Image reconstruction algorithms for inertial confinement fusion neutron imaging

A neutron imaging system is required to diagnose ignition implosions at the National Ignition Facility. Such a system is required to be able to resolve features in the imploded target core as small as 5 μm. The system will use a pinhole-camera-type geometry with a nonideal coded aperture and will employ image restoration techniques. The choice of image reconstruction method will be important in recovering the best possible source images from the recorded data. Monte Carlo transport simulations with MCNP5 make it possible to estimate the performance of the neutron imaging system based on calculated energy-dependent image edits of a failed inertial confinement fusion implosion. Simulations of the recorded neutron images include specific aperture designs, a pixelated energy- and time-dependent scintillator array, and an intensified gated charge coupled device camera for recording the images. An initial series of simulations used a source that was binned into 1 MeV increments from 6 to 18 MeV, an imaging aperture approximately 40 cm from target chamber center, and a detector array at 40 m, for a system magnification of around 100. A modified regularization method used the calculated point spread function of the overall system to deconvolve the simulated images. The results demonstrate the possibility that the imaging system can satisfy the resolution requirements and provide the desired images of the neutron emission source