Innovative Deep-Sea Analysis Protects The Environment: The Double-Pulse LIBS Technology

The seabed contains large quantities of valuable minerals and metals that are urgently needed for modern technologies such as electric cars and wind turbines. However, discovering the deposits has so far been very complex: diving robots use gripping arms to take samples, which are then examined on board a research vessel. An innovative method is now opening up new possibilities for more environmentally friendly research into our oceans.

The Laser Zentrum Hannover eV (LZH) has developed laser-induced plasma spectroscopy (LIBS) using double-pulse lasers, a method for the environmentally friendly analysis of materials at a depth of 6,000 meters below sea level. Together with the Leibniz Institute for Plasma Research and Technology (INP) in Greifswald, the basic process behavior was investigated as part of a DFG project. The method provides precise elemental analysis in real time and replaces the laborious sampling of the seabed.

The double-pulse technique uses two laser pulses: the first pulse creates a cavity, a kind of hollow space in the water on the material's surface, the second pulse evaporates material from the surface and creates a plasma that contains the elements for the spectroscopic analysis. The problem here is the high pressure under water, which makes it difficult to generate meaningful spectra for precise analysis.

Optimized For Deep Sea Use
The current research focuses on the analysis of materials at a pressure of up to 600 bar, as is the case at depths of 6,000 meters below the water surface, and the use of laser pulses with energies of up to 150 millijoules. By adjusting the laser parameters, the team was able to optimize the measurements for the high deep-sea pressure. Short delays of 0.5 microseconds between the laser pulses and the precise adjustment of the measurement start times for the spectrometer are crucial for the quality of the data obtained.

The research results were published, among others, in the specialist journal "Spectrochimica Acta Part B: Atomic Spectroscopy" (DOI:10.1016/j.sab.2024.106877). The project was funded by the German Research Foundation (DFG) under project number 454848899.