Near-wall conductivity effect under a space—charge-saturated sheath in the Hall thruster

Abstract

This paper adopts modified Morozov secondary electron emission model to make research into the impact of the character of space-charge-saturated sheath near the insulated wall of Hall thruster on the near-wall conductivity, by the method of 2D particle simulation (2D+3V). The results show that, due to the sharp increase of collision frequency between the electrons and the wall under the space-charge-saturated sheath, the near wall transport current under this sheath is remarkably higher than that under classical sheath, and equal to the near wall transport current under spatial oscillated sheath in the order of magnitude. However, the transport currents under space-charge-saturated sheath and spatial oscillated sheath are different in the mechanism, causing different current density distribution under the above two sheaths, and a great impact of channel width on the near wall transport current under space-charge-saturated sheath. Hall thruster is a kind of plasma equipment discharging in the configuration of crossed electric and magnetic

Sheath structure in plasma with two species of positive ions and secondary electrons

“…1, the coordinate origin x = 0 is defined as the plasma-sheath boundary, x < 0 is the bulk plasma region and x > 0 is the plasma sheath region. The electron density in the sheath can be described by the Boltzmann distribution in the thermodynamic equilibrium [18][19][20][21][22][23] n e = n e0 exp(eφ /T e ),…”

“…[32] When SEE is taken into consideration in two-ion-species plasma, the critical value of ion velocity at the sheath edge u 10 can be obtained from Eqs. ( 19)- (21), and (23) for the given parameter N 20 . Figure 2(a) shows that the critical value of u 10 increases monotonically with SEE coefficient γ for each of Ar-He, Ar, and Ar-Xe plasmas while N 20 = 0.1.…”

“…For a single-ion sheath, SEE can cause the sheath potential drop and sheath width to decrease, it can even give rise to the sheath instability if the SEE coefficient reaches a critical value γ c (defined as the value when the electric field equals zero at the wall). [18][19][20][21][22][23][24][25] For γ > γ c , the sheath structure becomes complex.…”

Numerical study on the electron—wall interaction in a Hall thruster with segmented electrodes placed at the channel exit

“…[3,4] The electron NWC occurs because electron-wall interaction destroys the steady Hall drift of electron in 𝐸 × 𝐵 direction (where 𝐸 and 𝐵 are axial electric and radial magnetic fields, respectively), which is believed to be responsible for the portion of electron conductivity that is higher than classical value. [4,5] We then can come to a conclusion that the electron NWC caused by electron-wall interaction increases electron current, and thus reducing the discharge efficiency. Moreover, the electron-wall interaction has other influences on the discharge of Hall thruster, such as the potential distribution in discharge channel, [6] the wall temperature effect caused by the energy deposition of incident electron moving toward lateral walls, etc.…”

Characteristics of wall sheath and secondary electron emission under different electron temperatures in a Hall thruster

“…[7][8][9] By improving the secondary electron emission model which was proposed by Morozov, the Harbin Institute of Technology established a 1D fluid sheath model combined with a two-dimensional (2D) particle sheath model within an insulated wall to study the influence of the electronic anisotropic temperature on the nearwall electron current, as well as the effect of a space-chargesaturated sheath on the near-wall conductivity. [10][11][12][13] In addition, the institute established a 1D fluid sheath model, analyzing the influence of the secondary electron emission coefficient on plasma sheath properties in Hall thruster channels numerically. [14][15][16] Fluid simulation, hybrid simulation and particle simulation are often used to numerically model the plasma sheath in Hall thrusters.…”