Field in gap klystron resonator

[xXTurner]

Hello, colleagues. I am currently doing research on klystron resonators. While calculating the eigenmodes of the resonator, I started to study its fields in the gap and came across an interesting picture at higher frequencies. Can you suggest how modes with such fields can be described? I realise that this is most likely the highest type of oscillations. It's a double gap klystron resonator. It just seems to me to be some strange behaviour of the fields in the resonator gap. Usually the field pattern is in-phase or anti-phase direction of electric field vectors. I.e. when vectors are directed only in one direction or in different directions in the whole gap.