Ice Ray an Ice CubeCentered Radio GZK Array
Ice. Ray: an Ice. Cube-Centered Radio GZK Array John Kelley University of Wisconsin, Madison for the Ice. Ray collaboration ARENA 08, Rome
Goals • Extend Ice. Cube into the Ee. V 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
The Ice. Ray Collaboration Hawai’i: P. Allison, M. Du. Vernois, 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 50 m 200 m
Ray Tracing, cont. 400 m 1 km
Drilling • Deeper is better for Veff (up to ~400 m) • Ice. Cube EHWD: too cumbersome (and expensive) • Independent firn drill: easily drill to 50 -80 m, possibly deeper with modifications • Realistic goal: 200 m
50 km 2 Baseline Studies Higher density, shallow (50 m) vs. sparse, deep (200 m)
Simulation Results Ice. Ray-36 / 50 m depth Ice. Ray-18 / 200 m depth UH Ice. Ray 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 Ice. Ray-36 / shallow • Triggering both Ice. Ray and Ice. Cube: rates are low, but extremely valuable for calibration • High-energy extension (Ice. Cube+ above) with 1. 5 km ring helps a lot • Sub-threshold crosstriggering can also help
ANITA Experience MCM SP…SP MCM 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 • 12+2 antennas – – – • • • 6 Vpol 6 Hpol Discones for Vpol Batwings for Hpol 5 m circle 2. 5 m depth below screen Stacked in pairs for vertical resolution 15 m Cu mesh ground screen DAQ & receivers in shielded boxes ~1. 5 m depth just above screen Also: – 1 monitor antenna above screen, but ~1 m deep – Pulser bicone ~15 m away, in 24” augered hole, 2. 5 -3 m deep courtesy of C. Miki, Univ. of Hawai’i
courtesy of C. Miki, Univ. of Hawai’
Antenna Assembly discone batwing C. Miki with antenna pair
Receivers & DAQ system • RF receivers: – ANITA design, ~76 d. B gain, 140 K noise temperature – Bandpass 115 -1200 MHz • Ice. Cube radio readout (ICRR): – Based on LABRADOR digitizer + Virtex-4 FPGA combination – Similar to ANITA design, 16 chan, 8@1 Gs/s, 8@2 Gs/s – Interfaces to std. Ice. Cube DOM readout + leverage AURA DAQ courtesy of G. Varner
Terminated Amplifier Module
Ice. Ray Brains
DOM MB, TRACR, and ICRR
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
Summary • AURA (see talk by H. Landsman): leverage deep Ice. Cube holes • Surface testbed: detailed background characterization • Ice. Ray: greatly extend Ice. Cube+AURA; GZK neutrino measurement with optical crosscalibration
Extra Slides
Discones • Checked with nec 2 dx_firn – Code modified for n=1. 35 • 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 2 ndary mode
Simulation Details – Throw events over 6 km radius disk, 300 m to 2500 m depth – 60 -300 MHz bandwidth for each antenna, low gain (dipolelike response) – 12 antennas (6 Hpol, 6 Vpol) per station – > 4 s on 5 antennas required to trigger (to ensure near 100% reconstruction efficiency), use Tsys ~ 360 K (230 K ice +130 K receiver) – Exclude shallow zenith angles due to firn refraction shadowing
Cu mesh Ground screen • Ground screen goals: – suppress surface noise from Pole – block aircraft RFI – block galactic & solar RF emission (strong at 100 MHz) • Incident RFI from pole Refracts into surface better angle n=1. 35 f =48 o ~1/4 wave radius Suppress Fresnel diffraction • Size: ~ 3 times antenna array diam, ~15 m High-quality EMI mesh is really needed for best performance
Surface Cable • 1700 m Ericsson shielded 3 -quad connects to spare quads at SJB • Adaptor for direct DOM hookup (comms testing / debugging) also complete
- Slides: 28