## Abbreviations  
The following abbreviations are used in this manuscript: \begin{tabular}{l l} \(A\) & Magnetic vector potential \\ \(A_{a}\) & Electron loss area at anode \\ \(A_{as}\) & Total surface area of anode exposed to plasma \\ \(A_{p}\) & Primary electron loss area at anode \\ \(B\) & Magnetic flux density \\ \(B_{cusp}\) & Magnetic field strength at the cusps on the anode wall \\ \(B_{t}\) & Maximum transverse magnetic field between magnets \\ \(d\) & Grid gap \\ \(D\) & Discharge chamber diameter \\ \(D_{s}\) & Screen-grid holes diameter \\ \(e\) & Electron charge \\ \(f_{c}\) & Ion-confinement factor \\ \(g\) & Gravitational acceleration at sea level \\ \(H\) & Magnetic field intensity \\ \(I^{*}\) & Neutral excitation rate \\ \(I_{a}\) & Electron current leaving plasma to anode \\ \(I_{b}\) & Ion-beam current \\ \(I_{d}\) & Discharge current \\ \(I_{e}\) & Current emitted by the hollow cathode \\ \(I_{ia}\) & Ion current lost to the anode \\ \(I_{k}\) & Ion current back to the cathode \\ \(I_{L}\) & Primary electron current lost directly to the anode \\ \(I_{p}\) & Ion-production rate \\ \(I_{s}\) & Ion current to the screen grid \\ \(I_{sp}\) & Specific impulse \\ \(J\) & Free-current density \\ \(k\) & Boltzmann's constant \\ \(Kn\) & Knudsen number \\ \(l\) & Diffusion length \\ \(L_{c}\) & Total length of the magnetic cusps \\ \(m\) & Electron mass \\ \(\dot{m}_{p}\) & Propellant flow rate \\ \(M\) & Ion mass \\ \(n_{e}\) & Electron density in the plasma \\ \(n_{i}\) & Ion density in the plasma \\ \(n_{p}\) & Primary-electron density \\ \(P1\) & Upstream pressure of the injector \\ \(P2\) & Discharge chamber pressure \\ \(P_{in}\) & Total input power \\ \(P_{inc,c}\) & Input power in the discharge chamber \\ \(P_{out,c}\) & Output power in the discharge chamber \\ \(P_{b}\) & Beam power \\ \(r_{e}\) & Larmor radius of plasma electrons \\ \(r_{i}\) & Larmor radius of ions \\ \(r_{p}\) & Larmor radius of primary electrons \\ \(R\) & Ratio of beam voltage to total voltage \\ \(t_{s}\) & Thickness of the screen grid \\ \(T\) & Thrust \\ \(T_{a}\) & Optical transparency of the grid \\ \(T_{e}\) & Electron temperature \\ \(U^{+}\) & Ionization potential \\ \(U^{*}\) & Average excitation potential \\ \(v_{p}\) & Primary-electron velocity \\ \(V_{acc}\) & Accel grid voltage \\ \end{tabular}   
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