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BELL SYSTEM TECHNICAL JOURNAL 



Since the screen element is in one piece there will be present two beams 

 out to it. One of these may be suppressed after it has passed through the 

 screen by the suppressor grids or by the anodes in the manner described below. 



These suppressor grids are generally operated at cathode potential or at 

 a potential that is negative with respect to the cathode. They may be used 

 for three purposes: to suppress secondaries from the anodes, to modulate 

 the beam current to their particular anode, and to suppress one of the two 

 beams. For the first of these functions they are biased at cathode potential. 

 For the second they are biased negatively and have a modulation curve simi- 

 lar to that of the suppressor grid in a pentode. Curve A of Fig. 6 shows the 

 variation of beam current to one anode when the potential of the suppressor 

 grid in front of it is varied. This curve is for a grid similar to the two paraxial 



SUPPRESSOR GRID 



CATHODE 



ELECTRON BEAM 



CONTROL GRID 



INDIVIDUAL ANODE 



Fig. 5. — Arrangement of elements in the tube shown in Figure 4. Only the operating 



beam is shown. 



wires in the tube shown in Fig. 5. For some applications a higher sup- 

 pressor-anode transconductance or a lower cut-off is desirable and these may 

 be obtained by welding lateral wires across this grid window to make the 

 grid action more efifective. Curve B of Fig. 6 was taken with the same size 

 window across which laterals were welded. The table below gives the data 

 for this suppressor grid with and without the lateral cross wires. 



Without Laterals With Laterals 



Transconductance (mho) 100 250 



Anode Resistance (ohms) 30,000 64,000 



Amphfication Factor 3.5 16.0 



Cut-Off Voltage -80 -20 



It is apparent from these data that amplification of the signals applied to 

 the individual suppressors may be readily obtained. 



