Plasma Hollow Cathodes

Hollow cathode plasma discharges are a fundamental part of a large variety of applications in industry, academia, and space. From surface processing and coatings deposition to plasma-surface interaction research and electric propulsion, advances in hollow cathode modeling and performance are critically important to the progress and evolution of these and other areas of technology. This paper describes perspectives on the progress that has been made in recent years in the capabilities and modeling of hollow cathodes used in plasma discharges. While many of the developments have been driven by the demanding requirements of electric propulsion applications, the information provided applies to all thermionic hollow cathodes and their applications. In the paper, we describe the status of 2D global simulations of hollow cathode plasmas, hollow cathode plume instabilities, and the development of higher current cathodes and low-current heaterless cathode technologies. Advances in our understanding and technology in these areas and some of the challenges that still need to be addressed and solved are discussed.