Göttingen 2012 – wissenschaftliches Programm
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T: Fachverband Teilchenphysik
T 107: Niederenergie-Neutrinophysik/Suche nach Dunkler Materie 2
T 107.9: Vortrag
Montag, 27. Februar 2012, 18:50–19:05, ZHG 103
Electrons and ions in the KATRIN source and transport system — •Ferenc Glück — Karlsruhe Institute of Technology, IEKP
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. Within the KATRIN source, tritium beta decays occur with 1011 s−1 rate, creating primary electrons (below 18.6 keV kinetic energy) and various positive ions: 3HeT+, He+ and T+. The primary electrons make ionization collisions with the T2 molecules, producing low energy (order of few eV) secondary electrons and tritium ions (T2+, T+); 1 primary electron creates on the average 15 electron-ion pairs. Due to inelastic and elastic collisions with T2 molecules, most of the secondary electrons cool down to gas temperature (30 K). The secondary electrons create also T− ions. Due to the collisions of the previous positive ions with T2 molecules, T3+ and tritium cluster ions (T5+, T7+, etc.) are produced, which can recombine with the secondary electrons. For the KATRIN experiment it is important that the many positive tritium ions do not reach the pre- and main spectrometers (otherwise an extremely large background is produced), and that the neutrino mass determination should not be significantly influenced by beta decay, space charge and plasma instability effects of the above electron-ion plasma that will be present in the source and transport system.
We acknowledge support by the BMBF of Nr. 05A11VK3.