[en] The plane-diode model is used to calculate steady-state parameters (plasma density, plasma potential, and potential extremum) for a strongly biased, collisionless single-ended Q-machine over a wide range of neutralization parameters. By solving the cold-beam dispersion relation in the long-wavelength limit, approximate expressions are obtained for the frequency and growth rate of the Buneman two-stream instability which occurs at sufficiently positive biases. All of these dependences exhibit a characteristic kink at the transition between monotone and non-monotone potential distributions. (Auth.)