Vacuum tube and vacuum tube manufacturing apparatus and method

A vacuum tube having a reduced-pressure vessel comprising:

• at least a discharge gas sealed for electric discharge,
• wherein:
• the sum total of the number of organic gas molecules, the number of water molecules, and the number of oxygen molecules all of which remain inside a space of said reduced-pressure vessel is smaller than the number of molecules of said discharge gas,
• the number of water molecules which is adsorbed on an inner wall of said reduced-pressure vessel is not greater than 1×1016 molecules/cm2,
• a ratio of said number of molecules of said discharge gas to the sum total of said number of organic gas molecules and said number of water molecules is not smaller than ten times, and
• the reduced-pressure vessel is a component of a device selected from the group consisting of:
• a vacuum tube, a fluorescent tube, a cold cathode tube, a deuterium discharge tube, an electron beam tube, an X-ray generating tube, an ultraviolet generator, and a static electricity neutralizer.