Research on Similarity Law of Glow Discharge in Argon at Low Pressure by Numerical Simulation

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Based on a two-dimensional (2-D) fluid model, the transition processes of discharges in a hollow cathode at low pressure are observed by changing three parameters, i.e., applied voltage U 0 , gas pressure p, and external circuit ballast resistance R b. The voltage-current characteristic curves, electron density distributions, and electric potential distributions of different discharge operating points in a hollow cathode are obtained. The transition processes are characterized by the voltage-current characteristic curves, the electron density distributions, and the electrical potential distributions. The transition modes observed from the voltage-current characteristics include the low-current abnormal mode, normal mode, and high-current abnormal mode. Increasing the applied voltage U 0 can have a similar effect on the discharge transition processes to decreasing the ballast resistance. By increasing U 0 from 200 V to 500 V and decreasing R b from 5000 kX to 100 kX independently, it is observed that the discharge transfers from the outside to the inside of the hollow cavity, thus forming the virtual anode potential. By increasing the gas pressure p from 50 Pa to 5 kPa, the discharge also moves into the hollow cavity from the outside; however, a further increase in the gas pressure leads to the discharge escaping from the hollow cavity. Simulation results and characterizations for different parameters are presented for the transition properties of low-pressure discharges in a hollow cathode. It is verified that the hollow cathode discharge only exists under certain ranges of the above parameters. Published by AIP Publishing.

Section: Model Descriptionmentioning

confidence: 99%

Transition characteristics of low-pressure discharges in a hollow cathode

Verboncoeur

Christlieb

et al. 2017

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“…The charged particle density relations (SL4-SL6) can be derived based on SL2, SL3, the current continuity equation, and the Poisson equation, which was illustrated in our previous work. 16 The average electron temperature relation (SL7) can be explained in general when the reduced electric fields in two similar discharges are the same. The time interval relation (SL8) can be derived based on the gap length relation and the same mean velocity of the particles.…”

Section: Similarity Laws and Discharge Processesmentioning

confidence: 99%

“…No matter what the discharge mechanisms are, the requirements of the similarity law on the particle productions from different physical processes are the same, which can be generally derived from the similarity relations in Table I. According to the similarity relations of the particle density (SL4 and SL5) and time interval relation (SL8), the relationship of the charged particle production rate (dn/dt) in two similar discharge gaps is expressed as 12,16 No.…”

Section: Similarity Laws and Discharge Processesmentioning

confidence: 99%

“…10,11 The similarity laws, including the well-known Paschen's law, are potential techniques to predict discharge parameters in ultra-small scale discharges when the direct diagnostics are hardly possible. [12][13][14][15][16] Based on the recent interests in microdischarges, such as the lab-on-a-chip concept, researchers are attempting to extend the applicability of the similarity law to sub-millimeter and even nano-scale discharges. 17,18 With the similarity relations being valid, the prediction of the discharge parameters of a scaled-up and scaled-down systems will be less expensive, reducing the prediction to the proportionality conversions.…”

Section: Introductionmentioning

confidence: 99%

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Investigation on the effect of nonlinear processes on similarity law in high-pressure argon discharges

Parsey

Verboncoeur

et al. 2017

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In this paper, the effect of nonlinear processes (such as three-body collisions and stepwise ionizations) on the similarity law in high-pressure argon discharges has been studied by the use of the Kinetic Global Model framework. In the discharge model, the ground state argon atoms (Ar), electrons (e), atom ions (Ar þ ), molecular ions (Ar 2 þ ), and fourteen argon excited levels Ar*(4s and 4p) are considered. The steady-state electron and ion densities are obtained with nonlinear processes included and excluded in the designed models, respectively. It is found that in similar gas gaps, keeping the product of gas pressure and linear dimension unchanged, with the nonlinear processes included, the normalized density relations deviate from the similarity relations gradually as the scale-up factor decreases. Without the nonlinear processes, the parameter relations are in good agreement with the similarity law predictions. Furthermore, the pressure and the dimension effects are also investigated separately with and without the nonlinear processes. It is shown that the gas pressure effect on the results is less obvious than the dimension effect. Without the nonlinear processes, the pressure and the dimension effects could be estimated from one to the other based on the similarity relations. Published by AIP Publishing. https://doi.

“…In recent years, the validity of the similarity law for various discharge modes has attracted more attention from different groups. [5][6][7][8][9] There are many ways to investigate the validity of the similarity law, such as experimental measurements on external parameters (breakdown voltage, discharge current, etc.) and inner parameters (particle density, electric field, etc.…”

Section: Introductionmentioning

confidence: 99%

Investigation on the similarity law of low-pressure glow discharges based on the light intensity distributions in geometrically similar gaps

Wang

Zou

et al. 2017

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Experimental investigation of the light intensity distributions of a low-pressure glow discharge is carried out in several pairs of geometrically similar plane-parallel gaps, of which the aspect ratios and the products of the linear dimension and the gas pressure are the same. The discharge images are captured using a Charge Coupled Device camera, from which the corresponding axial light intensity distributions are presented. Based on the obtained light intensity distributions, the thicknesses of cathode fall layers were identified by measuring the distance between the peak glow position and the cathode boundary. The influence of the discharge current on the light intensity distributions on the geometrically similar gaps is also investigated. It was found that, for discharges in each pair of geometrically similar gaps, the reduced cathode fall thicknesses are observed to be identical when the discharge currents are the same. The similarity relation of the cathode fall thickness is validated for low-pressure glow discharges in gaps for different aspect ratios. Published by AIP Publishing.