Williams-Kilburn tubes, which were CRTs with high-persistence phosphor used as memory and display devices beginning in the 1940s. The 'high-persistence' means W

Williams-Kilburn tubes, which were CRTs with high-persistence phosphor used as memory and display devices beginning in the 1940s. The 'high-persistence' means W-K tubes are the exact opposite of where CRT technology stands today: They're useless for TVs and computer monitors, because the phosphor stays lit too long. However, that's what you want if you're using the phosphor to store bits of data in a vacuum tube computer, or to display the contents of memory in that computer. Plenty of people are making CRTs today. I doubt anyone is making CRTs that would be useful W-K tubes. (Another guess might be core memory but, knowing NASA and some of IBM's customers, I have a suspicion someone still has real uses for a few hundred kilobytes of core.) [as originally posted by me elsewhere]