Fist Wall Panel 11 is assessed.

Laser-excited Xe plasma as a radiation source for lithography at wavelengths near 11 nm

Subject of study. The study focuses on the plasma excited by a laser on a gas-jet Xe target. Aim of study. The aim was to achieve such a high emissivity of the Xe plasma at a wavelength of 11.2 nm that would meet the requirements of industrial lithography. In addition to the applied aspect, the work also has a diagnostic component, the purpose of which is to study the internal structure of the laser plasma and determine its internal parameters, such as temperature, concentration, and mean ion charge. Method. The paper contains a review of works devoted to the comprehensive investigation of the laser-produced plasma with a Xe gas-jet target. In the course of this research, several methods of measurements and plasma diagnostics were developed and tested, including multimirror Bragg spectrometry, probing the plasma with the same infrared laser radiation that creates it, and determination of mean ion charge of this nonequilibrium and short-lived laser-produced plasma using the measured absorption of the laser energy in the plasma and a database on cross-sections of ionization by electron impact. Main results. A multimirror Bragg spectrometry technique was developed and tested. This technique was then used to obtain quantitatively calibrated spectra of the laser-produced Xe plasma. An effective mode of irradiating the target with a wide, defocused laser beam has been found, which made it possible to achieve the coefficient of conversion of laser pulse energy into the energy of the narrow-band plasma radiation around λ=11.2nm, approximately equal to 4%. This value is currently a world record for plasmas of such a type. Additionally, an analytical method for determining the temperature and ion charge of the plasma based on experimental measurements was developed. Practical significance. The achieved conversion efficiency of the radiation source under consideration is sufficient for its application in high production industrial lithography. The use of the simple and “clean” radiation source with Xe plasma could eliminate a number of problems encountered in contemporary lithography with a wavelength of 13.5 nm and a source with targets of metallic tin.

Characterization of InN Grown Directly on Sapphire Substrate Using Plasma‐Enhanced Metal Organic Chemical Vapor Deposition

AbstractDirect InN growth is demonstrated and characterized on a sapphire (Al2O3) substrate by plasma‐enhanced metal–organic chemical vapor deposition using high‐density nitrogen (N2) microstrip‐line microwave plasma. N2 plasma irradiation at 650 °C for 20 min forms AlN on Al2O3 substrate. No peak regarding metallic In droplets is detected from InN/Al2O3 regardless of N2 plasma irradiation. InN is found to be rotated 30° with their a‐axis oriented to become InN // Al2O3. The transition layers are confirmed at the InN/Al2O3 interface regardless of N2 plasma irradiation. The surface of InN consisted of large undulations with root mean square values >30 nm, suggesting that strain relaxation introduces misfit dislocations.

Magnetohydrodynamics simulation of magnetic reconnection process based on the laser-driven Helmholtz capacitor-coil targets

Magnetic reconnection is an important rapid energy release mechanism in astrophysics. Magnetic energy can be effectively converted into plasma kinetic energy, thermal energy, and radiation energy. This study is based on the magnetohydrodynamics simulation method and utilizes the FLASH code to investigate the laser-driven magnetic reconnection physical process of the Helmholtz capacitor-coil target. The simulation model incorporates the laser driving effect, and the external magnetic field consistent with the Helmholtz capacitor-coil target is written in. This approach achieves a magnetic reconnection process that is more consistent with the experiment. By changing the resistivity, subtle differences in energy conversion during the evolution of magnetic reconnection are observed. Under conditions of low resistivity, there is a more pronounced increase in the thermal energy of ions compared to other energy components. In simulations with high resistivity, the increase in electrons thermal energy is more prominent. The simulation gives the evolution trajectory of magnetic reconnection, which is in good agreement with the experimental results. This has important reference value for experimental research on the low-β magnetic reconnection.

Helium plasma irradiation on Nickel: Nanostructure formation and electrochemical characteristics

Nanotechnology offers new avenues for the design, fabrication, and application of novel materials. Helium plasma exposure is a technique that can be used to fabricate self-supported metallic nanostructures. In this work, we explore the plasma irradiation conditions for fabricating various morphologies on planar nickel surfaces, and evaluate the electrochemical performance of these surfaces for oxygen evolution reaction (OER) in alkaline media. The preferential growth towards certain morphologies such as nano-pillars, nano-blocks, and micro-structures, is found to be primarily influenced by the applied plasma conditions and two counteracting processes of sputtering and annealing. The plasma treatment increased the electrochemical surface area of the modified samples by approximately 3 to 4 times as compared to the planar/unmodified surfaces, along with an increase in the OER performance for all morphologies. However, in addition to the increased surface area, the electrochemical performance was found to be dependent on the shape, size and thickness of the nano/micro-features. Moving ahead, the ability of this technique to achieve control over the feature size along with its effectiveness for a broad range of metals offers new routes for nanostructuring and functionalization of emerging materials.

Controllable defects in monolayer graphene induced by hydrogen and argon plasma

Graphene has attracted wide attentions since its successfully exfoliation. Honeycomb sp 2 carbon lattice and Dirac semi-metal band structure make graphene a promising material with excellent mechanical strength, thermal conductivity, and carrier mobility. However, the absence of intrinsic bandgap limits its application in semiconductor. Defects in graphene is supposed to modify its band structure and lead to an opened bandgap. Many methods have been demonstrated to introduce defects into graphene, such as chemical reaction, plasma, electron beam, and laser. However, the species of defects are mostly uncontrollable in most treatment processes. In this study, we report three kinds of defects can be controllably induced in graphene via hydrogen (H2) and argon (Ar) plasma. With different parameter and feeding gas, hydrogenated graphene, graphene nanomesh and graphene with vacancies can be well obtained. The defect density can be precisely controlled by tuning plasma power and irradiation time. Morphological, spectroscopic, and electrical characterizations are performed to systematically investigate the defect evolution. Graphene nanomesh and graphene with vacancies show obvious difference for roughness and coverage, whereas the morphology of hydrogenated graphene remains similar with that of as-prepared graphene. For hydrogenated graphene, an opened bandgap of ∼20 meV is detected. For graphene nanomesh and graphene with vacancies, the semiconductive on/off behaviors are observed. We believe this work can provide more details of plasma-induced defects and assist the application of graphene in semiconductor industry.

Symmetrized Dot Pattern as an Alternative Method to Visualize the Dynamics of Tokamak Plasma Radiation

The unusual graphic representation of time series based on Symmetrized Dot Pattern (SDP) helps capturing subtle dynamics in the analyzed signals, otherwise difficult to identify when applying traditional techniques. SDP is creating features and forming a global percept easily readable and recognizable for a human observer. Thanks to this method, local correlations of the signals of any sampled data series can be visualized. This work describes the application of SDP to measurements of tokamak plasma radiation, namely the soft X-ray line-integrated brightness on WEST, where it was thus possible to analyze different phases of the discharge and in particular to identify sawtooth oscillations. In the future, the SDP method could be used to monitor the plasma state and to warn against the appearance of undesirable plasma behavior.

Effect of Corona Discharge Plasma Radiation on the Viability of True Shallot Seeds (Allium cepa L. var. aggregatum)

TSS (True Shallot Seed) need to be developed to address the quality and quality of shallot seeds. The seeds, however, still has constraints on its viability and germination. The objective of this study was to investigate the effect of corona discharge plasma radiation on the viability of true shallot seeds. The research was conducted in March - April 2023 at the Plasma Laboratory, Faculty of Science and Mathematics, Diponegoro University, and the germination test experiments at the the Agricultural Technology Research and Assessment Installation (IP2TP Ungaran). The experiment was designed completely randomized with 6 treatments of radiation time consisting of P0 (without radiation), P1 (5 min), P2 (10 min), P3 (15 min), P4 (20 min), and P5 (25 min). All treatments were carried out with 5 replications. The collected data were processed using ANOVA and then continued with the DMRT test. The results showed that the corona plasma radiation treatment for 15-25 min affected the parameters of germination, germination rate, seed growth rate, vigor index, seed uniformity, and sprout length. Keywords: Plasm, Radiation, Shallots, TSS.

Enhancing starch functionality through synergistic modification via sequential treatments with cold plasma and electron beam irradiation

The impact of dual sequential modifications using radio-frequency (RF) plasma and electron beam irradiation (EBI) on starch properties was investigated and compared with single treatments within an irradiation dose range of 5–20 kGy. Regardless of sequence, dual treatments synergistically affected starch properties, increasing acidity, solubility, and paste clarity, while decreasing rheological features with increasing irradiation dose. The molecular weight distribution was also synergistically influenced. Amylopectin distribution broadened particularly below 10 kGy. Amylose narrowed its distribution across all irradiation doses. This was due to dominating EBI-induced degradation and molecular rearrangements from RF plasma. With the highest average radiation-chemical yield (G) and degradation rate constant (k) of (2.12 ± 0.14) × 10−6 mol·J−1 and (3.43 ± 0.23) × 10−4 kGy−1, respectively, upon RF plasma pre-treatment, amylose underwent random chain scission. In comparison to single treatments, dual modification caused minor alterations in spectral characteristics and crystal short-range order structure, along with increased granule aggregation and surface irregularities. The synergistic effect was dose-dependent, significant up to 10 kGy, irrespective of treatment sequence. The highest synergistic ratio was observed when RF plasma preceded irradiation, demonstrating the superior efficiency of plasma pre-treatment in combination with EBI. This synergy has the potential to lower costs and extend starch's technological uses by enhancing radiation sensitivity and reducing the irradiation dose.

Enhancement of spectral model transferability in LIBS systems through LIBS-LIPAS fusion technique

BackgroundLaser-induced breakdown spectroscopy (LIBS) is extensively utilized a range of scientific and industrial detection applications owing to its capability for rapid, in-situ detection. However, conventional LIBS models are often tailored to specific LIBS systems, hindering their transferability between LIBS subsystems. Transfer algorithms can adapt spectral models to subsystems, but require access to the datasets of each subsystem beforehand, followed by making individual adjustments for the dataset of each subsystem. It is clear that a method to enhance the inherent transferability of spectral original models is urgently needed. ResultsWe proposed an innovative fusion methodology, named laser-induced breakdown spectroscopy fusion laser-induced plasma acoustic spectroscopy (LIBS-LIPAS), to enhance the transferability of support vector machine (SVM) original models across LIBS systems with varying laser beams. The methodology was demonstrated using nickel-based high-temperature alloy samples. Here, the area-full width at half maximum (AFCEI) Composite Evaluation Index was proposed for extracting critical features from LIBS. Further enhancing the transferability of the model, the laser-induced plasma acoustic signal was transformed from the time domain to the frequency domain. Subsequently, the feature-level fusion method was employed to improve the classification accuracy of the transferred LIBS system to 97.8 %. A decision-level fusion approach (amalgamating LIBS, LIPAS, and feature-level fusion models) achieved an exemplary accuracy of 99 %. Finally, the adaptability of the method was demonstrated using titanium alloy samples. Significance and noveltyIn this work, based on plasma radiation models, we simultaneously captured LIBS and LIPAS, and proposed the fusion of these two distinct yet origin-consistent signals, significantly enhancing the transferability of the LIBS original model. The methodology proposed holds significant potential to advance LIBS technology and broaden its applicability in analytical chemistry research and industrial applications.

Study of Nanostructured Layer Growth on Plasma-Facing Materials Irradiated with Helium Plasma

Tungsten and stainless steel samples were irradiated with stationary helium plasma in the plasma linear multicusp plasma device. The surface of the material is modified under the influence of helium plasma with the formation of nanostructures and microstructures on the surface. The fluence of helium ions equal to 8 × 1027 ions/m2 was achieved on the tungsten sample. Depending on the helium ion fluence, fuzzlike layers, loops, and bubbles of 20- to 500-nm scale were formed on the tungsten surface. The fuzz layer thickness depends on the duration of plasma irradiation in a wide range of fluence. Saturation of the growth of the thickness of the tungsten fuzz layer was observed at a fluence of more than 8 × 1026 ions/m2. The growth of microstructures and nanostructures on the surface of stainless steel irradiated with helium plasma was observed. The growth of nanostructured layers is explained by a theoretical model considering the dynamics of adatoms under the influence of plasma.

Response of lettuce seeds undergoing dormancy break and early senescence to plasma irradiation

This study reports the response of lettuce seeds undergoing dormancy breaking and early senescence to DBD plasma irradiation. A heat map of germination percentages at 12 h reveals that dormancy has broken at 39 days' storage, and that one minute of plasma irradiation enhances germination in dormant seeds. Plasma irradiation does not affect those seeds where dormancy has already broken. Early senescence via storage was estimated using ESR measurements and the molecular modification of quercetin. This study reveals that lettuce seed susceptibility to plasma irradiation depends on storage duration and conditions, with dormancy state as a critical variable modulating the impact of plasma irradiation.

Electric steelmaking process monitoring with optical emission spectroscopy – An in-depth review

Electric steelmaking plays an important role in various scenarios for environmentally friendly steelmaking where the processes must be energetically and economically feasible. As electric furnaces’ capacities and low-grade recycled material usage can be expected to increase, optimizing the process practices and flexibility becomes paramount. The high-temperature environment of electric steelmaking sets several criteria for the implemented tools, where the equipment must withstand extreme conditions, have a low maintenance need and cost, and have the capability of real-time data acquisition and analysis. Optical emission spectroscopy (OES) has been studied in laboratory furnaces and on pilot and industrial scales to provide an in situ method for electric arc furnace and ladle furnace process control. Since OES is a method that measures the properties of emitted light, the applications focus on the electric arc plasma, burners’ flames, and heat radiation from the molten bath. The optical spectra carry information on the composition, temperature, and status of the process. This in-depth review compiles the research and usage of OES as a process monitoring tool by focusing on electric arc plasma, burner flames, and molten bath radiation. Suggestions for further development of existing applications and potential new applications are discussed.

Optimization of conditions for excitation of Xe laser plasma in an extreme ultraviolet radiation source for nanolithography in order to increase its efficiency

Subject of study. The study focuses on laser plasma excited by a Xe gas-jet target. Aim of study. The aim of this study is to increase the output of extreme ultraviolet radiation from such a plasma to a level that meets the requirements of industrial production, specifically for use as a radiation source in a new branch of lithography with a wavelength near 11.2 nm. Method. The primary method used involves changing the diameter of the laser beam by moving a Xe gas-jet target along its axis. This adjustment leads to a change in the interaction area between the beam and the target, which in turn alters the size of the laser spark. The intensity of plasma radiation at wavelengths of 11.2 nm and 13.5 nm was measured using a surface-barrier Si photosensor and a Bragg mirror. Additionally, the energy of the laser radiation absorbed by the plasma was measured. Main results. The results show that, when the diameter of the laser beam illuminating the target increases from 46 µm to 344 µm, the energy emitted in the extreme ultraviolet range increases by approximately 5 times. In the identified irradiation mode, the efficiency of converting laser radiation into radiation with a wavelength of 11.2 nm was 3.9%. Recent measurements of the plasma lifetime have shown that it depends on the size of the plasma and, in several experiments, is significantly shorter than the laser pulse duration. This finding suggests that the plasma lifetime can be used as an optimization parameter when selecting the laser pulse duration. Practical significance. A record-high efficiency is obtained for the conversion of laser pulse energy into extreme ultraviolet radiation by a laser-plasma radiation source with a gas target. This achievement opens up the prospect of using such sources in the industrial production of microcircuits.

Design and Test of a Klystron Intra-Pulse Phase Feedback System for Electron Linear Accelerators

Beam stability and timing jitter in modern linear accelerators are becoming increasingly important. In particular, if a magnetic or radio-frequency (RF) compression regime is employed, the beam time of arrival jitter at the end of the linac can be strictly correlated with the phase noise of the accelerating fields of the RF structure working off-crest. For this reason, since 2008, an RF fast-feedback technique, which acts within each RF pulse, has been successfully employed at LNF-INFN (Laboratori Nazionali di Frascati dell’Istituto Nazionale di Fisica Nucleare) in the SPARC_LAB (Sources for Plasma Accelerators and Radiation Compton with Laser And Beam) facility on S-band (2856 MHz) klystrons powered by pulse-forming network (PFN) modulators, as reported in this paper. However, in order to meet the more stringent requirements of plasma wakefield acceleration schemes, some upgrades to this feedback system have been recently carried out. The first prototype has been experimentally tested on a C-band (5712 MHz) klystron, driven by a solid-state modulator, in order to investigate the possibility for additional improvement resulting from the inherently more stable power source. In this paper, the design, realization and the preliminary measurement results obtained at SPARC_LAB after such upgrades will be reviewed.

Evolution of the Electronic Properties of Tellurium Crystals with Plasma Irradiation Treatment.

Tellurium exhibits exceptional intrinsic electronic properties. However, investigations into the modulation of tellurium's electronic properties through physical modification are notably scarce. Here, we present a comprehensive study focused on the evolution of the electronic properties of tellurium crystal flakes under plasma irradiation treatment by employing conductive atomic force microscopy and Raman spectroscopy. The plasma-treated tellurium experienced a process of defect generation through lattice breaking. Prior to the degradation of electronic transport performance due to plasma irradiation treatment, we made a remarkable observation: in the low-energy region of hydrogen plasma-treated tellurium, a notable enhancement in conductivity was unexpectedly detected. The mechanism underlying this enhancement in electronic transport performance was thoroughly elucidated by comparing it with the electronic structure induced by argon plasma irradiation. This study not only fundamentally uncovers the effects of plasma irradiation on tellurium crystal flakes but also unearths an unprecedented trend of enhanced electronic transport performance at low irradiation energies when utilizing hydrogen plasma. This abnormal trend bears significant implications for guiding the prospective application of tellurium-based 2D materials in the realm of electronic devices.