Further Development of Fluorescence Excitation Spectroscopy

|   Physik, Chemie, Gäste

Philipp Bokatius, Gudrun Mende, Matthias Rang & Peter Stolz

Project Status after the Third Project Year

In the course of the year, after numerous delays, we were finally able to set up the system. Although there are still some improvements to be made before the system is fully functional, such as the installation of the second photomultiplier, the difficulties we described in the previous annual reports were all resolved during the course of the year.

The mechanical solution for the optical shutter blades in front of the photomultipliers still occupied us intensively. These fine metal blades must be absolutely light-tight and at the same time be able to close a large illumination aperture quickly. Since there were no commercial solutions for this, we had to develop the blades and their guides ourselves and have them constructed with contract milling work. The blades tended to jam in their light-tight sliding fit upon closing, even with a slight twist in the structure.

The lighting proved to be a new problem. Due to the focus on the light guide opening, the heat protection filters are not evenly illuminated. They can heat up more in the middle area and burst due to inhomogeneous expansion. However, we were also able to solve this problem through improved air cooling.

Since this project is not about conducting an experiment but about developing a system on which many series of measurements can be carried out over the next few years, all these problems have to be fundamentally and carefully solved – a challenge for our small team (without a technical development department). But we have the impression that we have now have a grip on all the major problems and will be able to put the plant into full operation in the last year of the project. First, it will be characterised in comparative measurements to Jürgen Strube's existing plant.

Another focus during the year was the development of the software, which is now functional. It allows (without reprogramming) the creation of new measurement procedures for failed or not yet measured sample types. This gives it much more flexibility than originally planned.


In the coming months, there will be more bug fixes, both in the software and in the entire measuring procedure. We are looking forward to the first characterisation measurements and the final performance of the new system, which will emerge on the basis of these data. Measurements on test specimens will also allow a direct comparison with the existing system. We very much hope that the new possibilities will prove their worth and be reflected in the characterisation. The second half of the year will also see the moderate modernisation of the old plant. Here, we will leave the proven mechanical construction entirely and only change the amplifier electronics, data acquisition cards and, above all, the software, to the solutions developed in the new plant.

Demonstration of the installed system at the KWALIS gGmbH research institute during the Scientific Advisory Board meeting on 1 July 2022. At the center of the system you can see the measuring chamber with symmetrically mounted filter wheels and photomultiplier housings, but still missing cabling, fibre optics, coolant, pneumatic and evacuation hoses.