Imaging shock waves via proton snapshots.

Obtaining an X ray of a decayed tooth is a routine procedure available at any dentist's office. In contrast, imaging the shock waves produced within an explosion requires a special type of radiography involving high-energy protons.

Researchers at the Los Alamos (N.M.) National Laboratory have demonstrated for the first time that proton radiography can be used to probe the interior of not only a static object but also a turbulent, rapidly evolving system.

According to Los Alamos scientists, proton radiography represents a potentially useful technology in a broad program aimed at ensuring the safety and reliability of the U.S. nuclear weapons stockpile, particularly as weapons components get older (SN: 10/19/96, p. 254).

In conventional radiography, X rays traverse an object and leave on film a pattern of light and dark areas that corresponds to the composition, density, and thickness of the object. However, X rays tend to bounce around within a material, making it difficult to obtain a sharp image in a brief time. Protons don't scatter as much and can be generated more efficiently than X rays.

Last April, the team detonated about 3 ounces of a powerful explosive inside a chamber 4 feet across and obtained an image of the shock wave generated a few millionths of a second after ignition. Earlier this month, the researchers used a new electronic camera to capture a sequence of images, which they combined into a short movie, says James E. Rickman of Los Alamos.