Investigation of the possibility of gamma-ray diagnostic imaging of target compression at NIF

Daniel A. Lemieux, Camille Baudet, Gary P. Grim, H. Bradford Barber, Brian W. Miller, David Fasje, Lars R. Furenlid

Research output: Chapter in Book/Report/Conference proceedingConference contribution

5 Scopus citations

Abstract

The National Ignition Facility at Lawrence Livermore National Laboratory is the world's leading facility to study the physics of igniting plasmas. Plasmas of hot deuterium and tritium, undergo d(t,n)α reactions that produce a 14.1 MeV neutron and 3.5 MeV a particle, in the center of mass. As these neutrons pass through the materials surrounding the hot core, they may undergo subsequent (n,x) reactions. For example, 12C(n,n′γ) 12C reactions occur in remnant debris from the polymer ablator resulting in a significant fluence of 4.44 MeV gamma-rays. Imaging of these gammas will enable the determination of the volumetric size and symmetry of the ablation; large size and high asymmetry is expected to correlate with poor compression and lower fusion yield. Results from a gamma-ray imaging system are expected to be complimentary to a neutron imaging diagnostic system already in place at the NIF. This paper describes initial efforts to design a gamma-ray imaging system for the NIF using the existing neutron imaging system as a baseline for study. Due to the cross-section and expected range of ablator areal densities, the gamma flux should be approximately 10-3 of the neutron flux. For this reason, care must be taken to maximize the efficiency of the gamma-ray imaging system because it will be gamma starved. As with the neutron imager, use of pinholes and/or coded apertures are anticipated. Along with aperture and detector design, the selection of an appropriate scintillator is discussed. The volume of energy deposition of the interacting 4.44 MeV gamma-rays is a critical parameter limiting the imaging system spatial resolution. The volume of energy deposition is simulated with GEANT4, and plans to measure the volume of energy deposition experimentally are described. Results of tests on a pixellated LYSO scintillator are also presented.

Original languageEnglish (US)
Title of host publicationPenetrating Radiation Systems and Applications XII
DOIs
StatePublished - 2011
EventPenetrating Radiation Systems and Applications XII - San Diego, CA, United States
Duration: Aug 21 2011Aug 24 2011

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume8144
ISSN (Print)0277-786X

Other

OtherPenetrating Radiation Systems and Applications XII
CountryUnited States
CitySan Diego, CA
Period8/21/118/24/11

Keywords

  • GEANT4
  • NIF
  • energy deposition
  • fusion
  • gamma
  • ignition
  • scintillator

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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  • Cite this

    Lemieux, D. A., Baudet, C., Grim, G. P., Barber, H. B., Miller, B. W., Fasje, D., & Furenlid, L. R. (2011). Investigation of the possibility of gamma-ray diagnostic imaging of target compression at NIF. In Penetrating Radiation Systems and Applications XII [814407] (Proceedings of SPIE - The International Society for Optical Engineering; Vol. 8144). https://doi.org/10.1117/12.895765