Suppression of secondary electrons from target surface under pulsed ion beam bombardment

The producing mechanism of secondary electrons from target surfaces under ion beam bombardment is discussed. Several methods to suppress the secondary electrons in special vacuum devices and their advantages and disadvantages are introduced. The ways of using self-bias and curved surface targets are proposed and verified in the experiment. The results show that the secondary electrons can be effectively suppressed when the self-bias is larger than 80 V. The secondary electron yield decreases by using curved surface target instead of flat target. The secondary electron yield calculated from the experimental data is about 0.67, which is slightly larger than the value (0.58) from the literature due to the impurities of the ion beam and target surface. The effect of suppressing the electron countercurrent by the self-bias method is analyzed. The result shows that the self-bias method can suppress not only the secondary electrons from target surface under ion beams bombardment, but also the electron countercurrent resulting from the instability of the pulsed power source.