  Based on elastic collisions, the linear momentum of a fast neutron can be
measured from as few as two consecutive recoil ion tracks plus the vertex
position of the third collision, or `two and half' ion tracks. If the time
delay between the first two consecutive ion tracks is also measured, the number
of ion tracks can be reduced to one and a half. The angular and magnitude
resolutions are limited by ion range straggling to about ten percent.
Multi-wire proportional chambers and light-field imaging are discussed for fast
neutron tracking. Single-charge or single-photon detection sensitivity is
required in either approach. Light-field imaging is free of
charge-diffusion-induced image blur, but the limited number of photons
available can be a challenge. $^1$H,$^2$H and $^3$He could be used for the
initial development of fast neutron trackers based on light-field imaging.
