Study of Rhenium as an Alternate Substrate Material for Impregnated Dispenser Cathodes

摘要

Rhenium powder with an average particle size of 6.8 microns was used to develop the fabrication techniques of rhenium cathodes. Pressing pressures, sintering temperatures, and sintering times were the parameters of concern. The possibility of machining unlubricated, impregnated cathodes was also tested. Electron microscopy, nitrogen permeability, and metallography methods were used to characterize the various matrices and compare them to tungsten matrices. Cathodes impregnated with 5:3:2 or 4:1:1 barium-calcium-aluminate were tested for emission performance and compared to tungsten cathodes. A guard ring structure was installed around the cathode to suppress edge effects. Results indicated that rhenium can be fabricated into a working cathode. Fabrication techniques are not completed, and optimization methods need to be studied. Results from emission testing showed 4:1:1 to be the impregnant of choice for a rhenium matrix due to little or no emission from a 5:3:2 impregnated cathode. Testing also proved that activation procedures must be altered according to the metal used. Recommendations for methods of emission enhancement and future studies were made.