Hot spot velocity measurements using the deuterium-deuterium peak at the National Ignition Facility

The center-of-mass velocity of the fusing plasma in an Inertial Confinement Fusion (ICF) implosion can be determined from shifts in the first moment of the fusion neutron peak, measured by neutron time-of-flight (nToF) diagnostics. This “hot spot” velocity is correlated with ICF performance [1] and can provide insight into other aspects of implosion physics. At the National Ignition Facility Cherenkov-based detectors provide unprecedented precision in hot spot velocities derived from the deuterium-tritium (D-T) neutron peak, thereby uncovering unique features of burning plasma implosions. Here we present hot spot velocities determined from the deuterium-deuterium (D-D) neutron peak using scintillator measurements. The reduced velocity of D-D neutrons compared to D-T neutrons relaxes the diagnostic timing requirements and allows precision measurements to be made with scintillator-based nToFs. In addition to providing a consistency check of the D-T results, this data gives additional understanding of burning plasma ICF implosions.

[1] Schlossberg et al., RSI, 92(5), 1–5 (2021).