The results of our experiments showed that ion production depends on several factors such as the density difference between the projectile and the target and evaporation energy as well as the impact velocity of Ag projectile. These dependences are confirmed by analyses of impact craters on different targets (Al, Mo and Au). The existence of Ag residues means the impact velocity is not enough to vaporize the Ag projectile, and the crater depth shows the relative difference of degree in the evaporation of the target and the .projectile. The best material for the target of a dust analyzer is one capable of ionizing dust particles effectively. Our results suggest that molybdenum is the best target material in the three materials only when silver is used as the projectile; molybdenum can vaporize a projectile much efficiently because molybdenum has larger evaporation energy than other materials.

Table 1. Classification of craters by shape and size.

The numbers in parentheses indicate the mean diameters of each type of crater._

Number Ripplc-Shapcd Ag Residues [%] Unknown ^Trace^

Inside Outside Both 1 1 O X

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