Thursday, October 7, 2010

New Airport Screening by Long Wavelength X-ray and by Microwave

Two weeks ago I was full body scanned as I passed through airport security in Detroit. The operator as in a little closet right next to the unit. It seemed silly to have the poor operator all enclosed in this little showstall sized booth.

There are two kinds of full-body scanners. There are Millimeter Waves and Back-scatter X-ray.

X-Rays are 10 femtometers to 10 nanometers in size. This is 100 times smaller than one millimeter, yet this technology is being called "Long wavelength X-Ray" scanning. The "millimeter waves" don't penetrate very deep, so they are good for picking out stuff on the surface of the body. The waves are 30 to 300 gigahertz, which is 10 - 100 millimeters: as advertised. Since these millimeter waves penetrate, somewhat the collectors need to be spread out, and the result is a 3-D image.

They do penetrate several centimeters though, so this is a little disturbing for medical reasons. These airport scanners have been in experimental use since 2007.

The other technology for full body imaging is "Back-scatter X-ray." A backscatter X-ray is the same as a regular x-ray except that the film is beside the camera rather than on the opposite of the body, that is, it catches the reflected X-rays not the transmitted X-rays that shine through your bod. The X-ray is a stronger kind of radiation, so it is a little more hazardous.  This kind of imaging makes a regular two dimensional image.

I don't think that 3-D images are appreciably better than 2-D images. You can see a gun on either one.

These scanners cost $150,000 each, so they are expensive, but if they last a several years, it is not too bad. The biggest value is making the inspection process less predictable.