Design, performance, and analysis of a measurement of optical properties of antarctic ice below 400 nm

TL;DR

This paper reports on the measurement of UV light scattering and absorption in Antarctic ice using a novel calibration device, aiding the development of optical sensors for neutrino detection in IceCube upgrades.

Contribution

It introduces a new calibration device and provides measurements of UV optical properties of ice relevant for neutrino telescope sensor development.

Findings

Measured scattering and absorption lengths of UV light in Antarctic ice.

Validated Monte Carlo simulations with experimental data.

Demonstrated the performance of the calibration device.

Abstract

The IceCube Neutrino Observatory, located at the geographic South Pole, is the world's largest neutrino telescope, instrumenting 1 km$^3$ of Antarctic ice with 5160 photosensors to detect Cherenkov light. For the IceCube Upgrade, to be deployed during the 2022-23 polar field season, and the enlarged detector IceCube-Gen2 several new optical sensor designs are under development. One of these optical sensors, the Wavelength-shifting Optical Module (WOM), uses wavelength-shifting and light-guiding techniques to measure Cherenkov photons in the UV range from 250 nm to 380 nm. In order to understand the potential gains from this new technology, a measurement of the scattering and absorption lengths of UV light was performed in the SPICEcore borehole at the South Pole during the winter seasons of 2018/2019 and 2019/2020. For this purpose, a calibration device with a UV light source and a detector using the wavelength shifting technology was developed. We present the design of the developed calibration device, its performance during the measurement campaigns, and the comparison of data to a Monte Carlo simulation.