1. SalSA presentation, DOE HQ1 Saltdome Shower Array: A GZK neutrino Detector For High Energy Physics & Particle Astrophysics Part II: Salt Domes & Detector Details Peter Gorham With help from Gary Varner University of Hawaii at Manoa

2. SalSA presentation, DOE HQ2 What is needed for a GZK detector? Standard model EeV GZK flux: <1 per km 2 per day over 2  sr Interaction probability per km of water = 0.2% Derived rate of order 0.5 event per year per cubic km of water or ice  A teraton (1000 km 3 sr) target is desirable! Problem: how to scale up from current water Cherenkov detectors? One solution: exploit the Askaryan effect: coherent radio Cherenkov emission Particle showers in solid dielectric media yield strong, coherent radio pulses Neutrinos can shower in many radio-clear media: air, ice, rock-salt, etc. Economy of scale for a radio detector (antenna array + receivers) is very competitive for giant detectors

3. SalSA presentation, DOE HQ3 Saltdome Shower Array (SalSA) concept 1 2 3 4 5 6 7 Depth (km) Halite (rock salt) L  ( 500 m w.e. Depth to >10km Diameter: 3-8 km V eff ~ 50-350 km 3 w.e. No known background >2  steradians possible Antenna array Qeshm Island, Hormuz strait, Iran, 7km diameter Isacksen salt dome, Ellef Ringnes Island, Canada 8 by 5km Salt domes: found throughout the world Rock salt can have extremely low RF loss, as radio-clear as Antarctic ice ~2.4 times as dense as ice typical: 50-100 km 3 water equivalent in top ~3.5km =>300-600 km 3 sr w.e.

4. SalSA presentation, DOE HQ4 U.S Gulf coast salt domes Salt origin: Shallow Jurassic period sea, 200-150M yrs old, inshore Gulf coast area dried ~150 Myrs ago Formed fairly uniform evaporite beds ~1 km thick or more, known as ‘Louann’ salt: 94-98% halite (NaCl) 2-6% anhydrite (Calcium sulfate) Trace Mg, Sr, dissolved gases, 10- 40 ppm trapped brine Salt density (2.2) < rock (2.6) plasticity at 10-15km depth leads to ‘diapirism’ : formation of buoyant extrusions toward surface Diapirism for Louann salt ceased 50-100 Myrs ago, left stable salt diapirs all over the Gulf coast Houston New Orleans Hockley salt Dome & mine

5. SalSA presentation, DOE HQ5 Gulf coast salt domes 1.5 - 8 km sectional axes, circular to highly elliptical vertical extent from near surface to 10 km depths common Source of oil & gas trapped on flanks: impermeability of salt compared to sediments

6. SalSA presentation, DOE HQ6 Examples of Gulf coast halite purity Salt domeSample depth, fthalite %anhydrite % Splindletop, TX267694.835.17 Sour Lake, TX729092.487.52 Saratoga, TX--96.793.21 McFaddin, TX264598.471.53 Hull, TX70692.157.85 Moss Bluff456696.023.98 High Island, LA335989.6310.37 Grand Saline, TXVarious, mine hor.98.02.0 Hockley, TX1200, estimated avg.95.05.0 Avery Island, LAMine horizon98.731.2 Cypress Creek, MS1720-1876, 8 samples95.613.97 Richton, MS1120-1270, 8 samples94.085.41 Port Barre, LA--991

7. SalSA presentation, DOE HQ7 Halite & anhydrite Pure NaCl crystals are theoretically lossless to RF via absorption Crystal lattice defects are only mechanism for loss Rayleigh & Mie scattering lead to attenuation over 100’s of m Measured in situ bulk attenuation lengths can be several hundred m or more in many salt domes, but not all (Weeks Island--water intrusion) Chief impurity: anhydrite (anhydrous gypsum or alabaster) Also known to have ultra-low loss at radio frequencies Expectations: typical Louann salt will have at least several hundred meter attenuation length if water content is low (<300 ppm) Core samples indicate low water content in 80-90% of domes

8. SalSA presentation, DOE HQ8 Halite-anhydrite salt dome structure Morton Salt mine, Grand Saline Salt dome, TX ~98% pure halite, 2% anhydrite Anhydrite banding evident, nearly vertical from deformation of original salt beds Produces negligible effects on radio propagation

9. SalSA presentation, DOE HQ9 In situ salt dome measurements of attenuation LocationFreq., MHz Loss coefficientAttenuation length Methodreference Pine Prairie salt dome, LA 230<0.0042 per m (best) <0.0105 (typical) <0.016 (worst case) >235m >94m >66m GPR, from salt dome flank reflections, 150- 200m typical one way, very close to flank Holser et al. 1972 Cote blanche salt dome, LA 440<0.0033 per m>300mGPR, 1245m path, derived Stewart & Unterberger 1976 Hockley dome, TX440<0.005 per m>200mGPR, derived from reflections, 350m 1-way Hluchanek 1973 “saltdome in N. Germany” 22.50.0027 per m~370mDual borehole, 470m separation Nickel et al. 1983 Hockley dome, TX150 300 750 <0.0039 per m <0.0047 per m <0.0041 per m >256m >213m >243m Transmit & receive through salt column, 40m thick Gorham, Saltzberg et al. 2001

10. SalSA presentation, DOE HQ10 Borehole radar on dome flank Pine Prairie dome, LA northern extreme of Louisiana salt dome region Holser et al 1972 used dipole & helix antennas at 230MHz in a 5” diameter sonde to map the flank of the dome (1 microsec pulses) Most data within 150m of edge of dome (impurities increase close to flank) Flank location confirmed by retrieved samples when flank was intercepted Good data & SNR to 8000 foot depths, until flank was pierced

11. SalSA presentation, DOE HQ11 Salt Dome Selection & Phase I Prototype Inputs: Surveys in 1970’s, 1980’s for Nuclear Waste Repository sites Stringent requirements with similar needs to SalSA, large, stable dome with dry salt, no economic usage Richton (MS) and Vacherie (LA) domes both have excellent DOE salt core reports Keechi Dome in TX also appears to have no oil or gas interests Select 3-5 salt domes, drill 1500’ borehole with 300-500 ft of salt penetration, continuous core Use chemical & loss-tangent measurements on core, plus borehole radar to assess initial salt quality Choose best of initial domes that meet requirements for three or four deep (3km) boreholes, to install a prototype SalSA (‘Salsita’) 1-2 years’ operations to establish proof-of-concept, and discover or confirm small sample of GZK neutrino events, then propose full array

12. SalSA presentation, DOE HQ12 Current Salt Dome candidate ranking

13. SalSA presentation, DOE HQ13 Richton Dome Richton Dome has excellent seismic, gravity & sulfur exploration (unsuccessful) measurements of salt body

14. SalSA presentation, DOE HQ14 Richton Dome area Land use primarily industrial forest Plum Creek Land Mgmt contacted, lease option negotations ongoing

15. SalSA presentation, DOE HQ15 Mechanics of land use & drilling Land use & rights studies underway, will have agreements in place for initial phase as pre-requisite for proposal Mineral rights owner/leaseholders will retain asset rights if oil, gas, sulfur, etc. is discovered (unlikely but not excluded) Surface rights owners will receive “damages” for 1 acre drilling site, and lease agreements for duration of project Depends on land usage, rural land: $1-2K damages typical per well Typical $1-2K/yr lease for small well-head site (~100 sq. ft.) & right of way Will negotiate contracts for “options” on leases for proposal Baker-Hughes INTEQ has expressed interest in cost-sharing agreement for prototype phase Mississippi Office of Geology is supporting Richton dome SalSA studies

16. SalSA presentation, DOE HQ16 Drilling salt domes Shallow holes: a modest rig possible, 20-40’ truck- mounted; water-well driller capable Deep holes require large derricks, 130’ high typical, and a 1 acre site Bore is drilled through surface layers and “caprock” to about 1000’ depth into salt, and must be cased with steel liner above salt Salt is hermetic and needs no casing or liner, is easily drilled Requires oil-based drilling fluids to avoid brine formation Borehole remains OPEN after drilling, probably for decades at a 4” bore, and is backfilled with fluid providing hydrostatic pressure head Ergo: Strings will be repairable, recoverable, can be upgraded!

17. SalSA presentation, DOE HQ17 Drilling Salt Domes Drilling costs preliminary estimates $120-150K per 1500’ bore, $250-350K per 3.5 km deep hole 4 shallow & 3-4 deep holes: $1.2M-$2M including casing and cores Capital cost of dedicated drill rig ($0.8-1M) would be justified for full SalSA, but not at this stage rig can be sold at termination of drilling, capital re-invested in project (eg., Don Thomas at UH has done similar) Damage & lease costs: Damages of order $20K in initial year Lease costs expected to be of order $20K per yr for 3 years Negotiations for lease options in progress

18. SalSA presentation, DOE HQ18 String instrumentation: “node” configuration Antennas (copper cylinders) are cheap, “controller nodes” (receiver, digitizers, data transmitters, & pressure housing) costly, THUS: Use many (12) antennas per controller node to optimize sensitivity 12 nodes of 12 antennas each is current choice $100-$150K estimated per string cost with no new technology pressure-compensated controller system to be demonstrated

19. SalSA presentation, DOE HQ19 Fat dipole results in salt 4” diameter by 30 inch length, copper Usable from 50MHz to 1 GHz (better than model predicts) Single mode from 50-350MHz 120 MHz 370 MHz 180 MHz 530 MHz Frequency, Hz/MHz SWR (predicted) SWR (measured) Gain, dB 50 ohm feedpoint coupling

20. SalSA presentation, DOE HQ20 Basic string architecture String 12 nodes Node = 12 antennas and center housing tape Stainless tube armor Insulated conductors Fibers NEMA 3R 38" x 21" x17"

21. SalSA presentation, DOE HQ21 GEISER ( Giga-bit Ethernet Instrumentation for SalSA Electronics Readout) GEISER Philosophy Set low threshold Fill Gb/s ethernet link Event build at surface Pure digital transmission Trigger/Event building No custom, fast trigger Exploit telecomm Event building on PC farm

22. SalSA presentation, DOE HQ22 GEISER Data flow GEISER approach: Digitize the “mud” in downhole Pan for gold at the surface Digital Cell system for data collection Internal FPGA Buffer RAM 100ms latency/hit >99.999999…% livetime @ 1.5kHz RF in Continuous 64kb/event 1.6kHz (100baseT) 16kHz (GbitEthernet) Trigger packets sent via FM/local radio Node/String Time stamps Event request Data Transfer 4-deep analog buffering: Hold at 1.5kHz (>2.4  )

23. SalSA presentation, DOE HQ23 In hole digitization 3rd generation switched-capacitor array (SCA) architecture Digitizer n’ Readout, In-situ Transient Observation in Salt [D’RITOS] 4-deep analog buffering for each antenna channel Reference timing Channel 6 Massively parallel ADCs 50ms conversion 7x256 samples/event 50ms readout (40MHz) 100ms total latency

24. SalSA presentation, DOE HQ24 Readout board Trigger, bi-directional fiber-link D’RITOS LNA, 2 nd -stage amps RF conns HV-lvDC regulation on separate board

25. SalSA presentation, DOE HQ25 Radio Cherenkov testbed system Goal: to detect first coherent radio Cherenkov emission signals of natural origin, from muon-bremsstrahlung showers Standard hodoscope tagging combined with antenna array SalSA instrument development: up to 196 antenna channels! Salt, 25 tons Antenna layer Shown exposed Liquid Scintillation counters (MACRO)

26. SalSA presentation, DOE HQ26 First Observation of Cosmic-ray muon- generated Radio Cherenkov signals Average of ~10K events selected for showers, out of 230K (2mo. data) Signal antennas & time determined by track fit from scint. Counter Backgrounds taken from out-of-cone and out-of-time data We see strong enhancement due to ensemble of ~200 GeV muon bremsstrahlung showers

27. SalSA presentation, DOE HQ27 Summary The SalSA concept intellectual fruit of two OJI awards, Saltzberg & Gorham Strong HEP motivation to study & use GZK neutrinos We have gone about as far as we can without a prototype array Salsita will position us for a full-scale proposal within 2 years Capable of discovery and/or confirmation of GZK flux Pathfinder for full scale detector, built around the prototype We solicit your advice & guidance! OJI awards have mentored us both to this stage We offer SalSA as a next generation Energy Frontier HEP instrument

28. SalSA presentation, DOE HQ28 Neutrino Flavor/Current ID Charged/neutral current & flavor ID possible on subset of SalSA events At least 20% of GZK CC events will get first order flavor ID For non-SM high neutrino cross sections, NC events can interact twice Charged current (SM: 80%) Neutral current (SM: 20%) e 25% hadronic + 75% EM shower at primary vertex; LPM on EM shower Single hadronic shower at vertex  25% hadronic at primary, 2ndary lepton showers, mainly EM Single hadronic shower at vertex  25% hadronic at vertex, 2ndary lepton showers, mainly hadronic Single hadronic shower at vertex ~2 km 10 18 eV 