V. L. Paperny

Micropinches in laser induced moderate power vacuum discharge

Studies of x-ray emission from a laser induced vacuum discharge of moderate storage energy (<20 J) are examined. It is found that micropinches in the initial stage of the cathode jet expansion into the interelectrode gap are formed. Hot plasma of the micropinches emits a soft x-ray radiation and beams of accelerated electrons moving toward the anode. It is found that these phenomena occur just when both amplitude of the discharge current and energy of the initiating laser pulse lie in the specified ranges of values. The position of the micropinch within the interelectrode gap and also the intensity of the x-ray radiation and beams of the accelerated electrons emitted from the micropinch are variable over a wide range of values through changes in energy of the laser pulse and/or amplitude of the discharge current. The experimental results are compared with the data of the particle-in-cell simulations and a fair agreement is found between them.

Metal plasma jet passage through plasma-optical transport system

The passage of a plasma jet of steady-state vacuum arc discharge through a plasma-optical transport (POT) system based on a curvilinear magnetic field has been studied. Special features of the system are the absence of a metallic duct and the misfit of axes of the guiding magnetic field and the plasma jet. It is demonstrated that the position and shape of the plasma jet at the POT system output can be varied within broad limits by changing the currents in solenoids and the positive bias on a control electrode introduced into the plasma jet. For fixed parameters of the POT system, the jet position depends on the mass to charge ratio of plasma ions.

Charge separation of plasma flow in curvilinear magnetic field

The energy spectra of ions occurring in various charged states in a flow of titanium plasma in a steady-state vacuum arc discharge have been studied. It is established that, during the motion of this flow through a plasma transport system based on a curvilinear magnetic field, ions with different charges are spatially separated. As a result, at the system output, ions with greater charges are concentrated in the inner part of the plasma flow, so that the average charge of ions in this region is higher than that in the outer part of the flow.

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.

Energy spectrum of a multicomponent flux of accelerated ions

We have experimentally studied the energy spectrum of an accelerated ion beam moving in a drift gap upon separation by a grid electrode system from a metal plasma jet of a pulsed high-current vacuum arc. It is established that the average energy per unit ion charge in the beam is below the value corresponding to the accelerating voltage. The width of the energy spectrum of accelerated ions is close to their average energy and significantly exceeds the width of the energy spectrum of the initial beam. The results of model calculations show that the observed phenomena can be explained by the action of a nonstationary electric field of the space charge of the ion beam transported via the drift gap.

Vacuum discharge as an effective source of multiply charged ions

The time-of-flight (TOF) spectra measured under high vacuum conditions revealed ion beams of a cathode material (Cun+) with a maximum charge of up to +19 generated in the initial stage of a spark discharge development at a storage voltage of up to U0=2.5 kV. As the U0 value increases, the range of the multiply charged states of ions detected by the TOF technique increases, the average ion charge reaching +9.

Expansion of a multicomponent current-carrying plasma jet into vacuum

An expression for the ion−ion coupling in a multicomponent plasma jet is derived for an arbitrary ratio between the thermal and relative velocities of the components. The obtained expression is used to solve the problem on the expansion of a current-carrying plasma microjet emitted from the cathode surface into vacuum. Two types of plasmas with two ion components are analyzed: (i) plasma in which the ion components of equal masses are in the charge states Z1= +1 and Z2= +2 and (ii) plasma with ions in equal charge states but with the mass ratio m1/m2 = 2. It is shown that, for such plasmas, the difference between the velocities of the plasma components remains substantial (about 10% of the average jet velocity in case (i) and 15% in case (ii)) at distances of several centimeters from the emission center, where it can be measured experimentally, provided that its initial value at the emitting cathode surface exceeds a certain threshold. This effect is investigated as a function of the mass ratio and charge states of the ion components.

Effect of space charge on the energy spectrum of a multispecies ion beam

AbstractThe parameters of a multispecies metal ion beam extracted with the help of a set of grids from a plasma jet of a pulsed vacuum arc are studied experimentally. It is shown that the beam contains ions with energies that are both significantly lower and higher than the expected energy EZ =

Characteristics of plasma flow from a pulse vacuum arc

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