CATUODR SPUTTERING 



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all of each diaphragm except a central circular spot about 3/4" in 

 diameter. A vacuum is produced by means of a Megavac pump con- 

 nected to the bell jar by 5/8" pyrex glass tubing, which is made as 

 short as possible to facilitate rapid pumping. In the vacuum system 

 are a small rotating McLeod gauge, a trap, a bleeder valve, and an 

 anode. The anode consists of a 20-turn, 1/2" helix of No. 14 aluminum 



VACUUM GAUGE 



BLEEDER VALVE 

 KEEPING VACUUM 

 AT .lOOMM PRESSURE 



Fig. 3 — A complete sputtering unit. 



wire sealed into a one-inch tube at some distance from the bell jar. 

 The end of the helix is shielded against high current density by a 

 flanged piece of glass tubing. This type of anode has a life of at least 

 two thousand hours. 



In order to maintain a constant residual gas pressure, the pump is 

 operated continuously and air is allowed to leak in slowly through the 



