No abstract

Deuterium-tritium-loaded capsules at the National Ignition Facility (NIF) are now regularly producing a neutron rich high energy density plasma (nHEDP) with a low-energy "ICF-thermal" neutron density > 10 21 neutrons/cm 3 . These low-energy neutrons are produced via multiple scatter off of the highly compressed capsule and therefore provide insight into the confinement time (τ confinement ) of the assembled plasma. Neutrons are formed in the center of the 5 m NIF chamber that is well suited for minimizing "room return" thermal capture. This nHEDP environment is befitting for activation-based measurements of the (n,γ) cross sections responsible for the formation of heavy elements in astrophysical settings. These experiments also offer the first opportunity to search for the effects of nuclear-plasma interaction-induced excited state population on (n,x) reaction rates in a stellar-like plasma environment. Unfortunately, no capability currently exists at the NIF to measure the neutron spectrum in a capsule down to the 100 eV level required to enable these new classes of nuclearplasma experiments. In this paper we will discuss nHEDP-based neutron capture experiments, compare them to accelerator-based (n,γ) measurements, and discuss the requirements for a NIF-based low energy neutron spectrometer (LENS).

The generation of dynamic high energy density plasmas in the pico-to nanosecond time domain at high-energy laser facilities affords unprecedented nuclear science research possibilities. At the National Ignition Facility (NIF), the primary goal of inertial confinement fusion research has led to the synergistic development of a unique high brightness neutron source, sophisticated nuclear diagnostic instrumentation, and versatile experimental platforms. These novel experimental capabilities provide a new path to investigate nuclear processes and structural effects in the time, mass and energy density domains relevant to astrophysical phenomena in a unique terrestrial environment. Some immediate applications include neutron capture cross-section evaluation, fission fragment production, and ion energy loss measurement in

We report on the most recent and successful effort at controlling the trajectory and symmetry of a high density carbon implosion at the National Ignition Facility. We use a low gasfill (0.3 mg/cc He) bare depleted uranium hohlraum with around 1 MJ of laser energy to drive a 3-shock-ignition relevant implosion. We assess drive performance and we demonstrate symmetry control at convergence 1, 3–5, 12, and 27 to better than ±5 μm using a succession of experimental platforms. The symmetry control was maintained at a peak fuel velocity of 380 km/s. Overall, implosion symmetry measurements are consistent with the pole-equator symmetry of the X-ray drive on the capsule being better than 5% in the foot of the drive (when shocks are launched) and better than 1% during peak drive (main acceleration phase). This level of residual asymmetry should have little impact on implosion performance.