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