Yu. V. Korobkin

Influence of laser pulse parameters on characteristics of a source of multicharged metal ions based on laser-induced medium-power spark discharge

The dynamics of laser-induced vacuum spark discharge with storage energy not exceeding 25 J has been studied in a broad range of laser pulse energies and power densities. It is shown that, using discharge-initiating laser pulse of nanosecond duration, it is possible to obtain stable single pinching of cathode jet plasma at a storage voltage above 10 kV. Plasma pinching is accompanied by the generation of a beam of multicharged ions of the cathode material (aluminum) up to Al8+. The maximum energies of ions obey the scaling relation Emax = 5ZeU0 that has been obtained previously for a low-voltage discharge. An increase in the laser pulse energy leads to growth of the average beam charge and a sharp decrease in the ion energy.

Ion acceleration in a high-current cathode plasma jet expanding in vacuum

Ion acceleration in a high-current cathode plasma jet of a low-voltage vacuum spark discharge has been studied. It is established that an increase in the discharge current amplitude leads to a growth in both the density and velocity of the ion flux emitted from the discharge gap. The dependence of the ion velocity on the discharge current amplitude in the range below 10 kA is well described by a simple hydrodynamic model of the current-carrying jet with allowance for plasma compression by the intrinsic magnetic field of the discharge current. For discharge current amplitudes exceeding 10 kA, the ion velocity ceases to grow and exhibits a considerable scatter of values measured in different shots.

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.

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.

Active media for lasers based on colored epoxy and triazine-containing polymers

The problems of the synthesis of active media for lasers based on colored thermoreactive polymers are examined, and the lasing characteristics of the active media are investigated.

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.

Formation of a cathode plasma jet in a laser-induced vacuum discharge

The process of formation of micropinch structures in the plasma of a vacuum discharge initiated by a laser pulse on the cathode is studied. It is demonstrated that the micropinch formation takes place mainly in the substance evaporated by the laser pulse upon the discharge initiation. The size of the hot region of the plasma jet and the distance from the cathode to the micropinch increase with increasing laser pulse energy.

Second-harmonic conversion of partially coherent radiation of neodymium glass laser

The experimental results on the conversion of multimode radiation of a neodymium glass laser with controlled spatial and temporal coherence to the second optical harmonic in nonlinear KDP crystal during the oee interaction implementation are presented. The dependence of the efficiency of the conversion to the second harmonic on the fundamental radiation power density on the crystal in the range I = 0.2 − 5 GW/cm2 is studied at the number of transverse modes in the cavity N = 1000; the radiation divergence φ = 3.5, 4.7, and 5 mrad; the emission spectral width δλ = 5and 42 Å; and the pulse duration of 2.5 ns. The breakdown power density of the KDP crystal is determined, the interference properties of the converted radiation of the second harmonic are studied.

Pulsed operation of low-power plasma thruster

Integral and local characteristics of the laboratory model of a low-power plasma thruster operating in a pulsed regime have been experimentally studied. Rectangular pulses of discharge current with the leading and trailing fronts not exceeding 1 ms have been obtained. At an average supplied electric power of ∼150 W, the propulsion efficiency amounted to 35%. The plasma concentration, electron temperature, and potential distributions in the output plasma jet have been measured using an electric probe. These measurements showed that a well formed plasma jet with a small divergence angle exists behind the thruster edge.

On one possibility of studying dynamics of ferroelectric repolarization

It was shown that the time dependence of the current appeared during ferroelectric repolarization is controlled by nonstationary dynamics of spontaneous polarization caused by external influences. Furthermore, even a flowing charge yields information on domain structure transformation. The paper conclusions are illustrated by experimental data on ferroelectric repolarization under electric fields and laser pulses.