A specular layer is secured to {HEAD ~ the support} on {TAIL ~ the internal channel surface} to provide a relatively highly reflective surface over the region of the support facing the tube 
on
A specular layer is secured to { HEAD ~ the support } on { TAIL ~ the internal channel surface } to provide a relatively highly reflective surface over the region of the support facing the tube
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH