Results from a search for cosmic axions

A search experiment has been carried out to look for relic cosmic axions trapped in the halo of our Galaxy and limits on their coupling ${g}_{a\ensuremath{\gamma}\ensuremath{\gamma}}$ and galactic abundance are presented for the axion mass range of ${m}_{a}=(5.4\ensuremath{-}5.9)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ eV. The detector consisted of a tunable high-$Q$ microwave cavity immersed in liquid helium and permeated by a strong magnetic field. A low-noise microwave receiver with a cryogenic HEMT amplifier as its first stage was coupled to the cavity. The noise power within successive cavity bandwidths was spectrum analyzed and searched for narrow peaks resulting from axion-to-photon conversions in the cavity.