means for directing {TAIL ~ substantially collimated source} supplied {HEAD ~ radiation} toward the second focusing reflector in the reflectance mode; and 
means for directing { TAIL ~ substantially collimated source } supplied { HEAD ~ radiation } toward the second focusing reflector in the reflectance mode ; and
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH