a sensor for detecting a at least one of a secondary electron and reflected electron emanated from the object, upon exposure of {HEAD ~ the object} to {TAIL ~ the electron beam} 
to
a sensor for detecting a at least one of a secondary electron and reflected electron emanated from the object , upon exposure of { HEAD ~ the object } to { TAIL ~ the electron beam }
OTH OTH OTH OTH OTH OTH OTH OTH 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 TAIL