K. Chirko

Spectroscopy of a ferroelectric plasma cathode

Results of spectroscopic investigations of the plasma formed on the surface of a ferroelectric cathode upon the application of a driving pulse are presented. The ferroelectric plasma cathode was made of a solid solution of Sr, Ba, Ti, Nb, Pb, and O. Its front side was covered by Cu grounded strip electrodes. A driving pulse with an amplitude ≲18 kV and pulse duration of ∼400 ns was applied to the rear Cu disk electrode. A Jobin-Yvon 750M spectrometer was used for visible light dispersion. Spectral line profiles were obtained by a fast framing camera. It was shown that light is emitted from the excited ions and neutral atoms of Cu, Pb, Sr, Ba, Ti, and H within the first 50 ns after the beginning of the driving pulse. By analyzing the Doppler broadening of the observed spectral line profiles it was found that the ion and neutral atom temperature is ⩽0.8 eV. Analysis of the Stark broadening of the Hα and Hβ spectral lines showed the absence of a high (>1 kV/cm) electric field which could be developed at the ...

Ferroelectric plasma sources and their applications

We review our experimental studies of ferroelectric plasma sources and their applications. Using various diagnostics, it was shown that the source of the charged particle emission from the ferroelectric is surface plasma. This plasma is formed as a result of an incomplete discharge on the surface of the ferroelectric sample. The process of the plasma formation is accompanied by desorption of neutrals from the ferroelectric surface. It was shown that the parameters of the plasma and the neutral flow strongly depend on the polarization state of the ferroelectric material and on the parameters of the driving pulse. The lifetime of ferroelectric plasma sources was also studied. Electron beams with current amplitude of a few kiloamperes were generated with rep-rate up to 10 Hz under the application of accelerating pulses with amplitudes of 25-250 kV. Operation of the electron diode with and without plasma prefilling was demonstrated. Data concerning the uniformity of the extracted electron beam and the potential distribution in the diode are presented. In addition, we present data concerning an enhanced emission mode of the ferroelectric cathode and its application as a promising source of heavy ions. Results of applications of ferroelectric plasma sources in low-pressure high-current hollow-cathode discharge, as cathodes in relativistic magnetrons, as high-current switches and for generation of high-frequency modulated electron beams are presented as well.

Parameters of the plasma produced at the surface of a ferroelectric cathode by different driving pulses

Spectroscopic investigations of the properties of a plasma produced by a ferroelectric-plasma source are presented. The electron plasma density, the electron and ion temperature, and the density of desorbed neutrals near the ferroelectric surface are determined from spectral line intensities and profiles. Three different methods of surface plasma formation are analyzed using a simplified model for the plasma production. The model predicts the total amount of charge in the plasma to be proportional to the dielectric constant of the ferroelectric material. Also, the model shows a strong dependence of the plasma parameters on the resistivity of the plasma transition layer. A maximal plasma density of ∼1015cm−3 is achieved when the electrons that were attached by the driving field to the ferroelectric surface are released from the surface owing to driving pulse sharp decay and ionized heavy atoms desorbed from the ferroelectric.

Characterization of a channel spark discharge and the generated electron beam

We report on an experimental study of a channel spark discharge (CSD) and the generated electron beam. The CSD was operated at a discharge voltage Ud⩽30kV and a discharge current Id⩽3.5kA. The CSD system consists of a glass tube placed between a hollow cathode and a grounded anode electrode. The parameters of the CSD operation, the potential distribution along the glass tube, and the generated beam were studied by electrical, optical, and spectroscopic diagnostics in the Ar gas pressure range of P=0.005–2Pa. At P⩾0.5Pa, electrons with energy ∼eUd appeared prior to the start of the main CSD with a current amplitude ⩽10−4Id. These high-energy electrons are responsible for the initiation of the CSD inside the glass tube. The generation of the electron beam which was composed of low-energy electrons with a current amplitude up to 3kA occurred during a fast fall in the discharge voltage. Decreasing the Ar gas pressure below 0.1Pa allows one to increase significantly the beam duration and the part of the high-e...

Dense plasma formation on the surface of a ferroelectric induced by a driving pulse with a fast fall time

Experimental results are presented of dense plasma formation on the surface of a BaTi-based ferroelectric sample during the fall time of a driving pulse. A negative or positive driving pulse (⩽14 kV), with a slow rise time (∼450 ns) and a fast fall time (40–200 ns), was applied to the rear electrode of the ferroelectric. It was found by different electrical, optical, and spectroscopic diagnostics that this method allows one to form a plasma with a larger density (∼3×1013 cm−3) as compared with that formed by a driving pulse with a fast rise time (⩽4×1012 cm−3). It was shown that the shorter the fall time of the driving pulse the more intense plasma formation occurs. The most uniform and dense plasma formation occurs with a positive driving pulse. In addition, it was found that the shorter the fall time of the positive driving pulse the larger are the current amplitude, the energy, and the divergence of the emitted electrons. The obtained results are discussed in terms of the surface plasma formation and t...

Ion beam generation in a diode with a ferroelectric anode

In this article experimental results of the application of a ferroelectric anode for the generation of ion beams are presented. The ferroelectric anode was made of a solid solution of Sr, Ba, Ti, Nb, Pb, and O. Its front side was covered by a grounded Cu strip electrode. The ion beam generation was studied in a planar diode powered by a high-voltage generator with accelerating voltage ⩽300 kV and pulse duration ⩽400 ns. The source of the ion beam was found to be the plasma which was formed on the front anode surface. This plasma was formed by a driving pulse with an amplitude ⩽18 kV and pulse duration of ∼400 ns which was applied to the rear Cu disk electrode prior to the application of the accelerating pulse. The generation of ion beams with current amplitude up to 150 A was demonstrated in the plasma prefilled mode of the diode operation. It was found that the generated ion beam consists of light (H+,C+,O+) and heavy (Ti+,Cu+,Sr+) ions. In addition, it was shown that the application of a reflex triode s...

High-frequency electron beam modulation by a ferroelectric cathode with anomalous plasma resistance

Spectroscopic measurements are reported of the plasma formed inside a cathode having a ferroelectric source incorporated in it. These measurements were performed during the generation of a high-frequency modulated electron beam in a planar diode with the above cathode. It was found that there is a spatially periodic structure in the plasma density, electric field, and electron energy in the plasma in the longitudinal direction from the ferroelectric surface. The plasma density, electric field, and electron energy vary in the range of 5×1013–5×1014 cm−3, 0–1 kV/cm, and 2–30 eV, respectively. Also, it was found that the plasma electron temperature is ∼8 eV in the vicinity of the ferroelectric surface and ∼2 eV in the bulk of the plasma. To explain the obtained experimental data a qualitative model is suggested. The model is based on fast periodic appearance of anomalous plasma resistance due to generation of ion-acoustic instability. The latter is controlled by the ratio between the velocities of the curren...

Electron beam generation in a diode with different ferroelectric cathodes

We present experimental results of electron beam generation in a diode with cathodes made of BaTi solid solution and prepoled and unpoled PZT ferroelectrics without a screening grid in front of them. The diode operates with an accelerating pulse of ∼200 kV and ∼300 ns duration. It was found that although a surface plasma is always formed as a result of the application of a driving pulse, the beginning of the electron emission does not always coincide with the start of the accelerating pulse. Namely, it was shown that the application of the accelerating pulse at the same time with the driving pulse leads to simultaneous electron emission from the surface plasma only in the case of coincidence of the driving and accelerating electric field directions. In the opposite case, electron emission starts only at the end or at the fall of the driving pulse for the BaTi and PZT samples, respectively. Also, it was found that the electron beam current density distribution corresponds to the plasma emission spots which...

Investigation of a density modulated electron beam emitted by a ferroelectric plasma cathode

We present experimental results of the generation of a high-frequency modulated electron beam in a diode with a ferroelectric plasma cathode. The energy of electrons in the modulated beam is significantly higher than that obtained in previous experiments, reaching 150 keV. The maximum amplitude of the modulated beam current reaches 65 A, which corresponds to a beam power of 4.5 MW. Data concerning the influence of the diode geometry and the accelerating voltage on the electron energy and the amplitude of the modulated beam current are presented. It was found that the beam modulation is caused by the variation of the beam electron density, and that it has uniform cross-sectional electron beam current density distribution. Efficient transport of the modulated electron beam in a guiding external magnetic field without distortion of its waveform is demonstrated. The electron beam modulated at 190 MHz with an amplitude of 25 A was transported in the magnetic field (0.3–3 kG) along a distance of 50 cm. In addit...

High-frequency electron beam modulation, transportation and its interaction with slow-wave structure

We present new experimental results of the generation of a high-frequency modulated electron beam in a diode with a ferroelectric plasma cathode. The energy of electrons in the modulated beam is significantly higher than that obtained in previous experiments, reaching 150 keV. The maximum amplitude of the modulated beam current reaches 65 A, which corresponds to a beam power of 4.5 MW. Efficient transport of the modulated electron beam in a guiding external magnetic field without distortion of its waveform is demonstrated. In addition, it was shown that the modulated beam could be efficiently transported through a slow wave structure without the application of the external magnetic field.