Compact DD-neutron spectrometers for studying $\rho $R, $\rho $R symmetry and yield at the NIF and OMEGA

R. LEEPER, SNL --- A new and very compact broadband spectrometer for DD neutrons is being tested for diagnosis of $\rho $R and $\rho $R symmetry of implosions at the NIF and OMEGA by measuring direct and down-scattered components at different positions around implosions involving D$^{3}$He or D$_{2}$ fuel. Based on CR-39 nuclear track detectors, C$_{2}$H$_{4}$ neutron-to-proton converters and filters, its 5-cm size enables simultaneous use of multiple modules at different angles. Directionality rejects a large fraction of neutrons scattered from the target chamber. Tests on the MIT linear accelerator provided initial calibration and demonstrated a dynamic range from $\sim $ 10$^{5}$--10$^{8}$ neutrons/cm$^{2}$, while NIF data provided a starting point for testing practical measurements. Results from initial experiments and simulations will be presented. This work was supported in part by the US DOE, LLE, and LLNL.