saltdome shower array: a gzk neutrino detector for high energy physics & particle astrophysics
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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. What is needed for a GZK n detector?. - PowerPoint PPT PresentationTRANSCRIPT
SalSA presentation, DOE HQ 1
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
SalSA presentation, DOE HQ 2
What is needed for a GZK detector?
Standard model EeV GZK flux: <1 per km2 per day over 2 srInteraction 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 km3 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 pulsesNeutrinos 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
SalSA presentation, DOE HQ 3
Saltdome Shower Array (SalSA) concept
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Depth (km)
Halite (rock salt)• L(<1GHz) > 500 m w.e.• Depth to >10km• Diameter: 3-8 km• Veff ~ 50-350 km3 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 km3 water equivalent in top ~3.5km =>300-600 km3 sr w.e.
SalSA presentation, DOE HQ 4
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 OrleansHockley salt Dome & mine
SalSA presentation, DOE HQ 5
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
SalSA presentation, DOE HQ 6
Examples of Gulf coast halite purity
Salt dome Sample depth, ft halite % anhydrite %
Splindletop, TX 2676 94.83 5.17
Sour Lake, TX 7290 92.48 7.52
Saratoga, TX -- 96.79 3.21
McFaddin, TX 2645 98.47 1.53
Hull, TX 706 92.15 7.85
Moss Bluff 4566 96.02 3.98
High Island, LA 3359 89.63 10.37
Grand Saline, TX Various, mine hor. 98.0 2.0
Hockley, TX 1200, estimated avg. 95.0 5.0
Avery Island, LA Mine horizon 98.73 1.2
Cypress Creek, MS
1720-1876, 8 samples 95.61 3.97
Richton, MS 1120-1270, 8 samples
94.08 5.41
Port Barre, LA -- 99 1
SalSA presentation, DOE HQ 7
Halite & anhydrite
Pure NaCl crystals are theoretically lossless to RF via absorptionCrystal 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
SalSA presentation, DOE HQ 8
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
SalSA presentation, DOE HQ 9
In situ salt dome measurements of attenuation
Location Freq., MHz
Loss coefficient Attenuation length
Method reference
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 >300m GPR, 1245m path, derived
Stewart & Unterberger 1976
Hockley dome, TX 440 <0.005 per m >200m GPR, derived from reflections, 350m 1-way
Hluchanek 1973
“saltdome in N. Germany”
22.5 0.0027 per m ~370m Dual borehole, 470m separation
Nickel et al. 1983
Hockley dome, TX 150300750
<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
SalSA presentation, DOE HQ 10
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
SalSA presentation, DOE HQ 11
Salt Dome Selection & Phase I Prototype
Inputs: Surveys in 1970’s, 1980’s for Nuclear Waste Repository sitesStringent 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 reportsKeechi 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 qualityChoose 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
SalSA presentation, DOE HQ 12
Current Salt Dome candidate ranking
Rank DomeUS
State
Volume to 3.5km depth
[cubic km salt]
Maximum aperture [cubic km steradians
water equiv.] (a)
Positive Notes Negative Notes
1 Richton MS 50.0 684.4 220 360
Shallow, extensively mapped, no oil or gas production. Salt core analysis shows 94% halite 5%
anhydrite. Good drainage, flat cap region. Huge body of ONWI survey
literature. Industrial forestry on most of cap.
Numerous dropped projects. Plans for LPG storage caverns could revive?
2 Vacherie LA 45.4 621.7 240 300
3500' core taken by DOE, salt analysis done; very low water
content in salt; shallow cap. Large body of ONWI survey literature
some potential for flooding on dome crest?
3 Keechi TX 32.7 447.3 90 900No oil or gas, good drainage
around dome, good access. Near Palestine, TX
Little survey work. Sloping cap; requires >1000m bores on flank
4 Hainesville TX 39.2 536.5 366 400Well mapped; circular, flat cap, very large, sparsely populated
Extensive oil/gas production (53 wells); Several LPG storage caverns.
5 Chacahoula LA 38.7 529.8 370 1000No oil directly on cap (in 1961),
sparse population expected.
Extensive oil/gas prod, S flank densely producing. In "Bubbling Bayou."
Sloping cap, requires 1000m bores on flank. Probable LPG storage caverns
6 Butler TX 21.1 289.3 10 450Shallow cap. Near Palesine, TX.
Good access roads. Minimal oil or gas production.
Sandstone quarry on flank. Two or more gas storage caverns in 1984.
Potential for flooding.
7 Cypress Creek MS 15.0 205.8 396 400Extensively mapped by DOE. Flat cap. DOE salt core analysis gives
94% halite 6% anhydrite.
Oil & gas wells on S and W flanks. Some potential for flooding on cap
region.
NOTES:(a) Assumes 2 pi steradians solid angle acceptance for all of volume (consistent with simulations), density of 2.18 g/cc for salt.(b) Minimum depth is shallowest salt from surface; average is over all of crest needed to instrument the dome for a SalSA.
Salt crest mininmum (left) and average
(right) depths [m] (b)
SalSA presentation, DOE HQ 13
Richton Dome
Richton Dome has excellent seismic, gravity & sulfur exploration (unsuccessful) measurements of salt body
SalSA presentation, DOE HQ 14
Richton Dome area
Land use primarily industrial forest
Plum Creek Land Mgmt contacted, lease option negotations ongoing
SalSA presentation, DOE HQ 15
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 wellTypical $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
SalSA presentation, DOE HQ 16
Drilling salt domes
Shallow holes: a modest rig possible, 20-40’ truck-mounted; water-well driller capableDeep 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 saltSalt is hermetic and needs no casing or liner, is easily drilled
Requires oil-based drilling fluids to avoid brine formationBorehole remains OPEN after drilling, probably for decades at a 4” bore, and is backfilled with fluid providing hydrostatic pressure headErgo: Strings will be repairable, recoverable, can be upgraded!
SalSA presentation, DOE HQ 17
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 yearLease costs expected to be of order $20K per yr for 3 yearsNegotiations for lease options in progress
SalSA presentation, DOE HQ 18
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 sensitivity12 nodes of 12 antennas each is current choice$100-$150K estimated per string cost with no new technologypressure-compensated controller system to be demonstrated
SalSA presentation, DOE HQ 19
Fat dipole results in salt
4” diameter by 30 inch length, copperUsable 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 ohmfeedpointcoupling
SalSA presentation, DOE HQ 20
Basic string architecture
String12 nodes
Node = 12 antennas and center housing
tape
Stainless tube
armor
Insulatedconductors
Fibers
NEMA 3R 38" x 21" x17"
SalSA presentation, DOE HQ 21
GEISER (Giga-bit Ethernet Instrumentation for SalSA Electronics
Readout)
GEISER PhilosophySet low thresholdFill Gb/s ethernet linkEvent build at surfacePure digital transmission
Trigger/Event buildingNo custom, fast triggerExploit telecomm Event building on PC farm
SalSA presentation, DOE HQ 22
GEISER Data flow
GEISER approach:Digitize the “mud” in downholePan for gold at the surface
Digital Cell system for data
collection
Internal FPGA Buffer RAM
100ms latency/hit>99.999999…% livetime @ 1.5kHz
RF inContinuous 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
)
SalSA presentation, DOE HQ 23
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
SalSA presentation, DOE HQ 24
Readout board
Trigger, bi-directional fiber-link
D’RITOS
LNA, 2nd-stage amps
LNA, 2nd-stage amps
RF conns
HV-lvDC regulation on separate board
SalSA presentation, DOE HQ 25
Radio Cherenkov testbed system
Goal: to detect first coherent radio Cherenkov emission signals of natural origin, from muon-bremsstrahlung showersStandard hodoscope tagging combined with antenna arraySalSA instrument development: up to 196 antenna channels!
Salt, 25 tons
Antenna layerShown exposed
Liquid Scintillation counters (MACRO)
SalSA presentation, DOE HQ 26
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. CounterBackgrounds taken from out-of-cone and out-of-time dataWe see strong enhancement due to ensemble of ~200 GeV muon bremsstrahlung showers
SalSA presentation, DOE HQ 27
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 yearsCapable 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
SalSA presentation, DOE HQ 28
Neutrino Flavor/Current ID
Charged/neutral current & flavor ID possible on subset of SalSA eventsAt least 20% of GZK CC events will get first order flavor IDFor 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
1018 eV