Energy distribution measurement of a gallium liquid metal ion source modulated at high frequency by a focused laser beam

Abstract

The emission current of a gallium liquid metal ion source (LMIS) was modulated at 500 KHz by focusing a modulated laser beam to 20 μm diam on the tip of LMIS. The peak-to-peak amplitude of the modulated ion current was 300 nA when the average laser power was 15 mW with 83% modulation depth, when the ion source was operated at 1–10-μA dc emission current range. Total energy distributions of ions emitted by the LMIS were measured with and without modulation. We found minimal difference between the energy distributions spread with and without modulation, to within the experimental error.