Feb 3, 2005 Searching for a Suitable Salt Structure for SalSa by Allen Odian SLAC

Feb 3, 2005 Requirements Large Volume (Many tens of cubic kilometers) Long Microwave Attenuation Length (Hundreds of meters for frequencies between 100 MHz and a few GHz)

Feb 3, 2005 Types of Large Volume Salt Deposits Evaporites (Ancient sea beds) DOE Site WIPP in New Mexico 600 meter thick Low Level Radioactive Waste Disposal Salt Domes (Geologically Processed Evaporite) United Salt Co’s Hockley Mine in Texas Both are ~ 300 meters below ground surface

Feb 3, 2005 Cerenkov Radiation, Coherent and Incoherent Spectrum, dN/d ~ (Ze) 2   Incoherent, e - s and e + s, N total ~ Energy (E) Ne - /Ne + ~ 1.2, Charge excess, N excess ~ 0.1 N t Coherence length ~ bunch size (few cms) dN/d ~ E 2 for  > bunch size

Feb 3, 2005 Cerenkov Spectrum for ev Shower Wavelength (cm) dN/dlambda (relative units)

Feb 3, 2005 Salt Properties for Microwaves Density  = 2.2 gm/cm 3, X 0 = 24 gm/cm 2 Dielectric Constant  = 6, tan  < Ratio Im  /Re  = tan  Att length L att : L att / = 1/  tan  L att = f( ), = 0 /sqrt  For 1 GHz 0 = 0.3 m, = 0.12 m For tan  = 10 -4, L att = 400 m

Feb 3, 2005 Maximizing the Signal Power P is radiated for about a nanosecond P ~ E 2 ~ E 2 ~ 1/R 2 : E ~ 1/R ~ Voltage on Antenna V ~ E x Antenna Design (frequency) Cerenkov Radiation lobes are linearly polarized (Antennas need to preserve this) Energy Threshold set by R, Noise, and Antenna

Feb 3, 2005 View of WIPP WIPP Machine Shop

Feb 3, 2005 Test of WIPP Site Ceiling of salt tunnel had two sets of three 10 cm diameter holes, depth 6.7 meters, 22.9 meters apart Transmitter at end hole, ratio of signal at two separations gives attenuation length Study L att ~ f(Frequency and Depth) Results show presence of water n = 2.8 not 2.45

Feb 3, 2005 L att vs Frequency at WIPP

Feb 3, 2005 WIPP as a Salsa Site Wipp is not suitable for a SalSa site!

Feb 3, 2005 How to Make a Salt Dome Start with Evaporite Bury it deep by Geologic Movement When it becomes plastic, expel impurities Rise toward surface from density difference Shape like a high altitude Helium balloon

Feb 3, 2005 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 km 3 water equiv. in top 3-5 km for many domes Houston New Orleans Hockley dome/mine

Feb 3, 2005 Hockley Salt Dome Active Salt Mine, United Salt Company About 3 by 4 Km in horizontal, many Km deep No Boreholes, but Tunnels and Chambers Complications from Matching Antennas to Salt Change in beam pattern Measure many distances

Feb 3, 2005 Layout of Hockley Mine

Feb 3, 2005 Measurements Compare Friis formula with experimental results Ratio of 150 and 300 MHz results 750 MHz measurement Polarization and Noise Ground penetrating radar data

Feb 3, 2005 Measurement of Signal vs Distance Friis Formula (no attenuation) V R /V T = A/(R x , A = effective area of transmitting and receiving antennae At 150 MHz (half wave), A = At 300 MHz (full wave), A =

Feb 3, 2005 L att vs Distance at Two Frequencies

Feb 3, 2005 Frequency Dependence For constant tan  L att (300MHz)/L att (150MHz) = 0.5 Results for L att from frequency dependence

Feb 3, 2005 Latt from Frequency Dependence

Feb 3, MHz Measurement Four commercial UHF phased bowtie array Narrow beam made measurements difficult Results

Feb 3, 2005 Latt from Frequency of 750 MHz

Feb 3, 2005 Polarization and Noise At 150 MHz, test salt for birefringence No cross polarization observed within the rejection of antenna Observed noise characterized by a <600 K blackbody (not inconsistant with 310K blackbody)

Feb 3, 2005 Ground Penetrating Radar Masters thesis at Texas A&M GPR at 440 MHz, n = Results

Feb 3, 2005 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.

Feb 3, 2005 Dielectric resonator Combined Measurements M.Chiba

Feb 3, 2005 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 cubic km per salt dome –Several hundred known known salt domes in Gulf coast area, probably thousands throughout the world

Feb 3, 2005 Conclusions At least one salt dome may be suitable for SalSa A search for a candidate SalSa dome should start Preliminary tests should be made to test properties of dome

Feb 3, 2005 Backup Slides

Feb 3, 2005 Properties of materials for UHE Neutrino Detector Material Properties Air (STP) Ice (H 2 O) Rock salt (NaCl) Lime stone (CaCO 3 ) Density ρ (g/cm 3 ) Radiation length X 0 (cm) Refractive index n = Cherenkov angle (deg) Cherenkov threshold energy(keV) … Rock salt: high density, large refractive index and short radiation length From M. Chiba

Feb 3, 2005 Salt Measurements at WIPP & Hockley

Feb 3, 2005 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: 23x10x155mm 3 1GHz TM010 Q=10000 Size: 230mm  x 30mm

Feb 3, 2005

Latt from 440 MHz Radar