Domed-grid-cathode project phases 1 and 2

The feasibility of increasing the cathode area of a planar triode by use of spherical (domed grid-cathode) geometry was investigated. Early experiments conducted on a standard production planar triode with 2 sq cm cathode hinted at grid dissipation at least double those of standard planar triodes with no degradation of performance. Phase I of this project was set up to fully evaluate the performance of a standard production planar triode (Y730) refitted with a domed grid-cathode structure. If possible, a Y-690 was also to be fitted with the domed grid cathode structure for evaluation. Phase II of the project included design of a 3 sq cm domed grid cathode structure to fit within the Y-730 envelope. The geometry (spacing, grid mesh) from the Y-690 was also to be used. This structure was to be evaluated as to grid dissipation and performance. Progress is reported.