MAGXETROS AS GENERATOR OF CEXTI METER \\A\ES 277 



Structure for the purpose of electrostatic shielding from electrons in the 

 interaction region. The frequency range required was spanned by the use 

 of anode structures having three different slot widths for the primary fre- 

 quency separation, small additional frequency shifts being obtained by small 

 distortions of the straps. Resonant frequencies of magnetron resonator 

 systems were now being determined prior to sealing for pumping by measure- 

 ments like those described in PART I, during which any necessary strap 

 adjustment could be made. 



The cathode was a plain, oxide coated, nickel cylinder much like that 

 used in the 700A-D magnetrons. The heater inductance was considerably 

 higher than that of any previous cathode assembly. It was found that 

 sudden and severe transient conditions, such as those imposed by a mo- 

 mentar}' internal arc between cathode and anode, would cause relatively 

 high voltages to develop between the cathode and the open end of the heater. 

 This could break down the heater insulation and cause either open or short 

 circuits. This difficulty was minimized by incorporating in the driving 

 equipment a condenser across the heater and an RF choke in series with 

 the heater. Before final design specifications were submitted, the input 

 leads and cathode structure were completely redesigned to provide greater 

 rigidity and strength. To withstand violent shock and vibration, the 

 structure was designed to have as high frequencies of mechanical resonance 

 as possible. The structure looked much like that to be seen in the 5J23 

 magnetron of Fig. 49. Direct mechanical injury to the input leads is pre- 

 vented by the use of a heavy glass housing. 



The output circuit in early experimental models was a coaxial type fed by a 

 loop in one of the resonators. The central conductor was a tungsten rod 

 to which the glass seal was made and to which the inner conductor of the 

 load coaxial was clamped. When the resonator system was redesigned for 

 lower voltage, a new design of output circuit was made in which was used a 

 choke or contact-free load coupling like that designed for the 720A-E. 

 This removed the possibility of stress being applied to the glass of the output 

 seal at either the inner or outer conductors. Except for the critical dimen- 

 sions determined by frequency, the output circuit is identical to that used 

 on the 5J23 shown in the photograph of the cut-away model of Fig. 49. 



In Fig. 47 is shown a schematic diagram of this type of coupling. On both 

 inner and outer conductors an electrical short circuit is produced at the gap 

 between magnetron and load coaxials by folded low impedance coaxial 

 sections incorporated into the bodies of the conductors. In the outer con- 

 ductor a half wavelength section folded once is employed. In the section 

 shown at (a), the joint is made at the current node in the choke section by 

 the outer of two cylinders which project from the load end of the coupler 



