  Oscillations of the neutron into a hidden sector particle are processes
predicted in various Standard Model extensions. This extra channel for neutron
disappearance has not been tested experimentally in large portions of the
oscillation parameter space. Several efforts have been recently made on
revising the oscillation time limits at low mass-splitting in ultra-cold
neutron (UCN) storage experiments, and at larger mass-splitting in
passing-through-wall experiments. In this work, we present the expected
sensitivity of an experiment searching for neutron hidden neutron oscillations
at intermediate mass-splitting via the application of magnetic fields in the
range $B_0=30-1100$ $\mu$T. This experiment was performed at the
Institut-Laue-Langevin using a novel UCN counter to monitor the beam flux. The
measured UCN rate and the data collection technique predict a sensitivity on
the oscillation time at the level of a couple of seconds.
