Authors: J. Grant Mitchell (NASA/GSFC), Georgia A. de Nolfo (NASA/GSFC), Jim Ryan (UNH), Alessandro Bruno (NASA/GSFC)

Fast neutrons ( > 0.5 MeV) are ubiquitous in nature, originating from nuclear spallation in environments including the solar corona, within planetary atmospheres, and in the lunar regolith.  However, measurements of fast neutrons of solar origin are extremely limited due to challenges imposed by high backgrounds and the relatively short lifetime of free neutrons before they undergo beta decay.  These measurements are a critical missing piece in understanding the spectral and temporal characteristics of energetic particle energization and transport within the solar corona.  Fast neutrons fill a gap in the interacting ion spectrum between lower energy gamma-rays produced by nuclear de-excitation (<10 MeV) and higher energy (>100 MeV) gamma-rays produced by neutral pion decay.  Gamma-rays and neutrons offer complementary methods for examining how flare particle energization evolves in time.   Furthermore, both gamma-rays and neutrons provide insight into the composition of the chromosphere/photosphere and the accelerated particles.  Techniques for neutron spectroscopy, both traditional and upcoming, are presented as well as potential mission concepts that can expand our knowledge of solar neutrons.