U.S Gulf coast salt domes

Salt dome demographics:

• Several hundred known—some are good source of oil

• Typical ~3-5 km diameters, 5-15 km deep

• ~200 km3 water equiv. in top 3-5 km for many domes

HoustonNew Orleans

Hockley dome/mine

Salt Measurements at WIPP & Hockley

• Supported through UCLA: DOE ADRP grant (Saltzberg)• Results posted at hep-ex, submitted to NIM:

– WIPP: not so good……. Hockley Mine: very promising!

Results from Hockley Mine rock salt tests

• All results consistent with >200 meter attenuation lengths• Supported by ground-penetrating radar results since early 1970’s

– Radar pulses sent through ~3 km of salt in some Gulf-coast salt domes

Summary of WIPP/Hockley results• Rock salt is perhaps the clearest medium known for EM propagation

– Usable frequency range from few MHz to ~10 GHz– Evaporite beds (WIPP) have problems with impurities, but salt domes

appear to be often purified through geologic processes

• No measureable bi-refringence or depolarization– Allows for possibility of polarization tracking– May be better than ice in this respect

• Several other salt domes known to be as good or better than Hockley– Avery Island (LA), Weeks Island (LA)– Cote Blanche (LA), Grand Saline (TX)– Many others expected to be excellent but as yet unmeasured– Typical salt volume 50-100 cubic km per salt dome– Several hundred known known salt domes in Gulf coast area, probably

thousands throughout the world

Properties of materials for UHE Neutrino Detector

MaterialProperties

Air(STP)

Ice(H2O)

Rock salt

(NaCl)

Lime stone

(CaCO3)

Density ρ (g/cm3) 0.0012 0.924 2.22 2.7

Radiation length X0 (cm) 30420 39 10.1 9.0

Refractive index n = 1.000293 1.78 2.43 2.9

Cherenkov　 angle (deg) 1.387 55.8 65.7 69.8

Cherenkov threshold energy(keV) …. 107 50 33

Rock salt: high density, large refractive index and short radiation length

From M. Chiba

Measurements of complex permittivity of rock salts and lime stones

Cavity perturbation method

Absorption depends on the surface condition of the samples, e.g. smoothness, stain etc.

9.4GHz TE107 Q=4000 Size: 23x10x155mm3

1GHz TM010Q=10000Size: 230mm x 30mm

Samples measured around 10GHz

•Rock salt is fragile, so that it is not easy to make small stick samples ( 1mm x 1mm x 10.2mm ). Lime stone (especially Jura lime stone ) is rigid. The small stick samples are obtained using a milling machine.

in situ measurementsP.Gorham et al

NaCl, Dielectric Materials and Applications (A. R. von Hippel ed.), 1954

tanδ=2×10-4

Rock salt Hockley mine, USA

Rock salt, Halstadt mine, Austria

NaCl synthesizedLime stone, Kamaishi, Japan

Lime stone, Mt. Jura, France Rock salt, Asse mine, Germany

Hippel 25GHz

1GHz cavity 5.5GHz

8.2GHz

11GHz

Nacl powder

Teflon

Dielectric resonator

tan

1

L

Attenuation length

M.Chiba