{HEAD ~ Temperature sensors}, such as {TAIL ~ pyrometers}, that do not contact the wafers being preheated, measure temperature for control of the heating of the lamps 
such as
{ HEAD ~ Temperature sensors } , such as { TAIL ~ pyrometers } , that do not contact the wafers being preheated , measure temperature for control of the heating of the lamps
HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH