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Author

A. Dunaevsky

Bio: A. Dunaevsky is an academic researcher from Technion – Israel Institute of Technology. The author has contributed to research in topics: Cathode & Plasma. The author has an hindex of 15, co-authored 34 publications receiving 1016 citations.
Topics: Cathode, Plasma, Diode, Cathode ray, Electron

Papers
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Journal ArticleDOI
TL;DR: The electron emission from ferroelectrics (FEE) is an unconventional electron emission effect as discussed by the authors, which is a tunneling emission current which screens uncompensated polarization charges, generated by a deviation of macroscopic spontaneous polarization from its equilibrium state under pyroelectric effect, piezoelectric effect, or polarization switching.
Abstract: Electron emission from ferroelectrics (FEE) is an unconventional electron emission effect. Methods of FEE excitation are quite different compared to classic electron emission from solids. Two kinds of FEE have been observed, “weak” and “strong.” “Weak” electron emission (current density 10−12–10−7 A/cm2) occurs from polar surfaces of ferroelectric materials in the ferroelectric phase only. A source of the electric field for “weak” FEE excitation is an uncompensated charge, generated by a deviation of macroscopic spontaneous polarization from its equilibrium state under a pyroelectric effect, piezoelectric effect, or polarization switching. The FEE is a tunneling emission current which screens uncompensated polarization charges. It is shown that the FEE is an effective tool for direct domain imaging and studies of electronic properties of ferroelectrics. “Strong” FEE, which is 10–12 orders of magnitude higher than “weak” FEE, achieves 100 A/cm2 and is plasma-assisted electron emission. Two modes of the sur...

333 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated different types of cathodes operating in an electron diode powered by a high-voltage generator (300 kV, 250 ns, 84 Ω, ⩽5 Hz) and found that the amount of the emitting centers and the time delay in the electron emission were dependent strongly on the accelerating electric field growth rate.
Abstract: We present results of the investigation of different types of cathodes operating in an electron diode powered by a high-voltage generator (300 kV, 250 ns, 84 Ω, ⩽5 Hz). The cathodes which have the same emitting area of 100 cm2 are made of metal–ceramic, carbon fibers, carbon fabric, velvet, or corduroy. We also tested carbon fibers and carbon fabric cathodes coated by CsI. It was shown that for all types of cathodes the electron emission occurs from the plasma which is formed as a result of a flashover of separate emitting centers. The amount of the emitting centers and the time delay in the electron emission were found to depend strongly on the accelerating electric field growth rate. Experimental data concerning the uniformity of the light emission from the cathode surface and divergence of the generated electron beams are presented. Data related to the general parameters of the diode, namely its impedance, power, and energy are given as well. For all the cathodes investigated the observed diode impedance indicated the existence of a quasistationary cathode plasma boundary for electron current density ⩽20 A/cm2. We present the dependencies of the average emitted electron current density and of the time delay in the electron emission on the number of generator shots. We also present data of the vacuum deterioration as a result of the tested cathodes operation. The obtained data are discussed within the framework of plasma formation as a result of cathode surface flashover.

156 citations

Journal ArticleDOI
TL;DR: In this article, the application of a high-voltage driving pulse to the surface of a ferroelectric sample causes a fast surface plasma formation, which occurs within a few nanoseconds from the start of the driving pulse.
Abstract: We present experimental results of plasma formation on the surface of ferroelectric samples. Different poled and unpoled ferroelectric samples having a disk or tube form and made of Pb(Zr, Ti)O3 or BaTiO3 were tested. Using fast framing photography and different electric probes it was found that the application of a high-voltage driving pulse to the ferroelectric sample causes a fast surface plasma formation. This plasma formation occurs within a few nanoseconds from the start of the driving pulse for all the tested ferroelectric samples and the methods of applying the driving pulse. It was found that reversing the polarization of a ferroelectric does not play a significant role in the process of the plasma formation. Parameters of the plasma and of the neutral flow formed during the plasma formation versus the polarity and the amplitude of the driving pulse are presented.

79 citations

Journal ArticleDOI
TL;DR: In this article, a detailed study of the spatial and temporal evolution of visible light emission from plasma formed on the surface of ferroelectrics and a printed-circuit board under the application of a high-voltage pulse is presented.
Abstract: We present a detailed study of the spatial and temporal evolution of visible light emission from plasma formed on the surface of ferroelectrics [Pb(Zr,Ti)O3 and BaTiO3] and a printed-circuit board under the application of a high-voltage pulse. For all samples studied, plasma formation occurs within the first 5 ns from the start of the high-voltage pulse. It is shown that the plasma appears at the edges of the front strip electrodes. Further, the plasma spreads along the dielectric surface covering it partially. It is found that the uniformity of the plasma and the distance of its propagation along the surface depend on the properties of the dielectric, the polarity and amplitude of the high-voltage pulse, and the vacuum conditions. A qualitative model which explains the observed experimental data is suggested.

55 citations

Journal ArticleDOI
TL;DR: In this paper, the operation of a planar diode with a large area (64 cm2) ferroelectric plasma cathode based on BaTiO3 ceramics is investigated under accelerating voltage of 200-350 kV and pulse duration of 250 ns.
Abstract: The operation of a planar diode with a large area (64 cm2) ferroelectric plasma cathode based on BaTiO3 ceramics is studied. Diode parameters and parameters of the generated electron beam are investigated under accelerating voltage of 200–350 kV and pulse duration of 250 ns. Parameters of the plasma, which forms on the surface of the ferroelectric cathode due to incomplete discharge, are reported as well. It is shown that the application of this cathode allows one to produce an electron beam simultaneously with application of the accelerating pulse. The generation of an electron beam with current density up to 20 A/cm2 and divergence of less than 1° is demonstrated. It is shown that diode operation is governed by parameters of the cathode plasma which fills the anode–cathode gap prior to application of the accelerating voltage pulse. By proper adjustment of the cathode and diode parameters the operation of the diode with almost constant impedance is achieved. Measurements of the potential distribution in ...

49 citations


Cited by
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Journal ArticleDOI
TL;DR: The electron emission from ferroelectrics (FEE) is an unconventional electron emission effect as discussed by the authors, which is a tunneling emission current which screens uncompensated polarization charges, generated by a deviation of macroscopic spontaneous polarization from its equilibrium state under pyroelectric effect, piezoelectric effect, or polarization switching.
Abstract: Electron emission from ferroelectrics (FEE) is an unconventional electron emission effect. Methods of FEE excitation are quite different compared to classic electron emission from solids. Two kinds of FEE have been observed, “weak” and “strong.” “Weak” electron emission (current density 10−12–10−7 A/cm2) occurs from polar surfaces of ferroelectric materials in the ferroelectric phase only. A source of the electric field for “weak” FEE excitation is an uncompensated charge, generated by a deviation of macroscopic spontaneous polarization from its equilibrium state under a pyroelectric effect, piezoelectric effect, or polarization switching. The FEE is a tunneling emission current which screens uncompensated polarization charges. It is shown that the FEE is an effective tool for direct domain imaging and studies of electronic properties of ferroelectrics. “Strong” FEE, which is 10–12 orders of magnitude higher than “weak” FEE, achieves 100 A/cm2 and is plasma-assisted electron emission. Two modes of the sur...

333 citations

Journal ArticleDOI
28 Apr 2005-Nature
TL;DR: It is reported that gently heating a pyroelectric crystal in a deuterated atmosphere can generate fusion under desktop conditions and it is anticipated that the system will find application as a simple palm-sized neutron generator.
Abstract: Many methods of reproducing nuclear fusion — the process that powers the Sun — at the table-top scale have been tried, but failed to convince. Remember ‘cold fusion’? More recently, fusion linked to sonoluminescence is still controversial. Now comes a claim from the labs of the University of California at Los Angeles of unequivocal evidence of nuclear fusion in a simple room-temperature experiment. They report that gently heating a pyroelectric crystal — material that becomes charged when heated — causes ionization of a surrounding deuterium gas. The ions bombard a deuterated solid target with such energy that a large neutron signal is detected, a hallmark of deuterium fusion. Though not a viable power source, ‘crystal fusion’ may find application as a generator of neutrons for imaging technology. While progress in fusion research continues with magnetic1 and inertial2 confinement, alternative approaches—such as Coulomb explosions of deuterium clusters3 and ultrafast laser–plasma interactions4—also provide insight into basic processes and technological applications. However, attempts to produce fusion in a room temperature solid-state setting, including ‘cold’ fusion5 and ‘bubble’ fusion6, have met with deep scepticism7. Here we report that gently heating a pyroelectric crystal in a deuterated atmosphere can generate fusion under desktop conditions. The electrostatic field of the crystal is used to generate and accelerate a deuteron beam (> 100 keV and >4 nA), which, upon striking a deuterated target, produces a neutron flux over 400 times the background level. The presence of neutrons from the reaction D + D → 3He (820 keV) + n (2.45 MeV) within the target is confirmed by pulse shape analysis and proton recoil spectroscopy. As further evidence for this fusion reaction, we use a novel time-of-flight technique to demonstrate the delayed coincidence between the outgoing α-particle and the neutron. Although the reported fusion is not useful in the power-producing sense, we anticipate that the system will find application as a simple palm-sized neutron generator.

221 citations

Patent
10 May 2011
TL;DR: In this article, a semiconductor substrate processing system includes a top plate assembly disposed within the chamber above the substrate support, which includes first and second sets of plasma microchambers each formed into the lower surface of the topplate assembly.
Abstract: A semiconductor substrate processing system includes a chamber that includes a processing region and a substrate support. The system includes a top plate assembly disposed within the chamber above the substrate support. The top plate assembly includes first and second sets of plasma microchambers each formed into the lower surface of the top plate assembly. A first network of gas supply channels are formed through the top plate assembly to flow a first process gas to the first set of plasma microchambers to be transformed into a first plasma. A set of exhaust channels are formed through the top plate assembly. The second set of plasma microchambers are formed inside the set of exhaust channels. A second network of gas supply channels are formed through the top plate assembly to flow a second process gas to the second set of plasma microchambers to be transformed into a second plasma.

191 citations

Journal ArticleDOI
TL;DR: This paper presents a new mesoporous composite material developed at the Lawrence Berkeley National Laboratory with high-performance liquid chromatography-like properties that can be modeled on the basis of nanomaterials and chemical reactions.

174 citations

Journal Article
TL;DR: Jeong Young Park*,†, Miquel Salmeron*, and M. Jeong as mentioned in this paper, Daejeon 305-701, Republic of Korea ‡Graduate School of EEWS, Korea Advanced Institute of Science and Technology (KAIST).
Abstract: Jeong Young Park*,†,‡ and Miquel Salmeron* †Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, Republic of Korea ‡Graduate School of EEWS, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Republic of Korea Materials Sciences Division, Lawrence Berkeley National Laboratory, University of CaliforniaBerkeley, Berkeley, California 94720, United States Materials Science and Engineering Department, University of CaliforniaBerkeley, Berkeley, California 94720, United States

164 citations