Neutron source reconstruction from pinhole imaging at National Ignition Facility.

The neutron imaging system at the National Ignition Facility (NIF) is an important diagnostic tool for measuring the two-dimensional size and shape of the neutrons produced in the burning deuterium-tritium plasma during the ignition stage of inertial confinement fusion (ICF) implosions at NIF. Since the neutron source is small (∼100 μm) and neutrons are deeply penetrating (>3 cm) in all materials, the apertures used to achieve the desired 10-μm resolution are 20-cm long, single-sided tapers in gold. These apertures, which have triangular cross sections, produce distortions in the image, and the extended nature of the pinhole results in a non-stationary or spatially varying point spread function across the pinhole field of view. In this work, we have used iterative Maximum Likelihood techniques to remove the non-stationary distortions introduced by the aperture to reconstruct the underlying neutron source distributions. We present the detailed algorithms used for these reconstructions, the stopping criteria used and reconstructed sources from data collected at NIF with a discussion of the neutron imaging performance in light of other diagnostics.

[1]  C R Danly,et al.  Simultaneous usage of pinhole and penumbral apertures for imaging small scale neutron sources from inertial confinement fusion experiments. , 2012, The Review of scientific instruments.

[2]  David C. Eder,et al.  Development of Nuclear Diagnostics for the National Ignition Facility (invited) , 2006 .

[3]  L. Lucy An iterative technique for the rectification of observed distributions , 1974 .

[4]  E. Veklerov,et al.  Stopping Rule for the MLE Algorithm Based on Statistical Hypothesis Testing , 1987, IEEE Transactions on Medical Imaging.

[5]  P L Volegov,et al.  The neutron imaging diagnostic at NIF (invited). , 2012, The Review of scientific instruments.

[6]  M. Moran,et al.  Image reconstruction algorithms for inertial confinement fusion neutron imaging , 2006 .

[7]  D Ros,et al.  Evaluation of a cross-validation stopping rule in MLE SPECT reconstruction. , 1998, Physics in medicine and biology.

[8]  William H. Richardson,et al.  Bayesian-Based Iterative Method of Image Restoration , 1972 .

[9]  Peter Pazuchanics,et al.  The National Ignition Facility neutron imaging system. , 2008, The Review of scientific instruments.

[10]  D. Clark,et al.  Modeling the National Ignition Facility neutron imaging system. , 2010, The Review of scientific instruments.

[11]  E. T. Alger,et al.  Cryogenic thermonuclear fuel implosions on the National Ignition Facility , 2012 .

[12]  Paul A. Bradley,et al.  ICF ignition capsule neutron, gamma ray, and high energy x-ray images , 2003 .

[13]  E. R. Podolyak,et al.  Programs for signal recovery from noisy data using the maximum likelihood principle I. General description , 1993 .

[14]  R Tommasini,et al.  Extracting core shape from x-ray images at the National Ignition Facility. , 2012, The Review of scientific instruments.

[15]  Albert Macovski,et al.  A Maximum Likelihood Approach to Emission Image Reconstruction from Projections , 1976, IEEE Transactions on Nuclear Science.

[16]  George Kontaxakis,et al.  PET image reconstruction: A stopping rule for the MLEM algorithm based on properties of the updating coefficients , 2010, Comput. Medical Imaging Graph..