Abstract—The detection of fast neutrons has important applications
in several fields including solar, geospace and planetary
physics. Neutrons are challenging to detect and measurements of
them typically suffer from high background rates. High-energy
neutrons (>50 MeV) pose even more challenges, because the
traditional double-scatter technique based on a time-of-flight
(ToF) measurement is limited by short flight paths and small
detector sizes characteristic of small satellite platforms. It is now
possible to perform high-energy neutron measurements inside
a large monolithic detector by imaging the recoil proton tracks,
thus eliminating the need for a measure of the time-of-flight. The
concept is based on a spectrometer assembled from numerous
thin hydrogenous scintillating fibers that allow ionization track
imaging. Fine grained readout is now possible with arrays of
1-mm pitch silicon photomultipliers (SiPMs). The Solar Neutron
TRACking (SONTRAC) instrument, equipped with scintillating
fibers readout with SiPMs sensors, provides high-resolution,
fine grained, imaging of fast (between 20-200 MeV) neutron
scatters in a compact, low-power design ideal for small satellite
(and aircraft) platforms. We discuss below applications of this
technology and performance characteristics of the prototype
SONTRAC instrument.
