LASER-ION ACCELERATO · Optimal ion acceleration at the interaction of super-intense profiled laser pulse with mass limited targets

Optimal ion acceleration at the interaction of super-intense profiled laser pulse with mass limited targets.

Recently an interest has developed in the ion acceleration by high intensity short pulse lasers up to tens-MeV energies which has a large number of potential applications: for the development of a compact neutron source, isotope production, activation experiments, new methods in nuclear medicine, relativistic ion beam production and "Fast igniter" concept with light ions for ICF as well as - and especially important for the MBI strategy- proton radiography to image field structures in matter and ceation of warm dense matter. Unlike traditional sources that generate proton pulses longer than several nanoseconds, the laser acceleration technique allows one to generate particle pulses that are a few orders of magnitude shorter and have a peak current exceeding few kA. Therefore, this method offers a unique opportunity for fundamental research in the field of nuclear physics on ps time scale. The commonly recognized effect responsible for ion acceleration is the charge separation in plasma due to high-energy electrons driven by the laser inside the target or/and an inductive electric field as a result of the self-generated magnetic field. A direct laser-ion interaction or Radiation Pressure Acceleration (RPA) has been discussed for extremely high laser intensities. On behalf of the laser, improving the temporal pulse contrast by several orders of magnitude has enabled experiments with extremely thin foils and therewith the study of new acceleration mechanisms like RPA. Regarding the target, so-called mass-limited targets (MLT) have become a major point for investigations since prediction an energy increase compared to foil targets of the same thickness. The crucial feature of MLT is the limited size which leads to a confinement and recirculation of plasma electrons resulting in additional interaction with the laser pulse, which changes their energy distribution function and enhances ion energy [1]. Our basic interest in the project was to investigate the mechanisms of ion acceleration in the interaction of laser pulse with MLT depending on laser pulse and target parameters and formulate practical recommendations for optimization of ion yield for the given laser pulse characteristics (intensity etc.). Collaboration with graduate and postgraduate students has been done who take part in this work. This includes help in formulation of their tasks in this area and consultations have been done. Students in their training process were learning by the method of scientific touch and personal supervision. In all of these activities postgraduate students played an active role as part of their training. The learning process included understanding principles of methodology and special analyzing software. Training for graduate student taking part in computer simulations has been done. In particular a DAAD student has been supervised for about two month. The given lecture course on "Introduction to Laser Plasma" for postgraduate students played an active role as part of their training. The obtained results have been summarized, reported on 22 international meetings and published in 15 papers.

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