Pretty similar, maybe less flexible (Score 1)

If this thruster works, the VASIMR people could stop messing around with their ICRH (resonant ion heater) in the expanding section of their plasma. VASIMR creates a helicon plasma, lets it flow out one end (a one-sided magnetic mirror), and adds ion heating in the expanding plasma. The 'double layer' forms due to expanding a plasma in a one-sided magnetic mirror. I don't know is the VASIMR people have looked for a double layer, but they probably would find one if they tried. The hoped-for improvement of VASIMR is that you can gain additional ion energy, over the double-layer voltage, through conservation of the magnetic moment. It's maybe not so easy to single-pass heat ions, however. One issue with both concepts: I think that they assume a very high ionization fraction; efficiency per input gas is pretty important here. Additional issue with the double-layer idea: I've never seen a power balance -- I don't know how the input RF power is converted to directional ion momentum. But I might be ignorant. I (thereby) don't know how you can control the double-layer, and thereby the thrust and SI).