Effect of Mode-1 Perturbations on OMEGA Areal-Density Measurements

Implosion areal density (ρR) is an important measurement to assess the performance of cryogenic implosions. The presence of a mode-1 (l = 1) perturbation compromises this measurement. The statistical model[1] used to design the high-performance cryogenic implosions on OMEGA have shown that the ion-temperature distribution is a good indication of the presence of a mode-1 asymmetry. Energy shifts in the neutron peak energies are used to measure the velocity of the fusing plasma,[2] also an indicator of a mode‑1 asymmetry. Data that utilize these two mode-1 signatures will be compared to the implosion ρR measurements using two backscatter signatures, neutron time of flight (nToF) and a downscatter signature (magnetic recoil spectrometer). An outstanding question is whether or not the high ρR values from early cryogenic implosions[3] have been affected by mode-1 asymmetries. The earlier experiments did not have the mode-1 asymmetry measurements of the recent implosions. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856.

 

[1] V. Gopalaswamy et al., Nature 565, 581 (2019).

[2] .O. M. Mannion et al., Nucl. Instrum. Methods Phys. Res. A 964, 163774 (2020).

[3] S. P. Regan et al., Phys. Rev. Lett. 117, 025001 (2016).