AVS 49th International Symposium
    Vacuum Technology Tuesday Sessions
       Session VT-TuP

Paper VT-TuP1
The KATRIN Neutrino Mass Experiment - Vacuum Technological Aspects

Tuesday, November 5, 2002, 5:30 pm, Room Exhibit Hall B2

Session: Poster Session
Presenter: C. Day, Forschungszentrum Karlsruhe, Germany
Authors: C. Day, Forschungszentrum Karlsruhe, Germany
V. Hauer, Forschungszentrum Karlsruhe, Germany
J. Bonn, University of Mainz, Germany
Correspondent: Click to Email
In modern particle physics, one of the most challenging task is to determine the rest mass of neutrinos. The energy spectrum of the electrons of the @beta@ decay can be used to derive upper limits of the electron neutrino mass. A new large tritium experiment is currently being planned, the KATRIN experiment, which is expected to increase the resolution of mass determination by one order of magnitude. It is an international effort and will be built up and operated in FZK, Germany. The KATRIN vacuum system can be subdivided into three main parts, the windowless gaseous tritium source (WGTS), the differential pumping section, and the pre- and main spectrometer. The WGTS introduces tritium gas into the central piping system, operated under fine vacuum conditions. Further in spectrometer direction follows a differentially pumped section to reduce the gas pressure by nine orders of magnitude. This is realised by a cascade of turbomolecular pumps combined with a cryogenic pump system (Ar frost). Between the tritium source and the main spectrometer a pre-spectrometer is inserted, acting as an energy pre-filter. The key component of the new experiment is the large MAC-E-filter with a diameter of 7 m and an overall length of about 20 m, designed for XHV conditions. The spectrometers are pumped by a two-stage system, comprising turbomolecular pumps with high compression ratio for hydrogen, and getter pump modules. This paper delineates the underlying concepts for the three different vacuum systems. Special requirements are full tritium compatibility, operation in strong magnetic fields and under high voltage conditions. The differential pumping section, especially the final cryogenic pump, must provide a capture probability of almost unity, to allow for XHV conditions in the pre-spectrometer tank. To limit the pumping speed requirements with respect to the getter pumps, the outgassing of the spectrometer vessel walls must be reduced to an absolute minimum.