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