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