CATHODE SPUTTERING 



289 



having all high tension leads and terminals enclosed in an expanded 

 metal cage. The door operates a switch in the primary circuit, so that 

 as the door is opened, the circuit is broken. 



In order that equal amounts of metal might be evenly deposited on 

 each of the si.x diaphragms, it was necessary to determine experimen- 

 tally the relative spacing of the electrodes, and the shape and the size 



Fig. 5 — Detailed construction of the bleeder valve. 



of the shields, stands, and bell jar which would give a uniform current 

 distribution. The best results were obtained by placing the dia- 

 phragms 5y8" from the cathodes, which are arranged symmetrically, 

 by maintaining the pressure at .10 ± .05 mm., by having a 1/2" hole 

 in the center of the diaphragm holder and shield, and a one inch clear- 

 ance between their outer rims and the bell jar. 



