https://collaborate.princeton.edu/en/publications/the-attachment-length-in-orificed-hollow-cathodes/
The attachment length in orificed hollow cathodes - Princeton University
attachmentlengthhollowcathodesprinceton
https://collaborate.princeton.edu/en/publications/total-pressure-in-thermionic-orificed-hollow-cathodes-controlling/
Total pressure in thermionic orificed hollow cathodes: Controlling mechanisms and their relative...