  We propose a method to measure the neutrino mass kinematically using beams of
ions which undergo beta decay. The idea is to tune the ion beam momentum so
that in most decays, the electron is forward moving with respect to the beam,
and only in decays near the endpoint is the electron moving backwards. Then, by
counting the backward moving electrons one can observe the effect of neutrino
mass on the beta spectrum close to the endpoint. In order to reach
sensitivities for $m_\nu < 0.2$ eV, it is necessary to control the ion momentum
with a precision better than $\delta p/p < 10^{-5}$, identify suitable nuclei
with low Q-values (in the few to ten keV range), and one must be able to
observe at least O($10^{18}$) decays.
