Calibration and Physics with ARA Station 1: A Unique Askaryan Radio Array Detector

TL;DR

This paper details the calibration procedures and initial performance of the ARA Station 1, a pioneering ultra-high energy neutrino detector using Antarctic ice, focusing on timing, calibration, and antenna positioning to enhance neutrino detection capabilities.

Contribution

It introduces calibration methods for the ARA Station 1's electronics and antennas, improving timing precision and understanding of channel performance, aiding future neutrino detection and array design.

Findings

Achieved sub-nanosecond timing calibration precision.

Identified underperformance of HPol channels relative to VPol.

Calibrated antenna locations for improved vertex reconstruction.

Abstract

The Askaryan Radio Array Station 1 (A1), the first among five autonomous stations deployed for the ARA experiment at the South Pole, is a unique ultra-high energy neutrino (UHEN) detector based on the Askaryan effect that uses Antarctic ice as the detector medium. Its 16 radio antennas (distributed across 4 strings, each with 2 Vertically Polarized (VPol), 2 Horizontally Polarized (HPol) receivers), and 2 strings of transmitting antennas (calibration pulsers, CPs), each with 1 VPol and 1 HPol channel, are deployed at depths less than 100 m within the shallow firn zone of the 2.8 km thick South Pole (SP) ice. We apply different methods to calibrate its Ice Ray Sampler second generation (IRS2) chip for timing offset and ADC-to-Voltage conversion factors using a known continuous wave input signal to the digitizer, and achieve a precision of sub-nanoseconds. We achieve better calibration for odd, compared to even samples, and also find that the HPols under-perform relative to the VPol channels. Our timing calibrated data is subsequently used to calibrate the ADC-to-Voltage conversion as well as precise antenna locations, as a precursor to vertex reconstruction. The calibrated data will then be analyzed for UHEN signals in the final step of data compression. The ability of A1 to scan the firn region of SP ice sheet will contribute greatly towards a 5-station analysis and will inform the design of the planned IceCube Gen-2 radio array.