Please activate JavaScript!
Please install Adobe Flash Player, click here for download

discovered 02_2012

FOCUS// The HZDR Research Magazine WWW.Hzdr.DE 26 27 tick more slowly than those of the other surfers. That means each electron “sees“ the laser wave at a different point in time – depending on its position on the wave. This relativistic effect may not tally with common sense, but it cannot be ignored when correctly predicting the energy of laser- accelerated particles. For the predecessors of DRACO and PENELOPE, the textbook predictions still match the experimental results very nicely. To continue our metaphor, the wave the electrons are surfing on is still so flat that relativistic effects hardly come into play at all. If Thomas Kluge’s model is correct, however, then future high-power laser systems capable of producing laser intensities tens to hundreds of times greater will experience an even bigger gap between the experimentally measured temperatures and the temperatures predicted by the conventional models. Since hot electrons are the intermediaries in laser-ion acceleration, in that they transfer energy from the laser to the ions, it is crucial that we gain a better understanding of these hot electrons and their behavior in the electron cloud. Accurate predictions at last The extended model for laser-electron interactions, which physicist Thomas Kluge developed with the support of Michael Bussmann, head of the junior group “Computational Radiation Physics”, now allows laser systems to be built on the correct power scale for producing the ion energies needed for future applications. “Our new insights improve on the decades-old models. For one thing, they provide an explanation for previous measurements and, for another, they allow us to make accurate predictions for optimizing future experiments,” Michael Bussmann says. Not resting on their laurels, the team from Dresden has already moved on. The two physicists are figuring out exactly how energy is transferred from electrons to ions in order to gain a better understanding of laser-ion acceleration. They are delving deep into fundamental issues of laser-matter interactions knowing that, one day, their work will advance the clinical use of laser accelerators in future cancer research and therapy. Literature T. Kluge, T. E. Cowan, A. Debus, U. Schramm, K. Zeil, M. Bussmann: “Electron temperature scaling in laser interaction with solids”, in Physical Review Letters, vol. 107, p. 20 (DOI: 10.1103/PhysRevLett.107.205003) ELECTRON CLOUD: Each individual electron “sees“ the laser wave at a different point in time. But even though it is difficult to conceive of this relativity effect, it is essential for the exact determination of energy from laser-accelerated particles. Contact _ Institute of Radiation Physics at HZDR Prof. Ulrich Schramm