Cavity design for high-frequency axion dark matter detectors
  In an effort to extend the usefulness of microwave cavity detectors to higher axion masses, above ~8 $\mu$eV (~2 GHz), a numerical trade study of cavities was conducted to investigate the merit of using variable periodic post arrays and regulating vane designs for higher-frequency searches. The results show that both designs could be used to develop resonant cavities for high-mass axion searches. Multiple configurations of both methods obtained the scanning sensitivity equivalent to approximately 4 coherently coupled cavities with a single tuning rod. 
I. Stern, A.A. Chisholm, J. Hoskins, P. Sikivie, N.S. Sullivan, D.B.   Tanner, G. Carosi, and K. van Bibber
physics.ins-det