As an electric propulsion engineer used to measure thrust in the uN range, what disturbs me much more than thrust levels close to the sensitivity threshold is t

As an electric propulsion engineer used to measure thrust in the uN range, what disturbs me much more than thrust levels close to the sensitivity threshold is the fact that thrust is only detected some 10-20s after the RF is turned on (figs 9,8,13). I am rather confident that there is no physical time scale in the RF generation process that would account for a 10-20s ramp, and this would contradict their own report of the fast RF power stabilization. It definitely looks like thermal drift; in fact, thermal drift is _always_ the first thing to suspect when you get strange measurements with a low thrust balance. It appears as well that the authors have conveniently prepared an answer for this objection with fig.5 which attempts to mislead the reader by suggesting that the very slow evolution of the balance displacement is to be expected as an artifact of the combined effect of thermal drift and RF pulse onset. But conveniently, the time units are arbitrary so that hopefully nobody will notice that RF onset was assumed in that figure to have exactly the same characteristic time as the thermal drift... When all measurements actually show that RF power stabilizes much faster.