Measurement of the neutron lifetime using magnetically trapped neutrons: tSPECT

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The lifetime of the free neutron is a basic physical quantity, which is relevant in a variety of different fields of particle and astrophysics. In this project a precise measurement of the neutron lifetime using three-dimensional magnetic storage of ultra-cold neutrons (UCN) will be conducted. The differences in the results of experiments using different methods, beam and material bottle experiments, indicate that there are still some subtle and not understood effects in some of these experiments. Rather than relying on neutron reflection from a material wall, where neutron up-scattering and capture cause significant wall losses, magnetically trapped neutrons do not interact with matter during storage. That is the obvious appeal to the use of magnetic and gravitational confinement, where, at least in principle, the dynamics of the neutron-trap interaction is well understood and under control. The experiment tSPECT is located at the pulsed UCN-source of the TRIGA Mainz research reactor. It will become fully operational end of 2016. In the requested 3 years funding period beam times will be conducted to study and to minimize the systematic effects. A measurement of a competitive neutron lifetime with ~ 1 s accuracy is planned towards the end of the funding period (during the last third). We aim to continue tSPECT in an upgraded version in the framework of PRISMA II, the planned continuation of the excellence cluster PRISMA. An overall accuracy of delta tn = 0.2-0.3 s is envisaged.