USE OF FIELD EMISSION ELECTRON MICROSCOPE 



919 



T = 2400"K V = 



1 MINUTE 



V=8900^ L=30xtA 



2/5 SECOND 



T= 1400° K 



L = 50 M 

 21 MINUTES 



8000 



V=7850^ 1=30 M.A 



2/5 SECOND 



1400" K L = 17/iA V = 8300 



1 MINUTE 



V= 8800 ^ L=30AtA 



2/% SECOND 



T=1400°K L=25^A 

 39 MINUTES 



V = 7900 



V=8050^ l=3QfiA 



2/5 SECOND 



T = 1400*'K 



8200 



V=8400^^ L = 30i«A 



2/5 SECOND 



T = 1430* K V = 

 3 MINUTES 



V = 8500 ^ L = 30>tiA 



2/5 SECOND 



Fig. 5 — Effect of high fields at 1400*K on size and shape of principal planes for clean W, 



