An X ray generator includes a cathode having an emitter made of {HEAD ~ carbon nanotubes} which emits electrons by field emission and thus becomes {TAIL ~ a cold cathode electron emission source} 
becomes
An X ray generator includes a cathode having an emitter made of { HEAD ~ carbon nanotubes } which emits electrons by field emission and thus becomes { TAIL ~ a cold cathode electron emission source }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL