  The Karlsruhe Tritium Neutrino experiment KATRIN will allow a model
independent measurement of the neutrino mass scale with an expected sensitivity
of 0.2 eV/c^{2} (90% C.L.) and so will help to clarify the role of neutrinos in
the early universe is the direct measurement of the mass of the electron
anti-neutrino. KATRIN investigates spectroscopically the electron spectrum from
tritium beta- decay close to the kinematic endpoint of 18.6 keV with a high
resolution electro-static filter of unprecedented energy resolution of 0.93 eV.
KATRIN will be built at the Tritium Laboratory Karlsruhe on site of the KIT
Campus North. For such a precise mass-determination a key parameter is the
stability of the source in terms of beta-activity und isotopic purity. For that
purpose KATRIN uses a strong windowless gaseous tritium source of almost pure
molecular tritium (95%) with a throughput of 40 g tritium per day stabilized on
0.1% level. The decay electrons are guided adiabatically from the source to the
spectrometer by means of superconducting magnets while at the same time the
tritium flow rate to the spectrometers has to be reduced by a factor > 1E14. To
reach the sensitivity KATRIN is aiming for, an high energy resolution as well
as high statistics and low background are needed. A tandem spectrometer system
is used for energy analysis. The transport section consists of a differential
pumping system (DPS2-F) and a cryogenic pumping section (CPS). In the DPS2-F
the tritium flow will be reduced by differential pumping while in the CPS
tritium will be adsorbed on a pre-condensed argon layer prepared inside
KATRIN's beamtube. To assure the required stability of the source on 0.1% level
a stabilized tritium injection in the source is required. This is done by
closed tritium loops. The purity and composition of the injected gas will be
monitored by Laser Raman spectroscopy.
