Physicists achieve record-breaking electron beam power and current

A team of physicists at the SLAC National Accelerator Laboratory, in Menlo Park, California, generated the highest-current, highest-peak-power electron beams ever produced. The team has published their paper in Physical Review Letters.

For many years, scientists have been finding new uses for high-powered laser light, from splitting atoms to mimicking conditions inside other planets. For this new study, the research team upped the power of electron beams, giving them some of the same capabilities.

The idea behind the newer, more powerful beams was pretty simple, the team acknowledges; it was figuring out how to make it happen that was difficult. The basic idea is to pack as much charge as possible into the shortest amount of time. In their work, they generated 100 kiloamps of current for just one quadrillionth of a second.

The work involved sending high-energy electron beams around an accelerator. In such devices, the electrons are pushed to higher speeds by powerful magnets—they ride on radio waves inside a vacuum. The team compares the electrons to a race car traveling around an oval track. In their case, the electrons were accelerated to speeds approximately 99% that of light. But when the electrons reach the turn on the track, they need to swerve, which slows them down. To take the turn more quickly, the race car (electron) must take a straighter path than has been the norm.

To simulate taking that straighter path, the researchers sent a string of electrons a millimeter long around the track. In such a configuration, the electrons in front moved along a less-steep part of the radio wave, which meant they came out of the turn with less energy—a phenomenon known as a chirp. The researchers then used magnets to make the electrons swerve left, then right, then left again, before they allowed them to return to their original path.

Then, because the magnets deflected more lower-energy electrons than they did those with higher energies, those with lower densities had to take a slightly longer path—and that longer path allowed the higher-energy electrons to catch up, resulting in compressing the string of electrons. The researchers then added another magnet that resulted in exchanging energy for light, which made the chirps even more dramatic.

They then ran the strings around the track multiple times, each time making the beam more powerful, but shorter. At its zenith, the pulse was just 0.3 micrometers long.

The research team suggests their technique could lead to new work involving chemical processes or perhaps producing new kinds of plasma or revealing more about the nature of empty space.

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