Small project: Simulator for a better understanding of inverse space Proposer / Project manager:

The goal of the project was to create a simulator for the diffraction imaging of crystals in the transmission electron microscope. Because the concept of inverse space, which comprises the theoretical background for the understanding of the diffractogram and with which students consistly have difficulty, the plan was to deploy this simulator (in a way similar to a flight simulator) to enable students to gain an understanding based on mathematics, i.e. develop a feeling for this area. Real images from the electron microscope (taken by F. Gramm at EMEZ) were also used as a basis for the most important steerable microscope parameters, in order to make the experience with the apparatus as realistic as possible. A comprehensive help file regarding the various parameters provided the theoretical background. The students F. Marrafino and M. Häfelfinger from the Fachhochschule Nordwestschweiz (Prof. M. Vogel) programmed the simulator in Java in the framework of their Bachelor’s thesis, such that it can be deployed on all usual operating systems (Windows, Mac Os, Linux).

The following suggestions for improvement were submitted:
– A finer gradation of crystal tilt to improve clarity. This would require expanding the data
– The integration of a vertical section image of the microscope which – if possible coupled with the respective diffractograms – visualises changes in the optical path in the microscope. An interactive variation would in particular require a follow-on project.
– The integration of the theoretically computed diffraction images in addition to the real microscope images
– For one of the parameters only images for 3 settings were taken on the electron microscope. For the interim levels the images were interpolated via software, and this interpolation has not yet been achieved optimally. Improving it (i.e., reprogramming it), would be desirable because previous versions have only been able to represent reality in a very limited way.
– A few programming details. In particular, some images are not optimally aligned with one another. Perfecting this would be a visual improvement.

Over the past few weeks the simulator has been available for the first time to the students of the electron microscope course (Dept. MATL, ETHZ). Their feedback has been extremely positive: the simulator is very clear, the theory very helpful and comprehensible. The simulator has achieved its goal of significantly improving the understanding of abstract material.