Solar, atmospheric, and reactor experiments have all conclusively shown that neutrinos possess a small, yet finite, mass. Limits from previous experiments place the neutrino mass at less than 2 eV, while limits from oscillitory experiments place a lower bound of 50 meV on the neutrino mass. The effects of neutrino mass within this scale (50-2000 eV) will have a direct impact on galaxy evolution and cosmology.
The KATRIN experiment is the next generation tritium beta decay experiment designed to probe the neutrino mass down to this scale (200 meV at 90% C.L.). It does so by using a very precise electron spectrometer so as to measure the electron energy spectrum from triutium decay. Unlike other methods, KATRIN makes a direct measurement of the neutrino mass, with as few model assumptions as possible.
KATRIN is currently under construction and plans to start data taking in 2009-2010.
To see a movie about the voyage of the KATRIN spectrometer, click here