Helmholtz-Zentrum Dresden-Rossendorf (HZDR) physicists directed the high power laser DRACO light diagonally and vertically onto a thin metal foil. This demonstration was conducted for the first time, wherein accelerated protons track the path of the laser light.
High-performance lasers are very promising and compact proton sources which could be used, for example, in future cancer therapies
Following the integration of this new data within the conventional model representing the laser particle acceleration, there is potential for attaining high proton energies. The results have been released in the scientific journal Nature Communications.
The high power laser DRACO’s ultra-short intense light and pulses can be considered as thin disks measuring 10 cm in diameter. By focusing one of these disks of light onto a thin metal foil, the extreme high electric and magnetic forces will draw the electrons that are negatively charged out of the foil. The positively-charged protons will be accelerated farther from the foil's surface with the help of electrons. The HZDR group’s results show that proton energies effective for treating cancers can be produced from such a short pulse laser. So, Dresden researchers started scrutinizing the process of particle acceleration.
By slightly tilting the angle of the thin light disk in accord to the axis of propagation, the electrons sense the rotation of the light disk and follow the path of the light striking the foil. Protons move rapidly along this direction and maintain their direction. Dresden physicists used the new observation of this directional dependence to study the acceleration process.
Key author, Karl Zeil identified another specific feature of ultra-short laser pulses. The initial phase is vital for the entire acceleration process. Efficient acceleration is observed during the first 30 fs, and similar to the laser pulse in length. A longer expansion phase follows the short acceleration phase that includes the formation of a uniform and symmetrical plasma cloud. During the first phase, the protons gain considerable energy and this in turn makes them quite fast, wherein they attain higher energies beyond the prediction capability of conventional models.
At present, the DRACO laser has attained a peak power of 150 TW, with an expected reach of 500 TW. A petawatt laser system called PENELOPE is under construction. The newly-built OncoRay center will be utilized for cancer research and therapy by incorporating the prototype of a high performance laser along with conventional proton accelerator.
Source: http://www.helmholtz.de/