xray, photomultiplier and laser tubes are still SOTA. PM tubes in particular have a huge number of glass feed through for the intermediate plate voltages.
xray, photomultiplier and laser tubes are still SOTA. PM tubes in particular have a huge number of glass feed through for the intermediate plate voltages.
Musical instrument amplifiers still use them as well, at least some of them.
Those are Not where the tubes are SOTA.