Handheld terahertz wand to unmask terrorists

New Scientist ^ | 09:30 12 July 04

[ckilmer]

Handheld terahertz wand to unmask terrorists

09:30 12 July 04

Exclusive from New Scientist

The next generation of security screening systems will be based on so-called terahertz technology that can see weapons and explosives hidden under people's clothes. But using terahertz radiation to produce X-ray-like images of passengers is likely to be unacceptable for routine use, as it will allow security staff to see the people they are scanning as if they were naked.

The answer, according to a company called TeraView in Cambridge, UK, is to use the terahertz radiation in a different way. Instead of producing images, it plans to build a detection system that picks up the telltale frequencies that explosives or metallic objects reflect and absorb when terahertz waves hit them.

Terahertz waves occupy a relatively unexplored part of the electromagnetic spectrum between microwaves and infrared. By sending short pulses of terahertz waves at a person and recording what is reflected it is possible to image the materials hidden next to the body (New Scientist print edition, 14 September 2002).

TeraView has just begun working with Smiths Detection of Bushey, Hertfordshire, UK, one of the world's largest manufacturers of X-ray security scanners, to develop a hand-held terahertz security wand that will scan passengers. But to avoid privacy concerns, it will not be used to generate an image on a screen.

Instead, the system will check to see which wavelengths of terahertz radiation have been absorbed and reflected by the subject and pick up the characteristic spectral signatures of explosives, metals and other chemicals such as drugs. All the operative will see is a light that shows green if all is OK or red if not.

Vital clues

TeraView has been able to create a terahertz "signature" for a given material because

some terahertz frequencies are absorbed by different substances while others are reflected. So metal will absorb and reflect different frequencies to a plastic explosive, say. However the firm is saying very little about the nature of these signatures to avoid people developing countermeasures.

In addition to safeguarding passengers' privacy, not having to have security staff continuously watching a screen has other advantages, says Mike Kemp of TeraView. People's concentration can drift, missing vital clues, but the automated detection system will always stay alert.

The TeraView system generates terahertz radiation by shining pulses from a powerful infrared laser on to a crystal of gallium arsenide semiconductor. The bulkiness of the laser means the whole setup is large enough to fill the back seat of a car, so the wand has to be linked to it with an optical fibre.

Kemp says the firm is now working towards a more compact but equally powerful diode laser which will fit into the wand. The technology should arrive in airports within two years.

[FairOpinion]

"Instead, the system will check to see which wavelengths of terahertz radiation have been absorbed and reflected by the subject and pick up the characteristic spectral signatures of explosives, metals and other chemicals such as drugs. All the operative will see is a light that shows green if all is OK or red if not. "

That makes more sense.

I remember seeing those pictures and they even started to use those machines at one airport, I forget where.

[Young Werther]

"Wingardium Leviosa!"

[buffyt]

Well, I plan to STAY on my diet/exercise regimen forever then. So when I am scanned, they won't laugh at TUBBY! Lost almost 20 lbs. so far. Ten more to go. If they are gonna scan my ugly bod in public places, I wanna be thin. LOL

[ovrtaxt]

Wow, can you imagine having to look at images like that all day? Enough to make you join a monastery!