Field-emission X-ray sources with an anisotropic focusing lens for isotropic X-ray focal spots

Hermetic-sealed field-emission X-ray sources with an anode voltage and current of 70 kV and 0.5 mA have been developed using an anisotropic focusing electron lens structure for an isotropic focal spot. The anisotropic focusing of an electron beam was achieved using an electrostatic electron lens with anisotropic aperture geometry integrated in a gate (or grid) electrode. The anisotropic geometry has an influence on the electron beam with different horizontal and vertical electric fields, thereby anisotropically focusing the beam on an anode target.