ELECTROSTATIC El ELD IN VACUUM TUBES 



313 



0.05 0.10 0.(5 0.20 0.25 0.30 0.35 0.40 0.45 0.50 



DISTANCE ALONG CATHODE, X/3 



Fig. 5— Variation of transconductance along the cathode surface of a triode. 



ral2 



while, from (31), 



2K /""'' 

 ^^^ d^ 4 ^^^^^ "^ ^^^/^^ '^ ^ + d,/dd]"' dx (36) 



where .To is given by 



Vg + VJix{x,) = (37) 



On the basis of several reasonable assumptions it may be shown that both 

 (35) and (36) lead to an approximate 5/2 power law instead of 3/2 power 

 law. Such a law has actually been observed in cases where shadow forma- 

 tion was suspected. 

 We wish to express our appreciation to Messrs. R. K. Potter, J. A. Morton, 



