{HEAD ~ The resonators secondary and primary mirrors} are adjusted into a parallel orientation which gives a series of {TAIL ~ circles} in both laser beams 
{ HEAD ~ The resonators secondary and primary mirrors } are adjusted into a parallel orientation which gives a series of { TAIL ~ circles } in both laser beams
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH