According to a panel of experts formed by national intelligence agencies, some of the mysterious cases that have afflicted U.S. embassy personnel and C.I.A. officers in 2016 in Cuba and Russia, China, Russia and other countries are most likely caused by pulsed electromagnetic radiation.

Similar findings were found in the report to National Academies’ 2020 report. A committee of 19 experts from medicine concluded that directed, pulsed radiofrequency energy was the most plausible explanation for the illness. It is dubbed the Havana Syndrome.

The reports are not conclusive, and the authors of them don’t provide any information about who or why the embassies were targeted. The technology behind the suspected weapons is well-known and dates back to Cold War arms races between the U.S.A. and the Soviet Union. High-power microwave weapons are designed to disable electronic equipment. These pulses of energy, however, can also cause harm, as evidenced by the Havana syndrome reports.

As an electrical engineer, I have spent many decades studying the physics of microwaves. This includes work with the U.S. Department of Defense. The directed energy microwave weapon converts energy from a source (a wall plug in the lab or an engine on a military car) into electromagnetic energy focused on a target. Directed high-power microwaves can cause damage to equipment, especially electronics, and not kill anyone nearby.

Boeing’s Counter-electronics High-powered Microwave Advanced Missile Project is a good example. It’s a high-power microwave source that’s mounted inside a missile. The Tactical High-power Operational Responder was developed recently by the Air Force Research Laboratory to eliminate drone swarms.

Cold War origins

These microwave-directed energy devices were developed in the U.S. in the 1960s. In the 1960s, pulsed electricity enabled them. Pulsed power is a short-term generator of electrical pulses with very high power. This means they have both high voltage (up to a few megavolts) and large currents (tens or hundreds of kiloamps). This is more than long-distance power transmission lines with the highest voltage and approximately the same current as a lightning bolt.

The idea of a plasma physicist at the time was that you could create a 1-megavolt electron beam using a 10-kiloamp current. This would give rise to a beam power of 10 billion or gigawatts. One gigawatt of microwaves can be made by converting 10% of this beam power using standard microwave tube technology dating back to the 1940s. Comparatively, today’s microwave ovens produce around 1000 watts. That is a million times less.

This technology was the catalyst for a subset in the U.S.-Soviet arms races – a microwave power derby. In 1991, the Soviet Union fell. I was among the first Americans to access Russian pulsed energy accelerators. The SINUS-6 is still in use in my laboratory. My decade-long collaboration with Russian colleagues was fruitful. However, it ended quickly after Vladimir Putin’s rise.

While high-power microwave research continues in the U.S., Russia and China, it has seen a surge in China. Since 1991, I’ve visited Russian labs and Chinese labs. The investment made by China is far greater than that of the U.S. Numerous countries have now started high-power microwave research programs.

A lot of power and little heat

These high-power microwave sources can generate extremely high power levels but also produce short pulses. My lab’s SINUS-6 produces an output pulse of approximately 10 nanoseconds. This is a billionth of a second. Even though the SINUS-6 generates 1-gigawatt output power, a 10-nanosecond pulse still has a 10-joule energy content. This is a significant difference from the microwave oven, which generates one kilojoule (or thousand joules) of energy in a single second. Boiling a cup of water takes approximately 4 minutes, equivalent to 240 kilojoules.

These microwaves, which are high-power microwave weapons, don’t produce noticeable heat.

These weapons require high power because they generate very high instantaneous power, which results in very high electric fields. These fields scale according to the square root power. These high electric fields can cause electronic disruptions, which is why the Department of Defense is looking into these devices.

It affects people

According to the National Academies report, high-power microwaves can impact people via the Frey effect. The human head receives microwaves from the low gigahertz frequency band as an antenna. The U.S. military reported hearing sounds as one of their symptoms. Other symptoms of Havana Syndrome sufferers have reported nausea, headaches, hearing loss, lightheadedness, cognitive problems, and headaches.

According to the report, electronic devices weren’t damaged during the attacks. This suggests that the power levels required to produce the Frey effect are lower than would be needed to attack electronics. This is consistent with a microwave weapon of high power located far from the targets. The inverse quad law shows that power decreases with distance. This means that one of these devices could generate a power level at the target which is too low to cause damage to electronics but could still induce the Frey effect.

The Russians and Chinese can use high-power microwave sources such as those used in Cuba or China. Although the truth about what happened to U.S. personnel in Cuba or China and why is still unknown, the technology most likely involved comes straight from textbook physics, and the world’s military power continues to develop and deploy it.