  We have performed small-angle neutron scattering (SANS) of the flux line
lattice (FLL) in a Fe doped NbSe_2 sample which presents a large peak effect in
the critical current. The scattered intensity and the width of the Bragg peaks
of the equilibrium FLL indicate an ordered structure in the peak effect zone.
The history dependence in the FLL structure has been studied using field cooled
and zero field cooled procedures, and each state shows the same intensity of
Bragg scattering and good orientational order. These results strongly suggest
that the peak effect is unrelated to a bulk disordering transition, and confirm
the role of a heterogeneous distribution of screening current.
