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Validity of the two-term Boltzmann approximation employed in the fluid model for high-power microwave breakdown in gas

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Chinese Physics B 2014年第5期23卷 380-384页

作者：赵朋程廖成杨丹钟选明 Institute of Electromagnetics Southwest Jiaotong University

The electron energy distribution function （EEDF）, predicted by the Boltzmann equation solver BOLSIG＋ based on the two-term approximation, is introduced into the fluid model for simulating the high-power microwave （HPM） breakdown in argon, nitrogen, and air, and its validity is examined by comparing with the results of particle-in-cell Monte Carlo collision （PIC/MCC） simulations as well as the experimental data. Numerical results show that, the breakdown time of the fluid model with the Maxwellian EEDF matches that of the PIC/MCC simulations in nitrogen; however, in argon under high pressures, the results from the Maxwellian EEDF were poor. This is due to an overestimation of the energy tail of the Maxwellian EEDF in argon breakdown. The prediction of the fluid model with the BOLSIG＋ EEDF, however, agrees very well with the PIC/MCC prediction in nitrogen and argon over a wide range of pressures. The accuracy of the fluid model with the BOLSIG＋ EEDF is also verified by the experimental results of the air breakdown.

关键词： fluid model electron energy distribution function gas breakdown particle-in-cell Monte Carlocollision (PIC/MCC) simulation

Ammonia pyrolysis oxidation excited by nanosecond pulsed discharge:Global/fluid models hybrid solution

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Journal of Energy Chemistry 2025年第1期100卷 385-396页

作者： Mingming Zhang Hanyu Wu Qi Chen Jiaxin Yang Bonan Liu School of Mechanical Electronic and Control Engineering Beijing Jiaotong University China University of Petroleum

The kinetic characteristics of plasma-assisted oxidative pyrolysis of ammonia are studied by using the global/fluid models hybrid solution ***,the stable products of plasma-assisted oxidative pyrolysis of ammonia are *** results show that the consumption of NH3/O2and the production of N2/H2change linearly with the increase of voltage,which indicates the decoupling of nonequilibrium molecular excitation and oxidative pyrolysis of ammonia at low ***,the detailed reaction kinetics mechanism of ammonia oxidative pyrolysis stimulated by a nanosecond pulse voltage at low pressure and room temperature is *** on the reaction path analysis,the simplified mechanism is *** detailed and simplified mechanism simulation results are compared with experimental data to verify the accuracy of the simplified ***,based on the simplified mechanism,the fluid model of ammonia oxidative pyrolysis stimulated by the nanosecond pulse plasma is established to study the pre-sheath/sheath behavior and the resultant consumption and formation of key *** results show that the generation,development,and propagation of the pre-sheath have a great influence on the formation and consumption of *** consumption of NH3by the cathode pre-sheath is greater than that by the anode pre-sheath,but the opposite is true for OH and O（1S）.However,within the sheath,almost all reactions do not ***,by changing the parameters of nanosecond pulse power supply voltage,it is found that the electron number density,electron current density,and applied peak voltages are not the direct reasons for the structural changes of the sheath and ***,the discharge interval has little effect on the sheath structure and gas mixture *** research results of this paper not only help to understand the kinetic promotion of non-equilibrium excitation in the process of oxidative pyrolysis but also help to explore th

关键词： Nanosecond pulsed discharge Ammonia Oxidative pyrolysis fluid model Global model

Effect of pressure and space between electrodes on the deposition of SiN_(x)H_(y)films in a capacitively coupled plasma reactor

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Chinese Physics B 2021年第5期30卷 507-512页

作者： Meryem Grari CifAllah Zoheir Yasser Yousfi Abdelhak Benbrik University Mohamed First Department of PhysicsLETSER LaboratoryOujdaMorocco University Mohamed First Department of MathematicsLANO LaboratoryOujdaMorocco

The fluid model,also called the macroscopic model,is commonly used to simulate low temperature and low pressure radiofrequency plasma *** varying the parameters of the model,numerical simulation allows us to study several cases,providing us the physico-chemical information that is often difficult to obtain *** this work,using the fluid model,we employ numerical simulation to show the effect of pressure and space between the reactor electrodes on the fundamental properties of silicon plasma diluted with ammonia and *** results show the evolution of the fundamental characteristics of the plasma discharge as a function of the variation of the pressure and the distance between the *** examining the pressure-distance product in a range between 0.3 Torr 2.7 cm and 0.7 Torr 4 cm,we have determined the optimal pressure-distance product that allows better deposition of hydrogenated silicon nitride(SiN_(x)H_(y))films which is 0.7 Torr 2.7 cm.

关键词： fluid model numerical simulation SiN_(x)H_(y) capacitively coupled plasma reactor

Conversion of an atomic to a molecular argon ion and low pressure argon relaxation

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Chinese Physics B 2016年第1期25卷 697-705页

作者： M N Stankov A P Jovanovie V Lj Markovic S N Stamenkovic Department of Physics Faculty of Sciences and MathematicsUniversity of Ni Viegradska 33Ni 18001Serbia

The dominant process in relaxation of DC glow discharge between two plane parallel electrodes in argon at pressure 200 Pa is analyzed by measuring the breakdown time delay and by analytical and numerical models. By using the approx- imate analytical model it is found that the relaxation in a range from 20 to 60 ms in afterglow is dominated by Ar＋ ions, produced by atomic-to-molecular conversion of Ar＋ ions in the first several milliseconds after the cessation of the discharge. This conversion is confirmed by the presence of double-Gaussian distribution for the formative time delay, as well as con- version maxima in a set of memory curves measured in different conditions. Finally, the numerical one-dimensional （1D） model for determining the number densities of dominant particles in stationary DC glow discharge and two-dimensional （2D） model for the relaxation are used to confirm the previous assumptions and to determine the corresponding collision and transport coefficients of dominant species and processes.

关键词： argon discharge afterglow relaxation fluid model plasma reactions

Simulation of Capacitively Coupled Dual-Frequency N_2,O_2,N_2/O_2 Discharges:Effects of External Parameters on Plasma Characteristics

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Plasma Science and Technology 2014年第4期16卷 335-343页

作者：尤左伟戴忠玲王友年 School of Physics and Optoelectronic Technology Dalian University of Technology

A one-dimensional fluid model is adopted to simulate the characteristics of N2, O2, and N2/O2 dual-frequency （DF） capacitively coupled plasmas （CCPs） under typical conditions in PECVD technologies. Not only the ground, the excited states but also the vibration levels of the main species are considered. The study focuses on the influence of external parameters such as matching of the high-frequency （HF） and low-frequency （LF）, HF and LF of the voltage sources, as well as discharge pressures, on physical characteristics of discharges. The results show that the decoupling of the two sources is possible by increasing the applied HF, the electron density and ion flux are determined only by the HF of the voltage source, whereas the LF has a little influence on the plasma characteristics. In addition, the matching of frequency affects the characteristics of discharges to some extent. Fhrthermore, the pressure is a main external parameter affecting the characteristics of discharges, and a small amount of oxygen in N2 plasma can efficiently increase N＋ ion flux incident onto the electrode and the density of N atom.

关键词： CCP dual-frequency fluid model N2 discharge O2 discharge

STABILITY OF HLPPS AND MODIFIED HLPPS POLICIES FOR THE RE-ENTRANT LINE

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Journal of Systems Science & Complexity 2010年第6期23卷 1239-1246页

作者： Jiankui YANG School of Science Beijing University of Posts and Telecommunications Beijing 100876 China.

For a re-entrant line operating under the HLPPS service policy, the stability was proved by Bramson in 1996. A simple proof for the stability of the fluid model is given here. Also, the HLPPS service policy is modified according to the proportion of potential jobs and the stability of the fluid model under the modified one is proved.

关键词： fluid model re-entrant line stability.

Influence of a centered dielectric tube on inductively coupled plasma source: Chamber structures and plasma characteristics

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Chinese Physics B 2017年第7期26卷 250-255页

作者：毕振华洪义雷光玖王帅王友年刘东平 Liaoning Key Laboratory of Optoelectronic Films & Materials School of Physics and Materials EngineeringDalian Nationalities University Southwestern Institute of Physics Physics Department School of Science Northeastern University School of Physics and Optoelectronic Technology Dalian University of Technology

A high-density RF ion source is an essential part of a neutral beam injector. In this study, the authors attempt to retrofit an original regular RF ion source reactor by inserting a thin dielectric tube through the symmetric axis of the discharge chamber. With the aid of this inner tube, the reactor is capable of generating a radial magnetic field instead of the original transverse magnetic field, which solves the E × B drift problem in the current RF ion source structure. To study the disturbance of the dielectric tube, a fluid model is introduced to study the plasma parameters with or without the internal dielectric tube, based on the inductively coupled plasma（ICP） reactor. The simulation results show that while introducing the internal dielectric tube into the ICP reactor, both the plasma density and plasma potential have minor influence during the discharge process, and there is good uniformity at the extraction region. The influence of the control parameters reveals that the plasma densities at the extraction region decrease first and subsequently slow down while enhancing the diffusion region.

关键词： neutral beam ion source inductively coupled plasma(ICP) fluid model

Gas flow characteristics of argon inductively coupled plasma and advections of plasma species under incompressible and compressible flows

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Chinese Physics B 2018年第12期27卷 348-360页

作者： Shu-Xia Zhao Zhao Feng Physics Department Dalian University of Technology

In this work, incompressible and compressible flows of background gas are characterized in argon inductively coupled plasma by using a fluid model, and the respective influence of the two flows on the plasma properties is specified. In the incompressible flow, only the velocity variable is calculated, while in the compressible flow, both the velocity and density variables are calculated. The compressible flow is more realistic; nevertheless, a comparison of the two types of flow is convenient for people to investigate the respective role of velocity and density variables. The peripheral symmetric profile of metastable density near the chamber sidewall is broken in the incompressible flow. At the compressible flow, the electron density increases and the electron temperature decreases. Meanwhile, the metastable density peak shifts to the dielectric window from the discharge center, besides for the peripheral density profile distortion, similar to the incompressible *** velocity profile at incompressible flow is not altered when changing the inlet velocity, whereas clear peak shift of velocity profile from the inlet to the outlet at compressible flow is observed as increasing the gas flow rate. The shift of velocity peak is more obvious at low pressures for it is easy to compress the rarefied gas. The velocity profile variations at compressible flow show people the concrete residing processes of background molecule and plasma species in the chamber at different flow rates. Of more significance is it implied that in the usual linear method that people use to calculate the residence time, one important parameter in the gas flow dynamics, needs to be rectified. The spatial profile of pressure simulated exhibits obvious spatial gradient. This is helpful for experimentalists to understand their gas pressure measurements that are always taken at the chamber outlet. At the end, the work specification and limitations are listed.

关键词： gas flow inductively coupled plasma compressible flow fluid model

Numerical Study on Atmospheric Pressure DBD in Helium:Single-breakdown and Multi-breakdown Discharges

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Plasma Science and Technology 2011年第6期13卷 724-729页

作者：王小华杨爱军荣命哲刘定新 State Key Laboratory of Electrical Insulation and Power Equipments Xi'an Jiaotong University

A 1-D fluid model for homogeneous dielectric barrier discharge （DBD） in helium is presented, aimed at unraveling the spatial-temporal characteristics of two basic discharge regimes： single-breakdown and multi-breakdown discharges. Discharge currents, gap voltages, charge densities, electron temperature and electric field profiles of the two regimes make it clear that these two regimes are qualitatively different. It is found that the multi-breakdown discharge has a more homogeneous flux on dielectrics compared to the single-breakdown discharge.

关键词： fluid model single-breakdown discharge multi-breakdown discharge dielectric barrier discharge