MAGNETRON AS GENERATOR OF CENTIMETER WAVES 347 



The next step in the development was the replacement of the nickel mesh 

 by a sintered matrix of coarse nickel powder (see Fig. 79). The average 

 particle size was 55 microns. The active material is packed into this 

 matrix in much the same manner as in the mesh cathode. Little difference 

 was observed in the addition of fine nickel powder to the Active coating in 

 this type of cathode. The matrix cathode has the best life characteristic 

 of any yet devised for the magnetron oscillator. Its life characteristic is 

 shown in Fig. 80 with those of the earlier types. 



The sintered matrix type of cathode has been used extensively in the 

 4J50 and 4J52 magnetrons at 3 cm. and in the 3J21 magnetron at 1 cm. 

 In these cathodes, it was important to have high heat dissipation. This 

 was achieved by designing a high thermal conductivity support and pro- 

 viding considerable radiating area immediately adjacent to the cathode 

 surface by extending the cathode, as shown in Figs. 75 and 77, into the pole 

 piece opposite that carr}'ing the cathode mount. 



22. Acknowledgments 



During the war, the interchange of ideas and results among authorized 

 persons concerned with magnetrons has been rapid and effective. Be- 

 cause of this it would be difficult to trace the origins of much of the general 

 material presented in PART I and no attempt has been made to do so. 

 It must be clear that the results reported have involved the efforts of many 

 people. In the Bell Laboratories, the authors were members of a group 

 which, as the work progressed, grew to a considerable size. In the early 

 stages they were joined by G. E. Moore and W. B. Hebenstreit, later by 

 N. Wax, L. M. Field, A. T. Nordsieck, and R. D. Fracassi. Other mem- 

 bers of the Technical Staff in the magnetron group were A. J. Ahearn, 

 H. W. Allison, B. B. Gaboon, G. J. Galbick, M. S. Glass, R. K. Hansen, J. G. 

 Potter, R. Rudin, H. G. Wehe, A. E. Whitcomb, and C. M. Witcher, as well 

 as several technical assistants. 



The XDRC Radiation Laboratories at the Massachusetts Institute of 

 Technology- and at Golumbia University generously supplied personnel for 

 several cooperative projects and information on new results. In the 725A 

 development, A. T. Nordsieck, then of Columbia, took part. L. R. Walker 

 of M. I. T. contributed not only to the development of the 725A but took 

 part in the development of the 4J50, 4J52, and 4J78. Other M. I. T. Staff 

 Members in residence from time to time were F. Hutchinson, E. Everhart, 

 and D. B. Bowen. The developments of the 2J51 and the 3J21 were 

 effected jointly with the Columbia Laboratory. 



Prof. J. C. Slater, first as a member of the M. I. T. Radiation Laboratory 

 and later as a member of the Bell Laboratories, made numerous studies in 

 our Laboratories and consulted generally on magnetron problems. 



