The Landau form of the Fokker-Planck equation is the gold standard for plasmas dominated by small angle collisions, however its $Order{N^2}$ work complexity has limited its practicality. This paper extends previous work on a fully conservative finite element method for this Landau collision operator with adaptive mesh refinement, optimized for vector machines, by porting the algorithm to the Cuda programming model with implementations in Cuda and Kokkos, and by reporting results within a Vlasov-Maxwell-Landau model of a plasma thermal quench. With new optimizations of the Landau kernel and ports of this kernel, the sparse matrix assembly and algebraic solver to Cuda, the cost of a well resolved Landau collision time advance is shown to be practical for kinetic plasma applications. This fully implicit Landau time integrator and the plasma quench model is available in the PETSc (Portable, Extensible, Toolkit for Scientific computing) numerical library.
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