Summary

Dipole- and quadrupole-like modes in the coupling cells oE coaxial and annular-ring coupled structures have been examined up to a frequency of 4 GHz. The quadrupole mode frequencies appear to Lie high enough above the frequency of the accelerating mode to make coupling between the two unlikely. In the annular-ring case ( however, a dipole mode was found very near the accelerating mode frequency. Evidence is presented which suggests that some power may couple between these two modes in a real cavity