Compact, low power radio frequency cavity for femtosecond electron microscopy

Reported here is the design, construction, and characterization of a small, power efficient, tunable dielectric filled cavity for the creation of femtosecond electron bunches in an existing electron microscope without the mandatory use of femtosecond lasers. A 3 GHz pillbox cavity operating in the TM110 mode was specially designed for chopping the beam of a 30 keV scanning electron microscope. The dielectric material used is ZrTiO4, chosen for the high relative permittivity (¿r = 37 at 10 GHz) and low loss tangent (tan d = 2 × 10-4). This allows the cavity radius to be reduced by a factor of six, while the power consumption is reduced by an order of magnitude compared to a vacuum pillbox cavity. These features make this cavity ideal as a module for existing electron microscopes, and an alternative to femtosecond laser systems integrated with electron microscopes