Measuring Device for Air Pollutants Mobile UV Spectrometer Can Detect Gas Leaks at 2.5 km

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A team from TU Graz (Austria) has developed a UV dual-chamber spectrometer that detects gaseous pollutants with extremely high sensitivity. Particularly exciting for electronics developers: thanks to a new optical design, the system was reduced to the size of a moving box, and the complexity of the control electronics was massively reduced.

Until now, UV dual-chamber spectrometers were complex laboratory setups. The team led by Birgitta Schultze-Bernhardt at the Institute of Experimental Physics at TU Graz (Austria) has now achieved a breakthrough in device technology. The system developed by the team measures pollutant concentrations, such as formaldehyde, within 0.5 seconds with high spectral resolution.

The Laser Source Makes the Difference

The crucial trick for the mobility and robustness of the device lies in the laser source. While the first generation still required two highly precise, actively synchronized laser sources, the new development uses a single-laser design that generates the double laser pulse. From a system development perspective, this results in significant advantages:

• Elimination of active phase stabilization: The system operates on the so-called free-running principle. Since both pulses originate from the same source, the complex electronic control technology (phase-locked loops) for synchronization is no longer necessary.
• Reduced computing load: The inherent stability of the single-laser setup lowers the requirements for real-time signal processing of the detected interference patterns.
• Miniaturization: The entire setup has been reduced to the size of a moving box, enabling its use on mobile measurement platforms.

60-Year-Old Reference Values Corrected

The spectrometer operates in the ultraviolet wavelength range and excites electronic transitions as well as rotational and vibrational states (rovibronic transitions) of gas molecules. With a resolution of 1 GHz, the system detects absorption patterns that remain invisible to conventional UV spectrometers.

The importance of this hardware precision and accurate calibration became evident in tests with ultra-pure formaldehyde, which was produced at the Institute of Organic Chemistry at TU Graz (Austria): In collaboration with the Harvard-Smithsonian Center for Astrophysics, researchers were able to correct fundamental rotational constants by up to 15 percent, which had been considered standard since the 1960s.

Multispectral Measurement and Field Use

With a range of up to 2.5 kilometers (1.5 miles) via retroreflector, the device targets the remote monitoring of industrial areas. The current development focuses on two areas. 1. Multispectral Detection: The hardware architecture is being expanded to determine the concentration of several different pollutants with a single measurement followed by digital signal separation. 2. User Experience: Supported by a "Proof of Concept Grant" from the European Research Council (ERC), the system is to be automated to the extent that it can be used in environmental agencies or companies without expert knowledge.