Laser Ion Acceleration
The acceleration of intense ion pulses on a few micrometers to 10 MeV energies is possible when light pulses from a short-pulse laser are focused on thin solid-state targets. In the interaction, the laser energy is primarily transferred to relativistic electrons whose collective fields result in the acceleration of the ions. The work on the laser ion acceleration at the HZDR is designed to diagnose and understand the time scales of only a few 10 femtosecond processes, to explore new regimes and, ultimately, to improve control of the beam parameters so that these unrivaled compact accelerators for applications.
Bachelor, Master and PhD theses available!!
Investigation of the laser-plasma interaction
The first step to control laser-plasma driven ion beams is a deep understanding of the interaction of the laser with the plasma. In our experiments laser pulses of the Draco Laser are focused onto targets and hence relativistic intensities of up to 1021 W/cm2 are reached which correspond to possible acceleration fields in the range of MV/µm. In order to gain profound insights of the processes inside the hot plasmas we use different additional probe pulses which are synchronized to the high intensity main laser pulse. Depending on whether surface or volume effects are analyzed, the probe pulses are in the optical wave length range or in X-rays are used. However, the complex dynamic of the laser plasma interaction can often only be understood using extensive large scale computer simulation. Together with the computational radiation physiks group we investigate the influence of the different experimental parameters, try to identify new acceleration mechanisms in order to be able to even predict experimental results in the future.
Direct observation of prompt pre-thermal laser ion sheath acceleration, K. Zeil et al., Nature Communications 3, 874 (2012)
Experimental observation of transverse modulations in laser-driven proton beams, J. Metzkes et al., New Journal of Physics 16 (2014)
Reflective optical probing of laser-driven plasmas at the rear surface of solid targets, J. Metzkes et al., Plasma Physics and Controlled Fusion 58 (2016)
It’s the target!
Besides the control of the laser parameter, the choice of the right laser target is of outmost importance for the quality of the plasma driven particle beam. Thus, the conversion of the laser to particle energy, but also further basic properties as the spatial distribution of the collective fields can be influenced by the target composition and its geometry. In collaboration with national and international partners we conduct experiments using different target types, such as thin foils with thicknesses in the nanometer range (Ohio State University) or special nanostructured surfaces (University of Milan) as well as jets of frozen Hydrogen as an example of a renewable target (SLAC, XFEL, CEA). Together with the Institute of Ion Beam Physics and Materials Research we develop tiny three-dimensional target structures in the micro-meter range which are produced using state-of-the art semi-conductor technology.
Robust energy enhancement of ultrashort pulse laser accelerated protons from reduced mass targets, Karl Zeil et al., Plasma Physics and Controlled Fusion 56 (2014)
Proton beams for cancer therapy
For many physicians, particle therapy is considered to be more effective and more gentle than conventional radiotherapy with X-rays. The principle: Charged particles - mostly protons, but also carbon ions - are accelerated to high energies and applied to the tumor. They penetrate deeply into the tissue and lose the main part of their energy at a certain depth, which depends on their original velocity. This is the goal of any radiotherapy: maximum dose in the tumor, minimal dose in the surrounding healthy tissue.
Compact laser plasma accelerators could represent an interesting alternative to present conventional accelerator systems. In addition to the proton energies which need to be sufficiently high for sufficient penetration in to the tissue, a very high stability of the radiation properties must be achieved. In order to characterize the effect of the intense pulsed radiation on biological systems, we conduct interdisciplinary radiobiological studies together with OncoRay (project OnCOOPtics). The principle suitability of the laser plasma source can be demonstrated using the dose-controlled irradiation of living cells or tissues.
A suitable beam transport system is of outmost importance. In general, the intense laser-accelerated ion pulse has a broad energy distribution as well as a relatively large energy-dependent beam divergence angle (about 20°). In cooperation with the Dresden High Magnetic Field Laboratory, OncoRay and the LIGHT Collaboration, we are investigating compact pulsed magnetic solenoid lenses for ion beam collimation and energy selection in order to develop a pulsed laser plasma driven ion beam delivery for future application.
Dose controlled irradiation of cancer cells with laser accelerated proton pulses, K. Zeil et al., Applied Physics B 110, 437 (2013)
Focusing and transport of high-intensity multi-MeV proton bunches from a compact laser-driven source, S. Busold et al., Phys. Rev. STAB 16, 101302 (2013)
A compact solution for ion beam therapy with laser accelerated Protons, Umar Masood et al., Applied Physics B 117 (2014)