High-sensitivity scintillating-fiber imaging detector for high-energy neutrons

Abstract

We have created a detector to image the neutrons emitted by imploded inertial-confinement fusion targets. The 14 MeV neutrons, which are produced by deuterium–tritium fusion events in the target, pass through an aperture to create an image on the detector. The neutron radiation is converted to blue light (430 nm) with a 20 cm2 array of plastic scintillating fibers. Each fiber is 10 cm long with a 1 mm2 cross section; approximately 35 000 fibers make up the array. The resulting blue-light image is reduced in size and amplified by a sequence of fiber-optic tapers and image intensifiers, then acquired by a charge-coupled device camera. The fiber-optic readout system was tested separately for overall throughput and spatial resolution; the throughput was 0.22 electrons/photon, and the resolution was 0.8 mm. We also characterized the overall efficiency of the detector using the DT-fusion neutrons emitted by inertial confinement targets; the measured value was 14 electrons/pixel/neutron. Several neutron images of laser-fusion targets have been obtained with the detector. We describe the detector, present characterization results, and give examples of the neutron images.