New Cosmic Radiation Detectors
Since 2008, Dr Tim Huege and his Helmholtz Young Investigators Group at the Karlsruhe Institute of Technology (KIT) develop innovative detectors for the more detailed observation of cosmic radiation. The radiation particles are atomic nuclei hitting the Earth's atmosphere with in part high levels of energy. Although they have already been observed for about 100 years, their detailed origin remains hidden. Tim Huege's goal is to find the source of cosmic radiation by means of new technology.
Mr Huege, why is it so difficult to measure cosmic radiation?
The cosmic radiation particles only very rarely reach us. Low-energy particles, for example, from the sun or sources within our galaxy, are fairly frequent and can be measured with satellites or balloons. But the higher the energy level of the particles, the rarer they are. Yet we are most interested in exactly those particles with the highest energy, because they come from sources with the most extreme characteristics.
But do we not have accelerators capable of generating particles such as the Higgs boson? Would not that work also for cosmic radiation?
No, the energy of the particles with the highest energy levels is much too great. The worldwide largest accelerator ring at CERN measures 27 kilometres. In order to generate particles with similarly extreme energy, one would need a ring the size of the orbit of Mercury (approx. 365 million km). We therefore need to measure the cosmic particles. However, as of a certain energy level these are so rare that we need an extremely large measuring surface.
How large are these measuring surfaces?
Many square kilometres. Within that area, numerous detectors are connected in a grid. At the Pierre Auger Observatory in Argentina, the currently largest cosmic radiation observation facility, 1,600 detectors are scattered across 3,000 square kilometres. There, two detector types are combined; we are now developing a third.
Why three types of measurement systems for just one particle?
Cosmic radiation interacts with the atmosphere and does not even reach Earth in its original state. It causes an avalanche of other particles, a so-called air shower, which is several kilometres wide at ground level and which can be measured. A second effect – hence the second detector type – is caused by excitation of nitrogen in the atmosphere, which generates measurable UV radiation. Yet both detector types have their limitations: one measures only a small part of secondary particles, the other works only in clear, dark nights. We therefore need another measured variable and that is radio wave radiation. Air showers emit short radio impulses. We now have developed highly sensitive radio detector stations including their own electricity supply and wireless communication.
According to the Helmholtz programme, your Young Investigators Group expires this year, so what will happen then?
The funding for this Young Investigators Group will stop. But the group was so successfully assessed, that my temporary contract now was changed to a permanent one – an absolutely unique feature of Helmholtz Young Investigators Groups. Given the basis of funding from the institute and by campaigning for additional third-party funds, I can thus continue my research.