The ray gun has been a staple of science fiction since HG Wells’s The War of the Worlds, but fantasy is now reality as the first heat-ray weapon goes on display in London this week.

Raytheon, the American defence company, is hoping to find customers for its Silent Guardian system, developed as a form of non-lethal crowd control, which will be shown at the Defence Systems and Equipment International (DSEi) exhibition, the world’s largest arms fair, at the Excel centre in Docklands, East London.

The weapon emits a wave of energy that vaporises skin moisture, causing an intense burning sensation. Ministry of Defence (MoD) officials will be invited to place their hands in front of the machine’s ray and experience what its maker describes as “intolerable” pain.

A Raytheon marketing brochure explains: “The system’s antenna emits a focused beam of millimetre-wave energy. The beam travels at the speed of light and penetrates the skin to a depth of 1/64th of an inch, producing an intolerable heating sensation that causes the targeted individuals to instinctively flee or take cover.”

Raytheon envisages that the ray gun will be deployed for crowd-control and peacekeeping missions. It said that the machine had been certified by Guinness World Records as the first heat-ray gun.

The weapon is shaped like a satellite dish and can be mounted on a van or on a security checkpoint. It emits a beam of electromagnetic radiation up to half a kilometre, which causes water particles in the skin to vibrate, creating a burning sensation equivalent to touching an oven ring.

Raytheon insists that the gun does not cause any physical harm unless a victim is exposed to the ray for a sustained period.

Anti-arms industry campaigners are opposed to Raytheon promoting the system in Britain. Symon Hill, a spokesman for the Campaign Against Arms Trade, said: “The Silent Guardian sounds like a dictator’s dream – a weapon to suppress dissent and protest.”

Raytheon began work on the raygun in 1993 when 19 US soldiers were killed in Mogadishu, Somalia. The troops were trying to withdraw from the city and were surrounded by thousands of civilians and armed militia.

A Raytheon spokesman said that a heat-ray gun would have given the troops the ability to clear streets without using lethal force.

Despite the claims that the heat ray is harmless, the American military so far has rejected calls for it to be deployed in Iraq. There are still concerns about how the weapon affects eyes or contact lenses worn by those coming into contact with it.

The Silent Guardian will be just one of thousands of weapons and pieces of military equipment on display at the controversial show, which is a rare opportunity for leaders in the global defence industry to meet. Antiarms trade protesters are planning a campaign outside Exel, which effectively will become a high-security military base for the four days of the show.

An estimated 1,350 firms will be exhibiting at DSEi, including the big British and American companies. There will also be arms businesses from Russia, China and Israel.

Howard Wheeldon, a defence analyst with BGC Partners in London, said: “Defence exports are very important to the UK economy, improving our balance of trade by about £5 billion a year and employing over 65,000 people. It is also something we happen to be good at and DSEi is an important showcase.

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