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Sub-picosecond optical laser processing of metals is actively utilized for modification of a heated surface layer. But for deeper modification of different materials a laser in the hard x-ray range is required. Here, we demonstrate that a single 9-keV x-ray pulse from a free-electron laser can form a um-diameter cylindrical cavity with length of ~1 mm in LiF surrounded by shock-transformed material. The plasma-generated shock wave with TPa-level pressure results in damage, melting and polymorphic transformations of any material, including transparent and non-transparent to conventional optical lasers. Moreover, cylindrical shocks can be utilized to obtain a considerable amount of exotic high-pressure polymorphs. Pressure wave propagation in LiF, radial material flow, formation of cracks and voids are analyzed via continuum and atomistic simulations revealing a sequence of processes leading to the final structure with the long cavity. Similar results can be produced with semiconductors and ceramics, which opens a new pathway for development of laser material processing with hard x-ray pulses.

Materials exposed to ultrashort intense x-ray irradiation may experience various damaging conditions depending on the in-situ temperature. A pre-heated target exposed to intense x-rays plays a crucial role in numerous systems of physical-technical importance, ranging from the heavily-, and repeatedly radiation-loaded optics at x-ray free-electron laser facilities, to the first wall of prospective inertial fusion reactors. We study theoretically the damage threshold dependence on the temperature in different classes of materials: an insulator (diamond), a semiconductor (silicon), a metal (tungsten), and an organic polymer (PMMA). The numerical techniques used here enable us to trace the evolution of both, an electronic state and atomic dynamics of the materials. It includes damage mechanisms such as thermal damage (induced by an increase of the atomic temperature due to energy transfer from x-ray-excited electrons) and nonthermal phase transitions (induced by changes in the interatomic potential due to excitation of electrons). We demonstrate that in the pre-heated materials, typically, the thermal damage threshold stays the same or lowers with the increase of the in-situ temperature, whereas nonthermal damage thresholds may be lowered or raised, depending on the particular material and specifics of the damage kinetics.

According to a prevailing opinion, the electron g-factor ge = 2 is exclusively a quantum feature. Here we demonstrate it could be explained classically only in relativistic terms. The electron is treated as an extended, continuous, but rigid Gaussian body (RGB) spinning at finite angular frequency. In contrast to expectations, the mechanical energy and spin angular momentum of the particle are not diverging but standard values are reproduced. The g-factor value ge = 2 immediately follows from the ratio of non-relativistic and relativistic angular momenta which can be both attributed to a spinning electron of known rest mass. A detailed analysis of the inertia tensor and limit, torque-free precession reveals a multiplication factor of -2 between the external and internal precession angular frequency which might resemble the spin-1/2 appearance of the particle. Furthermore, the theory of Li\'enard and Wiechert is used to derive a static electromagnetic field. A continuous form of Gaussian charge density ensures an absence of infinities in electromagnetic energy and angular momentum. Introducing the associated electromagnetic angular momentum as a small correction to the mechanical spin angular momentum, we obtain a modified g-factor ge* = 2.0021 which is close to the measured value ge = 2.0023., Comment: 17 pages, 5 figures