Effect of gap length on effective field strength

A micro-channel plate (MCP) was used to measure the minute emission current within the range of 1*10/sup -19/ A to 1*10/sup -14/ A in a high vacuum (1.3*10/sup -5/ Pa). By a Fowler-Nordheim plot, it is found that the effective field strength for initial electron emission is mostly constant between 10/sup 7/ and 10/sup 8/ V/cm under any gap length. The effective field strength is held constant between 10/sup 7/ and 10/sup 8/ V/cm, independent of the current under any gap length. With this result, a model which shows the choice of minute projection is suggested. In order to certify this model, an MCP phosphor-anode is used. As a result, it is found that the minute projections which emit electrons melt with heat and are chosen when the voltage rises.<<ETX>>