1. APPARATUS FOR TREATING A CATHODE RAY TUBE TO REDUCE THE TENDENCY FOR ARCHING AMONG THE PARTS THEREOF, THE TUBE HAVING A NECK PORTION AND AN ELECTRON GUN STRUCTURE MOUNTED THEREIN, THE GUN STRUCTURE HAVING ANODE ELECTRODE MEANS TO BE ESTABLISHED AT A HIGH VOLTAGE ANODE POTENTIAL DURING OPERATION OF THE TUBE, AND GRID ELECTRODE MEANS CONNECTED TO CONDUCTOR MEANS PROTRUDING EXTERIORLY OF THE NECK PORTION, A CONDUCTIVE COATING ON THE INNER SURFACE OF THE NECK PORTION TERMINATING AT A SELECTED POINT THEREIN AND ELECTRICALLY CONNECTED TO SAID ANODE ELECTRODE MEANS, SAID APPARATUS INCLUDING IN COMBINATION; A SLEEVE OF INSULATING MATERIAL, AN ANNULAR INTERIOR MEMBER COMPOSED OF RESILIENT INSULATING MATERIAL HAVING AN INNER DIAMETER LESS THAN THE OUTER DIAMETER OF THE NECK PORTION OF THE TUBE AND SECURED WITHIN SAID SLEEVE, SAID SLEEVE AND SAID INTERIOR MEMBER BEING ADAPTED TO BE SLIPPED OVER THE OUTSIDE OF THE NECK PORTION WITH THE INTERIOR MEMBER BEING FURTHER ADAPTED TO ENGAGE THE NECK AND HOLD THE SLEEVE THEREON, AND MEANS FOR APPLYING AN ARC PRODUCING POTENTIAL SUBSTANTIALLY IN EXCESS OF SAID HIGH VOLTAGE ANODE POTENTIAL TO SAID ANODE ELECTRODE MEANS WITH RESPECT TO SAID GRID ELECTRODE MEANS FOR CAUSING DESTRUCTION OF FOREIGN PARTICLES AND CONSTRUCTIONAL IMPERFECTIONS ON SAID ELECTRON GUN STRUCTURE, THE ARC PRODUCING POTENTIAL BEING SUFFICIENTLY HIGH TO PRESENT THE POSSIBILITY OF ARCING BETWEEN THE CONDUCTIVE COATING AND THE CONDUCTOR MEANS THEREBY SUBJECTING THE TUBE TO DAMAGE, SAID SLEEVE HAVING LENGTH SUBSTANTIALLY AS LONG AS THE DISTANCE BETWEEN THE POINT WHERE THE CONDUCTIVE COATING TERMINATES AND THE END OF THE NECK PORTION WHEREBY THE CONDUCTOR MEANS PROTUDES, WHEREBY ARC-OVER BETWEEN THE CONDUCTOR MEANS AND THE CONDUCTIVE COATING EXTERIORLY OF THE TUBE IS PREVENTED.