Abstract: A flat display screen including a.cathode provided with field effect electron emission means, a cathodoluminescent anode placed opposite to the cathode, an extraction grid associated with the cathode, and at least one filtering grid, permeable to electron bombardment and biased to forbid parasitic ions, generated on one side of this filtering grid, to reach the cathode or the anode located on the other side.

Abstract: A liquid metal ion source is disclosed, wherein it comprises an ion emitter tip, ion source material holder means holding ion source material for supplying liquid metal ion source material to said ion emitter tip, ion extracting means for extracting ions from said ion emitter tip, when a voltage is applied between the ion extracting means and the ion emitter tip, the pulsing means for pulsing the relative voltage applied between the ion extracting means and the ion emitter tip. A DC voltage corresponding to the threshold voltage V.sub.th for ion beam extraction is applied between the ion emitter tip and the extracting electrode, what permits to extract an ion beam having a high current density by superposing a pulsed voltage on the DC voltage.