Abstrakt
We have investigated the charging of spherical glassy carbon grains of 3 to 6 micrometers in diameter under the influence of high energy electron bombardment. The single grain is trapped in the electrodynamic quadrupole trap and hold there for a long time (up to days).
The grain is isolated and therefore its charge can be altered by impinging and leaving electrons only. We are able to continuously monitor the grain charge and we can determine the net current on the grain.
We have measured the secondary electron-electron emission yield and we have observed the increase of the yield that was attributed to the electric field at the surface of the grain. The relation between the measured yield and primary energy follows the universal curve suggested by Draine (1979) and the total yield increases with square root of the surface electric field according to our results.