Energy efficiency of electron plasma emitters
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AND VACUUM DISCHARGES
Energy Efficiency of Electron Plasma Emitters V. G. Zalesski Polotsk State University, Novopolotsk, 211440 Belarus email: [email protected] Received: April 26, 2010
Abstract—Electron emission influence from gasdischarge plasma on plasma emitter energy parameters is considered. It is shown, that electron emission from plasma is accompanied by energy contribution redistri bution in the gasdischarge from plasma emitter supplies sources—the gasdischarge power supply and the accelerating voltage power supply. Some modes of electron emission as a result can be realized: “a probe mea surements mode,” “a transitive mode,” and “a full switching mode.” DOI: 10.1134/S1063780X11090145
INTRODUCTION Using plasma as an emitter of electrons or ions assumes realization of optimal conditions for forma tion of emitting plasma which provide efficiency and technological applicability of such emitters [1]. Since parameters of emitting plasma and mechanisms of for mation of emission current are interconnected, then the influence of emission must be reflected on power characteristics of the plasma emitter and as a result lead to changing of its currentvoltage characteristics. Power efficiency is usually used as the main power characteristic for plasma emitters of charged particles which is defined through extraction efficiency α (ratio of emission current Ie and discharge current Id) [2] I Ie α . H = e = = Ud P Id Ud
(1)
Power efficiency H characterizes power which is consumed from an electric source of discharge at a given value of emission current. It was established experimentally for some types of efficient plasma emitters that the discharge voltage Ud decreases with increasing of extraction efficiency. However, this fact was not reflected in existing theories of plasma emit ters. At the same time one may assume that growth of extraction efficiency excites mechanisms which pro mote increasing of intensity of ionization processes in plasma at the expense of part of energy contributed by an accelerating voltage source into discharge. That is why, in our opinion, it is appropriate to use an addi tional power parameter for a deeper comprehension of processes in plasma emitter Ud Id ( 1 – α ) κ = , U d0 I d0
(2)
where Ud0 and Id0 are the discharge voltage and current in the absence of forced extraction of electrons from
plasma (α 0); and Ud and Id are the voltage and current of discharge at some value of extraction effi ciency. The generally accepted theory of formation of electric emission current in plasma emitters [3] is based on assumption about the infinite emission abil ity of plasma (horizontal currentvoltage characteris tic of discharge) and it reflects two emission modes: with low efficiency of extraction of electrons from plasma α—“the probe measurements mode”; and extraction efficiency α close to 1—“full switching mode.” Within the framework of this theory excitation of plasma by emission of electrons is not considered; therefore, dependences
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