Testing an indirectly heated cathode ion source: Temperature and thermionic emission

Abstract

Here we compare the cathode surface temperatures and thermionic emissions of a novel thermal barrier cathode against original equipment manufacturing (OEM). The new indirectly heated cathode ion source assembly employs a cathode cup unit and filament arrangement, where the filament has a flat face that is separated from the cup-shaped cathode body. The filament is placed in a space that is surrounded by a thermal barrier to reduce thermal losses. The thermal barrier is formed by a plurality of concentric foils that are closely spaced. We observed an improvement on the cathode surface temperature and thermionic emission relative to OEM. The addition of the thermal barrier in combination with the large cathode surface area increased the thermionic emission.