A scraper mirror reflects the beams to a thermal imager which reflects the beams to {HEAD ~ a pair} of {TAIL ~ NaCl beamsplitters} 
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A scraper mirror reflects the beams to a thermal imager which reflects the beams to { HEAD ~ a pair } of { TAIL ~ NaCl beamsplitters }
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