Systematic mode-1 asymmetry study based on the scattered neutron spectrum from cryogenic DT inertial confinement fusion implosions on OMEGA

A detailed understanding of the compressed fuel and low-mode asymmetry is essential to diagnose the performance of direct-drive cryogenic deuterium-tritium (DT) inertial confinement fusion (ICF) implosions. These metrics are inferred from the neutron energy spectrum from 3 to 7 MeV measured with high-resolution, high-dynamic range neutron time-of-flight (nTOF) diagnostics positioned along two nearly opposing lines of sight [1]. The shape of the spectrum influenced by the neutrons that elastically scatter off of D and T in the cold fuel is sensitive to the compressed areal density and mode-1 asymmetry [1]. A systematic study was conducted to determine experimental trends in the inferred asymmetry for a series of implosions on OMEGA. The results are compared to measured values of flow velocity and apparent ion temperature asymmetry diagnosed from nTOF detectors distributed around the target chamber, as well as to the 3D hot-spot reconstruction analysis from x-ray emission [2]. Preliminary results indicate a correlation between higher flow velocities and higher asymmetries. The results of the systematic mode-1 study will be presented.



[1] C. J. Forrest et al., Rev. Sci. Instrum. 93, 103505 (2022).

[2] K. Churnetski et al., Phys. Plasmas. 32, 052711 (2025).