Conceptual design of the gamma-to-electron magnetic spectrometer for the National Ignition Facility

Y Kim; H W Herrmann; H J Jorgenson; D B Barlow; C S Young; W Stoeffl; D Casey; T Clancy; F E Lopez; J A Oertel; T Hilsabeck; K Moy; S H Batha

doi:10.1063/1.4892900

Conceptual design of the gamma-to-electron magnetic spectrometer for the National Ignition Facility

Rev Sci Instrum. 2014 Nov;85(11):11E122. doi: 10.1063/1.4892900.

Authors

Y Kim¹, H W Herrmann¹, H J Jorgenson¹, D B Barlow¹, C S Young¹, W Stoeffl², D Casey², T Clancy², F E Lopez¹, J A Oertel¹, T Hilsabeck³, K Moy⁴, S H Batha¹

Affiliations

¹ Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
² Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
³ General Atomics, San Diego, California 92186, USA.
⁴ National Security Technologies, Special Technologies Laboratory, Santa Barbara, California 93111, USA.

PMID: 25430301
DOI: 10.1063/1.4892900

Abstract

The Gamma-to-Electron Magnetic Spectrometer (GEMS) diagnostic is designed to measure the prompt γ-ray energy spectrum during high yield deuterium-tritium (DT) implosions at the National Ignition Facility (NIF). The prompt γ-ray spectrum will provide "burn-averaged" observables, including total DT fusion yield, total areal density (ρR), ablator ρR, and fuel ρR. These burn-averaged observables are unique because they are essentially averaged over 4π, providing a global reference for the line-of-sight-specific measurements typical of x-ray and neutron diagnostics. The GEMS conceptual design meets the physics-based requirements: ΔE/E = 3%-5% can be achieved in the range of 2-25 MeV γ-ray energy. Minimum DT neutron yields required for 15% measurement uncertainty at low-resolution mode are: 5 × 10(14) DT-n for ablator ρR (at 0.2 g/cm(2)); 2 × 10(15) DT-n for total DT yield (at 4.2 × 10(-5) γ/n); and 1 × 10(16) DT-n for fuel ρR (at 1 g/cm(2)).