Fluence-compensated down-scattered neutron imaging using the neutron imaging system at the National Ignition Facility

D T Casey; P L Volegov; F E Merrill; D H Munro; G P Grim; O L Landen; B K Spears; D N Fittinghoff; J E Field; V A Smalyuk

doi:10.1063/1.4960065

Fluence-compensated down-scattered neutron imaging using the neutron imaging system at the National Ignition Facility

Rev Sci Instrum. 2016 Nov;87(11):11E715. doi: 10.1063/1.4960065.

Authors

Affiliations

¹ Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
² Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.

PMID: 27910388
DOI: 10.1063/1.4960065

Abstract

The Neutron Imaging System at the National Ignition Facility is used to observe the primary ∼14 MeV neutrons from the hotspot and down-scattered neutrons (6-12 MeV) from the assembled shell. Due to the strong spatial dependence of the primary neutron fluence through the dense shell, the down-scattered image is convolved with the primary-neutron fluence much like a backlighter profile. Using a characteristic scattering angle assumption, we estimate the primary neutron fluence and compensate the down-scattered image, which reveals information about asymmetry that is otherwise difficult to extract without invoking complicated models.