The coolest coax cable is the YK-217 cable. 14.8 ohm impedance. 25kv. The center conductor was a 6mm plastic rod. Then came the braided inner conductor, covered with some very thin black plastic shit. Then some serious HV insulation, followed by the outer conductor and a thick outer protective jacket. The cable was about 16mm in outside diameter. I had to strip 100 of these cables, with the inner conductor extending about 35mm from the outer conductor. The only way to do this accurately was on a lathe. In my youth, I spent all afternoon and evening doing this, then went to a concert at Winterland in San Francisco. From these cables, and a ton of other machining and one large 50nF capacitor, I built a nitrogen laser reliable enough to use in my thesis experiment. Every once in a while, a cable would short, always where my lathe knife had gone a tad too deep. As the laser pulsed at 17Hz, it sounded like a machine gun when this happened. I stopped the laser, used my grounding hook to discharge everything, and calmly unclamped the offending cable and threw it away. The laser ran perfectly well with 99, 98,97… cables. That’s why I used cables.