Laser-Produced Proton Beams Open New Research Areas

Recent proton beam experiments using high-intensity lasers have unveiled a new way to heat material and create novel states of matter in the laboratory. This advance could lead to medical applications and even offer insight into planetary science.

Using the Trident subpicosecond laser at Los Alamos National Laboratory, researchers generated and focused a proton beam using a cone-shaped target. The protons were found to have unexpectedly curved trajectories due to the large electric fields in the beam. A sheath electric field also channeled the proton beam through the cone tip, substantially improving the beam focus.

The Trident laser at Los Alamos National Laboratory. (Image: LLNL)

The experiments are providing a new understanding of the physics involved in proton focusing. This knowledge will affect how proton beams are used in the future. For example, a proton beam could be focused on a solid density or compressed material, creating millions of atmospheres of pressure. Scientists would be able to study the properties of warm, dense matter found in the interior of giant planets such as Jupiter.

“This work has given a new direction to the conventional thinking of proton beam focusing in short-pulse laser-matter interaction,” said Farhat Beg of the University of California, San Diego, who led his students’ participation in the experiments. “Surely it will impact heating of precompressed materials to temperatures observed at the core of the sun and any future applications in proton oncology using high-intensity lasers.”

Laser-produced proton beams also are making an impact on medical applications such as isotope production for positron emission tomography and proton oncology, said the researchers.

Along with those from the Los Alamos lab and UCSD, the experiments were carried out by researchers at Lawrence Livermore National Laboratory; at Hemoltz-Zentrum Dresden-Rossendorf and the Technical University of Darmstadt, both in Germany; and at San Diego-based General Atomics.

The research appears in the December issue of Nature Physics.

For more information, visit: www.llnl.gov