{HEAD ~ a first focusing reflector} which directs {TAIL ~ source} provided radiation to the sample in the transmission mode 
directs
{ HEAD ~ a first focusing reflector } which directs { TAIL ~ source } provided radiation to the sample in the transmission mode
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH