Self-sustained criterion with photoionization for positive dc corona plasmas between coaxial cylinders

Abstract

The positive dc corona plasmas between coaxial cylinders in air under the application of a self-sustained criterion with photoionization are investigated in this paper. A photon absorption function suitable for cylindrical electrode, which can characterize the total photons within the ionization region, is proposed on the basis of the classic corona onset criteria. Based on the general fluid model with the self-sustained criterion, the role of photoionization in the ionization region is clarified. It is found that the surface electric field keeps constant under a relatively low corona current, while it is slightly weakened with the increase of the corona current. Similar tendencies can be found under different conductor radii and relative air densities. The small change of the surface electric field will become more significant for the electron density distribution as well as the ionization activity under a high corona current, compared with the results under the assumption of a constant surface field. The assumption that the surface electric field remains constant should be corrected with the increase of the corona current when the energetic electrons with a distance from the conductor surface are concerned.

Revisiting the positive DC corona discharge theory: Beyond Peek's and Townsend's law

“…The small photo-ionization efficiency (typically c < 10 À3 ) results in a very weak correction to the overall positive ion current. This is completely coherent with previous results 22 where the computed positive ion flux is conserved in the outer region, indicating negligible source terms. So, photo-ions can be neglected.…”

“…The coefficient c is the secondary electron efficiency, identical to the one introduced by Zheng. 22 The effective absorption coefficient is named k (and not l as in Refs. 1 and 22 to avoid confusion with mobility) and kGðr; r 0 Þ is its associated effective absorption function.…”

Ion-impact secondary emission in negative corona with photoionization

“…In weak ionization region, these photoelectrons can be used as seed electrons to produce secondary electron emission avalanche (SEEA). Characteristics for positive direct current corona discharges in air under the action of photoionization has been well developed in recent years, [4][5][6] while the role of photoionization in negative corona has seldom studied so far.…”

The role of photoionization in negative corona discharge

“…8,9 Theory of photoionization is also important in many fields, such as cooling rates in astrophysical 10 and anesthetic method, 11 liquid chromatography-tandem mass spectrometry 12,13 in medical applications. Therefore, more attention should be paid to discover the effect of photoionization which has been well developed in positive corona 5,6,14 while the effect of photoionization in negative corona has seldom studied up to now.…”

“…[1][2][3][4] It occurs if the corona onset voltage is applied to asymmetric electrodes such as a needle and a plate. [5][6][7] In the process of corona discharge, photons are emitted by the collisions of electrons with molecules at the head of the electron avalanche, and a portion of photons will be absorbed by molecules. These photoelectrons in the weakly ionized region can be used as seed electrons to produce new electron avalanche, which called secondary electron emission avalanche (SEEA).…”