Have Polarized Neutrons been as Important as We Expected?

Abstract

My friend John Hayter, one of the pioneers of neutron spin echo, once told me: “If they'd taught you to read in Cambridge, you'd never have tried polarization analysis on IN12.” He had a point. Not about my prowess as a reader or the education offered by my alma mater, I hope, but certainly about the fact that I brashly ignored the values on the ordinate of Figure 1. This figure is taken from the seminal 1970 paper of Moon, Riste and Koehler [1] (MRK), in which they first demonstrated what we now like to call longitudinal polarization analysis. Hayter's point, made with his usual distain for people who do foolish things, was that MRK had used a powerful 85 MW reactor for their experiments and had only accumulated a few counts. John liked to say that MRK killed the polarized neutron field for a decade because people who paid attention to count rates realized that it would be foolish to try to use polarization analysis to examine inelastic scattering from “real” samples that did not scatter as strongly as MRK's “fruit flies.”