Except that they also tested a dummy unit with the resonance chamber futzed, so any gross physical effects from coronal discharge, convection etc, should have shown up on that as well.
I don't believe this means much of anything, other than, "the working unit probably had coronal discharge, and the dummy didn't."
That's certainly a lot easier to believe than the result they got. If, on the other hand, they observed the same sized effect in a decent vacuum, I would be more inclined to believe it. The fact that this test didn't take place in a vacuum, despite already being in a vacuum chamber ought to make people wonder a bit.
Having fed microwaves into vacuum chambers my own self: if the torsion pendulum was already in there, there is absolutely no reason this experiment wasn't run in at least a rough vacuum. I can understand not going to UHV if the cavity things are dirty or have crap which outgasses, but there is no excuse for not running this experiment in a rough vacuum.
