Measurements of the Suitability of Large Rock Salt Formations for Radio Detection of High Energy Neutrinos

TL;DR

This study evaluates large rock salt formations' potential for high-energy neutrino detection via radio signals, finding some salt domes have sufficiently long attenuation lengths for effective use.

Contribution

It provides the first measurements of radio-frequency attenuation lengths in different salt formations, demonstrating the feasibility of using salt domes as neutrino detection targets.

Findings

Attenuation lengths vary significantly between salt formations.

Hockley mine salt dome shows attenuation lengths over 250 meters.

Salt domes could contain several hundred cubic kilometers of water-equivalent mass.

Abstract

We have investigated the possibility that large rock salt formations might be suitable as target masses for detection of neutrinos of energies about 10 PeV and above. In neutrino interactions at these energies, the secondary electromagnetic cascade produces a coherent radio pulse well above ambient thermal noise via the Askaryan effect. We describe measurements of radio-frequency attenuation lengths and ambient thermal noise in two salt formations. Measurements in the Waste Isolation Pilot Plant (WIPP), located in an evaporite salt bed in Carlsbad, NM yielded short attenuation lengths, 3-7 m over 150-300 MHz. However, measurements at United Salt's Hockley mine, located in a salt dome near Houston, Texas yielded attenuation lengths in excess of 250 m at similar frequencies. We have also analyzed early ground-penetrating radar data at Hockley mine and have found additional evidence for attenuation lengths in excess of several hundred meters at 440 MHz. We conclude that salt domes, which may individually contain several hundred cubic kilometer water-equivalent mass, provide attractive sites for next-generation high-energy neutrino detectors.