A third vacuum pump, connected to the processing chamber, is operated when {HEAD ~ the vacuum} in {TAIL ~ the processing chamber} reaches a predetermined value 
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A third vacuum pump , connected to the processing chamber , is operated when { HEAD ~ the vacuum } in { TAIL ~ the processing chamber } reaches a predetermined value
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH