Multiple Boris integrators for particle-in-cell simulation

We construct Boris-type schemes for integrating the motion of charged particles in particle-in-cell (PIC) simulation. The new solvers virtually combine the 2-step Boris procedure arbitrary n times in the Lorentz-force part, and therefore we call them the multiple Boris solvers. Using Chebyshev polynomials, a one-step form of the new solvers is provided. The new solvers give n^2 times smaller errors, allow larger timesteps, and have a long-term stability. We present numerical tests of the new solvers, in comparison with other particle integrators.