# Performance of Miniature Carbon Nanotube Field Emission Pressure Sensor for X-Ray Source Applications

## TL;DR

A new miniature sensor using carbon nanotubes effectively measures vacuum conditions in sealed devices like X-ray tubes, offering advantages like low power and stability.

## Contribution

A novel miniature carbon nanotube sensor is developed for in situ vacuum monitoring in sealed devices with low power consumption and high stability.

## Key findings

- The MWCNT sensor performs well for nitrogen, hydrogen, and air mixtures in the 10−7 to 10−3 Pa range.
- The sensor remains stable under high-temperature baking and long-term storage over two years.
- Pre-sealing degassing treatments enable X-ray tubes to maintain high vacuum levels with minimal outgassing.

## Abstract

There is a lack of an effective approach to measure vacuum conditions inside sealed vacuum electronic devices (VEDs) and other small-space vacuum instruments. In this study, the application performance of an innovative low-pressure gas sensor based on the emission enhancements of multi-walled carbon nanotube (MWCNT) field emitters was investigated, and the in situ vacuum performance of X-ray tubes was studied for the advantages of miniature dimension and having low power consumption, extremely low outgassing, and low thermal disturbance compared to conventional ionization gauges. The MWCNT emitters with high crystallinity presented good pressure sensing performance for nitrogen, hydrogen, and an air mixture in the range of 10−7 to 10−3 Pa. The miniature MWCNT sensor is able to work and remain stable with high-temperature baking, important for VED applications. The sensor monitored the in situ pressures of the sealed X-ray tubes successfully with high-power operations and a long-term storage of over two years. The investigation showed that the vacuum of the sealed X-ray tube is typical at a low 10−4 Pa level, and pre-sealing degassing treatments are able to make the X-ray tube work under high vacuum levels with less outgassing and keep a stable high vacuum for a long period of time.