RADIAL BEAM VACUUM TUBE 



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arrangement of the elements. Closely surrounding the cathode is a control 

 grid that may be used for modulating the current density of the electron 

 beams. Farther out is a cylindrical element with 30 windows that is main- 

 tained positive and which by virtue of its similarity in position to the third 

 element of a tetrode is called a screen. Immediately behind each window 

 there is a pair of paraxial wires which because of its similarity in function 

 to the fourth element of a pentode is called a suppressor grid. In back of 

 each suppressor grid there is an anode. In this particular tube there are pro- 



Fig. 4. — Radial beam tube with 30 anodes and unwound stator used with it. 



jections like gear teeth on the back of the screen clement to prevent electrons, 

 destined for one anode, from reaching an adjacent one. 



The control grid that is close to the cathode is biased negatively and con- 

 trols the electron current in the same way that it would if the magnetic field 

 were not present. The space current vs. grid potential curve is nearly 

 identical for the two cases: with and without the magnetic field. The 

 slight difference is due to the fact that the presence of the magnetic field 

 increases the space charge near the cathode. Thus the tube may be used for 

 amplification in the usual way when the electrons are focused. The pres- 

 ence of this grid has no appreciable effect on the focusing of the electrons. 



