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 ga and galactic abundance are presented for the axion mass range of ma=(5.4-5.9)×10-6 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. © 1990 The American Physical Society.