Low-pressure, high-current hollow cathode with a ferroelectric plasma source

Abstract

We report the parameters of a hollow cathode with a ferroelectric plasma source incorporated in it. It was found that this source allows the ignition and sustaining of a high-current discharge (⩽1.4 kA, ⩽2×10−5 s) at N2 gas pressure of (3–5)×10−4 Torr. It was shown that ∼85% of the discharge current is emitted by the ferroelectric sample. The plasma in the cathode acquires a positive potential (⩽50 eV) with respect to the anode and the plasma density and temperature are ⩽8×1012 cm−3 and ⩽18 eV, respectively. Generation of an electron beam (0.3–1.6 kA, 300 ns) was demonstrated under an accelerating pulse ⩽300 kV.

Optimization of a low-pressure hollow-anode electrical discharge for generation of high-current electron beams

“…The FPS power supply (Blumlein generator) was excluded from the design and a fast rise time of the PFN pulse, which is required for the FPS operation, was achieved by low-inductive connection between the PFN and HA. In the present experiments, an FPS sample was made of BaTi solid solution with a dielectric constant ε ≈ 1600, in contrast to the ferroelectric sample with ε ≈ 170 that was used in previous experiments [12,15]. This allowed an efficient generation of incomplete surface discharges with a smaller amplitude of the voltage pulse supplied by the PFN generator as compared with the amplitude of the driving pulse supplied by the Blumlein generator.…”

“…Another approach that has been taken in developing electron sources is associated with the generation of electron beams of moderate current density, using sources with plasma production prior to the application of the accelerating pulse. As examples of such plasma sources, one can consider arc plasma sources [6], ferroelectric plasma sources (FPS) [7], hollow-cathode [8][9][10][11][12] and hollow-anode (HA) [10] sources.…”

Measuring the plasma density of a ferroelectric plasma source in an expanding plasma

“…1, is similar to other setups for study of FPS. [1][2][3][4][5][6][7][8][9][10] The ferroelectric plasma source consists of a ferroelectric disc Operation of the FPS with probes was observed by Andor I-Star ® ICCD camera.…”

“…Because of these reasons, most of the probe measurements in previous studies of FPS were done by biased probes placed behind a grounded grid, which helped to suppress the noise. [6][7][8][9] Measurements of the density of expanding plasma behind the grounded grid left some uncertainty in the original plasma density because of grid transparency, which is not easy to evaluate accurately. Consequently, reliable temporal profiles of the plasma density in the expanding FPS plasma were not obtained yet.…”

“…5 In the majority of experiments, plasma measurements were performed in expanding plasma by probes placed distantly from the FPS surface. 6,7,8,9 Although placed distantly, the probes are exposed to strong broadband electromagnetic noise from the surface discharge. Consequently, measurements of the ion saturation branch of the ampere-volt characteristics of a biased probe, where the probe signal is usually very low, become uncertain on the noise background of hundreds of millivolts.…”