How does a "CRT storage tube" work?

Part of the answer is “based upon the secondary emission of electrons from the phosphor screen itself” from a related link.
Regular CRTs drain the electron beam current off quickly so after illuminating phosphors a high energy electron from the beam settles down and flows out the drain wire.
In the storage tube the drain current is shut off while the electrons energize the phosphors and the phosphors themselves energize their neighbors back and forth within localized area where the pattern was drawn by the electrons.