Tinkering with the proton beam

© Jens Meyer/ University of Jena

Here, two scientists are preparing an experiment using the POLARIS laser at the University of Jena. This should help to make it easier to generate the proton beams required for medical therapies in the future

Proton therapy is used in medicine to treat tumors in sensitive areas of the body, such as the brain or eyes. The positively charged atomic nucleus building blocks are extremely accelerated and directed precisely into the tumor tissue, which is destroyed in the process. So far, however, this efficient treatment method, which is gentle on healthy tissue, has required large accelerator facilities, which is why the method is only available in special centers.

But scientists have been working on producing proton beams with smaller laser systems for some time. To do this, a high-intensity laser pulse is shot at a thin metal foil and generates a plasma on its front side. This creates a strong electrical field on the back of the foil, which propels protons away from the foil surface and accelerates them greatly – a proton beam is created.

The problem, however: “The proton radiation generated by means of laser-plasma interaction has simply not been high enough in energy so far, even though the previous theoretical models predict that the prerequisites for this would actually be met,” explains Malte Kaluza from the Friedrich Schiller University Jena . While energies of more than 200 megaelectron volts would be necessary for radiation therapy, laser-accelerated protons have not yet achieved half of this energy.

To change this, Kaluza and his colleagues spent months conducting experiments at the POLARIS laser at the Institute of Optics and Quantum Electronics to investigate which parameters play a role in laser-induced proton acceleration. From this, they were able to derive a number of conditions through which the energy yield for the proton beam can be maximized. These findings could now pave the way to new, more compact proton beam generators for medicine.


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