An electron emitter has an emitter section formed on a substrate, a cathode electrode
formed on one surface of the emitter section, and an anode electrode formed on
the same one surface of the emitter section and cooperating with the cathode electrode
in providing a slit. A pulse generation source applies a drive voltage between
the cathode electrode and the anode electrode. The anode electrode is connected
to GND (ground). The slit has a width in the range from 0.1 m to 50 m.
