I've never been able to find the answer to this question - maybe someone on here knows the answer. What were the initial conditions of the ELECTRONS in the experiment? There seems to be the implicit assumption that only the positive ions' state of motion has an effect on the photons being emitted. I recognize that the ions are orders of magnitude more massive than the electrons, and thus their trajectories would be essentially unaffected. But aren't the photons emitted by the JOINT actions of both positive and negative charges? And how did the electrons get past the accelerating grid into the recombination chamber? Could the answer be that the initial conditions of the electrons are "random". And thus the "net" directed activity be that of the positive ions?