quote:

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WASHINGTON: Cosmic ray detectors, already used to look into the great Cheops pyramid in Egypt, could be enlisted to peer into cargo holds in a bid to prevent possible terror attacks, scientists said.

The detectors read muon particles, which are more powerful than gamma or so-called X-rays.

They would peek into the millions of shipping containers entering the United States by air, ship and land, to detect even nuclear materials wrapped in lead, physicist Chris Morris of Los Alamos National Laboratory told a conference this weekend of the American Association for the Advancement of Science.

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The energies of the mu mesons spraying down from the upper atmosphere are on the order of somewhere around 1 GeV, if I may trust a back-of-the-envelope calculation I just did to account for relativistic effects.

Those buggers, as the article says, will indeed blast through near about anything and interact with the material.

A somewhat technical article on charged-particle imaging

quote:

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The muon radiograph in Figure 4 clearly shows the ease with which nuclear materials can be distinguished from background scatter. An x-ray radiography of a portion of the container, also shown in Figure 4, is plagued with problems from background scatter. Also, x-ray radiography does not provide three-dimensional views of a scene. Two-view x-ray radiography may be able to address some of these problems. The results of this study show that within the boundaries of weight limits, shielded containers of fissionable material can be easily obscured in ways that make it impossible to discriminate the material from legitimate cargo with x-rays. However, these are easily detected using muon radiography.

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Whee!

Quick Backgrounder on the mu meson

The Wikipedia has an excellent article on the mu meson.

Overview of the mu meson (the original article actually referred to mesons generally, of which the mu meson is not a true member, but older terminology has persisted, and I got my first taste of particle physics from textbooks in the 1960s and 1970s )

[ 22 February 2005: Message edited by: DrConway ]

[ 22 February 2005: Message edited by: DrConway ]

These guys aren't generated in a particle accelerator in this process; they're part of the secondary flux from the cosmic rays bashing the upper atmosphere, so that they constantly rain down on us from all over, about equally. Since they're charged particles and unstable, they are influenced readily by electric or magnetic fields and will decay into electrons after a couple of microseconds.