Dresden 2013 – scientific programme
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T: Fachverband Teilchenphysik
T 99: Niederenergie-Neutrinophysik 1
T 99.2: Talk
Monday, March 4, 2013, 11:20–11:35, WIL-A317
Chaotic motion of stored electrons in the KATRIN main spectrometer — •Ferenc Glück — Karlsruhe Institute of Technology
The aim of the KATRIN experiment is to determine the absolute neutrino mass scale in a model independent way, by measuring the electron energy spectrum shape near the endpoint of tritium beta decay. An ultra-low background level of 10 mHz is necessary to reach the design sensitivity of 200 meV. Magnetically stored high energy (above few keV) electrons, arising from radioactive decays of radon and tritium in the KATRIN main spectrometer, can produce several hundreds of secondary electrons by ionization of residual gas, leading to enhanced background rates for several hours. Tracking simulations with highly accurate field calculations and with 8th order Runge-Kutta methods have been performed, in order to investigate the long-time storage conditions of the high energy primary electrons. The simulations show that the motion of these electrons in the main spectrometer is non-adiabatic and chaotic. For example, for two electrons starting exactly with the same velocity vector and with 10−14 m distance of their starting points, the two trajectories start to diverge exponentially from each other after a few µs real time. Sensitive dependence on the initial conditions is a typical attribute of chaos.
We acknowledge support by the BMBF of Nr. 05A11VK3 and by the Helmholtz Association.