At the Helmholtz center GSI, PHELIX (Petawatt High Energy Laser for heavy Ion eXperiments) has been commissioned for operation in stand-alone mode and, in combination with ions accelerated up to an ...energy of 13 MeV/u by the heavy ion accelerator UNILAC. The combination of PHELIX with the heavy-ion beams available at GSI enables a large variety of unique experiments. Novel research opportunities are spanning from the study of ion–matter interaction, through challenging new experiments in atomic physics, nuclear physics, and astrophysics, into the field of relativistic plasma physics.
We report on the dynamics of ultrafast heating in cryogenic hydrogen initiated by a ≲300 fs, 92 eV free electron laser x-ray burst. The rise of the x-ray scattering amplitude from a second x-ray ...pulse probes the transition from dense cryogenic molecular hydrogen to a nearly uncorrelated plasmalike structure, indicating an electron-ion equilibration time of ∼0.9 ps. The rise time agrees with radiation hydrodynamics simulations based on a conductivity model for partially ionized plasma that is validated by two-temperature density-functional theory.
Creating non-equilibrium states of matter with highly unequal electron and lattice temperatures (T(ele)≠T(ion)) allows unsurpassed insight into the dynamic coupling between electrons and ions through ...time-resolved energy relaxation measurements. Recent studies on low-temperature laser-heated graphite suggest a complex energy exchange when compared to other materials. To avoid problems related to surface preparation, crystal quality and poor understanding of the energy deposition and transport mechanisms, we apply a different energy deposition mechanism, via laser-accelerated protons, to isochorically and non-radiatively heat macroscopic graphite samples up to temperatures close to the melting threshold. Using time-resolved x ray diffraction, we show clear evidence of a very small electron-ion energy transfer, yielding approximately three times longer relaxation times than previously reported. This is indicative of the existence of an energy transfer bottleneck in non-equilibrium warm dense matter.
We have employed fast electrons produced by intense laser illumination to isochorically heat thermal electrons in solid density carbon to temperatures of ∼10,000 K. Using time-resolved x-ray ...diffraction, the temperature evolution of the lattice ions is obtained through the Debye-Waller effect, and this directly relates to the electron-ion equilibration rate. This is shown to be considerably lower than predicted from ideal plasma models. We attribute this to strong ion coupling screening the electron-ion interaction.
We present a new method for parametric amplification of soft-X-ray radiation. The laser-driven amplifier is based on parametric stimulated emission and is seeded with high-order-harmonic radiation ...generated in the same medium. The exponential increase of the soft-X-ray yield with increasing atomic density is experimentally demonstrated for two different sets of laser parameters. A small-signal gain up to 8 x 103 is obtained in both experiments at about 40 eV in argon using 350-fs-long laser pulses and with 6-fs-long ones at about 260 eV in helium, respectively. This new scheme reduces the pumping threshold for lasing with a comparable conversion efficiency into the millijoule level, which is about two orders of magnitude smaller compared with the conventional plasma X-ray lasers. With a simple model, we can estimate the necessary experimental conditions for identifying the spectral range and the magnitude of the maximum gain, which are in reasonable agreement with our measurements. PUBLICATION ABSTRACT
Experimental results of a two-stage Ni-like Ag soft X-ray laser operated in a seed-amplifier configuration are presented. Both targets were pumped applying the double-pulse grazing incidence ...technique with intrinsic travelling wave excitation. The injection of the seed X-ray laser into the amplifier target was realized by a spherical mirror. The results show amplification of the seed X-ray laser and allow for a direct measurement of the gain lifetime. The experimental configuration is suitable for providing valuable input for computational simulations.
We report here more than 50% coverage of the XUV spectral range between 18 nm and 35 nm by tuning the high-order harmonics generated by a fixed frequency Nd:Glass laser system. The tuning range ...achieved is suitable to seed Ni-like Y, Zr and Mo soft X-ray lasers.
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