We have developed a new scattering geometry for magnetic neutron scattering experiments on YBa2Cu3O7 in which the phonon background around q similar to (pi/alpha,pi/alpha), h omega similar to 40meV is significantly reduced. We use this new approach to study the previously detected, sharp magnetic excitation at similar to 40meV in the superconducting state in detail. The excitation does not shift substantially in energy up to at least 75K (similar to 0.8T(c)). Polarized neutron scattering experiments (horizontal minus vertical field) confirm the magnetic origin of the 40meV excitation and put stringent limits on the magnetic scattering intensity in the normal stale.