A calibration study of local ice and optical sensor properties in IceCube

TL;DR

This study models the optical properties of ice and sensors in IceCube, addressing how bubbly ice and sensor orientation affect calibration and photon detection accuracy.

Contribution

It provides a detailed modeling of hole ice optical properties and sensor positioning, improving calibration accuracy in IceCube.

Findings

Bubbly ice significantly distorts calibration light profiles.

Sensor tilt and cable shadowing impact photon detection.

Modeling helps correct for optical distortions in IceCube.

Abstract

The optical sensors of the IceCube Neutrino Observatory are attached on vertical strings of cables. They were frozen into the ice in the deployment holes made by hot water drill. This hole ice, to the best of our knowledge, consists of a bubbly central column, with the remainder of the re-frozen volume being optically clear. The bubbly ice often blocks one or several of the calibration LEDs in every optical sensor and significantly distorts the angular profile of the calibration light pulses. It also affects the sensors' response to in-coming photons at different locations and directions. We present our modeling of the hole ice optical properties as well as optical sensor location and orientation within the hole ice. The shadowing effects of cable string and possible optical sensor tilt away from the nominal vertical alignment are also discussed.