Transcript document

IceRay:
an IceCube-Centered Radio GZK
Array
John Kelley
University of Wisconsin, Madison
for the IceRay collaboration
ARENA08, Rome
Goals
• Extend IceCube into the EeV range via a radio array
(detecting Askaryan emission)
– 50 km2 (initial phase) to 300-1000 km2 (final target)
– substantial rates of GZK  / year
• O(1º) angular resolution
• Subset of events which trigger both radio and optical
arrays
– Allows calorimetry of both shower and outgoing lepton
– Invaluable for cross-calibration / unambiguous GZK
identification
The IceRay Collaboration
Hawai’i: P. Allison, M. DuVernois, P. Gorham,
J. Learned, C. Miki, B. Morse, L.
Ruckman, and G. Varner
Wisconsin: A. Karle, F. Halzen, and H.
Landsman
Ohio State: J. Beatty
Maryland: K. Hoffman
Delaware: D. Seckel
Penn State: D. Cowen and D. Williams
MIT: I. Kravchenko
Taiwan: P. Chen
UCL: R. Nichol and A. Connolly
Design: Frequency Range
• Attenuation length of
ice is better at low
frequency (< 500 MHz)
• Solid angle also better
at low freq.
• SNR goes as
sqrt(bandwidth)
• Go low freq., high
bandwidth: 60-300
MHz
Design: Depth
Firn shadowing: shallow rays can’t get to
surface!
I. Kravchenko et al., Astropart.Phys. 20 195-213 (200
Ray Tracing
50m
200m
Ray Tracing, cont.
400m
1km
Drilling
• Deeper is better for Veff (up to
~400m)
• IceCube EHWD: too cumbersome
(and expensive)
• Independent firn drill: easily drill to
50-80m, possibly deeper with
modifications
• Realistic goal: 200m
50 km2 Baseline Studies
Higher density, shallow (50m) vs. sparse, deep (200m)
Simulation Results
IceRay-36 / 50m depth
IceRay-18 / 200m depth
UH IceRay MC; crosschecked with Bartol, RICE MC, and ARIANNA MC
Acceptance and Event Rates
Initial phase achieves 3-9 ev/year
for “standard” fluxes
Final phase: ~100 ev/year
“Golden” Hybrid Events
IceRay-36 / shallow
• Triggering both IceRay
and IceCube: rates are
low, but extremely
valuable for calibration
• High-energy extension
(IceCube+ above) with
1.5km ring helps a lot
• Sub-threshold crosstriggering can also help
ANITA Experience
MCM SP…SP
MCM SP..SP..SP
MCM SP ….SP…..SP
• South Pole isn’t so radio-quiet
– strong impulsive sources (-like)
– 400-500 MHz range noisy (where
you want to be for ice)
– understanding / eliminating
background is key for large-scale
courtesy of P. Gorham
Surface Testbed
Station
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12+2 antennas
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6 Vpol 6 Hpol
Discones for Vpol
Batwings for Hpol
5m circle
2.5m depth below screen
Stacked in pairs for vertical
resolution
15m Cu mesh ground screen
DAQ & receivers in shielded
boxes ~1.5m depth just above
screen
Also:
– 1 monitor antenna above
screen, but ~1m deep
– Pulser bicone ~15m away, in
24” augered hole, 2.5-3m
deep
courtesy of C. Miki, Univ. of Hawai’i
courtesy of C. Miki, Univ. of Hawai’i
Antenna Assembly
discone
batwing
C. Miki with antenna pair
Receivers & DAQ system
• RF receivers:
– ANITA design, ~76 dB
gain, 140K noise
temperature
– Bandpass 115-1200
MHz
• IceCube radio readout
(ICRR):
– Based on LABRADOR
digitizer + Virtex-4
FPGA combination
– Similar to ANITA
design, 16 chan,
8@1Gs/s, 8@2Gs/s
– Interfaces to std.
IceCube DOM readout
+ leverage AURA DAQ
courtesy of G. Varner
Terminated Amplifier Module
IceRay Brains
DOM MB, TRACR, and ICRR
Test Setup — UH Manoa
10/24/07
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Nearly end-to-end test
DAQ and waveform analysis
Cold test with dry ice also
successful
Hardware is ready for
deployment
Summary
• AURA (see talk by H.
Landsman): leverage deep
IceCube holes
• Surface testbed: detailed
background characterization
• IceRay: greatly extend
IceCube+AURA; GZK neutrino
measurement with optical crosscalibration
Extra Slides
Discones
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Checked with
nec2dx_firn
– Code modified for
n=1.35
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Reasonable mode
structure, 100-600 MHz
100 MHz
200 MHz
300 MHz
400 MHz
600 MHz
Batwing (Horizontal Pol.)
375 MHz
100 MHz
150 MHz
175 MHz
225 MHz
Primary mode
2ndary mode
Simulation Details
– Throw events over 6 km radius disk, 300m to 2500m depth
– 60-300 MHz bandwidth for each antenna, low gain (dipolelike response)
– 12 antennas (6 Hpol, 6 Vpol) per station
– > 4s on 5 antennas required to trigger (to ensure near
100% reconstruction efficiency), use Tsys ~ 360K (230K ice
+130K receiver)
– Exclude shallow zenith angles due to firn refraction
shadowing
Cu mesh Ground screen
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Ground screen goals:
– suppress surface noise
from Pole
– block aircraft RFI
– block galactic & solar RF
emission (strong at
100MHz)
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Incident RFI from pole
Refracts into surface  better angle
n=1.35
f =48o
~1/4 wave radius
Suppress Fresnel diffraction
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Size: ~ 3 times antenna
array diam,  ~15m
High-quality EMI mesh is
really needed for best
performance
Surface Cable
• 1700m Ericsson shielded 3-quad
connects to spare quads at SJB
• Adaptor for direct DOM hookup
(comms testing / debugging) also
complete