Aperture tolerances for neutron-imaging systems in inertial confinement fusion

Abstract

Neutron-imaging systems are being considered as an ignition diagnostic for the National Ignition Facility (NIF) [Hogan et al., Nucl. Fusion 41, 567 (2001)]. Given the importance of these systems, a neutron-imaging design tool is being used to quantify the effects of aperture fabrication and alignment tolerances on reconstructed neutron images for inertial confinement fusion. The simulations indicate that alignment tolerances of more than 1 mrad would introduce measurable features in a reconstructed image for both pinholes and penumbral aperture systems. These simulations further show that penumbral apertures are several times less sensitive to fabrication errors than pinhole apertures.

Progress toward the development and testing of source reconstruction methods for NIF neutron imaging

“…6,7,14 Since the PSF of the pinhole is not shift invariant, the reconstruction will change depending on where the source actually was relative to where we thought it was during the reconstruction since a different set of PSFs is used in the two cases. 6,7,14 Since the PSF of the pinhole is not shift invariant, the reconstruction will change depending on where the source actually was relative to where we thought it was during the reconstruction since a different set of PSFs is used in the two cases.…”

High resolution neutron imaging for inertial confinement fusion experiments

“…These results were then compared with Monte-Carlo calculations performed with the GEANT4 toolkit [14]- [15]. Aperture alignment and deformation tolerances were also studied by Ghilea et al comparing tolerances of a penumbral aperture relatively to a pinhole aperture [16]. They proposed a design tool for the evaluation of aperture tolerances.…”

Obtaining point spread function of penumbral encoding aperture with “expectation maximization” algorithm based on matched source-image pair experiment

“…[5][6][7] However, many factors such as the isoplanatic property of the encoding aperture, edge sharpness of PSF and the optimization on the design of wide dynamic range, as well as measuring the precise PSF have limited the development of penumbral encoded imaging technology. [7][8][9][10][11] Penumbral encoded imaging technology started in 1980s, when Nugent reported on a series x-ray and neutron penumbral imaging simulation of fusion plasmas. 1,8 Subsequently, Ress et al 2 reported on the first experimental observation of fusion neutron penumbral encoded imaging with a spatial resolution 80 m. In the 1990s, Ress 12 attempted a penumbral encoded aperture space-invariant design, where some assumptions and approximations were made to ensure the isoplanatic property of the system point spread function.…”