Abstract and subjects
Summary form only given. The neutron imaging diagnostic has recently been commissioned at the National Ignition Facility. We will present the diagnostic performance characteristics, which have been measured with the collection of these first neutron images. The goal for this diagnostic is to collect two pinhole images at two different times. The long flight path results in a chromatic separation of the neutrons, the first image will be of the 14 MeV neutrons and the second image of the 10-12 MeV neutrons. The combination of these two images will provide data on the size and shape of the compressed capsule as well as a measure of the quantity and spatial distribution of the cold fuel surrounding this core. The imager uses an array of 20 pinholes and three mini-penumbra machined in 20 cm of layered gold and tungsten, with an apex at 32.5 cm from the source to produce images in a scintillator array at 2800 cm. This geometry provides a magnification factor of 85 at the scintillator. The scintillator is a coherent array of scintillating fibers, which is viewed from the two ends by two fast-gated image collection systems. The first neutron images, collected in February, 2011, have provided the first measure of system performance at NIF. These results will be presented along with an interpretation of future system performance.