DARPA Wants to Create Subatomic Particles That Can Peer Through Concrete

The United States' military has announced it is seeking to create powerful subatomic particle beams that would enable personnel to "see" through walls tens of yards thick and even peer deep underground.

Using radiation or particles to see through objects is something scientists have done for decades and across a variety of industries. Commercial aviation has made use of neutrons and gamma rays to scan the interiors of airfreight containers for illicit materials, and x-ray scans are widely used in healthcare to see the bone structure of our bodies.

However, none of the methods devised so far can see through particularly thick walls or map deep underground structures, which puts a limit on military uses.

A stock image shows an illustration of an atom. Subatomic particles called muons can be used to 'see' through thick solid objects. aleksandarnakovski/Getty

This is where high-energy particles known as muons come in, according to the U.S. military's Defense Advanced Research Projects Agency (DARPA).

Muons are subatomic particles that are similar to electrons but around 200 times heavier. At high energy, they can easily travel through hundreds of yards of solid rock.

The problem is that since muons are high-energy particles they require high-energy sources. Only two such sources are known: cosmic rays, which produce muons in Earth's upper atmosphere when they collide with atmospheric particles; and particle accelerators like the U.S. Fermilab accelerator or the Large Hadron Collider in Europe.

Such huge accelerators are not practical for military purposes, and while it is possible to harness muons created naturally via cosmic rays, it's a slow process that can take months to produce meaningful results.

According to Mark Wrobel, program manager for DARPA's MuS2 muon research program, lasers could provide the answer.

"Our goal is to develop a new, terrestrial muon source that doesn't require large accelerators and allows us to create directional beams of muons at relevant energies, from tens to hundreds of giga-electronvolts (GeV)—to either image or characterize materials," he said in a press release.

"Enabling this program is high-peak-power laser technology that has been steadily advancing and can potentially create the conditions for muon production in a compact form factor. MuS2 will lay the groundwork needed to examine the feasibility of developing compact and transportable muon sources."

The press release stated that muons could be used to scan whole buildings from the outside in order to detect "threat materials" on the inside. They could also be used to quickly map the location of tunnels hundreds of yards underground.

MuS2 is a four-year program split into two halves. In the first two years, military researchers will attempt to create 10 GeV muons before moving onto compact accelerator designs to produce 100 GeV muons.