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Published byGrant Powers Modified over 8 years ago
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IceRay: an IceCube-Centered Radio GZK Array John Kelley University of Wisconsin, Madison for the IceRay working group ARENA08, Rome
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Goals Extend IceCube into the EeV range via a radio array (detecting Askaryan emission) –50 km 2 (initial phase) to 300-1000 km 2 (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
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The IceRay Working Group 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
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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
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Design: Depth Firn shadowing: shallow rays can’t get to surface! I. Kravchenko et al., Astropart.Phys. 20 195-213 (2003)
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Ray Tracing 50m200m
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Ray Tracing, cont. 400m1km
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Drilling Deeper is better for V eff (up to ~400m) IceCube EHWD: too cumbersome (and expensive) Independent firn drill: easily drill to 50-80m, possibly deeper with modifications Realistic goal: 200m
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50 km 2 Baseline Studies Higher density, shallow (50m) vs. sparse, deep (200m)
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Simulation Results UH IceRay MC; crosschecked with Bartol, RICE MC, and ARIANNA MC IceRay-36 / 50m depth IceRay-18 / 200m depth
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Acceptance and Event Rates Initial phase achieves 3-9 ev/year for “standard” fluxes Final phase: ~100 ev/year
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“Golden” Hybrid Events 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 cross- triggering can also help IceRay-36 / shallow
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ANITA Experience 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 radio array MCM SP…SP MCM SP..SP..SP MCM SP ….SP…..SP courtesy of P. Gorham
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Surface Testbed Station 12+2 antennas –6 V pol 6 H pol –Discones for V pol –Batwings for H pol –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
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Antenna Assembly discone batwing C. Miki with antenna pair
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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
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Terminated Amplifier Module
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IceRay Brains
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DOM MB, TRACR, and ICRR
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Test Setup — UH Manoa 10/24/07 Nearly end-to-end test DAQ and waveform analysis Cold test with dry ice also successful Hardware is ready for deployment
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Summary / Outlook AURA (see talk by H. Landsman): leverage deep IceCube holes Surface testbed: detailed background characterization, hardware prototypes IceRay: greatly extend IceCube+AURA; GZK neutrino measurement with optical cross- calibration
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Extra Slides
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Discones Checked with nec2dx_firn –Code modified for n=1.35 Reasonable mode structure, 100-600 MHz 100 MHz 200 MHz 300 MHz400 MHz 600 MHz
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Batwing (Horizontal Pol.) 100 MHz175 MHz 375 MHz 150 MHz 225 MHz Primary mode2ndary mode
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Simulation Details –Throw events over 6 km radius disk, 300m to 2500m depth –60-300 MHz bandwidth for each antenna, low gain (dipole- like response) –12 antennas (6 H pol, 6 V pol ) per station –> 4 on 5 antennas required to trigger (to ensure near 100% reconstruction efficiency), use T sys ~ 360K (230K ice +130K receiver) –Exclude shallow zenith angles due to firn refraction shadowing
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Cu mesh Ground screen Ground screen goals: –suppress surface noise from Pole –block aircraft RFI –block galactic & solar RF emission (strong at 100MHz) Size: ~ 3 times antenna array diam, ~15m High-quality EMI mesh is really needed for best performance n=1.35 =48 o Incident RFI from pole Refracts into surface better angle ~1/4 wave radius Suppress Fresnel diffraction
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Surface Cable 1700m Ericsson shielded 3-quad connects to spare quads at SJB Adaptor for direct DOM hookup (comms testing / debugging) also complete
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