  Two cavities in different size with the photonic crystal structure have been
developed for axion searches. In the cavities, the dispersion relation in the
photonic crystal is utilised, and so was named to "DRiPC cavities". The size of
the smaller one is 100 mm x 100 mm x 10 mm, where 16 cylindrical metal poles
with a diameter of 4 mm are introduced in a 4x4 grid at 20 mm intervals. In
this study, the grid interval in x direction in the small size cavity, Lx, was
changed to investigate resonance frequency, Q-value, and electric field profile
at each Lx. The lowest three frequencies have been compared with the ones
simulated by the finite element method to be found in excellent agreement. The
lowest frequency mode could be tuned from 5.10 GHz (Lx = 25.0 mm) to 6.72 GHz
(13.9 mm), centering on 5.87 GHz at Lx = 20 mm. This wide range tunability,
27.7%, was suitable for a search with a modest Q-value. By examining the
electric field distributions with the bead pull method, the lowest frequency
mode at Lx = 16.0 - 25.0 mm were TM010-like. This mode was also obtained in a
larger size cavity (180 mm x 180 mm x 20 mm x 2) with the same photonic crystal
structure. These results led us to conclude a DRiPC cavity has the noble
features for future axion search experiments.
