February 2021
Understanding the ice
“With the IceCube experiment at the South Pole, we use one cubic kilometer of glacial ice to capture signals from neutrinos that come from the depths of space. When one of these neutrinos hits an ice molecule, the resulting particles emit a special bluish light as they travel through the ice. 5,160 light sensors in glass spheres on long cables reach up to 2.45 kilometers deep into the ice and capture this Cherenkov light.
In order to evaluate the measured signals correctly, we have to calibrate the sensors and the ice as a detection medium as accurately as possible and, above all, simulate how the Cherenkov light spreads. We now have to take into account not only impurities in the ice, but also its microstructure as a birefringent polycrystal and thus the refractions that occur at each transition between two crystals.
©: Angelika Stehle
We use LEDs as a defined light source, which are located in a glass sphere together with the light sensors. Their defined light pulses are registered by the sensors in other spheres.
We are currently working on expanding our neutrino telescope: in the IceCube upgrade, we want to bring 700 new detector components into the ice and further improve the calibration methods, for example with the help of new LED flashers. Each flasher is a small circuit board that needs everything to light up a single LED for a few nanoseconds in a precisely defined manner. The trick: we not only design the flashers, but also test and produce them in large numbers in the PRISMA Detector Lab. The final rehearsal in 2020 was a great success with 220 flashers. We are in the starting blocks for the production of 4,500 flashers in 2021.
The pre-integrated detector components with “our” flashers are expected to be installed in seven new boreholes in 2022/23. Being on site in Antarctica is a very formative experience, which I have already had the pleasure of experiencing twice myself. It's not for nothing that the term “ice fever” is doing the rounds among the expedition participants.”
Dr. Martin Rongen is a postdoc in Professor Sebastian Böser's group and works on the IceCube experiment. Being on site in the Antarctic is a very formative experience for him, which he has already had the pleasure of experiencing twice.