{HEAD ~ vacuum} means enclosing {TAIL ~ at least the chip} and said luminescent target means  
enclosing
{ HEAD ~ vacuum } means enclosing { TAIL ~ at least the chip } and said luminescent target means
HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH