Magnetized laser-produced plasmas are central to many novel laboratory astrophysics and inertial confinement fusion studies, as well as in industrial applications. Here we provide the first complete description of the three-dimensional dynamics of a laser-driven plasma plume expanding in a 20 T transverse magnetic field. The plasma is collimated by the magnetic field into a slender, rapidly elongating slab, whose plasma-vacuum interface is unstable to the growth of the "classical", fluid-like magnetized Rayleigh-Taylor instability.The combination of high-power lasers with externally applied high-strength magnetic fields of up to kT [1,2] has been seminal in the development of many recent applications in laboratory astrophysics [3][4][5][6][7], in novel concepts in laser-[8-10] and magnetically-driven [11,12] inertial confinement fusion physics, and in industrial applications [13,14]. Beside understanding the dynamics of the plasma expansion across a magnetic field, of particular importance is to grasp the nature of rapidly growing instabilities which may develop and profoundly modify the morphology and characteristics of these plasmas. Indeed, the presence of striations and flutes have often been associated with the development of instabilities and in particular with the lower hybrid drift instability (LHDI) or one of its variants [15][16][17]. In addition, anomalous resitivity driven by the LHDI [18,19] can also affect the plasma microscopically, with potentially important consequences on magnetic field diffusion and the growth of other instabilities. Among those, the magnetic Rayleigh-Taylor instability (MRTI) [20,21] is known to play a key role on the dynamics of laboratory [22], as well as astrophysical plasmas [23,24]. So far however, it has not been isolated in laser-produced high energy density plasmas.A major parameter affecting the stability and dynamics of these plasmas is the relative direction of the applied magnetic field with respect to the plasma expansion axis. While for an aligned magnetic field the plasma is collimated into an axisymmetric, stable jet-like flow [4,5], for a transverse magnetic field both stable[25] and unstable flows [26] were observed and a clear understanding of the plasma evolution is still missing.Here, we provide the first complete description of the three-dimensional dynamics of a laser-driven plasma plume in a transverse 20 T magnetic field. We show that the plasma is collimated into a slender, rapidly expanding slab, and demonstrate that under these conditions, the growth of flute-like, interchange modes at the plasma-vacuum interface that extend in the form of spikes into the vacuum is due to the classical, fluid-like, magnetic Rayleigh-Taylor instability (MRTI). Interestingly, we find that to recover quantitatively in the simulations the penetration of these spikes into the vacuum, a subgrid-scale model of anomalous resistivity needs to be included. This anomalous resistivity could be induced by the micro-turbulence generated by the LHDI, which for our plasma condition...

Fractional derivatives of arbitrary order are incorporated into a model nonlinear equation in order to simulate the absorption mechanism in a finite frequency domain. That makes it possible to take into account a power dependence of the absorption coefficient on the frequency at any real degree. The model gives a mathematical description of a large set of well-known absorption mechanisms. The method is applied to calculate weakly nonlinear oscillations in a nonrigid tube. As a result, the value of the absorption coefficient and its dependence on the frequency are found based on experimental data.

High resolution X-ray imaging is crucial for many high energy density physics (HEDP) experiments. Recently developed techniques to improve resolution have, however, come at the cost of a decreased field of view. In this paper, an innovative experimental detector for X-ray imaging in the context of HEDP experiments with high spatial resolution, as well as a large field of view, is presented. The platform is based on coupling an X-ray backligther source with a Lithium Fluoride detector, characterized by its large dynamic range. A spatial resolution of 2 µm over a field of view greater than 2 mm2 is reported. The platform was benchmarked with both an X-ray free electron laser (XFEL) and an X-ray source produced by a short pulse laser. First, using a non-coherent short pulse laser-produced backlighter, reduced penumbra blurring, as a result of the large size of the X-ray source, is shown. Secondly, we demonstrate phase contrast imaging with a fully coherent monochromatic XFEL beam. Modeling of the absorption and phase contrast transmission of X-ray radiation passing through various targets is presented.

We present new diagnostics for use in optical laser pump - X-ray Free Electron Laser (XFEL) probe experiments to monitor dimensions, intensity profile and focusability of the XFEL beam and to control initial quality and homogeneity of targets to be driven by optical laser pulse. By developing X-ray imaging, based on the use of an LiF crystal detector, we were able to measure the distribution of energy inside a hard X-ray beam with unprecedented high spatial resolution (∼1 μm) and across a field of view larger than some millimetres. This diagnostic can be used in situ, provides a very high dynamic range, has an extremely limited cost, and is relatively easy to be implemented in pump-probe experiments. The proposed methods were successfully applied in pump-probe experiments at the SPring-8 Angstrom Compact free electron LAser (SACLA) XFEL facility and its potential was demonstrated for current and future High Energy Density Science experiments.

The response of lithium fluoride (LiF) crystal detectors to monochromatic X-rays is measured in the multi-kilo-electron-volt range. This response, as a function of the X-ray dose, is independent of photon energy with no saturation level found. The response, as a function of the incident energy flux, is found to increase for photons of lower energy due to the differing attenuation lengths of X-ray photons within the crystal. Small differences are seen between different confocal microscopes used to scan the data, suggesting the need for absolute calibration. The spatial resolution of the LiF is also measured (1.19–1.36 μm) and is found to be independent of incident photon energy. Finally, a photometric study is performed in order to assess the feasibility of using these detectors at current X-ray free electron laser and laser facilities worldwide.