Neutron Experimental Techniques for n(p)

Abstract

The determination of electron momentum density distributions in condensed matter is now a well established technique and the experimental methods employed have been adequately summarised in this volume by M J Cooper [1] (recent x-ray and electron techniques) and by S Berko [2] (positron annihilation studies). These well established experimental techniques contrast sharply with the more recent inelastic scattering studies involving high energy neutrons. The requirement for intense high energy neutron beams emerged from the theoretical work of Hohenberg and Platzman [3] who showed that such energetic beams were necessary in order to approach the limits imposed by the Impulse Approximation. Moreover, the Impulse Approximation was a necessary fulfillment of the experimental conditions to facilitate the interpretation of the results without recourse to complex final state corrections [4] so evident in the earlier momentum density work on reactor sources [5]. With the advent of pulsed neutron sources, and their abundant flux of epithermal neutrons, there have naturally been significant developments in the experimental methods used to obtain atomic momentum distributions, n(p). Such techniques are now more commonly referred to as Deep Inelastic Neutron Scattering (DINS) or Neutron Compton Scattering. It is therefore the purpose of this chapter to highlight the basic neutron experimental methods with particular emphasis on pulsed source techniques.