DESIGN FACTORS OF THE 1553 TRIODE 



501 



Fig. 3. This perspective sketch has been made much out of scale so that 

 the very close spacings and small parts would be seen. The nickel core of 

 the cathode is mounted in a ring of low-loss ceramic in such a manner 

 that the nickel and ceramic surfaces may be precision ground flat and 

 coplanar. A thin, smooth oxide coating is applied to the upper surface of 



Fig. 1. — The B.T.L. 1553 microwave triode with a cross-section drawing of it in the 

 background. 



the cathode by an automatic spray machine developed especially for this 

 tube. With this machine, a coating of 0.0005" zb 0.00002" may be put on 

 under controlled and specifiable conditions. To insure long life with such 

 a thin coating, it was necessary to develop coatings from two to four 

 times as dense as those used in existing commercial practice. 



The grid wires are wound around a flat, polished molybdenum frame 



