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The preparation technology of micron spherical metal powder has become a common problem in the fields of chip, medical diagnosis, and 3D-printing. In this paper, micron spherical gold powder was prepared by hydrometallurgy process, and high-purity conductive gold ball was prepared by plasma spheroidizing method. The high-purity and highly dispersed gold powder was prepared with the self-made Au-99. 999% as raw material, hydrazine hydrate as reducing agent and PVP as diluent, and the reduction potential was controlled at 1 692 ~ 1 002 mV, 5N micron conductive gold spheres for semiconductor chips are obtained by gas flow crushing and plasma spheroidizing. At present, this method has realized industrialized production of 10 kg, preliminarily solved the problem that the conductive gold ball for domestic chip packaging was monopolized by other countries, and made an important contribution to improving China's chip R & D industry chain, especially the research and development of electronic grade gold raw materials. [ABSTRACT FROM AUTHOR]

Herein, the effect of kinetic damping on the resistive wall mode (RWM) instability in the China nuclear fusion engineering test reactor (CFETR) is numerically studied using the magnetohydrodynamic resistive spectrum-kinetic (MARS-K) code. A CFETR hybrid equilibrium with a plasma current of Ip = 13 MA is adopted. The sum of the electron diamagnetic, plasma rotation, and mode frequencies increases at q = 2 rational surface with increasing plasma rotation frequency. When the sum of the frequencies is less than 0, kinetic damping has a stabilizing effect on RWM. In contrast, when the sum of the frequencies is greater than 0, the kinetic damping has a destabilizing effect on RWM, causing a second unstable branch to appear. Additionally, the effects of plasma pressure and wall distance on the two unstable branches are investigated. The mode frequency is excited with increasing plasma pressure and wall distance. Consequently, the first branch is stabilized and the second branch is destabilized. [ABSTRACT FROM AUTHOR]

A complete 28-GHz/50-kW gyrotron system was developed by the Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang, China, as a plasma heating source for the EXL50 fusion device, a compact spherical tokamak constructed by the ENN Group in 2019. The gyrotron employs a triode magnetron injection gun, a TE02-mode cylindrical cavity, a built-in quasi-optical mode converter, a single-stage depressed collector, and a single-disk boron nitride window. The gyrotron system features a match optical unit, a superconducting magnet, a calorimetric dummy load, a high-voltage power supply system, and other auxiliary components, was delivered to the EXL50 site. In the acceptance test, five successive shots of each power over 50 kW were generated for 30 s at 28 GHz. An average power of 51 kW, a maximum power of 55 kW, and 46% overall efficiency were obtained. The gyrotron system was assembled in the EXL50 and applied to a plasma discharge experiment. The gyrotron is the first practical domestic gyrotron produced for fusion applications in China. The design and test results of this instrument are presented in this article. [ABSTRACT FROM AUTHOR]

BACKGROUND: Pesticides have been widely used to control pests on agricultural products in China, and large amounts of pesticide residues have caused a serious threat to human health. Thus, developing a high‐efficiency pesticide degradation method for fresh vegetables represents a great challenge. The present study investigated the effects of dielectric barrier discharge (DBD) plasma on the degradation of malathion and chlorpyrifos in aqueous solutions and on lettuces. RESULTS: DBD treatment significantly degraded malathion and chlorpyrifos in water and on lettuce. After cold plasma treatment at 80 kV for 180 s, the degradation efficiency of malathion (0.5 μg mL−1) and chlorpyrifos (1.0 μg mL−1) in aqueous solutions reached 64.6% and 62.7%, respectively. The degradation intermediates were explored by HPLC‐mass spectrometry and the DBD plasma degradation pathways of malathion and chlorpyrifos were proposed. There was no significant damage to the quality of lettuces, including color and chlorophyll content, after plasma treatment. Ascorbic acid decreased significantly during long‐term treatment with DBD plasma. To ensure the quality of lettuces during processing, the treatment time was shortened to 120 s. Under this condition, the degradation efficiency of malathion (0.5 mg kg−1) and chlorpyrifos (1.0 mg kg−1) on lettuces was found to be 53.1% and 51.4%. More importantly, we noted that cold plasma treatment significantly inactivated the microorganisms on lettuces. CONCLUSION: The results of the present study show that cold plasma is an effective and safe method for the degradation of organic pesticide residues on fresh vegetables at the same time as retaining the original quality. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

[Display omitted] • Soil depth directly affects dielectric barrier discharge plasma (DBD) processing capacity. • Alkyl radicals improved diesel fuel degradation efficiency during DBD treatment. • Degradation pathway of diesel fuel were proposed. • Experimental results proved the feasibility of heavily diesel-fuel-polluted soil remediation using DBD. Diesel-fuel-polluted soil poses a risk to both the environment and human health. This study assessed the feasibility and efficiency of dielectric barrier discharges (DBD) for the degradation of diesel fuel in soil. At 180 W input power, 3 mm soil depth, initial concentration of 10,000 mg/kg, soil pH of 7.1, and 2% moisture, the degradation efficiency of diesel fuel reached 74% within 40 min of the treatment. The diesel fuel removal efficiency decreased significantly at a soil depth of >3 mm, and increased soil moisture impaired the process. With a high initial diesel fuel concentration, the removal efficiency was high due to the action of alkyl radicals. The most effectively removed hydrocarbons had <17 carbons, and by-products were mainly esters, anhydrides, and long-chain alkanes. The remediation efficiency of the actual petroleum-polluted soil from the Heilongjiang province of China was tested using DBD. The removal efficiency for saturated hydrocarbons was 71% at a power of 180 W for 40 min. Thus, DBD can be used as an efficient method for diesel-fuel-polluted soil remediation. [ABSTRACT FROM AUTHOR]

• The influence of the eddy current generated in the vacuum vessel of the CFQS on the plasma discharge was negligible. • The maximum stress on the CFQS vacuum vessel was less than the allowable level of stainless steel. • The adoption of the induction heating method is difficult because the applied voltage in the modular coils exceeded the allowable voltage. The design activity on the CFQS quasi-axisymmetric stellarator which is conducted as a joint international project is ongoing by National Institute for Fusion Science (NIFS) in Japan and Southwest Jiaotong University (SWJTU) in China. The CFQS magnetic field generating coils consist of sixteen modular coils (MCs) in total with four different types, four poloidal field coils (PFCs), and twelve toroidal field coils (TFCs). In designing fusion devices, eddy currents and electromagnetic (EM) forces on the vacuum vessel (VV) have to be evaluated to verify the mechanical confidence and reliability. In this work, we consider the following three issues, (1) Influence of eddy current induced by external coil current change on the CFQS magnetic confinement, (2) Evaluation of EM force on VV by eddy current under a typical current of the MC and the PFC, and (3) Feasibility check of whether it is possible to heat the CFQS VV by using induction current. [ABSTRACT FROM AUTHOR]