Lights, Camera, Nanosecond Action!

Picturing the Bomb


High-speed still photography dates back decades, most famously to the spectacular milk-drop and bullet-through-apple photography of Harold Edgerton, who invented the strobe in 1931. Very-high-speed movie photography started later, and came into its own as a scientific tool in the birthing room of the atomic bomb. Its purpose has been not so much to freeze a moment in time, but to glimpse what changes from one infinitesimal moment to the next. It begins at the point at which our familiarity with ordinary time-splitting ends, a point not far past the 100 milliseconds that constitute the blink of an eye. Ordinary cameras freeze time, but crudely and in big chunks. Movie cameras fool the eye into seeing continuous motion when only 24 still frames are presented per second. We know from snapshot experience that the 1/500th or 1/1,000th shutter setting will stop most human motion. Beyond this realm—into micro- and nano- dimensions of time, let alone across exotic picosecond and femtosecond frontiers—the very fast is almost as invisible to us as the extremely small. The eye does not register, and the conventional camera does not record.



High-speed movie cameras do record, but many of the most arresting picture sequences taken with such equipment have not been seen—except by a few researchers who might go to jail if they released them to the public. Secret weapons research is in the DNA of this business. During the final stages of the Manhattan Project, Los Alamos scientists hit a brick wall. Sid Nebeker recalls hearing an account of this little-known chapter in history from Berlyn Brixner, a technician who still lives quietly, at the age of 96, in Los Alamos. The scientists who were developing the theoretical and practical framework for implosion weapons hadn’t been able to get them to work properly. There was much disagreement about whether that failure meant that the entire concept was flawed, or merely that the execution needed adjustment—perhaps, for example, the shape of the explosive “lens” that was supposed to trigger the nuclear reaction needed to be modified. Brixner was enlisted to capture the footage that would allow the scientists to see what was happening.



The camera Brixner used was an early rotating-mirror design. A mirror in the center of a cylindrical housing projected images in series from the camera’s main lens to the film, which was seated along the inside edge of the housing. The light traveling to each frame passed through its own set of lenses en route. The mirror acted as a sort of shutter, flashing a discrete image onto the film and forming a discrete frame. This design had been adapted from work done by C. David Miller, an engineer who worked at NASA’s predecessor, NACA. “With Miller’s concept of forming the image on a rotating mirror and putting a sequence of lenses between mirror and film, you can jump to 1, 2 or 5 million images per second,” says Sid Nebeker. “Extremely crisp ones at that.”