Because {HEAD ~ the vacuum pump} 12 creates {TAIL ~ a vacuum} inside the light source chamber 10, X rays generated and propagating inside the chamber are not attenuated 
Because { HEAD ~ the vacuum pump } 12 creates { TAIL ~ a vacuum } inside the light source chamber 10 , X rays generated and propagating inside the chamber are not attenuated
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH