Considerations on an underground neutrino radio detector in salt

Abstract

This article presents the possibility of in-salt radio detection of high energy neutrinos, and shows the implications that a heterogeneous propagating medium has on both antenna behaviour, and on constructing the detector. Based on several factors (propagation effects signal to noise ratio, minimum necessary number of triggers, etc.) it was found that observations are limited at a 10 22 eV energy threshold. This higher limit allows both neutrino characteristics, and internal structure of the dome to be simultaneously determined. A total number of 40 to 200 events per year is expected when typical sedimentary layers of about 5cm are considered for the internal salt dome structure.

A Large Scale Characterization of the Dielectric Properties of Heterogeneous Layered Rock Salt

“…Propagation of radio waves in a heterogeneous medium is affected by several phenomena: reflections at the separation interfaces, absorption, and scattering on naturally occurring impurities within each layer. Among the three, the main energy loss is due to reflections [32]. Diapirs produce salt with a negligible brine content and minimal impurities, and thus birefringence is unlikely to occur [33].…”

“…The effect of brines in the form of fluid inclusions was already estimated in [32]. The brine-induced radio wave attenuation was calculated following [65], [66].…”

The Transfer Function of a Boreholed Dipole Antenna

“…This is one of the main reasons why the problem addressed in this paper is difficult to solve, as commercial analysis software for antenna and propagation description require as input of exactly the mentioned unknown quantities. Some recent work using detailed finite difference time domain models [18] presented simulations for lossy heterogeneous environments, but there the medium was continuous, which already excludes the main source of power losses, reflections at interfaces of separation [19].…”

“…Other propagation effects, such as scatterings on impurities, have been estimated elsewhere [19] and their overall effect on the attenuation of radio waves is very small compared to other effects (e.g., reflections at interfaces of separation between layers).…”

Results on radio attenuation length recorded in a Romanian salt mine

“…In the specific case of a km 3 neutrino detector in a salt mine neutrinos are observed indirectly by measuring the radio emission generated by their interaction with the salt. As waves propagate in a non ideal medium before being measured by radio antennas it is impetuous to have first a good geophysical material description for radio wave propagation.…”