title: Conceptual design of the gamma-to-electron magnetic spectrometer for the National Ignition Facility.
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)).
authors.affiliation: Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Kim
authors.affiliation: Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: H W
authors.initials: HW
authors.lastname: Herrmann
authors.affiliation: Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: H J
authors.initials: HJ
authors.lastname: Jorgenson
authors.affiliation: Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: D B
authors.initials: DB
authors.lastname: Barlow
authors.affiliation: Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: C S
authors.initials: CS
authors.lastname: Young
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
authors.forename: W
authors.initials: W
authors.lastname: Stoeffl
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
authors.forename: D
authors.initials: D
authors.lastname: Casey
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
authors.forename: T
authors.initials: T
authors.lastname: Clancy
authors.affiliation: Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: F E
authors.initials: FE
authors.lastname: Lopez
authors.affiliation: Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Oertel
authors.affiliation: General Atomics, San Diego, California 92186, USA.
authors.forename: T
authors.initials: T
authors.lastname: Hilsabeck
authors.affiliation: National Security Technologies, Special Technologies Laboratory, Santa Barbara, California 93111, USA.
authors.forename: K
authors.initials: K
authors.lastname: Moy
authors.affiliation: Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: S H
authors.initials: SH
authors.lastname: Batha