Analysis of characteristic X-ray generation induced by laser plasma electrons accelerated by an electric field

The results of experiments devoted to the study of spectral, spatial, and time characteristics of a spectrally bright point x-ray source based on a vacuum diode with a laser-plasma cathode and a titanium needle anode with a photon energy approximately equal to 4.5 keV are presented. The experimental results revealed a considerable difference between the electron emission from laser plasma in a strong electric field and the explosive electron emission and demonstrated the effectiveness of laser plasma as an electron source. The optimization of the laser radiation power density, the accelerating voltage, and the interelectrode spacing made it possible to create a point x-ray source whose spectral brightness exceeds available sources in the class of small-size pulse x-ray instruments (tubes with explosive cathodes). It has been proved experimentally that the maximum contrast of the characteristic lines of the anode material is attained in the case of an optimal choice of accelerating voltage. The x-ray source has the following parameters: (1) spectral brightness of the K-lines of titanium of the order of 10²¹ photons/cm² s sr keV; (2) emitting region size of 250 mm; and (3) laser pulse duration less than 20 ns.     

Physical characteristics of a heavy hydrogen ion source based on a coaxial discharge system with central filament anode

Results are presented from a study of physical characteristics of a heavy hydrogen isotope ion source using a gas filled accelerator tube for neutron generation based on a coaxial system with central filament anode. High and low current operating modes of such a source are considered, together with factors affecting its operation. Mass-spectrometer and current-voltage characteristics of orbitron ion sources are considered. The advantages and shortcomings of such sources compared to Penning sources are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 13–17, September, 1990.     

Vacuum discharge instability at laser initiation of a cathode spot

The dynamics of fast (a current rise time of ≤10¹¹ A/s) laser-induced vacuum discharges with moderate amplitudes of the current (≤10 kA) and voltage (≤20 kV), as well as medium storage energy (20 J), is studied. It is shown experimentally that the initial conditions specified by the energy and duration of laser radiation are a decisive factor governing the discharge dynamics. Two types of beam-plasma instabilities separated in space and time are discovered, and their occurrence conditions are analyzed. The first type of instability, observed early in the discharge, is associated with pinch structures at the front of the cathode jet expanding into a vacuum. The second type arises either at the peak or at the trailing edge of the current pulse and is accompanied by generation of hard (with an energy of ≥100 keV) bremsstrahlung from the anode region. The increase of the hard component energy over the current source potential is attributed to breaking due to plasma erosion.     

Monochromatic X-Ray Sources Based on Emitters Controlled by Laser Radiation

The results of study of frequency-tuned monochromatic x-ray source are reported. The source was developed on the basis of a vacuum diode with a laser-plasma cathode. The source proposed is particularly promising, if the range of x-ray energy higher than 5 keV is of interest. The source features a spectral brightness higher than 10¹⁹ photons/(cm²·s·sr·keV) and an x-ray pulse duration no larger than 10^?8 s. An electromagnetic model of such a cathode is proposed and evaluated in order to assess the feasibility of an x-ray source with a laser-plasma cathode of higher performance. The possibility of using a ferroelectric electron emitter is discussed.     

Diagnostics of the temperature of a plasma created by a CO2 laser,from the UV radiation spectrum

Delivered at the Fifth All-Union Conference on Diagnostics of a High-Temperature Plasma (18–22 June, 1990, Minsk).     

Effect of non-linear thermal conductivity in a shock wave front at a velocity of 107–108 cm/s

The structure of a shock wave front at a velocity of 10⁷–10⁸ cm/s has been studied experimentally. The formation of a pre-heated layer caused by the thermal conductivity of the electrons before the shock wave has been observed for the first time.     

Dynamics of plasma corona of laser-irradiated spherical targets

The paper is devoted to an investigation of the formation and spreading of an inhomogeneous dense plasma heated by high-power laser radiation. The present status of the experimental and theoretical research in this field is analyzed. The “Kal'-mar” facility is used to study the dynamics of the plasma corona (electron density n_e ~ 10¹⁸–10²⁰ cm^-3), the law of motion of the critical (n_e ~ 10²¹ cm^-3) region of the plasma is established, and the dependence of the rate of compression of the shell targets on the initial parameters is determined. The electron temperature of the corona is measured with high temporal resolution in the course of the compression. A jetlike expansion of the “fast” ions is observed and investigated.     

Formation of Ion Fluxes of Laser Plasma by Azimuthally Symmetric Magnetic Fields

Physics of Atomic Nuclei - The formation of ion fluxes of the laser plasma by axially symmetric magnetic fields is studied. An algorithm for forming ion fluxes is developed and a computer...     

Model of forming deuteron fluxes and neutron generation in an axial plasma diode with inertial ion confinement

A model of forming deuteron fluxes and neutron generation in an axial plasma diode with two external anodes and a transparent internal hollow cathode is suggested. Such configuration provides longitudinal deuteron oscillations (inertial confinement) and required frequency of collisions with slow deuterons in the cathode plasma. On the basis of the suggested model of neutron generation, the neutron flux generated in the course of D(d, n)³ He nuclear reactions is approximately calculated. The examined diode system seems to be promising for the development of compact controllable neutron sources with increased operation lifetime and transverse size no more than 5 cm.