Electromagnetic design of the spectrometer section of the KATRIN experiment

The aim of the KATRIN experiment is to determine the neutrino mass directly, with a sensitivity of 0.2 eV (90% CL). KATRIN is located at KIT (Karlsruhe Institute of Technology) and is currently under construction (J. Angrik et al., 2004 [3]). The experiment will analyze the shape of the tritium β-spectrum in the region of the tritium endpoint. A nonzero neutrino mass reduces the maximal energy of the electron and changes the shape of the tritium spectrum, especially close to the endpoint. To reach the sensitivity KATRIN is aiming for, an high energy resolution as well as high statistics and low background are needed. In order to achieve this, KATRIN uses the MAC-E-Filter (Magnetic Adiabatic Collimation followed by Electrostatic Filter) principle, and several background reduction mechanisms. The optimization of both MAC-E-Filter and background reduction is the main challenge of the electromagnetic design. This article describes how these issues are tackled and discusses the actual realization of two major electromagnetic design components.