The field reversed configuration (FRC), such as studied in the C-2W experiment at TAE Technologies, is an attractive candidate for realizing a nuclear fusion reactor. In an FRC, kinetic ion effects play the majority role in macroscopic stability, which allows global stability studies to make use of fluid-kinetic hybrid (also referred to as Ohm's law) models wherein ions are treated kinetically while electrons are treated as a fluid. The development and validation of such a hybrid particle-in-cell algorithm in the Exascale Computing Project code WarpX are reported here. Implementation of this model in the WarpX framework benefits from the numerical efficiency of WarpX as well as its scalability on large HPC systems and portability to different architectures. Performance benchmarks of the new algorithm for large, 3-dimensional, full device simulations from the Perlmutter supercomputer are presented. Results of a series of FRC simulations are discussed in which the impact of two-fluid effects on the tilt-mode growth rate was studied. It was observed that, in agreement with previous Hall-MHD studies, two-fluid effects have a stabilizing impact on the tilt mode.

We introduce a concept of laser-generated neutrons to transmute transuranic elements separated from spent nuclear fuel (SNF) and dissolved in a molten salt to form a subcritical core whose liquid state allows and facilitates safety, laser irradiation, and monitoring of chemical and physical properties. In this transmutation concept (the transmutator), the neutrons are generated via beam-target fusion whereas the beam is created by laser irradiation of nanometric foils through the Coherent Acceleration of Ions by Laser (CAIL) process. This relatively low deuteron energy is catapulted by fusion and eventually by secondary fission processes. The combination of the use of molten salt and laser allows us to introduce rapid feedback control of the system’s operation. The transmutator is an integral part of the partitioning and transmutation concept whereby the radiotoxicity of SNF is significantly reduced together with the required storage duration and volume. To enable this transmutator, we introduce integrated ideas and processes in the areas of lasers, neutronics, first-wall material, and chemistry.

Plasma flow and acceleration in a magnetic mirror configuration are studied using a drift-kinetic particles-in-cell model in the paraxial approximation, with an emphasis on finite temperature effects and energy transport. Energy conversion between electrons and ions, overall energy balance, and axial energy losses are investigated. The simulations of plasma flow, acceleration, and energy transport in the magnetic mirror are extended into the high-density regimes with implicit particle-in-cell simulations. It is shown that profiles of the anisotropic ion temperatures and heat fluxes obtained with the full drift-kinetic model compare favorably with the results of a fluid model, which includes collisionless ion heat fluxes beyond the two-pressure adiabatic equations. The effects of collisions on trapped electrons and the resulting impacts on electron temperature and electric field profiles are investigated using a model collision operator.

Simulations of photoneutron generation are presented for the anticipated experimental campaign at ELI-ALPS using the under-commissioning e-SYLOS beamline. Photoneutron generation is a three-step process starting with the creation of a relativistic electron beam which is converted to gamma radiation, which in turn generates neutrons via the $\left(\gamma ,n\right)$ interaction in high-Z material. Electrons are accelerated to relativistic energies using the laser wakefield acceleration (LWFA) mechanism. The LWFA process is simulated with a three-dimensional particle in cell code to generate an electron bunch of 100s pC charge from a 100 mJ, 9 fs laser interaction with a helium gas jet target. The resultant electron spectrum is transported through a lead sphere with the Monte Carlo N-Particle (MCNP) code to convert electrons to gammas and gammas to neutrons in a single simulation. A neutron yield of $3\times {10}^7$ per shot over $4\pi$ is achieved, with a corresponding neutron yield per kW of $6\times {10}^{11}$ n/s/kW. The paper concludes with a discussion on the attractiveness of LWFA-driven photoneutron generation on high impact, and societal applications.