Triggers Lightning Strike
During Japanese Experiment
based on an article by Paul Mortensen as
reported in the September, 1997 issue of Laser Focus World
Lightning was triggered by a laser beam for the
first time in an outdoor experiment conducted by a group of researchers
in Osaka, Japan. As reported in the September, 1997 issue of Laser
Focus World, researchers from Kansai Electric Power Company, the
Institute for Laser Technology, and Osaka University conducted
The impetus for the research is the more than
500 lightning strikes per year on electric transmission lines
that result in widespread power outages. The researchers hope
to reduce that number through use of the laser system.
The experiment was successful in conducting natural
lightning discharges to ground of 35,000 A. By exposing the tip
of a 50-m conducting tower to 20-m s pulses of light condensed
on concave mirrors and discharged from two carbon dioxide (CO2)
lasers, a peak output of 20,000 MW was produced.
A lightning tower, electron-beam controlled CO2lasers,
and two large-aperture focusing telescopes equipped with focusing
mirrors of 500 and 1000 mm made up the laser system. Plasma channels
at the top of the 50-m lightning tower were created from the system's
output. The two laser heads delivered two 1-kJ/50-ns laser pulses
that were directed by the two telescopes and opened a conducting
path for lightning by creating a plasma state - ionized positive
and negative electric charges in super heated air.
In order for a lightning strike to be triggered,
the motion of thunderclouds had to be monitored to choose the
precise time for a laser shot to take place. Intense uniform laser-plasma
channels of at least 1m also had to be produced
A thunderstorm-monitoring network was set up around
the field site. Each station in the network measured electric
fields under clouds and sent real-time data to the laser system.
Plasma channels were produced when thunderclouds were ready to
discharge because of the microsecond response of the laser trigger.
Precursor ultra-high-frequency pulses that are generated in thunderclouds
when the electrical field becomes critical allowed the precise
timing to be achieved by detection of preliminary breakdown pulses.
Creation of the plasma channels during the field
test was not without difficulties. Snow typically accompanied
thunderstorms. The snow particles tend to degrade the line density
of the laser plasma by attenuating the laser energy near the focal
point. Aerosol cores of plasma were depleted and caused the line
intensity of the plasma channel to be less dense in snowy weather
as opposed to fine weather. Additionally, a plasma channel could
not be produced within 30 cm of the top of the antenna when the
electric fields were more than 1000 kV/m. This was attributed
to the corona space charge generated by high electric fields at
the top of the tower.
Beam ducts were built to protect the laser beam
and irradiated a dielectric target attached to the top of the
tower to generate continuous plasma channels on its surface. Alumina
powder was sprayed above the target to generate a long plasma
channel in air. The plasma channel consists of plasma beads made
from the alumina powder as a core.
The research group began outdoor experiments in
1994 after having successfully completed indoor experiments beginning
in 1990. NASA originally began work on lightning conduction by
laser in the USA in 1978. Other groups have attempted outdoor
tests but have been unsuccessful. In the future, researchers plan
to use lasers with higher output and ultrashort pulses.
Update!!!!! The ESD Journal
recently recieved an e-mail from Dr. Vernon L. Mangold adding
new information to our article. His e-mail reads as follows:
"NASA was not the organization that conducted
the laser triggering project, it was an Air Force project conducted
at NASA KSC during the project Thunderstorm in 1978. It was my
program and was not successful because during the short time we
had after getting set-up and running, we did not get any lightning
cloud formations directly overhead. We fired the laser a number
of times, but only had less than a week before we had to tear
it down and return to Wright-Patterson Air Force Base in Dayton
Ohio. The laser was CO laser, not a CO2 laser."
The ESD Journal thanks Dr. Mangold for his comments.