The world´s largest Helmholtz Coil System

Neutrinos are regarded as ghostly particles. Produced in the Big Bang in great numbers, they permeate the universe and play an essential role in its development. Nevertheless, we only know very little about their properties, and we don’t even know their mass yet. Working in collaboration with colleagues from Germany, Europe and the United States, astroparticle physicists at the Karlsruhe Institute of Technology have built an enormous spectrometer called Karlsruhe Tritium Neutrino Experiment – KATRIN in short – to determine the neutrino mass. They aim to do this by using the decay of tritium (hydrogen-3) into helium-3, in which both electrons and neutrinos are emitted.

By precision-determining the electron energies, the scientists can identify the neutrino mass. However, a suitable magnetic guide field has to be generated at the spectrometer and, furthermore, the Earth’s magnetic field has to be compensated as well as possible. “This is why we are building the world’s largest Helmholtz Coil System capable of generating a magnetic field along the whole length of the KATRIN spectrometer,” says Professor Dr. Guido Drexlin, who is in charge of the KATRIN experiment. This involves a frame of 15 rings made of aluminium profiles with diameters of 12.6 metres bearing the twists and turns of the coil which generate the magnetic guiding field. The magnetic field can be set at between three and six Gauss.

To fine-tune the magnetic guide field, each ring can be operated at different power rates. A maximum of up to 70 amperes is planned. To shield the Earth’s magnetic field, which has a strength of roughly 0.5 Gauss, two further coil systems are integrated vertically and horizontally relative to the axis of the spectrometer making use of the ring structure of the Helmholtz Coil. After commissioning of the coil systems, the first experiments with KATRIN are planned for summer 2010.