Deep understanding of the impact of photon polarization on pair production is essential for the efficient generation of laser-driven polarized positron beams and demands a complete description of polarization effects in strong-field QED processes. Employing fully polarization-resolved Monte Carlo simulations, we investigate correlated photon and electron (positron) polarization effects in the multiphoton Breit–Wheeler pair production process during the interaction of an ultrarelativistic electron beam with a counterpropagating elliptically polarized laser pulse. We show that the polarization of e-e+ pairs is degraded by 35% when the polarization of the intermediate photon is resolved, accompanied by an ∼13% decrease in the pair yield. Moreover, in this case, the polarization direction of energetic positrons at small deflection angles can even be reversed when high-energy photons with polarization parallel to the laser electric field are involved.

Ultra-intense short-pulse light sources are powerful tools for a wide range of applications. However, relativistic short-pulse lasers are normally generated in the near-infrared regime. Here, we present a promising and efficient way to generate tunable relativistic ultrashort pulses with wavelengths above 20 µm in a density-tailored plasma. In this approach, in the first stage, an intense drive laser first excites a nonlinear wake in an underdense plasma, and its photon frequency is then downshifted via phase modulation as it propagates in the plasma wake. Subsequently, in the second stage, the drive pulse enters a lower-density plasma region so that the wake has a larger plasma cavity in which longer-wavelength infrared pulses can be produced. Numerical simulations show that the resulting near-single-cycle pulses cover a broad spectral range of 10–40 µm with a conversion efficiency of ∼2.1% (∼34 mJ pulse energy). This enables the investigation of nonlinear infrared optics in the relativistic regime and offers new possibilities for the investigation of ultrafast phenomena and physics in strong fields.

Void nucleation and growth under dynamic loading are essential for damage initiation and evolution in ductile metals. In the past few decades, the development of experimental techniques and simulation methods has helped to reveal a wealth of information about the nucleation and growth process from its microscopic aspects to macroscopic ones. Powerful and effective theoretical approaches have been developed based on this information and have helped in the analysis of the damage states of structures, thereby making an important contribution to the design of damage-resistant materials. This Review presents a brief overview of theoretical models related to the mechanisms of void nucleation and growth under dynamic loading. Classical work and recent research progress are summarized, together with discussion of some aspects deserving further study.

A novel bidirectional remotely controlled device for static and dynamic compression/decompression using diamond anvil cells (DACs) has been developed that can control pressure in an accurate and consistent manner. Electromechanical piezoelectric actuators are applied to a conventional DAC, allowing applications under a variety of pressure conditions. Using this static and dynamic DAC (s-dDAC), it is possible to addresses the poorly studied experimental regime lying between purely static and purely dynamic studies. The s-dDAC, driven by three piezoelectric actuators, can be combined with a time-resolved spectral measurement system and high-speed imaging device to study the structural changes, chemical reactions, and properties of materials under extreme conditions. The maximum compression/decompression rate or pressure range highly depends on the culet size of the anvil, and a higher compression rate and wider pressure range can be realized in a DAC with smaller anvil culet. With our s-dDAC, we have been able to achieve the highest compression rate to date with a 300 μm culet anvil: 48 TPa/s. An overview of a variety of experimental measurements possible with our device is presented.

We present a Stark–Zeeman spectral line-shape model and the associated numerical code, PPPB, designed to provide fast and accurate line shapes for arbitrary atomic systems for a large range of plasma conditions. PPPB is based on the coupling of the PPP code—a Stark-broadened spectral line-shape code developed for multi-electron ion spectroscopy in hot dense plasmas—and the MASCB code developed recently to generate B-field-dependent atomic physics. The latter provides energy levels, statistical weights, and reduced matrix elements of multi-electron radiators by diagonalizing the atomic Hamiltonian that includes the well know B-dependent term. These are then used as inputs to PPP working in the standard line-broadening approach, i.e., using the quasi-static ion and impact electron approximations. The effects of ion dynamics are introduced by means of the frequency fluctuation model, and the physical model of electron broadening is based on the semi-classical impact approximation including the effects of a strong collision term, interference, and cyclotron motion. Finally, to account for polarization effects, the output profiles are calculated for a given angle of observation with respect to the direction of the magnetic field. The potential of this model is presented through Stark–Zeeman spectral line-shape calculations performed for various experimental conditions.

A simultaneous high-resolution x-ray backlighting and self-emission imaging method for laser-produced plasma diagnostics is developed in which two Kirkpatrick–Baez imaging channels for high-energy and low-energy diagnostics are constructed using a combination of multilayer mirrors in near-coaxial form. By using a streak or framing camera placed on the image plane, both backlit and self-emission images of a laser-produced plasma with high spatial and temporal resolution can be obtained simultaneously in a single shot. This paper describes the details of the method with regard to its optical and multilayer design, assembly, and alignment method. In addition, x-ray imaging results with a spatial resolution better than 5 µm in the laboratory and experimental results with imploding capsules in the SG-III prototype laser facility are presented.

We describe the design and x-ray emission properties (temporal, spatial, and spectral) of Dry Pinch I, a portable X-pinch driver developed at Imperial College London. Dry Pinch I is a direct capacitor discharge device, 300 × 300 × 700 mm3 in size and ∼50 kg in mass, that can be used as an external driver for x-ray diagnostics in high-energy-density physics experiments. Among key findings, the device is shown to reliably produce 1.1 ± 0.3 ns long x-ray bursts that couple ∼50 mJ of energy into photon energies from 1 to 10 keV. The average shot-to-shot jitter of these bursts is found to be 10 ± 4.6 ns using a combination of x-ray and current diagnostics. The spatial extent of the x-ray hot spot from which the radiation emanates agrees with previously published results for X-pinches—suggesting a spot size of 10 ± 6 µm in the soft energy region (1–10 keV) and 190 ± 100 µm in the hard energy region (>10 keV). These characteristics mean that Dry Pinch I is ideally suited for use as a probe in experiments driven in the laboratory or at external facilities when more conventional sources of probing radiation are not available. At the same time, this is also the first detailed investigation of an X-pinch operating reliably at current rise rates of less than 1 kA/ns.