Using VISAR to assess the M-band isotropy in hohlraums

In laser basedradiation flow experiments, drive variability can often overwhelm the physics sensitivity that one seeks to quantify.Hohlraums can help by providing a more symmetrized, Planckian-like source. However, at higher temperatures, the hohlraum ’s actual emission can deviate significantly from a truly blackbody, Lambertian source. At the National Ignition Facility (NIF), Dante provides the best quantification ofhohlraum output. Unfortunately, limited diagnostic access coupled with NIF ’s natural symmetry does not allow for Dantemeasurements at more than two angles. As part of the CEPHEUS campaign on NIF, proof-of-principle experiments to better quantify thegoldM-band isotropy were conducted. These experiments positioned beryllium/aluminummirrors at differing angles, offset from thehohlraum. Filtering removes the thermal emission of thehohlraum and the remainingM-bandradiation is preferentially absorbed in thealuminum layer. The subsequenthydrodynamic motion ismeasured via VISAR. Although indirect, thisM-bandmeasurement can be made at any angle.

Source: Review of Scientific Instruments - September 27, 2016 Category: Physics Authors: N. E. Lanier, J. L. Kline and J. Morton Source Type: research