Validation of energy coupling models using time-resolved scattered light data in polar direct drive experiments on the NIF*

Time resolved scattered light data from polar direct drive (PDD)[1] experiments on the National Ignition Facility (NIF) using 2.1-mm diameter solid CH sphere targets have been analyzed to validate laser energy-to-target coupling models in 2-D radiation hydrodynamic simulations. Fourteen scattered light time history diagnostic (SLTD)[2] units and eight full aperture backscatter stations (FABS) are used to measure the time resolved scattered light in a narrow band around the incident laser wavelength of 351 nm. The measured scattered light intensity has been compared with data from the 2-D radiation hydrodynamic code DRACO, which includes the effects of cross beam energy transfer (CBET). DRACO overpredicts scattered light at early times. [WT1] At later times the scattered light predictions compared to experimental data to reveal trends that depend on pulse shape features[WT2] . These trends will be discussed further to tune DRACO in validating CBET models. The evaluation of time resolved scattered light and future development of 2D scattered light map reconstruction will be discussed.

 

 

[1] M. Hohenberger et al., Phys. Plasmas 22, 056308 (2015).

[2] M. J. Rosenberg et al., Rev. Sci. Instrum. 92, 033511 (2021)