{HEAD ~ The beam} then passes through mode matching means 66 and finally through {TAIL ~ final amplifier stage} 82 
{ HEAD ~ The beam } then passes through mode matching means 66 and finally through { TAIL ~ final amplifier stage } 82
HEAD HEAD HEAD HEAD HEAD HEAD OTH REL OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH