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).

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Isospin properties of dipole excitations in74 Ge are investigated using the (α, α ′ γ) reaction and compared to (γ, γ ′ ) data. The results indicate that the dipole excitations in the energy region of 6 to 9 MeV adhere to the scenario of the recently found splitting of the region of dipole excitations into two separated parts: one at low energy being populated by both isoscalar and isovector probes and the other at high energy, excited only by the electromagnetic probe. RQTBA calculations show a reduction in the isoscalar E1 strength with an increase in excitation energy which is consistent with the measurement.

The neutron time-of-flight (nTOF) diagnostics used to characterize implosions at the National Ignition Facility (NIF) has necessitated the development of novel scintillators that exhibit a rapid temporal response and high light yield. One such material, a bibenzyl-stilbene mixed single-crystal organic scintillator grown in a 99.5:0.5 ratio in solution, has become the standard scintillator used for nTOF diagnostics at NIF. The prompt fluorescence lifetime and relative light yield as a function of proton energy were determined to calibrate this material as a neutron detector. The temporal evolution of the intensity of the prompt fluorescent response was modeled using first-order reaction kinetics and the prompt fluorescence decay constant was determined to be 2.46 6 0.01 (fit) 6 0.13 (systematic) ns. The relative response of the bibenzyl-stilbene mixed crystal generated by recoiling protons was measured, and results were analyzed using Birks' relation to quantify the non-radiative quenching of excitation energy in the scintillator. V C 2014 AIP Publishing LLC. [http://dx.