[sabali (OP)]

I'm writing a book about a group of criminals and just wanted to be really factually accurate.
So far I;ve heard Lead can , and carbon paper. if anyone can add to these two or expand on my question with a answer I would greatly appreciate it.

thanks

[JP]

Very dense materials generally block x-rays well.  Lead and tungsten are frequently used.  Of course, if you put these in your luggage at an airport, you'd be pulled aside for "extra screening," since having a chunk of lead in your luggage is a sign that you're trying to hide something.

[sabali (OP)]

Thanks , Do you know alot about lead ?

[RD]

A few millimeters of metal isn’t necessary enough to block X-rays :
you can see the truck's engine, as well as the illegal immigrants in the back ...


http://www.thenakedscientists.com/forum/index.php?topic=6326.msg254272#msg254272

https://en.wikipedia.org/wiki/Backscatter_X-ray

[sabali (OP)]

i suspect  those x ray machines are alot more powerful then the tiny ones that scan packages.
thats just logical.

im interested in hiding something concealed within a package

[Bored chemist]

RD, that's a backscatter image, so the xrays don't need to go through the engine to image it.

[sabali (OP)]

hey bored chemist i sent you a personal message

[RD]

RD, that's a backscatter image, so the xrays don't need to go through the engine to image it.

They do need to pass through the metal bodywork of the truck for the engine to be visible,
(bodywork could be Aluminium rather than steel)


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[Bored chemist]

If they didn't passsthrough that then they wouldn't be a lot of use for this purpose. The point is that the skin of the truck is quite thin.

[sabali (OP)]

check your inbox mate

[CliffordK]

As mentioned, the x-rays will pass through different substances at different rates, thus giving an image of what is inside of the container.  Presumably if something isn't showing up well, the intensity or exposure time can be increased.  Or they will do a physical inspection of the questionable object.

The biggest concern is to make one object appear like another.  

I.E. semi-liquid explosives could be put into toothpaste and shampoo bottles, which is why those items may be restricted from carry-on bags.  Of course, a detonator stuck to a toothpaste tube might show up in the scans.

Years ago I took a 110V/220V transformer to Europe with me which was a block of steel & copper wires weighing about 10 or 20 lbs.  But, even so, it probably had a very distinctive look in the X-Rays.  Modern laptop power supplies invariably take 110/220V, and thus all one needs is the proper plug adapters.

A well supplied terrorist undoubtedly would get access to a fluoroscopy machine for "testing" purposes.

[chris]

The x-rays have definitely gone through the people because their lungs look nice and dark in the pictures. I'm very impressed at the quality of that image - it's good enough to do diagnoses of TB almost. I wonder if that's part of HMRC's cost-cutting initiative - save money by screening people and trucks on the way into the country...

[Bored chemist]

Knowing the HMRC they are more likely to use the technology to assess the quality and hence the true value of the bananas.
I agree that they xrays go through the people (twice), but, again, that's hardly news.

[SeanB]

The whole truck scanner does use a very high power source, to get the detected signal out of the noise floor. Note there is no driver inside, as otherwise he would be regularly exposed to a very high dose of very ionising radiation. not good for the hidden passengers, and probably quite capable of fogging any undeveloped film inside the truck, possibly even possibly erasing flash media ( bye bye truck engine management, and any electronics on board the truck) in the path.

Airline scanners hopefully are not as high powered, as they do not need to penetrate a few inches of steel plate.

[damocles]

The principle of X-ray examination is that different atoms reflect or absorb X-rays differently. So the main thing that X-rays show up is the atomic composition of whatever material they pass through/fail to pass through/reflect off. In most situations X-rays pass easiest through light atoms (hydrogen, carbon, nitrogen, oxygen), and with more difficulty through heavier atoms (phosphorus, sulfur <iron, nickel, copper <silver <gold , mercury, lead)

The most favourable likely thing for your international criminals to have in their package would be uncut diamonds (carbon), and to disguise them by mixing in with a pack of scorched almonds or similar (also mostly carbon & oxygen). The only thing I am not sure of is whether the x-ray scanner would pick up suspicious diffraction rings or spots from the crystalline nature of the diamonds which would not be so clearly produced by the chocolates. Similarly most drugs are not detectable by X-ray machines, but they do have sniffer dogs at airports!

[Bored chemist]

OK, so I know that the manufacturer's website is hardly an unbiased opinion but it seems that the Xray dose isn't very big.
http://www.saic.com/products/security/vacis-xpl/
My guess is that the driver isn't in that vehicle because he is talking to Customs about his cargo.
Once they see the image they will want to talk at more length.

I'm fairly sure that x ray scanners don't produce diffraction images because it would need monochromatic Xrays and the image would be horrible convoluted.

[damocles]

I'm fairly sure that x ray scanners don't produce diffraction images because it would need monochromatic Xrays and the image would be horrible convoluted.

The most common/simplest type of X-ray generator has an electron beam at several kV impinging on a metal target -- often copper. It therefore provides not a monochromatic source, but certainly a line spectrum with few lines, and CuKα dominating. While it is very likely that a scanner image would be too convoluted for diffraction spots or rings to be detected, I would not be totally sure of that.

The brochure that can be downloaded from the linked manufacturer's site says, inter alia,

Powerful imaging performance

The VACIS XPL system’s switched-energy X-ray source simultaneously screens vehicles at two
different energies, displaying organic threats such as explosives, stowaways and drugs in a
different color to help inspectors quickly evaluate the vehicle’s contents. The system also
provides conventional high-resolution black-and-white X-ray images to help inspectors
identify metallic threats such as guns.
The system can image passenger cars and light trucks from roof to pavement and bumper to
bumper, allowing the entire vehicle to be quickly and efficiently screened.

"Two different energies" implies a fairly efficient monochromator, and effectively a pair of monochromatic scans. I think the real issue about detecting diffraction would come with spatial resolution and convolution rather than wavelength convolution. Diffraction spots are much weaker than a direct through-beam or a specular back-scatter, and their presence would not generally be welcome in an imaging procedure anyway (they would tend to blur and confuse the image).

[Bored chemist]

""Two different energies" implies a fairly efficient monochromator, and effectively a pair of monochromatic scans."
Or it implies two different acceleration voltages and "optimistic" writing.

[CliffordK]

The most favourable likely thing for your international criminals to have in their package would be uncut diamonds (carbon), and to disguise them by mixing in with a pack of scorched almonds or similar (also mostly carbon & oxygen).
[...]
Similarly most drugs are not detectable by X-ray machines, but they do have sniffer dogs at airports!

Diamonds (and drugs) are non metallic.  So, as long as the airports are using simple metal detectors for people, then it would be possible to carry them on (or in) one's body.  The new whole-body scanners may not be at a high enough power to pick up non-metallic stuff in the GI tract.

[JP]

""Two different energies" implies a fairly efficient monochromator, and effectively a pair of monochromatic scans."
Or it implies two different acceleration voltages and "optimistic" writing.

I believe most airport X-ray baggage scanners use a wide bandwidth source and a dual energy detector, which allows the separation of the high and low-energy X-rays.