  We study the inverse problem of determining a magnetic Schr\"odinger operator
in an unbounded closed waveguide from boundary measurements. We consider this
problem with a general closed waveguide in the sense that we only require our
unbounded domain to be contained into an infinite cylinder. In this context we
prove the unique recovery of the magnetic field and the electric potential
associated with general bounded and non-compactly supported electromagnetic
potentials. By assuming that the electromagnetic potentials are known on the
neighborhood of the boundary outside a compact set, we even prove the unique
determination of the magnetic field and the electric potential from
measurements restricted to a bounded subset of the infinite boundary. Finally,
in the case of a waveguide taking the form of an infinite cylindrical domain,
we prove the recovery of the magnetic field and the electric potential from
partial data corresponding to restriction of Neumann boundary measurements to
slightly more than half of the boundary. We establish all these results by mean
of suitable complex geometric optics solutions and Carleman estimates suitably
designed for our problem stated in an unbounded domain and with bounded
electromagnetic potentials.
