Hagar Landsman, Mike Richman, and Kara Hoffman On behalf of the IceCube Collaboration Ice index of refraction n(z) Ice Attenuation Length (point to point) Environmental noise Reconstruction algorithms

2 IceCube’s radio extension  In ice digitization. Combination of ANITA/IceCube/RICE technologies: 2 clusters in clusters in Depth of 1450 m or 300 m AKA “AURA”  Envelope detection. 6 units deployed at -35, -5 meters ( ) 6 units in other depth/location (On top of a building, terminated, -250m) AKA “SATRA”  Calibration Set of transmitters and passive antennas for calibration (including cable symmetrical antennas)

IceCube-radio hardware Fully digitized WFs Use IceCube’s resources: holes, comm. and power Each Cluster contains:  Digital Radio Module (DRM) – Electronics  4 Antennas – With front end electronics  1 Array Calibration Unit (ACU) - Transmitter Deployed above the IceCube array:  “Free” Deep holes  “Free” Power distribution and communication Signal conditioning and amplification happen at the front end  RICE Broad band fat dipole antennas centered at 400 MHz  450 MHz Notch filter  200 MHz High pass filter (2 units with 100Mhz)  ~50dB amplifiers (+~20 dB in DRM) Signal is digitized and triggers formed in DRM (a’la’ANITA)  512 samples per 256 ns (2 GSPS).  Wide frequency range and multiple antennas are required for triggering surface junction box Counting house

4 Source at surface: Source In Ice: Deep KU pulser to DorisSurface pulser to Danielle 256 ns

5 Transient detection Transient detector (“SATRA”) * 6 in ice units on 3 strings in holes #8, #9 and #16 * 1 antenna each: 2 antennas per hole. * 35m and 5 m deep * Each pair of antennas has a local-coincidence triggering * Dry holes * Log amp envelope detection DAQ box sjb 30 m 5 m satra IceCube cable Nick name: SATRA - (Sensor Array for Transient Radio Astrophysics )

Wind generated noise * The South Pole is electrically insulated, causing a buildup of electrostatic charge, leading to EMI from discharge. * Elevated noise corresponds to wind speed great than ~20 knots. * New model: Gordon, Taylor (2008) : E>25 KV/m near surface

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8 * NOAA Sonde (National Oceanic and Atmospheric Administration) * Model RS80-15 * MHz signal * Fridays only * Plastic baloon (rises slower) * MET Sonde * Model RS92-SGP * MHz * Daily * rubber balloons

Source at -250m Bottom antenna -35m Top antenna -5m Depth [m] XY separation [m] surface Direct rays Reflected rays Measured time differences: Time differences between direct rays And between direct and reflected rays can be calculated

10 Hole 16, Bottom Hole 16, Top Hole 9, Top Hole 8, Top Hole 9, Bottom Hole 8, Bottom ~44 bins = ~139 ns Simulated results=137 ns Simulated results=14 ns

11 n_c n_shallow Simulated absolute travel time from pulser to top antenna, hole 8 no solution 2950 ns 2650 ns Improved Ray trace simulation (Chris Weaver) n(z) = n_d + (n_s - n_d)*e n_c*z Values for n_d and n_s from RICE data down to 150m and ice cores down to 240m. Simulated time diff between Direct & secondary ray For Bottom ant hole 16 n_c n_shallow 180 ns 140 ns 90 ns 30 ns 50 ns n_c n_shallow Simulated Time differences between direct hits in hole 9 bottom and top This is why this channel did not see the pulser. It is in the invisible region due to ray tracing

Based on set of hit time differences between antennas and between primary and secondary hits on the same antenna, a limit on the index of refraction model n(z) = n_d + (n_s - n_d)*e n_c*z can be obtained. Systematics taken into account: n_deep, Geometry, timing resolution, WF features

Final best fit attenuation length profile for different pairs of antennas. Systematics currently being evaluted.

IceCube provided unique infrastructure and opportunity to study the RF properties of South Polar ice, develop RF hardware for an Askaryan array, and study the suitability of the RF noise environment for an englacial array. Favorable ice properties and noise environment have been found. An array concept has been proposed, and a new collaboration, independent of IceCube has been formed. The first phase is funded (see talks by Amy Connolly and Kara Hoffman). SummarySummary