Effect of the parametric beam instability (PBI) of the relativistic electron beam in a crystal was analyzed theoretically in1 (see also2). This effect is analogous to self-amplification of spontaneous emission (SASE) mechanism for X-ray Free Electron Laser (XFEL) with an undulator. However, in the case of PBI the transversal modulation of the beam is defined by channeling of the electron in a crystal and the longitudinal modulation arises because of the parametric X-ray radiation mechanism. It is shown in the present paper that the current density J in the electron bunch typical for FEL facility is enough for the beam self-modulation within the X-ray range if the crystal thickness is larger than the crystal absorption length L ≥ Labs. This process could be used for generation of the coherent X-ray pulses if the time τd of the crystal destruction affected by the electron bunch is less than its passing time τd< L=c. The value τd(J) is estimated for the case of the FLASH electron bunch propagating through a Si crystal.
Interaction of the X-ray Free Electron Laser (XFEL) femtosecond pulses with a crystal is investigated beyond the means of the conventional linear response theory. In order to analyze the time dependence of the X-ray scattering properties of a crystal we analyze the electron density evolution on the basis of rate equations.1 In order to take into account the influence of the electron plasma that appears due to the ionization of the atoms of a crystal we couple the system of rate equations to the Boltzmann kinetic equation. As a result, the system of master equations involves such evolution channels as: photoionization, Auger recombination, electron impact ionization, electron-electron scattering and three body recombination. In order to consider these channels effectively expressions for the cross sections of these processes are calculated within the framework of the effective charge approximation.2 The numerical algorithm and software are developed for calculation of the intensity of the diffraction reflection of the XFEL pulse taking into account the specific characteristics of the kinetic processes in a crystal. Numerical results are analyzed on the example of the Si crystal in the wide range of the pulse parameters variation.
There is a problem of creation of the system of the halftone and colored laser-beam recording of high resolution. Obstacles have influence on them more than on binary systems of laser- beam recording. Periodical fluctuations of speed of scanning are particularly dangerous. These fluctuations are connected with the vibration of the mechanism of movement of the light sensitivity material. They create a parasitic effect on the recorded image. The cardinal way of disposing of the problem is recording on an immovable material. These records can be made by the system of the two-coordinate angular scanning of the laser-beam. This system has geometrical distortions. Questions of correction of geometrical distortions are considered in this article. An objective with negative distortions is proposed by us for correction of geometrical distortions of one coordinate. We propose to make a correction of the geometrical distortions for a bi-coordinate scanning system by an electronic method. The essence of the electronic method is a modulation of the timing frequency of recording by a function of the correction of distortions. A module of the two-coordinate scanning was elaborated and investigated. The module contains two deflectors, an interferometric system, a block of the control and a three-lens objective with negative distortions. Resolution of scanning of the module is 10,000 X 10,000. Area of recording is 300 X 300 mm. Horizontal sweep frequency is 150 Hz. Error of the position of a beam is +/- 0.002 mm.
In the article there is an estimation of the maximum speed of electromagnetic and piezoceramic deflectors. The estimation takes into consideration properties of used materials and working conditions. Analytical dependences are received. They connect the maximum speed, an angle of deflection, and an aperture of light beam. It's found out that the maximum speed of electromagnetic deflectors is 5 - 10 MHz and the maximum speed of piezoceramic deflectors is 1 - 3 MHz. A mathematical model of the electromechanical deflector is elaborated. Mathematical simulation of transitional processes is conducted. Influence on the transitional process of the first and the second mechanical resonance was investigated. An experimental research of deflectors with the maximum parameters was made.
The interferometric scanning laser beam position control system based on Ronchi interferometer is investigated. The new technical decision, increasing the accuracy and ranges of measurements are considered. The basic ratios and the results of experimental research are adduced.
This paper presents an analysis of laser beam image recording on a metal-polymer film and an estimation of technical parameters of devices for the recording realization.
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