In order to improve the quality of the electron beam, the laser heater vibrates the electron beam back and forth as the electron beam moves along the path of the infrared laser beam. Using beam configurations, the team found that they could produce higher-quality, more stable beams.
Scientists have come up with a way to improve the electron beam and produce brighter X-ray beams: add a ring to the beam. The team, which includes researchers from the department of energy's Stanford linear accelerator center and Stanford university, recently published their findings in the journal Physical Review Letters.

In X-ray free-electron lasers such as the coherent light source (LCLS) at the Stanford linear accelerator center, scientists compress an electron beam and accelerate it to near the speed of light, then oscillate it back and forth through a series of magnets to produce x-rays. These x-rays are then used to study biological, chemical and material samples, allowing scientists to create high-resolution images of how their molecular structures move.
The researchers found that these beams are most stable when they are long and smooth, like an American football, producing x-rays with more uniform and brighter wavelengths and producing higher-resolution images. But because the electrons repel each other as they are created in a vacuum, the beam is shorter and unpredictably uneven, "like a deflated football driven by a nail," said Sergio Carbajo, a scientist and lead researcher at the Stanford linear accelerator center.
Swell up a football
To solve this problem, the scientists used a device called a laser heater, a technique previously studied at the Stanford linear accelerator center by Zhirong Huang and Daniel Ratner. The laser heater swings the electron beam back and forth along the path of the infrared laser beam, allowing scientists to make longer, better-shaped beams. This process injects energy into the beam, says cabacho, "introducing a little bit of chaos early on to prevent more chaos." .
"The idea is that if we don't do anything to expand and smooth the spikes before we send the ball to the linear accelerator, the defects will expand and the beam quality will deteriorate," he said. But if we "heat" the electron at the beginning and change its energy distribution, we can adjust its shape to improve its mass as it reaches the end of the accelerator."