The DT to DD yield ratio as a diagnostic of implosion dynamics for NIF ICF experiments.*

The variation of the yield ratio Y_DT/Y_DD for implosions of cryogenically layered deuterium and tritium (DT) fueled capsules  exceeds the  expectation based on measurement statistical uncertainties and fuel isotopic concentration [M. Gatu-Johnson, et al.,  Phys. Plasmas, 20 (2013) 042707]. Variations in the line-of-sight diagnostics depend on both the attenuation of the "birth spectrum" of the neutrons through the compressed, cold fuel and the burn-averaged moments of the fuel velocity distributions [D. H. Munro,  Nucl. Fusion, 56 (2016) 036001]. An analysis of the variability of the yield ratio for recent implosions sets limits on the size of the velocity contributions. These limits are compared to expectations from 2D and 3D simulation ensembles of similar implosions.