Toward CP-even neutrino beam

The best method of measuring CP violating effect in neutrino oscillation experiments is to construct and use a neutrino beam made of an ideal mixture of ν _e and ν _e of monochromatic lines. The conceptual design of such a beam is described, together with how to measure the CP-odd quantity. We propose to exploit an accelerated unstable hydrogen-like heavy ion in a storage ring, whose decay has both electron capture and bound beta decay with a comparable fraction.