projecting a patterned beam of {HEAD ~ radiation} onto {TAIL ~ a substrate} held on the substrate table 
projecting a patterned beam of { HEAD ~ radiation } onto { TAIL ~ a substrate } held on the substrate table
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH