Theory of High-Voltage Glow Discharge with the Generation of a Monoenergetic Electron Beam
- PDF / 365,817 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 36 Downloads / 191 Views
IED PHYSICS
Theory of High-Voltage Glow Discharge with the Generation of a Monoenergetic Electron Beam T. M. Sapronovaa, * and K. N. Ulyanova, ** a Branch
of the Russian Federal Nuclear Center–Zababakhin All-Russia Research Institute of Technical Physics (VNIITF), Moscow, 111259 Russia *e-mail: [email protected] **e-mail: [email protected] Received December 4, 2018; revised December 4, 2018; accepted December 4, 2018
Abstract—A kinetic theory of high-voltage glow discharge (HVGD) is developed. The Poisson equation in the space charge layer is solved taking into account the flow of ions coming from the plasma into the layer, the ionization of gas in the layer via electrons, ions, and fast atoms. On the cathode there is a potential and kinetic extraction of electrons from the surface. For different values of the gas density and secondary emission yield, the current–voltage characteristic is calculated, the dimensions of the space charge layer are determined, and electric field distributions in the layer are present, as well as other HVGD characteristics. The proposed mathematical model can be used to calculate the characteristics of electron accelerators based upon HVGD. DOI: 10.1134/S1063780X19110084
INTRODUCTION A high voltage glow discharge (HVGD) is an anomalous glow discharge in the left-hand branch of the Paschen curve at voltages of 5–150 kV [1–4]. The HVGD current density at U ≈ 100 kV can reach values on the order of 1 A/cm2. Electrons exit the cathode due to potential extraction via positive ions, as well as the kinetic extraction during bombardment of the cathode via ions and fast atoms, which are formed during charge exchange in a space charge layer. All voltage is applied to the layer, therefore the electrons are accelerated in the layer and form an almost monoenergetic beam. The effective secondary electron emission yield in HVGD at U ≈ 30–150 kV can reach very high values (10–20); therefore, electron accelerators that use HVGD have a high efficiency (on the order of 0.90–0.98). In this work, the kinetic theory of HVGD is developed. The Poisson equation in the layer is solved taking into account the flow of ions from the plasma; ionization of the gas in the layer via electrons, ions, and fast atoms; the formation of a flow of fast atoms via ion charge exchange; and secondary electron emission under the action of fast ions and atoms. For various voltages, current densities, and gas densities, the layer size, effective secondary electron emission yield for ions and fast atoms, electric field distribution, ion flux density, and fast atoms are calculated. The current– voltage characteristics (CVC) of the discharge are calculated.
MATHEMATICAL MODEL We consider a discharge model consisting of a space charge layer size x1 in size and a plasma size of L. The discharge voltage ϕ1 is applied to the layer and the ion current of density ji(0) flows into the layer from the plasma boundary. The origin is at the boundary of the plasma and the layer, and the coordinate axis is directed toward the cathode. The electr
Data Loading...
