The mass flow controllers 94 and 96 control {HEAD ~ the flow rates} of {TAIL ~ the boron} trichloride 
of
The mass flow controllers 94 and 96 control { HEAD ~ the flow rates } of { TAIL ~ the boron } trichloride
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH