  In this paper we stress the idea that new, more precise neutrino
cross-sections measurements at low energies will be necessary to improve the
results of future big neutrino detectors, which will be dominated by the
contribution of the systematic errors. The use of a muon beam instead of the
traditional pion beams is proposed. This choice allows the simultaneous
measurement of both, numu and nue interactions and the two helicities, in a
clean environment and with a precise knowledge of the beam flux. We show that
with approx 10^{15} mu's/year and a moderate mass detector (approx 100 tons)
placed close to the muon storage ring, precisions of the order of 10% in
sigma(nu) (E_nu bin size of 100 MeV) can be reached for neutrino energies below
2 GeV.
