V. I. Krasov

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.

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 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.

Spatial structure, dynamics and electron heating of cathode jet of a pulse vacuum discharge

Results of experimental studies of energy and charge state distributions of ions in a cathode plasma jet of a high-current vacuum discharge are presented. Measurements have been carried out by a time-of flight method with an electrostatic energy analyzer. Ions of cathode material with the charge states up to Z=+11 have been observed. Significant increase of the mean ion charge and the ion energy in compare both with the low-current discharges and with the steady-state arcs has been obtained. With the peak discharge current about 2.5 kA and the rate of current rise I/spl dot/=3/spl middot/10/sup 9/ A/s the mean ion charge state equals Z=6.4 and the mean ion energy for different ion species was within range 1.3-1.8 keV. These results are explained by pinching of the cathode jet by magnetic field of its current which occur at high values of I and the region of ions generation is rather less than the size of cathode jet.

Influence of centrifugal drift on mass-separation of ions of plasma flow in a curved magnetic field

Traveling of plasma flow produced with a DC arc through a transport system based on a curved magnetic field was studied. For arc with a composite cathode, principally, consisted of Cr-Fe-Ni, the profile of atoms of these elements at exit of the transport system was measured by the X-ray fluorescence spectrometry. It was found that with parameters of the transport system held constant, the plasma ions with lower m/Z were deflected more, namely Cr ions were deflected more that Fe and Ni ions. It was found as well that ions with different m/Z are shifted along binormal to the magnetic field lines in different ways that, supposedly, is due to the centrifugal drift. This effect results in the additional separation of ions of different masses in this direction.

Transport of plasma fluxes with distinct ion masses through a curved magnetic field

Traveling of cathode plasma flow of a steady state arc through a transport system based on a curved magnetic field and supplied with an additional governing electrode is studied. Characteristic of the system is that the metallic guiding duct is absent as well as that the magnetic field is produced by the coils located beyond the plasma flow trajectory. It is shown that position of cathode plasma flow at exit of the transport system is governed by currents of the magnetic coils. If the coil currents hold constant, biasing of the electrode governs both shape of the plasma flow and position of its maximum. It is found that these positions when both the magnetic field and bias hold constant are distinct for different cathode materials, so that the system, in principle, can be used for spatial separation of a multi-component (by mass) plasma flow.

Ion Erosion Rate in a High Current Vacuum Spark

Measurements of the ion erosion rate for copper cathode in the low-inductance vacuum spark are presented. The spark peak current was varied from 3 kA up to 13 kA therewith the current rise rate increases from 4middot109 up to 1.5middot1010 A/s. The mean velocity of the cathode plasma flame was obtained by means of the passive collector time-of-flight measurements. It was shown that the velocity increases from 2middot104 m/s up to 8middot10 4 m/s with the discharge enhancement. Mechanical momentum of the plasma flame was measured with a ballistic pendulum, located beyond annual anode in the immediate vicinity. From these data the ion erosion rate was derived at range of peaks of the discharge current mentioned above. This parameter holds to within the accuracy of measurements throughout the range of the current variations. Its value is of 7middot10-5 g/Q and is close to the well-known one that has been obtained earlier in low-current vacuum arcs

Charge and mass transfer in the cathode plasma jet of a low-inductance vacuum spark

The contributions of fast and slow ion components to the average mass transfer rate in the cathode plasma jet of a low-inductance vacuum spark have been determined using time-of-flight measurements. The total mechanical momentum of the cathode plasma jet has been found using the ballistic pendulum technique. The coefficient γ of ion erosion of a cathode material was evaluated in the range of discharge current amplitudes 3–13 kA and the discharge current buildup rates 4 × 109 − 1.5 × 1010 A/s. The γ value exhibits small variations in the indicated range of discharge parameters and is close to the values known for vacuum arcs.

Extended region of ''anomalous'' acceleration in the cathode jet of a vacuum discharge

AbstractIt is observed that “anomalous” acceleration of ions in a pulsed vacuum discharge is initiated at a certain distance from the surface of the cathode and takes place in the bulk of the cathode jet. It is established that the average ion energy