Powerful laser can act as a lightning rod – New Scientist

With a test set-up in the Alps, researchers have shown that a powerful laser beam can divert lightning. But for now, this impressive technique will not yet protect us against lightning strikes.

In the summer of 2021, one was found special experiment place at an altitude of 2.5 kilometers, on Mount Säntis in the Swiss Alps. Next to a 124 meter high telecommunication tower, which is hit by lightning about a hundred times a year, researchers placed a powerful laser that can produce a thousand light pulses per second. The goal: to investigate whether the laser, the size of a large car, can serve as a lightning rod.

The experiment was a success. In the ten-week measurement period, thunderstorms above the tower lasted for a total of more than six hours. In those six hours, the laser diverted the path of lightning four times. One of the first camera images showed how a lightning discharge follows the path of the laser for 50 meters. “As soon as I saw that picture, I knew I had succeeded,” tells Jean Pierre Wolfa Swiss physicist who has been working on this research for twenty years.

Lightning rods have changed little since Benjamin Franklin invented the technique in the eighteenth century. These metal rods provide lightning with an easy path to earth, without damaging neighboring buildings.

This method works well, but the length of the lightning rod is limited and so is the size of the area it can protect. A laser lightning rod could protect a larger area from lightning strikes, such as a power plant or an airport.

Beaten path

The idea of ​​diverting lightning with a laser has been around for decades. Experiments have been done with it since the beginning of the century. ‘It wasn’t until 2000 that we had lasers that are powerful enough for this,’ says Wolf.

The technique works because the laser beam creates a path in the air with a low electrical resistance. This conductive path is created because the laser releases electrons from the oxygen and nitrogen molecules in the air. The path of positively charged molecules and negatively charged free electrons forms a plasma channel. As with the metal lightning rod, the current of lightning can easily pass through this.

Until the summer of 2021, the technique had only proven itself in artificially generated lightning in a laboratory and not in a real thunderstorm. Wolf: ‘At the time we couldn’t get the laser pulse frequency higher than ten times per second.’ That turned out not to be high enough for a real thunderstorm.

In recent years, researchers have therefore built a laser with a frequency of a thousand light pulses per second. That turned out to be the improvement needed for a successful test.

Practical

These lightning-deflecting lasers could also be used in the future to draw lightning from a thundercloud. That way lightning can strike in a safe place, far from buildings and airports. Still more work is needed for this. In the summer of 2021, the laser turned out to be unable to elicit lightning from storm clouds. The device only influenced the lightning that came naturally.

In addition, the laser currently consists of a complex, large and sensitive installation. To make it suitable for practical use, the design will have to be smaller, cheaper and simpler.