Description
This ongoing study investigates the bremsstrahlung emission in high-temperature plasmas using molecular dynamics (MD) simulations. A wide range of plasma coupling and degeneracy regimes is investigated, with particular focus on temperatures, where relativistic phenomena become important. To accurately resolve the relativistic kinematics, we use a modified LAMMPS code [1] that includes velocity-dependent inertia and causally retarded long-range electromagnetic interactions. Short-range quantum effects are modeled using the improved Kelbg potential (IKP) and a Pauli repulsion potential based on the hyper-netted-chain (HNC) method. The standard bremsstrahlung coefficient formulation is adjusted with the relativistic Larmor formula. Our simulations at non-relativistic conditions and without the Pauli potential agree with the literature [2]. The bremsstrahlung spectrum decays at high frequencies and has a slightly reduced magnitude at low frequencies compared to the plasma frequency. Peaks in the emission spectra are introduced at strong coupling near the plasma frequency due to the formation of classical orbits by the attractive ion-electron interactions. Preliminary results suggest that Pauli repulsion attenuates these peaks due to enhanced electron-electron repulsions. At relativistic conditions, the contribution of the Pauli potential becomes less significant. Current simulations are underway to measure the emission spectra at relativistic temperatures.
[1] P. Svensson, Novel modelling techniques for charged many-body systems with quantum and relativistic effects, Ph.D. thesis, University of Oxford (2024).
[2] J. P. Kinney, H. J. LeFevre, C. C. Kuranz, S. D. Baalrud, Mean force emission theory for classical bremsstrahlung in electron–ion plasmas, Physics of Plasmas 32 (10) (2025) 103301.