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