CTF3 Cavity Pick-up to Waveguide Spacing

Cross Coupling

The separation between the pick-up in port number 2 and the wall of the waveguide was varied. The curve for separation of 0.2mm looks anomalous. This may be because the cavity was dismantled and reconstructed between this measurement and all the others.

Reflection and Transmission

This time, the separation between two opposing pick-ups and the waveguide walls were varied simultaneously with the other ports terminated.

The loaded Q was measured at each separation using the transmission curves between opposite ports and exponential curves were fitted to the results. The limits of these curves are printed on the graph and give values for the internal Q. In each case, the first point at a spacing of 0.15mm is ignored because it falls in a region where the behavior is different as suggested by the results below.

Combined with Measurements at Finer Spacing

The reflected and transmitted amplitudes suggest the strongest coupling can be found with a separation of 0.1mm

However, the reflection curves also suggest the most resonant frequency is most stable with a separation greater than 0.2mm