A Pencil Beam Electron-Optical System for Teahertz Vacuum Electronic Devices

The simulation of a terahertz pencil beam electron-optical system (EOS), comprising an electron gun and a uniform magnetic focusing system with operating voltage of 18–20 kV and current of 14-16.5 mA, is reported. The beam current density exceeds 360 A/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> due to the miniature radius of beam as 35 μm and tunnel as 50 μm, while the cathode surface current density below 3 A/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>. Therefore, the magnetic system provides a peak magnetic field strength of approximately 0.6 T to ensure stable transmission over distances exceeding 30mm with transmission efficiency of 100%.