Development of a High-Beam-Transparency Gridded Electron Gun Based on a Carbon Nanotube Cold Cathode

We here report on the development of an improved dual-gridded electron gun based on a carbon nanotube cold cathode that enhances electron beam transparency and reduces grid interception and loss pathways. Compared with microscale tip Spindts, the dual-gridded construction decreases challenges associated with nanomaterial growth, fabrication, and assembly. Our experimental findings show that this dual-gridded CNT electron gun can support anode output currents (cathode emission current) of up to 700 mA, with a beam-transparency of up to ~100% and a compression ratio of 1/19. A beam spot of uniform brightness is obtained and the radius of the beam spot is 1.5 mm. In addition, our studies show that the device can operate at 1/100 duty cycle continuous pulse with a stable current of around 100mA over 100 h.

I. Introduction

Electron-optical systems are a core technology within almost every vacuum electron radiation source (VERS), though their design and effective integration remains challenging [1]–[5]. Carbon nanotubes (CNTs) have been proven to function as a near ideal field electron emission (FE) cold cathode source [6]–[8] due to their room-temperature operation, instantaneous switch-on, ability to support large emission current densities, ease of nanoscale self-assembly, and ever decreasing and increasingly competitive production costs [9]–[16]. However, several integration challenges continue to restrict the development of carbon nanotube (CNT) cold cathode VERS, such as the effective and scalable integration of CNT based electron emitters into macroscopic devices [17]–[19].