Muons

Geological, Geophysics, Environmental & Geotechical Engineering

Date posted: 08/26/15

Jeanmarie Ryan reports that muons are elementary particles that are 200 times heavier than electrons. A muon decays to form either an electron or a positron. Muons are created when cosmic rays interact with earth atmosphere, and they inherit the high energy of these cosmic rays. Because of this, they can pass through dense objects, although they slow down while doing so. In the 1960s, Luis Alvarez came up with the idea of using muon tomography in archeology to study pyramids and ancient ruins. A muon detector is placed within or beneath the pyramid. It measures the energies and trajectories of the muons that reach it. Those data are compared to simulated data that were created based on the assumption that the structure is completely solid. Researchers use this to find places with different densities and create a 2D image of the pyramid. It allows archeologists to get a clear picture of the inside of ancient ruins without stumbling in and potentially disturbing things, and snakes. The higher the atomic number of a material, the more scattered muons will be after moving through it. The exact deflection of a muon is very sensitive to the atomic number of the material, so it can be used to detect materials with a high atomic number In 2005, scientists at Los Alamos National Laboratory were working on a way to use muon tomography to detect nuclear materials in large cargo containers. They would measure the angle of a muon before and after it passed through the container, and analyze its change in path. Today, the technology they developed is used by security companies to examine large cargo containers. In 2007, Hiroyuki Tanaka used muon tomography to study the Asama volcano in Japan. The technique is, for the most part, the same as the one used to study pyramids, but the detector is placed to the side of the volcano instead of under it. Hiroyuki found that there was a region of low-density rock at the bottom of the volcano crater.