Particle acceleration by wave scattering off dielectric spheres at whispering-gallery-mode resonance

The large electromagnetic fields, created in wave scattering near a perfect dielectric sphere at the condition of whispering-gallery-mode resonances, are investigated as driving units for high energy charged particle accelerators. For optimal trajectories passing near the scattering sphere, particle coupling with the field reduces to very short intervals, of the order of the wave period. Interacting fields can be almost 1000 times stronger than that in the incident wave. An example considered indicates that the instantaneous energy yield during this strong coupling interval is equivalent to ∼30  GeV/m, assuming the incident electric field E₀=100  MV/m. It was shown that the particle transverse deflection is negligible if the phase of the particle is optimal for acceleration. Hence, the acceleration process can be repeated many times. A rough estimate of the energy gain in a periodic chain of such elementary accelerating unit cells gives ΔEnergy/m≈5  GeV/m, which is several hundred times more than in contemporary operating and projected accelerators. Preliminary estimates of absorption losses in the scheme are given.