A 580-MW peak power, radially polarized C${\mathrm{O}}_2$ laser beam ($\lambda =10.6\mathrm{}$ μm) focused by an axicon accelerated 40-MeV electrons by ≤3.7 MeV over a 12-cm interaction length (31 MeV/m), using the inverse Cherenkov effect in which a gas is used to slow the light wave. This represents the first direct observation of acceleration using this effect and demonstrates the effectiveness of the radially-polarized-axicon-focused geometry. The observed energy gain agrees with model predictions.

• Received 23 May 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.546