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We propose to produce neutron-rich nuclei in the range of the astrophysical r-process (the rapid neutron-capture process) around the waiting point N=126 (Kratz et al. in Prog. Part. Nucl. Phys. 59:147, ; Arnould et al. in Phys. Rep. 450:97, ; Panov and Janka in Astron. Astrophys. 494:829, ) by fissioning a dense laser-accelerated thorium ion bunch in a thorium target (covered by a polyethylene layer, CH), where the light fission fragments of the beam fuse with the light fission fragments of the target. Using the 'hole-boring' (HB) mode of laser radiation pressure acceleration (RPA) (Robinson et al. in Plasma Phys. Control. Fusion 51:024004, ; Henig et al. in Phys. Rev. Lett. 103:245003, ; Tajima et al. in Rev. Accel. Sci. Technol. 2:221, ) using a high-intensity, short pulse laser, bunches of Th with solid-state density can be generated very efficiently from a Th layer (ca. 560 nm thick), placed beneath a deuterated polyethylene foil (CD with ca. 520 nm), both forming the production target. Th ions laser-accelerated to about 7 MeV/u will pass through a thin CH layer placed in front of a thicker second Th foil (both forming the reaction target) closely behind the production target and disintegrate into light and heavy fission fragments. In addition, light ions (d,C) from the CD production target will be accelerated as well to about 7 MeV/u, also inducing the fission process of Th in the second Th layer. The laser-accelerated ion bunches with solid-state density, which are about 10 times more dense than classically accelerated ion bunches, allow for a high probability that generated fission products can fuse again when the fragments from the thorium beam strike the Th layer of the reaction target. In contrast to classical radioactive beam facilities, where intense but low-density radioactive beams of one ion species are merged with stable targets, the novel fission-fusion process draws on the fusion between neutron-rich, short-lived, light fission fragments from both beam and target. Moreover, the high ion beam density may lead to a strong collective modification of the stopping power in the target by 'snowplough-like' removal of target electrons, leading to significant range enhancement, thus allowing us to use rather thick targets. Using a high-intensity laser with two beams with a total energy of 300 J, 32 fs pulse length and 3 μm focal diameter, as, e.g. envisaged for the ELI-Nuclear Physics project in Bucharest (ELI-NP) (, ), order-of-magnitude estimates promise a fusion yield of about 10 ions per laser pulse in the mass range of A=180-190, thus enabling us to approach the r-process waiting point at N=126. First studies on ion acceleration, collective modifications of the stopping behaviour and the production of neutron-rich nuclei can also be performed at the upcoming new laser facility CALA (Center for Advanced Laser Applications) in Garching. [ABSTRACT FROM AUTHOR]

High power short-pulse lasers with peak powers presently reaching Terawatts and even Petawatt levels routinely reach focal intensities of 1018 - 1021 W/cm². These lasers are able to produce a variety of secondary radiation, from relativistic electrons and multi-MeV/nucleon ions to highenergetic X-rays and γ-rays. In many laboratories world-wide large resources are presently devoted to a rapid development of this novel tool of particle acceleration, targeting nuclear, fundamental and high-field physics studies as well as various applications e.g. in medical technology for diagnostics and tumor therapy. Within the next 5 years a new EU-funded large-scale research infrastructure (ELI: Extreme Light Infrastructure) will be constructed, with one of its four pillars exclusively devoted to nuclear physics based on high intensity lasers (ELI-Nuclear Physics, to be built in Magurele/Bucharest). There the limits of laser intensity will be pushed by three orders of magnitude to yet unprecedented 1024 W/cm². [ABSTRACT FROM AUTHOR]

Electrons have been accelerated from ultra-thin diamond-like carbon (DLC) foils by an ultrahigh-intensity laser pulse. A distinct quasi-monoenergetic electron spectrum peaked at 30 MeV is observed at a target thickness as thin as 5 nm which is in contrast to the observations of wide spectral distributions for thicker targets. At the same time, a substantial drop in laser-accelerated ion energies is found. The experimental findings give first indication that relativistic electron sheets can be generated from ultra-thin foils which in future may be used to generate brilliant X-ray beams by the coherent reflection of a second laser. [ABSTRACT FROM AUTHOR]

We report on experimental studies of divergence of proton beams from nanometer thick diamond-like carbon foils irradiated by a linearly polarized intense laser with high contrast. Proton beams with extremely small divergence (half angle) of 2° are observed in addition with a remarkably well-collimated feature over the whole energy range, showing one order of magnitude reduction of the divergence angle in comparison to the results from μm thick targets. Similar features are reproduced in two-dimensional particle-in-cell simulations with parameters representing our experiments, indicating a strong influence from the electron density distribution on the divergence of protons. Our comprehensive experimental study reveals grand opportunities for using nm foils in experiments that require high ion flux and small divergence. [ABSTRACT FROM AUTHOR]

A significant deceleration effect on a stored coasting ion beam by a continuous-wave laser light was observed in the Schottky-noise spectrum during the laser experiments with lithium-like oxygen ion beams stored at a relativistic energy of 275.7 MeV/u at the heavy-ion storage ring CSRe in Lanzhou, China. The observed deceleration range of the laser (Δ p / p ≈ 5. 7 × 1 0 − 6 ) is much broader than the expected capture range (Δ p / p ≈ 3. 6 × 1 0 − 8 ), as calculated from the natural linewidth of the O 5 + ion's electronic transition (2 S 1 / 2 − 2 P 1 / 2). In order to explain this huge deviation, a phase space tracking code has been developed to investigate the interaction between the stored coasting ion beam and the laser light. Simulations reveal that the deceleration range of the typically narrow CW laser force is highly enlarged by taking into account the transverse betatron oscillation of the ions with larger emittance and the angular misalignment of the laser light direction. The experimental observation is well described by the systematic simulations. The present work is crucial for forthcoming laser cooling and precision laser spectroscopy experiments and simulations on heavy highly charged ions at the CSRe and the future facility HIAF. [ABSTRACT FROM AUTHOR]