The discharge vessel encloses {HEAD ~ a discharge space} having an ionizable filling which, in addition to Hg, contains a quantity of iodide of {TAIL ~ Na}, Tl, Ho and Ca 
The discharge vessel encloses { HEAD ~ a discharge space } having an ionizable filling which , in addition to Hg , contains a quantity of iodide of { TAIL ~ Na } , Tl , Ho and Ca
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH