  Neutrino oscillation experiments from different sources have demonstrated
non-vanishing neutrino masses and flavour mixings. The next experiments have to
address the determination of the connecting mixing U(e3) and the existence of
the CP violating phase. Whereas U(e3) measures the strength of the oscillation
probability in appearance experiments, the CP phase acts as a phase-shift in
the interference pattern. Here we propose to separate these two parameters by
energy dependence, using the novel idea of a monochromatic neutrino beam
facility based on the acceleration of ions that decay fast through electron
capture. Fine tuning of the boosted neutrino energy allows precision
measurements able to open a window for the discovery of CP violation, even for
a mixing as small as 1 degree.
