High-temperature Plasma Research Articles

Star formation near the Sun is driven by expansion of the Local Bubble.

For decades we have known that the Sun lies within the Local Bubble, a cavity of low-density, high-temperature plasma surrounded by a shell of cold, neutral gas and dust1-3. However, the precise shape and extent of this shell4,5, the impetus and timescale for its formation6,7, and its relationship to nearby star formation8 have remained uncertain, largely due to low-resolution models of the local interstellar medium. Here we report an analysis of the three-dimensional positions, shapes and motions of dense gas and young stars within 200 pc of the Sun, using new spatial9-11 and dynamical constraints12. We find that nearly all of the star-forming complexes in the solar vicinity lie on the surface of the Local Bubble and that their young stars show outward expansion mainly perpendicular to the bubble's surface. Tracebacks of these young stars' motions support a picture in which the origin of the Local Bubble was a burst of stellar birth and then death (supernovae) taking place near the bubble's centre beginning approximately 14 Myr ago. The expansion of the Local Bubble created by the supernovae swept up the ambient interstellar medium into an extended shell that has now fragmented and collapsed into the most prominent nearby molecular clouds, in turn providing robust observational support for the theory of supernova-driven star formation.

Lifetime measurement of a particular deep crack failure on a flat-type divertor mockup under cyclic high heat flux loading conditions

Plasma facing components are key to enduring high heat flux (HHF) loading from high-temperature plasma in nuclear fusion reactors. Understanding their thermal-mechanical behavior and cracking failure mechanisms related to structural designs and fabrication technologies during HHF loading is of great significance for improving their servicing performance and R&D (research and development) levels. In this study, a particular deep cracking failure process on the tungsten layer of a flat-type divertor mockup during 1800 cycles of 10 MW m−2 HHF loadings is completely monitored and measured with a special improved digital image correlation (DIC) technique. It is found that the DIC measurement under the HHF loading environment is improved successfully to capture fine deformation and strain fields with a spatial resolution less than 0.35 mm so that field strain on a 1 mm thick copper interlayer and deep crack initiation at several microns scale on the tungsten layer are measured out. Based on both full field and local strain and displacement measurements of the target divertor mockup, the thermal mechanical behaviors from deformation to crack initiation and propagation are successfully measured and traced. It is revealed that for the baseline copper interlayer design of a flat-type divertor mockup, the accumulation of plastic strain in the copper interlayer during ratcheting damage induces enough tensile stress on the tungsten layer during HHF cycles, leading to cracking and fracture failures even in its elastic state earlier than the copper LCF lifetime. Current Structural Design Criteria for ITER In-Vessel Components rules fail to cover this kind of ratcheting cracking failure mode in the design stage. New design models or mechanical validation rules to resolve this design blind spot should be established in the future.

Full-wave 2D modeling of helicons propagation and absorption in thespherical tokamak Globus-M2

Numerical modeling of propagation and absorption of fast waves(helicons) with frequency 200 MHz in 2D inhomogeneous plasma of thespherical tokamak Globus-M2 was carried out with 2D full-wave code. Toroidal effects, poloidal magnetic field and the actual shape of the fluxsurfaces were taken into account. The full wave electric field and RF powerabsorption profiles were computed by solving plasma wave equation withelectron Landau damping term. The modeling demonstrated a fairly highefficiency of helicons absorption in the bulk plasma within a wide range ofexperimental parameters. The waves propagate to the inner regions of theplasma column and are mainly absorbed there; less than 20% of RF energyreturns back to the plasma periphery. Keywords: high temperature plasma, nuclear fusion, tokamak, high frequency plasma waves, helicons, plasma wave equation, full-wave code.\

Full-wave 2D modeling of helicons propagation and absorption in the spherical tokamak Globus-M2

Numerical modeling of propagation and absorption of fast waves (helicons) with frequency 200MHz in 2D inhomogeneous plasma of the spherical tokamak Globus-M2 was carried out with 2D full-wave code. Toroidal effects, poloidal magnetic field and the actual shape of the flux surfaces were taken into account. The full wave electric field and RF power absorption profiles were computed by solving plasma wave equation with electron Landau damping term. The modeling demonstrated a fairly high efficiency of helicons absorption in the bulk plasma within a wide range of experimental parameters. The waves propagate to the inner regions of the plasma column and are mainly absorbed there; less than 20% of RF energy returns back to the plasma periphery. Keywords: high temperature plasma, nuclear fusion, tokamak, high frequency plasma waves, helicons, plasma wave equation, full-wave code.

Modelling of three-ion ICRF heating scenario for tokamak Globus-M2

The goal of this paper is to assess the possibility of using a new three-ion ICRF heating scheme on the spherical tokamak Globus-M2. In the first place, the operating frequencies and positions of cyclotron harmonics were found. Matching with frequency band of RF system of Globus-M2 was made. The absorption of electromagnetic waves was modeled using a one-dimensional full-wave code. Since the appearance of high-energy particles is expected in the three-ion ICRF scheme of heating special attention is paid to a comparing the estimates for generated particles energies with their confinement in tokamak Globus-M2. Keywords: nuclear fusion, tokamak, high temperature plasma, Globus-M, ICRF heating, three-ion ICRF, H-D-3He plasma.

Effect of High-Temperature Pulsed Deuterium Plasma on the Structure and Mechanical Properties of the Surface of Cu–Ga and Cu–Ga–Ni Alloys

Effect of High-Temperature Pulsed Deuterium Plasma on the Structure and Mechanical Properties of the Surface of Cu–Ga and Cu–Ga–Ni Alloys

Имитационное облучение ДУО стали 16Cr – 4Al – 2W – 0,3Ti – 0,3Y2O3, перспективной для термоядерных реакторов, в установке Плазменный фокус “Вихрь”

A study of the radiation-thermal resistance of ferritic steel 16Cr – 4Al – 2W – 0.3Ti – 0.3Y2O3 was made. This ODS (oxide dispersion strengthened) steel is perspective for fusion applications. The “Vikhr” Plasma Focus installation was used to introduse of powerful pulsed flows of helium ions and helium plasma. The power density of a beam of fast helium ions and high-temperature helium plasma flows was ~ 108 and 107 W/cm2 at exposure times of ~ 50 and 100 ns, respectively. The number of pulses N varied in the range from 10 to 30. The rate of evaporation and radiaсtive sputtering changed slightly with an increase in the number of pulses of energy flows acting on the material and amounted to h ≈ 0.01 – 0.02 μm/puls. The irradiated surface after repeated melting under the action of a pulsed radiation-thermal load with powerful energy flows acquired a wave-like character with inclusions of dispersed micro particles of the second phase, containing mainly yttrium, oxygen, aluminum, iron, and titanium. At the same time, in contrast to the refractory metals (W, Mo, Ti) earlier under similar radiation conditions studied, no micro- and macro cracks were formed on the surface of the material facing the plasma. “Vikhr” Plasma Focus setup proved to be an effective tool for simulation testing of candidate materials with magnetic and inertial plasma confinement.

ПЛАЗМЕННАЯ ТЕХНОЛОГИЯ ПОЛУЧЕНИЯ СТЕКЛОМИКРОШАРИКОВ НА ОСНОВЕ БОЯ ТАРНЫХ И СОРТОВЫХ СТЕКОЛ

A technology – based on the breakage of graded and container glasses – was developed for the production of glass microbeads in a plasma reactor. The regularities of the influence of the flow rate of plasma-forming gas argon and the power of the plasma reactor on the fractional composition of glass microbeads were established. It was shown that with an increase in the flow rate of plasma-forming gas from 1.0 m3/hour to 2,0 m3/hour and the current strength from 300 A to 400 A, the amount of fraction over 630 microns increases due to coagulation processes. It was established that under the influence of high plasma temperatures, about 6000-8000 K, complete melting and sphering of particles occur with the formation of glass microbeads ranging in size from 80 microns to 1250 microns. The microhardness, acid resistance and alkali resistance of glass microbeads were investigated.

Thermodynamic equilibrium investigation to operational capabilities and process tolerance of plasma gasification for various feedstock

A thermodynamic equilibrium model is employed to study the capability of plasma gasification in waste-to-value concepts. In difference to waste-to-energy concepts, not the caloric value of the product stream, but the achievable total amount of syngas as also the H2 to CO ratio is focused on. Within the study the impact of the feedstock composition, use of gasification agent as also process temperature up to 1800 K is quantified. In the comparison of equilibrium modelled compositions with experimental compositions, it is exposed that compositions obtained by plasma gasification are in high agreement with the ideal equilibrium composition, unlike conventional gasification. It is shown, that above 1400 K a temperature invariant product composition can be achieved for a given feedstock, giving rise to high process tolerance for the high temperature plasma process. Additionally, the possibility to react on changes in feedstock composition and to tune the product gas composition through the flexible use of gasification agent is shown. Furthermore, a way to visualize an operational window of the gasification process is presented. Therefore, constraints set for the syngas ratio and amount as well as the solid carbon content are added based on the equilibrium calculation as borderlines to the van Krevelen plot.

Analysis of investment incentives for power generation based on an integrated plasma gasification combined cycle power plant using municipal solid waste

Municipal solid waste (MSW) high generation rate and final disposal are major issues for societies worldwide. In Colombia, projections warn about potential sanitary emergencies by 2030 due to ∼30% of current landfill short life span (0–3 years). Thus, this work aimed to assess the techno-economic performance of an Integrated Plasma Gasification Combined Cycle power plant (IPGCC) fueled with MSW. The effects of the plasma and reactor temperatures on the IPGCC efficiency were studied. The plant reached the best thermodynamic performance (32.49% efficiency) at a low reactor temperature (2000 °C) and at high plasma temperature (5000 °C) since torch power consumption decreased. At these conditions, the IPGCC power plant, processing 900 t/day, was able to generate ∼56 MWe. In the economic assessment, several financing scenarios were considered for the calculations of the levelized cost of energy (LCOE), which is used as an economic indicator. When the investment structure included 30% green bonds and 70% bank loans, the best LCOE (9.13 ¢US$/kWh) was obtained. Furthermore, if the generation project received a reliability charge of 1.70 ¢US$/kWh, the LCOE would decrease to 7.56 ¢US$/kWh, which could be competitive in the Colombian electricity market, whose 2020 average electricity price was 7.11 ¢US$/kWh.

Organic Waste Gasification: A Selective Review

This review considers the selective studies on environmentally friendly, combustion-free, allothermal, atmospheric-pressure, noncatalytic, direct H2O/CO2 gasification of organic feedstocks like biomass, sewage sludge wastes (SSW) and municipal solid wastes (MSW) to demonstrate the pros and cons of the approaches and provide future perspectives. The environmental friendliness of H2O/CO2 gasification is well known as it is accompanied by considerably less harmful emissions into the environment as compared to O2/air gasification. Comparative analysis of the various gasification technologies includes low-temperature H2O/CO2 gasification at temperatures up to 1000 °C, high-temperature plasma- and solar-assisted H2O/CO2 gasification at temperatures above 1200 °C, and an innovative gasification technology applying ultra-superheated steam (USS) with temperatures above 2000 °C obtained by pulsed or continuous gaseous detonations. Analysis shows that in terms of such characteristics as the carbon conversion efficiency (CCE), tar and char content, and the content of harmful by-products the plasma and detonation USS gasification technologies are most promising. However, as compared with plasma gasification, detonation USS gasification does not need enormous electric power with unnecessary and energy-consuming gas–plasma transition.

Microstructure and Ablation Behavior of Low-Pressure Plasma Sprayed ZrB2 Coatings Down to 100 Pa.

The effect of chamber pressure on the microstructure and ablation behavior of ZrB2 coatings deposited by low-pressure plasma spraying was investigated. The results showed that as the spray chamber pressure further was reduced to less than 50 kPa, the porosity of the coating deposited at the same distance decreased with the chamber pressure, and the coating prepared under 100 Pa presented the lowest porosity of about 0.89%. The ablation performance test subjected to high-temperature plasma jet revealed that the linear ablation rate of ZrB2 coating increased with the porosity of the coating. As a result, among the ZrB2 coatings deposited at chamber pressures of 100 Pa, 5 kPa, 10 kPa and 50 kPa, the dense coating deposited at 100 Pa showed the lowest ablation rate of 0.33 µm/s. The dense ZrB2 coating with a thickness of about 100 μm was able to withstand 300 s ablation by a plasma flame with a net power of 25 kW resulting in an ablating coating surface temperature of about 2000 °C. The ablation mechanism of the coating was also examined.

Multi-machine SOLPS-ITER comparison of impurity seeded H-mode radiative divertor regimes with metal walls

SOLPS-ITER modelling databases of three tokamaks—ASDEX-Upgrade, JET and ITER with fluid drifts activated are compared to understand the dependence of edge plasma performance on machine size and other global parameters. Two medium Z extrinsic radiating impurity species (Ne and N) are considered. It is demonstrated that N is better kept in the divertor region than Ne in semi-detached and detached divertor conditions due to smaller first ionization potential (FIP effect). Together with the fact that Ne radiates more efficiently at higher plasma temperatures, this leads to an increase in the efficiency of Ne for divertor heat load control with increasing machine size. In larger machines such as JET and ITER Ne can be as efficient a radiator as N while for ASDEX-Upgrade Ne easily leads to radiation from the pedestal and loss of H-mode stability. The relative roles of various physical effects are compared for the three tokamaks based on both whole databases and in more details for chosen semi-detached regimes with comparable fraction of radiated power. It is shown that for smaller machines drift effects are more significant and divertor asymmetries more pronounced.

Nonlinear development of absolute Raman backscatter in ignition-scale direct-drive coronal conditions

Motivated by a resurgence of interest in stimulated Raman scattering (SRS) in direct-drive inertial confinement fusion, we use Vlasov–Maxwell simulations to investigate the nonlinear saturation and associated hot electron production for absolute SRS backscatter near the quarter-critical density. The simulated plasma conditions are relevant to recent planar target experiments on the National Ignition Facility [Rosenberg et al., Phys. Rev. Lett. 120, 055001 (2018)]. It is discovered that wave–wave interactions dominate over kinetic effects in the nonlinear development of instability with clear signatures of the Langmuir decay instability (LDI) cascade and modulational instability of the primary electron plasma wave. Spectral broadening of the scattered light is shown to occur by two mechanisms: via a long wavelength modulation of the electron density—caused by the ponderomotive action of the near-turning point Airy-like structure of the SRS light—and by seeding of SRS by the LDI cascade. Hot electrons are produced at a level that is ≲1% of the incident laser energy by acceleration in the turbulent spectrum associated with the LDI cascade. Despite the high electron plasma temperature, collisions are shown to be important and have the effect of moderating the LDI cascade. The effect of collisions is shown to have a more dramatic effect on hot electron production than on the SRS reflectivity.

Silicon nanorod formation from powder feedstock through co-condensation in plasma flash evaporation and its feasibility for lithium-ion batteries

Si nanowires/nanorods are known to enhance the cycle performance of the lithium-ion batteries. However, viable high throughput production of Si nanomaterials has not yet attained as it requires in general expensive gas source and low-rate and multiple-step approach. As one of the potential approaches, in this work, we report the fast-rate Si nanorod synthesis from low-cost powder source by the modified plasma flash evaporation and the fundamental principle of structural formation during gas co-condensation. In this process, while Si vapors are formed in high temperature plasma jet, molten copper droplets are produced separately at the low temperature region as catalysts for growth of silicon nanorods. Si rods with several micrometers long and a few hundred of nanometers in diameter were produced in a single process at rates up to 40 µm s−1. The growth of the Si nanorods from powder source is primarily characterized by the vapor–liquid–solid growth which is accelerated by the heat extraction at the growth point. The battery cells with the Si nanorods as the anode have shown that a higher capacity and better cyclability is achieved for the nanorods with higher aspect ratios.

Detection of micro-toxic heavy metals in commercial ink powder brands via short-long orthogonal dual pulse LIPs and ICP-OES spectroscopic techniques for environmental protection

ABSTRACT We successfully offer a quantitative and qualitative analysis of the micro-toxic elements that are found in various brands of commercial ink powders (CIPs) available in Saudi Arabia employing short-long orthogonal double-pulse laser-induced plasma spectroscopy (SLODP-LIPS), and an inductively coupled plasma-optical emission spectrometer (ICP-OES). The compositional analysis exploiting the fast detection SLODP-LIPS geometry is based on the received emission spectra of the laser-generated ink plasma flare to promote the SNR (signal-to-noise ratio) compared to the single-pulse (SP) LIPS geometry. The investigated elemental composition of CIPs brands was compared with ICP-OES. The emission optical spectra of the CIPs contain spectral lines of aluminium, antimony, cadmium, calcium, carbon, chromium, copper, lead, iron, potassium, silicon, sodium, and zinc, with varying intensities. To overwhelm the struggle of inadequate SP-LIPS sensitivity or calibration-free LIPS (CF-LIPS) routine characterisation of the tested material and to accomplish a greater emitting volume, grander atomised mass, the lower detection limit, and higher plasma temperature, a double-pulse alternate for sample vaporisation were exercised in our work. The density and electron temperature of the spectral lines of the pertinent elements were deduced by stark-broadening and Boltzmann plot, with an average of about 1.23 × 1018 cm−3 and 9300 ± 200 K, respectively. It was found that both outcomes from SLODP-LIPS and ICP-OES were in greater agreement. The analysis of different commercial ink brands shows that SLODP-LIPS is a potent scheme for the analysis of the micro-toxic trace element in any solids.

Modeling and Estimation of Break Arc Extinction Distance in Low Voltage DC Systems

Recently, as DC power generation and DC loads such as renewable energy and EVs increase, the need for a low-voltage direct current (LVDC) distribution system has gradually emerged. The DC system has various advantages, such as system stability, transmission efficiency, and connectivity to renewable power generation compared to AC distribution systems. One of the important technical issues for commercialization of DC distribution system is safety. Since the DC system does not have a current zero point, unlike the AC system, a breaking arc accompanied by a high-temperature plasma is easily generated when the circuit is cut off. The arc can cause fire accidents that threaten people and facilities. In order to prevent customers and facilities from the accidents caused by the arc in the DC system, a study on the characteristics of the DC breaking arc is necessary. An important factor of characteristics for the DC breaking arc fault is an arc extinction distance at which the DC breaking arc is completely extinguished. There are two major behaviors in DC breaking arc; one is active behavior where the arc voltage is inversely related with the arc current for a given gap distance, the other is passive behavior where the arc voltage is negatively proportional to the arc current according to Kirchhoff’s voltage rule. This paper combines the two arc characteristics together to establish a DC breaking arc model, and proposes a method to estimate the arc extinction distance. Experiment results verify the method under various power and load conditions.

Probe method to measure the electromagnetic field in a plasma by Poynting vector conversion

In this paper, a high-precision electromagnetic measurement system suitable for a high-temperature and high-speed plasma is built to provide a platform for scientific research on the interaction mechanism of the electromagnetic fields and a plasma. This paper presents a method to measure the electromagnetic field inside a plasma by using a probe and Poynting vector conversion, which is a new and completely different method from the traditional method of measuring the electromagnetic field inside plasma. In addition, for this system and method, this work designs a microstrip antenna probe that can suppress multipath effects. This method is confirmed to be valid and usable after closed-loop verification by the CST software.

SRS-SBS competition and nonlinear laser energy absorption in a high temperature plasma

Stimulated Raman and Brillouin scattering of laser radiation in a plasma corona are outstanding issues for the inertial confinement fusion. Stimulated Raman scattering may produce absorption of a significant fraction of laser energy near the plasma quarter critical density associated with plasma cavitation and generation of hot electrons. By contrast, stimulated Brillouin scattering operates in a lower density plasma and prevents the laser light access to the absorption region. In the present paper, we report the results of analysis of competition of these two parametric instabilities with a series of one-dimensional kinetic simulations of laser-plasma interactions. We revised several flexible methods for controlling the SRS-SBS competition in inertial fusion plasmas. Suppression of SBS favors SRS excitation, electron acceleration and cavitation. The latter process makes an important contribution to the laser absorption by trapping the backscattered light. Consequently, by controlling the Brillouin backscattering through variation such plasma parameters as ion acoustic wave damping, divergence of the plasma expansion velocity or the laser bandwidth, we demonstrate the possibility of controlling the level of nonlinear laser absorption and scattering in a hot, weakly collisional plasma.

Insight into BN Impurity Formation during Boron Nitride Nanotube Synthesis by High-Temperature Plasma.

The high-temperature plasma process has demonstrated great potential in growing high-quality boron nitride nanotubes (BNNTs) with small diameters (∼5 nm) and few walls (3–4 walls) and led to successful commercialization with a high production rate approaching 20 g/h. However, the process is still accompanied by the production of BN impurities (e.g., a-BN, BN shell, BN flakes) whose physicochemical properties are similar to those of BNNTs. This renders the post-purification process very challenging and thus hampers the development of their practical applications. In this study, we have employed both experimental and numerical approaches for a mechanistic understanding of BN impurity formation in the high-temperature plasma process. This study suggests that the flow structure of the plasma jet (e.g., laminar or turbulent) plays a key role in the formation of BN impurities by dictating the transport phenomena of BNNT seeds (e.g., B droplets), which play an important role in BNNT nucleation. We discussed that the turbulence enhances the radial diffusion of B droplets as well as their interparticle coagulation, which leads to a significant reduction in the population of effective BNNT seeds in the BNNT growth zone (T < 4000 K). This results in the generation of unreacted BN precursors (e.g., B-N-H species) in the BNNT growth zone that eventually self-assemble into BN impurities. Our numerical simulation also suggests that a higher thermal energy input makes the flow more turbulent in the BNNT growth zone due to the elevated velocity difference between the plasma jet and ambient cold gas. This finding provides critical insight into the process design that can suppress the BN impurity formation in the high-temperature plasma process.