Computational Radiation Physics

Research Topics

• Advanced Radiation Sources

  Our main research topic is the theory of laser-driven radiation sources. We study these sources by building analytic models and complex simulations to better understand and control the properties of these sources.

  In order to increase our understanding of these sources, we have to be able to gain insight into the dynamical behaviour of large many-particle systems. High-intensity lasers can ionise matter, forming a new state of matter called a plasma. This means that they can rip matter apart, separating the positively charged atomic nuclei, so called ions, from their negatively charged electrons. This charge separation can create strong electric fields which in turn can be used to accelerate charged particles.

  Physical Models of such a plasma need to take into account a variety of physical processes that can occur during the evolution of the plasma. Important processes include the ionisation of atoms by the laser pulse or by collisions with other particles but also radiation emitted by charged particles and collisions between particles.

  These processes can happen on various time and length scales. This challenges both simulation techniques and theoretical models of these processes. One of our projects is PIConGPU, an implementation of the Particle-in-Cell algorithm for GPU clusters.

  Our current research interests are:

  - Laser-driven acceleration of ion beams
  - Laser-driven acceleration of electron beams
  - Laser-driven X-ray sources

• Complex, large-scale simulations

  Realistic simulations of the interaction of high-power laser pulses with matter require to compute the trajectories of several million to a few billion charged particles in electromagnetic fields that strongly vary in space and time. It is therefore important, to use high performance computers with several hundred to thousands of processors. For this we are developing new parallel computing schemes to reduce the simulation time and thus the time the scientists have to wait for results.

  Besides our physics research program we thus deal with information technology topics such as

  - Massively-parallel simulations on new compute hardware such as GPUs
  - Advanced data analysis techniques (Big Data, Visual Analytics)

• Combining accelerator physics and laser physics

  Besides working on new acceleration schemes using lasers, we are interested in making use of standard accelerator techniques in combination with these new sources. For many applications, transport or focusing of laser-driven particle beams is essential.

  Our work currently focuses on the following topics in accelerator physics:

  - Laser cooling of relativistic ion beams
  - Compact beam transport systems (permanent magnet quadrupoles, pulsed magnets)