We present measurements of the transmission of radio/microwave pulses through salt in the Cote Blanche salt mine operated by the North American Salt Company in St. Mary Parish , Louisiana .
These results are from data taken in the southwestern region of the 1500 ft. ( 457 m ) deep level of the mine on our third and most recent visit to the mine .
We transmitted and received a fast , high-power , broadband pulse from within three vertical boreholes that were drilled to depths of 100 ft. ( 30 m ) and 200 ft. below the 1500 ft. level using three different pairs of dipole antennas whose bandwidths span 125 to 900 MHz .
By measuring the relative strength of the received pulses between boreholes with separations of 50 m and 169 m , we deduce the attenuation of the signal attributed to the salt medium .
We fit the frequency dependence of the attenuation to a power law and find the best fit field attenuation lengths to be 93 \pm 7 m at 150 MHz , 63 \pm 3 m at 300 MHz , and 36 \pm 2 m at 800 MHz .
This is the most precise measurement of radio attenuation in a natural salt formation to date .
We assess the implications of this measurement for a future neutrino detector in salt .