So that no sparks fly

Europe wants to be the first continent to be climate-neutral by 2050. At least that is what the "European Green Deal" envisages. In order to fulfil this ambitious vision, new technological approaches and feasible solutions are needed. Great potential to replace fossil fuels is attributed to technologies that utilise green hydrogen - whether for energy and heat generation or as a fuel.

However, hydrogen technologies harbour considerable risks, as junior professor Dr Christian Franke from the University of Jena knows. "Together with air, hydrogen forms an explosive mixture." Even the tiniest sparks are enough to trigger explosions. This currently limits the use of hydrogen considerably, says the physicist from the Institute of Applied Optics and Biophysics.

In a new joint project, the team led by Franke and project manager Dr Andreas Stark has set itself the task of making the measurement technology required for the examination and maintenance of hydrogen tanks and pipes so safe that no sparks can occur. The project "3D measurement using explosion-protected endoscopy with structured lighting" (3D-Vens) will be funded by the Federal Ministry of Education and Research with a total of around three million euros over the next three years. In addition to the team from the University of Jena, researchers from the Fraunhofer Institute of Applied Optics and Precision Engineering and three commercial enterprises are part of the consortium, which began work at the beginning of July.

Measuring head manages without electronic components

The aim of the project is to build an endoscope demonstrator over the next three years that combines other aspects in addition to explosion protection, such as the use of miniature optics and multi-core fibres as well as a new type of 3D measurement method. The special feature of this integrated approach is that the measuring head itself - which could come into contact with hydrogen - does not contain any electronic components that could form sparks, thus minimising the risk of explosion, as Andreas Stark, the scientific coordinator of the network, emphasises.

In order to obtain a three-dimensional image of the objects being examined, patterns are generated in the endoscope using structured illumination and, after interacting with the object, these are guided out of the system via a separate fibre bundle. "This is where the electronic processing into an image takes place," says Christian Franke. Multi-core fibres are used - these are bundles of up to twelve individual fibres, each with a diameter of 150 micrometres. "We can control each fibre separately and thus achieve a high spatial resolution and depth of field." Details as small as 100 micrometres (roughly equivalent to the diameter of a human hair) can be imaged in real time with such an endoscope and without any risk of explosion.