[en] We analyze a detailed model of a Bose-Einstein condensate (BEC) trapped in a ring optical resonator and contrast its classical and quantum properties to those of a Fabry-Perot geometry. The inclusion of two counterpropagating light fields and three matter field modes leads to important differences between the two situations. Specifically, we identify an experimentally realizable region where the system's behavior differs strongly from that of a BEC in a Fabry-Perot cavity, and also where quantum corrections become significant. The classical dynamics are rich, and near bifurcation points in the mean-field classical system, the quantum fluctuations have a major impact on the system's dynamics.

[en] We report on our experiments on laser-driven ion acceleration using fully isolated mass-limited spheres with a diameter down to 8 μm for the first time. Two-dimensional (2D) particle-in-cell (PIC) and hydro-code simulations were used to show that the pre-plasma at both the front and rear sides of the target strongly affect the efficiency of the ion acceleration. The mechanism of the plasma flow around mass-limited targets has not yet been identified for laser-driven ion acceleration. Our models indicate that this effect is the cause of the observed limitation to the ion-beam energy in both previous experiments and in our own.

[en] Laser plasma accelerators (LPA) offer an exciting possibility to deliver high energy, high brightness electrons beams in drastically smaller distance scales than is typical for conventional accelerators. As such, LPAs draw considerable attention as potential drivers for next generation light sources and for a compact linear collider. In order to asses the viability of an LPA source for a particular application, the brightness of the source should be properly characterized. In this paper, we present charge dependent transverse emittance measurements of LPA sources using both ionization injection and shock induced density down ramp injection, with the latter delivering smaller transverse emittances by a factor of two when controlling for charge density. The single shot emittance method is described in detail with a discussion on limitations related to second order transport effects. The direct role of space charge is explored through a series of simulations and found to be consistent with experimental observations. (paper)

[en] ⁹⁹Mo photonuclear yield was measured using high-energy electrons from Laser Plasma Accelerators and natural molybdenum. Spectroscopically resolved electron beams allow comparisons to Monte Carlo calculations using known ¹⁰⁰Mo(γ,n)⁹⁹Mo cross sections. Yields are consistent with published low-energy data, and higher energy data are well predicted from the calculations. The measured yield is (15±2)×10⁻⁵ atoms/electron (0.92±0.11 GBq/μA) for 25 mm targets at 33.7 MeV, rising to (1391±20)×10⁻⁵ atoms/electron (87±2 GBq/μA) for 54 mm/ 1.7 GeV, with peak power-normalized yield at 150 MeV. - Highlights: • ⁹⁹Mo yields with high energy electrons. • Increased yield and specific activity. • Non-reactor based ^99mTc production

[en] We introduce the equilibrium and non-equilibrium statistical hadronization picture of particle production in ultra-relativistic heavy ion collisions. We describe the related physical reaction scenarios, and show how these can lead to quark pair yield non-equilibrium. Using the SHARE1.2 program suite we quantitatively model particle yields and ratios for RHIC-130 run. We study how experimental particle ratios can differentiate between model scenarios, and discuss in depth the importance of hadronic resonances in understanding of hadron production processes. (author)

[en] © 2019 U.S. Government. Magnetic Vortex Acceleration (MVA) from near critical density targets is one of the promising schemes of laser-driven ion acceleration. 3D particle-in-cell simulations are used to explore a more extensive laser-target parameter space than previously reported in the literature as well as to study the laser pulse coupling to the target, the structure of the fields, and the properties of the accelerated ion beam in the MVA scheme. The efficiency of acceleration depends on the coupling of the laser energy to the self-generated channel in the target. The accelerated proton beams demonstrate a high level of collimation with achromatic angular divergence, and carry a significant amount of charge. For petawatt-class lasers, this acceleration regime provides a favorable scaling of the maximum ion energy with the laser power for the optimized interaction parameters. The megatesla-level magnetic fields generated by the laser-driven coaxial plasma structure in the target are a prerequisite for accelerating protons to the energy of several hundred mega-electron-volts.

[en] Dilute plasmas surrounding mass-limited targets provide sufficient current for influencing strong fields, which are built up due to the interaction of an intense and ultrafast laser pulse. Such situation occurs, where evaporation of the target surface is present. The high-intensity laser pulse interacts with the quasi-isolated mass-limited target and the spatial wings of the intensity distribution account for ionization of the ambient plasma. A fast change of strong electrical fields following intense laser irradiation of water droplets (16 micron diameter) has been measured with proton imaging. An analytical model explains charge transport accounting for the observation.

[en] Applying a 21-channel Thomson spectrometer setup has revealed further insight to the connection between spatial and spectral beam characteristic of laser accelerated protons. Analyzing the central emission cone (plus/minus 3 degree) shows an increasing beam divergency for protons with increasing kinetic energies. This holds for protons emitted from the same source area at the target surface. The whole beam is a well ordered system with a clear functional dependence of trajectories on proton energy. This is a consequence of the source dynamics which is determined by the sheath development in time. Thus laser-driven ion beams can be advantageously manipulated for further propagation to an experiment. We demonstrate this capability with a magnetic quadrupole and obtain a nearly parallel and monochromatized beam. Furthermore we set our achievements in beam production efficiency into context with other laser systems and demonstrate the potential of very-thin target foils.

[en] Laser-driven ion acceleration is capable of generating ion beams of MeV energy exhibiting unique attributes such as ultralow emittance. Research is still focusing on fundamental laser-target interactions to control further beam attributes. In this Letter we present the observation of directional ion acceleration of irradiated spherical targets through proton imaging. This feature, together with an earlier observed quasimonoenergetic proton burst makes spherical targets extremely attractive candidates for high quality, high repetition rate sources of laser accelerated particles.

[en] Due to the envisioned advantages of mass-limited targets for laser driven ion beams, which are high efficiency and high cut-off energies, their field dynamics are of special interest. Micro-water droplets can be used as mass-limited targets with a high repetition rate. Our investigations show that the surrounding dilute plasma of such liquid spheres influences the interaction. We review our experimental findings together with computer simulations and conclude on the different processes in electron transport and related acceleration fields for mass-limited targets and foils, respectively.