Researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in Germany have used a new approach to provide proton acceleration rates that are usually only possible in large facilities with large lasers.
The breakthrough could open up more economical and accessible medical applications, such as radiation treatments for cancer tumors.
Laser-based plasma acceleration is a promising technology that can provide similar or better results using a smaller system. By using lasers to move particles instead of powerful radio waves, the system provides particle acceleration in a more energy-efficient manner.
How does laser-plasma acceleration work?
In this approach, scientists use very short but high-intensity laser pulses and aim them at wafer-thin films. The light from the lasers heats the material so that the electrons jump out of their orbits while the atoms remain in place.
It separates the charges of the atom with negatively charged electrons and positively charged nuclei and creates a strong electric field between them, which lasts for a short time.
This field is strong enough to move proton pulses to energy levels over a distance of a few micrometers, compared to significantly longer distances in a conventional accelerator. The technology is still in its infancy, but proton energies of 100 MeV have been achieved using large laser systems.
Researchers at HZDR used a new approach to achieve similar proton energies, but with laser systems that produce pulses that are much smaller and shorter.
Novel approach
A pulse’s energy usually doesn’t kick in immediately; Instead, part of it runs forward. HZDR researchers see this property of lasers, usually looked down upon, to their advantage.
When a laser hits a plastic film in a vacuum chamber, it expands the film, making it thinner and hotter before eventually melting. However, this has a positive effect on the primary pulse because instead of reflecting the light, the film becomes transparent, allowing the pulse to penetrate deeper into the material than before.
This causes a further acceleration mechanism in the material, causing the protons in the material to accelerate further. In terms of energies, proton energies have nearly doubled from 80 MeV to 150 MeV, according to a company press release.
To achieve this feat, the researchers conducted a series of experiments to determine the optimal thickness of the film. In these experiments, they also discovered another characteristic of proton beams: a narrow energy distribution, meaning they have similar energies, a property that can be used in many applications.
Efficient applications
The approach developed by HZDR researchers allows for the delivery of high radiation doses in short intervals using a compact system. Until now, this has only been possible using large laser systems, severely limiting the availability of such treatments to large facilities.
These compact systems are easy to install and operate in small facilities, but they use less energy and are more economical to operate.
Alternatively, a laser-based system can produce short, intense neutron pulses that have many applications in science. The Press release HZDR researchers want to improve the technology and reach 200 MeV proton energy before then.
The research results are published in the journal Natural Physics.
About the editor
Ameya Paleja Ameya is a science writer based in Hyderabad, India. A molecular biologist at heart, he traded the micropipette to write about science during the pandemic and never wanted to go back. He likes to write about genetics, microbes, technology and public policy.
„Oddany rozwiązywacz problemów. Przyjazny hipsterom praktykant bekonu. Miłośnik kawy. Nieuleczalny introwertyk. Student.