Inertial confinement fusion neutron images

Abstract

At the OMEGA laser facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)], 14-MeV neutron images are acquired with a 20-μm resolution and a large signal-to-noise ratio (SNR) using penumbral and ring apertures. The two aperture types produce coded images of the source that are unfolded using a similar autocorrelation method. The techniques provide comparable images for various deuterium-tritium filled target implosions, with glass and plastic (CH) shells. SNR analysis reveals that the annular (ring) technique will achieve a good image quality at the 10-μm resolution level with the planned upgrade of our novel detector. The detector is an array of 85-μm-diam capillary tubes filled with a liquid scintillator. Its resolution is limited to 650μm by the track length of the elastically scattered recoil protons. Replacing the hydrogen in the scintillator with deuterium improves detector spatial resolution to 325μm, and makes high source resolution achievable. The readout design provides an efficient light collection of the scintillation photons by relaying the image through a fiber optic taper. Improved efficiency produces images with better SNR. Also, the increased detector sensitivity allows single event recording of 2.45-MeV neutron interactions. For the first time ever, we show neutron images of deuterium filled, warm, and cryogenic target implosions.