The paper Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum (H. White et al, J. Propulsion & Power, November, 2016, http://dx.doi.org/10.2514/1.B36120) refers to an unusually shaped copper cavity with a resonance at about 1.94 GHz. This is described in the quoted section below. (further reading: https://space.stackexchange.com/questions/tagged/emdrive)
Fig. 4 suggests that the Q of this cavity is over 7,000 (7E+03). As far as I can tell there is no suggestion of an unusually conductive coating inside the copper.
My question is about the extremely high Q. I think among those with experience with ~GHz resonant copper cavities should be able to answer this based on experience, without it being too opinion based. Could a copper RF cavity like this be reasonably expected to have a Q > 7000?
I'm curious - with a drive of 50W, what would be the order of magnitude electric fields inside? kV/m? MV/m? I can break this off as a separate question if necessary.
An example of anything close in configuration and Q could be the basis of a "yes" and an example of anything close in configuration, highly optimized, and not even close in Q could be the basis of a "no" answer.
B. Test Article
The RF resonance test article is a copper frustum with an inner diameter of 27.9 cm on the big end, an inner diameter of 15.9 cm on the small end, and an axial length of 22.9 cm. The test article contains a 5.4-cm-thick disk of polyethylene with an outer diameter of 15.6 cm that is mounted to the inside face of the smaller diameter end of the frustum. A 13.5-mm-diam loop antenna drives the system in the TM212 mode at 1937 MHz. Because there are no analytical solutions for the resonant modes of a truncated cone, the use of the term TM212 describes a mode with two nodes in the axial direction and four nodes in the azimuthal direction. A small whip antenna provides feedback to the phase-locked loop (PLL) system. Figure 3 provides a block diagram of the test article’s major elements.
above: Figure 4 from here. Right click to open in a separate window to view clearly as full size, or view at the original link.
above: "Fig. 14 Forward thrust mounting configuration (heat sink is black finned item between test article and amplifier)." from here
above: "Fig. 17 Null thrust mounting configuration, b) view from side" from here