Performance of a magnetic multipole line-cusp argon ion thruster

A 17-cm-diam line-cusp ion thruster was evaluated with inert gases which are candidate propellants for onorbit and orbit transfer propulsion functions for large space systems. A semiempirical relationship was generated to predict thruster beam current in terms of plasma parameters which would allow initial thruster optimization without ion extraction and the associated large vacuum facilities. The sensitivity of performance to changes in discharge electrode configurations and magnetic circuit was evaluated and is presented. After final optimization a propellant utilization efficiency, uncorrected for multiply charged ions, of 0.9 was obtained at a discharge chamber power expenditure of 260 W per beam ampere. These performance parameters are the highest yet achieved with argon propellant. Nomenclature A = number of anode tubes As = screen grid open area, m2 B = magnetic field strength, T Bz = axial magnetic field strength at cathode, mT C = length of cylindrical shell, cm D = distance between opposite anodes, cm e = electronic charge = 1.6 x 10 ~19 °C G = screen grid diameter, cm JB = ion beam current, A k =1.38xlO~ 23 JK- 1 L = anode length, cm M = magnetic field strength over anodes, mT mi — ion mass, kg