The Säntis is one of the most popular excursion mountains in the Lake Constance area. Just 20 kilometers from Feldkirch, at 2,502 meters above sea level, there is a panorama that spans six countries when the skies are clear. During storms, on the other hand, the 120-metre-high telecommunications tower at the summit is a veritable lightning magnet – ideal for the experiments starting in the summer of 2021.
The laser beam is so strong that it ionizes air molecules. “This ionized air, called plasma, becomes an electrical conductor”, explains physics professor Jean-Pierre Wolf. Lightning is deflected directly from the storm cloud.
three ton lasers
The three-ton “Laser Lightning Rod” (LLR) was brought to the Säntis by helicopter. It is eight meters long and one and a half meters wide. The LLR was installed next to the telecommunications tower, which is hit by up to 400 lightning strikes a year. The airspace around the Säntis had to be closed during the experiment. It took almost a year to analyze the vast amount of data collected, according to a press release from the University of Geneva. This analysis has now shown that the laser can effectively direct beams. “In the first beam where the laser was used, we could see that the discharge can follow the beam for almost 60 meters,” said international research group leader Jean-Pierre Wolf of the University of Geneva.
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Even in difficult weather conditions
Data analysis also shows that, unlike other lasers, the LLR works even in difficult weather conditions such as fog, as it literally penetrates clouds. So far, this result has only been observed in the laboratory.
In addition, the device’s power consumption is “reasonable,” Wolf said. It uses almost as much energy as an electric stove. As the laser flashes are very short, very high peak performance can be achieved with little power.
High speed cameras recorded
The Säntis tower is equipped with sensors that record lightning current, electromagnetic fields at different distances, X-rays and sources of radiation from lightning strikes. The researchers installed additional measuring devices and two high-speed cameras that recorded lightning strikes at up to 24,000 frames per second.
These cameras were located 1.4 and 5 kilometers from the top of the tower and provided usable results only in good visibility. This was the case for one of the four recorded flashes where the laser was on. Camera footage shows that the beam revolves around the laser beam for more than 50 meters and then hits the tower’s lightning rod. The slightly angled laser beam was directed so that it landed near the top of the tower. Comparisons with lightning recorded without a laser show that the lightning strikes the tower’s lightning rod much more precisely, thanks to the laser’s orientation.
Efficiency should increase
The next step for the research team will be to further increase the laser’s effectiveness. The long-term goal is to use the LLR to extend a 10-meter-long lightning rod by 500 meters. In the future, these lasers could protect sensitive installations, such as nuclear power plants or airports, from lightning, as the researchers write in the study published on Monday.
“Experimental Breakthrough” for Lightning Protection
“We believe this experimental breakthrough will lead to advances in lightning protection and lightning physics,” the authors wrote in the study. Until now, lightning protection was based on a technique invented by Benjamin Franklin nearly 300 years ago – a grounded metal rod. However, this only has a very limited scope.