Particle Recycling Research Articles

Gyrokinetic study of collisional resonant magnetic perturbation (RMP)-driven plasma density and heat transport in tokamak edge plasma using a magnetohydrodynamic screened RMP field

The total-f gyrokinetic particle-in-cell code XGC is applied to study various aspects of collisional transport in the tokamak edge pedestal in the presence of resonant magnetic perturbations (RMPs) calculated with M3D-C1. Simulations including the separatrix and scrape-off layer are exercised for a model DIII-D H-mode plasma. Neutral particle recycling is modeled by means of ionization and charge exchange with the plasma. A fully nonlinear Fokker–Planck collision operator is utilized to account for non-Maxwellian edge plasma. The study yields kinetic evidence that (i) neglecting the non-axisymmetric component of the RMP-generated electrostatic potential perturbation could yield a fictitiously high particle pump-out rate in the edge pedestal; that (ii) the experimental level of particle pump-out from the pedestal cannot be provided by collisional transport across Kolmogorov–Arnold–Moser surfaces except across the magnetic separatrix where stochastic magnetic field lines exist; that (iii) the H-mode type electron heat barrier is retained in the steep slope area under the M3D-C1 calculated RMPs; and that (iv) the stochastic electron heat-transport rate around the magnetic separatrix surface is much lower than the prediction by Rechester–Rosenbluth (1978 Phys. Rev. Lett. 40 38–41) and is qualitatively consistent with the experimentally observed rate. Detailed kinetic physics analysis on how the transport fluxes, electrostatic potential perturbation, and -well structure respond to onset of RMPs is also reported.

New approach to the control of particle recycling using divertor pumping in the Large Helical Device

The effect of the divertor pumping on plasmas has been investigated in the Large Helical Device (LHD). A divertor pump which reaches high pumping speed (67 ± 5 m3 s−1 in hydrogen) and high pumping capacity (58 000 Pa m3 in hydrogen) has been developed at LHD. The global particle confinement time (), which is expressed as τp/(1 − R), where τp is the particle confinement time and R is the global recycling coefficient, is used for comparison of operation with and without divertor pumping. After the fueling was stopped, shorter values were obtained in low density plasmas with divertor pumping in comparison with the values without divertor pumping. In this paper, the acceleration of RF wall conditioning by the divertor pumping is also discussed. The effect of the divertor pumping on high density plasmas has been investigated. In high density plasmas obtained by pellet fueling, not only edge density but also core density is reduced by the divertor pumping due to shallower pellet penetration. The control of neutral pressure by the feedback operation of pellet injection and gas puffing likely will be a candidate for the edge density control.

The 210Po / 210Pb disequilibrium in a spring-blooming marginal sea, the Southern Yellow Sea

The Southern Yellow Sea (SYS) is suffering from the increasing environment problems, such as the recurrent algal bloom. The 210Po/210Pb disequilibrium is very useful for assessing particulate organic matter dynamics during phytoplankton blooming. In this study, 23 surface samples were collected from the SYS after the 2009 spring bloom, to investigate the disequilibrium between these two radionuclides. The dissolved 210Pb and particulate 210Pb activities (dpm 100 L−1) in the SYS surface waters varied within a wide range, with values of 2.28–17.82 (average 7.63 ± 4.25, n = 23) and 1.08–13.56 (average: 4.72 ± 2.84, n = 23). A deficiency of 210Po relative to 210Pb in the seawater was observed. The distribution coefficients (Kd) of the two radionuclides varied considerably (from 104 to 106 L kg−1), and higher Kd values of 210Po relative to 210Pb generally increased with POC/TSM (when above 10%). The negative correlation (R = 0.97, P = 0.012) between 210Po/210Pb activity ratios and primary productivities in all four seasons implies that marine biological processes may enhance the disequilibrium between 210Po and 210Pb. The residence times of 210Po and 210Pb were estimated to be 7–206 days and 14–105 days, respectively. The longer 210Po residence times might be connected with several processes, e.g., 210Po uptake by marine particles or plankton, and recycling of fine-grained particles in the surface water. These short residence times of 210Po and 210Pb might indicate the existence of efficient scavenging processes, causing heavy metals and pollutants to deposit into the Yellow Sea (YS) bottom sediments.

Driven transport on a flexible polymer with particle recycling: A model inspired by transcription and translation.

Many theoretical works have attempted to coarse grain gene expression at the level of transcription and translation via frameworks based on exclusion processes. Usually in these models the three-dimensional conformation of the substrates (DNA and mRNA) is neglected, and particles move on a static unidimensional lattice in contact to an infinite reservoir. In this work we generalize the paradigmatic exclusion process and study the transport of particles along a unidimensional polymerlike flexible lattice immersed in a three-dimensional particle reservoir. We study the recycling of particles in the reservoir, how the transport is influenced by the global conformation of the lattice, and, in turn, how particle density dictates the structure of the polymer.

Recycling of hazardous diesel soot particles into a high performance solar evaporation device

In recent years, solar-induced interfacial heating of water has proven to be an efficient technique to produce steam while harnessing solar energy. Herein, we report diesel soot coated on cotton as a novel photothermal membrane for highly efficient solar steam generation. A facile fabrication procedure was successfully followed to synthesize the photothermal membrane with hazardous diesel soot particles obtained from vehicular exhaust, and cotton cloth. In this photothermal membrane, the diesel soot particles embedded in the cotton cloth substrate help in the absorption of incident solar illumination, and the excellent hydrophilicity of cotton cloth assists in the rapid supply of water at the air-water interface to produce constant steam. As a result, the evaporation rate of water using the photothermal membrane was 3 times the bare water system with an excellent photothermal efficiency of 91.75% under 1 sun illumination. The photothermal membrane was also successful in water desalination using a simple laboratory setup. The results of this work should motivate further research of diesel soot and other waste products for high efficiency water evaporation and its applications.

Study of liquid metal surface wave damping in the presence of magnetic fields and electrical currents

Abstract Experiments and predictions of surface wave damping in liquid metal due to a surface aligned magnetic field and externally regulated j × B force are presented. Fast-flowing, liquid-metal plasma facing components (LM-PFCs) are a proposed alternative to solid PFCs that are unable to handle the high heat flux, thermal stresses, and radiation damage in a tokamak. The significant technical challenges associated with LM-PFCs compared to solid PFCs are justified by greater heat flux management, self-healing properties, and reduced particle recycling. However, undesirable engineering challenges such as evaporation and splashing of the liquid metal introduce excessive impurities into the plasma and degrade plasma performance. Evaporation may be avoided through high-speed flow that limits temperature rise of the liquid metal by reducing heat flux exposure time, but as flow speed increases the surface may become more turbulent and prone to splashing and uneven surfaces. Wave damping is one mechanism that reduces surface disturbance and thus the chances of liquid metal impurity introduction into the plasma. Experiments on the Liquid Metal eXperiment Upgrade (LMX-U) examined damping under the influence of transverse magnetic fields and vertically directed Lorentz force.

A Review of Recent Studies on Particle Recycling From Liquid Metals With/Without Convection Under Plasma Bombardment

From the recent experiments on liquid metal plasma-facing components, convection appears to play an important role in maintaining reduced recycling conditions. Either it is natural or forced convection, the transport of the implanted particle is accelerated in the depth direction whereby the surface saturation would be delayed or avoided. Reviewed in this paper are some of the recent studies on particle recycling from liquid metals under plasma bombardment with the emphasis on liquid convection effects. Natural convection has been observed to enhance deuterium plasma-driven permeation. In addition, the effects of J × B forced convection on particle recycling have been extensively studied under steady-state hydrogen, deuterium, helium, and argon plasma bombardment. Also, preliminary fluid dynamics analysis has been conducted to interpret these experimental observations.

G4Linac_MT, an easy-to-use Geant4-based code for modeling medical linear accelerator

In this paper, we present G4Linac_MT, a simple-to-use open source code developed to facilitate the use of the Geant4 C++ toolkit for the simulation of a medical linear accelerator (linac). This multithreaded code encapsulates several well-developed C++ modules serving to handle the complexity of coding geometry and material, to easy plot histograms of various physics quantities, to auto-merge output data created by all working threads into a single file, to well-estimate the number of simulated primary particles required to achieve data with a statistical uncertainty < 1% and also the CPU time required for, to use a set of variance reduction techniques as bremsstrahlung splitting, particle recycling, particle rotational splitting and stacking mechanism, to use a new format of phase space file based on HDF5-C++ scientific library which has been developed specially for this code. In order to minimize human effort required by Geant4 coding and validating of a linac, the code comes with a Java-based GUI application which contains separated GUI modules for linac head simulation, dose calculation, data analysis, geometry modeling and gamma index calculation. Results from Monte Carlo simulations of linac head of a Saturne 43 12 MV configuring a 10 × 10 cm2 radiation field are showed in order to demonstrate the G4Linac_MT capabilities. Thus, comparisons between simulated dosimetric functions and measured ones in a water phantom have been established by using a gamma index method and the results show a good agreement within 2.6%-1 mm accuracy. In addition, after optimizing variance reduction techniques, the overall CPU time spent by this multithreaded code has been decreased by a factor of 7.

Demonstration of suppression of dust generation and partial reduction of the hydrogen retention by tungsten coated graphite divertor tiles in LHD

Three sets of tungsten coated graphite divertor tiles (VPS-W tiles) were installed in the closed helical divertor of the Large Helical Device (LHD) instead of the graphite divertor tiles in the 2012FY plasma campaign for examining the plasma wall interaction (PWI) with divertor plasma. The first wall panels and divertor tiles of the LHD consist of stainless steels (SUS316L) and graphite, respectively. The carbon based mixed-material deposition layer including a very small amount of Fe element has been formed on not only the divertor tiles but also the first walls near the divertor tiles through the PWI processes. Such a mixed layer often causes undesirable influences for maintaining a long pulse discharge in LHD, e.g., changing the particle recycling properties and dust generation. After the single plasma campaign of the 2012FY, we confirmed drastic suppression of the mixed-material deposition layer on the first wall panels just under the VPS-W tiles. On the other hand, carbon based mixed-material deposition layer was formed on the VPS-W tile surface, where the amount of the hydrogen retention was estimated to be over ∼4 × 1021 H/m2. If we would want further suppression of the hydrogen retention on the VPS-W tiles, the plasma facing components should be replaced to a full metal wall to avoid formation of the carbon co-deposition layer.

Results from an improved flowing liquid lithium limiter with increased flow uniformity in high power plasmas in EAST

Significant engineering and physic progress was made by the upgrade of a flowing liquid lithium limiter (FLiLi) inserted into EAST H-mode discharges in 2016. The progress includes an improvement of liquid Li coverage uniformity, no macroscopic surface erosion by plasma materials interaction, effective removal of 55% of the discharge heat flux using high pressure He cooling during ohmic discharges, and the demonstrated ability to restart Li flow for a second experiment performed a week after the first. With increasing Li flow rate, fuel particle recycling and Fe impurity radiation gradually decreased, and plasma performance slightly improved, but there was no impact on the edge tungsten influx. No obvious Li bursts appeared during operation with up to about 4.5 MW auxiliary heating power with peak heat flux reaching ~4 MW m−2 on FLiLi. In addition, a gradual mitigation of edge localized mode (ELM) activity was observed with FLiLi operation. Finally, short-lived ELM-free phases were observed for the first time in EAST during FLiLi insertion, with increasing τE and transient H98(y, 2) < 2.

Experimental validation of a model for particle recycling and tungsten erosion during ELMs in the DIII-D divertor

A refined version of the Fundamenksi-Moulton 'free-streaming' model (FSM) for the dynamics of divertor density, particle flux, and heat flux during edge localized modes (ELMs) is presented. This model depends only on inter-ELM pedestal and divertor conditions and, crucially, incorporates particle recycling: a FSM with recycling model, FSRM. The effective particle recycling coefficient, Reff, is the only empirical fitting parameter in the FSRM. The predictions of the FSRM are systematically tested against a DIII-D database of ELM ion and energy fluence measurements and are shown to be consistent with the model across a wide range of pedestal and divertor conditions using a constant value of 0.96 for Reff . Predictions for W sputtering during ELMs are developed based on the FSRM. It is concluded that energetic free-streaming D+ ions and C6+ impurities are the dominant contributors to the intra-ELM gross erosion of W in the DIII-D divertor, i.e., recycling ions and impurities have relatively little impact on the total W sputtering rate. These calculations are also shown to be consistent with spectroscopic measurements of W gross erosion for three different pedestal conditions after incorporating the strong electron density dependence of the WI 400.8 nm ionizations/photon (S/XB) coefficient.

Why do protoplanetary disks appear not massive enough to form the known exoplanet population?

When and how planets form in protoplanetary disks is still a topic of discussion. Exoplanet detection surveys and protoplanetary disk surveys are now providing results that are leading to new insights. We collect the masses of confirmed exoplanets and compare their dependence on stellar mass with the same dependence for protoplanetary disk masses measured in ∼1–3 Myr old star-forming regions. We recalculated the disk masses using the new estimates of their distances derived fromGaiaDR2 parallaxes. We note that single and multiple exoplanetary systems form two different populations, probably pointing to a different formation mechanism for massive giant planets around very low-mass stars. While expecting that the mass in exoplanetary systems is much lower than the measured disk masses, we instead find that exoplanetary systems masses are comparable or higher than the most massive disks. This same result is found by converting the measured planet masses into heavy element content (core masses for the giant planets and full masses for the super-Earth systems) and by comparing this value with the disk dust masses. Unless disk dust masses are heavily underestimated, this is a big conundrum. An extremely efficient recycling of dust particles in the disk cannot solve this conundrum. This implies that either the cores of planets have formed very rapidly (&lt;0.1–1 Myr) and a large amount of gas is expelled on the same timescales from the disk, or that disks are continuously replenished by fresh planet-forming material from the environment. These hypotheses can be tested by measuring disk masses in even younger targets and by better understanding if and how the disks are replenished by their surroundings.

The effects of particle recycling on the divertor plasma: A particle-in-cell with Monte Carlo collision simulation

A Particle-In-Cell (PIC) with Monte Carlo Collision (MCC) model is applied to study the effects of particle recycling on divertor plasma in the present work. The simulation domain is the scrape-off layer of the tokamak in one-dimension along the magnetic field line. At the divertor plate, the reflected deuterium atoms (D) and thermally released deuterium molecules (D2) are considered. The collisions between the plasma particles (e and D+) and recycled neutral particles (D and D2) are described by the MCC method. It is found that the recycled neutral particles have a great impact on divertor plasma. The effects of different collisions on the plasma are simulated and discussed. Moreover, the impacts of target materials on the plasma are simulated by comparing the divertor with Carbon (C) and Tungsten (W) targets. The simulation results show that the energy and momentum losses of the C target are larger than those of the W target in the divertor region even without considering the impurity particles, whereas the W target has a more remarkable influence on the core plasma.

A fast low-to-high confinement mode bifurcation dynamics in the boundary-plasma gyrokinetic code XGC1

A fast edge turbulence suppression event has been simulated in the electrostatic version of the gyrokinetic particle-in-cell code XGC1 in a realistic diverted tokamak edge geometry under neutral particle recycling. The results show that the sequence of turbulent Reynolds stress followed by neoclassical ion orbit-loss driven together conspire to form the sustaining radial electric field shear and to quench turbulent transport just inside the last closed magnetic flux surface. The main suppression action is located in a thin radial layer around ψN≃0.96–0.98, where ψN is the normalized poloidal flux, with the time scale ∼0.1 ms.

Electrochemical Preparation of Nanostructured Silicon from Rice Husks As a Sustainable Source for High Performance Anode in Secondary Lithium Ion Battery

Silicon is one of the most promising anode material candidates for lithium ion batteries because of its high specific capacity (3579 mAh/g), which is ten times higher than existing graphite anodes. One of the most important issues toward commercialization is the high cost of nanostructured silicon related to the complex fabrication amd expansive raw materials. In this work, we demonstrate the recycling of pure silicon nanoporous particles from rice husks (RHs) directly, which is an abundant agricultural byproduct (108 tons/year) in worldwide. Besides, the massive amount of RHs has unique nanoporous structure on the RHs to preform the function as protection and ventilation. In the first step of our experiment, the metal ions in the RHs by HCl leaching were removed and then incinerate the leached RHs to produce silica with nanostructure. Next step, we convert the silica to silicon by electrochemical reduction method, which is a potential process for large scale reduction in a relative low tempareture compared with conventional carbothermal reduction. Owing to the nanoporous nature, these recovered silicon nano-particles show high performance as lithium ion battery anodes, with high reversible capacity and long cycle life. Recycling RHs as the source of silicon, this work presents a process to produce Si based Li-ion battery with cost effective, energy-efficient, green, and potential of large scale synthesis in industry. Key words: rice husk, electrochemical reduction, Li-ion battery

Cleaner production of polyurethane foam: Replacement of conventional raw materials, assessment of fire resistance and environmental impact

Abstract This work presents the results in the field of materials engineering, and they are related to recycling of paper production waste sludge particles at amounts of 10 wt% and 20 wt% in tall oil polyol-based rigid polyurethane foam with and without tris (1-chloro 2-propyl) phosphate flame retardant. The impact of both systems on physical and mechanical properties, thermal stability, fire resistance and ignitability is studied. Paper production waste sludge particles filled rigid polyurethane foams display better fire performance thus resulting into reduction of the emission of CO2 and CO as well as reduction in average heat release rate. Scanning electron microscopy has shown that paper waste sludge particles and tris (1-chloro 2-propyl) phosphate together act systematically, and synergism between two materials may be observed. It is as well determined that paper production waste sludge particles reduce thermal conductivity by approx. 15% for polyurethane foam with paper production waste sludge particles and by approx. 13% for polyurethane foam with paper production waste sludge particles and conventional flame retardant. Moreover, the substitution of tris (1-chloro 2-propyl) phosphate, petroleum based polyol and hydroflurocarbons with 10 wt% and 20 wt% of PPWS particles, tall oil polyol and water reduces carbon dioxide emission by 60.8% and 39.6%, respectively, contributing to cleaner production of rigid polyurethane foam.

Hydrothermal modification and recycling of nonmetallic particles from waste print circuit boards

Nonmetallic particles recycled from waste print circuit boards (NPRPs) were modified by a hydrothermal treatment method and the catalysts, solvents, temperature and time were investigated, which affected the modification effect of NPRPs. The mild hydrothermal treatment method does not need high temperature, and would not cause secondary pollution. Further, the modified NPRPs were used as the raw materials for the epoxy resin and glass fibers/epoxy resin composites, which were prepared by pouring and hot-pressing method. The mechanical properties and morphology of the composites were discussed. The results showed that relative intensity of the hydroxyl bonds on the surface of NPRPs increased 58.9% after modification. The mechanical tests revealed that both flexural and impact properties of the composites can be significantly improved by adding the modified NPRPs. Particularly, the maximum increment of flexural strength, flexural modulus and impact strength of the epoxy matrix composites with 30% modified NPRPs is 40.1%, 80.0% and 79.0%, respectively. Hydrothermal treatment can modify surface of NPRPs successfully and modified NPRPs can not only improve the properties of the composites, but also reduce the production cost of the composites and environmental pollution. Thus, we develop a new way to recycle nonmetallic materials of waste print circuit boards and the highest level of waste material recycling with the raw materials-products-raw materials closed cycle can be realized through the hydrothermal modification and reuse of NPRPs.

Recycling and reuse of rusted iron particles containing core-shell Fe-FeOOH for ibuprofen removal: Adsorption and persulfate-based advanced oxidation

Abstract This paper describes the reuse of rusted iron particles recycled from used heat pads to remove ibuprofen through adsorption and persulfate-based advanced oxidation. The recycled rusted iron particles (RRIP) contained α-FeOOH and amorphous FeOOH on the shell and zero valet iron (Fe0) in the core. The RRIP had an adsorption capacity of 3.47 mg/g towards ibuprofen, which was 4.8 times higher than that of the synthetic α-FeOOH. The stronger ibuprofen adsorption of RRIP was due to the larger specific surface area. The RRIP activated persulfate to generate both sulfate radicals (SO4− ) and hydroxyl radicals (OH ), which degraded the adsorbed and dissolved ibuprofen. Persulfate was activated primarily by surface bound Fe(II) that was in-situ formed from the interactions of the surface FeOOH with the Fe0 cores. The adsorption enriched IBP on the FeOOH surface and accelerated the overall IBP degradation. RRIP had a saturation magnetization of 0.6 emu/g, which made it magnetically separable. The RRIP magnetically separated from the treated water were repeatedly reused with less than a 10% drop in adsorption capacity in each cycle. Ibuprofen was degraded by SO4− and OH through hydroxylation, decarboxylation and sequential oxidation. The recycled waste iron particles are demonstrated to be promising adsorbents-and-catalysts for the removal of pharmaceuticals and personal care products from contaminated water by adsorption, and together with persulfate, by catalytic advanced oxidation.

Establishment of a low recycling state with full density control by active pumping of the closed helical divertor at LHD

Superior control of particle recycling and hence full governance of plasma density has been established in the Large Helical Device (LHD) using largely enhanced active pumping of the closed helical divertor (CHD). In-vessel cryo-sorption pumping systems inside the CHD in five out of ten inner toroidal divertor sections have been developed and installed step by step in the LHD. The total effective pumping speed obtained was 67 ± 5 m3 s−1 in hydrogen, which is approximately seven times larger than previously obtained. As a result, a low recycling state was observed with CHD pumping for the first time in LHD featuring excellent density control even under intense pellet fueling conditions. A global particle confinement time () is used for comparison of operation with and without the CHD pumping. The was evaluated from the density decay after the fueling of hydrogen pellet injection or gas puffing in NBI plasmas. A reliably low base density before the fueling and short after the fueling were obtained during the CHD pumping, demonstrating for the first time full control of the particle balance with active pumping in the CHD.

The effects of magnetic nanoparticles embedded with SA/PVA and pH on chemical-mechanical polishing wastewater and magnetic particle regeneration and recycle

Experiments were conducted using sodium alginate (SA) and polyvinyl alcohol (PVA) as embedded materials for Fe3O4 magnetic nanoparticles (MNPs). The materials provided excellent protection to the embedded MNPs in low-pH conditions. This study observed and compared the adsorption capacity of the unaltered and embedded MNPs. At pH 3 and without additional magnetic fields, the wastewater turbidity removal rate of the embedded MNPs reached a maximum of 95%, similar to that of the unaltered MNPs. Moreover, this study examined the recyclability and reusability of the unaltered and embedded MNPs and discovered that the embedded MNPs could be reused up to seven times. Overall, the use of SA/PVA prevented MNPs from disintegrating and contaminating the wastewater through the dissolution of Fe ions. SA and PVA also increased the reusability of the unaltered MNPs.