X-ray emission from stainless steel foils irradiated by femtosecond petawatt laser pulses

We report about nonlinear growth of x-ray emission intensity emitted from plasma generated by femtosecond petawatt laser pulses irradiating stainless steel foils. X-ray emission intensity increases as ∼ I 4.5 with laser intensity I on a target. High spectrally resolved x-ray emission from front and rear surfaces of 5 μm thickness stainless steel targets were obtained at the wavelength range 1.7-2.1 Å, for the first time in experiments at femtosecond petawatt laser facility J-KAREN-P. Total intensity of front x-ray spectra three times dominates to rear side spectra for maximum laser intensity I ≈ 3.21021 W/cm2. Growth of x-ray emission is mostly determined by contribution of bremsstrahlung radiation that allowed estimating bulk electron plasma temperature for various magnitude of laser intensity on target

Asymptotics of eigenfunctions and eigenvalues of a singularly perturbed relativistic analogue of the Schrödinger equation with an arbitrary potential

The paper is devoted to the study of finite truncations of the radial part of the relativistic analog of the Schrödinger equation (quasipotential equation) which are obtained by means of truncating the operator coshleft( frac {ihslash}{mc}frac d{dr}right) to a finite part of its Taylor series. The constant c is assumed to be large, so that the truncated equation is a singular perturbation of boundary layer type of the limit standard radial Schrödinger equation. The asymptotics of the eigenvalues are constructed by means of a standard technique in terms of the solutions of the unperturbed equation and boundary layer functions; the eigenvalues have regular perturbation series. The paper contains some rather surprising assertions (for example, domains of differential operators are segments of the real line, differential operators in L_2 are continuous, etc.), so that the results of Section 4 on the behavior of eigenvalues as mtoinfty (where m is the order of truncation) are suspect, but formal asymptotic series for a finite truncation are apparently correct

Detailed analysis of hollow ions spectra from dense matter pumped by X-ray emission of relativistic laser plasma

X-ray emission from hollow ions offers new diagnostic opportunities for dense, strongly coupled plasma. We present extended modeling of the x-ray emission spectrum reported by Colgan et al. [Phys. Rev. Lett. 110, 125001 (2013)] based on two collisional-radiative codes: the hybrid-structure Spectroscopic Collisional-Radiative Atomic Model (SCRAM) and the mixed-unresolved transition arrays (MUTA) ATOMIC model. We show that both accuracy and completeness in the modeled energy level structure are critical for reliable diagnostics, investigate how emission changes with different treatments of ionization potential depression, and discuss two approaches to handling the extensive structure required for hollow-ion models with many multiply excited configurations

Ultra-bright keV X-ray source generated by relativistic femtosecond laser pulse interaction with thin foils and its possible application for HEDS investigations

It was shown (Faenov et al ., 2015 b ) that the energy of femtosecond laser pulses with relativistic intensity approaching to ~10 21 W/cm 2 is efficiently converted to X-ray radiation and produces exotic states in solid density plasma periphery. We propose and show by one-dimensional two-temperature hydrodynamic modeling, that applying two such unique ultra-bright X-ray sources with intensities above 10 17 W/cm 2 – allow to generate shock waves with strength of up to some hundreds Mbar, which could give new opportunities for studies of matter in extreme conditions

Measurements of X-ray spectral opacity of dense plasma at ISKRA-5 laser facility

Powerful iodine ISKRA-5 laser facility was upgraded and now operates on the second harmonic. Experiments were performed to measure the x-ray spectral opacity of dense plasma of different materials. Sample of material under study was fabricated as a thin plate with the 0.1-0.15 $\mu$m thickness and was heated by the soft x-rays generated by irradiation of a thin film gold converter by one beam of the ISKRA-5 laser facility. Typical laser intensity on the converter was (1-5)$\cdot$10$^{13}$ W/cm$^{2}$ and laser pulse duration was 0.5-0.6 ns. The effective temperature of sample under experimental conditions didn't exceed 30-40 eV. The sample was tampered by $\sim$ 1 $\mu$m plastic layers on both sides to avoid its rarefaction during heating and to obtain a quasistationary layer of a dense plasma prepared to be probed by a backlighter. The backlighter was aluminum or dysprosium film irradiated by another beam of the ISKRA-5 laser facility with an intensity of 10$^{14}$-10$^{15}$ W/cm$^{2}$. Probe x-rays were registered by a Bragg spectrometer with spatial resolution. Comparison between experimental data and simulations is discussed