Two electrodes {TAIL ~ each} having {HEAD ~ an electrode tip} at a mutual distance EA are arranged inside the discharge vessel 
Two electrodes { TAIL ~ each } having { HEAD ~ an electrode tip } at a mutual distance EA are arranged inside the discharge vessel
OTH OTH TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH