Electron mobility calculations for mercury-argon low pressure gas discharges

Abstract

A new formula is derived which gives electron mobility values in argon in good agreement with experiment and calculation. The effect of mercury on electron mobility in argon is expressed as a correction factor. The theoretical expression obtained is applied to discharge conditions for which exact results are known, and the results are compared. The values of mu e obtained have been used to calculate axial electron density, showing good agreement with experiment.

Unification of field emission and space charge limited emission with collisions

“…43 A matched asymptotic analysis of plasma sheath behavior showed that the maximum current density J transitions from CL scaling, J / V 3=2 =D 2 , to MG scaling, J / V 2 =D 3 , by incorporating electron mobility l, defined as v d ¼ lE, where v d is the drift velocity and E is the electric field, into the fluid equation for electron motion. 44 Thus, asymptotic studies have demonstrated the transition from FN to CL 17 and CL to MG; 45 however, no study has comprehensively assessed the transition between all three electron emission mechanisms. Given the necessity of incorporating collisions into electron emission theory for either D % k at atmospheric pressure or SCLE for imperfect vacuum, this letter assesses the transitions between FN, MG, and CL by including electron mobility into the equation for electron motion.…”

“…We start with a one-dimensional, planar diode with the cathode at x ¼ 0 and the anode at x ¼ D, fixed at V with respect to the cathode. The gap is filled with a neutral gas with electron mobility l, which varies inversely with pressure P. 45 We assume electron emission from the cathode with negligible initial (t ¼ 0) velocity and accelerated by the surface electric field E s ¼ E(0), or x 0 ð Þ ¼ 0; v 0 ð Þ ¼ 0; a 0 ð Þ ¼ eE s =m. Coupling Poisson's equation with continuity, J ¼ env, where e, n, and v are the electron charge, number density, and velocity, respectively, yields…”

“…For argon, l A ¼ 1:148 Â 10 9 =ðT 1:55 e P A0 Þ, where T e is the electron temperature in K, l A is the argon electron mobility in m 2 =ðVsÞ, and P A0 is the reduced pressure of argon in Torr. 45 Obtaining T e from mv 2 d =2 ¼ k B T e , where k B is the Boltzmann constant, gives P A0 ¼ 243 Torr. For nitrogen, v e ¼ 3:3 Â 10 6 ffiffiffiffiffiffiffiffi ffi E=P p…”

Investigation of a -discharge plasma under an increased pressure of Ar and in narrow tubes

“…Estimations show that, under the discharge conditions in question, this model must include the birth of charged particles due to collisions of excited mercury atoms [17]. The roles of other processes which could manifest themselves under the higher pressure of gases, namely, the influence of elastic collisions between electrons and mercury atoms on the electron mobility [18] and the influence of elastic collisions between electrons and inert gas atoms on the electron energy balance, are unimportant. For instance, in the case of 'classical' luminescent lamps, according to [18], the first process has to be taken into account at the mercury vapour pressure corresponding to the temperature of a mercury bath T Hg > 60 • C. The essentially higher pressure of a rare gas in compact luminescent lamps makes it possible not to take into consideration elastic collisions between electrons and mercury atoms up to T Hg = 80 • C. The second processelastic collisions between electrons and rare gas atomsand its influence on the electron energy balance are, as estimation shows, inessential for a (Hg + Ar) discharge plasma at p Ar < 30 Torr and N 0 > 2 × 10 14 cm −3 (T Hg > 40 • C).…”

Modelling of low-pressure Ar+Hg discharge with high electric current densities

“…The electric current equation is where ,u,(r) denotes the electron mobility in a mixture of mercury and argon. We adopted here the expression of pe given by Chen and Jones (1984).…”