Direct Electron Detection And Imaging Using CCD

TL;DR

This paper explores the feasibility of using charge-coupled devices (CCDs) for direct electron detection across various energy ranges, combining simulation models to analyze detection efficiency and charge collection.

Contribution

It introduces a combined simulation approach using Geant4 and a charge collection model to evaluate CCD performance for electron detection at different energies.

Findings

Simulated charge collection efficiency as a function of electron energy.

Determined the minimum detectable energy levels for electrons.

Analyzed the impact of CCD surface layer thickness on detection capability.

Abstract

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.