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Diagnosing ratio of electron density to collision frequency of plasma surrounding scaled model in a shock tube using low-frequency alternating magnetic field phase shift
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作者 吴明兴 谢楷 +3 位作者 刘艳 徐晗 张宝 田得阳 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第5期519-530,共12页
A non-contact low-frequency(LF)method of diagnosing the plasma surrounding a scaled model in a shock tube is proposed.This method utilizes the phase shift occurring after the transmission of an LF alternating magnetic... A non-contact low-frequency(LF)method of diagnosing the plasma surrounding a scaled model in a shock tube is proposed.This method utilizes the phase shift occurring after the transmission of an LF alternating magnetic field through the plasma to directly measure the ratio of the plasma loop average electron density to collision frequency.An equivalent circuit model is used to analyze the relationship of the phase shift of the magnetic field component of LF electromagnetic waves with the plasma electron density and collision frequency.The applicable range of the LF method on a given plasma scale is analyzed.The upper diagnostic limit for the ratio of the electron density(unit:m^(-3))to collision frequency(unit:Hz)exceeds 1×10^(11),enabling an electron density to exceed 1×10^(20)m^(-3)and a collision frequency to be less than 1 GHz.In this work,the feasibility of using the LF phase shift to implement the plasma diagnosis is also assessed.Diagnosis experiments on shock tube equipment are conducted by using both the electrostatic probe method and LF method.By comparing the diagnostic results of the two methods,the inversion results are relatively consistent with each other,thereby preliminarily verifying the feasibility of the LF method.The ratio of the electron density to the collision frequency has a relatively uniform distribution during the plasma stabilization.The LF diagnostic path is a loop around the model,which is suitable for diagnosing the plasma that surrounds the model.Finally,the causes of diagnostic discrepancy between the two methods are analyzed.The proposed method provides a new avenue for diagnosing high-density enveloping plasma. 展开更多
关键词 low-frequency alternating magnetic field phase shift shock-tube plasma diagnosis electron density collision frequency
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Impact of the Collisional Plasma on the Propagation of Millimeter Waves
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作者 袁忠才 时家明 +1 位作者 汪家春 许波 《Plasma Science and Technology》 SCIE EI CAS CSCD 2004年第2期2265-2268,共4页
The plasma generated in the low-altitude atmosphere is of high collision frequencies. In this paper, the transmission coefficients of millimeter(MM) waves normally incident upon the plasma with high collision frequenc... The plasma generated in the low-altitude atmosphere is of high collision frequencies. In this paper, the transmission coefficients of millimeter(MM) waves normally incident upon the plasma with high collision frequencies are calculated and analyzed. The experimental results of reflection and attenuation are presented for the eight-millimeter waves propagating through the plasma. Both the calculated experimental results indicate that the MM-waves concerned are attenuated significantly and reflected weakly, when propagating through the plasma of high collision frequencies. 展开更多
关键词 high collision frequencies PLASMA MILLIMETER-WAVES
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Measurement of Electron Density and Ion Collision Frequency with Dual Assisted Grounded Electrode DBD in Atmospheric Pressure Helium Plasma Jet
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作者 周秋娇 齐冰 +2 位作者 黄建军 潘丽竹 刘英 《Plasma Science and Technology》 SCIE EI CAS CSCD 2016年第4期400-405,共6页
The properties of a helium atmospheric-pressure plasma jet(APPJ)are diagnosed with a dual assisted grounded electrode dielectric barrier discharge device.In the glow discharge,we captured the current waveforms at th... The properties of a helium atmospheric-pressure plasma jet(APPJ)are diagnosed with a dual assisted grounded electrode dielectric barrier discharge device.In the glow discharge,we captured the current waveforms at the positions of the three grounded rings.From the current waveforms,the time delay between the adjacent positions of the rings is employed to calculate the plasma bullet velocity of the helium APPJ.Moreover,the electron density is deduced from a model combining with the time delay and current intensity,which is about 10^(11)cm^(-3).In addition,The ion-neutral particles collision frequency in the radial direction is calculated from the current phase difference between two rings,which is on the order of 10~7 Hz.The results are helpful for understanding the basic properties of APPJs. 展开更多
关键词 atmospheric plasma plasma bullet velocity electron density collision frequency
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Analytical Expressions of Dual-Frequency Plasma Diagnostic Theory 被引量:3
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作者 程立 时家明 许波 《Plasma Science and Technology》 SCIE EI CAS CSCD 2012年第1期37-39,共3页
Based on the fundamental ideas concerning microwave attenuation in plasma, we obtain a new expression of transmission attenuation of microwaves as a function of the incident wave frequency. And with reasonable hypothe... Based on the fundamental ideas concerning microwave attenuation in plasma, we obtain a new expression of transmission attenuation of microwaves as a function of the incident wave frequency. And with reasonable hypothesis, analytical forms of the electron density and the electron-neutral collision frequency are derived from the equations of the transmission attenuation of microwaves at two near frequencies. This method gives an effective and easy approach to diagnose the unmagnetized plasma. 展开更多
关键词 PLASMA diagnosis DUAL-FREQUENCY ATTENUATION electron density electron-neutral collision frequency
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Power law of particle size distributions in water treatment processes
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作者 王在刚 徐勇鹏 +1 位作者 刘广奇 崔福义 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2010年第3期308-312,共5页
In this paper,the power law of particle size distributions (PSDs) in conventional water treatment processes is developed. After measuring the particle size distributions of raw-water,settled water and filtered water,a... In this paper,the power law of particle size distributions (PSDs) in conventional water treatment processes is developed. After measuring the particle size distributions of raw-water,settled water and filtered water,a mathematical model between particle diameter and the amount of particles was studied. The value of collision frequency factor β in the PSDs model can be used to represent the collision behavior of particles ,and can be used as foundation exponent to choose suitable coagulation to accelerate particles aggregation. At the same time,the relationship between the value of parameter K and the total particles volume V was deduced. K is defined as particle volume exponent,which can represent the total volume of particles. The degression degree of K shows the removal efficiency of potable water treatment units. 展开更多
关键词 micro-particles particle size distributions (PSDs) particles collision frequency factor β particle volume exponent K
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The Absorbing Properties of Two-Dimensional Plasma Photonic Crystals
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作者 亓丽梅 李超 +1 位作者 方广有 高翔 《Plasma Science and Technology》 SCIE EI CAS CSCD 2015年第1期4-9,共6页
Plasma photonic crystals composed of periodic plasma and dielectric materials have attracted considerable attention because of their tunable photonic band gaps,but only their band structures or negative refractive ind... Plasma photonic crystals composed of periodic plasma and dielectric materials have attracted considerable attention because of their tunable photonic band gaps,but only their band structures or negative refractive index properties have been addressed in previous works.In this paper,through studying the transmission and reflection characteristics of two types of twodimensional plasma photonic crystals,it is found that plasma photonic crystals play an important role in absorbing waves,and they show broader band and higher amplitude absorption characteristics than bulk plasmas.Also,the absorption of plasma photonic crystals can be tuned via plasma parameters;varying the collision frequency can make the bandwidth and amplitude tunable,but cannot change the central frequency,whereas varying the plasma frequency would control both the location and the amplitude of the absorbers.These features of plasma photonic crystals have potential for terahertz tunable absorber applications. 展开更多
关键词 plasma photonic crystal absorber tunable plasma frequency collision frequency
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Interaction between the core and the edge for ion cyclotron resonance heating based on artificial absorption plasma model
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作者 Zhuoqi LIU Jiahui ZHANG +4 位作者 Kaibang WU Xinjun ZHANG Chengming QIN Feng WANG Zhengxiong WANG 《Plasma Science and Technology》 SCIE EI CAS 2024年第10期65-72,共8页
In numerical simulations of the ion cyclotron range of frequencies(ICRF)wave heating scheme,core solvers usually focus on wave propagation and absorption mechanisms within the core plasma region.However,the realistic ... In numerical simulations of the ion cyclotron range of frequencies(ICRF)wave heating scheme,core solvers usually focus on wave propagation and absorption mechanisms within the core plasma region.However,the realistic scrape-off layer(SOL)plasma is usually simplified,making it difficult to have deeper understanding of wave propagation and absorption within the SOL.In this work,we employ a cold plasma assumption and an artificial absorption mechanism based on the approach of reference(Zhang et al 2022 Nucl.Fusion 62076032),to study wave propagation and absorption in the realistic SOL plasma of the EAST.During the exponential decay of the total coupled power with respect to the toroidal mode numbers,several fluctuations are observed in the case of low collisional frequencies.The fluctuations may be caused by the cavity modes associated with specific toroidal mode numbers.Due to the presence of cut-off densities,the edge power losses and the total coupled power exhibit different behaviors before and after the cut-off layer is“open”.Furthermore,the simulation results obtained from the kinetic model in reference(Zhang et al 2022 Nucl.Fusion 62076032)is discussed.This suggests that both the core-edge combined model and the artificial mechanism are capable of simulating wave propagation and absorption. 展开更多
关键词 ICRF EAST artificial mechanism collisional frequency
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The collision frequency of electron-neutralparticle in weakly ionized plasmas with non-Maxwellian velocity distributions
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作者 Hong Wang Jiulin Du Rui Huo 《Communications in Theoretical Physics》 SCIE CAS CSCD 2021年第9期113-123,共11页
The collision frequencies of electron-neutral-particle in weakly ionized complex plasmas with the non-Maxwellian velocity distributions are studied.The average collision frequencies of electron-neutral-particle in pla... The collision frequencies of electron-neutral-particle in weakly ionized complex plasmas with the non-Maxwellian velocity distributions are studied.The average collision frequencies of electron-neutral-particle in plasmas are accurately derived.We find that these collision frequencies are significantly dependent on the power-law spectral indices of non-Maxwellian distribution functions and so they are generally different from the collision frequencies in plasmas with a Maxwellian velocity distribution,which will affect the transport properties of the charged particles in plasmas.Numerically analyses are made to show the roles of the spectral indices in the average collision frequencies respectively. 展开更多
关键词 non-Maxwellian velocity distribution collision frequency weakly ionized plasma
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Calculation of collision frequency function for aerosol particles in free molecule regime in presence of force fields
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作者 Xiaowei LUO Yannick BENICHOU Suyuan YU 《Frontiers in Energy》 SCIE CSCD 2013年第4期506-510,共5页
The collision frequency function for aerosol particles has already been calculated for the free molecule regime and for the continuum range. The present work, taking into account the influence of internal force fields... The collision frequency function for aerosol particles has already been calculated for the free molecule regime and for the continuum range. The present work, taking into account the influence of internal force fields such as magnetic force, electric force and molecular forces, created by particles themselves, recalculated the collision frequency in the case of particles much smaller than the mean free path of the gas (free molecule regime). Attractive forces increase naturally the collision frequency, while repulsive forces decrease it. The calculation was performed for all types of central forces deriving from a potential, including Coulomb forces and Van der Waals forces. 展开更多
关键词 aerosol particles collision frequency function COAGULATION
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