The flood guns are located just outside the horizontal deflection plates. A cloud of electrons is emitted by each flood-gun cathode. These clouds are combined, shaped, and accelerated by the two control grids, as well as the collimator. The collimator consists of a coating on the inside of the tube. The positive voltage on the collimator is adjusted so the flood-gun electron cloud only fills the CRT viewing screen. The cloud is further accelerated towards the storage mesh and viewing screen by the collector mesh. After passing through the collector mesh, the flood electrons are further controlled by the potentials of the storage mesh and storage layer. The cathode side of the storage mesh is coated with the nonconductive storage material, which is where the pattern to be displayed is stored. Because of the nonconductive property, only a capacitive coupling exists between the storage layer and the storage mesh. This capacitive coupling is required for the storage and erase functions. The rest potential of the storage mesh is approximately + 1 V with respect to the flood-gun cathodes. In the write and erase routines, the potential of the storage layer varies from O V to negative. This is accomplished through the storage mesh and the capacitive coupling.
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