  The purpose of this project is to investigate the use of charge couple
devices (CCDs) to detect electrons directly. This can be done in transmission
electron microscopy (TEM) for electrons over 100 KeV, but for space plasma
instruments, lower energies are of interest. At the entrance surface of a back
illuminated CCD, there is an insensitive layer of oxide and silicon. This layer
needs to be kept as thin as possible, in order to detect the electrons of
interest, which have short absorption depths. Following analysis of the
parameters, we are going to measure the least amount of energy we can detect
from electron interaction with the thinned layer. The detection process is
simulated by combining two separate models: First: Mulasses, using Geant4, to
simulate the interaction of the incident electron with the silicon, giving the
energy absorption as a function of depth; Second A model from Stern et al. of
the charge collection efficiency as a function of depth. Combining these models
gives a measure of the charge collected as a function of incident electron
energy, which is the relationship of interest.
