Abstract: The direction of propagation of a neutral particle beam is determined by positioning a shadow wire in the beam and positioning an array of detector wires downstream from the shadow wire. The shadow wire forms a shadow region downstream thereof, i.e., a region which is depleted of particles due to multiple scattering events. The detector wires are each formed of a different material and the count rate of K shell X-rays emitted from the individual detector wires are used to determine the loction of the centroid of the shadow at the detector wire array. The location of the center of the shadow wire and the position of the downstream shadow centroid are used to establish the direction of beam propagation.