Abstract: A model of cathode spots in high-current vacuum arcs is developed, with account of the plasma cloud left over from a previously existing spot, all mechanisms of current transfer to the cathode surface, including the contribution of the plasma produced by ionization of the metal vapor emitted in the spot, and the Joule heat generation in the cathode body The simulation results allow one to clearly identify the different phases of life of an individual spot: the ignition, the expansion over the cathode surface, and the thermal explosion The expansion phase is associated with a nearly constant maximum temperature of the cathode, which occurs at the surface and is approximately 4700–4800 K Thermal explosion is a result of thermal instability (runaway), which develops below the cathode surface when the Joule heating comes into play The development of the spot is interrupted if the plasma cloud has been extinguished: the spot is destroyed by heat removal into the bulk of the cathode due to thermal conduction Therefore, different scenarios are possible depending on the time of action of the cloud: the spot may be quenched before having been formed or during the expansion phase, or even at the initial stage of thermal explosion

Abstract: Here, we investigate, through parametrically optimized macroscale simulations, the field electron emission from arrays of carbon nanotube (CNT)-coated Spindts towards the development of an emerging class of novel vacuum electron devices. The present study builds on empirical data gleaned from our recent experimental findings on the room temperature electron emission from large area CNT electron sources. We determine the field emission current of the present microstructures directly using particle in cell (PIC) software and present a new CNT cold cathode array variant which has been geometrically optimized to provide maximal emission current density, with current densities of up to 11.5 A/cm2 at low operational electric fields of 5.0 V/μm.

Abstract: The effect of an electron extraction electrode on electron emission for a high-performance electron beam was studied using vertically aligned carbon nanotube emitters as a cold cathode. For the lower electron emission regime (anode current less than 1 mA), the gate electrode structure and materials used had little effect on the electron emission current. However, at the higher electron emission regime (anode current higher than 1 mA), the gate electrode materials and structure do begin to deviate from an ideal Fowler–Nordheim plot by the thermal and electrostatic load on the gate electrode, especially for the small cathode area. The gate mesh bends upward under a higher current load, which then increases the gate leakage current. The upward bending in the gate mesh electrode could reduce the effective electric field by increasing the gate to cathode distance, resulting in saturation of the electron emission current. For higher electron emission currents on the anode, a gate electrode comprising a lower th...

Abstract: The tandem hollow cathode discharge, formulated by arranging two discharges in series, is an important method used to increase the irradiance of a hollow cathode discharge. In this paper, based on a two-dimensional fluid model we studied a five-layer tandem hollow cathode discharge, with three hollow electrodes stacked together and separated by the insulators to obtain the configuration of anode/insulator/cathode/insulator/anode from the top to the bottom. In the model, the thickness of both electrodes and insulators is set at 1 cm and the diameter of the hollow cavity is 2 cm. The pressure effect on the discharge properties is investigated with gas pressure ranges from 100 Pa to 5 kPa. The gap voltage first decreases, reaching a minimum sustaining voltage at 1 kPa, and then increases. Based on the two-dimensional electron density distributions, the discharges parameters (including the electron density, ion density, electric potential, and electric field) of one integrated hollow cathode discharge at 1 kP...

Abstract: We present a new surface structure-dependent cold cathode material capable of sustaining high electron emission current suitable for next-generation low turn-on field-emission devices. The low turn-on electric field for electron emission in the cathode materials is critical, which facilitates the low-power room-temperature operation, a key factor required by the industrial sector. We demonstrate the facile synthesis of polypyrrole (PPy)/tin oxide (SnO2)-based core–shell hybrid cold cathode materials for large area applications. The technique used here is based on a simple and economical method of surfactant-mediated polymerization. The coupled investigation of X-ray diffraction along with electron microscopy reveals the formation of rutile phase SnO2 nanoparticles of size ∼15 nm. These SnO2 nanoparticles act as nucleation sites for the growth of PPy nanofibers, resulting in encapsulated SnO2 nanoparticles in the PPy amorphous matrix. The coupling of spherical-shaped core–shell structures of PPy/SnO2 resul...

Abstract: The results from studies of an electric discharge between a metal cathode and liquid anode at atmospheric pressure are presented. We investigate the discharge shape, the plasma emission spectrum, the electron concentration and temperature, and the molecule temperature; we analyze the continuous emission in the plasma spectrum and perform infrared thermography.

Abstract: The data on the measured static breakdown voltages and pre-breakdown currents flowing in the main gap of a two-section, sealed-off thyratron with a cold-cathode TPI1-10k/50 are presented. It is shown that pre-breakdown current in the lower section appears at lower voltages than in the upper section. A few methods are proposed for increasing the thyratron breakdown voltage via re-distribution of the voltage between the sections using capacitive and resistive voltage dividers. It is demonstrated that either the self-capacitance of one of the sections or the resistance due to the pre-breakdown current flow could serve as one of the arms of the divider.

Abstract: An investigation of the process of electrical strength recovery is performed using demountable devices and a TPI-10k/50 two-section, cold-cathode, sealed-off thyratron. The method of forced removal of the discharge burning products is used via a non-self-sustained discharge immediately after a breakdown in the thyratron. Measurements of the non-self-sustained discharge current allow estimating the time of the electrical strength recovery in the thyratron sections.

Abstract: This paper is devoted to studying how the inter-electrode distance affects the voltage drop across electrodes, the cathode sheath thickness, and the axial distribution of plasma parameters. The experiment demonstrates the simultaneous growth of both the voltage drop across the electrodes and the cathode sheath thickness when on increasing the gap the anode is moved away from the cathode while remaining in the negative glow. This effect is most clearly pronounced under low gas pressure and high current values when the negative glow length is large. The discharge axial structure dynamics is studied with the Langmuir probe technique and with the OOPIC Pro code. The inter-electrode gap growth with the current fixed is found to be accompanied by the plasma concentration increase in the negative glow. The positive plasma potential is shown to cause the current to the grounded anode to be transported by fast electrons accelerated in the cathode sheath. Moving the anode away from the cathode through the negative ...

Abstract: This paper deals with the investigations of the sealed-off hold-cathode thyratron (pseudospark switch) TPI1-10k/50, which is commercially produced by the Pulsed Technology Ltd., Ryazan, Russia. The trigger unit of the switch is based on a low-current auxiliary glow discharge. The new method for the switch triggering is proposed. The essence of the method is that the thyratron grid and the hollow cathode of the auxiliary discharge has to be grounded and the trigger pulse is applied to the ring anode of the trigger unit. In the proposed method, an undesirable high-voltage spike at the thyratron grid, which can appear with a usage of the other methods of triggering, is absent. It is shown that to trigger the thyratron a critical pulsed current to the main cathode cavity at a level of 0.8 A and higher should be provided. When the current exceeds the critical value, the jitter in the delay time to triggering falls in a range of 10 ns. This means that the method of triggering can be used in a variety of applica...

Abstract: WO2 nanowires have great potential as cold cathode materials because they exhibit excellent field-emission properties in terms of their low work function and high conductivity. Considering the requirements of the practical applications in large-area cold-cathode devices, such as X-ray source and panel display, these nanostructures are desired to be fabricated on glass substrate and integrated into devices. It is best known that the studies on WO2 nanowire cold cathode arrays grown on glass-substrate are absent so far, which remains a challenge for the researchers. In the current study, procedures for fabrication of WO2 nanowire cold cathode arrays, which consist of 22000 separated patterns on 1.2 in. glass wafer are developed. It is found that the turn-on and threshold field of the nanowire arrays are, respectively, 6.6 and 9.3 V µm−1. In addition, the performance of the cold cathode arrays is strongly affected by the distribution of the nanowire density as well as the thickness of Al electrode. By modifying the fabrication techniques, over 82% patterns can contribute to the emission, whereby a maximum current density can reach 1.89 mA cm−2. Such a value can fulfill the basic requirement of the large-area cold cathode devices. The research can pave the way for fabrication of high-performance cold cathode devices using glass-substrates.

Abstract: In this paper, a carbon fiber array cathode was constructed and the application in a hard-tube magnetically insulated transmission line oscillator (MILO) was investigated. The performance was compared with a traditionally used polymer velvet cathode in the same conditions, where applied electric power ranged from 9 GW to 28 GW and microwave with power level of several GW was the output. The MILO worked on single shot mode or repetitive mode at 5 Hz. For both cathodes, the central frequencies of output microwaves are in the L-band, and the pulse durations (full width at half maximum) range from 25 to 50 ns. Experimental results show that the pulse duration of output microwave of the carbon fiber array cathode is shorter than the velvet cathode, and the power conversion efficiency is also somewhat lower than the velvet cathode. Although the performance testing results show that this carbon fiber array cathode is somewhat not as good as the traditional velvet cathode in the present state, the reasons for the...

Abstract: A cold cathode arc discharge filament based multicusp H- ion source (HNIS) has been developed using an innovative low power igniter system working in a glow discharge regime to achieve a longer lifetime of the filament. This HNIS is cesium-free and its experimental prototype generates a maximum H- ion beam (HNIB) current of 12 mA at 50 keV beam energy in pulse mode with a peak arc power of 27 kW using the triode extraction system. This article presents the results of initial commissioning of the HNIS and steering magnetic field used to separate out the co-extracted electrons from HNIB, verified through experiments and 3-D ion beam simulations.

Abstract: The invention discloses a flat plate X-ray source using a temperature-sensitive nanowire cold cathode and a preparation method thereof. The flat plate X-ray source comprises a cathode substrate, an anode substrate, and a high-voltage insulation isolator; the cathode substrate and the anode substrate are opposite to and parallel to each other, the high-voltage insulation isolator is disposed at the edge of the cathode substrate and the anode substrate, and a cavity is formed by enclosing of the high-voltage insulation isolator, the cathode substrate, and the anode substrate; one side, which faces the anode substrate, of the cathode substrate is provided with a nanowire cold cathode, and the nanowire cold cathode is provided with zinc oxide nano wires, copper oxide nano wires, tungsten oxide nano wires, molybdenum oxide nano wires, iron oxide nano wires, titanium oxide nano wires, or tin oxide nano wires. Compared with the prior art, the flat plate X-ray source is advantageous in that, through controlling the temperature of the nanowire cold cathode, under the condition that the spacing between the cathode substrate and the anode substrate of the flat plate X-ray source is not changed, regulation of working voltage and current and radiation dose rate of the flat plate X-ray source is achieved, limitation of current regulation of the flat plate X-ray source is reduced, and application scope of the flat plate X-ray source is enlarged.

Abstract: The invention discloses a spiral-band-shaped electron beam cold cathode radiation source which relates to the technical field of microwave, millimeter wave, submillimeter wave and tera-hertz electric vacuum device. The spiral-band-shaped electron beam cold cathode radiation source comprises a spiral-band-shaped electron beam cold cathode electron gun, a periodical structure metal housing, a collecting electrode and a guiding magnetic field generator, wherein the spiral-band-shaped electron beam cold cathode electron gun is composed of a cathode block, a cathode transmitting surface, an anode block and an electron gun packaging insulator. The cathode transmitting surface is rectangular. The lower surface of the anode block is an oblique surface which inclines to the right lower side. The anode block is arranged at the right upper part of the cathode block. The periodical structure meta housing is provided with an electron beam channel which penetrates through the left end and the right end of the periodical structure metal housing. The middle part of the electron beam channel is provided with a high-frequency structure which extends along the axial direction of the electron beam channel. The collecting electrode, the electron beam channel and the cathode transmitting surface are in a straight line. The invention provides the spiral-band-shaped electron beam cold cathode electron gun which has advantages of simple structure, long service life and excellent performance. Energy is generated through interaction between electron beam longitudinal speed and a high-frequency field, thereby realizing electromagnetic radiation.

Abstract: The invention relates to a CT system and a cold cathode X-ray tube thereof. The cold cathode X-ray tube comprises a shell, an anode and a circulating assembly, wherein the shell is provided with a cavity, a first mounting hole and a second mounting hole, and the cavity communicates with the first mounting hole and the second mounting hole respectively; the cavity has a vacuum degree; a part of the anode is positioned in the cavity, and two ends of the anode stretch into the first mounting hole and the second mounting hole respectively; the circulating assembly is connected to the two ends of the anode respectively, and the circulating assembly drives a cooling liquid to come in and out of an accommodating cavity in a circulating manner. According to the CT system and the cold cathode X-ray tube thereof, due to the fact that the circulating assembly is connected to the two ends of the anode respectively, and the cooling liquid comes in and out the accommodating cavity through the circulating assembly, heat generated when electron beams are bombarded on the anode can be taken out of the accommodating cavity through the cooling liquid to be quickly cooled, so that the problem, that the heat dissipation performance of the anode is relatively low, of the cold cathode X-ray tube is solved.

Abstract: The specifics of operating a metal-ceramic TPI1-10k/50 thyratron in electric circuits with capacitance, inductance, and active resistance have been examined under circuit parameters that establish oscillatory current. Experiments have been performed at an anode voltage as high as 30 kV, a forward current of up to 7.6 kA, and a length of the first current half-period that varies from 0.38 to 1.9 μs. The data on operating modes in which this thyratron may handle a backward current wave and when current interruption is observed in the second half-period have been obtained. It has been demonstrated that a certain current flows through the thyratron in the backward direction during the interruption process. The amplitude of this current and the maximum backward voltage at the thyratron define whether the current is interrupted or repeat back-voltage device breakdown occurs. If the maximum backward current is on the level of several hundred amperes, complete current interruption occurs at backward voltages of up to 12 kV. The physical mechanisms of current interruption have been discussed.

Abstract: The paper reports on azimuthal and radial distributions of the ion saturation current density measured with a single cylindrical and a plane probe in the plasma of a low-pressure (≈1 Pa) pulsed non-self-sustained glow discharge with a large (0.21 m3) hollow cathode at discharge currents higher than 100 A. It is shown that increasing the discharge operating voltage and decreasing the operating pressure in the range 0.4–1 Pa improves the uniformity of the ion current density distribution.

Abstract: In this work, design and construction of a DC cold cathode Penning ion source is described. It consists of cylindrical hollow anode and two movable disc cathodes that are placed symmetrically at tw...

Abstract: The utility model belongs to the technical field of X ray image, a tomography system and tomoscan control circuit thereof is provided. The utility model discloses an adopt the tomoscan control circuit who sends X ray source array and high voltage dc source including drive module, a plurality of high -pressure control module, cold cathode field in the tomography system, send exposure time series signal to drive module by the detector of tomography system, by drive module according to the single pulse signal of exposure time series signal output multichannel, control the transmission chronogenesis that X ray source array was sent to the cold cathode field according to the single pulse signal of multichannel respectively by a plurality of high -pressure control modules to make a plurality of cold cathode fields send the X ray source and in proper order to target object transmission X ray, owing to adopt the full static scanning mode of electronic type, consequently practiced thrift the cost of the rotatory frame of high accuracy, and can not have the pseudo - shadow of motion in the imaging process, simultaneously, owing to adopt pulse exposure mode, thus avoided invalid radiation does's production in the scanning process.

Abstract: We have studied the thermal regime of a self-heated hollow cathode in combined low-current (1–5 A) dc discharge and high-current (up to 100 A) pulsed-periodic discharge and the influence of the pulsed parameters on the current-voltage characteristic of the high-current discharge. It has been shown that, after the application of a voltage pulse (200–500 V), the discharge current attains its peak value and is stabilized over a time of ~100 μs. The discharge voltage in the quasi-stationary discharge stage exceeds the continuous discharge voltage at the same current by many times and depends on the mean value of the current in the discharge gap. The interpretation of the form of the I–V characteristics of the pulsed discharge is based on the dynamics of heating and cooling of the cathode surface layer and on the variations in the integral temperature of the cathode.

Abstract: The X-ray tube disclosed herein includes an electron emission part including an electron emission element using a cold cathode; an anode part having an anode surface with which an electron emitted from the electron emission part collides; and a focusing structure disposed between the electron emission part and a target part disposed on the anode surface. The focusing structure has a plurality of focal point areas that are applied with a voltage in a mutually independent manner. The electron emission part has first and second electron beam emission areas that are on/off controlled in a mutually independent manner. The X-ray tube is designed in such a way that a collision area of the electron beam emitted from each of the first and second electron beam emission areas on the anode surface moves in response to a voltage applied to the focusing structure.