Field ionization intensity used to measure local pressure in gas flows

Authors : F. Sharipov, I. Martin-Graur, E. Salançon

Published: January 2025 in Vacuum (235):

https://www.sciencedirect.com/science/article/pii/S0042207X24007747

The coaxial ion source studied at CINaM generates an ion beam through field ionization in a gas flow. Ionization occurs at the tip of a nanoscale needle emerging from a coaxial microchannel situated between a high-pressure chamber and the ion propagation chamber. Experimental work conducted by Djouher Bedrane during her PhD (2023) demonstrated an ionization intensity 300 times greater than that achieved without this structure, under identical pressure conditions in the propagation chamber.

This increased intensity is attributed to a high local pressure at the needle tip, a value confirmed by theoretical models developed in collaboration with two specialists in rarefied flow dynamics. These findings validate the use of a field ionization tip as a local pressure sensor, with spatial resolution defined by the positioning and size of the needle tip.

This research opens two major avenues in instrumentation:

– A field ionization tip can serve as a precise and localized pressure sensor.

– The position of the tip can be adjusted to maximize the intensity of the ion source currently under development, in a PhD project in partnership with Orsay Physics, for applications in focused ion beam (FIB) technology.