Radiophysics and Quantum Electronics最新文献

The paper considers a laser discharge supported by an infrared laser in a jet of a heavy gas as a source of extreme ultraviolet (EUV) radiation for lithography. It is shown theoretically and demonstrated in the experiment that the region occupied by the plasma emitting in the EUV wavelength range is much larger than the laser focal spot. Expansion of the emitting plasma beyond the laser focus is explained by the photoionization of the surrounding gas and subsequent heating of electrons by the heat flux from the energy deposition region due to thermal conductivity. The possibilities of optimizing the EUV radiation source based on the discharge under consideration are studied. Limiting parameters of the xenon plasma-based EUV radiation source intended for use in the Alpha Machine project are discussed. It is planned to create a demonstration EUV lithograph within the framework of the project. It is shown that the use of a xenon jet can provide efficiency at the level of the existing commercial sources.

The advance in developing methods for generating super-strong magnetic fields (from several teslas to several and even tens of kiloteslas) opens up new possibilities for using them to control beams of charged particles. In this paper, we present a theoretical analysis and calculation of the influence of a super-intense external magnetic field (up to 100 kT) on the process of generating and collimating a laser plasma flow and fast electrons with energies exceeding 1 MeV, which are obtained due to the interaction of a laser pulse having the relativistic intensity and a femtosecond duration with a thin aluminum foil. The obtained analytical estimates of the electron beam collimation agree well with the results of computer calculations. Time evolution of the electron beam is also considered, and estimates of the electron charge loss over time as a function of the external magnetic field are presented.

We study the possibilities of developing electrodeless plasma jet engines on the basis of an electron cyclotron resonance (ECR) discharge. The efficiency of using the working substance in the engine is achieved by increasing the speed of its outflow, which is determined by the maximum electron energy achievable in the ECR discharge. The work involved the measurement of the energy distribution function of the electrons emitted from a discharge maintained in a simple magnetic trap by high-power microwave radiation in the continuous-wave regime. A discharge combustion mode is discovered, which realizes a nonequilibrium electron energy distribution function characterized by the presence of a clearly expressed hot fraction with a characteristic energy of more than 100 keV.

Using the method of microwave reactive sintering, we obtained Ce:YAG–Al₂O₃ ceramic composite samples with a density of about 95% of the theoretical value and exhibiting luminescent properties. It was established that during the microwave heating, the temperatures of phase transformations in both the Y–Al–O system and aluminum oxide decrease by 250–400°C (depending on the intensity of the microwave electromagnetic field in the sample) compared to conventional furnace heating. This indicates a significant effect of the microwave electromagnetic field on diffusion transport and nucleation processes in the solid-state chemical reactions leading to the formation of yttrium–aluminum garnet.

We present the results of the initial stage of studying the gyrotron-type devices with a novel electrodynamic system in the form of a zigzag quasioptical transmission line. The basic concept of the considered modification was proposed for the first time in 2018, particular versions of such devices with calculation results were described in a publication of 2021, and the first successful experiments were carried out and reported in early 2024. The electrodynamic system under discussion consists of mirrors that direct a quasioptical Gaussian beam along a zigzag trajectory in such a way that it periodically intersects the electron beam at the right angle. At the points of these intersections, electron-wave interaction occurs at a frequency close to the cyclotron frequency of electrons having initial transverse velocities. The work treats the features of such devices and the results of their theoretical analysis in detail and presents the results of the first experiments.

We present the results of an experimental study of instability developing in high-speed (speed v ∼ 500 km/s) plasma flows propagating in an external magnetic field with induction about 14 T. High-speed plasma flows were created as a result of irradiation of the Teflon target by nanosecond pumping laser pulses of the PEARL laser facility. It has been demonstrated that at the stage of plasma confinement by a magnetic field, a Rayleigh–Taylor instability develops in the form of flutes on the surface of the plasma cavity. Instability is observed when the plasma spreads both along and across an external uniform magnetic field and rapidly passes into the nonlinear phase, which allows the plasma to penetrate into the magnetic field region.

We propose a convolutional neural network–based algorithm for retrieving the wavefront shape of a beam using in-focus and out-of-focus intensity distributions. The neural network is trained on numerically generated data. In numerical experiments, the trained model enabled wavefront shape reconstruction with a relative error below 20% for root-mean-square (rms) wavefront distortion in the range of (0.05–0.25)λ, where λ is the radiation wavelength. In a physical experiment conducted on the PEARL laser facility, for a beam with an 18 cm aperture, equal to one-quarter of the focal length, the relative error was approximately 40% for rms wavefront distortion of 0.4λ.

The problem of generating single-mode terahertz pulsed radiation via optical rectification of a femtosecond laser pulse (Ti:Sapphire) in a nonlinear crystal partially filling a parallel-plate waveguide is addressed. A numerical analysis of the mode composition and terahertz pulse transmission in this structure is performed. It is demonstrated that single-mode coupling between the linearly polarized optical excitation pulse focused on the LiNbO₃ crystal and the terahertz pulse can be achieved in a broad spectral range of 0.1–2.5 THz. The study shows that efficient generation and single-mode transmission of the terahertz pulse with minimum attenuation can be achieved by optimally selecting the sizes and permittivity of the nonlinear crystal, along with the waveguide sizes. The results are compared with both experimental and numerical data for a rectangular metal waveguide partially filled with an optically nonlinear crystal.

We propose to use a combined two-mirror resonator based on the three-dimensional (3D) and onedimensional (1D) Bragg reflectors in order to achieve a multi-gigawatt level of microwave power in free-electron masers (FEMs) having the planar geometry. The possibility of creating a FEM of this type in the W band on the basis of the U-2 accelerator, which forms a sheet electron beam with a cross section of 1×140 cm, is studied within the framework of the quasioptical model. It is shown that in the proposed scheme, the input Bragg 3D reflector implementing the mechanism of the three-dimensional distributed feedback allows one to ensure the synchronization of radiation along both transverse coordinates at the cross-sectional sizes of the system from tens to hundreds of wavelengths, while a small reflection from the output conventional 1D Bragg reflector is sufficient to complete the feedback loop and provide the single-mode generation regime with a high efficiency and a low ohmic-loss level. At the optimal parameters, the possibility is demonstrated of obtaining a stable narrow-band generation regime in the developed FEM with an electron efficiency of about 18–20% and a record-breaking output radiation power of up to 20 GW.

The structure of a laser pulse may significantly affect the dynamics of particles interacting with it. In the case of a rarefied plasma, single-particle approach to the problem is a good approximation. This paper considers the problem of absorption of the orbital angular momentum by a single particle in a focused structured pulse. Within the framework of the developed theoretical model, which includes the solution of the Maxwell equations with required accuracy and a high-order perturbation theory, the motion of electrons is considered in a number of important cases. Analytical results are compared with the data of numerical simulation. It is demonstrated that the angular dependence in the structure of the laser pulse plays a fundamental role in the absorption of the orbital angular momentum of a wave by an ensemble of charged particles.