Particle-in-cell simulations of laser-plasma instabilities: creation of a dataset for training a deep-learning-based LPI surrogate for ICF

For the success of inertial confinement fusion (ICF) [1], it is crucial to understand some of laser-plasma instabilities (LPIs) [2] effects, particularly  i) scattered light, and ii)  features of suprathermal electrons. However, LPI complexity obscures experimental characterisation and mathematical understanding of those processes. In addition, the LPI kinetic nature makes them incompatible to be fully included in ICF hydrodynamics codes. Then, in hydrocodes,  LPI effects are simplified using scaling laws based on a few experimental and/or simulations results due to limited resources [3], constraining the hydrocodes accuracy, especially at ignition conditions.

 LPIs models can benefit from deep learning methods. Recently, an efficient deep neural network called Deep Emulator Network Search (DENSE) has shown impressive results even with a small amount of data sampling in modelling physical phenomena [4]. We apply this methodology to the creation of an LPIs emulator containing all the relevant information to couple LPI effects to laser ray tracing and plasma hydrodynamics. 

Here we present  LPIs one-dimensional particle-in-cell simulations which constitute the training dataset for the LPIs emulator. Laser and plasma conditions span from sub-scale to ignition-scale: the interval of the plasma density scale lengths considered is L = 100 -700 μm, whereas the laser intensities range from I = 0.02 to I = 10 x10¹⁵ W/cm². We characterise the back-scattered light and hot-electron generated, showing how LPIs behaviour varies when plasma and laser parameters approach ignition conditions, i.e. large plasmas and high laser intensities. Finally, we show the DENSE LPI surrogate results and compare them with PIC simulations to benchmark its accuracy.

References

[1] J.D.Lindl, “Inertial Confinement Fusion”,AIP-Press(1998).

[2] W.Kruer, “The Physics Of Laser Plasma Interactions",CRC Press(2003).

[3] A.Colaitis, et al.,PhysicalReviewE92(4),041101

[4] M.F.Kasim, et al.,arXiv:2001.08055v2