The Fraunhofer-Gesellschaft is developing a new Raman LiDAR system for gas analysis in the project "Raman Atmospheric DetectIon And raNging Technology" (RADIANT). Involved are the Fraunhofer Institute for Microelectronic Circuits and Systems (IMS), the Fraunhofer Institute for Applied Solid State Physics (IAF), and the Fraunhofer Centre for Applied Photonics (CAP) in Glasgow. The goal is to reliably detect hydrogen leaks from a distance.
The technology is based on Raman scattering. Molecules are identified via their characteristic scattering signal. Simultaneously, the measurement of the light travel time allows spatial localization. According to Fraunhofer, the system can also operate in daylight as it measures in the so-called solar-blind UV-B and UV-C range. In this spectral range, solar background radiation is low, which increases sensitivity.
Detector technology for weak signals
A central challenge is detecting very weak optical signals, which are sometimes in the range of individual photons. Fraunhofer IMS in Duisburg is developing back-illuminated silicon photomultipliers (BSI-SiPMs) with increased UV sensitivity for this purpose. "The detectors are specifically optimized for the requirements of time-resolved Raman measurements and enable the detection of extremely weak signals with high temporal resolution," says Dr. Maren Kasischke, Head of Industry at Fraunhofer IMS.
Additionally, a readout circuit for up to 32 channels is being developed. It is intended to allow parallel processing of spectroscopy signals and thus achieve high temporal and spectral resolution.
More flexible gas analysis without predefinition
Unlike previous systems, RADIANT relies on linear detector arrays instead of filter-based spectral division. This should allow the system to detect various gases without being predetermined for specific molecules. Fraunhofer IAF is additionally developing a large-area, cost-effective detector technology that can also be used in mobile devices in the future.
Applications in hydrogen infrastructures
Fraunhofer CAP coordinates the project and works on system integration. The goal is a practical overall system for industrial applications.
The technology is aimed at operators of energy plants, industrial processes, and pipelines. It is intended to enable continuous monitoring and early detection of leaks without endangering personnel. According to Fraunhofer, the project also aims to reduce the size, complexity, and costs of the systems.
In the long term, demonstrators are to be developed that can be transformed into marketable products. The project is funded by the Fraunhofer Joint Capability (JCAP) Building Programme.
