Hollow Cathode Assembly Development for the HERMeS Hall Thruster

Science.gov (United States)

Sarver-Verhey, Timothy R.; Kamhawi, Hani; Goebel, Dan M.; Polk, James E.; Peterson, Peter Y.; Robinson, Dale A.

2016-01-01

To support the operation of the HERMeS 12.5 kW Hall Thruster for NASA's Asteroid Redirect Robotic Mission, hollow cathodes using emitters based on barium oxide impregnate and lanthanum hexaboride are being evaluated through wear-testing, performance characterization, plasma modeling, and review of integration requirements. This presentation will present the development approach used to assess the cathode emitter options. A 2,000-hour wear-test of development model Barium Oxide (BaO) hollow cathode is being performed as part of the development plan. Specifically this test is to identify potential impacts cathode emitter life during operation in the HERMeS thruster. The cathode was operated with a magnetic field-equipped anode that simulates the HERMeS hall thruster operating environment. Cathode discharge performance has been stable with the device accumulating 743 hours at the time of this report. Observed voltage changes are attributed to keeper surface condition changes during testing. Cathode behavior during characterization sweeps exhibited stable behavior, including cathode temperature. The details of the cathode assembly operation of the wear-test will be presented.

Hollow cathode for positive ion sources

International Nuclear Information System (INIS)

Schechter, D.E.; Kim, J.; Tsai, C.C.

1979-01-01

Development to incorporate hollow cathodes into high power ion sources for neutral beam injection systems is being pursued. Hollow tube LaB 6 -type cathodes, similar to a UCLA design, have been constructed and tested in several ORNL ion source configurations. Results of testing include arc discharge parameters of >1000 and 500 amps for 0.5 and 10 second pulse lengths, respectively. Details of cathode construction and additional performance results are discussed

Design and experiment of high-current low-pressure plasma-cathode e-gun

International Nuclear Information System (INIS)

Xie Wenkai; Li Xiaoyun; Wang Bin; Meng Lin; Yan Yang; Gao Xinyan

2006-01-01

The preliminary design of a new high-power low pressure plasma-cathode e-gun is presented. Based on the hollow cathode effect and low-pressure glow discharge empirical formulas, the hollow cathode, the accelerating gap, and the working gas pressure region are given. The general experimental device of the low-pressure plasma cathode electron-gun generating high current density e-beam source is shown. Experiments has been done in continuous filled-in gases and gases-puff condition, and the discharging current of 150-200 A, the width of 60 μs and the collector current of 30-80 A, the width of 60 μs are obtained. The results show that the new plasma cathode e-gun can take the place of material cathode e-gun, especially in plasma filled microwave tubes. (authors)

Development and Testing of High Current Hollow Cathodes for High Power Hall Thrusters

Science.gov (United States)

Kamhawi, Hani; Van Noord, Jonathan

2012-01-01

NASA's Office of the Chief Technologist In-Space Propulsion project is sponsoring the testing and development of high power Hall thrusters for implementation in NASA missions. As part of the project, NASA Glenn Research Center is developing and testing new high current hollow cathode assemblies that can meet and exceed the required discharge current and life-time requirements of high power Hall thrusters. This paper presents test results of three high current hollow cathode configurations. Test results indicated that two novel emitter configurations were able to attain lower peak emitter temperatures compared to state-of-the-art emitter configurations. One hollow cathode configuration attained a cathode orifice plate tip temperature of 1132 degC at a discharge current of 100 A. More specifically, test and analysis results indicated that a novel emitter configuration had minimal temperature gradient along its length. Future work will include cathode wear tests, and internal emitter temperature and plasma properties measurements along with detailed physics based modeling.

Emission mechanism in high current hollow cathode arcs

International Nuclear Information System (INIS)

Krishnan, M.

1976-01-01

Large (2 cm-diameter) hollow cathodes have been operated in a magnetoplasmadynamic (MPD) arc over wide ranges of current (0.25 to 17 kA) and mass flow (10 -3 to 8 g/sec), with orifice current densities and mass fluxes encompassing those encountered in low current steady-state hollow cathode arcs. Detailed cathode interior measurements of current and potential distributions show that maximum current penetration into the cathode is about one diameter axially upstream from the tip, with peak inner surface current attachment up to one cathode diameter upstream of the tip. The spontaneous attachment of peak current upstream of the cathode tip is suggested as a criterion for characteristic hollow cathode operation. This empirical criterion is verified by experiment

Geometrical Aspects of a Hollow-cathode Magnetron (HCM)

International Nuclear Information System (INIS)

Cohen, Samuel A.; Wang, Zhehui

1998-01-01

A hollow-cathode magnetron (HCM), built by surrounding a planar sputtering-magnetron cathode with a hollow-cathode structure (HCS), is operable at substantially lower pressures than its planar-magnetron counterpart. We have studied the dependence of magnetron operational parameters on the inner diameter D and length L of a cylindrical HCS. Only when L is greater than L sub zero, a critical length, is the HCM operable in the new low-pressure regime. The critical length varies with HCS inner diameter D. Explanations of the lower operational pressure regime, critical length, and plasma shape are proposed and compared with a one-dimension diffusion model for energetic or primary electron transport. At pressures above 1 mTorr, an electron-impact ionization model with Bohm diffusion at a temperature equivalent to one-half the primary electron energy and with an ambipolar constraint can explain the ion-electron pair creation required to sustain the discharge. The critical length L sub zero is determined by the magnetization length of the primary electrons

Diagnostic of a Hollow Cathode Radio-Frequency Plasma Excited in Organosilicon HMDSO, used for Barrier Anti Corrosion Thin Films Deposition

International Nuclear Information System (INIS)

Saloum, S.; Naddaf, M.

2010-01-01

In this work, remote hollow cathode RF plasma, generated from the monomer hexamethyledisiloxane (HMDSO), as a precursor, and argon as a feed gas, and the plasma mixture HMDSO/O 2 have been studied, as a function of different plasma parameters such as: RF applied power (100-300 W), HMDSO flow rate (2-32 sccm), time deposition (5-20 minutes), and oxygen fraction in HMDSO/O 2 mixture (0-0.9). Plasma diagnostic and prepared thin films characterization have been investigated. (author)

Barium Depletion in Hollow Cathode Emitters

Science.gov (United States)

Polk, James E.; Capece, Angela M.; Mikellides, Ioannis G.; Katz, Ira

2009-01-01

The effect of tungsten erosion, transport and redeposition on the operation of dispenser hollow cathodes was investigated in detailed examinations of the discharge cathode inserts from an 8200 hour and a 30,352 hour ion engine wear test. Erosion and subsequent re-deposition of tungsten in the electron emission zone at the downstream end of the insert reduces the porosity of the tungsten matrix, preventing the ow of barium from the interior. This inhibits the interfacial reactions of the barium-calcium-aluminate impregnant with the tungsten in the pores. A numerical model of barium transport in the internal xenon discharge plasma shows that the barium required to reduce the work function in the emission zone can be supplied from upstream through the gas phase. Barium that flows out of the pores of the tungsten insert is rapidly ionized in the xenon discharge and pushed back to the emitter surface by the electric field and drag from the xenon ion flow. This barium ion flux is sufficient to maintain a barium surface coverage at the downstream end greater than 0.6, even if local barium production at that point is inhibited by tungsten deposits. The model also shows that the neutral barium pressure exceeds the equilibrium vapor pressure of the impregnant decomposition reaction over much of the insert length, so the reactions are suppressed. Only a small region upstream of the zone blocked by tungsten deposits is active and supplies the required barium. These results indicate that hollow cathode failure models based on barium depletion rates in vacuum dispenser cathodes are very conservative.

Geometrical aspects of a hollow-cathode planar magnetron

International Nuclear Information System (INIS)

Wang, Z.; Cohen, S.A.

1999-01-01

A hollow-cathode planar magnetron (HCPM), built by surrounding a planar sputtering-magnetron cathode with a hollow-cathode structure (HCS) [Z. Wang and S. A. Cohen, J. Vac. Sci. Technol. A 17, 77 (1999)], is operable at substantially lower pressures than its planar-magnetron counterpart. HCPM operational parameters depend on the inner diameter D and length L of its cylindrical HCS. Only when L is greater than L 0 , a critical length, is the HCPM operable in the new low-pressure regime. The critical length varies with HCS inner diameter D. Explanations of the lower operational pressure regime, critical length, and plasma shape are proposed and compared with a one-dimension diffusion model for energetic electron transport. At pressures above 1 mTorr, Bohm diffusion (temperature congruent primary electron energy), with an ambipolar constraint, can explain the ion - electron pair creation required to sustain the discharge. At the lowest pressure, ∼0.3 mTorr, collision-limited diffusion creates fewer ion - electron pairs than required for steady state and therefore cannot explain the experimental data. The critical length L 0 is consistent with the magnetization length of the primary electrons. copyright 1999 American Institute of Physics

The plasma properties and electron emission characteristics of near-zero differential resistance of hollow cathode-based plasma contactors with a discharge chamber

Energy Technology Data Exchange (ETDEWEB)

Xie, Kan, E-mail: xiekan@bit.edu.cn [School of Aerospace Engineering, Beijing Institute of Technology, Beijing 100081 (China); Farnell, Casey C.; Williams, John D. [Department of Mechanical Engineering, Colorado State University, Fort Collins, Colorado 80524 (United States)

2014-08-15

The formation of electron emission-bias voltage (I-V) characteristics of near-zero differential resistance in the cathodic plasma contactor for bare electrodynamic tether applications, based on a hollow cathode embedded in a ring-cusp ionization stage, is studied. The existence of such an I-V regime is important to achieve low impedance performance without being affected by the space plasma properties for a cathodic plasma contactor. Experimental data on the plasma structure and properties downstream from the ionization stage are presented as functions of the xenon flow rate and the electron emission current. The electrons were emitted from the cathode to the cylindrical vacuum chamber wall (r = 0.9 m) under ≈10{sup −5 }Torr of vacuum pressure. The ring-cusp configuration selected for the plasma contactor created a 125-Gauss axial field near the cathode orifice, along with a large-volume 50-Gauss magnitude pocket in the stage. A baseline ion energy cost of ≈300 eV/ion was measured in the ionization stage when no electrons were emitted to the vacuum chamber wall. In addition, the anode fall growth limited the maximum propellant unitization to below ≈75% in the discharge loss curves for this ion stage. Detailed measurements on the plasma properties were carried out for the no-electron emission and 3 A emission conditions. The experimental data are compared with 1-D models, and the effectiveness of the model is discussed. The four key issues that played important roles in the process of building the near-zero different resistance I-V regime are: a significant amount of ionization by the emission electrons, a decrease in the number of reflected electrons in the plume, the electron-temperature increment, and low initial ion energy at the source outlet.

Barium depletion in hollow cathode emitters

International Nuclear Information System (INIS)

Polk, James E.; Mikellides, Ioannis G.; Katz, Ira; Capece, Angela M.

2016-01-01

Dispenser hollow cathodes rely on a consumable supply of Ba released by BaO-CaO-Al 2 O 3 source material in the pores of a tungsten matrix to maintain a low work function surface. The examination of cathode emitters from long duration tests shows deposits of tungsten at the downstream end that appear to block the flow of Ba from the interior. In addition, a numerical model of Ba transport in the cathode plasma indicates that the Ba partial pressure in the insert may exceed the equilibrium vapor pressure of the dominant Ba-producing reaction, and it was postulated previously that this would suppress Ba loss in the upstream part of the emitter. New measurements of the Ba depletion depth from a cathode insert operated for 8200 h reveal that Ba loss is confined to a narrow region near the downstream end, confirming this hypothesis. The Ba transport model was modified to predict the depletion depth with time. A comparison of the calculated and measured depletion depths gives excellent qualitative agreement, and quantitative agreement was obtained assuming an insert temperature 70 °C lower than measured beginning-of-life values

Development of plasma cathode electron guns

Science.gov (United States)

Oks, Efim M.; Schanin, Peter M.

1999-05-01

The status of experimental research and ongoing development of plasma cathode electron guns in recent years is reviewed, including some novel upgrades and applications to various technological fields. The attractiveness of this kind of e-gun is due to its capability of creating high current, broad or focused beams, both in pulsed and steady-state modes of operation. An important characteristic of the plasma cathode electron gun is the absence of a thermionic cathode, a feature which leads to long lifetime and reliable operation even in the presence of aggressive background gas media and at fore-vacuum gas pressure ranges such as achieved by mechanical pumps. Depending on the required beam parameters, different kinds of plasma discharge systems can be used in plasma cathode electron guns, such as vacuum arcs, constricted gaseous arcs, hollow cathode glows, and two kinds of discharges in crossed E×B fields: Penning and magnetron. At the present time, plasma cathode electron guns provide beams with transverse dimension from fractional millimeter up to about one meter, beam current from microamperes to kiloamperes, beam current density up to about 100 A/cm2, pulse duration from nanoseconds to dc, and electron energy from several keV to hundreds of keV. Applications include electron beam melting and welding, surface treatment, plasma chemistry, radiation technologies, laser pumping, microwave generation, and more.

Theory of hollow cathode arc discharges. II. Metastable state balance inside the cathode. Application to argon

International Nuclear Information System (INIS)

Ferreira, C.M.; Delcroix, J.L.

1975-01-01

In the hollow cathode the metastable species are created by fast electrons, which are emitted by the cathode wall and injected in the plasma across a space-charge sheath, and destroyed by Maxwellian electrons. A detailed analysis of the different electronic destruction mechanisms in argon shows that the re-excitation up to 3p 5 4p states plays a very important role. Solutions of the metastable balance equation were obtained in a wide range of variation of the discharge parameters displaying the best conditions of operation to obtain high concentrations [fr

Long pulse, plasma cathode E-gun

International Nuclear Information System (INIS)

Goebel, D.M.; Schumacher, R.W.; Watkins, R.M.

1993-01-01

A unique, long-pulse E-gun has been developed for high-power tube applications. The Hollow-Cathode-Plasma (HCP) E-gun overcomes the limitations of conventional thermionic-cathode guns that have limited current density (typically ≤ 10 A/cm 2 ) or field-emission guns that offer high current density but suffer from short pulsewidth capability (typically 50 A/cm 2 ), long-pulse operation without gap closure, and also requires no cathode-heater power. The gun employs a low-pressure glow discharge inside a hollow cathode (HC) structure to provide a stable, uniform plasma surface from which a high current-density electron beam can be extracted. The plasma density is controlled by a low-voltage HC discharge pulser to produce the desired electron current density at the first grid of a multi-grid accelerator system. A dc high-voltage electron-beam supply accelerates the electrons across the gap, while the HC pulser modulates the beam current to generate arbitrary pulse waveforms. The electron accelerator utilizes a multi-aperture array that produces a large area, high perveance (>35 μpervs) beam consisting initially of many individual beamlets. The E-beam is normally operated without an applied magnetic field in the ion-focused regime, where the plasma produced by beam ionization of a background gas space-charge neutralizes the beam, and the Bennett self-pinch compresses the beamlets and increases the current density. The self-pinched beam has been observed to propagate over a meter without beam breakup or instabilities. The HCP E-gun has been operated at voltages up to 150 kV, currents up to 750 A, and pulse lengths of up to 120 μsec

Pulsed hollow cathode discharge: intense electron beam and filamentary plasma

International Nuclear Information System (INIS)

Modreanu, Gabriel

1998-01-01

This work deals with a transient hollow cathode discharge optimised by a preionization one and providing intense electron beams. It exists a preionization current value for which the pulsed discharge becomes a very straight and bright filament, well collimated on the discharge tube axis for some tenths of centimeters. A remarkable feature of this discharge is that, without internal metallic electrodes very pure plasma could be produced. Using self-biasing by the beam of a Faraday cup placed only few millimeters behind the anode, we deduced the beam electron's distribution function and its temporal behavior for two radial positions, on the axis and 1 millimeter off-axis, respectively. The real advantage of this measurement technique is the transient polarization character, which allows analysis very closely from the electron beam extraction hole. On the other side, using the emission spectroscopy, we have studied the plasma produced in electron beam - gas interaction and deduced the temporal evolution of the electron temperature. The temporal behavior of the filamentary plasma diameter shows a constriction at the last moments of the beam existence, followed by diffusion controlled expansion. The ambipolar diffusion coefficient corresponding to the estimated electron temperature describes quite well this expansion and allows a quantitative interpretation of the measured temperature diminution, with taking into account the preferential fast electrons escape. The analysis of both beam and post-beam plasma phases suggests potential applications of this robust, very reproducible and not expensive discharge also susceptible to be external monitored. The beam - target interaction could be used for PVD, elementary analysis and filamentary or point-like X-ray emission. (author) [fr

Dependence of electron peak current on hollow cathode dimensions and seed electron energy in a pseudospark discharge

International Nuclear Information System (INIS)

Cetiner, S. O.; Stoltz, P.; Messmer, P.; Cambier, J.-L.

2008-01-01

The prebreakdown and breakdown phases of a pseudospark discharge are investigated using the two-dimensional kinetic plasma simulation code OOPIC PRO. Trends in the peak electron current at the anode are presented as function of the hollow cathode dimensions and mean seed injection velocities at the cavity back wall. The plasma generation process by ionizing collisions is examined, showing the effect on supplying the electrons that determine the density of the beam. The mean seed velocities used here are varied between the velocity corresponding to the energy of peak ionization cross section, 15 times this value and no mean velocity (i.e., electrons injected with a temperature of 2.5 eV). The reliance of the discharge characteristics on the penetrating electric field is shown to decrease as the mean seed injection velocity increases because of its ability to generate a surplus plasma independent of the virtual anode. As a result, the peak current increases with the hollow cathode dimensions for the largest average injection velocity, while for the smallest value it increases with the area of penetration of the electric field in the hollow cathode interior. Additionally, for a given geometry an increase in the peak current with the surplus plasma generated is observed. For the largest seed injection velocity used a dependence of the magnitude of the peak current on the ratio of the hole thickness and hollow cathode depth to the hole height is demonstrated. This means similar trends of the peak current are generated when the geometry is resized. Although the present study uses argon only, the variation in the discharge dependencies with the seed injection energy relative to the ionization threshold is expected to apply independently of the gas type. Secondary electrons due to electron and ion impact are shown to be important only for the largest impact areas and discharge development times of the study

In situ plasma diagnostics study of a commercial high-power hollow cathode magnetron deposition tool

International Nuclear Information System (INIS)

Meng Liang; Raju, Ramasamy; Flauta, Randolph; Shin, Hyungjoo; Ruzic, David N.; Hayden, Douglas B.

2010-01-01

Using a newly designed and built plasma diagnostic system, the plasma parameters were investigated on a commercial 200 mm high-power hollow cathode magnetron (HCM) physical vapor deposition tool using Ta target under argon plasma. A three dimensional (3D) scanning radio frequency (rf)-compensated Langmuir probe was constructed to measure the spatial distribution of the electron temperature (T e ) and electron density (n e ) in the substrate region of the HCM tool at various input powers (2-15 kW) and pressures (10-70 mTorr). The T e was in the range of 1-3 eV, scaling with decreasing power and decreasing pressure. Meanwhile, n e was in the range of 4x10 10 -1x10 12 cm -3 scaling with increasing power and decreasing pressure. As metal deposits on the probe during the probe measurements, a self-cleaning plasma cup was designed and installed in the chamber to clean the tungsten probe tip. However, its effectiveness in recovering the measured plasma parameters was hindered by the metal layer deposited on the insulating probe tube which was accounted for the variation in the plasma measurements. Using a quartz crystal microbalance combined with electrostatic filters, the ionization fraction of the metal flux was measured at various input power of 2-16 kW and pressure of 5-40 mTorr. The metal ionization fraction reduced significantly with the increasing input power and decreasing gas pressure which were attributed to the corresponding variation in the ionization cross section and the residence time of the sputtered atoms in the plasma, respectively. Both the metal neutral and ion flux increased at higher power and lower pressure. The 3D measurements further showed that the ionization fraction decreased when moving up from the substrate to the cathode.

Compact Rare Earth Emitter Hollow Cathode

Science.gov (United States)

Watkins, Ronald; Goebel, Dan; Hofer, Richard

2010-01-01

A compact, high-current, hollow cathode utilizing a lanthanum hexaboride (LaB6) thermionic electron emitter has been developed for use with high-power Hall thrusters and ion thrusters. LaB6 cathodes are being investigated due to their long life, high current capabilities, and less stringent xenon purity and handling requirements compared to conventional barium oxide (BaO) dispenser cathodes. The new cathode features a much smaller diameter than previously developed versions that permit it to be mounted on axis of a Hall thruster ( internally mounted ), as opposed to the conventional side-mount position external to the outer magnetic circuit ("externally mounted"). The cathode has also been reconfigured to be capable of surviving vibrational loads during launch and is designed to solve the significant heater and materials compatibility problems associated with the use of this emitter material. This has been accomplished in a compact design with the capability of high-emission current (10 to 60 A). The compact, high-current design has a keeper diameter that allows the cathode to be mounted on the centerline of a 6- kW Hall thruster, inside the iron core of the inner electromagnetic coil. Although designed for electric propulsion thrusters in spacecraft station- keeping, orbit transfer, and interplanetary applications, the LaB6 cathodes are applicable to the plasma processing industry in applications such as optical coatings and semiconductor processing where reactive gases are used. Where current electrical propulsion thrusters with BaO emitters have limited life and need extremely clean propellant feed systems at a significant cost, these LaB6 cathodes can run on the crudest-grade xenon propellant available without impact. Moreover, in a laboratory environment, LaB6 cathodes reduce testing costs because they do not require extended conditioning periods under hard vacuum. Alternative rare earth emitters, such as cerium hexaboride (CeB6) can be used in this

Operational features and air plasma characteristics of a thermal plasma torch with hollow electrodes

International Nuclear Information System (INIS)

Hur, Min; Kim, Keun Su; Hong, Sang Hee

2003-01-01

The operational features and thermal plasma characteristics of a plasma torch with hollow electrodes are investigated based on their dependence on input current, gas flow rate and electrode diameter when air is used as a plasma gas. A plasma torch with a hollow cathode and anode has been designed and fabricated, and the arc voltages and thermal efficiencies are measured from its discharge. The newly modified similarity criteria are derived from the measured data related to torch performances. From the fact that these criteria successfully describe both the arc voltage and thermal efficiency behaviour of the torch, depending on its operating and geometrical parameters, it is proved that they can be usefully applied to the design and operation of high power torches. For the numerical modelling of the interior region of the torch, a cold flow analysis is employed along with a simplified balance equation of the Lorentz and gas dynamic drag forces in order to determine a cathode spot position on the cathode surface. The validity of this method is confirmed by comparison of the calculated and measured net powers. As a practically useful result of this analysis, carried out through this numerical and experimental work, it is suggested that low input current, high gas flow rate and relatively large electrode diameter are more favourable as appropriate operating conditions of the torch for the efficient treatment of hazardous organic wastes

Improved Rare-Earth Emitter Hollow Cathode

Science.gov (United States)

Goebel, Dan M.

2011-01-01

An improvement has been made to the design of the hollow cathode geometry that was created for the rare-earth electron emitter described in Compact Rare Earth Emitter Hollow Cathode (NPO-44923), NASA Tech Briefs, Vol. 34, No. 3 (March 2010), p. 52. The original interior assembly was made entirely of graphite in order to be compatible with the LaB6 material, which cannot be touched by metals during operation due to boron diffusion causing embrittlement issues in high-temperature refractory materials. Also, the graphite tube was difficult to machine and was subject to vibration-induced fracturing. This innovation replaces the graphite tube with one made out of refractory metal that is relatively easy to manufacture. The cathode support tube is made of molybdenum or molybdenum-rhenium. This material is easily gun-bored to near the tolerances required, and finish machined with steps at each end that capture the orifice plate and the mounting flange. This provides the manufacturability and robustness needed for flight applications, and eliminates the need for expensive e-beam welding used in prior cathodes. The LaB6 insert is protected from direct contact with the refractory metal tube by thin, graphite sleeves in a cup-arrangement around the ends of the insert. The sleeves, insert, and orifice plate are held in place by a ceramic spacer and tungsten spring inserted inside the tube. To heat the cathode, an insulating tube is slipped around the refractory metal hollow tube, which can be made of high-temperature materials like boron nitride or aluminum nitride. A screw-shaped slot, or series of slots, is machined in the outside of the ceramic tube to constrain a refractory metal wire wound inside the slot that is used as the heater. The screw slot can hold a single heater wire that is then connected to the front of the cathode tube by tack-welding to complete the electrical circuit, or it can be a double slot that takes a bifilar wound heater with both leads coming out

Emission characteristics of laser ablation-hollow cathode glow discharge spectral source

Directory of Open Access Journals (Sweden)

Karatodorov Stefan

2014-11-01

Full Text Available The emission characteristics of a scheme combining laser ablation as sample introduction source and hollow cathode discharge as excitation source are presented. The spatial separation of the sample material introduction by laser ablation and hollow cathode excitation is achieved by optimizing the gas pressure and the sample-cathode gap length. At these conditions the discharge current is maximized to enhance the analytical lines intensity.

Ion source using a hollow cathode discharge system and especially, particle accelerator comprising said source

International Nuclear Information System (INIS)

Mourier, Georges.

1975-01-01

An ion source provided with a hollow cathode discharge system is presented. The ion extraction system is designed in view of generating a beam directed towards a point of use located far from the point of ion production. Said source essentially comprises two cathodes facing each other, an anode at a continuous voltage with respect to the cathodes, a heated filament beyond the cathode on the path of the extracted beam, and a grid between said filament and cathode. The ion extraction is limited to a certain portion of the ions present inside the plasma, so as the discharge to continue to be sustained by itself. For that purpose pierced cathodes are used, with a transparency (the ratio of the hole area to the whole cathode area) not much higher than 50% [fr

Numerical simulation of the sustaining discharge in radio frequency hollow cathode discharge in argon

Energy Technology Data Exchange (ETDEWEB)

Jiang, Xin-Xian; He, Feng, E-mail: hefeng@bit.edu.cn; Ouyang, Ji-Ting [School of Physics, Beijing Institute of Technology, Beijing 100081 (China); Chen, Qiang, E-mail: lppmchenqiang@hotmail.com; Ge, Teng [Laboratory of Plasma Physics and Materials, Beijing Institute of Graphic Communication, Beijing 10081 (China)

2014-03-15

In this paper, a two-dimensional fluid model was developed to study the radio frequency (RF) hollow cathode discharge (HCD) in argon at 1 Torr. The evolutions of the particle density distribution and the ionization rate distribution in RF HCD at 13.56 MHz indicate that the discharge mainly occurs inside the hollow cathode. The spatio-temporal distributions of the ionization rate and the power deposition within the hollow cathode imply that sheath oscillation heating is the primary mechanism to sustain the RF HCD, whereas secondary electron emission plays a negligible role. However, as driving frequency decreases, secondary electron heating becomes a dominant mechanism to sustain the discharge in RF hollow cathode.

Hollow Cathode Studies for the Next Generation Ion Engines in JAXA

Science.gov (United States)

Ohkawa, Yasushi; Hayakawa, Yukio; Yoshida, Hideki; Miyazaki, Katsuhiro; Kitamura, Shoji; Kajiwara, Kenichi

The current status of experimental studies of hollow cathodes for the next-generation ion engines in the Aerospace Research and Development Directorate, JAXA is described. One of the topics on the hollow cathode studies is a life test of a discharge cathode. The keeper disk, orifice plate, and cathode tube of this discharge cathode are made of "high density graphite," which possesses much higher tolerance to ion impingement compared with conventional metal materials. The life test had started in March 2006 and the cumulative operation time reached 15,600 hours in April 2008. No severe degradation has been found both in the operation voltages and electrodes so far, and the test is favorably in progress. In addition to the life test of the discharge cathode, some experiments for design optimization of neutralizer cathodes have been performed. A life test of the neutralizer cathode is being started in June 2008.

Physics and applications of micro-plasmas in dielectric barrier and hollow cathode configurations

International Nuclear Information System (INIS)

Boeuf, J. P.; Pitchford, L. C.

2005-01-01

Non-equilibrium or non-thermal plasmas operate at low gas temperatures and this property make these plasmas very attractive in a number of applications, from etching and deposition in the microelectronics industry to plasma displays and pollution control. However, although it is quite easy to generate a large volume non-equilibrium plasma at pressure on the order or below 100 Pa, this is more of a challenge around atmospheric pressure. Large area plasma sources operating at atmospheric pressure represent a very cost-effective solution for material processing, light sources and other applications, and a large research effort has been devoted to the development of such sources in the last ten years. Dielectric Barrier Discharges (DBDs), where one or both electrodes are covered with a dielectric layer are good candidates for atmospheric non-equilibrium plasma generation because of their ability to limit the current and power deposition. It is also much easier to control an atmospheric discharge in a small volume. Therefore an atmospheric plasma source often consists of a number of micro-discharges arranged in a way that depends on the application. Even in DBDs with large electrode areas, the plasma is generally not uniform and consists in a large number of micro-discharges or filaments. In this lecture we present a discussion of the physical properties of non-equilibrium plasmas generated in different configurations and operating at atmospheric pressure. This discussion is based on results from numerical models and simulations of Dielectric Barrier Discharges to Micro-Hollow Cathode Discharges. We then focus on specific applications such as surface DBDs for flow control. These discharges (which have some similarities with the surface micro-discharges used in Plasma Display Panels) are being studied for their ability to modify the properties of the boundary layer along airfoils and hence to control the transition between laminar and turbulent regimes. We will show how

Electronic and optical device applications of hollow cathode plasma assisted atomic layer deposition based GaN thin films

International Nuclear Information System (INIS)

Bolat, Sami; Tekcan, Burak; Ozgit-Akgun, Cagla; Biyikli, Necmi; Okyay, Ali Kemal

2015-01-01

Electronic and optoelectronic devices, namely, thin film transistors (TFTs) and metal–semiconductor–metal (MSM) photodetectors, based on GaN films grown by hollow cathode plasma-assisted atomic layer deposition (PA-ALD) are demonstrated. Resistivity of GaN thin films and metal-GaN contact resistance are investigated as a function of annealing temperature. Effect of the plasma gas and postmetallization annealing on the performances of the TFTs as well as the effect of the annealing on the performance of MSM photodetectors are studied. Dark current to voltage and responsivity behavior of MSM devices are investigated as well. TFTs with the N 2 /H 2 PA-ALD based GaN channels are observed to have improved stability and transfer characteristics with respect to NH 3 PA-ALD based transistors. Dark current of the MSM photodetectors is suppressed strongly after high-temperature annealing in N 2 :H 2 ambient

Generation of uniform low-temperature plasma in a pulsed non-self-sustained glow discharge with a large-area hollow cathode

Energy Technology Data Exchange (ETDEWEB)

Akhmadeev, Yu. H.; Denisov, V. V., E-mail: volodyadenisov@yandex.ru; Koval, N. N.; Kovalsky, S. S.; Lopatin, I. V.; Schanin, P. M.; Yakovlev, V. V. [Russian Academy of Sciences, Institute of High-Current Electronics, Siberian Branch (Russian Federation)

2017-01-15

Generation of plasma in a pulsed non-self-sustained glow discharge with a hollow cathode with an area of ≥2 m{sup 2} at gas pressures of 0.4–1 Pa was studied experimentally. At an auxiliary arc-discharge current of 100 A and a main discharge voltage of 240 V, a pulse-periodic glow discharge with a current amplitude of 370 A, pulse duration of 340 μs, and repetition rate of 1 kHz was obtained. The possibility of creating a uniform gas-discharge plasma with a density of up to 10{sup 12} cm{sup −3} and an electron temperature of 1 eV in a volume of >0.2 m{sup 3} was demonstrated. Such plasma can be efficiently used to treat material surfaces and generate pulsed ion beams with a current density of up to 15 mA/cm{sup 2}.

Extraction of a long-pulsed intense electron beam from a pulsed plasma based on hollow cathode discharge

International Nuclear Information System (INIS)

Uramoto, Johshin.

1977-05-01

An intense electron beam (up to 1.0 kV, 0.8 kA in 0.8 cm phi) is extracted along a uniform magnetic field with a long decay time (up to 2 msec) from a pulsed high density plasma source which is produced with a fast rise time (< 100 μsec) by a secondary discharge based on a dc hollow cathode discharge. Through a back stream of ionized ions from a beam-extracting anode region where a neutral gas is fed, a space charge limit of the electron beam is so reduced that the beam current is determined by an initially injected electron flux and concentrated in a central aperture of the extracting anode. Moreover, the beam pulse width is much extended by the neutral gas feed into the anode space. (auth.)

Study of electron current extraction from a radio frequency plasma cathode designed as a neutralizer for ion source applications

Energy Technology Data Exchange (ETDEWEB)

Jahanbakhsh, Sina, E-mail: sinajahanbakhsh@gmail.com; Satir, Mert; Celik, Murat [Department of Mechanical Engineering, Bogazici University, Istanbul 34342 (Turkey)

2016-02-15

Plasma cathodes are insert free devices that are developed to be employed as electron sources in electric propulsion and ion source applications as practical alternatives to more commonly used hollow cathodes. Inductively coupled plasma cathodes, or Radio Frequency (RF) plasma cathodes, are introduced in recent years. Because of its compact geometry, and simple and efficient plasma generation, RF plasma source is considered to be suitable for plasma cathode applications. In this study, numerous RF plasma cathodes have been designed and manufactured. Experimental measurements have been conducted to study the effects of geometric and operational parameters. Experimental results of this study show that the plasma generation and electron extraction characteristics of the RF plasma cathode device strongly depend on the geometric parameters such as chamber diameter, chamber length, orifice diameter, orifice length, as well as the operational parameters such as RF power and gas mass flow rate.

Microstructure and corrosion resistance of nitrogen-rich surface layers on AISI 304 stainless steel by rapid nitriding in a hollow cathode discharge

Science.gov (United States)

Li, Yang; He, Yongyong; Zhang, Shangzhou; Wang, Wei; Zhu, Yijie

2018-01-01

Nitriding treatments have been successfully applied to austenitic stainless steels to improve their hardness and tribological properties. However, at temperatures above 450 °C, conventional plasma nitriding processes decrease the corrosion resistance due to the formation of CrN phases within the modified layer. In this work, AISI 304 austenitic stainless steels were efficiently treated by rapid plasma nitriding at a high temperature of 530 °C in a hollow cathode discharge. The enhanced ionization obtained in the hollow cathode configuration provided a high current density and, consequently, a high temperature could be attained in a short time. The nitrided layers were characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The results indicated that the dual-layer structure of the nitrided layer consists of a high-N face-centered cubic structure with a free CrN precipitate outer (top) layer and a nitrogen-expanded austenite S-phase bottom layer. The rapid nitriding-assisted hollow cathode discharge technique permits the use of high temperatures, as high as 530 °C, without promoting degradation in the corrosion resistance of stainless steel.

Ultraviolet Generation by Atmospheric Micro-Hollow Cathode Discharges

National Research Council Canada - National Science Library

Cooper, J

2004-01-01

Report developed under STTR contract for topic AFO3TOl9. This report documents the program objectives, work performed, results obtained, and future plans for a program to develop micro-hollow cathode discharge (MHCD...

Ionization processes in a transient hollow cathode discharge before electric breakdown: statistical distribution

International Nuclear Information System (INIS)

Zambra, M.; Favre, M.; Moreno, J.; Wyndham, E.; Chuaqui, H.; Choi, P.

1998-01-01

The charge formation processes in a hollow cathode region (HCR) of transient hollow cathode discharge have been studied at the final phase. The statistical distribution that describe different processes of ionization have been represented by Gaussian distributions. Nevertheless, was observed a better representation of these distributions when the pressure is near a minimum value, just before breakdown

High-Current Plasma Electron Sources

International Nuclear Information System (INIS)

Gushenets, J.Z.; Krokhmal, V.A.; Krasik, Ya. E.; Felsteiner, J.; Gushenets, V.

2002-01-01

In this report we present the design, electrical schemes and preliminary results of a test of 4 different electron plasma cathodes operating under Kg h-voltage pulses in a vacuum diode. The first plasma cathode consists of 6 azimuthally symmetrically distributed arc guns and a hollow anode having an output window covered by a metal grid. Plasma formation is initiated by a surface discharge over a ceramic washer placed between a W-made cathode and an intermediate electrode. Further plasma expansion leads to a redistribution of the discharge between the W-cathode and the hollow anode. An accelerating pulse applied between the output anode grid and the collector extracts electrons from this plasma. The operation of another plasma cathode design is based on Penning discharge for preliminary plasma formation. The main glow discharge occurs between an intermediate electrode of the Penning gun and the hollow anode. To keep the background pressure in the accelerating gap at P S 2.5x10 4 Torr either differential pumping or a pulsed gas puff valve were used. The operation of the latter electron plasma source is based on a hollow cathode discharge. To achieve a sharp pressure gradient between the cathode cavity and the accelerating gap a pulsed gas puff valve was used. A specially designed ferroelectric plasma cathode initiated plasma formation inside the hollow cathode. This type of the hollow cathode discharge ignition allowed to achieve a discharge current of 1.2 kA at a background pressure of 2x10 4 Torr. All these cathodes were developed and initially tested inside a planar diode with a background pressure S 2x10 4 Torr under the same conditions: accelerating voltage 180 - 300 kV, pulse duration 200 - 400 ns, electron beam current - 1 - 1.5 kA, and cross-sectional area of the extracted electron beam 113 cm 2

Sputter deposition of BSCCO films from a hollow cathode

International Nuclear Information System (INIS)

Lanagan, M.T.; Kampwirth, R.T.; Doyle, K.; Kowalski, S.; Miller, D.; Gray, K.E.

1991-01-01

High-T c superconducting thin films were deposited onto MgO single crystal substrates from a hollow cathode onto ceramic targets with the nominal composition of Bi 2 Sr 2 CaCu 2 O x . Films similar in composition to those used for the targets were deposited on MgO substrates by rf sputtering. The effects of sputtering time, rf power, and post-annealing on film microstructure and properties were studied in detail. Substrate temperature was found to have a significant influence on the film characteristics. Initial results show that deposition rates from a hollow cathode are an order of magnitude higher than those of a planar magnetron source at equivalent power levels. Large deposition rates allow for the coating of long lengths of wire

Production of a large area diffuse arc plasma with multiple cathode

International Nuclear Information System (INIS)

Wang Cheng; Cui Hai-Chao; Li Wan-Wan; Liao Meng-Ran; Xia Wei-Dong; Xia Wei-Luo

2017-01-01

An arc channel at atmospheric pressure tends to shrink generally. In this paper, a non-transferred DC arc plasma device with multiple cathode is introduced to produce a large area arc plasma at atmospheric pressure. This device is comprised of a 42-mm diameter tubular chamber, multiple cathode which is radially inserted into the chamber, and a tungsten anode with a nozzle in its center. In argon/helium atmosphere, a large area and circumferential homogenous diffuse arc plasma, which fills the entire cross section surrounded by the cathode tips, is observed. Results show that the uniformity and stability of diffuse arc plasma are strongly related to the plasma forming gas. Based on these experimental results, an explanation to the arc diffusion is suggested. Moreover, the electron excitation temperature and electron density measured in diffuse helium plasma are much lower than those of constricted arc column, which indicates the diffuse helium plasma probably deviates from the local thermodynamic equilibrium state. Unlike the common non-transferred arc plasma devices, this device can provide a condition for axial-fed feedstock particles. The plasma device is attempted to spheroidize alumina powders by using the central axis to send the powder. Results show that the powder produced is usually a typical hollow sphere. (paper)

Note: Possibilities of detecting the trace-level erosion products from an electric propulsion hollow cathode plasma source by the method of time-of-flight mass spectrometry

Science.gov (United States)

Ning, Zhong-Xi; Zhang, Hai-Guang; Zhu, Xi-Ming; Jiang, Bin-Hao; Zhou, Zhong-Yue; Yu, Da-Ren; An, Bing-Jian; Wang, Yan-Fei

2018-02-01

A hollow cathode produces electrons which neutralize ions from electric propulsion thrusters. After hundreds to thousands of hours of operation in space, the cathode materials can be significantly eroded due to ion bombardment. As a result, the electric propulsion system performance will be obviously changed or even fail. In this work, the erosion products from a LaB6 hollow cathode (widely used presently in electric propulsion systems) are studied by using a specific detection system, which consists of a molecular beam sampler and a time-of-flight mass spectrometer. This system measures trace-level-concentration (10-6-10-3) products. Boron (B), tantalum (Ta), and tungsten (W)—originating from the emitter, keeper, and orifice of the hollow cathode—are measured. It is found that the erosion rate is significantly influenced by the gas flow rate to the cathode.

Electric field measurements in a hollow cathode discharge by two-photon polarization spectroscopy of atomic deuterium

International Nuclear Information System (INIS)

Rosa, M I de la; Perez, C; Gruetzmacher, K; Gonzalo, A B; Steiger, A

2006-01-01

The local electric field strength (E-field) is an important parameter to be known in low pressure plasmas such as glow discharges, RF and microwave discharges, plasma boundaries in tokamaks etc. In this paper, we demonstrate, for the first time, the potential of two-photon polarization spectroscopy measuring the E-field in the cathode fall region of a hollow cathode discharge, via Doppler-free spectra of the Stark splitting of the 2S level of atomic deuterium. Electric field strength is determined in the range from 2 to 5 kV cm -1 . Compared with LIF, this method has several advantages: it is not affected by background radiation, it can be applied without limitation at elevated pressure and it allows simultaneous measurement of absolute local atomic ground state densities of hydrogen isotopes

Synthesis of diamond-like carbon via PECD using a streaming neutral gas injection hollow cathode

International Nuclear Information System (INIS)

Pacho, A.; Pares, E.; Ramos, H.; Mendenilla, A.; Malapit, G.

2009-01-01

A streaming neutral gas injection hollow cathode system was used to deposit diamond-like carbon films via plasma enhanced chemical vapor deposition on silicon and nickel-coated silicon substrates with acetylene and hydrogen as reactant gases. Samples were characterized using SEM and Raman spectroscopy. The work presented here aims to demonstrate the capability of the system to synthesize carbonaceous films and is starting point towards work on formation of carbon nanostructures. (author)

Hollow core plasma channel generation

International Nuclear Information System (INIS)

Quast, Heinrich Martin

2018-03-01

The use of a hollow plasma channel in plasma-based acceleration has beneficial properties for the acceleration of electron and positron bunches. In the scope of the FLASHForward facility at DESY, the generation of such a plasma structure is examined. Therefore, the generation of a ring-shaped laser intensity profile with different techniques is analyzed. From the obtained intensity profiles the electron density of a hollow plasma channel is simulated in the focal region. Different parameters are scanned to understand their influence on the electron density distribution - an important parameter being, for example, the radius of the central region of the channel. In addition to the simulations, experiments are presented, during which a laser pulse is transformed into a hollow beam with a spiral phase plate. Subsequently, it forms a plasma during the interaction with hydrogen, where the plasma is imaged with interferometry. For energies above 0.9 mJ a hollow plasma structure can be observed at the location of first plasma formation.

A multiple gap plasma cathode electron gun and its electron beam analysis in self and trigger breakdown modes

International Nuclear Information System (INIS)

Kumar, Niraj; Pal, Udit Narayan; Prakash, Ram; Pal, Dharmendra Kumar; Jadon, Arvind Singh; Rahaman, Hasibur

2016-01-01

In the present paper, a pseudospark discharge based multiple gap plasma cathode electron gun is reported which has been operated separately in self and trigger breakdown modes using two different gases, namely, argon and hydrogen. The beam current and beam energy have been analyzed using a concentric ring diagnostic arrangement. Two distinct electron beams are clearly seen with hollow cathode and conductive phases. The hollow cathode phase has been observed for ∼50 ns where the obtained electron beam is having low beam current density and high energy. While in conductive phase it is high current density and low energy electron beam. It is inferred that in the hollow cathode phase the beam energy is more for the self breakdown case whereas the current density is more for the trigger breakdown case. The tailor made operation of the hollow cathode phase electron beam can play an important role in microwave generation. Up to 30% variation in the electron beam energy has been achieved keeping the same gas and by varying the breakdown mode operations. Also, up to 32% variation in the beam current density has been achieved for the trigger breakdown mode at optimized trigger position by varying the gas type.

A multiple gap plasma cathode electron gun and its electron beam analysis in self and trigger breakdown modes.

Science.gov (United States)

Kumar, Niraj; Pal, Dharmendra Kumar; Jadon, Arvind Singh; Pal, Udit Narayan; Rahaman, Hasibur; Prakash, Ram

2016-03-01

In the present paper, a pseudospark discharge based multiple gap plasma cathode electron gun is reported which has been operated separately in self and trigger breakdown modes using two different gases, namely, argon and hydrogen. The beam current and beam energy have been analyzed using a concentric ring diagnostic arrangement. Two distinct electron beams are clearly seen with hollow cathode and conductive phases. The hollow cathode phase has been observed for ∼50 ns where the obtained electron beam is having low beam current density and high energy. While in conductive phase it is high current density and low energy electron beam. It is inferred that in the hollow cathode phase the beam energy is more for the self breakdown case whereas the current density is more for the trigger breakdown case. The tailor made operation of the hollow cathode phase electron beam can play an important role in microwave generation. Up to 30% variation in the electron beam energy has been achieved keeping the same gas and by varying the breakdown mode operations. Also, up to 32% variation in the beam current density has been achieved for the trigger breakdown mode at optimized trigger position by varying the gas type.

A multiple gap plasma cathode electron gun and its electron beam analysis in self and trigger breakdown modes

Energy Technology Data Exchange (ETDEWEB)

Kumar, Niraj; Pal, Udit Narayan; Prakash, Ram [CSIR-Central Electronics Engineering Research Institute (CSIR-CEERI), Pilani, Rajasthan 333031 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-CEERI Campus, Pilani (India); Pal, Dharmendra Kumar; Jadon, Arvind Singh; Rahaman, Hasibur [CSIR-Central Electronics Engineering Research Institute (CSIR-CEERI), Pilani, Rajasthan 333031 (India)

2016-03-15

In the present paper, a pseudospark discharge based multiple gap plasma cathode electron gun is reported which has been operated separately in self and trigger breakdown modes using two different gases, namely, argon and hydrogen. The beam current and beam energy have been analyzed using a concentric ring diagnostic arrangement. Two distinct electron beams are clearly seen with hollow cathode and conductive phases. The hollow cathode phase has been observed for ∼50 ns where the obtained electron beam is having low beam current density and high energy. While in conductive phase it is high current density and low energy electron beam. It is inferred that in the hollow cathode phase the beam energy is more for the self breakdown case whereas the current density is more for the trigger breakdown case. The tailor made operation of the hollow cathode phase electron beam can play an important role in microwave generation. Up to 30% variation in the electron beam energy has been achieved keeping the same gas and by varying the breakdown mode operations. Also, up to 32% variation in the beam current density has been achieved for the trigger breakdown mode at optimized trigger position by varying the gas type.

Development of Hollow Cathode of High Power Middle Pressure Arcjet

National Research Council Canada - National Science Library

Vaulin, Eujeni

1995-01-01

...: Determine integral performances of arcjet devices in nitrogen, ammonia, and their mixtures using hollow cathode devices at low and high current levels, perform short term tests (up to 50 hours...

The design and characteristics of direct current glow discharge atomic emission source operated with plain and hollow cathodes

International Nuclear Information System (INIS)

Qayyum, A.; Mahmood, M.I.

2008-01-01

A compact direct current glow discharge atomic emission source has been designed and constructed for analytical applications. This atomic emission source works very efficiently at a low-input electrical power. The design has some features that make it distinct from that of the conventional Grimm glow discharge source. The peculiar cathode design offered greater flexibility on size and shape of the sample. As a result the source can be easily adopted to operate in Plain or Hollow Cathode configuration. I-V and spectroscopic characteristics of the source were compared while operating it with plain and hollow copper cathodes. It was observed that with hollow cathode, the source can be operated at a less input power and generates greater Cu I and Cu II line intensities. Also, the intensity of Cu II line rise faster than Cu I line with argon pressure for both cathodes. But the influence of pressure on Cu II lines was more significant when the source is operated with hollow cathode

Modulation Transfer Spectroscopy of Ytterbium Atoms in a Hollow Cathode Lamp

International Nuclear Information System (INIS)

Wang Wen-Li; Xu Xin-Ye

2011-01-01

We present the experimental study of modulation transfer spectroscopy of ytterbium atoms in a hollow cathode lamp. The dependences of its linewidth, slope and magnitude on the various experimental parameters are measured and fitted by the well-known theoretical expressions. The experimental results are in good agreement with the theoretical prediction. We have observed the Dicke narrowing effect by increasing the current of the hollow cathode lamp. It is also found that there are the optimal current and laser power to generate the better modulation transfer spectroscopy signal, which can be employed for locking the laser frequency to the atomic transition. (atomic and molecular physics)

Measurements on the source properties of a hollow cathode

NARCIS (Netherlands)

Vogels, J.M.M.J.; Konings, L.U.E.; Koelman, J.M.V.A.; Schram, D.C.; Bötticher, W.; Wenk, H.; Schulz-Gulde, E.

1983-01-01

The ion production rate of a hollow cathode in a magnetized arc has been measured. At low magnetic fields supersonic ion drifts have been observed. The ionized fraction of the gas flow decreases with increasing flow and the ion flux saturates at high flow rates

Reduction of gas flow into a hollow cathode ion source for a neutral beam injector

International Nuclear Information System (INIS)

Tanaka, S.; Akiba, M.; Arakawa, Y.; Horiike, H.; Sakuraba, J.

1982-01-01

Experimental studies have been made on the reduction of the gas flow rate into ion sources which utilize a hollow cathode. The electron emitter of the hollow cathode was a barium oxide impregnated porous tungsten tube. The hollow cathode was mounted to a circular or a rectangular bucket source and the following results were obtained. There was a tendency for the minimum gas flow rate for the stable source operation to decrease with increasing orifice diameter of the hollow cathode up to 10 mm. A molybdenum button with an appropriate diameter set in front of the orifice reduced the minimum gas flow rate to one half of that without button. An external magnetic field applied antiparallel to the field generated by the heater current stabilized the discharges and reduced the minimum gas flow rate to one half of that without field. Combination of the button and the antiparallel field reduced the minimum gas flow rate from the initial value (9.5 Torr 1/s) to 2.4 Torr 1/s. The reason for these effects was discussed on the basis of the theory for arc starvation

[Atomic/ionic fluorescence in microwave plasma torch discharge excited by high current microsecond pulsed hollow cathode lamp-europium atomic/ionic fluorescence spectrometry].

Science.gov (United States)

Gong, Z; Liang, F; Yang, P; Jin, Q; Huang, B

1999-06-01

Eu atomic and ionic fluorescence spectrometry in microwave plasma torch discharge excited by high current microsecond pulsed hollow cathode lamp (HCMP HCL-MPT AFS/IFS) was studied. Operating conditions were optimized. The best detection limits for AFS and IFS obtained with a desolvated ultrasonic nebulization system were 42.0 ng/mL for Eu I 462.7 nm and 21.8 ng/mL for Eu II 381.97 nm, respectively, both were better than those given by the instruction manual of a Baird ICP AFS-2000 spectrometer using pneumatic concentric nebulizer with desolvation for AFS, but were significantly higher than those obtained by using the Baird spectrometer with a mini-monochromator and a ultrasonic nebulzer system.

Spectra of Th/Ar and U/Ne hollow cathode lamps for spectrograph calibration

Science.gov (United States)

Nave, Gillian; Shlosberg, Ariel; Kerber, Florian; Den Hartog, Elizabeth; Neureiter, Bianca

2018-01-01

Low-current Th/Ar hollow cathode lamps have long been used for calibration of astronomical spectrographs on ground-based telescopes. Thorium is an attractive element for calibration as it has a single isotope, has narrow spectral lines, and has a dense spectrum covering the whole of the visible region. However, the high density of the spectrum that makes it attractive for calibrating high-resolution spectrographs is a detriment for lower resolution spectrographs and this is not obvious by examination of existing linelists. In addition, recent changes in regulations regarding the handling of thorium have led to a degradation in the quality of Th/Ar calibration lamps, with contamination by molecular ThO lines that are strong enough to obscure the calibration lines of interest.We are pursuing two approaches to these problems. First, we have expanded and improved the NIST Standard Reference Database 161, "Spectrum of Th-Ar Hollow Cathode Lamps" to cover the region 272 nm to 5500 nm. Spectra of hollow cathode lamps at up to 3 different currents can now be displayed simultaneously. Interactive zooming and the ability to convolve any of the spectra with a Gaussian or uploaded instrument profile enable the user to see immediately what the spectrum would look like at the particular resolution of their spectrograph. Second, we have measured the spectrum of a recent, contaminated Th/Ar hollow cathode lamp using a high-resolution Echelle spectrograph (Madison Wisconsin) at a resolving power (R~ 250,000). This significantly exceeds the resolving power of most astronomical spectrographs and resolves many of the molecular lines of ThO. With these spectra we are measuring and calibrating the positions of these molecular lines in order to make them suitable for spectrograph calibration.In the near infrared region, U/Ne hollow cathode lamps give a higher density of calibration lines than Th/Ar lamps and will be implemented on the upgraded CRIRES+ spectrograph on ESO’s Very Large

[Atomic/ionic fluorescence in microwave plasma torch discharge with excitation of high current and microsecond pulsed hollow cathode lamp: Ca atomic/ionic fluorescence spectrometry].

Science.gov (United States)

Gong, Zhen-bin; Liang, Feng; Yang, Peng-yuan; Jin, Qin-han; Huang, Ben-li

2002-02-01

A system of atomic and ionic fluorescence spectrometry in microwave plasma torch (MPT) discharge excited by high current microsecond pulsed hollow cathode lamp (HCMP HCL) has been developed. The operation conditions for Ca atomic and ionic fluorescence spectrometry have been optimized. Compared with atomic fluorescence spectrometry (AFS) in argon microwave induced plasma (MIP) and MPT with the excitation of direct current and conventional pulsed HCL, the system with HCMP HCL excitation can improve AFS and ionic fluorescence spectrometry (IFS) detection limits in MPT atomizer and ionizer. Detection limits (3 sigma) with HCMP HCL-MPT-AFS/IFS are 10.1 ng.mL-1 for Ca I 422.7 nm, 14.6 ng.mL-1 for Ca II 393.4 nm, and 37.4 ng.mL-1 for Ca II 396.8 nm, respectively.

Spatio-temporal characteristics of self-pulse in hollow cathode discharge

International Nuclear Information System (INIS)

Jing, Ha; He, Shoujie

2015-01-01

The characteristics of self-pulse in hollow cathode discharge at low pressure have been investigated. The voltage-current (V-I) curves, the influence of ballast resistor on the self-pulses, and the evolution of current and voltage are measured. Both the axial and radial spatio-temporal discharge images of self-pulse are recorded. The results show that there exists the hysteresis effect in the present hollow cathode discharge. The high value of ballast resistors is favourable for the observation of self-pulses. The process of the self-pulse can be divided into three stages from the temporal discharge images, i.e., the pre-discharge, the transition from mainly axial electric field to mainly radial electric field, and the decaying process. The self-pulse is suggested to originate from the mode transition of the discharge in essence

Auxiliary glow discharge in the trigger unit of a hollow-cathode thyratron

Energy Technology Data Exchange (ETDEWEB)

Korolev, Yu. D.; Landl, N. V., E-mail: landl@lnp.hcei.tsc.ru; Geyman, V. G.; Frants, O. B.; Shemyakin, I. A.; Nekhoroshev, V. O. [Russian Academy of Sciences, Institute of High-Current Electronics, Siberian Branch (Russian Federation)

2016-08-15

Results from studies of a low-current glow discharge with a hollow cathode are presented. A specific feature of the discharge conditions was that a highly emissive tablet containing cesium carbonate was placed in the cathode cavity. In the absence of a tablet, the discharge ignition voltage was typically ≥3.5 kV, while the burning voltage was in the range of 500–600 V. The use of the tablet made it possible to decrease the ignition voltage to 280 V and maintain the discharge burning voltage at a level of about 130 V. A model of the current sustainment in a hollow-cathode discharge is proposed. Instead of the conventional secondary emission yield, the model uses a generalized emission yield that takes into account not only ion bombardment of the cathode, but also the emission current from an external source. The model is used to interpret the observed current−voltage characteristics. The results of calculations agree well with the experimental data. It is shown that, in some discharge modes, the external emission current from the cathode can reach 25% of the total discharge current.

A flexible platform for simulations of sputtering hollow cathode discharges for laser applications

NARCIS (Netherlands)

Mihailova, D.B.; Grozeva, M.; Hagelaar, G.J.M.; Dijk, van J.; Brok, W.J.M.; Mullen, van der J.J.A.M.

2008-01-01

The Plasimo modelling platform, extended with a cathode wall sputtering module is used to study the discharge processes and to optimise the design parameters of a sputtering hollow cathode discharge (HCD). We present Plasimo simulations of a HCD used for laser applications. A time dependent

Photoluminescence from PP-HMDSO thin films deposited using a remote plasma of 13.56 MHz hollow cathode discharge

International Nuclear Information System (INIS)

Naddaf, M; Saloum, S; Hamadeh, H

2007-01-01

Room temperature photoluminescence (PL) from plasma-polymerized hexamethyldisiloxane (PP-HMDSO) thin films deposited on silicon wafers has been investigated as a function of both the applied RF power and the monomer flow rate. Films were deposited in a low pressure-low temperature remote plasma ignited in a 13.56 MHz hollow cathode discharge reactor, using pure HMDSO as a monomer and Ar as a feed gas. The substrate temperature during the deposition was as low as 40 deg. C and the total pressure was about 0.03 mbar. Optical emission spectroscopy (OES) has been used as in situ tool for monitoring the different chemical species present in the plasma during deposition processes. The deposited PP-HMDSO films showed a strong, broad 'green/yellow' PL band. The RF power and the flow rate of the HMDSO monomer are found to have a significant impact on the PL intensity of the deposited film. The changes in the chemical bonding of the film as a function of deposition parameters have been investigated by using the Fourier transform infrared (FTIR) spectroscopic analysis and are related to PL and OES results. The 'green/yellow' PL band is ascribed to chemical groups and bonds of silicon, hydrogen and/or oxygen constituting the films, in particular, SiH, SiO bonds and silanol Si-O-H groups

Photoluminescence from PP-HMDSO thin films deposited using a remote plasma of 13.56 MHz hollow cathode discharge

Science.gov (United States)

Naddaf, M.; Saloum, S.; Hamadeh, H.

2007-07-01

Room temperature photoluminescence (PL) from plasma-polymerized hexamethyldisiloxane (PP-HMDSO) thin films deposited on silicon wafers has been investigated as a function of both the applied RF power and the monomer flow rate. Films were deposited in a low pressure-low temperature remote plasma ignited in a 13.56 MHz hollow cathode discharge reactor, using pure HMDSO as a monomer and Ar as a feed gas. The substrate temperature during the deposition was as low as 40 °C and the total pressure was about 0.03 mbar. Optical emission spectroscopy (OES) has been used as in situ tool for monitoring the different chemical species present in the plasma during deposition processes. The deposited PP-HMDSO films showed a strong, broad 'green/yellow' PL band. The RF power and the flow rate of the HMDSO monomer are found to have a significant impact on the PL intensity of the deposited film. The changes in the chemical bonding of the film as a function of deposition parameters have been investigated by using the Fourier transform infrared (FTIR) spectroscopic analysis and are related to PL and OES results. The 'green/yellow' PL band is ascribed to chemical groups and bonds of silicon, hydrogen and/or oxygen constituting the films, in particular, SiH, SiO bonds and silanol Si-O-H groups.

Photoluminescence from PP-HMDSO thin films deposited using a remote plasma of 13.56 MHz hollow cathode discharge

Energy Technology Data Exchange (ETDEWEB)

Naddaf, M; Saloum, S; Hamadeh, H [Department of Physics, Atomic Energy Commission of Syria (AECS), PO Box 6091, Damascus (Syrian Arab Republic)

2007-07-07

Room temperature photoluminescence (PL) from plasma-polymerized hexamethyldisiloxane (PP-HMDSO) thin films deposited on silicon wafers has been investigated as a function of both the applied RF power and the monomer flow rate. Films were deposited in a low pressure-low temperature remote plasma ignited in a 13.56 MHz hollow cathode discharge reactor, using pure HMDSO as a monomer and Ar as a feed gas. The substrate temperature during the deposition was as low as 40 deg. C and the total pressure was about 0.03 mbar. Optical emission spectroscopy (OES) has been used as in situ tool for monitoring the different chemical species present in the plasma during deposition processes. The deposited PP-HMDSO films showed a strong, broad 'green/yellow' PL band. The RF power and the flow rate of the HMDSO monomer are found to have a significant impact on the PL intensity of the deposited film. The changes in the chemical bonding of the film as a function of deposition parameters have been investigated by using the Fourier transform infrared (FTIR) spectroscopic analysis and are related to PL and OES results. The 'green/yellow' PL band is ascribed to chemical groups and bonds of silicon, hydrogen and/or oxygen constituting the films, in particular, SiH, SiO bonds and silanol Si-O-H groups.

Photoluminescence from PP-HMDSO thin films deposited using a remote plasma of 13.56 MHz hollow cathode discharge

International Nuclear Information System (INIS)

Naddaf, M.; Saloum, S.; Hamadeh, H.

2008-01-01

Room temperature photoluminescence (PL) from plasma-polymerized hexamethyldisiloxane (PP-HMDSO) thin films deposited on silicon wafers has been investigated as a function of both the applied RF power and the monomer flow rate. Films were deposited in a low pressure-low temperature remote plasma ignited in a 13.56 MHz hollow cathode discharge reactor, using pure HMDSO as a monomer and Ar as a feed gas. The substrate temperature during the deposition was as low as 40 deg. C and the total pressure was about 0.03 mbar. Optical emission spectroscopy (OES) has been used as in situ tool for monitoring the different chemical species present in the plasma during deposition processes. The deposited PP-HMDSO films showed a strong, broad 'green/yellow' PL band. The RF power and the flow rate of the HMDSO monomer are found to have a significant impact on the PL intensity of the deposited film. The changes in the chemical bonding of the film as a function of deposition parameters have been investigated by using the Fourier transform infrared (FTIR) spectroscopic analysis and are related to PL and OES results. The 'green/yellow' PL band is ascribed to chemical groups and bonds of silicon, hydrogen and/or oxygen constituting the films, in particular, SiH, SiO bonds and silanol Si-O-H groups. (Authors)

Determination of electric field strength and kinetic temperature in the cathode fall region of a hollow cathode discharge

Energy Technology Data Exchange (ETDEWEB)

De la Rosa, M I; Perez, C; Gruetzmacher, K [Universidad de Valladolid, Facultad de Ciencias, 47071 Valladolid (Spain); Gonzalo, A B; Del Val, J A, E-mail: delarosa@opt.uva.e [Universidad de Salamanca, Escuela Politecnica Superior, 05003 Avila (Spain)

2010-05-01

In this work, we demonstrate the high potential of two-photon excitation of the 1S -2S transition of atomic hydrogen followed by optogalvanic detection, for measuring under identical experimental conditions, the kinetic temperature and the electric field strength in the cathode sheath region of a hollow cathode discharge. The first obtained results for both parameters are discussed in this paper.

Ionization Waves in a Fast, Hollow-Cathode-Assisted Capillary Discharge

International Nuclear Information System (INIS)

Rutkevich, I.; Mond, M.; Kaufman, Y.; Choi, P.; Favre, M.

1999-01-01

The initial, low-current stage of the evolution of a soft x-ray emitting, hollow-cathode-assisted capillary discharge initiated by a steep high-voltage pulse is investigated. The capillary is surrounded by a shield having the cathode potential. The mean electric field E of the order of 10 kV/cm and the low gas pressure (P<1Torr) provide conditions for extensive electron runaway. This is taken into account in the formulation of the theoretical approach by retaining the inertial terms in the momentum equation for the electrons. In addition, the ionization rate is calculated by considering the cross section for ionization by high-energy electrons. The two-dimensional system of the basic equations is reduced to a system of one-dimensional equations for the axial distributions of the physical quantities by introducing appropriate radial profiles of the electric potential, and the electron gas parameters and satisfying the electrodynamic boundary conditions at the capillary wall and at the shield. The resulting system of equations admits solutions in the form of stationary ionization waves transferring the anode potential to the cathode end. Numerical calculations of such solutions for argon show that the wave velocity V increases with the gas pressure P and with the density of initial electron beam ejected from the cathode hole ahead of the ionization front, while the dependence of V on the applied voltage is weak. At the instant when the virtual anode reaches the cathode hole, the plasma in the capillary is not yet fully ionized. The traverse time of the ionization wave along the capillary calculated for various gas pressures is in reasonable agreement with experimentally registered time delay for a high-current stage resulting in voltage collapse and soft x-ray emission

Facile Synthesis of V2O5 Hollow Spheres as Advanced Cathodes for High-Performance Lithium-Ion Batteries

Directory of Open Access Journals (Sweden)

Xingyuan Zhang

2017-01-01

Full Text Available Three-dimensional V2O5 hollow structures have been prepared through a simple synthesis strategy combining solvothermal treatment and a subsequent thermal annealing. The V2O5 materials are composed of microspheres 2–3 μm in diameter and with a distinct hollow interior. The as-synthesized V2O5 hollow microspheres, when evaluated as a cathode material for lithium-ion batteries, can deliver a specific capacity as high as 273 mAh·g−1 at 0.2 C. Benefiting from the hollow structures that afford fast electrolyte transport and volume accommodation, the V2O5 cathode also exhibits a superior rate capability and excellent cycling stability. The good Li-ion storage performance demonstrates the great potential of this unique V2O5 hollow material as a high-performance cathode for lithium-ion batteries.

Integration issues of a plasma contactor Power Electronics Unit

Science.gov (United States)

Pinero, Luis R.; York, Kenneth W.; Bowers, Glen E.

1995-01-01

A hollow cathode-based plasma contactor is baselined on International Space Station Alpha (ISSA) for spacecraft charge control. The plasma contactor system consists of a hollow cathode assembly (HCA), a power electronics unit (PEU), and an expellant management unit (EMU). The plasma contactor has recently been required to operate in a cyclic mode to conserve xenon expellant and extend system life. Originally, a DC cathode heater converter was baselined for a continuous operation mode because only a few ignitions of the hollow cathode were expected. However, for cyclic operation, a DC heater supply can potentially result in hollow cathode heater component failure due to the DC electrostatic field. This can prevent the heater from attaining the proper cathode tip temperature for reliable ignition of the hollow cathode. To mitigate this problem, an AC cathode heater supply was therefore designed, fabricated, and installed into a modified PEU. The PEU was tested using resistive loads and then integrated with an engineering model hollow cathode to demonstrate stable steady-state operation. Integration issues such as the effect of line and load impedance on the output of the AC cathode heater supply and the characterization of the temperature profile of the heater under AC excitation were investigated.

Hollow Carbon Nanofiber-Encapsulated Sulfur Cathodes for High Specific Capacity Rechargeable Lithium Batteries

KAUST Repository

Zheng, Guangyuan

2011-10-12

Sulfur has a high specific capacity of 1673 mAh/g as lithium battery cathodes, but its rapid capacity fading due to polysulfides dissolution presents a significant challenge for practical applications. Here we report a hollow carbon nanofiber-encapsulated sulfur cathode for effective trapping of polysulfides and demonstrate experimentally high specific capacity and excellent electrochemical cycling of the cells. The hollow carbon nanofiber arrays were fabricated using anodic aluminum oxide (AAO) templates, through thermal carbonization of polystyrene. The AAO template also facilitates sulfur infusion into the hollow fibers and prevents sulfur from coating onto the exterior carbon wall. The high aspect ratio of the carbon nanofibers provides an ideal structure for trapping polysulfides, and the thin carbon wall allows rapid transport of lithium ions. The small dimension of these nanofibers provides a large surface area per unit mass for Li2S deposition during cycling and reduces pulverization of electrode materials due to volumetric expansion. A high specific capacity of about 730 mAh/g was observed at C/5 rate after 150 cycles of charge/discharge. The introduction of LiNO3 additive to the electrolyte was shown to improve the Coulombic efficiency to over 99% at C/5. The results show that the hollow carbon nanofiber-encapsulated sulfur structure could be a promising cathode design for rechargeable Li/S batteries with high specific energy. © 2011 American Chemical Society.

Self-induced optogalvanic effect in a segmented hollow-cathode discharge

Science.gov (United States)

Steflekova, V.; Zhechev, D.

2018-03-01

Optogalvanic (OG) interaction is simulated and studied in a segmented hollow-cathode discharge (SHCD). HCD-lamps are used to induce an OG signal by their own emission or by that of another lamp. The efficiency of the OG of a Ne/Cu HCD lamp in the range 320-380 nm is estimated theoretically. An irregular galvanic peak arising near the inflection point in the i-V curve (∂V/∂i<0) is detected. Its origin is related to Penning ionization of the sputtered cathode material.

Investigation of chlorination of zirconium and hafnium and their compounds in discharge from hollow cathode

International Nuclear Information System (INIS)

Ioffe, R.B.; Korovin, Yu.I.

1978-01-01

The possibility is investigated of chlorinating various zirconium and hafnium compounds (metal, oxide, carbide) in a hot discharge from a hollow cathode with various chlorinating reagents: copper monochloride, nickel chloride, magnesium chloride, for the purpose of accelerating their entrance into the excitation zone. It has been shown thermodynamically and experimentally that chlorination of metal zirconium and hafnium and their carbides with copper monochloride in hot hollow cathode conditions provides a sharp increase in the intensity of the lines of these elements

A new large-scale plasma source with plasma cathode

International Nuclear Information System (INIS)

Yamauchi, K.; Hirokawa, K.; Suzuki, H.; Satake, T.

1996-01-01

A new large-scale plasma source (200 mm diameter) with a plasma cathode has been investigated. The plasma has a good spatial uniformity, operates at low electron temperature, and is highly ionized under relatively low gas pressure of about 10 -4 Torr. The plasma source consists of a plasma chamber and a plasma cathode generator. The plasma chamber has an anode which is 200 mm in diameter, 150 mm in length, is made of 304 stainless steel, and acts as a plasma expansion cup. A filament-cathode-like plasma ''plasma cathode'' is placed on the central axis of this source. To improve the plasma spatial uniformity in the plasma chamber, a disk-shaped, floating electrode is placed between the plasma chamber and the plasma cathode. The 200 mm diameter plasma is measure by using Langmuir probes. As a result, the discharge voltage is relatively low (30-120 V), the plasma space potential is almost equal to the discharge voltage and can be easily controlled, the electron temperature is several electron volts, the plasma density is about 10 10 cm -3 , and the plasma density is about 10% variance in over a 100 mm diameter. (Author)

Kinetic model of a Ne-H2 Penning Recombination Laser operating in the hollow cathode discharge

International Nuclear Information System (INIS)

Pramatarov, P.M.; Stefanova, M.S.; Petrov, G.M.

1995-01-01

The Penning Recombination Laser (PRL) requires the presence of both a recombination plasma populating the upper laser level (ULL) and a gas component efficiently depopulating the lower laser level (LLL) by Penning reactions. Such requirements are met in the negative glow plasma of a pulsed high voltage Ne-H 2 discharge with a helical hollow cathode. High rates of ionizations followed by recombinations are reached due to the beam component of non-Maxwellian electrons of 1-2 keV energy present in the tail of the electron energy distribution function. The H 2 , on the one hand plays the role of Penning component and on the other hand effectively cools the electrons by rotational and vibrational levels excitation. The latter contributes to the effectiveness of the recombination processes. A kinetic model of the physical processes determining the inversion population on the NeI(2p 1 -1s 2 ) transition (the 585.3 nm line) in a Ne-H 2 PRL operating in a high voltage hollow cathode discharge at intermediate pressures is proposed. About 60 plasma-chemical reactions are considered in the model. These include: two-electron recombination of Ne + ; dissociative recombination of Ne 2 + , NeH + and H 2 + ; ion-ion recombination of Ne + and H - ; Ne and H 2 direct ionization by fast electrons; Ne stepwise ionization; Penning ionization; Ne excitation by fast electrons; Ne stepwise excitation and de-excitation; radiative transitions; electron mixing between Ne excited states; H 2 rotational and vibrational levels excitation; H 2 dissociative attachment; elastic electron collisions with H 2 and Ne. The rate constants for the reactions are either taken from the literature or calculated in this work

Electron and ion kinetics in a micro hollow cathode discharge

Energy Technology Data Exchange (ETDEWEB)

Kim, G J; Iza, F; Lee, J K [Electronics and Electrical Engineering Department, Pohang University of Science and Technology, Pohang, 790-784 (Korea, Republic of)

2006-10-21

Electron and ion kinetics in a micro hollow cathode discharge are investigated by means of two-dimensional axisymmetric particle-in-cell Monte Carlo collision simulations. Argon discharges at 10 and 300 Torr are studied for various driving currents. Electron and ion energy probability functions (IEPF) are shown at various times and locations to study the spatio-temporal behaviour of the discharge. The electron energy probability function (EEPF) evolves from the Druyvesteyn type in the early stages of the discharge into a two (or three) temperature distribution when steady state is reached. In steady state, secondary electrons accelerated across the cathode fall populate the high energy tail of the EEPF while the low energy region is populated by trapped electrons. The IEPF evolves from a Maxwellian in the negative glow (bulk) to a two temperature distribution on the cathode surface. The overpopulation of low energy ions near the cathode surface is attributed to a larger collision cross section for low energy ions and ionization within the cathode fall.

Electron and ion kinetics in a micro hollow cathode discharge

International Nuclear Information System (INIS)

Kim, G J; Iza, F; Lee, J K

2006-01-01

Electron and ion kinetics in a micro hollow cathode discharge are investigated by means of two-dimensional axisymmetric particle-in-cell Monte Carlo collision simulations. Argon discharges at 10 and 300 Torr are studied for various driving currents. Electron and ion energy probability functions (IEPF) are shown at various times and locations to study the spatio-temporal behaviour of the discharge. The electron energy probability function (EEPF) evolves from the Druyvesteyn type in the early stages of the discharge into a two (or three) temperature distribution when steady state is reached. In steady state, secondary electrons accelerated across the cathode fall populate the high energy tail of the EEPF while the low energy region is populated by trapped electrons. The IEPF evolves from a Maxwellian in the negative glow (bulk) to a two temperature distribution on the cathode surface. The overpopulation of low energy ions near the cathode surface is attributed to a larger collision cross section for low energy ions and ionization within the cathode fall

Two-stage plasma gun based on a gas discharge with a self-heating hollow emitter.

Science.gov (United States)

Vizir, A V; Tyunkov, A V; Shandrikov, M V; Oks, E M

2010-02-01

The paper presents the results of tests of a new compact two-stage bulk gas plasma gun. The plasma gun is based on a nonself-sustained gas discharge with an electron emitter based on a discharge with a self-heating hollow cathode. The operating characteristics of the plasma gun are investigated. The discharge system makes it possible to produce uniform and stable gas plasma in the dc mode with a plasma density up to 3x10(9) cm(-3) at an operating gas pressure in the vacuum chamber of less than 2x10(-2) Pa. The device features high power efficiency, design simplicity, and compactness.

Two-stage plasma gun based on a gas discharge with a self-heating hollow emitter

International Nuclear Information System (INIS)

Vizir, A. V.; Tyunkov, A. V.; Shandrikov, M. V.; Oks, E. M.

2010-01-01

The paper presents the results of tests of a new compact two-stage bulk gas plasma gun. The plasma gun is based on a nonself-sustained gas discharge with an electron emitter based on a discharge with a self-heating hollow cathode. The operating characteristics of the plasma gun are investigated. The discharge system makes it possible to produce uniform and stable gas plasma in the dc mode with a plasma density up to 3x10 9 cm -3 at an operating gas pressure in the vacuum chamber of less than 2x10 -2 Pa. The device features high power efficiency, design simplicity, and compactness.

Ultra-Compact Center-Mounted Hollow Cathodes for Hall Effect Thrusters, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — The proposed innovation is a long lifetime, compact hollow cathode that can be mounted along the axis of a 600 W-class Hall effect thruster. Testing at kilowatt...

Geometrical features in longitudinal sputtering hollow cathode discharges for laser applications

NARCIS (Netherlands)

Mihailova, D.B.; Dijk, van J.; Hagelaar, G.J.M.; Karatodorov, S.; Zahariev, P.; Grozeva, M.; Mullen, van der J.J.A.M.

2012-01-01

Longitudinal sputtering hollow cathode discharge (HCD) used as active medium for lasing is studied by means of numerical modelling. Due to the longitudinal non-uniformities of the discharge, the laser operation could be strongly affected. The non-uniformity of the discharge is mainly influenced by

Deposition of hematite Fe.sub.2./sub.O.sub.3./sub. thin film by DC pulsed magnetron and DC pulsed hollow cathode sputtering system

Czech Academy of Sciences Publication Activity Database

Hubička, Zdeněk; Kment, Štěpán; Olejníček, Jiří; Čada, Martin; Kubart, T.; Brunclíková, Michaela; Kšírová, Petra; Adámek, Petr; Remeš, Zdeněk

2013-01-01

Roč. 549, Dec (2013), s. 184-191 ISSN 0040-6090 R&D Projects: GA ČR GAP108/12/2104; GA MŠk LH12043 Grant - others:AVČR(CZ) M100101215 Institutional support: RVO:68378271 Keywords : HIPIMS * thin films * hollow cathode Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.867, year: 2013

Absolute atomic hydrogen density distribution in a hollow cathode discharge by two-photon polarization spectroscopy

International Nuclear Information System (INIS)

Gonzalo, A B; Rosa, M I de la; Perez, C; Mar, S; Gruetzmacher, K

2004-01-01

We report on quantitative measurements of ground-state atomic hydrogen densities in a stationary plasma far off thermodynamic equilibrium, generated in a hollow cathode discharge, by two-photon polarization spectroscopy via the 1S-2S transition. Absolute densities are obtained using a well established calibration method based on the non-resonant two-photon polarization signal of xenon gas at room temperature, which serves as the reference at the wavelength of the hydrogen transition. This study is dedicated to demonstrating the capability of two-photon polarization spectroscopy close to the detection limit. Therefore, it requires single-longitudinal mode UV-laser radiation provided by an advanced UV-laser spectrometer

Local Electric Field Strength in a Hollow Cathode Determined by Stark Splitting of the 2S Level of Hydrogen Isotopes by Optogalvanic Spectroscopy

International Nuclear Information System (INIS)

Perez, C.; Rosa, M. I. de la; Gruetzmacher, K.; Fuentes, L. M.; Gonzalo, A. B.

2008-01-01

In this work we present Doppler-free two-photon optogalvanic spectroscopy as a tool to measure the electric field strength in the cathode fall region of a hollow cathode discharge via the Stark splitting of the 2S level of atomic deuterium. The strong electric field strength present in the hollow cathode is determined for various discharge conditions which allows studying the corresponding variations of the cathode fall, and its changes with discharge operation time.

Hollow Carbon Nanofiber-Encapsulated Sulfur Cathodes for High Specific Capacity Rechargeable Lithium Batteries

KAUST Repository

Zheng, Guangyuan; Yang, Yuan; Cha, Judy J.; Hong, Seung Sae; Cui, Yi

2011-01-01

Sulfur has a high specific capacity of 1673 mAh/g as lithium battery cathodes, but its rapid capacity fading due to polysulfides dissolution presents a significant challenge for practical applications. Here we report a hollow carbon nanofiber

Comparison of trimethylgallium and triethylgallium as “Ga” source materials for the growth of ultrathin GaN films on Si (100) substrates via hollow-cathode plasma-assisted atomic layer deposition

International Nuclear Information System (INIS)

Alevli, Mustafa; Haider, Ali; Kizir, Seda; Leghari, Shahid A.; Biyikli, Necmi

2016-01-01

GaN films grown by hollow cathode plasma-assisted atomic layer deposition using trimethylgallium (TMG) and triethylgallium (TEG) as gallium precursors are compared. Optimized and saturated TMG/TEG pulse widths were used in order to study the effect of group-III precursors. The films were characterized by grazing incidence x-ray diffraction, atomic force microscopy, x-ray photoelectron spectroscopy, and spectroscopic ellipsometry. Refractive index follows the same trend of crystalline quality, mean grain, and crystallite sizes. GaN layers grown using TMG precursor exhibited improved structural and optical properties when compared to GaN films grown with TEG precursor

Comparison of trimethylgallium and triethylgallium as “Ga” source materials for the growth of ultrathin GaN films on Si (100) substrates via hollow-cathode plasma-assisted atomic layer deposition

Energy Technology Data Exchange (ETDEWEB)

Alevli, Mustafa, E-mail: mustafaalevli@marmara.edu.tr [Department of Physics, Marmara University, Göztepe Kadıköy, 34722 İstanbul (Turkey); Haider, Ali; Kizir, Seda; Leghari, Shahid A.; Biyikli, Necmi, E-mail: biyikli@unam.bilkent.edu.tr [Institute of Materials Science and Nanotechnology, Bilkent University, Bilkent, 06800 Ankara, Turkey and National Nanotechnology Research Center (UNAM), Bilkent University, Bilkent, 06800 Ankara (Turkey)

2016-01-15

GaN films grown by hollow cathode plasma-assisted atomic layer deposition using trimethylgallium (TMG) and triethylgallium (TEG) as gallium precursors are compared. Optimized and saturated TMG/TEG pulse widths were used in order to study the effect of group-III precursors. The films were characterized by grazing incidence x-ray diffraction, atomic force microscopy, x-ray photoelectron spectroscopy, and spectroscopic ellipsometry. Refractive index follows the same trend of crystalline quality, mean grain, and crystallite sizes. GaN layers grown using TMG precursor exhibited improved structural and optical properties when compared to GaN films grown with TEG precursor.

A Hollow-Structured Manganese Oxide Cathode for Stable Zn-MnO₂ Batteries.

Science.gov (United States)

Guo, Xiaotong; Li, Jianming; Jin, Xu; Han, Yehu; Lin, Yue; Lei, Zhanwu; Wang, Shiyang; Qin, Lianjie; Jiao, Shuhong; Cao, Ruiguo

2018-05-05

Aqueous rechargeable zinc-manganese dioxide (Zn-MnO₂) batteries are considered as one of the most promising energy storage devices for large scale-energy storage systems due to their low cost, high safety, and environmental friendliness. However, only a few cathode materials have been demonstrated to achieve stable cycling for aqueous rechargeable Zn-MnO₂ batteries. Here, we report a new material consisting of hollow MnO₂ nanospheres, which can be used for aqueous Zn-MnO₂ batteries. The hollow MnO₂ nanospheres can achieve high specific capacity up to ~405 mAh g −1 at 0.5 C. More importantly, the hollow structure of birnessite-type MnO₂ enables long-term cycling stability for the aqueous Zn-MnO₂ batteries. The excellent performance of the hollow MnO₂ nanospheres should be due to their unique structural properties that enable the easy intercalation of zinc ions.

Influence of the radial spacing between cathodes on the surface composition of iron samples sintered by hollow cathode electric discharge

Directory of Open Access Journals (Sweden)

Brunatto S.F.

2001-01-01

Full Text Available The present work reports an investigation of the influence of the radial spacing between cathodes on the iron sintering process by hollow cathode electrical discharge, with surface enrichment of the alloying elements Cr and Ni. Pressed cylindrical samples of 9.5 mm diameter and density of 7.0 ± 0.1 g/cm³ were prepared by compaction of Ancorsteel 1000C iron powder. These samples, constituting the central cathode, were positioned concentrically in the interior of an external cathode machined from a tube of stainless steel AISI 310 (containing: 25% Cr, 16% Ni, 1.5% Mn, 1.5% Si, 0.03% C and the remainder Fe. Sintering was done at 1150 °C, for 120 min, utilizing radial spacings between the central and hollow cathodes of 3, 6 and 9 mm and a gas mixture of 80% Ar and 20% H2, with a flow rate of 5 cm³/s at a pressure of 3 Torr. The electric discharge was generated using a pulsed voltage power source, with a period of 200 mus. The radial spacing had only a slight influence on the quantity of atoms of alloying elements deposited and diffused on the surface of the sample. Analysis with a microprobe showed the presence of chrome (up to 4.0% and nickel (up to 3.0%, in at. % at the surface of the samples. This surface enrichment can be attributed to the mechanism of sputtering of the metallic atoms present in the external cathode, with the deposition of these elements on the sample surface and consequent diffusion within the sample.

Ionization and excitation of uranium in a hollow-cathode lamp

International Nuclear Information System (INIS)

Gagne, J.M.; Pianarosa, P.; Larin, G.; Saint-Dizier, J.P.; Bouchard, P.

1981-01-01

The influence of different carrier gases (Ne,Ar,Kr,Xe) their pressure, and discharge current on the excitation and ionization of uranium atoms in a vapor generator of hollow-cathode design has been investigated by monitoring emission line intensities. From our measurements of line intensities as a function of the carrier gas we obtain an indication of the role of Penning collisions on the excitation of radiative levels in U II

Atomization of thorium in a hollow-cathode type discharge

International Nuclear Information System (INIS)

Pianarosa, P.; Demers, Y.; Gagne, J.M.

1984-01-01

The atomization of thorium metal in a hollow-cathode electrical discharge has been investigated. Laser absorption spectroscopy with the laser tuned on the 5760.55 A (0-17355 1 cm -1 ) transition of Th I was used to evaluate the density of atoms in the 3 F 2 ground state. The results obtained (densities up to 10 13 atoms cm -3 ) show that our discharge tube is a suitable source of thorium metal atoms for laser assisted spectroscopic analysis of this element. (author)

Hall Current Plasma Source Having a Center-Mounted or a Surface-Mounted Cathode

Science.gov (United States)

Martinez, Rafael A. (Inventor); Williams, John D. (Inventor); Moritz, Jr., Joel A. (Inventor); Farnell, Casey C. (Inventor)

2018-01-01

A miniature Hall current plasma source apparatus having magnetic shielding of the walls from ionized plasma, an integrated discharge channel and gas distributor, an instant-start hollow cathode mounted to the plasma source, and an externally mounted keeper, is described. The apparatus offers advantages over other Hall current plasma sources having similar power levels, including: lower mass, longer lifetime, lower part count including fewer power supplies, and the ability to be continuously adjustable to lower average power levels using pulsed operation and adjustment of the pulse duty cycle. The Hall current plasma source can provide propulsion for small spacecraft that either do not have sufficient power to accommodate a propulsion system or do not have available volume to incorporate the larger propulsion systems currently available. The present low-power Hall current plasma source can be used to provide energetic ions to assist the deposition of thin films in plasma processing applications.

Experiments with a large sized hollow cathode discharge fed with argon

International Nuclear Information System (INIS)

Bastian, C.; Boeschoten, F.; Hekman, H.; Komen, R.; Riske, H.P.; Iersel, A. van.

1974-04-01

Several plasma parameters which are pertinent to the rotation of the plasma column of the hollow cathode discharge ''John Luce'' were measured. Several improvements to the device were made, notably concerning the construction of the electrodes and their supports. The ion temperature, Tsub(i), was measured with a Fabry-Perot interferometer; depending on arc current and gas flow Tsub(i) may be varied in argon arc in the range 1-10 eV. The magnetic field strength, B, is adjustable from 600-6000 Gauss. The plasma column is fully ionized, and for higher values of Tsub(i) and B it is also fully magnetized (ωsub(ci)tausub(i) > 1). Simultaneous Doppler-shift measurements of the Asup(II) line 4806 A reveal that the plasma column rotates non-uniformly around its axis. (Order of magnitude of angular frequency is 10 5 rad/sec.) At larger distances from the axis the rotation was measured with a pendulum and with a directional Langmuir Probe. The object of the experiments is to disclose the connection between this rotation and the stability of the plasma column. Langmuir Probes are used to measure radial density profiles under various conditions in the arc. A flat probe with its normal to the surface pointing in radial direction makes reliable ion density measurements possible, even in the presence of a magnetic field. Floating potential measurements were used in order to estimate the radial electric field strength and the drift velocity which is related to it. The electron temperature, Tsub(e), is measured with less accuracy

Cathode plasma expansion in diode with explosive emission

International Nuclear Information System (INIS)

Zuo Yinghong; Fan Ruyu; Wang Jianguo; Zhu Jinhui

2012-01-01

The evolution characteristics of the cathode plasma in a planar diode with explosive emission were analyzed. Be- sides the axial expansion which can reduce the effective anode-cathode gap, the radial expansion of the cathode plasma which can affect the effective emitting area was also taken into account. According to the Child-Langmuir law and the experimental data of current and voltage with a electron vacuum diode under four-pulse mode, the dynamics of the cathode plasma was investigated, on the assumption that the radial speeds of the cathode plasma was approximately equal to the axial speed. The results show that the radial and axial expansion speeds of the cathode plasma are 0.9-2.8 cm/μs. (authors)

Nitrogen Atom Energy Distributions in a Hollow-cathode Planar Sputtering Magnetron

International Nuclear Information System (INIS)

Ruzic, D.N.; Goeckner, M.J.; Cohen, S.A.; Wang, Zhehui

1999-01-01

Energy distributions of N atoms in a hollow-cathode planar sputtering magnetron were obtained by use of optical emission spectroscopy. A characteristic line, N I 8216.3 , well-separated from molecular nitrogen emission bands, was identified. Jansson's nonlinear spectral deconvolution method, refined by minimization of χ w ampersand sup2; , was used to obtain the optimal deconvolved spectra. These showed nitrogen atom energies from 1 eV to beyond 500 eV. Based on comparisons with VFTRIM results, we propose that the energetic N atoms are generated from N 2 + ions after these ions are accelerated through the sheath and dissociatively reflect from the cathode

Uranium vapor generator: pulsed hollow cathode lamp

International Nuclear Information System (INIS)

Carleer, M.; Gagne, J.; Leblanc, B.; Demers, Y.; Mongeau, B.

1979-01-01

The production of uranium vapors has been studied in the 5 L 0 6 ground state using a pulsed hollow cathode lamp. The evolution of the 238 U ( 5 L 0 6 ) concentration with time has been studied with Xe and Ar as buffer gases. A density of 2.7 x 10 13 atoms cm -3 was obtained with Xe as a buffer gas. In addition, those measurements, obtained from the absorption of a laser beam tuned to the 5758.143 A ( 5 L 0 6 -17,361 7 L 6 ) transition, allowed the determination of the transition probability A=2.1 x 10 5 sec -1 and of the branching ratio BR=0.08 for this transition

Optical constants of silicon-like (Si:Ox:Cy:Hz) thin films deposited on quartz using hexamethyldisiloxane in a remote RF hollow cathode discharge plasma

International Nuclear Information System (INIS)

Saloum, S.; Naddaf, M.

2008-01-01

Deposition of amorphous silicon-like (Si:O x :C y :H z ) thin films in a remote RF hollow cathode discharge plasma using Hexamethyldisoloxane as monomer and Ar as feed gas; has been investigated for films optical constants and plasma diagnostic as a function of RF power (100-300 W) and precursor flow rate (1-10 sccm). Plasma diagnostic has been performed using optical emission spectroscopy (OES). The optical constants (refractive index, extinction coefficient and dielectric constant) have been obtained by reflection/transmission measurements in the range 300-700 nm. It is found that the refractive index increases from 1.92 to 1.97 with increasing power from 100 to 300 W, and from 1.70 to 1.92 with increasing precursor flow rate from 1 to 10 sccm. The optical energy-band gap E g and the optical-absorption tail ΔE have been estimated from optical absorption spectra, it is found that E g decreases from 3.28 eV to 3.14 eV with power increase from 100 to 300 W, and from 3.54 eV to 3.28 eV with precursor flow rate increase from 1 to 10 sccm. ΔE is found to increase with applied RF power and precursor flow rate increase. The dependence of optical constants on deposition parameters has been correlated to plasma OES. (author)

Transition Metal Hollow Nanocages as Promising Cathodes for the Long-Term Cyclability of Li–O2 Batteries

Directory of Open Access Journals (Sweden)

Amrita Chatterjee

2018-05-01

Full Text Available As a step towards efficient and cost-effective electrocatalytic cathodes for Li–O2 batteries, highly porous hausmannite-type Mn3O4 hollow nanocages (MOHNs of a large diameter of ~250 nm and a high surface area of 90.65 m2·g−1 were synthesized and their physicochemical and electrochemical properties were studied in addition to their formation mechanism. A facile approach using carbon spheres as the template and MnCl2 as the precursor was adopted to suit the purpose. The MOHNs/Ketjenblack cathode-based Li–O2 battery demonstrated an improved cyclability of 50 discharge–charge cycles at a specific current of 400 mA·g−1 and a specific capacity of 600 mAh·g−1. In contrast, the Ketjenblack cathode-based one can sustain only 15 cycles under the same electrolytic system comprised of 1 M LiTFSI/TEGDME. It is surmised that the unique hollow nanocage morphology of MOHNs is responsible for the high electrochemical performance. The hollow nanocages were a result of the aggregation of crystalline nanoparticles of 25–35 nm size, and the mesoscopic pores between the nanoparticles gave rise to a loosely mesoporous structure for accommodating the volume change in the MOHNs/Ketjenblack cathode during electrocatalytic reactions. The improved cyclic stability is mainly due to the faster mass transport of the O2 through the mesoscopic pores. This work is comparable to the state-of-the-art experimentations on cathodes for Li–O2 batteries that focus on the use of non-precious transition materials.

Plasma-induced field emission and plasma expansion of carbon nanotube cathodes

International Nuclear Information System (INIS)

Liao Qingliang; Zhang Yue; Qi Junjie; Huang Yunhua; Xia Liansheng; Gao Zhanjun; Gu Yousong

2007-01-01

High intensity electron emission cathodes based on carbon nanotube films have been successfully fabricated. An investigation of the explosive field emission properties of the carbon nanotube cathode in a double-pulse mode was presented and a high emission current density of 245 A cm -2 was obtained. The formation of the cathode plasma layer was proved and the production process of the electron beams from the cathode was explained. The time and space resolution of the electron beams flow from the cathode was investigated. The plasma expanded at a velocity of ∼8.17 cm μs -1 towards the anode and influenced on the intensity and distribution of electron beams obviously. The formation of cathode plasma had no preferential position and the local enhancement of electron beams was random. This carbon nanotube cathode appears to be suitable for high-power microwave device applications

Diagnostics of N2 Ar plasma mixture excited in a 13.56 MHz hollow cathode discharge system: application to remote plasma treatment of polyamide surface

Science.gov (United States)

Saloum, S.; Naddaf, M.; Alkhaled, B.

2008-02-01

N2-x% Ar plasma gas mixture, generated in a hollow cathode RF discharge system, has been characterized by both optical emission spectroscopy (OES) and double Langmuir probe, as a function of experimental parameters: total pressure (5-33 Pa), and different fractions of argon (7 <= x <= 80), at a constant applied RF power of 300 W. N2 dissociation degree has been investigated qualitatively by both the actinometry method and the ratio I_N/I_{N_2} of the atomic nitrogen line emission intensity at 672.3 nm to the vibrational band (0-0) of the N2 second positive system at 337.1 nm. Both methods showed that the increase in argon fraction enhances the dissociation of N2, with a maximum at x = 50 for the pressure of 5 Pa, although the two methods give two opposite trends as a function of total pressure. Spectroscopic measurements showed that the vibrational temperature of the N2 second positive system increases with both argon fraction and total pressure increase, it lies between 4900 and 12 300 K. Langmuir probe measurements showed that, in the remote zone, the electron temperature falls in the range 1.57-1.75 eV, the N_{2}^{+} density varies between 5 × 109 and 1.4 × 1010 cm-3 and that both the plasma ionization degree and electron temperature increase towards the source. In addition, the process of plasma-polyamide (PA) surface interaction, in the remote plasma zone, has been studied through OES analysis during plasma treatment of PA to monitor the possible emissions due to the polymer etching. An increase in atomic nitrogen line (672.3 nm) intensity is obtained, atomic carbon line (833.52 nm) and the band emission (0-0) from the CN (B 2Σ+-X 2Σ+) violet system were observed. The PA surface modification has been confirmed through the improvement of its hydrophilic character as the water contact angle measured after the plasma treatment significantly decreased.

Diagnostics of N2-Ar plasma mixture excited in A 13.56 MHz hollow cathode discharge system: Application to remote plasma treatment of polyamide surface

International Nuclear Information System (INIS)

Saloum, S.; Naddaf, M.; Al-khaled, B.

2009-01-01

N 2 -x % Ar plasma gas mixture, generated in a hollow cathode RF discharge system, has been characterized by both optical emission spectroscopy (OES) and double langmuir probe, as a function of experimental parameters: Total pressure (5-33 Pa), and different fractions of argon (7≤ x ≤ 80), at a constant applied RF power of 300 W. N 2 dissociation degree has been investigated qualitatively by both actinometry method and the ratio of the atomic nitrogen line emission intensity at 672.3 nm to the vibrational band (0-0) of the N 2 second positive system at 337.1 nm. Both methods showed that the increase of argon fraction enhances the dissociation of N 2 , with a maximum at x=50 for the pressure of 5 Pa, although the two methods give two opposite trends as a function of total pressure. Spectroscopic measurements showed that the vibrational temperature of N 2 second positive system increases with both argon fraction and total pressure increase, it lies between 4900 K and 12300 K. Langmuir probe measurements showed that, in the remote zone, the electron temperature falls in the range 1.57-1.75 eV, the N 2 + density varies between 5.10 9 cm-3 and 1.4 10 10 cm -3 , and that both the plasma ionization degree and electron temperature increase towards the source. In addition, the process of plasma-polyamide surface interaction, in the remote plasma zone, has been studied through optical emission spectroscopy analysis during plasma treatment of polyamide to monitor the possible emissions due to the polymer etching. An increase of atomic nitrogen line (672.3 nm) intensity is obtained, atomic carbon line (833.52 nm) and the band emission (0-0) from CN (B 2 Σ + -X 2 Σ + ) violet system were observed. The polyamide surface modification has been confirmed through the improvement of its hydrophilic character as the water contact angle measured after the plasma treatment significantly decreased. (author)

Diagnostics of N2-Ar plasma mixture excited in a 13.56 MHz hollow cathode discharge system: application to remote plasma treatment of polyamide surface

International Nuclear Information System (INIS)

Saloum, S; Naddaf, M; Alkhaled, B

2008-01-01

N 2 -x% Ar plasma gas mixture, generated in a hollow cathode RF discharge system, has been characterized by both optical emission spectroscopy (OES) and double Langmuir probe, as a function of experimental parameters: total pressure (5-33 Pa), and different fractions of argon (7 ≤ x ≤ 80), at a constant applied RF power of 300 W. N 2 dissociation degree has been investigated qualitatively by both the actinometry method and the ratio I N /I N 2 of the atomic nitrogen line emission intensity at 672.3 nm to the vibrational band (0-0) of the N 2 second positive system at 337.1 nm. Both methods showed that the increase in argon fraction enhances the dissociation of N 2 , with a maximum at x = 50 for the pressure of 5 Pa, although the two methods give two opposite trends as a function of total pressure. Spectroscopic measurements showed that the vibrational temperature of the N 2 second positive system increases with both argon fraction and total pressure increase, it lies between 4900 and 12 300 K. Langmuir probe measurements showed that, in the remote zone, the electron temperature falls in the range 1.57-1.75 eV, the N 2 + density varies between 5 x 10 9 and 1.4 x 10 10 cm -3 and that both the plasma ionization degree and electron temperature increase towards the source. In addition, the process of plasma-polyamide (PA) surface interaction, in the remote plasma zone, has been studied through OES analysis during plasma treatment of PA to monitor the possible emissions due to the polymer etching. An increase in atomic nitrogen line (672.3 nm) intensity is obtained, atomic carbon line (833.52 nm) and the band emission (0-0) from the CN (B 2 Σ + -X 2 Σ + ) violet system were observed. The PA surface modification has been confirmed through the improvement of its hydrophilic character as the water contact angle measured after the plasma treatment significantly decreased

Plasma distribution of cathodic ARC deposition system

International Nuclear Information System (INIS)

Anders, S.; Raoux, S.; Krishnan, K.; MacGill, R.A.; Brown, I.G.

1996-01-01

The plasma distribution using a cathodic arc plasma source with and without magnetic macroparticle filter has been determined by depositing on a transparent plastic substrate and measuring the film absorption. It was found that the width of the distribution depends on the arc current, and it also depends on the cathode material which leads to a spatial separation of the elements when an alloy cathode is used. By applying a magnetic multicusp field near the exit of the magnetic filter, it was possible to modify the plasma distribution and obtain a flat plasma profile with a constant and homogeneous elemental distribution

Dual-Function Electrocatalytic and Macroporous Hollow-Fiber Cathode for Converting Waste Streams to Valuable Resources Using Microbial Electrochemical Systems

KAUST Repository

Katuri, Krishna; Kalathil, Shafeer; Ragab, Ala'a; Bian, Bin; AlQahtani, Manal Faisal; Pant, Deepak; Saikaly, Pascal

2018-01-01

Dual-function electrocatalytic and macroporous hollow-fiber cathodes are recently proposed as promising advanced material for maximizing the conversion of waste streams such as wastewater and waste CO2 to valuable resources (e.g., clean freshwater, energy, value-added chemicals) in microbial electrochemical systems. The first part of this progress report reviews recent developments in this type of cathode architecture for the simultaneous recovery of clean freshwater and energy from wastewater. Critical insights are provided on suitable materials for fabricating these cathodes, as well as addressing some challenges in the fabrication process with proposed strategies to overcome them. The second and complementary part of the progress report highlights how the unique features of this cathode architecture can solve one of the intrinsic bottlenecks (gas-liquid mass transfer limitation) in the application of microbial electrochemical systems for CO2 reduction to value-added products. Strategies to further improve the availability of CO2 to microbial catalysts on the cathode are proposed. The importance of understanding microbe-cathode interactions, as well as electron transfer mechanisms at the cathode-cell and cell-cell interface to better design dual-function macroporous hollow-fiber cathodes, is critically discussed with insights on how the choice of material is important in facilitating direct electron transfer versus mediated electron transfer.

Dual-Function Electrocatalytic and Macroporous Hollow-Fiber Cathode for Converting Waste Streams to Valuable Resources Using Microbial Electrochemical Systems

KAUST Repository

Katuri, Krishna

2018-04-30

Dual-function electrocatalytic and macroporous hollow-fiber cathodes are recently proposed as promising advanced material for maximizing the conversion of waste streams such as wastewater and waste CO2 to valuable resources (e.g., clean freshwater, energy, value-added chemicals) in microbial electrochemical systems. The first part of this progress report reviews recent developments in this type of cathode architecture for the simultaneous recovery of clean freshwater and energy from wastewater. Critical insights are provided on suitable materials for fabricating these cathodes, as well as addressing some challenges in the fabrication process with proposed strategies to overcome them. The second and complementary part of the progress report highlights how the unique features of this cathode architecture can solve one of the intrinsic bottlenecks (gas-liquid mass transfer limitation) in the application of microbial electrochemical systems for CO2 reduction to value-added products. Strategies to further improve the availability of CO2 to microbial catalysts on the cathode are proposed. The importance of understanding microbe-cathode interactions, as well as electron transfer mechanisms at the cathode-cell and cell-cell interface to better design dual-function macroporous hollow-fiber cathodes, is critically discussed with insights on how the choice of material is important in facilitating direct electron transfer versus mediated electron transfer.

Hollow cathode discharges with gas flow: numerical modelling for the effect on the sputtered atoms and the deposition flux

International Nuclear Information System (INIS)

Bogaerts, Annemie; Okhrimovskyy, Andriy; Baguer, Neyda; Gijbels, Renaat

2005-01-01

A model is developed for a cylindrical hollow cathode discharge (HCD), with an axial gas flow (entering through a hole in the cathode bottom). The model combines a commercial computational fluid dynamics program 'FLUENT' to compute the gas flow, with home-developed Monte Carlo and fluid models for the plasma behaviour. In this paper, we focus on the behaviour of the sputtered atoms, and we investigate how the gas flow affects the sputtered atom density profiles and the fluxes, which is important for sputter deposition. The sputtered atom density profiles are not much affected by the gas flow. The flux, on the other hand, is found to be significantly enhanced by the gas flow, but in the present set-up it is far from uniform in the radial direction at the open end of the HCD, where a substrate for deposition could be located

Study of the three-step photoionization of uranium using a hollow cathode discharge tube

International Nuclear Information System (INIS)

Hu, Q.; Yin, L.; Zhang, Y.; Jin, C.; Cui, J.; Su, H.; Lin, F.

1986-01-01

The hollow cathode discharge (HCD) tube as a spectral light source has been developed. Because any element including refractory metals can be atomized by the cathode sputtering effect in HCD, a simple and reliable atomic vapor source produced by HCD has been widely used in laser spectroscopy. To the authors' knowledge, there is no previous work on the photoionization processes of metal atoms using an HCD tube. Here the authors report their study of the resonant three-step ionization of U in a homemade HCD tube

Space and Temporal Correlation between the Moving Virtual Anode and the Ionization Growth in a Transient Hollow Cathode Discharge

International Nuclear Information System (INIS)

Zambra, M.; Moreno, J.; Soto, L.; Silva, P.; Sylvester, G.; Alarcon, H.

2001-01-01

A Transient Hollow Cathode Discharge is a low-pressure high-voltage electric discharge between plane parallel electrodes with an axial hole in the cathode. There are essential ionization events which lead to final electrical breakdown, between them the enhanced ionization processes taking place inside the Hollow Cathode Region (HCR) and the virtual anode moving in the interelectrode region, which extends the anode potential to within the HCR. In previous works it was studied the virtual anode speed in the A-K gap and the temporal evolution of the ionization growth in the HCR separately. In this paper, the virtual anode speed has been studied temporal and space correlated with the ionization growth inside the HCR. The presence of the moving virtual anode and the ionization growth has been diagnosed by means of capacitive probes and observing the light emission at 656 nm (H-α) from a point behind the cathode aperture respectively. The discharge was operated in hydrogen gas, at pressure in the range 100-300 mTorr, with 5 mm cathode aperture and at 30 kV maximum voltage. (author)

Oxide cathodes produced by plasma deposition

International Nuclear Information System (INIS)

Scheitrum, G.; Caryotakis, G.; Pi, T.; Umstattd, R.; Brown, I.; Montiero, O.

1997-01-01

These are two distinct applications for high-current-density, long-life thermionic cathodes. The first application is as a substitute for explosive emission cathodes used in high-power microwave (HPM) devices being developed for Air Force programs. The second application is in SLAC's X-band klystrons for the Next Linear Collider (NLC). SLAC, UCD, and LBL are developing a plasma deposition process that eliminates the problems with binders, carbonate reduction, peeling, and porosity. The emission layer is deposited using plasma deposition of metallic barium in vacuum with an oxygen background gas. An applied bias voltage drives the oxide plasma into the nickel surface. Since the oxide is deposited directly, it does not have problems with poisoning from a hydrocarbon binder. The density of the oxide layer is increased from the 40--50% for standard oxide cathodes to nearly 100% for plasma deposition

Observation of a very high electron current extraction mode in a hollow cathode discharge

International Nuclear Information System (INIS)

Hershcovitch, A.

1993-01-01

Earlier results by Hershcovitch, Kovarik, and Prelec in J. Appl. Phys. 67, 671 (1990) proved that, in a low-pressure operating mode, hollow cathode discharges can have a two-component electron population, one of which is that of ''fast'' electrons having an energy corresponding to the cathode potential and a thermal spread of about 0.13 eV, which could form a basis for an excellent electron gun. Investigations of extracted electron currents in this low pressure mode indicate the existence of a narrow pressure range characterized by very high electron current extraction

Enhancement of opto-galvanic signals in the hollow cathode dark space: application to single colour 3-photon ionization of uranium

International Nuclear Information System (INIS)

Pradhan, S.; Manohar, K.G.; Marathe, A.; Rawat, V.S.; Sridhar, G.; Singh, S.; Jagatap, B.N.; Gantayet, L.M.

1999-01-01

Opto-galvanic effect in a hollow cathode lamp offers a very convenient method of spectroscopy of many elements of interest including refractory elements like uranium. The dependence of opto-galvanic signals on various discharge parameters like buffer gas pressure, buffer gas type, discharge current, diameter of the hollow cavity of the cathode etc. have been studied. Various mechanisms for the generation of opto-galvanic signals based on electron impact ionization and super elastic collisions have been proposed. It appears that both these processes do contribute to the opto-galvanic signals simultaneously, under specific discharge conditions

RF Electron Gun with Driven Plasma Cathode

CERN Document Server

Khodak, Igor

2005-01-01

It's known that RF guns with plasma cathodes based on solid-state dielectrics are able to generate an intense electron beam. In this paper we describe results of experimental investigation of the single cavity S-band RF gun with driven plasma cathode. The experimental sample of the cathode based on ferroelectric ceramics has been designed. Special design of the cathode permits to separate spatially processes of plasma development and electron acceleration. It has been obtained at RF gun output electron beam with particle energy ~500 keV, pulse current of 4 A and pulse duration of 80 ns. Results of experimental study of beam parameters are referred in. The gun is purposed to be applied as the intense electron beam source for electron linacs.

Time resolved diagnostics and kinetic modelling of a modulated hollow cathode discharge of NO2

International Nuclear Information System (INIS)

Castillo, M; Herrero, V J; Mendez, I; Tanarro, I

2004-01-01

The transients associated with the ignition and the extinction of the cold plasma produced in a low frequency, square-wave modulated, hollow cathode discharge of nitrogen dioxide are characterized by time resolved emission spectroscopy, mass spectrometry and electrical probes. The temporal evolution of the concentrations of neutral species created or destroyed in the NO 2 discharges are compared with the predictions of a simple kinetic model previously developed for discharges of other nitrogen oxides (N 2 O and NO). The physical conditions of pressure, gas flow rate, modulation frequency and electrical current in the NO 2 plasma were selected in order to highlight the time-dependent behaviour of some of the stable species formed in the discharge, especially the nitrogen oxide products, whose concentrations show transient maxima. The usefulness of the analysis of the transient results is emphasized as a means to evaluate the relevance of the different elementary processes and as a key to estimate the values of some of the rate constants critical to the modelling. This work is dedicated to the memory of Professor Jose Campos

Statistical analysis on hollow and core-shell structured vanadium oxide microspheres as cathode materials for Lithium ion batteries

Directory of Open Access Journals (Sweden)

Xing Liang

2018-06-01

Full Text Available In this data, the statistical analyses of vanadium oxide microspheres cathode materials are presented for the research article entitled “Statistical analyses on hollow and core-shell structured vanadium oxides microspheres as cathode materials for Lithium ion batteries” (Liang et al., 2017 [1]. This article shows the statistical analyses on N2 adsorption-desorption isotherm and morphology vanadium oxide microspheres as cathode materials for LIBs. Keywords: Adsorption-desorption isotherm, Pore size distribution, SEM images, TEM images

Examining the effects of fill gas pressure on the distribution of copper atoms in a hollow cathode lamp

International Nuclear Information System (INIS)

Oliver, D.R.; Finlayson, T.R.

1996-01-01

A modified Copper Hollow Cathode lamp has been used to examine the effects of fill gas pressure on the distribution of sputtered Copper atoms in the body of the lamp. The lamp was modified by placing a quartz disc above the cathode, perpendicular to both the cathode bore and the cathode-anode axis. While the lamp is operating, some of the Copper that has been sputtered out of the cathode bore is deposited on the disc. Modified lamps have been operated at a variety of pressures, and the resulting deposition profiles recorded using an optical microscope. A summary of variations between different pressures are presented

Observation of even-parity autoionization states of uranium by three-colour photoionization optogalvanic spectroscopy in U–Ne hollow cathode discharges

International Nuclear Information System (INIS)

Mandal, P.K.; Seema, A.U.; Das, R.C.; Shah, M.L.; Dev, Vas; Suri, B.M.

2013-01-01

Three-colour three-step photoionization spectroscopy of uranium has been performed in a U–Ne hollow cathode discharge tube by temporally resolving three-colour photoionization optogalvanic (PIOG) signal from the normal optogalvanic (OG) signal using three tunable pulsed dye lasers. U–Ne hollow cathode discharge tube has been used as a source of uranium atomic vapours and photoionization detector. Using this technique, photoionization spectra of uranium have been investigated systematically in the energy region 52,150–52,590 cm −1 , through three different excitation pathways, originating from its ground state, 0 cm −1 ( 5 L o 6 ). By analysing the three-colour photoionization spectra sixty new even-parity autoionization resonances of uranium have been identified and their probable total angular momentum (J) values have been assigned according to the J-momentum selection rule. The J-value of five autoionization resonances, which have been observed either through all three excitation pathways or through two different excitation pathways where J-value of the second excited levels differs by two, has been assigned uniquely. -- Highlights: ► Three-colour photoionization optogalvanic spectroscopy of uranium was performed in a U–Ne hollow cathode discharge tube. ► Hollow cathode discharge tube was used as a source of atomic vapour and laser ionisation detector. ► Uranium photoionization spectra were investigated through three different three-colour photoionization schemes. ► Sixty new even-parity autoionization levels of uranium were identified. ► J-value of five autoionization levels was assigned uniquely

Integrated Energetic Ion Mitigation for High Power Plasma Cathodes, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — The innovation proposed is a hollow cathode that integrates mitigation methods to suppress wear to the keeper. Recent advances in the magnetic topology in Hall...

Laser optogalvanic wavelength calibration with a commercial hollow cathode iron - neon discharge lamp

Science.gov (United States)

Zhu, Xinming; Nur, Abdullahi H.; Misra, Prabhakar

1994-01-01

351 optogalvanic transitions have been observed in the 337 - 598 nm wavelength region using an iron - neon hollow cathode discharge lamp and a pulsed tunable dye laser. 223 of these have been identified as transitions associated with neon energy levels. These optogalvanic transitions have allowed, in conjunction with interference fringes recorded concomitantly with an etalon, the calibration of the dye laser wavelength with 0.3/cm accuracy.

Three-dimensional interconnected cobalt oxide-carbon hollow spheres arrays as cathode materials for hybrid batteries

Directory of Open Access Journals (Sweden)

Jiye Zhan

2016-06-01

Full Text Available Hierarchical porous metal oxides arrays is critical for development of advanced energy storage devices. Herein, we report a facile template-assisted electro-deposition plus glucose decomposition method for synthesis of multilayer CoO/C hollow spheres arrays. The CoO/C arrays consist of multilayer interconnected hollow composite spheres with diameters of ∼350 nm as well as thin walls of ∼20 nm. Hierarchical hollow spheres architecture with 3D porous networks are achieved. As cathode of high-rate hybrid batteries, the multilayer CoO/C hollow sphere arrays exhibit impressive enhanced performances with a high capacity (73.5 mAh g−1 at 2 A g−1, and stable high-rate cycling life (70 mAh g−1 after 12,500 cycles at 2 A g−1. The improved electrochemical performance is owing to the composite hollow-sphere architecture with high contact area between the active materials and electrolyte as well as fast ion/electron transportation path.

Numerical study on rectangular microhollow cathode discharge

International Nuclear Information System (INIS)

He Shoujie; Ouyang Jiting; He Feng; Li Shang

2011-01-01

Rectangular microhollow cathode discharge in argon is investigated by using two-dimensional time-dependent self-consistent fluid model. The electric potential, electric field, particle density, and mean electron energy are calculated. The results show that hollow cathode effect can be onset in the present configuration, with strong electric field and high mean electron energy in the cathode fall while high density and quasineutral plasma in the negative glow. The potential well and electric filed reversal are formed in the negative glow region. It is suggested that the presence of large electron diffusion flux necessitates the field reversal and potential well.

Cathode Effects in Cylindrical Hall Thrusters

Energy Technology Data Exchange (ETDEWEB)

Granstedt, E.M.; Raitses, Y.; Fisch, N. J.

2008-09-12

Stable operation of a cylindrical Hall thruster (CHT) has been achieved using a hot wire cathode, which functions as a controllable electron emission source. It is shown that as the electron emission from the cathode increases with wire heating, the discharge current increases, the plasma plume angle reduces, and the ion energy distribution function shifts toward higher energies. The observed effect of cathode electron emission on thruster parameters extends and clarifies performance improvements previously obtained for the overrun discharge current regime of the same type of thruster, but using a hollow cathode-neutralizer. Once thruster discharge current saturates with wire heating, further filament heating does not affect other discharge parameters. The saturated values of thruster discharge parameters can be further enhanced by optimal placement of the cathode wire with respect to the magnetic field.

The effect of self-absorption in hollow cathode lamp on its temperature

International Nuclear Information System (INIS)

Sobhanian, S.; Naghshara, H.

2014-01-01

It has been shown experimentally that even a small error in the calculation of the temperature inside the hollow-cathode lamp (HCL) and the current applied to the lamp, may cause a tremendous error in determination of the absorption ratio in optical resonance absorption (ORA) method. This effect is intensified nonlinearity for large absorption ratios. If a higher current is applied to a copper hollow cathode lamp, the copper density inside the lamp is increasing rapidly. Due to the cylindrical (axisymmetric) form of the lamp, the density of atoms around the main axis of the lamp becomes greater than that near the internal wall. In this case the auto-absorption (or self-absorption) is occurred and as its result, the emission spectrum produced by copper atoms is locally absorbed before going out from the lamp. This absorption is stronger near the main axis compared with the areas near the wall because of the Gaussian profile of the spectral line. Two different Cu atoms ground state lines with the similar lower state (327.4 nm and 324.7 nm) are used in this work as optical resonance absorption and the absorption coefficient is obtained for three different pressures (0.6, 4.5 and 14 µbar). The best values for copper HCL temperature and for maximum HCL current were found respectively 450 K, and 5mA. (author)

Diagnostics of N{sub 2}-Ar plasma mixture excited in a 13.56 MHz hollow cathode discharge system: application to remote plasma treatment of polyamide surface

Energy Technology Data Exchange (ETDEWEB)

Saloum, S; Naddaf, M; Alkhaled, B [Atomic Energy Commission of Syria (AECS), Physics Department, PO Box 6091, Damascus (Syrian Arab Republic)], E-mail: scientific@aec.org.sy

2008-02-21

N{sub 2}-x% Ar plasma gas mixture, generated in a hollow cathode RF discharge system, has been characterized by both optical emission spectroscopy (OES) and double Langmuir probe, as a function of experimental parameters: total pressure (5-33 Pa), and different fractions of argon (7 {<=} x {<=} 80), at a constant applied RF power of 300 W. N{sub 2} dissociation degree has been investigated qualitatively by both the actinometry method and the ratio I{sub N}/I{sub N{sub 2}} of the atomic nitrogen line emission intensity at 672.3 nm to the vibrational band (0-0) of the N{sub 2} second positive system at 337.1 nm. Both methods showed that the increase in argon fraction enhances the dissociation of N{sub 2}, with a maximum at x = 50 for the pressure of 5 Pa, although the two methods give two opposite trends as a function of total pressure. Spectroscopic measurements showed that the vibrational temperature of the N{sub 2} second positive system increases with both argon fraction and total pressure increase, it lies between 4900 and 12 300 K. Langmuir probe measurements showed that, in the remote zone, the electron temperature falls in the range 1.57-1.75 eV, the N{sub 2}{sup +} density varies between 5 x 10{sup 9} and 1.4 x 10{sup 10} cm{sup -3} and that both the plasma ionization degree and electron temperature increase towards the source. In addition, the process of plasma-polyamide (PA) surface interaction, in the remote plasma zone, has been studied through OES analysis during plasma treatment of PA to monitor the possible emissions due to the polymer etching. An increase in atomic nitrogen line (672.3 nm) intensity is obtained, atomic carbon line (833.52 nm) and the band emission (0-0) from the CN (B {sup 2}{sigma}{sup +}-X {sup 2}{sigma}{sup +}) violet system were observed. The PA surface modification has been confirmed through the improvement of its hydrophilic character as the water contact angle measured after the plasma treatment significantly decreased.

The cathode material for a plasma-arc heater

Science.gov (United States)

Yelyutin, A. V.; Berlin, I. K.; Averyanov, V. V.; Kadyshevskii, V. S.; Savchenko, A. A.; Putintseva, R. G.

1983-11-01

The cathode of a plasma arc heater experiences a large thermal load. The temperature of its working surface, which is in contact with the plasma, reaches high values, as a result of which the electrode material is subject to erosion. Refractory metals are usually employed for the cathode material, but because of the severe erosion do not usually have a long working life. The most important electrophysical characteristic of the electrode is the electron work function. The use of materials with a low electron work function allows a decrease in the heat flow to the cathode, and this leads to an increase in its erosion resistance and working life. The electroerosion of certain materials employed for the cathode in an electric arc plasma generator in the process of reduction smelting of refractory metals was studied.

Development of hollow anode penning ion source for laboratory application

Energy Technology Data Exchange (ETDEWEB)

Das, B.K., E-mail: dasbabu31@gmail.com [Energetics and Electromagnetics Division, Bhabha Atomic Research Centre, Autonagar, Visakhapatnam (India); Shyam, A.; Das, R. [Energetics and Electromagnetics Division, Bhabha Atomic Research Centre, Autonagar, Visakhapatnam (India); Rao, A.D.P. [Department of Nuclear Physics, Andhra University, Visakhapatnam (India)

2012-03-21

The research work presented here focuses for the development of miniature penning type ion source. One hollow anode penning type ion source was developed in our laboratory. The size of the ion source is 38 mm diameter and 55 mm length. The ion source consists of two cathodes, a hollow anode and one piece of rare earth permanent magnet. The plasma was created in the plasma region between cathodes and the hollow anode. The J Multiplication-Sign B force in the region helps for efficient ionization of the gas even in the high vacuum region{approx}1 Multiplication-Sign 10{sup -5} Torr. The ions were extracted in the axial direction with help of the potential difference between the electrodes and the geometry of the extraction angle. The effect of the extraction electrode geometry for efficient extraction of the ions from the plasma region was examined. This ion source is a self extracted ion source. The self extracted phenomena reduce the cost and the size of the ion source. The extracted ion current was measured by a graphite probe. An ion current of more than 200 {mu}A was observed at the probe placed 70 mm apart from the extraction electrode. In this paper, the structure of the ion source, effect of operating pressure, potential difference and the magnetic field on the extracted ion current is reported.

Study on surface adhesion of Plasma modified Polytetrafluoroethylene hollow fiber membrane

Science.gov (United States)

Chen, Jiangrong; Zhang, Huifeng; Liu, Guochang; Guo, Chungang; Lv, Jinglie; Zhangb, Yushan

2018-01-01

Polytetrafluoroethylene (PTFE) is popular membrane material because of its excellent thermal stability, chemical stability and mechanical stability. However, the low surface energy and non-sticky property of PTFE present challenges for modification. In the present study, plasma treatment was performed to improve the surface adhesion of PTFE hollow fiber membrane. The effect of discharge voltage, treatment time on the adhesion of PTFE hollow fiber membrane was symmetrically evaluated. Results showed that the plasma treatment method contributed to improve the surface activity and roughness of PTFE hollow fiber membrane, and the adhesion strength depend significantly on discharge voltage, which was beneficial to seepage pressure of PTFE hollow fiber membrane module. The adhesion strength of PTFE membrane by plasma treated at 220V for 3min reached as high as 86.2 N, far surpassing the adhesion strength 12.7 N of pristine membrane. Furthermore, improvement of content of free radical and composition analysis changes of the plasma modified PTFE membrane were investigated. The seepage pressure of PTFE membrane by plasma treated at 220V for 3min was 0.375 MPa, which means that the plasma treatment is an effective technique to improve the adhesion strength of membrane.

Numerical simulation of cathode plasma dynamics in magnetically insulated vacuum transmission lines

International Nuclear Information System (INIS)

Thoma, C.; Genoni, T. C.; Welch, D. R.; Rose, D. V.; Clark, R. E.; Miller, C. L.; Stygar, W. A.; Kiefer, M. L.

2015-01-01

A novel algorithm for the simulation of cathode plasmas in particle-in-cell codes is described and applied to investigate cathode plasma evolution in magnetically insulated transmission lines (MITLs). The MITL electron sheath is modeled by a fully kinetic electron species. Electron and ion macroparticles, both modeled as fluid species, form a dense plasma which is initially localized at the cathode surface. Energetic plasma electron particles can be converted to kinetic electrons to resupply the electron flux at the plasma edge (the “effective” cathode). Using this model, we compare results for the time evolution of the cathode plasma and MITL electron flow with a simplified (isothermal) diffusion model. Simulations in 1D show a slow diffusive expansion of the plasma from the cathode surface. But in multiple dimensions, the plasma can expand much more rapidly due to anomalous diffusion caused by an instability due to the strong coupling of a transverse magnetic mode in the electron sheath with the expanding resistive plasma layer

Hollow laser plasma self-confined microjet generation

Science.gov (United States)

Sizyuk, Valeryi; Hassanein, Ahmed; CenterMaterials under Extreme Environment Team

2017-10-01

Hollow laser beam produced plasma (LPP) devices are being used for the generation of the self-confined cumulative microjet. Most important place by this LPP device construction is achieving of an annular distribution of the laser beam intensity by spot. An integrated model is being developed to detailed simulation of the plasma generation and evolution inside the laser beam channel. The model describes in two temperature approximation hydrodynamic processes in plasma, laser absorption processes, heat conduction, and radiation energy transport. The total variation diminishing scheme in the Lax-Friedrich formulation for the description of plasma hydrodynamic is used. Laser absorption and radiation transport models on the base of Monte Carlo method are being developed. Heat conduction part on the implicit scheme with sparse matrixes using is realized. The developed models are being integrated into HEIGHTS-LPP computer simulation package. The integrated modeling of the hollow beam laser plasma generation showed the self-confinement and acceleration of the plasma microjet inside the laser channel. It was found dependence of the microjet parameters including radiation emission on the hole and beam radiuses ratio. This work is supported by the National Science Foundation, PIRE project.

Reactive-environment, hollow cathode sputtering: Basic characteristics and application to Al2O3, doped ZnO, and In2O3:Mo

International Nuclear Information System (INIS)

Delahoy, A.E.; Guo, S.Y.; Paduraru, C.; Belkind, A.

2004-01-01

A method for thin-film deposition has been studied. The method is based on metal sputtering in a hollow cathode configuration with supply of a reactive gas in the vicinity of the substrate. The working gas and entrained sputtered atoms exit the cathode through an elongated slot. The reactive gas is thereby largely prevented from reaching the target. The basic operation of the cathode was studied using a Cu target and pulsed power excitation. These studies included the dependence of deposition rate on power, pressure, and flow rate, film thickness profiles, and film resistivity as a function of substrate conditions. Modeling was conducted to calculate the gas velocity distribution and pressure inside the cavity. Al 2 O 3 films were prepared in a reactive environment of oxygen by sputtering an Al target. It was demonstrated that only a very small amount of oxygen passing through the cathode will oxidize (poison) the target, whereas large quantities of oxygen supplied externally to the cathode need not affect the target at all. A very stable discharge and ease of Al 2 O 3 formation were realized in this latter mode. The method was applied to the preparation of transparent, conductive films of ZnO doped with either Al or B. High deposition rates were achieved, and, at appropriate oxygen flow rates, low film resistivities. High-mobility In 2 O 3 :Mo transparent conductors were also prepared, with resistivities as low as 1.9x10 -4 Ω cm. Scaling relations for hollow cathodes, and deposition efficiency, and process comparisons between magnetron sputtering and linear, reactive-environment, hollow cathode sputtering are presented

Effects of spray parameters on the microstructure and property of Al2O3 coatings sprayed by a low power plasma torch with a novel hollow cathode

International Nuclear Information System (INIS)

Li Changjiu; Sun Bo

2004-01-01

Al 2 O 3 coating is deposited using a low power plasma torch with a novel hollow cathode through axial powder injection under a plasma power up to several kilowatts. The effects of the main processing parameters including plasma arc power, operating gas flow and spray distance on particle velocity during spraying, and the microstructure and property of the coating are investigated. The microstructure of the Al 2 O 3 coating is examined using optical microscopy and X-ray diffraction analysis. The property of the coating is characterized by dry rubber wheel abrasive wear test. The velocity of in-flight particle is measured using a velocity/temperature measurement system for spray particle based on thermal radiation from the particle. The dependency of the microstructure and property of the coating on spray particle conditions are examined by comparing the particle velocity, and microstructure and abrasive wear weight loss of subsequent coating deposited by low power plasma spray with those of the coating by conventional plasma spray at a power one order higher. X-ray diffraction analysis of the coating revealed that Al 2 O 3 particles during low power plasma spraying reach to sufficiently melting state prior to impact on the substrate with a velocity comparable to that in conventional plasma spraying. The experiment results have shown that processing parameters have significant influence on the particle conditions and performance of deposited Al 2 O 3 coating. The coating of comparable microstructure and properties to that deposited by conventional plasma spray can be produced under a power one order lower. From the present study, it can be suggested that a comparable coating can be produced despite plasma power level if the comparable particle velocity and molten state are achieved

Neutralizer Hollow Cathode Simulations and Comparisons with Ground Test Data

Science.gov (United States)

Mikellides, Ioannis G.; Snyder, John S.; Goebel, Dan M.; Katz, Ira; Herman, Daniel A.

2009-01-01

The fidelity of electric propulsion physics-based models depends largely on the validity of their predictions over a range of operating conditions and geometries. In general, increased complexity of the physics requires more extensive comparisons with laboratory data to identify the region(s) that lie outside the validity of the model assumptions and to quantify the uncertainties within its range of application. This paper presents numerical simulations of neutralizer hollow cathodes at various operating conditions and orifice sizes. The simulations were performed using a two-dimensional axisymmetric model that solves numerically a relatively extensive system of conservation laws for the partially ionized gas in these devices. A summary of the comparisons between simulation results and Langmuir probe measurements is provided. The model has also been employed to provide insight into recent ground test observations of the neutralizer cathode in NEXT. It is found that a likely cause of the observed keeper voltage drop is cathode orifice erosion. However, due to the small magnitude of this change, is approx. 0.5 V (less than 5% of the beginning-of-life value) over 10 khrs, and in light of the large uncertainties of the cathode material sputtering yield at low ion energies, other causes cannot be excluded. Preliminary simulations to understand transition to plume mode suggest that in the range of 3-5 sccm the existing 2-D model reproduces fairly well the rise of the keeper voltage in the NEXT neutralizer as observed in the laboratory. At lower flow rates the simulation produces oscillations in the keeper current and voltage that require prohibitively small time-steps to resolve with the existing algorithms.

Three-colour photoionization optogalvanic spectroscopy in U-Ne hollow cathode discharges: observation of even-parity autoionization states of uranium

International Nuclear Information System (INIS)

Mandal, P.K.; Seema, A.U.; Das, R.C.; Shah, M.L.; Dev, Vas; Suri, B.M.

2013-01-01

Three-colour three-step photoionization spectroscopy of uranium has been performed in a U-Ne hollow cathode discharge tube by temporally resolving three-colour photoionization optogalvanic (PIOG) signal from the normal optogalvanic (OG) signal using three tunable pulsed dye lasers. U-Ne hollow cathode discharge tube has been used as a source of uranium atomic vapour and photoionization detector. Using this technique, photoionization spectra of uranium have been investigated systematically in the energy region 52150-52590 cm -1 , through three different excitation pathways, originating from its ground state, 0 cm -1 ( 5 L 0 6 ). By analyzing the three-colour photoionization spectra sixty new even-parity autoionization resonances of uranium have been identified and their probable total angular momentum (J) values have been assigned according to the J-momentum selection rule. (author)

Building Honeycomb-Like Hollow Microsphere Architecture in a Bubble Template Reaction for High-Performance Lithium-Rich Layered Oxide Cathode Materials.

Science.gov (United States)

Chen, Zhaoyong; Yan, Xiaoyan; Xu, Ming; Cao, Kaifeng; Zhu, Huali; Li, Lingjun; Duan, Junfei

2017-09-13

In the family of high-performance cathode materials for lithium-ion batteries, lithium-rich layered oxides come out in front because of a high reversible capacity exceeding 250 mAh g -1 . However, the long-term energy retention and high energy densities for lithium-rich layered oxide cathode materials require a stable structure with large surface areas. Here we propose a "bubble template" reaction to build "honeycomb-like" hollow microsphere architecture for a Li 1.2 Mn 0.52 Ni 0.2 Co 0.08 O 2 cathode material. Our material is designed with ca. 8-μm-sized secondary particles with hollow and highly exposed porous structures that promise a large flexible volume to achieve superior structure stability and high rate capability. Our preliminary electrochemical experiments show a high capacity of 287 mAh g -1 at 0.1 C and a capacity retention of 96% after 100 cycles at 1.0 C. Furthermore, the rate capability is superior without any other modifications, reaching 197 mAh g -1 at 3.0 C with a capacity retention of 94% after 100 cycles. This approach may shed light on a new material engineering for high-performance cathode materials.

Plasma-induced field emission study of carbon nanotube cathode

Directory of Open Access Journals (Sweden)

Yi Shen

2011-10-01

Full Text Available An investigation on the plasma-induced field emission (PFE properties of a large area carbon nanotube (CNT cathode on a 2 MeV linear induction accelerator injector is presented. Experimental results show that the cathode is able to emit intense electron beams. Intense electron beams of 14.9–127.8  A/cm^{2} are obtained from the cathode. The CNT cathode desorbs gases from the CNTs during the PFE process. The fast cathode plasma expansion affects the diode perveance. The amount of outgassing is estimated to be 0.06–0.49  Pa·L, and the ratio of outgassing and electron are roughly calculated to be within the range of 170–350 atoms per electron. The effect of the outgassing is analyzed, and the outgassing mass spectrum of the CNT cathode has been studied during the PFE. There is a significant desorption of CO_{2}, N_{2}(CO, and H_{2} gases, which plays an important role during the PFE process. All the experiments demonstrate that the outgassing plays an important role in the formation of the cathode plasma. Moreover, the characteristic turn-on time of the CNT cathode was measured to be 39 ns.

Evolution of transverse instability in a hollow cylindrical weakly-ionized plasma column

International Nuclear Information System (INIS)

Kuedyan, H.M.

1978-01-01

Having observed formation of plasma striations in an Electron Cyclotron Resonance Heating (ECRH) device, we have studied the conditions under which the hollow cylindrical plasma columns would develop into striations. We first present the observed conditions of the hollow cylindrical plasma which would develop into plasma striations, the measured characteristics of the transverse oscillations and a simple small signal model for a transverse instability in a weakly-ionized hollow cylindrical plasma. This linearized model, which assumes flowing cold ion fluid (T/sub i/ approximately < 0.1 eV) in warm electron fluid (T/sub e/ approximately 1 eV) and background neutrals, reveals a transverse flute-type electrostatic instability whose characteristics are in qualitative and quantitative agreement with the measured values of the oscillations in our experiment

Investigation of modified thin SnO2 layers treated by rapid thermal annealing by means of hollow cathode spectroscopy and AFM technique

International Nuclear Information System (INIS)

Djulgerova, R; Popova, L; Beshkov, G; Petrovic, Z Lju; Rakocevic, Z; Mihailov, V; Gencheva, V; Dohnalik, T

2006-01-01

By means of hollow cathode spectroscopy and atomic force microscopy the surface morphology and composition of SnO 2 thin film, modified with hexamethyldisilazane after rapid thermal annealing treatment (800-1200 deg. C), are investigated. Formation of crystalline structure is suggested at lower temperatures. Depolimerization, destruction and dehydration are developed at temperatures of 1200 deg. C. It is shown that the rapid thermal annealing treatment could modify both the surface morphology and the composition of the layer, thus changing the adsorption ability of the sensing layer. The results confirm the ability of hollow cathode emission spectroscopy for depth profiling of new materials especially combined with standard techniques

Coronal and local thermodynamic equilibriums in a hollow cathode discharge

International Nuclear Information System (INIS)

Zheng Xutao

2005-01-01

A characteristic two-section profile of excited-state populations is observed in a hollow cathode discharge and is explained by coexistence of the coronal equilibrium (CE) and the local thermodynamic equilibrium (LTE). At helium pressure 0.1 Torr and cathode current 200-300 mA, vacuum ultraviolet radiations from He I 1snp 1 P (n=2-16) and He II np 2 P (n=2-14) are resolved with a 2.2-M McPherson spectrometer. Relative populations of these states are deduced from the discrete line intensities and are plotted against energy levels. For both the He I and He II series, as energy level increases, populations of high-n (n>10) states are found to decrease much more quickly than low-n (n<7) populations. While low-n populations are described with the CE dominated by direct electron-impact excitations, high-n populations are fitted with the LTE to calculate the population temperatures of gas atoms and ions. Validities of the CE and LTE in different n-ranges are considered on the competition between radiative decays of the excited states and their collisions with gas atoms. (author)

Laser absorption spectroscopy for measurement of He metastable atoms of a microhollow cathode plasma

Science.gov (United States)

Ueno, Keisuke; Kamebuchi, Kenta; Kakutani, Jiro; Matsuoka, Leo; Namba, Shinichi; Fujii, Keisuke; Shikama, Taiichi; Hasuo, Masahiro

2018-01-01

We generated a 0.3-mm-diameter DC, hollow-cathode helium discharge in a gas pressure range of 10-80 kPa. In discharge plasmas, we measured position-dependent laser absorption spectra for helium 23S1-23P0 transition with a spatial resolution of 55 µm. From the results of the analysis of the measured spectra using Voigt functions and including both the Doppler and collision broadening, we produced two-dimensional maps of the metastable 23S1 atomic densities and gas temperatures of the plasmas. We found that, at all pressures, the gas temperatures were approximately uniform in space with values in the range of 400-1500 K and the 23S1 atomic densities were ˜1019 m-3. We also found that the two-dimensional density distribution profiles became ring-shaped at high gas pressures, which is qualitatively consistent with the two-dimensional fluid simulation results.

Optogalvanic detection of the Zeeman effect in a hollow-cathode discharge

International Nuclear Information System (INIS)

Langlois, E.; Gagne, J.

1987-01-01

Optogalvanic detection of complex Zeeman patterns in a hollow-cathode lamp is investigated. Uranium lines with J 1 = 6 and J 2 = 7 are resolved, with our best results obtained using intermodulate optogalvanic spectroscopy (but this scheme is applicable only to lines giving strong signals). This detection method has a 40-MHz resolution, so a magnetic field of 0.1 T is sufficient to resolve most patterns. Weak lines can be studied with modulated optogalvanic spectroscopy. However, the stronger field required in this case perturbs the discharge. Although they are impractical for the measurement of component relative intensities, these detection methods may find applications in the determination of Lande g factors

Heat input properties of hollow cathode arc as a welding heat source

International Nuclear Information System (INIS)

Nishikawa, Hiroshi; Shobako, Shinichiro; Ohta, Masashi; Ohji, Takayoshi

2005-01-01

In order to clarify whether a hollow cathode arc (HCA) can be used as a welding heat source in space, investigations into the fundamental characteristics of HCA were experimentally performed under low pressure conditions. The HCA method enables an arc discharge to ignite and maintain under low pressure conditions; in contrast, low pressure conditions make it extremely difficult for the conventional gas tungsten arc method to form an arc discharge. In an earlier paper, it was shown that the melting process by HCA is very sensitive to process parameters such as the gas flow rate and arc length, and a deep penetration forms when the arc length is long and the gas flow rate is low. In this paper, the distribution of the arc current on the anode surface and the plasma properties of the HCA under low pressure conditions have been made clear and the total heat energy to the anode has been discussed in order to understand the heat input properties of the HCA. The result shows that the HCA in the case of a low gas flow rate is a high and concentrated energy source, and the high energy input to the anode contributes to the deep penetration

Ion plasma electron gun

International Nuclear Information System (INIS)

Wakalopulos, G.

1976-01-01

In the disclosed electron gun positive ions generated by a hollow cathode plasma discharge in a first chamber are accelerated through control and shield grids into a second chamber containing a high voltage cold cathode. These positive ions bombard a surface of the cathode causing the cathode to emit secondary electrons which form an electron beam having a distribution adjacent to the cathode emissive surface substantially the same as the distribution of the ion beam impinging upon the cathode. After passing through the grids and the plasma discharge chamber, the electron beam exits from the electron gun via a foil window. Control of the generated electron beam is achieved by applying a relatively low control voltage between the control grid and the electron gun housing (which resides at ground potential) to control the density of the positive ions bombarding the cathode

Electron current extraction from a permanent magnet waveguide plasma cathode

Energy Technology Data Exchange (ETDEWEB)

Weatherford, B. R.; Foster, J. E. [University of Michigan, Ann Arbor, Michigan 48109 (United States); Kamhawi, H. [NASA Glenn Research Center, Cleveland, Ohio 44135 (United States)

2011-09-15

An electron cyclotron resonance plasma produced in a cylindrical waveguide with external permanent magnets was investigated as a possible plasma cathode electron source. The configuration is desirable in that it eliminates the need for a physical antenna inserted into the plasma, the erosion of which limits operating lifetime. Plasma bulk density was found to be overdense in the source. Extraction currents over 4 A were achieved with the device. Measurements of extracted electron currents were similar to calculated currents, which were estimated using Langmuir probe measurements at the plasma cathode orifice and along the length of the external plume. The influence of facility effects and trace ionization in the anode-cathode gap are also discussed.

Density of uranium ions in the 4I0/sub 9/2/ ground state in a hollow-cathode type discharge

International Nuclear Information System (INIS)

Pianarosa, P.; Bouchard, P.; Saint-Dizier, J.P.; Gagne, J.M.

1983-01-01

A hollow-cathode type discharge cell as generator of uranium ions is investigated. The 4 I 0 /sub 9/2/ ground-state ion density has been obtained by absorption spectroscopy at 5493 and 4244 A. The absorption measurements have been performed using two identical hollow-cathode lamps: one acting as a light source, the other as a reservoir of free ions. Neon and xenon have been used as discharge sustaining gases. In our experimental conditions the measured ion ground-state density is of the order of 10 12 ions cm -3 . Absorption measurements performed at 5915 and 4246 A of U i give a density of the order of 10 12 atoms cm -3 . This latter value is in excellent agreement with a previously measured value obtained by laser-absorption spectroscopy

Ion source with plasma cathode

International Nuclear Information System (INIS)

Yabe, E.

1987-01-01

A long lifetime ion source with plasma cathode has been developed for use in ion implantation. In this ion source, a plasma of a nonreactive working gas serves as a cathode in place of a thermionic tungsten filament used in the Freeman ion source. In an applied magnetic field, the plasma is convergent, i.e., filamentlike; in zero magnetic field, it turns divergent and spraylike. In the latter case, the plasma exhibits a remarkable ability when the working gas has an ionization potential larger than the feed gas. By any combination of a working gas of either argon or neon and a feed gas of AsF 5 or PF 5 , the lifetime of this ion source was found to be more than 90 h with an extraction voltage of 40 kV and the corresponding ion current density 20 mA/cm 2 . Mass spectrometry results show that this ion source has an ability of generating a considerable amount of As + and P + ions from AsF 5 and PF 5 , and hence will be useful for realizing a fully cryopumped ion implanter system. This ion source is also eminently suitable for use in oxygen ion production

Turbulence and transport in a magnetized argon plasma

International Nuclear Information System (INIS)

Pots, B.F.M.

1979-01-01

An experimental study on turbulence and transport in the highly ionized argon plasma of a hollow cathode discharge is described. In order to determine the plasma parameters three standard diagnostics have been used, whilst two diagnostics have been developed to study the plasma turbulence. (Auth.)

An ingenious design of lamellar Li1.2Mn0.54Ni0.13Co0.13O2 hollow nanosphere cathode for advanced lithium-ion batteries

International Nuclear Information System (INIS)

Zhang, Yao; Zhang, Wansen; Shen, Shuiyun; Yan, Xiaohui; Wu, Aiming; Wu, Ruofei; Zhang, Junliang

2017-01-01

Highlights: •Lamellar Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 hollow nanospheres serve as a cathode for LIBs. •Unique lamella and hollow structures benefit the enhanced electrochemical performance. •Lamellar shells can provide a short lithium-ion diffusion pathway. •The sufficient void space can accommodate volumetric expansion and contraction. -- Abstract: Although very appealing in developing hollow structured lithium-rich layered transition-metal oxides as cathodes for lithium-ion batteries (LIBs), a great challenge lies in controlling the growth of transition metal elements with desired molar ratios while maintaining intact hollow structures during synthesis. Herein, we propose a scalable strategy to successfully synthesize novel lamellar Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 hollow (L-LMOH) nanosphere cathode for advanced lithium-ion batteries (LIBs). It is proved that the employment of sulfonated polystyrene (SPS) gel nanospheres as the template plays a key role in the formation of flower-like SPS@ Ni-Co-Mn-precursor nanospheres with desired molar ratios, and a subsequently delicate control in the heating rate leads to the intact L-LMOH nanospheres. It is demonstrated that the use of L-LMOH nanosphere cathode not only delivers outstanding reversible discharge capacities of 281.7 mAh g −1 at a current density of 20 mA g −1 and 136.6 mAh g −1 at 2000 mA g −1 , but also possess superior cycling stability with a capacity reservation of 80% at 2000 mA g −1 after 200 continuous cycles. It is well analyzed that the ingenious design of both unique lamella and hollow architectures synergistically benefits the significantly enhanced rate capability and cycling stability.

Use of a discharge in an hollow cathode as neutral atom source for resonant ionization mass spectrometry

International Nuclear Information System (INIS)

Berthoud, T.; Briand, A.; Khelifa, N.; Mauchien, P.

1987-01-01

The resonance ionization mass spectrometry in our laboratory is aimed at simplification of isotope measurements of elements present in mixtures and at measurement of very small isotopes. An atomization source which produces an atomic beam collimated from a discharge in a hollow cathode has been developed. First results of this spectrometry with an uranium atomic jet are presented [fr

On the energy deposition into the plasma for an inverted fireball geometry

Science.gov (United States)

Levko, Dmitry; Gruenwald, Johannes

2017-10-01

Energy deposition into a plasma for an inverted fireball geometry is studied using a self-consistent two-dimensional Particle-in-Cell Monte Carlo collision model. In this model, the cathode is a pin which injects the fixed electron current and the anode is a hollow metal tube covered with the metal grid. We obtain an almost constant ratio between the densities of plasmas generated in the cathode-grid gap and inside the hollow anode. The results of the simulations show that there is no energy exchange between the beam and plasma electrons at low emission currents. For increasing current, however, we observe the increasing coupling between the electron beam and the thermal plasma electrons. This leads to the heating of plasma electrons and the generation of the so-called supra-thermal electrons.

Hierarchical nanostructured hollow spherical carbon with mesoporous shell as a unique cathode catalyst support in proton exchange membrane fuel cell.

Science.gov (United States)

Fang, Baizeng; Kim, Jung Ho; Kim, Minsik; Kim, Minwoo; Yu, Jong-Sung

2009-03-07

Hierarchical nanostructured spherical carbon with hollow macroporous core in combination with mesoporous shell has been explored to support Pt cathode catalyst with high metal loading in proton exchange membrane fuel cell (PEMFC). The hollow core-mesoporous shell carbon (HCMSC) has unique structural characteristics such as large specific surface area and mesoporous volume, ensuring uniform dispersion of the supported high loading (60 wt%) Pt nanoparticles with small particle size, and well-developed three-dimensionally interconnected hierarchical porosity network, facilitating fast mass transport. The HCMSC-supported Pt(60 wt%) cathode catalyst has demonstrated markedly enhanced catalytic activity toward oxygen reduction and greatly improved PEMFC polarization performance compared with carbon black Vulcan XC-72 (VC)-supported ones. Furthermore, the HCMSC-supported Pt(40 wt%) or Pt(60 wt%) outperforms the HCMSC-supported Pt(20 wt%) even at a low catalyst loading of 0.2 mg Pt cm(-2) in the cathode, which is completely different from the VC-supported Pt catalysts. The capability of supporting high loading Pt is supposed to accelerate the commercialization of PEMFC due to the anticipated significant reduction in the amount of catalyst support required, diffusion layer thickness and fabricating cost of the supported Pt catalyst electrode.

Simulative research on the expansion of cathode plasma in high-current electron beam diode

International Nuclear Information System (INIS)

Xu Qifu; Liu Lie

2012-01-01

The expansion of cathode plasma has long been recognized as a limiting factor in the impedance lifetime of high-current electron beam diode. Realistic modeling of such plasma is of great necessity in order to discuss the dynamics of cathode plasma. Using the method of particle-in-cell, the expansion of cathode plasma is simulated in this paper by a scaled-down diode model. It is found that the formation of cathode plasma increases the current density in the diode. This consequently leads to the decrease of the potential at plasma front. Once the current density has been increased to a certain value, the potential at plasma front would then be equal to or lower than the plasma potential. Then the ions would move towards the anode, and the expansion of cathode plasma is thereby formed. Different factors affecting the plasma expansion velocity are discussed in this paper. It is shown that the decrease of proton genatation rate has the benefit of reducing the plasma expansion velocity.

Doppler spectroscopy of hydrogen Balmer lines in a hollow cathode glow discharge in ammonia and argon-ammonia mixture

International Nuclear Information System (INIS)

Sisovic, N. M.; Konjevic, N.

2008-01-01

The results of Doppler spectroscopy of hydrogen Balmer lines from a stainless steel (SS) and copper (Cu) hollow cathode (HC) glow discharge in ammonia and argon-ammonia mixture are reported. The experimental profiles in ammonia discharge are fitted well by superposing three Gaussian profiles. The half widths, in energy units, of narrow and medium Gaussians are in the ranges 0.3-0.4 eV and 3-4 eV, respectively, for both hollow cathodes what is expected on the basis of earlier electron beam→NH 3 experiments. The half widths of the largest Gaussian in ammonia are 46 and 55 eV for SS and Cu HC, respectively. In argon-ammonia discharge, three Gaussians are also required to fit experimental profiles. While half widths of narrow and medium Gaussians are similar to those in ammonia, the half widths of the largest Gaussians are 35 and 42 eV for SS and Cu HC, respectively. The half widths of the largest Gaussians in ammonia and in argon-ammonia mixture indicate the presence of excessive Doppler broadening.

Efficient small molecular organic light emitting diode with graphene cathode covered by a Sm layer with nano-hollows and n-doped by Bphen:Cs2CO3 in the hollows

Science.gov (United States)

Yao, Li; Li, Lei; Qin, Laixiang; Ma, Yaoguang; Wang, Wei; Meng, Hu; Jin, Weifeng; Wang, Yilun; Xu, Wanjin; Ran, Guangzhao; You, Liping; Qin, Guogang

2017-03-01

Graphene is a favorable candidate for electrodes of organic light emitting diodes (OLEDs). Graphene has quite a high work function of ˜4.5 eV, and has been extensively studied when used as anodes of OLEDs. In order to use graphene as a cathode, the electron injection barrier between the graphene cathode and the electron transport layer has to be low enough. Using 4,7-diphenyl-1,10-phenanthroline (Bphen):Cs2CO3 to n-dope graphene is a very good method, but the electron injection barrier between the n-doped graphene and Bphen:Cs2CO3 is still too high to be ˜1.0 eV. In this work, in order to further reduce the electron injection barrier, a novel method is suggested. On the graphene cathode, a Sm layer with a lot of nano-hollows, and subsequently a layer of Bphen:Cs2CO3, are deposited. The Bphen:Cs2CO3 can n-dope graphene in the nano-hollows, and the Fermi level of the graphene rises. The nano Sm layer is very easily oxidized. Oxygen adsorbed on the surface of graphene may react with Sm to form an O--Sm+ dipole layer. On the areas of the Sm oxide dipole layer without nano-hollows, the electron injection barrier can be further lowered by the dipole layer. Electrons tend to mainly inject through the lower electron barrier where the dipole layer exists. Based on this idea, an effective inverted small molecular OLED with the structure of graphene/1 nm Sm layer with a lot of nano-hollows/Bphen:Cs2CO3/Alq3:C545T/NPB/MoO3/Al is presented. The maximum current efficiency and maximum power efficiency of the OLED with a 1 nm Sm layer are about two and three times of those of the reference OLED without any Sm layer, respectively.

Wave and transport studies utilizing dense plasma filaments generated with a lanthanum hexaboride cathode

International Nuclear Information System (INIS)

Van Compernolle, B.; Gekelman, W.; Pribyl, P.; Cooper, C. M.

2011-01-01

A portable lanthanum hexaboride (LaB 6 ) cathode has been developed for use in the LArge Plasma Device (LAPD) at UCLA. The LaB 6 cathode can be used as a tool for many different studies in experimental plasma physics. To date, the cathode has been used as a source of a plasma with a hot dense core for transport studies and diagnostics development, as a source of gradient driven modes, as a source of shear Alfven waves, and as a source of interacting current channels in reconnection experiments. The LaB 6 cathode is capable of higher discharge current densities than the main barium oxide coated LAPD cathode and is therefore able to produce plasmas of higher densities and higher electron temperatures. The 8.25 cm diameter cathode can be introduced into the LAPD at different axial locations without the need to break vacuum. The cathode can be scaled up or down for use as a portable secondary plasma source in other machines.

The spatial structure of cathode plasma jets in a vacuum arc

International Nuclear Information System (INIS)

Krinberg, I.A.; Zverev, E.A.

1999-01-01

It is shown that, in cathode plasma jets of a vacuum arc with an interelectrode gap of up to 1 m and a current of 10 2 -10 3 A, there exist three characteristic regions with different ratios β of the plasma pressure to the magnetic field pressure. The plasma emitted from cathode microspots, in the form of microjets, is heated and accelerated predominantly in the region near the cathode (z -2 ), in which β≅10 2 -10 3 . After the microjets merge into one jet, the plasma in the region z≅0.03-3 cm begins to move toward the jet axis because of the compression of the jet by its own magnetic field (β<1). Just before the compression reaches its maximum, the density, temperature, and potential sharply increase, and the compression comes to an end. In the region z≥3 cm, the cathode plasma jet looks like a paraboloid of revolution, whose surface oscillates about the equilibrium position (β≅1), which causes the density, temperature, and potential to oscillate in a similar fashion

Diode with plasma cathode on the basis of a sliding discharge

International Nuclear Information System (INIS)

Korenev, S.A.

1982-01-01

The operative regime of a diode with plasma cathode on the basis of a discharge sliding over the surface of dielectric without an additional switching - on discharge generator at the glance of capacity couplings of anode and cathode assemblies is described. It is experimentally shown that at the voltage at the diode of about 150-300 kV electron beams with the 400-1000 A/cm current density can be formed. The velocity of cathode plasma motion in the direction of anode for different materials of dielctric insertion in a cathode assembly amounts to (1.5-10)x10 5 cm/s

Acoustic emission by self-organising effects of micro-hollow cathode discharges

Science.gov (United States)

Kotschate, Daniel; Gaal, Mate; Kersten, Holger

2018-04-01

We designed micro-hollow cathode discharge prototypes under atmospheric pressure and investigated their acoustic characteristics. For the acoustic model of the discharge, we correlated the self-organisation effect of the current density distribution with the ideal model of an acoustic membrane. For validation of the obtained model, sound particle velocity spectroscopy was used to detect and analyse the acoustic emission experimentally. The results have shown a behaviour similar to the ideal acoustic membrane. Therefore, the acoustic excitation is decomposable into its eigenfrequencies and predictable. The model was unified utilising the gas exhaust velocity caused by the electrohydrodynamic force. The results may allow a contactless prediction of the current density distribution by measuring the acoustic emission or using the micro-discharge as a tunable acoustic source for specific applications as well.

Simple method for identifying doubly ionized uranium (U III) produced in a hollow-cathode discharge

International Nuclear Information System (INIS)

Piyakis, K.N.; Gagne, J.M.

1988-01-01

We have studied by emission spectroscopy the spectral properties of doubly ionized uranium, produced in a vapor generator of hollow-cathode design, as a function of the nature of a pure fill gas (helium, neon, argon, krypton, xenon) and its pressure. The spectral intensity is found to increase with increasing ionization potential of the discharge buffer gas, except in the case of helium. Based on our preliminary results, a simple and practical method for the positive identification of the complex U III spectrum is suggested

Study on the cathode of ion source for neutral beam injector

International Nuclear Information System (INIS)

Tanaka, Shigeru

1983-08-01

Durability of the cathode is an important problem in developing a high power long pulse ion source for neutral beam injector. The Purpose of this study is to develope a long life cathode and investigate the applicability of it to the source. Directly heated filaments which are commonly used as the cathode of injector source do not live very long in general. In the present work, an indirectly heated hollow cathode made of impregnated porous tungsten tube is proposed as the alternative of the directly heated cathode. At first, we fabricated a small hollow cathode to study the discharge characteristcs in a bell-jar configuration and to apply it to a duoPIGatron hydrogen ion source. The experiment showed that the gas flow rate for sustaining the stable arc discharge in the discharge chamber becomes higher than that when the filament cathode is used. To solve this problem, an experiment for gas reduction was made using a newly fabricated larger hollow cathode and a magnetic multi-pole ion source. The influence of the orifice diameter, the effect of a button and of magnetic field on the gas flow rate were experimentally studied and a method for gas reduction was found. In addition, effect of the magnetic field on the characteristics of the hollow cathode ion source was examined in detail and an optimum field configuration around the cathode was found. Finally, beam extraction from an intensively cooled hollow cathode ion source for up to 10 sec was successfully carried out. (author)

Characterization of hollow cathode fall field strength measured by Doppler-free two-photon optogalvanic spectroscopy via Stark splitting of the 2S level of hydrogen and deuterium

Energy Technology Data Exchange (ETDEWEB)

Perez, C; De la Rosa, M I; Gruetzmacher, K, E-mail: concha@opt.uva.e [Universidad de Valladolid, Facultad de Ciencias, 47071 Valladolid (Spain)

2010-05-01

Doppler-free two-photon optogalvanic spectroscopy has been applied to measure the strong electric field strength and the cathode fall characteristics of hollow cathode discharges operated in hydrogen and deuterium via the Stark splitting of the 2S level of atomic hydrogen isotopes. In this paper we show similarities and differences in the tendencies of the cathode fall characteristics of hydrogen and deuterium in a wide range of identical discharge parameters.

Characterization of hollow cathode fall field strength measured by Doppler-free two-photon optogalvanic spectroscopy via Stark splitting of the 2S level of hydrogen and deuterium

International Nuclear Information System (INIS)

Perez, C; De la Rosa, M I; Gruetzmacher, K

2010-01-01

Doppler-free two-photon optogalvanic spectroscopy has been applied to measure the strong electric field strength and the cathode fall characteristics of hollow cathode discharges operated in hydrogen and deuterium via the Stark splitting of the 2S level of atomic hydrogen isotopes. In this paper we show similarities and differences in the tendencies of the cathode fall characteristics of hydrogen and deuterium in a wide range of identical discharge parameters.

Characterization of an atom beam produced with the help of a hollow-cathode discharge

International Nuclear Information System (INIS)

Babin, F.; Gagne, J.

1986-01-01

A hollow-cathode type discharge is used as a refractory element vapor generator for the formation of an atomic beam. The development of the technique brings us to discuss its possibilities in spectroscopic studies of refractory elements. We focus primarily on the production of a uranium atomic beam and its characterization by laser-induced fluorescence spectroscopy. We determine, among other things, the beam divergence and the most probable velocity along its axis for specific current and pressure conditions in the discharge. We also discuss beam behavior with respect to buffer gas pressure and electric current in the discharge

Low-energy plasma-cathode electron gun with a perforated emission electrode

Science.gov (United States)

Burdovitsin, Victor; Kazakov, Andrey; Medovnik, Alexander; Oks, Efim; Tyunkov, Andrey

2017-11-01

We describe research of influence of the geometric parameters of perforated electrode on emission parameters of a plasma cathode electron gun generating continuous electron beams at gas pressure 5-6 Pa. It is shown, that the emission current increases with increasing the hole diameters and decreasing the thickness of the perforated emission electrode. Plasma-cathode gun with perforated electron can provide electron extraction with an efficiency of up to 72 %. It is shown, that the current-voltage characteristic of the electron gun with a perforated emission electrode differs from that of similar guns with fine mesh grid electrode. The plasma-cathode electron gun with perforated emission electrode is used for electron beam welding and sintering.

Resonant and hollow beam generation of plasma channels

International Nuclear Information System (INIS)

Alexeev, I.; Kim, K.Y.; Fan, J.; Parra, E.; Milchberg, H.M.; Margolin, L.Ya.; Pyatnitskii, L.N.

2001-01-01

We report two variations on plasma channel generation using the propagation of intense Bessel beams. In the first experiment, the propagation of a high intensity Bessel beam in neutral gas is observed to give rise to resonantly enhanced plasma channel generation, resulting from resonant self-trapping of the beam and enhanced laser-plasma heating. In the second experiment, a high power, hollow Bessel beam (J 5 ) is produced and the optical breakdown of a gas target and the generation of a tubular plasma channel with such a beam is realized for the first time. Hydrodynamic simulations of the laser-plasma interaction of are in good agreement with the results of both experiments

Study of the use of an electric discharge for hollow cathodes used as optical excitation sources in the spectrographic measurement of fluorine in thorium, uranium and plutonium

International Nuclear Information System (INIS)

Bufpereau, M.; Crehange, G.; Poublan, J.

1964-01-01

Previous works and phenomena concerned with a hollow cathode excitation are reviewed. Experiments aimed specially on the determination of the best conditions for an analysis of fluorine in oxides-metals and solutions. In that purpose, several factors have been pointed out. One started some researches about others elements that fluorine. Carrying fluorine into discharge and excitation have been more specially studied. A quantitative analysis method is given. The analysis limit is 45 ppm about but the detection limit is 5 ppm about. As a conclusion, various ways for optical excitation of fluorine are reviewed as other analytical possibilities a hollow cathode discharge offers. (authors) [fr

Deposition of Composite LSCF-SDC and SSC-SDC Cathodes by Axial-Injection Plasma Spraying

Science.gov (United States)

Harris, Jeffrey; Qureshi, Musab; Kesler, Olivera

2012-06-01

The performance of solid oxide fuel cell cathodes can be improved by increasing the number of electrochemical reaction sites, by controlling microstructures, or by using composite materials that consist of an ionic conductor and a mixed ionic and electronic conductor. LSCF (La0.6Sr0.4Co0.2Fe0.8O3-δ) and SSC (Sm0.5Sr0.5CoO3) cathodes were manufactured by axial-injection atmospheric plasma spraying, and composite cathodes were fabricated by mixing SDC (Ce0.8Sm0.2O1.9) into the feedstock powders. The plasma power was varied by changing the proportion of nitrogen in the plasma gas. The microstructures of cathodes produced with different plasma powers were characterized by scanning electron microscopy and gas permeation measurements. The deposition efficiencies of these cathodes were calculated based on the mass of the sprayed cathode. Particle surface temperatures were measured in-flight to enhance understanding of the relationship between spray parameters, microstructure, and deposition efficiency.

Collaborative Research: Understanding Ion Losses to Plasma Boundaries Sheaths and Presheaths

Energy Technology Data Exchange (ETDEWEB)

Hershkowitz, Noah [Univ. of Wisconsin, Madison, WI (United States)

2015-10-01

Sheaths are common to all bounded steady-state plasmas. This includes laboratory, industrial, fusion, and in some cases even space plasmas. They form in general to balance particle loss and maintain quasi-neutrality in plasmas. Electrons are lighter than the ions by 2000 times or more (depending on the gas), and in most plasmas ion temperatures are rarely higher than the electron temperature and generally much lower. Thus in most cases, negative potential sheaths occur to confine electrons and allow ions to be freely lost. We have investigated how a plasma locally response to a positive bias on a small electrode, and have established area criteria which plasma reacts differently to the positive bias – first a pure electron sheath, and a global non-ambipolar regime where all electrons are lost to the electrode, and a double layer structure identified as a virtual cathode forms to limiting electron loss and maintain quasi-neutrality, and finally a anode spot regime where a secondary discharge occurs in front of the electrode, turning it into the major loss area of the entire plasma. Electrode area and plasma parameters criteria for these regimes were established, and the effect of the virtual cathode on the electrode’s I-V characteristics was investigated. We have also developed a global non-ambipolar electron source to replace hollow cathodes in a number of plasma applications. This eliminates the lifetime limitation and maintenance cost of hollow cathodes as they easily wear out easily and cannot be replaced in space applications.

A new thin film deposition process by cathodic plasma electrolysis

International Nuclear Information System (INIS)

Paulmier, T.; Kiriakos, E.; Bell, J.; Fredericks, P.

2004-01-01

Full text: A new technique, called atmospheric pressure plasma deposition (APPD), has been developed since a few years for the deposition of carbon and DLC, Titanium or Silicon films on metal and metal alloys substrates. A high voltage (2kV) is applied in a liquid electrolytic solution between an anode and a cathode, both electrodes being cylindrical: a glow discharge is then produced and confined at the vicinity of the cathode. The physic of the plasma in the electrolytic solution near the cathode is very different form the other techniques of plasma deposition since the pressure is here close to the atmospheric pressure. We describe here the different physico-chemical processes occurring during the process. In this cathodic process, the anodic area is significantly larger than the cathode area. In a first step, the electrolytic solution is heated by Joule effect induced by the high voltage between the electrodes. Due to the high current density, the vaporization of the solution occurs near the cathode: a large amount of bubbles are produced which are stabilized at the electrode by hydrodynamic and electromagnetic forces, forming a vapour sheath. The electric field and voltage drop are then concentrated in this gas envelope, inducing the ionization of the gas and the ignition of a glow discharge at the surface of the material. This plasma induces the formation of ionized and reactive species which diffuse and are accelerated toward the cathode. These excited species are the precursors for the formation of the deposition material. At the same time, the glow discharge interacts with the electrolyte solution inducing also ionization, convection and polymerization processes in the liquid: the solution is therefore a second source of the deposition material. A wide range of films have been deposited with a thickness up to 10 micrometers. These films have been analyzed by SEM and Raman spectroscopy. The electrolytic solution has been characterized by GC-MS and the

Electron beam produced in a transient hollow cathode discharge: beam electron distribution function, X-ray emission and solid target ablation

International Nuclear Information System (INIS)

Nistor, Magdalena

2000-01-01

This research thesis aims at a better knowledge of phenomena occurring during transient hollow cathode discharges. The author first recalls the characteristics of such a discharge which make it different from conventional pseudo-spark discharges. The objective is to characterise the electron beam produced within the discharge, and the phenomena associated with its interaction with a solid or gaseous target, leading to the production of an X ray or visible radiation. Thus, the author reports the measurement (by magnetic deflection) of the whole time-averaged electronic distribution function. Such a knowledge is essential for a better use of the electron beam in applications such as X-ray source or material ablation. As high repetition frequency pulse X ray sources are very interesting tools, he reports the development and characterisation of Bremsstrahlung X rays during a beam-target interaction. He finally addresses the implementation of a spectroscopic diagnosis for the filamentary plasma and the ablation of a solid target by the beam [fr

Charge-exchange-induced formation of hollow atoms in high-intensity laser-produced plasmas

Energy Technology Data Exchange (ETDEWEB)

Rosmej, F.B. [TU-Darmstadt, Institut fuer Kernphysik, Darmstadt (Germany); Faenov, A.Ya.; Pikuz, T.A.; Magunov, A.I.; Skobelev, I.Yu. [Multicharged Ions Spectra Data Center of VNIIFTRI, Mendeleevo (Russian Federation); Auguste, T.; D' Oliveira, P.; Hulin, S.; Monot, P. [Commissariat a lEnergie Atomique DSM/DRECAM/SPAM, Gif-Sur-Yvette Cedex (France); Andreev, N.E.; Chegotov, M.V.; Veisman, M.E. [High Energy Density Research Centre, Institute of High Temperatures of Russian Academy of Sciences, Moscow (Russian Federation)

1999-03-14

For the first time registration of high-resolution soft x-ray emission and atomic data calculations of hollow-atom dielectronic satellite spectra of highly charged nitrogen have been performed. Double-electron charge-exchange processes from excited states are proposed for the formation of autoionizing levels nln'l' in high-intensity laser-produced plasmas, when field-ionized ions penetrate into the residual gas. Good agreement is found between theory and experiment. Plasma spectroscopy with hollow ions is proposed and a temperature diagnostic for laser-produced plasmas in the long-lasting recombining regime is developed. (author). Letter-to-the-editor.

A high-current pulsed cathodic vacuum arc plasma source

International Nuclear Information System (INIS)

Oates, T.W.H.; Pigott, J.; Mckenzie, D.R.; Bilek, M.M.M.

2003-01-01

Cathodic vacuum arcs (CVAs) are well established as a method for producing metal plasmas for thin film deposition and as a source of metal ions. Fundamental differences exist between direct current (dc) and pulsed CVAs. We present here results of our investigations into the design and construction of a high-current center-triggered pulsed CVA. Power supply design based on electrolytic capacitors is discussed and optimized based on obtaining the most effective utilization of the cathode material. Anode configuration is also discussed with respect to the optimization of the electron collection capability. Type I and II cathode spots are observed and discussed with respect to cathode surface contamination. An unfiltered deposition rate of 1.7 nm per pulse, at a distance of 100 mm from the source, has been demonstrated. Instantaneous plasma densities in excess of 1x10 19 m -3 are observed after magnetic filtering. Time averaged densities an order of magnitude greater than common dc arc densities have been demonstrated, limited by pulse repetition rate and filter efficiency

Construction and characterization of a hollow cathode tube for high sensibility laser spectroscopy

International Nuclear Information System (INIS)

Morage, A.; Motta, C.C.

1998-01-01

A new hollow cathode tube argon-iron design was developed to be used in laser atomic spectroscopy experiments, were high sensibility is required. This tube was employed in order to allow laser absorption and optogalvanic signal measurements. The tube also included fused-quartz Brewster angle windows aligned with the optical axis in each ending of the tube. Therefore, in this configuration a minimum laser intensity losses through the windows can be attained for the appropriate light polarization. The optogalvanic signal detection was accomplished using a tunable dye laser resonant with the Ar, 3p 5 4p ( 3 S 1 )--> 3p 5 4d ( 3 D 1 0 ) transition, that corresponds to 591.2 nm in air. It was also possible to determine the gas temperature by measuring the Doppler line broadening and the results were compared to those obtained from a theoretical model for gas heat conduction. To measure the temperature of the cathode external surface a thermocouple was used inside the tube. The analysis of results showed that a high signal to noise ratio can be obtained with this tube configuration, that permits experimental investigation of electronic transitions presenting low light absorption cross sections. (author)

Investigation of plasma potential and pulsed discharge characteristics in enhanced glow discharge plasma immersion ion implantation and deposition

International Nuclear Information System (INIS)

Li Liuhe; Lu Qiuyuan; Fu, Ricky K.Y.; Chu, Paul K.

2009-01-01

Enhanced glow discharge plasma immersion ion implantation and deposition (EGD-PII and D) does not require external plasma sources. In this technique, the plasma is produced by self-glow discharge when a high negative voltage is applied to the sample. The small-area, pointed-shape hollow anode and large area tabular cathode form an electron-focused electric field. Using a special electric field design, the electrons from either the plasma or target (secondary electrons) are focused to a special hollow anode. As a result of the special electron-focusing field, the self-glow discharge process can be enhanced to achieve effective ion implantation into the substrate. In this work, the plasma potential distribution is investigated in details and the possible pulse discharge mechanism is discussed. The unique characteristics of the pulsed plasma and plasma extinction are studied.

Erosion behavior of composite Al-Cr cathodes in cathodic arc plasmas in inert and reactive atmospheres

Energy Technology Data Exchange (ETDEWEB)

Franz, Robert, E-mail: robert.franz@unileoben.ac.at; Mendez Martin, Francisca; Hawranek, Gerhard [Montanuniversität Leoben, Franz-Josef-Strasse 18, 8700 Leoben (Austria); Polcik, Peter [Plansee Composite Materials GmbH, Siebenbürgerstrasse 23, 86983 Lechbruck am See (Germany)

2016-03-15

Al{sub x}Cr{sub 1−x} composite cathodes with Al contents of x = 0.75, 0.5, and 0.25 were exposed to cathodic arc plasmas in Ar, N{sub 2}, and O{sub 2} atmospheres and their erosion behavior was studied. Cross-sectional analysis of the elemental distribution of the near-surface zone in the cathodes by scanning electron microscopy revealed the formation of a modified layer for all cathodes and atmospheres. Due to intermixing of Al and Cr in the heat-affected zone, intermetallic Al-Cr phases formed as evidenced by x-ray diffraction analysis. Cathode poisoning effects in the reactive N{sub 2} and O{sub 2} atmospheres were nonuniform as a result of the applied magnetic field configuration. With the exception of oxide islands on Al-rich cathodes, reactive layers were absent in the circular erosion zone, while nitrides and oxides formed in the less eroded center region of the cathodes.

Plasma-induced evolution behavior of space-charge-limited current for multiple-needle cathodes

International Nuclear Information System (INIS)

Li Limin; Liu Lie; Zhang Jun; Wen Jianchun; Liu Yonggui; Wan Hong

2009-01-01

Properties of the plasma and beam flow produced by tufted carbon fiber cathodes in a diode powered by a ∼500 kV, ∼400 ns pulse are investigated. Under electric fields of 230-260 kV cm -1 , the electron current density was in the range 210-280 A cm -2 , and particularly at the diode gap of 20 mm, a maximum beam power density of about 120 MW cm -2 was obtained. It was found that space-charge-limited current exhibited an evolution behavior as the accelerating pulse proceeded. There exists a direct relation between the movement of plasma within the diode and the evolution of space-charge-limited current. Initially in the accelerating pulse, the application of strong electric fields caused the emission sites to explode, forming cathode flares or plasma spots, and in this stage the space-charge-limited current was approximately described by a multiple-needle cathode model. As the pulse proceeded, these plasma spots merged and expanded towards the anode, thus increasing the emission area and shortening the diode gap, and the corresponding space-charge-limited current followed a planar cathode model. Finally, the space-charge-limited current is developed from a unipolar flow into a bipolar flow as a result of the appearance of anode plasma. In spite of the nonuniform distribution of cathode plasma, the cross-sectional uniformity of the extracted electron beam is satisfactory. The plasma expansion within the diode is found to be a major factor in the diode perveance growth and instability. These results show that these types of cathodes can offer promising applications for high-power microwave tubes.

Ion acceleration in multi-species cathodic plasma jet

Science.gov (United States)

Krasov, V. I.; Paperny, V. L.

2016-05-01

A general expression for ion-ion coupling in a multi-species plasma jet was obtained. The expression is valid for any value of the inter-species velocity. This expression has enabled us to review a hydrodynamic problem of expanding the cathodic plasma microjet with two ion species within the respective charge states Z1 = +1 and Z2 = +2 into a vacuum. We were able to illustrate that in scenario when the initial (i.e., acquired during a process of emission from cathode's surface) difference for ion's species velocity exceeds a threshold value, the difference remains noticeable (roughly about 10% of the average jet's velocity) at a distance of a few centimeters from the emission center. At this point, it can be measured experimentally.

Effect of plasma formation on electron pinching and microwave emission in a virtual cathode oscillator

International Nuclear Information System (INIS)

Yatsuzuka, M.; Nakayama, M.; Nobuhara, S.; Young, D.; Ishihara, O.

1996-01-01

Time and spatial evolutions of anode and cathode plasmas in a vircator diode were observed with a streak camera. A cathode plasma appeared immediately after the rise of a beam current and was followed by an anode plasma typically after about 30 ns. Both plasmas expanded with almost the same speed of order of 104 m/s. The anode plasma was confirmed as a hydrogen plasma with an optical filter for H β line and study of anode-temperature rise. Electron beam pinching immediately followed by microwave emission was observed at the beam current less than the critical current for diode pinching in the experiment and the simulation. The electron beam current in the diode region is well characterized by the electron space-charge-limited current in bipolar flow with the expanding plasmas between the anode-cathode gap. As a result, electron bombardment produced the anode plasma, which made the electron beam strongly pinched, resulting in virtual cathode formation and microwave emission. (author). 5 figs., 5 refs

Numerical study on discharge process of microcavity plasma

International Nuclear Information System (INIS)

Xia Guangqing; Xue Weihua; Wang Dongxue; Zhu Guoqiang; Zhu Yu

2012-01-01

The evolution of plasma parameters during high pressure discharge in the microcavity with a hollow anode was numerically studied, with a two-dimensional self-consistent fluid model. The simulations were performed with argon at 13.3 kPa. The numerical results show that during the discharge the electric field around the cathode transforms from an axial field to a radial field, the plasma density gets the maximum value on the central line of the cavity and the location of the maximum density moves from the region near anode at the initial stage to the cathode vicinity at the stable stage, and the maximum electron temperature occurs in the ring sheath of cathode. (authors)

Ion acceleration in multi-species cathodic plasma jet

International Nuclear Information System (INIS)

Krasov, V. I.; Paperny, V. L.

2016-01-01

A general expression for ion-ion coupling in a multi-species plasma jet was obtained. The expression is valid for any value of the inter-species velocity. This expression has enabled us to review a hydrodynamic problem of expanding the cathodic plasma microjet with two ion species within the respective charge states Z 1  = +1 and Z 2  = +2 into a vacuum. We were able to illustrate that in scenario when the initial (i.e., acquired during a process of emission from cathode's surface) difference for ion's species velocity exceeds a threshold value, the difference remains noticeable (roughly about 10% of the average jet's velocity) at a distance of a few centimeters from the emission center. At this point, it can be measured experimentally.

Effect of plasma formation on electron pinching and microwave emission in a virtual cathode oscillator

Energy Technology Data Exchange (ETDEWEB)

Yatsuzuka, M; Nakayama, M; Nobuhara, S [Himeji Institute of Technology (Japan); Young, D; Ishihara, O [Texas Tech Univ., Lubbock, TX (United States)

1997-12-31

Time and spatial evolutions of anode and cathode plasmas in a vircator diode were observed with a streak camera. A cathode plasma appeared immediately after the rise of a beam current and was followed by an anode plasma typically after about 30 ns. Both plasmas expanded with almost the same speed of order of 104 m/s. The anode plasma was confirmed as a hydrogen plasma with an optical filter for H{sub {beta}} line and study of anode-temperature rise. Electron beam pinching immediately followed by microwave emission was observed at the beam current less than the critical current for diode pinching in the experiment and the simulation. The electron beam current in the diode region is well characterized by the electron space-charge-limited current in bipolar flow with the expanding plasmas between the anode-cathode gap. As a result, electron bombardment produced the anode plasma, which made the electron beam strongly pinched, resulting in virtual cathode formation and microwave emission. (author). 5 figs., 5 refs.

Hollow-anode plasma source for molecular beam epitaxy of gallium nitride

International Nuclear Information System (INIS)

Anders, A.; Newman, N.; Rubin, M.; Dickinson, M.; Jones, E.; Phatak, P.; Gassmann, A.

1996-01-01

GaN films have been grown by molecular beam epitaxy (MBE) using a hollow-anode nitrogen plasma source. The source was developed to minimize defect formation as a result of contamination and ion damage. The hollow-anode discharge is a special form of glow discharge with very small anode area. A positive anode voltage drop of 30 endash 40 V and an increased anode sheath thickness leads to ignition of a relatively dense plasma in front of the anode hole. Driven by the pressure gradient, the open-quote open-quote anode close-quote close-quote plasma forms a bright plasma jet streaming with supersonic velocity towards the substrate. Films of GaN have been grown on (0001) SiC and (0001) Al 2 O 3 at 600 endash 800 degree C. The films were investigated by photoluminescence, cathodoluminescence, x-ray diffraction, Rutherford backscattering, and particle-induced x-ray emission. The film with the highest structural quality had a rocking curve width of 5 arcmin, the lowest reported value for MBE growth to date. copyright 1996 American Institute of Physics

Connection experiments with a hollow cathode ion source and a helium gas jet system for on-line isotope separation

International Nuclear Information System (INIS)

Mazumdar, A.K.; Wagner, H.; Walcher, W.; Lund, T.

1976-01-01

A helium jet system was connected to a hollow cathode ion source. Using fission products the efficiencies of the different steps were measured by β-, X-ray and γ-counting while the mass spectrum and the focussing of the extracted ion beam were observed with a small deflecting magnet. Mean transport efficiencies of 50% through the 12 m capillary were obtained and ion source efficiencies in the percent range for several elements. (Auth.)

Note: Hollow cathode lamp with integral, high optical efficiency isolation valve: A modular vacuum ultraviolet source

International Nuclear Information System (INIS)

Sloan Roberts, F.; Anderson, Scott L.

2013-01-01

The design and operating conditions of a hollow cathode discharge lamp for the generation of vacuum ultraviolet radiation, suitable for ultrahigh vacuum (UHV) application, are described in detail. The design is easily constructed, and modular, allowing it to be adapted to different experimental requirements. A thin isolation valve is built into one of the differential pumping stages, isolating the discharge section from the UHV section, both for vacuum safety and to allow lamp maintenance without venting the UHV chamber. The lamp has been used both for ultraviolet photoelectron spectroscopy of surfaces and as a “soft” photoionization source for gas-phase mass spectrometry

Note: Hollow cathode lamp with integral, high optical efficiency isolation valve: A modular vacuum ultraviolet source

Energy Technology Data Exchange (ETDEWEB)

Sloan Roberts, F.; Anderson, Scott L. [Department of Chemistry, University of Utah, 315 S. 1400 E., Salt Lake City, Utah 84112 (United States)

2013-12-15

The design and operating conditions of a hollow cathode discharge lamp for the generation of vacuum ultraviolet radiation, suitable for ultrahigh vacuum (UHV) application, are described in detail. The design is easily constructed, and modular, allowing it to be adapted to different experimental requirements. A thin isolation valve is built into one of the differential pumping stages, isolating the discharge section from the UHV section, both for vacuum safety and to allow lamp maintenance without venting the UHV chamber. The lamp has been used both for ultraviolet photoelectron spectroscopy of surfaces and as a “soft” photoionization source for gas-phase mass spectrometry.

Note: Hollow cathode lamp with integral, high optical efficiency isolation valve: a modular vacuum ultraviolet source.

Science.gov (United States)

Roberts, F Sloan; Anderson, Scott L

2013-12-01

The design and operating conditions of a hollow cathode discharge lamp for the generation of vacuum ultraviolet radiation, suitable for ultrahigh vacuum (UHV) application, are described in detail. The design is easily constructed, and modular, allowing it to be adapted to different experimental requirements. A thin isolation valve is built into one of the differential pumping stages, isolating the discharge section from the UHV section, both for vacuum safety and to allow lamp maintenance without venting the UHV chamber. The lamp has been used both for ultraviolet photoelectron spectroscopy of surfaces and as a "soft" photoionization source for gas-phase mass spectrometry.

Development of long lifetime-high current plasma cathode ion source

International Nuclear Information System (INIS)

Yabe, Eiji; Takayama, Kazuo; Fukui, Ryota.

1987-01-01

A long lifetime ion source with plasma cathode has been developed for use in ion implantation. In this ion source, a plasma of a nonreactive working gas serves as a cathode in place of a thermionic tungsten filament used in the Freeman ion source. In an applied magnetic field, the plasma cathode is convergent, i.e. filament-like; in zero magnetic field, it turns divergent and spray-like. In the latter case, the plasma exhibits a remarkable ability when the working gas has an ionization potential larger than the feed gas. By any combination of a working gas of either argon or neon and a feed gas of AsF 5 or PF 5 , the lifetime of this ion source was found to be more than 90 hours with an extraction voltage of 40 kV and the corresponding ion current density 20 mA/cm 2 . Mass spectrometry results show that this ion source has an ability of generating a considerable amount of As + and P + ions from AsF 5 and PF 5 , and hence will be useful for realizing a fully cryopumped ion implanter system. This ion source is eminently suitable for use in oxygen ion production. (author)

Materials characterization of impregnated W and W–Ir cathodes after oxygen poisoning

International Nuclear Information System (INIS)

Polk, James E.; Capece, Angela M.

2015-01-01

Highlights: • Impregnated W and W–Ir cathodes were operated with 100 ppm of oxygen in Xe gas. • High concentrations of oxygen accelerated the formation of tungstate layers. • The W–Ir emitter exhibited less erosion and redeposition at the upstream end. • Tungsten was preferentially transported in the insert plasma of the W–Ir cathode. - Abstract: Electric thrusters use hollow cathodes as the electron source for generating the plasma discharge and for beam neutralization. These cathodes contain porous tungsten emitters impregnated with BaO material to achieve a lower surface work function and are operated with xenon propellant. Oxygen contaminants in the xenon plasma can poison the emitter surface, resulting in a higher work function and increased operating temperature. This could lead directly to cathode failure by preventing discharge ignition or could accelerate evaporation of the BaO material. Exposures over hundreds of hours to very high levels of oxygen can result in increased temperatures, oxidation of the tungsten substrate, and the formation of surface layers of barium tungstates. In this work, we present results of a cathode test in which impregnated tungsten and tungsten–iridium emitters were operated with 100 ppm of oxygen in the xenon plasma for several hundred hours. The chemical and morphological changes were studied using scanning electron microscopy, energy dispersive spectroscopy, and laser profilometry. The results provide strong evidence that high concentrations of oxygen accelerate the formation of tungstate layers in both types of emitters, a phenomenon not inherent to normal cathode operation. Deposits of pure tungsten were observed on the W–Ir emitter, indicating that tungsten is preferentially removed from the surface and transported in the insert plasma. A W–Ir cathode surface will therefore evolve to a pure W composition, eliminating the work function benefit of W–Ir. However, the W–Ir emitter exhibited less erosion

Ion acceleration in multi-species cathodic plasma jet

Energy Technology Data Exchange (ETDEWEB)

Krasov, V. I.; Paperny, V. L. [Irkutsk State University, Irkutsk 664003 (Russian Federation)

2016-05-15

A general expression for ion-ion coupling in a multi-species plasma jet was obtained. The expression is valid for any value of the inter-species velocity. This expression has enabled us to review a hydrodynamic problem of expanding the cathodic plasma microjet with two ion species within the respective charge states Z{sub 1} = +1 and Z{sub 2} = +2 into a vacuum. We were able to illustrate that in scenario when the initial (i.e., acquired during a process of emission from cathode's surface) difference for ion's species velocity exceeds a threshold value, the difference remains noticeable (roughly about 10% of the average jet's velocity) at a distance of a few centimeters from the emission center. At this point, it can be measured experimentally.

Electron emission and plasma generation in a modulator electron gun using ferroelectric cathode

International Nuclear Information System (INIS)

Chen Shutao; Zheng Shuxin; Zhu Ziqiu; Dong Xianlin; Tang Chuanxiang

2006-01-01

Strong electron emission and dense plasma generation have been observed in a modulator electron gun with a Ba 0.67 Sr 0.33 TiO 3 ferroelectric cathode. Parameter of the modulator electron gun and lifetime of the ferroelectric cathode were investigated. It was shown that electron emission from Ba 0.67 Sr 0.33 TiO 3 cathode with a positive triggering pulse is a sort of plasma emission. Electrons were emitted by the co-effect of surface plasma and non-compensated negative polarization charges at the surface of the ferroelectric. The element analyses of the graphite collector after emission process was performed to show the ingredient of the plasma consist of Ba, Ti and Cu heavy cations of the ceramic compound and electrode. It was demonstrated the validity of the Child-Langmuir law by introducing the decrease of vacuum gap and increase of emission area caused by the expansion of the surface plasma

INFLUENCE OF VACUUM ARC PLASMA EVAPORATOR CATHODE GEOMETRY OF ON VALUE OF ADMISSIBLE ARC DISCHARGE CURRENT

Directory of Open Access Journals (Sweden)

I. A. Ivanou

2015-01-01

Full Text Available An analysis of main design parameters that determine a level of droplet formation intensity at the generating stage of plasma flow has been given in the paper. The paper considers the most widely used designs of water cooled consumable cathodes. Ti or Ti–Si and Fe–Cr alloys have been taken as a material for cathodes. The following calculated data: average ionic charge Zi for titanium plasma +1.6; for «titanium–silicon plasma» +1.2, an electronic discharge 1.6022 ⋅ 10–19 C, an ion velocity vi = 2 ⋅ 104 m/s, an effective volt energy equivalent of heat flow diverted in the cathode Uк = 12 V, temperature of erosion cathode surface Тп = 550 К; temperature of the cooled cathode surface То = 350 К have been accepted in order to determine dependence of a maximum admissible arc discharge current on cathode height. The calculations have been carried out for various values of the cathode heights hк (from 0.02 to 0.05 m. Diameter of a target cathode is equal to 0.08 m for a majority of technological plasma devices, therefore, the area of the erosion surface is S = 0.005 m2.A thickness selection for a consumable target cathode part in the vacuum arc plasma source has been justified in the paper. The thickness ensures formation of minimum drop phase in the plasma flow during arc cathode material evaporation. It has been shown that a maximum admissible current of an arc discharge is practically equal to the minimum current of stable arcing when thickness of the consumable cathode part is equal to 0.05 m. The admissible discharge current can be rather significant and ensure high productivity during coating process with formation of relatively low amount of droplet phase in the coating at small values of hк.

Novel methods of ozone generation by micro-plasma concept

Energy Technology Data Exchange (ETDEWEB)

Fateev, A.; Chiper, A.; Chen, W.; Stamate, E.

2008-02-15

The project objective was to study the possibilities for new and cheaper methods of generating ozone by means of different types of micro-plasma generators: DBD (Dielectric Barrier Discharge), MHCD (Micro-Hollow Cathode Discharge) and CPED (Capillary Plasma Electrode Discharge). This project supplements another current project where plasma-based DeNOx is being studied and optimised. The results show potentials for reducing ozone generation costs by means of micro-plasmas but that further development is needed. (ln)

Reservoir Cathode for Electric Space Propulsion, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — We propose a hollow reservoir cathode to improve performance in ion and Hall thrusters. We will adapt our existing reservoir cathode technology to this purpose....

Determination of self-absorption in emission lines from some optically thick plasmas

International Nuclear Information System (INIS)

Pianarosa, P.; Gagne, J.M.; Larin, G.; Saint-Dizier, J.P.

1982-01-01

We present a relatively simple method by which the amount of self-absorption in laboratory-produced plasmas can be evaluated. As an illustration we apply it here to the evaluation of self-absorption of a U I resonance transition from a hollow-cathode-generated plasma. The method can be generalized to include more-complex situations

Electron depletion via cathode spot dispersion of dielectric powder into an overhead plasma

International Nuclear Information System (INIS)

Gillman, Eric D.; Foster, John E.

2013-01-01

The effectiveness of cathode spot delivered dielectric particles for the purpose of plasma depletion is investigated. Here, cathode spot flows kinetically entrain and accelerate dielectric particles originally at rest into a background plasma. The time variation of the background plasma density is tracked using a cylindrical Langmuir probe biased approximately at electron saturation. As inferred from changes in the electron saturation current, depletion fractions of up to 95% are observed. This method could be exploited as a means of communications blackout mitigation for manned and unmanned reentering spacecraft as well as any high speed vehicle enveloped by a dense plasma layer

An experimental study of the ion energy balance of a magnetized plasma

International Nuclear Information System (INIS)

Pots, B.F.M.; Hooff, P. van; Schram, D.C.; Sijde, B. van der

1981-01-01

A report is given on an experimental study of the ion energy balance of the magnetized and current-driven plasma f a hollow cathode discharge. The balance appears to be classical. At the axis of the plasma column the electron-ion Coulomb interaction is in equilibrium with the ion-neutral interaction. No significant influence on the energy balance by the spontaneously appearing plasma turbulence is formed. (author)

Experimental study of the discharge in the low pressure plasma jet sputtering system

Czech Academy of Sciences Publication Activity Database

Klusoň, J.; Kudrna, P.; Kolpaková, A.; Picková, I.; Hubička, Zdeněk; Tichý, M.

2013-01-01

Roč. 53, č. 1 (2013), s. 10-15 ISSN 0863-1042 Institutional support: RVO:68378271 Keywords : hollow cathode * plasma jet sputtering system * Langmuir probe Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.983, year: 2013

High-power pulsed plasma deposition of hematite photoanode for PEC water splitting

Czech Academy of Sciences Publication Activity Database

Kment, Š.; Hubička, Zdeněk; Krysa, J.; Olejníček, Jiří; Čada, Martin; Gregora, Ivan; Zlámal, M.; Brunclíková, Michaela; Remeš, Zdeněk; Liu, N.; Wang, L.; Kirchgeorg, R.; Lee, Ch.Y.; Schmuki, P.

2014-01-01

Roč. 230, Jul (2014), 8-14 ISSN 0920-5861 R&D Projects: GA ČR GAP108/12/2104; GA MŠk LH12043 Institutional support: RVO:68378271 Keywords : electrical properties * hematite * HiPIMS * hollow cathode plasma jet * photoelectrochemical water splitting * thin films Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.893, year: 2014

Anomalous Shf radiation of a stationary plasma engine

International Nuclear Information System (INIS)

Kirdyashev, K.P.; Efimov, A.I.; Lukin, D.S.

2002-01-01

The results of the preflight radio technical tests of the thrust moduli of the combined engine facility of the Jamal-100 space vehicle are presented. The pulse constituent of the electromagnetic radiation, connected with the unstable processes of the electron emission from the hollow cathode - compensator plasma, is identified [ru

Studies on the optogalvanic effect and isotope-selective excitation of ytterbium in a hollow cathode discharge lamp using a pulsed dye laser.

Science.gov (United States)

Kumar, Pankaj; Kumar, Jitendra; Prakash, Om; Saini, Vinod K; Dixit, Sudhir K; Nakhe, Shankar V

2013-09-01

This paper presents studies on the pulsed optogalvanic effect and isotope-selective excitation of Yb 555.648 nm (0 cm(-1) → 17 992.007 cm(-1)) and 581.067 nm (17 992.007 cm(-1) → 35 196.98 cm(-1)) transitions, in a Yb/Ne hollow cathode lamp. The Yb atoms were excited by narrow linewidth (500-1000 MHz) Rh110 and Rh6G dye based pulsed lasers. Optogalvanic signal inversion for ground state transition at 555.648 nm was observed beyond a hollow cathode discharge current of 8.5 mA, in contrast to normal optogalvanic signal at 581.067 nm up to maximum current of 14 mA. The isotope-selective excitation studies of Yb were carried out by recording Doppler limited optogalvanic signals as a function of dye laser wavelength. For the 581.067 nm transition, three even isotopes, (172)Yb, (174)Yb, and (176)Yb, and one odd isotope, (171)Yb, were clearly resolved. These data were compared with selective isotope excitation by 10 MHz linewidth continuous-wave dye laser. For 555.648 nm transition, isotopes were not clearly resolved, although isotope peaks of low modulation were observed.

Advanced Cathodes for Next Generation Electric Propulsion Technology

Science.gov (United States)

2008-03-01

learning opportunity- of which it did. Finally, Dr. Glen Perram of the physics department at AFIT was so gracious to let us borrow his Langmuir Probe in...Applications Like Hall thrusters, ion thrusters also employ hollow cathodes.15,18,19,20,21 Harold Kaufman at NASA Glen Research Center (GRC... brittle nature, a problem common to CeB6 and LaB6. As a result, easier to machine polycrystalline inserts for LaB6 have been used for hollow cathodes in

Two-dimensional simulations of multi-hollow VHF SiH4/H2 plasma

Directory of Open Access Journals (Sweden)

Li-Wen Su

2018-02-01

Full Text Available A triode multi-hollow VHF SiH4/H2 plasma (60 MHz was examined at a pressure of 20 Pa by two-dimensional simulations using the fluid model. In this study, we considered the effect of the rate constant of reaction, SiH3 + SiH3→SiH2 + SiH4, on the plasma characteristics. A typical VHF plasma of a high-electron density with a low-electron temperature was obtained between two discharge electrodes. Spatial profiles of SiH3+, SiH2+, SiH3- and SiH3 densities were similar to that of the electron density while the electron temperature had a maximum value near the two discharge electrodes. It was found that the SiH3 radical density did not decrease rapidly near the substrate and the electron temperature was lower than 1 eV, suggesting that the triode multi-hollow plasma source can provide high quality amorphous silicon with a high deposition rate.

Air plasma spray processing and electrochemical characterization of SOFC composite cathodes

Science.gov (United States)

White, B. D.; Kesler, O.; Rose, Lars

Air plasma spraying has been used to produce porous composite cathodes containing (La 0.8Sr 0.2) 0.98MnO 3- y (LSM) and yttria-stabilized zirconia (YSZ) for use in solid oxide fuel cells (SOFCs). Preliminary investigations focused on determining the range of plasma conditions under which each of the individual materials could be successfully deposited. A range of conditions was thereby determined that was suitable for the deposition of a composite cathode from pre-mixed LSM and YSZ powders. A number of composite cathodes were produced using different combinations of parameter values within the identified range according to a Uniform Design experimental grid. Coatings were then characterized for composition and microstructure using EDX and SEM. As a result of these tests, combinations of input parameter values were identified that are best suited to the production of coatings with microstructures appropriate for use in SOFC composite cathodes. A selection of coatings representative of the types of observed microstructures were then subjected to electrochemical testing to evaluate the performance of these cathodes. From these tests, it was found that, in general, the coatings that appeared to have the most suitable microstructures also had the highest electrochemical performances, provided that the deposition efficiency of both phases was sufficiently high.

Air plasma spray processing and electrochemical characterization of SOFC composite cathodes

Energy Technology Data Exchange (ETDEWEB)

White, B.D. [Department of Mechanical Engineering, The University of British Columbia, 2054-6250 Applied Sciences Lane, Vancouver, British Columbia (Canada); Kesler, O. [Department of Mechanical and Industrial Engineering, University of Toronto, 5 King' s College Road, Toronto, Ontario (Canada); Rose, Lars [Department of Materials Engineering, The University of British Columbia, 309-6350 Stores Road, Vancouver, British Columbia (Canada); National Research Council (Canada)

2008-03-15

Air plasma spraying has been used to produce porous composite cathodes containing (La{sub 0.8}Sr{sub 0.2}){sub 0.98}MnO{sub 3-y} (LSM) and yttria-stabilized zirconia (YSZ) for use in solid oxide fuel cells (SOFCs). Preliminary investigations focused on determining the range of plasma conditions under which each of the individual materials could be successfully deposited. A range of conditions was thereby determined that was suitable for the deposition of a composite cathode from pre-mixed LSM and YSZ powders. A number of composite cathodes were produced using different combinations of parameter values within the identified range according to a Uniform Design experimental grid. Coatings were then characterized for composition and microstructure using EDX and SEM. As a result of these tests, combinations of input parameter values were identified that are best suited to the production of coatings with microstructures appropriate for use in SOFC composite cathodes. A selection of coatings representative of the types of observed microstructures were then subjected to electrochemical testing to evaluate the performance of these cathodes. From these tests, it was found that, in general, the coatings that appeared to have the most suitable microstructures also had the highest electrochemical performances, provided that the deposition efficiency of both phases was sufficiently high. (author)

Atmospheric Plasma Spraying Low-Temperature Cathode Materials for Solid Oxide Fuel Cells

Science.gov (United States)

Harris, J.; Kesler, O.

2010-01-01

Atmospheric plasma spraying (APS) is attractive for manufacturing solid oxide fuel cells (SOFCs) because it allows functional layers to be built rapidly with controlled microstructures. The technique allows SOFCs that operate at low temperatures (500-700 °C) to be fabricated by spraying directly onto robust and inexpensive metallic supports. However, standard cathode materials used in commercial SOFCs exhibit high polarization resistances at low operating temperatures. Therefore, alternative cathode materials with high performance at low temperatures are essential to facilitate the use of metallic supports. Coatings of lanthanum strontium cobalt ferrite (LSCF) were fabricated on steel substrates using axial-injection APS. The thickness and microstructure of the coating layers were evaluated, and x-ray diffraction analysis was performed on the coatings to detect material decomposition and the formation of undesired phases in the plasma. These results determined the envelope of plasma spray parameters in which coatings of LSCF can be manufactured, and the range of conditions in which composite cathode coatings could potentially be manufactured.

Improving the Ar I and II branching ratio calibration method: Monte Carlo simulations of effects from photon scattering/reflecting in hollow cathodes

Science.gov (United States)

Lawler, J. E.; Den Hartog, E. A.

2018-03-01

The Ar I and II branching ratio calibration method is discussed with the goal of improving the technique. This method of establishing a relative radiometric calibration is important in ongoing research to improve atomic transition probabilities for quantitative spectroscopy in astrophysics and other fields. Specific suggestions are presented along with Monte Carlo simulations of wavelength dependent effects from scattering/reflecting of photons in a hollow cathode.

Plasma gun with coaxial powder feed and adjustable cathode

Science.gov (United States)

Zaplatynsky, Isidor (Inventor)

1991-01-01

An improved plasma gun coaxially injects particles of ceramic materials having high melting temperatures into the central portion of a plasma jet. This results in a more uniform and higher temperature and velocity distribution of the sprayed particles. The position of the cathode is adjustable to facilitate optimization of the performance of the gun wherein grains of the ceramic material are melted at lower power input levels.

The evolution of ion charge states in cathodic vacuum arc plasmas: a review

Energy Technology Data Exchange (ETDEWEB)

Anders, Andre

2011-12-18

Cathodic vacuum arc plasmas are known to contain multiply charged ions. 20 years after “Pressure Ionization: its role in metal vapour vacuum arc plasmas and ion sources” appeared in vol. 1 of Plasma Sources Science and Technology, it is a great opportunity to re-visit the issue of pressure ionization, a non-ideal plasma effect, and put it in perspective to the many other factors that influence observable charge state distributions, such as the role of the cathode material, the path in the density-temperature phase diagram, the “noise” in vacuum arc plasma as described by a fractal model approach, the effects of external magnetic fields and charge exchange collisions with neutrals. A much more complex image of the vacuum arc plasma emerges putting decades of experimentation and modeling in perspective.

Polychromatic holographic plasma diagnostics

International Nuclear Information System (INIS)

Zhiglinskij, A.G.; Morozov, A.O.

1992-01-01

Review of holographic interferometry properties is performed and advantages of this method by plasma diagnostics are indicated. Main results obtained by the method of holographic interferometry in studies of various-type plasmas are considered. Special attention is paid to multiwave plasma diagnostics, the necessity of which is related as a rule to multicomponent composition of plasma. The eight laser and gas-discharge sources and holographic schemes, which make it possible to realize plasma polychromatic and holographic interferometry, are considered. The advantages of the method are demonstrated by examples of polychromatic holographic diagnostics of arc discharge and discharge in a hollow cathode. Review of theoretical works determining the applicability area of resonance polychromatic interferometry is carried out

Floating harmonic probe measurements in the low-temperature plasma jet deposition system

Czech Academy of Sciences Publication Activity Database

Zanáška, M.; Hubička, Zdeněk; Čada, Martin; Kudrna, Pavel; Tichý, M.

2018-01-01

Roč. 51, č. 2 (2018), s. 1-8, č. článku 025205. ISSN 0022-3727 R&D Projects: GA ČR(CZ) GA15-00863S Institutional support: RVO:68378271 Keywords : plasma diagnostic * floating harmonic probe * Langmuir probe * hollow cathode * non-conducting film deposition Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics ) Impact factor: 2.588, year: 2016

Injection into electron plasma traps

International Nuclear Information System (INIS)

Gorgadze, Vladimir; Pasquini, Thomas A.; Fajans, Joel; Wurtele, Jonathan S.

2003-01-01

Computational studies and experimental measurements of plasma injection into a Malmberg-Penning trap reveal that the number of trapped particles can be an order of magnitude higher than predicted by a simple estimates based on a ballistic trapping model. Enhanced trapping is associated with a rich nonlinear dynamics generated by the space-charge forces of the evolving trapped electron density. A particle-in-cell simulation is used to identify the physical mechanisms that lead to the increase in trapped electrons. The simulations initially show strong two-stream interactions between the electrons emitted from the cathode and those reflected off the end plug of the trap. This is followed by virtual cathode oscillations near the injection region. As electrons are trapped, the initially hollow longitudinal phase-space is filled, and the transverse radial density profile evolves so that the plasma potential matches that of the cathode. Simple theoretical arguments are given that describe the different dynamical regimes. Good agreement is found between simulation and theory

Barium Depletion in the NSTAR Discharge Cathode After 30,000 Hours of Operation

Science.gov (United States)

Polk, James E.; Capece, Angela M.; Mikellides, Ioannis G.; Katz, Ira

2010-01-01

Dispenser hollow cathodes rely on a consumable supply of barium released by impregnant materials in the pores of a tungsten matrix to maintain a low work function surface. Examinations of cathode inserts from long duration ion engine tests show deposits of tungsten at the downstream end that appear to block the flow of barium from the interior. In addition, a numerical model of barium transport in the insert plasma indicates that the barium partial pressure in the insert may exceed the equilibrium vapor pressure of the dominant barium-producing reaction, and it was postulated previously that this would suppress barium loss in the upstream part of the insert. New measurements of the depth of barium depletion from a cathode insert operated for 30,352 hours reveal that barium loss is confined to a narrow region near the downstream end, confirming this hypothesis.

Effect of substrate and cathode parameters on the properties of suspension plasma sprayed solid oxide fuel cell electrolytes

Energy Technology Data Exchange (ETDEWEB)

Waldbillig, D.; Tang, Z.; Burgess, A. [British Columbia Univ., Vancouver, BC (Canada); Kesler, O. [Toronto Univ., ON (Canada)

2008-07-01

An axial injection suspension plasma spray system has been used to produce layers of fully stabilized yttriastabilized zirconia (YSZ) that could be used as solid oxide fuel cell (SOFC) electrolytes. Suspension plasma spraying is a promising technique for the rapid production of coatings with fine microstructures and controlled porosity without requiring a post-deposition heat treatment. This new manufacturing technique to produce SOFC active layers requires the build up of a number of different plasma sprayed SOFC functional layers (cathode, electrolyte and anode) sequentially on top of each other. To understand the influence of the substrate and previouslydeposited coating layers on subsequent coating layer properties, YSZ layers were deposited on top of plasma sprayed composite lanthanum strontium manganite (LSM)/YSZ cathode layers that were first deposited on porous ferritic stainless steel substrates. Three layer half cells consisting of the porous steel substrate, composite cathode, and suspension plasma sprayed electrolyte layer were then characterized. A systematic study was performed in order to investigate the effect of parameters such as substrate and cathode layer roughness, substrate surface pore size, and cathode microstructure and thickness on electrolyte deposition efficiency, cathode and electrolyte permeability, and layer microstructure. (orig.)

Development of a see-through hollow cathode discharge lamp for (Li/Ne) optogalvanic studies

Science.gov (United States)

Saini, V. K.; Kumar, P.; Sarangpani, K. K.; Dixit, S. K.; Nakhe, S. V.

2017-09-01

Development of a demountable and see-through hollow cathode (HC) discharge lamp suitable for optogalvanic (OG) spectroscopy is described. The design of the HC lamp is simple, compact, and inexpensive. Lithium, investigated rarely by the OG method, is selected for cathode material as its isotopes are important for nuclear industry. The HC lamp is characterized electrically and optically for discharge oscillations free OG effect. Strong OG signals of lithium as well as neon (as buffer gas) are produced precisely upon copper vapor laser pumped tunable dye laser irradiation. The HC lamp is capable of generating a clean OG resonance spectrum in the available dye laser wavelength scanning range (627.5-676 nm) obtained with 4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran dye. About 28 resonant OG lines are explicitly observed. Majority of them have been identified using j-l coupling scheme and assigned to the well-known neon transitions. One line that corresponds to wavelength near about 670.80 nm is assigned to lithium and resolved for its fine (2S1/2 → 2P1/2, 3/2) transitions. These OG transitions allow 0.33 cm-1 accuracy and can be used to supplement the OG transition data available from other sources to calibrate the wavelength of a scanning dye laser with precision at atomic levels.

Cathodic Vacuum Arc Plasma of Thallium

International Nuclear Information System (INIS)

Yushkov, Georgy Yu.; Anders, Andre

2006-01-01

Thallium arc plasma was investigated in a vacuum arc ion source. As expected from previous consideration of cathode materials in the Periodic Table of the Elements, thallium plasma shows lead-like behavior. Its mean ion charge state exceeds 2.0 immediately after arc triggering, reaches the predicted 1.60 and 1.45 after about 100 microsec and 150 microsec, respectively. The most likely ion velocity is initially8000 m/s and decays to 6500 m/s and 6200 m/s after 100 microsec and 150microsec, respectively. Both ion charge states and ion velocities decay further towards steady state values, which are not reached within the 300microsec pulses used here. It is argued that the exceptionally high vapor pressure and charge exchange reactions are associated with the establishment of steady state ion values

Population distribution of atomic uranium in the afterglow of a pulsed hollow-cathode discharge

International Nuclear Information System (INIS)

Demers, Yves; Gagne, J.-M.; Pianarosa, Piero

1987-01-01

From laser absorption measurements we have deduced the time evolution of the population distribution of atomic uranium in the afterglow of a pulsed hollow-cathode type discharge. The vapour generator operates with xenon as the discharge sustaining gas at a pressure of 280 Pa (2.1 Torr). The current pulse characteristics are width 250 μs and height 1.5 A. The pulse repetition frequency is 100 Hz. It is shown that the populations in the three metastable levels at 6249, 3868 and 3800 cm -1 decrease almost exponentially in a time interval between 150 and 300 μs. From 400 μs onwards in the afterglow, the atom population is essentially shared between the ground and the first metastable (620 cm -1 ) levels. Furthermore, starting from 9 ms in the afterglow more than 80% of the U atoms are found in the ground level. (author)

Demonstration of the hollow channel plasma wakefield accelerator

Energy Technology Data Exchange (ETDEWEB)

Gessner, Spencer J.

2016-09-17

A plasma wakefield accelerator is a device that converts the energy of a relativistic particle beam into a large-amplitude wave in a plasma. The plasma wave, or wakefield, supports an enormous electricfield that is used to accelerate a trailing particle beam. The plasma wakefield accelerator can therefore be used as a transformer, transferring energy from a high-charge, low-energy particle beam into a high-energy, low-charge particle beam. This technique may lead to a new generation of ultra-compact, high-energy particle accelerators. The past decade has seen enormous progress in the field of plasma wakefield acceleration with experimental demonstrations of the acceleration of electron beams by several gigaelectron-volts. The acceleration of positron beams in plasma is more challenging, but also necessary for the creation of a high-energy electron-positron collider. Part of the challenge is that the plasma responds asymmetrically to electrons and positrons, leading to increased disruption of the positron beam. One solution to this problem, first proposed over twenty years ago, is to use a hollow channel plasma which symmetrizes the response of the plasma to beams of positive and negative charge, making it possible to accelerate positrons in plasma without disruption. In this thesis, we describe the theory relevant to our experiment and derive new results when needed. We discuss the development and implementation of special optical devices used to create long plasma channels. We demonstrate for the first time the generation of meter-scale plasma channels and the acceleration of positron beams therein.

Destructive physical analysis of hollow cathodes from the Deep Space 1 Flight spare ion engine 30,000 hr life test

Science.gov (United States)

Sengupta, Anita

2005-01-01

Destructive physical analysis of the discharge and neutralizer hollow cathode assemblies from the Deep Space 1 Flight Spare 30,000 Hr life test was performed to characterize physical and chemical evidence of operationally induced effects after 30,372 hours of operation with beam extraction. Post-test inspection of the discharge-cathode assembly was subdivided into detailed analyses at the subcomponent level. Detailed materials analysis and optical inspection of the insert, orifice plate, cathode tube, heater, keeper assembly, insulator, and low-voltage propellant isolator were performed. Energy dispersive X-ray (EDX) and scanning electron microscopy (SEW analyses were used to determine the extent and composition of regions of net deposition and erosion of both the discharge and neutralizer inserts. A comparative approach with an un-operated 4:1:1 insert was used to determine the extent of impregnate material depletion as a function of depth from the ID surface and axial position from the orifice plate. Analysis results are compared and contrasted with those obtained from similar analyses on components from shorter term tests, and provide insight regarding the prospect for successful longer-term operation consistent with SOA ion engine program life objectives at NASA.

Cathode for Electric Space Propulsion Utilizing Iodine as Propellant, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — We propose a hollow reservoir cathode suitable for use in ion or Hall thrusters which utilizes iodine as a propellant. Reservoir cathodes have several unique...

Solvothermal Synthesis of a Hollow Micro-Sphere LiFePO4/C Composite with a Porous Interior Structure as a Cathode Material for Lithium Ion Batteries

Science.gov (United States)

Liu, Yang; Zhang, Jieyu; Li, Ying; Hu, Yemin; Li, Wenxian; Zhu, Mingyuan; Hu, Pengfei; Chou, Shulei; Wang, Guoxiu

2017-01-01

To overcome the low lithium ion diffusion and slow electron transfer, a hollow micro sphere LiFePO4/C cathode material with a porous interior structure was synthesized via a solvothermal method by using ethylene glycol (EG) as the solvent medium and cetyltrimethylammonium bromide (CTAB) as the surfactant. In this strategy, the EG solvent inhibits the growth of the crystals and the CTAB surfactant boots the self-assembly of the primary nanoparticles to form hollow spheres. The resultant carbon-coat LiFePO4/C hollow micro-spheres have a ~300 nm thick shell/wall consisting of aggregated nanoparticles and a porous interior. When used as materials for lithium-ion batteries, the hollow micro spherical LiFePO4/C composite exhibits superior discharge capacity (163 mAh g−1 at 0.1 C), good high-rate discharge capacity (118 mAh g−1 at 10 C), and fine cycling stability (99.2% after 200 cycles at 0.1 C). The good electrochemical performances are attributed to a high rate of ionic/electronic conduction and the high structural stability arising from the nanosized primary particles and the micro-sized hollow spherical structure. PMID:29099814

Solvothermal Synthesis of a Hollow Micro-Sphere LiFePO4/C Composite with a Porous Interior Structure as a Cathode Material for Lithium Ion Batteries

Directory of Open Access Journals (Sweden)

Yang Liu

2017-11-01

Full Text Available To overcome the low lithium ion diffusion and slow electron transfer, a hollow micro sphere LiFePO4/C cathode material with a porous interior structure was synthesized via a solvothermal method by using ethylene glycol (EG as the solvent medium and cetyltrimethylammonium bromide (CTAB as the surfactant. In this strategy, the EG solvent inhibits the growth of the crystals and the CTAB surfactant boots the self-assembly of the primary nanoparticles to form hollow spheres. The resultant carbon-coat LiFePO4/C hollow micro-spheres have a ~300 nm thick shell/wall consisting of aggregated nanoparticles and a porous interior. When used as materials for lithium-ion batteries, the hollow micro spherical LiFePO4/C composite exhibits superior discharge capacity (163 mAh g−1 at 0.1 C, good high-rate discharge capacity (118 mAh g−1 at 10 C, and fine cycling stability (99.2% after 200 cycles at 0.1 C. The good electrochemical performances are attributed to a high rate of ionic/electronic conduction and the high structural stability arising from the nanosized primary particles and the micro-sized hollow spherical structure.

Laser beam absorption study of a 238U(5L60) vapor obtained with a hollow cathode lamp

International Nuclear Information System (INIS)

Gagne, J.M.; Leblanc, B.; Mongeau, B.; Carleer, M.; Bertrand, L.

1979-01-01

The density of U atoms in the 5 L 0 6 ground state present in a vapor of this element from a hollow cathode lamp has been measured using laser absorption spectroscopy. The influence of the carrier gases (Ar, Kr, Xe) on the density, the absorption coefficient profiles, and on the ratio of U atoms to the dissipated electrical power has been investigated. It has been found that, in our range of operating conditions, the xenon gas is the most efficient. With xenon, a density of 2.2 x 10 12 cm -3 ground-state U atoms is obtained when the lamp dissipates 40 W of electrical power

Ignition and extinction phenomena in helium micro hollow cathode discharges

International Nuclear Information System (INIS)

Kulsreshath, M. K.; Schwaederle, L.; Dufour, T.; Lefaucheux, P.; Dussart, R.; Sadeghi, N.; Overzet, L. J.

2013-01-01

Micro hollow cathode discharges (MHCD) were produced using 250 μm thick dielectric layer of alumina sandwiched between two nickel electrodes of 8 μm thickness. A through cavity at the center of the chip was formed by laser drilling technique. MHCD with a diameter of few hundreds of micrometers allowed us to generate direct current discharges in helium at up to atmospheric pressure. A slowly varying ramped voltage generator was used to study the ignition and the extinction periods of the microdischarges. The analysis was performed by using electrical characterisation of the V-I behaviour and the measurement of He*( 3 S 1 ) metastable atoms density by tunable diode laser spectroscopy. At the ignition of the microdischarges, 2 μs long current peak as high as 24 mA was observed, sometimes followed by low amplitude damped oscillations. At helium pressure above 400 Torr, an oscillatory behaviour of the discharge current was observed just before the extinction of the microdischarges. The same type of instability in the extinction period at high pressure also appeared on the density of He*( 3 S 1 ) metastable atoms, but delayed by a few μs relative to the current oscillations. Metastable atoms thus cannot be at the origin of the generation of the observed instabilities

Ignition and extinction phenomena in helium micro hollow cathode discharges

Energy Technology Data Exchange (ETDEWEB)

Kulsreshath, M. K.; Schwaederle, L.; Dufour, T.; Lefaucheux, P.; Dussart, R. [GREMI, CNRS/Université d' Orléans (UMR7344), Orléans (France); Sadeghi, N. [LIPhy, CNRS and Universite Joseph Fourier (UMR5588), Grenoble (France); Overzet, L. J. [GREMI, CNRS/Université d' Orléans (UMR7344), Orléans (France); PSAL, UTDallas, Richardson, Texas 75080-3021 (United States)

2013-12-28

Micro hollow cathode discharges (MHCD) were produced using 250 μm thick dielectric layer of alumina sandwiched between two nickel electrodes of 8 μm thickness. A through cavity at the center of the chip was formed by laser drilling technique. MHCD with a diameter of few hundreds of micrometers allowed us to generate direct current discharges in helium at up to atmospheric pressure. A slowly varying ramped voltage generator was used to study the ignition and the extinction periods of the microdischarges. The analysis was performed by using electrical characterisation of the V-I behaviour and the measurement of He*({sup 3}S{sub 1}) metastable atoms density by tunable diode laser spectroscopy. At the ignition of the microdischarges, 2 μs long current peak as high as 24 mA was observed, sometimes followed by low amplitude damped oscillations. At helium pressure above 400 Torr, an oscillatory behaviour of the discharge current was observed just before the extinction of the microdischarges. The same type of instability in the extinction period at high pressure also appeared on the density of He*({sup 3}S{sub 1}) metastable atoms, but delayed by a few μs relative to the current oscillations. Metastable atoms thus cannot be at the origin of the generation of the observed instabilities.

Long-life cathode for the Berkeley-type ion source

International Nuclear Information System (INIS)

Fink, J.H.; Biagi, L.A.

1977-01-01

Preliminary experiments indicate that a hollow cathode, made from impregnated tungsten emitters, can be adapted for the Lawrence Berkeley Laboratory (LBL)/Lawrence Livermore Laboratory (LLL) ion source. Such cathodes could be the basis of a long life, continuously operated positive-ion source

Varying Radii of On-Axis Anode Hollows For kJ-Class Dense Plasma Focus

Science.gov (United States)

Shaw, Brian; Chapman, Steven; Falabella, Steven; Pankin, Alexei; Liu, Jason; Link, Anthony; Schmidt, Andréa

2017-10-01

A dense plasma focus (DPF) is a compact plasma gun that produces high energy ion beams, up to several MeV, through strong potential gradients. Motivated by particle-in-cell simulations, we have tried a series of hollow anodes on our kJ-class DPF. Each anode has varying hollow sizes, and has been studied to optimize ion beam production in Helium, reduce anode sputter, and increase neutron yields in deuterium. We diagnose the rate at which electrode material is ablated and deposited onto nearby surfaces. This is of interest in the case of solid targets, which perform poorly in the presence of sputter. We have found that the larger the hollow radius produces more energetic ion beams, higher neutron yield, and sputter less than a flat top anode. A complete comparison is presented. This work was prepared by LLNL under Contract DE-AC52-07NA27344 and supported by Office of Defense Nuclear Nonproliferation Research and Development within U.S. Department of Energy's National Nuclear Security Administration.

Excitation of quasi-electrostatic modes in a magnetized plasma by a modulated hollow E-beam

International Nuclear Information System (INIS)

Ezzeddine, A.; Smullin, L.D.

1982-01-01

The power radiated into the modes of an infinite magnetized plasma by a modulated hollow electron beam is calculated for the cases of cold and warm plasmas. The beam is assumed to be sinusoidally density modulated and the induced fluctuating electric field is strong enough to quench any beam plasma interaction. Numerical results are presented for the power deposited into the plasma at frequencies near the lower hybrid frequency for different beam plasma parameters

Solvothermal synthesis of monodisperse LiFePO4 micro hollow spheres as high performance cathode material for lithium ion batteries.

Science.gov (United States)

Yang, Shiliu; Hu, Mingjun; Xi, Liujiang; Ma, Ruguang; Dong, Yucheng; Chung, C Y

2013-09-25

A microspherical, hollow LiFePO4 (LFP) cathode material with polycrystal structure was simply synthesized by a solvothermal method using spherical Li3PO4 as the self-sacrificed template and FeCl2·4H2O as the Fe(2+) source. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the LFP micro hollow spheres have a quite uniform size of ~1 μm consisting of aggregated nanoparticles. The influences of solvent and Fe(2+) source on the phase and morphology of the final product were chiefly investigated, and a direct ion exchange reaction between spherical Li3PO4 templates and Fe(2+) ions was firstly proposed on the basis of the X-ray powder diffraction (XRD) transformation of the products. The LFP nanoparticles in the micro hollow spheres could finely coat a uniform carbon layer ~3.5 nm by a glucose solution impregnating-drying-sintering process. The electrochemical measurements show that the carbon coated LFP materials could exhibit high charge-discharge capacities of 158, 144, 125, 101, and even 72 mAh g(-1) at 0.1, 1, 5, 20, and 50 C, respectively. It could also maintain 80% of the initial discharge capacity after cycling for 2000 times at 20 C.

Studies on pulsed optogalvanic effect in Eu/Ne hollow cathode discharge.

Science.gov (United States)

Saini, V K; Kumar, P; Dixit, S K; Nakhe, S V

2014-07-01

The optogalvanic (OG) effect has been observed in a Eu/Ne hollow cathode discharge lamp using pulsed laser irradiation. An OG spectrum is recorded in dye laser wavelength region 574–602 nm using a boxcar-averager. In total 41 atomic lines are observed. Of these, 38 lines are assigned to neon transitions. Two lines observed corresponding to wavelengths 576.519 and 601.815 nm are assigned to europium transitions; (4f 7 6s 2 , S 8 7/2 →4f 7 6s6p , zP 6 7/2 ) and (4f 7 6s 2 , S 8 7/2 →4f 7 6s6p , zP 8 9/2 ), respectively, and the remaining line at 582.475 nm could not be assigned. The effect of the discharge current on europium as well as neon OG signals is also studied. At moderate discharge current values, an extra positive peak is observed in neon OG signal for the transition (1s 5 →2p 2 ) at 588.189 nm, which is explained by Penning-ionization process using the quasi-resonant energy transfer interactions between excited neon and europium atoms lying in 2p 2 and D 10 9/2 states, respectively.

Soliton-plasma nonlinear dynamics in mid-IR gas-filled hollow-core fibers

DEFF Research Database (Denmark)

Habib, Selim; Markos, Christos; Bang, Ole

2017-01-01

We investigate numerically soliton-plasma interaction in a noble-gas-filled silica hollow-core anti-resonant fiber pumped in the mid-IR at 3.0 mu m. We observe multiple soliton self-compression stages due to distinct stages where either the self-focusing or the self-defocusing nonlinearity...

Deposition of porous cathodes using plasma spray technique for reduced-temperature SOFCs

Energy Technology Data Exchange (ETDEWEB)

Jankovic, J.; Hui, S.; Roller, J.; Kesler, O.; Xie, Y.; Maric, R.; Ghosh, D. [National Research Council of Canada, Vancouver, BC (Canada). Inst. for Fuel Cell Innovation

2005-07-01

Current techniques for Solid Oxide Fuel Cell (SOFC) materials deposition are often expensive and time-consuming. Plasma-spraying techniques provide higher deposition rates, short processing times and control over porosity and composition during deposition. Optimum plasma spraying for lanthanum based cathode materials were discussed. Plasma-spraying was used to deposit cathode materials onto ceramic and stainless steel substrates to obtain highly porous structures. Lanthanum cathode materials with composition of La{sub 0.6}Sr{sub 0.4}C{sub 0.2}Fe{sub 0.8}O{sub 3} were employed in the powder form. The powder was prepared from powder precursors with different power formers and binder levels, or from produced single-phase lanthanum powders. The (La{sub 0.8}Sr{sub 0.2}){sub 0.98}MnO{sub 3} cathode material was also processed for comparison purposes. The deposition process was developed to obtain coatings with good bond strength, porosity, film thickness and residual stresses. The phase and microstructure of deposited materials were characterized using X-Ray Diffraction and Scanning Electron Microscopy (SEM). It was concluded that good flow of the powder precursors is achieved by spraying 50-100 um particle size powders and using vibrating feeders. Further processing of the spraying powders was recommended. It was noted that oxide precursors showed greater reactivity among the precursors. The best precursor reactivity and coating morphology was obtained using 40 volume per cent of graphite pore former, incorporated into the precursor mixture during wet ball milling. It was concluded that higher power levels and larger distances between the plasma gun and the substrate result in coatings with the highest porosities and best phase compositions. 5 refs., 1 tab., 6 figs.

Effect of N{sub 2} and Ar gas on DC arc plasma generation and film composition from Ti-Al compound cathodes

Energy Technology Data Exchange (ETDEWEB)

Zhirkov, Igor, E-mail: igozh@ifm.liu.se; Rosen, Johanna [Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Oks, Efim [Institute of High Current Electronics SB RAS, 2/3 Akademichesky Avenue, 634055 Tomsk (Russian Federation)

2015-06-07

DC arc plasma from Ti, Al, and Ti{sub 1−x}Al{sub x} (x = 0.16, 0.25, 0.50, and 0.70) compound cathodes has been characterized with respect to plasma chemistry (charged particles) and charge-state-resolved ion energy for Ar and N{sub 2} pressures in the range 10{sup −6} to 3 × 10{sup −2} Torr. Scanning electron microscopy was used for exploring the correlation between the cathode and film composition, which in turn was correlated with the plasma properties. In an Ar atmosphere, the plasma ion composition showed a reduction of Al of approximately 5 at. % compared to the cathode composition, while deposited films were in accordance with the cathode stoichiometry. Introducing N{sub 2} above ∼5 × 10{sup −3} Torr, lead to a reduced Al content in the plasma as well as in the film, and hence a 1:1 correlation between the cathode and film composition cannot be expected in a reactive environment. This may be explained by an influence of the reactive gas on the arc mode and type of erosion of Ti and Al rich contaminations, as well as on the plasma transport. Throughout the investigated pressure range, a higher deposition rate was obtained from cathodes with higher Al content. The origin of generated gas ions was investigated through the velocity rule, stating that the most likely ion velocities of all cathode elements from a compound cathode are equal. The results suggest that the major part of the gas ions in Ar is generated from electron impact ionization, while gas ions in a N{sub 2} atmosphere primarily originate from a nitrogen contaminated layer on the cathode surface. The presented results provide a contribution to the understanding processes of plasma generation from compound cathodes. It also allows for a more reasonable approach to the selection of composite cathode and experimental conditions for thin film depositions.

Temporal development of the composition of Zr and Cr cathodic arc plasma streams in a N2 environment

International Nuclear Information System (INIS)

Rosen, Johanna; Anders, Andre; Hultman, Lars; Schneider, Jochen M.

2003-01-01

We describe the temporal development of the plasma composition in a pulsed plasma stream generated by cathodic arc. Cathodes of Zr and Cr were operated at various nitrogen pressures. The time-resolved plasma composition for the cathode materials was analyzed with time-of-flight charge-to-mass spectrometry, and was found to be a strong function of the nitrogen pressure. Large plasma composition gradients were detected within the first 60 μs of the pulse, the nitrogen ion concentration increasing with increasing pressure. The results are explained by the formation and erosion of a compound layer formed at the cathode surface in the presence of a reactive gas. The average charge state was also found to be affected by the reactive gas pressure as well as by the time after ignition. The charge states were highest in the beginning of the pulse at low nitrogen pressure, decreasing to a steady-state value at higher pressure. These results are of importance for reactive plasma processing and for controlling the evolution of thin film composition and microstructure

Physics of Plasma Cathode Current Injection During LHI

Science.gov (United States)

Hinson, E. T.; Barr, J.; Bongard, M.; Burke, M. G.; Fonck, R.; Perry, J.

2015-11-01

Localized helicity injection (LHI) ST startup employs current sources at the tokamak edge. Max Ip in LHI scales with injection voltage Vinj, requiring an understanding of injector impedance. For the arc-plasma cathode electron injectors in Pegasus, impedance is plasma-determined, and typically Vinj>1kV for Iinj = 2kA. At low Iinj, Iinj Vinj3 / 2 , an indication of a double layer (DL) common to such devices. However, at Iinj> 1kA, Iinj Vinj1 / 2 occurs, a scaling expected for limited launched beam density, nb ≡Iinj / (e√{ 2eVinj /me }Ainj) Iinj /Vinj1 / 2 . An ohmic discharge injection target was created to test this hypothesis. Langmuir probe data showed Iinj/Vinj1 / 2 nedge at low nedge, consistent with a limit (nedge >=ne , b) imposed by quasineutrality. If edge fueling maintained nedge >=ne , b , spectroscopic measurements of source density narc indicated Iinj/Vinj1 / 2 narc , as expected from DL expansion. Thus nb established by narc or nedge determines Vinj up to the onset of cathode spot (CS) arcing. Technology development has increased obtainable Vinj and reduced CS damage using new ring shielding and a cathode design drawing CS's away from insulators. This involved a novel optimization of conical frustum geometry. Finally, consistent with NIMROD predictions of coherent streams in the edge during LHI, pairwise triangulation of outboard Mirnov data assuming beam m =1 motion has allowed an estimate of beam R(t), Z(t) location that is near the injector R, and consistent across the array. Supported by U.S. DOE Grant DE-FG02-96ER54375.

Plasma assisted heat treatment: annealing

International Nuclear Information System (INIS)

Brunatto, S F; Guimaraes, N V

2009-01-01

This work comprises a new dc plasma application in the metallurgical-mechanical field, called plasma assisted heat treatment, and it presents the first results for annealing. Annealing treatments were performed in 90% reduction cold-rolled niobium samples at 900 deg. C and 60 min, in two different heating ways: (a) in a hollow cathode discharge (HCD) configuration and (b) in a plasma oven configuration. The evolution of the samples' recrystallization was determined by means of the microstructure, microhardness and softening rate characterization. The results indicate that plasma species (ions and neutrals) bombardment in HCD plays an important role in the recrystallization process activation and could lead to technological and economical advantages considering the metallic materials' heat treatment application. (fast track communication)

A study of plasma parameters in hollow cathode plasma jet in pulse regime

Czech Academy of Sciences Publication Activity Database

Kudrna, P.; Klusoň, J.; Leshkov, S.; Chichina, M.; Picková, I.; Hubička, Zdeněk; Tichý, M.

2010-01-01

Roč. 50, č. 9 (2010), s. 886-891 ISSN 0863-1042 R&D Projects: GA ČR GA202/09/0800 Institutional research plan: CEZ:AV0Z10100522 Keywords : thin-films * system * deposition * RF * nitride Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.006, year: 2010

Transport and turbulence in a magnetized argon plasma

International Nuclear Information System (INIS)

Vogels, J.M.M.J.

1984-01-01

Three aspects of the longitudinal motion of ionized and neutral particles in a hollow cathode arc are investigated. The longitudinal plasma momentum balance of the column has been investigated, we have studied the momentum balance in relation to turbulence and we have investigated the source properties of the cathode. The study of the plasma momentum balance contains two aspects: (1) to collect experimental data on ion drift velocities and temperatures with Fabry-Perot interferometry, on electron densities and temperatures with Thomson scattering or optical spectroscopy and on neutral densities with a collisional radiative model combined with the ion energy balance; (2) to check the (classical) theory of the momentum balance with these data. The coupling between these aspects has been investigated and found to be in good agreement. (Auth.)

Cold plasmas

International Nuclear Information System (INIS)

Franz, G.

1990-01-01

This textbook discusses the following topics: Phenomenological description of a direct current glow discharge; the plasma (temperature distribution and measurement, potential variation, electron energy distribution function, charge neutralization, wall potentials, plasma oscillations); Production of charge carriers (ions, electrons, ionization in the cathode zone, negative glowing zone, Faraday dark space, positive column, anode zone, hollow cathode discharges); RF-discharges (charge carrier production, RF-Shields, scattering mechanisms); Sputtering (ion-surface interaction, kinetics, sputtering yield and energy distribution, systems and conditions, film formation and stresses, contamination, bias techniques, multicomponent film deposition, cohesion, magnetrons, triode systems, plasma enhanced chemical vapor deposition); Dry etching (sputter etching, reactive etching, topography, process control, quantitative investigations); Etching mechanisms (etching of Si and SiO 2 with CF 4 , of III/V-compound-semiconductors, combination of isotrope and anisotrope etching methods, surface cleaning); ion beam systems (applications, etching); Dyclotron-resonance-systems (electron cyclotron resonance systems, whistler-sources and 'resonant inductive plasma etching'); Appendix (electron energy distribution functions, Bohm's transition zone, plasma oscillations, scattering cross sections and mean free path, metastable states, Child-Langmuir-Schottky equation, loss mechanisms, charge carrier distribution in the positive column, breakdown at high frequencies, motion in a magnetic field, skin depth of an electric field for a HF-discharge, whistler waves, dispersion relations for plane wave propagation). (orig.) With 138 figs

Analysis of cathode geometry to minimize cathode erosion in direct current microplasma jet

Energy Technology Data Exchange (ETDEWEB)

Causa, Federica [Dipartimento di Scienze dell' Ambiente, della Sicurezza, del Territorio, degli Alimenti e della Salute, Universita degli studi di Messina, 98122 Messina (Italy); Ghezzi, Francesco; Caniello, Roberto; Grosso, Giovanni [Istituto di Fisica del Plasma, Consiglio Nazionale delle Ricerche, EURATOM-ENEA-CNR Association, Via R. Cozzi 53, 20125 Milano (Italy); Dellasega, David [Istituto di Fisica del Plasma, Consiglio Nazionale delle Ricerche, EURATOM-ENEA-CNR Association, Via R. Cozzi 53, 20125 Milano (Italy); Dipartimento di Energia, Politecnico di Milano, Via Ponzio 34/3, 20133 Milano (Italy)

2012-12-15

Microplasma jets are now widely used for deposition, etching, and materials processing. The present study focuses on the investigation of the influence of cathode geometry on deposition quality, for microplasma jet deposition systems in low vacuum. The interest here is understanding the influence of hydrogen on sputtering and/or evaporation of the electrodes. Samples obtained with two cathode geometries with tapered and rectangular cross-sections have been investigated experimentally by scanning electron microscopy and energy dispersion X-ray spectroscopy. Samples obtained with a tapered-geometry cathode present heavy contamination, demonstrating cathode erosion, while samples obtained with a rectangular-cross-section cathode are free from contamination. These experimental characteristics were explained by modelling results showing a larger radial component of the electric field at the cathode inner wall of the tapered cathode. As a result, ion acceleration is larger, explaining the observed cathode erosion in this case. Results from the present investigation also show that the ratio of radial to axial field components is larger for the rectangular geometry case, thus, qualitatively explaining the presence of micro-hollow cathode discharge over a wide range of currents observed in this case. In the light of the above findings, the rectangular cathode geometry is considered to be more effective to achieve cleaner deposition.

Plasma source ion implantation of metal ions: Synchronization of cathodic-arc plasma production and target bias pulses

International Nuclear Information System (INIS)

Wood, B.P.; Reass, W.A.; Henins, I.

1995-01-01

An erbium cathodic-arc has been installed on a Plasma Source Ion Implantation (PSII) experiment to allow the implantation of erbium metal and the growth of adherent erbia (erbium oxide) films on a variety of substrates. Operation of the PSII pulser and the cathodic-arc are synchronized to achieve pure implantation, rather than the hybrid implantation/deposition being investigated in other laboratories. The relative phase of the 20 μs PSII and cathodic-arc pulses can to adjusted to tailor the energy distribution of implanted ions and suppress the initial high-current drain on the pulse modulator. The authors present experimental data on this effect and make a comparison to results from particle-in-cell simulations

Metal-Organic Framework-Derived Reduced Graphene Oxide-Supported ZnO/ZnCo2O4/C Hollow Nanocages as Cathode Catalysts for Aluminum-O2 Batteries.

Science.gov (United States)

Liu, Yisi; Jiang, Hao; Hao, Jiayu; Liu, Yulong; Shen, Haibo; Li, Wenzhang; Li, Jie

2017-09-20

Aluminum-air battery is a promising candidate for large-scale energy applications because of its low cost and high energy density. Remarkably, tremendous efforts have been concentrated on developing efficient and stable cathode electrocatalysts toward the oxygen reduction reaction. In this work, a hydrothermal-calcination approach was utilized to prepare novel reduced graphene oxide (rGO)-supported hollow ZnO/ZnCo 2 O 4 nanoparticle-embedded carbon nanocages (ZnO/ZnCo 2 O 4 /C@rGO) using a zeolitic imidazolate framework (ZIF-67)/graphene oxide/zinc nitrate composite as the precursor. The ZnO/ZnCo 2 O 4 /C@rGO hybrid exhibits remarkable electrocatalytic performance for oxygen reduction reaction under alkaline conditions and superior stability and methanol tolerance to those of the commercial Pt/C catalyst. Furthermore, novel and simple Al-air coin cells were first fabricated using the hybrid materials as cathode catalysts under ambient air conditions to further investigate their catalytic performance. The coin cell with the ZnO/ZnCo 2 O 4 /C@rGO cathode catalyst displays a higher open circuit voltage and discharge voltage and more sluggish potential drop than those of the cell with the ZnO/ZnCo 2 O 4 /C cathode catalyst, which confirms that rGO can enhance the electrocatalytic activity and stability of the catalyst system. The excellent electrocatalytic performance of the ZnO/ZnCo 2 O 4 /C@rGO hybrid is attributed to the prominent conductivity and high specific surface area resulting from rGO, the more accessible catalytic active sites induced by the unique porous hollow nanocage structure, and synergic covalent coupling between rGO sheets and ZnO/ZnCo 2 O 4 /C nanocages.

Mass spectrometer diagnostic technique in the study of stationary afterglow plasmas in helium, argon and krypton

International Nuclear Information System (INIS)

Langenwalter, M.

1979-01-01

Since some years the method of massspectrometric monitoring has become an important tool in the analysis of time resolved (or stationary) afterglow plasmas. The present thesis reports the construction and testing of a new fully bakeable UHV-stationary-afterglow-apparatus using a hollow cathode discharge as plasma source for the first time. The hollow cathode is moveable perpendicular to its axis relative to the sampling orifice (i.e. a very small hole at the centre of the plasma container's boundary), so that the radical distribution of the charged particle density can be studied. Several specific extraction conditions for ions from the plasma especially the sampling probe potential have been systematically investigated. Results are illustrated and discussed. The new apparatus has been tested by determining the ambipolar diffusion coefficient of the molecular ion He 2 + in a pure Helium-plasma in thermal equilibrium. The present result (Dsub(a2) = 603 +- 38 / P 0 cm 2 s -1 ) is in agreement with results reported by other workers. Finally an example for the radial behaviour of the Ar + -sampling current in an Argon-discharge for several different times in the afterglow period is given. The shown behaviour agrees relatively well with the theoretically predicted radial ion density distribution, i.e. the zero-order Ressel'function. (Author)

TRACE ANALYSIS BY LASER-EXCITED ATOMIC FLUORESCENCE WITH ATOMIZATION IN A PULSED PLASMA

OpenAIRE

Lunyov , O.; Oshemkov , S.; Petrov , A.

1991-01-01

The possibilities of plasma atomization for laser fluorescence trace analysis are discussed. Pulsed hot hollow cathode discharge was used for analysis of solutions and powdered samples. The high voltage spark and laser-induced breakdown (laser spark) were used as atomizers of metal-containing atmospheric aerosols. Detection limits were improved by means of temporal background selection.

Hollow-cathode lamps as optical frequency standards: the influence of optical imaging on the line-strength ratios

Science.gov (United States)

Huke, Philipp; Tal-Or, Lev; Sarmiento, Luis Fernando; Reiners, Ansgar

2016-07-01

Hollow cathode discharge lamps (HCLs) have been successfully used in recent years as calibration sources of optical astronomical spectrographs. The numerous narrow metal lines have stable wavelengths, which makes them well suited for m/s calibration accuracy of high-resolution spectrographs, while the buffer-gas lines are less stable and less useful. Accordingly, an important property is the metal-to-gas line-strength ratio (Rmetal/gas). Processes inside the lamp cause the light to be emitted from different regions between the cathode and the anode leaing to the emission of different beams with different values of Rmetal/gas. We used commercially- available HCLs to measure and characterize these beams with respect to their spatial distribution, their angle of propagation relative to the optical axis, and their values of Rmetal/gas. We conclude that a good imaging of an HCL into a fiber-fed spectrograph would consist of an aperture close to its front window in order to filter out the parts of the beam with low Rmetal/gas, and of a lens to collimate the important central beam. We show that Rmetal/gas can be further improved with only minor adjustments of the imaging parameters, and that the imaging scheme that yields the highest Rmetal/gas does not necessarily provide the highest flux.

MODULATED PLASMA ELECTRON BEAMS

Energy Technology Data Exchange (ETDEWEB)

Stauffer, L. H.

1963-08-15

Techniques have been developed for producing electron beams of two amperes or more, from a plasma within a hollow cathode. Electron beam energies of 20 kilovolts are readily obtained and power densities of the order of 10,000 kilowatts per square inch can be obtained with the aid of auxiliary electromagnetic focusing. An inert gas atmosphere of a few microns pressure is used to initiate and maintain the beam. Beam intensity increases with both gas pressure and cathode potential but may be controlled by varying the potential of an internal electrode. Under constant pressure and cathode potential the beam intensity may be varied over a wide range by adjusting the potential of the internal control electrode. The effects of cathode design on the volt-ampere characteristics of the beam and the design of control electrodes are described. Also, performance data in both helium and argon are given. A tentative theory of the origin of electrons and of beam formation is proposed. Applications to vacuum metallurgy and to electron beam welding are described and illustrated. (auth)

Inflight dissociation of zircon in air plasma

Energy Technology Data Exchange (ETDEWEB)

Yugeswaran, S; Selvarajan, V [Bharathiar University, Coimbatore 641046 (India); Ananthapadmanabhan, P V; Thiyagarajan, T K [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai - 400 085 (India); Nair, Janardhanan [Ion Arc Technologies Pvt Ltd, Coimbatore (India)

2010-02-01

Thermal dissociation of zircon can be conveniently carried out in a plasma reactor, which is characterized by high temperature, high energy density and high quench rate. Zirconia is recovered from this partially dissociated zircon by alkali leaching. Dissociation of zircon has been conventionally carried out in argon gas, which is expensive. The present paper reports experimental results on thermal dissociation of zircon in air plasma medium. Process simulation for 'inflight' dissociation of zircon in air plasma medium is also presented. The experimental system consists of a central hollow graphite electrode, which acts as the cathode and a graphite anode. The material to be processed is fed centrally through the cathode. The unique feature of the system is that it uses air as the working gas to generate the thermal plasma. The system has been used to study in-flight dissociation of zircon in the thermal plasma jet. Dissociation was carried out over 10-25 kW power range. Results of the study indicate that complete dissociation of zircon to ZrO{sub 2} and silica could be accomplished at 25 kW in air plasma.

Inflight dissociation of zircon in air plasma

International Nuclear Information System (INIS)

Yugeswaran, S; Selvarajan, V; Ananthapadmanabhan, P V; Thiyagarajan, T K; Nair, Janardhanan

2010-01-01

Thermal dissociation of zircon can be conveniently carried out in a plasma reactor, which is characterized by high temperature, high energy density and high quench rate. Zirconia is recovered from this partially dissociated zircon by alkali leaching. Dissociation of zircon has been conventionally carried out in argon gas, which is expensive. The present paper reports experimental results on thermal dissociation of zircon in air plasma medium. Process simulation for 'inflight' dissociation of zircon in air plasma medium is also presented. The experimental system consists of a central hollow graphite electrode, which acts as the cathode and a graphite anode. The material to be processed is fed centrally through the cathode. The unique feature of the system is that it uses air as the working gas to generate the thermal plasma. The system has been used to study in-flight dissociation of zircon in the thermal plasma jet. Dissociation was carried out over 10-25 kW power range. Results of the study indicate that complete dissociation of zircon to ZrO 2 and silica could be accomplished at 25 kW in air plasma.

Study of the feasibility of distributed cathodic arc as a plasma source for development of the technology for plasma separation of SNF and radioactive wastes

Energy Technology Data Exchange (ETDEWEB)

Amirov, R. Kh.; Vorona, N. A.; Gavrikov, A. V.; Liziakin, G. D.; Polistchook, V. P.; Samoylov, I. S.; Smirnov, V. P.; Usmanov, R. A., E-mail: ravus46@yandex.ru; Yartsev, I. M. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

2015-12-15

One of the key problems in the development of plasma separation technology is designing a plasma source which uses condensed spent nuclear fuel (SNF) or nuclear wastes as a raw material. This paper covers the experimental study of the evaporation and ionization of model materials (gadolinium, niobium oxide, and titanium oxide). For these purposes, a vacuum arc with a heated cathode on the studied material was initiated and its parameters in different regimes were studied. During the experiment, the cathode temperature, arc current, arc voltage, and plasma radiation spectra were measured, and also probe measurements were carried out. It was found that the increase in the cathode heating power leads to the decrease in the arc voltage (to 3 V). This fact makes it possible to reduce the electron energy and achieve singly ionized plasma with a high degree of ionization to fulfill one of the requirements for plasma separation of SNF. This finding is supported by the analysis of the plasma radiation spectrum and the results of the probe diagnostics.

Excited argon 1s5 production in micro-hollow cathode discharges for use as potential rare gas laser sources

Science.gov (United States)

Peterson, Richard D.; Eshel, Ben; Rice, Christopher A.; Perram, Glen P.

2018-02-01

The diode-pumped rare gas laser (DPRGL) has been suggested as a potential high-gain, high-energy laser which requires densities on the order of 1013 cm-3 at pressures around 1 atmosphere for efficient operation. Argon 1s5 number densities have been measured in micro-hollow cathode discharges with electrode gaps of 127 and 254 μm and hole diameters from 100-400 μm. The dependency of the metastable argon (1s5) density on total gas pressure, electrode gap distance and hole diameter were explored. The measured densities were all in the range of 0.5 - 2 × 1013 cm-3 with the 400 μm hole diameters being the lowest.

Comparative analysis of turbulent effects on thermal plasma characteristics inside the plasma torches with rod- and well-type cathodes

International Nuclear Information System (INIS)

Hur, Min; Hong, Sang Hee

2002-01-01

The thermal plasma characteristics inside the two non-transferred plasma torches with rod-type cathode (RTC) and well-type cathode (WTC) are analysed in conjunction with turbulent effects on them in the atmospheric-pressure conditions. A control volume method and a modified semi-implicit pressure linked equations revised algorithm are used for solving the governing equations, i.e. conservation equations of mass, momentum, and energy together with a current continuity equation for arc discharge. A cold flow analysis is introduced to find the cathode spot position in the WTC torch, and both the laminar and turbulent models are employed to gain a physical insight into the turbulent effects on the thermal plasma characteristics produced inside the two torches. The numerical analysis for an RTC torch shows that slightly different values of plasma temperature and velocity between the laminar and turbulent calculations occur and the radial temperature profiles are constricted at the axis with increasing the gas flow rate, and that the large turbulent viscosities appear mostly near the anode wall. These calculated results indicate that the turbulent effects on the thermal plasma characteristics are very weak in the whole discharge region inside the RTC torch. On the other hand, the calculated results of the two numerical simulations for a WTC torch present that the significantly different values of plasma characteristics between the two models appear in the whole torch region and the plasma temperatures decrease with increasing the gas flow rate because the relatively strong turbulent effects are prevailing in the entire interior region of the WTC torch. From the comparisons of plasma net powers calculated and measured in this work, the turbulent modelling turns out to provide the more accurately calculated results close to the measured ones compared with the laminar one, especially for the torch with WTC. This is because the turbulent effects are considerably strong in

Effect of Si on DC arc plasma generation from Al-Cr and Al-Cr-Si cathodes used in oxygen

Science.gov (United States)

Zhirkov, I.; Landälv, L.; Göthelid, E.; Ahlgren, M.; Eklund, P.; Rosen, J.

2017-02-01

Al2O3 alloyed with Cr is an important material for the tooling industry. It can be synthesized from an arc discharge using Al-Cr cathodes in an oxygen atmosphere. Due to formation of Al-rich oxide islands on the cathode surface, the arc process stability is highly sensitive to oxygen pressure. For improved stability, the use of Al0.70Cr0.25Si0.05 cathodes has previously been suggested, where Si may reduce island formation. Here, we have investigated the effect of Si by comparing plasma generation and thin film deposition from Al0.7Cr0.3 and Al0.7Cr0.25Si0.05 cathodes. Plasma ion composition, ion energies, ion charge states, neutral species, droplet formation, and film composition have been characterized at different O2 flow rates for arc currents of 60 and 90 A. Si and related compounds are detected in plasma ions and in plasma neutrals. Scanning electron microscopy and energy dispersive X-ray analysis show that the cathode composition and the film composition are the same, with Si present in droplets as well. The effect of Si on the process stability, ion energies, and ion charge states is found to be negligible compared to that of the arc current. The latter is identified as the most relevant parameter for tuning the properties of the reactive discharge. The present work increases the fundamental understanding of plasma generation in a reactive atmosphere, and provides input for the choice of cathode composition and process parameters in reactive DC arc synthesis.

Research on an improved explosive emission cathode

International Nuclear Information System (INIS)

Liu Guozhi; Sun Jun; Shao Hao; Chen Changhua; Zhang Xiaowei

2009-01-01

This paper presents a physical description of the cathode plasma process of an explosive emission cathode (EEC) and experimental results on a type of oil-immersed graphite EEC. It is believed that the generation of a cathode plasma is mainly dependent on the state of the cathode surface, and that adsorbed gases and dielectrics on the cathode surface play a leading role in the formation of the cathode plasma. Based on these ideas, a type of oil-immersed graphite EEC is proposed and fabricated. The experiments indicate that the oil-immersed cathodes have improved emissive properties and longer lifetimes.

Vacuum arc plasma generation and thin film deposition from a TiB{sub 2} cathode

Energy Technology Data Exchange (ETDEWEB)

Zhirkov, Igor, E-mail: igozh@ifm.liu.se; Petruhins, Andrejs; Naslund, Lars-Ake; Rosen, Johanna [Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Kolozsvári, Szilard; Polcik, Peter [PLANSEE Composite Materials GmbH, Siebenbürgerstraße 23, 86983 Lechbruck am See (Germany)

2015-11-02

We have studied the utilization of TiB{sub 2} cathodes for thin film deposition in a DC vacuum arc system. We present a route for attaining a stable, reproducible, and fully ionized plasma flux of Ti and B by removal of the external magnetic field, which leads to dissipation of the vacuum arc discharge and an increased active surface area of the cathode. Applying a magnetic field resulted in instability and cracking, consistent with the previous reports. Plasma analysis shows average energies of 115 and 26 eV, average ion charge states of 2.1 and 1.1 for Ti and B, respectively, and a plasma ion composition of approximately 50% Ti and 50% B. This is consistent with measured resulting film composition from X-ray photoelectron spectroscopy, suggesting a negligible contribution of neutrals and macroparticles to the film growth. Also, despite the observations of macroparticle generation, the film surface is very smooth. These results are of importance for the utilization of cathodic arc as a method for synthesis of metal borides.

Cathode erosion in a high-pressure high-current arc: calculations for tungsten cathode in a free-burning argon arc

International Nuclear Information System (INIS)

Nemchinsky, Valerian

2012-01-01

The motion of an evaporated atom of the cathode material in a near-cathode plasma is considered. It is shown that the evaporated atom is ionized almost instantly. The created ion, under the influence of a strong electric field existing in the cathode proximity, has a high probability of returning to the cathode. A small fraction of evaporated atoms are able to diffuse away from the cathode to the region where they are involved in plasma flow and lose their chance to return to the cathode. The fraction of the total evaporated atoms, which do not return to the cathode, the escape factor, determines the net erosion rate. In order to calculate this factor, the distributions of the plasma parameters in the near-cathode plasma were considered. Calculations showed that the escape factor is on the order of a few per cent. Using experimental data on the plasma and cathode temperatures, we calculated the net erosion rate for a free-burning 200 A argon arc with a thoriated tungsten cathode. The calculated erosion rate is close to 1 µg s -1 , which is in agreement with available experimental data. (paper)

Electron beam generation form a superemissive cathode

International Nuclear Information System (INIS)

Hsu, T.-Y.; Liou, R.-L.; Kirkman-Amemiya, G.; Gundersen, M.A.

1991-01-01

An experimental study of electron beams produced by a superemissive cathode in the Back-Lighted Thyratron (BLT) and the pseudospark is presented. This work is motivated by experiments demonstrating very high current densities (≥10 kA/cm 2 over an area of 1 cm 2 ) from the pseudospark and BLT cathode. This high-density current is produced by field-enhanced thermionic emission from the ion beam-heated surface of a molybdenum cathode. This work reports the use of this cathode as a beam source, and is to be distinguished from previous work reporting hollow cathode-produced electron beams. An electron beam of more than 260 A Peak current has been produced with 15 kV applied voltage. An efficiency of ∼10% is estimated. These experimental results encourage further investigation of the super-emissive cathode as an intense electron beam source for applications including accelerator technology

Comparative study of two- and three-dimensional modeling on arc discharge phenomena inside a thermal plasma torch with hollow electrodes

International Nuclear Information System (INIS)

Kim, Keun Su; Park, Jin Myung; Choi, Sooseok; Kim, Jongin; Hong, Sang Hee

2008-01-01

A comparative study between two- and three-dimensional (2D and 3D) modeling is carried out on arc discharge phenomena inside a thermal plasma torch with hollow electrodes, in order to evaluate the effects of arc root configuration characterized by either 2D annular or 3D highly localized attachment on the electrode surface. For this purpose, a more precise 3D transient model has been developed by taking account of 3D arc current distribution and arc root rotation. The 3D simulation results apparently reveal that the 3D arc root attachment brings about the inherent 3D and turbulence nature of plasma fields inside the torch. It is also found that the constricted arc column near the vortex chamber plays an important role in heating and acceleration of injected arc gases by concentrating arc currents on the axis of the hollow electrodes. The inherent 3D nature of arc discharge is well preserved inside the cathode region, while these 3D features slowly diminish behind the vortex chamber where the turbulent flow begins to be developed in the anode region. Based on the present simulation results, it is noted that the mixing effects of the strong turbulent flow on the heat and mass transfer are mainly responsible for the gradual relaxation of the 3D structures of plasma fields into the 2D axisymmetric ones that eventually appear in the anode region near the torch exit. From a detailed comparison of the 3D results with the 2D ones, the arc root configuration seems to have a significant effect on the heat transfer to the electrode surfaces interacting with the turbulent plasma flow. That is, in the 2D simulation based on an axisymmetric stationary model, the turbulence phenomena are fairly underestimated and the amount of heat transferred to the cold anode wall is calculated to be smaller than that obtained in the 3D simulation. For the validation of the numerical simulations, calculated plasma temperatures and axial velocities are compared with experimentally measured ones

Hollow cylindrical plasma filament waveguide with discontinuous finite thickness cladding

International Nuclear Information System (INIS)

Alshershby, Mostafa; Hao Zuoqiang; Lin Jingquan

2013-01-01

We have explored here a hollow cylindrical laser plasma multifilament waveguide with discontinuous finite thickness cladding, in which the separation between individual filaments is in the range of several millimeters and the waveguide cladding thickness is in the order of the microwave penetration depth. Such parameters give a closer representation of a realistic laser filament waveguide sustained by a long stable propagation of femtosecond (fs) laser pulses. We report how the waveguide losses depend on structural parameters like normalized plasma filament spacing, filament to filament distance or pitch, normal spatial frequency, and radius of the plasma filament. We found that for typical plasma parameters, the proposed waveguide can support guided modes of microwaves in extremely high frequency even with a cladding consisting of only one ring of plasma filaments. The loss of the microwave radiation is mainly caused by tunneling through the discontinuous finite cladding, i.e., confinement loss, and is weakly dependent on the plasma absorption. In addition, the analysis indicates that the propagation loss is fairly large compared with the loss of a plasma waveguide with a continuous infinite thickness cladding, while they are comparable when using a cladding contains more than one ring. Compared to free space propagation, this waveguide still presents a superior microwave transmission to some distance in the order of the filamentation length; thus, the laser plasma filaments waveguide may be a potential channel for transporting pulsed-modulated microwaves if ensuring a long and stable propagation of fs laser pulses.

Spatial structure of radio frequency ring-shaped magnetized discharge sputtering plasma using two facing ZnO/Al2O3 cylindrical targets for Al-doped ZnO thin film preparation

Directory of Open Access Journals (Sweden)

Takashi Sumiyama

2017-05-01

Full Text Available Spatial structure of high-density radio frequency ring-shaped magnetized discharge plasma sputtering with two facing ZnO/Al2O3 cylindrical targets mounted in ring-shaped hollow cathode has been measured and Al-doped ZnO (AZO thin film is deposited without substrate heating. The plasma density has a peak at ring-shaped hollow trench near the cathode. The radial profile becomes uniform with increasing the distance from the target cathode. A low ion current flowing to the substrate of 0.19 mA/cm2 is attained. Large area AZO films with a resistivity of 4.1 – 6.7×10-4 Ω cm can be prepared at a substrate room temperature. The transmittance is 84.5 % in a visible region. The surface roughnesses of AZO films are 0.86, 0.68, 0.64, 1.7 nm at radial positions of r = 0, 15, 30, 40 mm, respectively, while diffraction peak of AZO films is 34.26°. The grains exhibit a preferential orientation along (002 axis.

Modification of low temperature deposited LiMn2O4 thin film cathodes by oxygen plasma irradiation

International Nuclear Information System (INIS)

Chen, Chen Chung; Chiu, Kuo-Feng; Lin, Kun Ming; Lin, Hsin Chih

2009-01-01

Lithium manganese oxides have been deposited by radio frequency magnetron sputter deposition with relatively lower annealing temperatures and then post-treated with a radio frequency (rf) driven oxygen plasma. Following oxygen plasma irradiation, the film properties were modified, and the performance of the thin film cathode has been enhanced. The electrochemical properties of the treated thin-film cathodes were characterized and compared. The results showed that the samples with moderate plasma treatment also maintained good cyclic properties as cycled at a wide range potential window of 2.0 V-4.5 V. Its electrochemical properties were significantly improved by this process, even though the films were prepared under low annealing temperature.

Fluid and gyrokinetic modelling of particle transport in plasmas with hollow density profiles

International Nuclear Information System (INIS)

Tegnered, D; Oberparleiter, M; Nordman, H; Strand, P

2016-01-01

Hollow density profiles occur in connection with pellet fuelling and L to H transitions. A positive density gradient could potentially stabilize the turbulence or change the relation between convective and diffusive fluxes, thereby reducing the turbulent transport of particles towards the center, making the fuelling scheme inefficient. In the present work, the particle transport driven by ITG/TE mode turbulence in regions of hollow density profiles is studied by fluid as well as gyrokinetic simulations. The fluid model used, an extended version of the Weiland transport model, Extended Drift Wave Model (EDWM), incorporates an arbitrary number of ion species in a multi-fluid description, and an extended wavelength spectrum. The fluid model, which is fast and hence suitable for use in predictive simulations, is compared to gyrokinetic simulations using the code GENE. Typical tokamak parameters are used based on the Cyclone Base Case. Parameter scans in key plasma parameters like plasma β, R/L T , and magnetic shear are investigated. It is found that β in particular has a stabilizing effect in the negative R/L n region, both nonlinear GENE and EDWM show a decrease in inward flux for negative R/L n and a change of direction from inward to outward for positive R/L n . This might have serious consequences for pellet fuelling of high β plasmas. (paper)

[Reparative regeneration of rat skin under influence of hollow cathode lamp (HCL) with manganese and copper line spectrum emission].

Science.gov (United States)

Mel'nikova, V I; Izvol'skaia, M S; Voronova, S N; Sharipova, M M; Rukin, E M; Zakharova, L A

2010-01-01

Influence of local light exposure by hollow cathode lamp with typical manganese and copper (HCL-Mn, Cu) line emission spectrum on posttraumatic regeneration rate of rat skin has been investigated. We performed the comparative analysis of the morphology and the differentiation ability of rat skin on the 15th and 24th days after full-thickness skin wound had been inflicted on rat dorsums. On the 15th day after injury, the experimental group (daily 30 s exposure for two weeks) showed scab loss, re-epithelialization, and hair regrowth, in contrast to the control rats, where scabs were still observed on the 24th day. Histological analysis revealed that in contrast to the control group the treatment with HCL-Mn, Cu resulted in the increased number of hair follicles and sebaceous glands, the decreased number of blood vessels and horizontal orientation of collagen fibers. The immunohistochemistry for OX-62 revealed that the number of dermal dendritic cells in the experimental groups was maximal on the 15th day, and then decreased to the 24th day after injury. The number of dermal dendritic cells was significantly lower in the control group. The immunohistochemistry for pan-keratins in the control animals revealed a high number of cells expressing different types of keratins, distributed in the main part of the epidermis on the 15th day after surgery, whereas in the experimental group the number of such cells was significantly lower and the cells were concentrated more close to the external part of the epidermis. The number of cells stained for keratin 19 was higher in the experimental group on the 15th day after surgery, whereas this number decreased in this group on the 24th day after surgery as compared to the control group. Thus, typical manganese and copper line spectrum emission emitted by hollow cathode lamp stimulates innate immunity, accelerates restoration of derma, skin epithelium and other skin derivates, and stimulates wound healing in general.

Hierarchical Li1.2Mn0.54Ni0.13Co0.13O2 hollow spherical as cathode material for Li-ion battery

Science.gov (United States)

Zhang, Yu; Zhu, Tianjiao; Lin, Liu; Yuan, Mengwei; Li, Huifeng; Sun, Genban; Ma, Shulan

2017-11-01

Lithium-rich manganese-based layered materials have been considered as the most promising cathode materials for future high-energy-density lithium-ion batteries. However, a great loss of irreversible capacity at the initial cycle, poor cycle stability, and rate performance severely restrict its application. Herein, we develop a new strategy to synthesize hierarchical hollow Li1.2Mn0.54Ni0.13Co0.13O2 microspheres using sucrose and cetyltrimethylammonium bromide as a soft template combined with hydrothermal assisted homogeneous precipitation method. The hollow microspheres are assembled by the primary particles with the size of 50 nm. As a result, the as-prepared material exhibits high reversible capacity, good cycling stability, and excellent rate property. It delivers a high initial discharge capacity of 305.9 mAh g-1 at 28 mA g-1 with coulombic efficiency of 80%. Even at high current density of 560 mA g-1, the sample also shows a stable discharge capacity of 215 mAh g-1. The enhanced electrochemical properties are attributed to the stable hierarchical hollow sphere structure and the appropriate contact area between electrode and electrolyte, thus effectively improve the lithium-ion intercalation and deintercalation kinetics. [Figure not available: see fulltext.

Propagation characteristics of atmospheric-pressure He+O{sub 2} plasmas inside a simulated endoscope channel

Energy Technology Data Exchange (ETDEWEB)

Wang, S.; Chen, Z. Y.; Wang, X. H., E-mail: xhw@mail.xjtu.edu.cn; Li, D.; Yang, A. J.; Liu, D. X.; Rong, M. Z. [State Key Laboratory of Electrical Insulation and Power Equipment, Centre for Plasma Biomedicine, Xi' an Jiaotong University, Xi' an 710049 (China); Chen, H. L. [Frank Reidy Center for Bioelectrics, Old Dominion University, Norfolk, Virginia 23508 (United States); Kong, M. G. [State Key Laboratory of Electrical Insulation and Power Equipment, Centre for Plasma Biomedicine, Xi' an Jiaotong University, Xi' an 710049 (China); Frank Reidy Center for Bioelectrics, Old Dominion University, Norfolk, Virginia 23508 (United States); Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, Virginia 23529 (United States)

2015-11-28

Cold atmospheric-pressure plasmas have potential to be used for endoscope sterilization. In this study, a long quartz tube was used as the simulated endoscope channel, and an array of electrodes was warped one by one along the tube. Plasmas were generated in the inner channel of the tube, and their propagation characteristics in He+O{sub 2} feedstock gases were studied as a function of the oxygen concentration. It is found that each of the plasmas originates at the edge of an instantaneous cathode, and then it propagates bidirectionally. Interestingly, a plasma head with bright spots is formed in the hollow instantaneous cathode and moves towards its center part, and a plasma tail expands through the electrode gap and then forms a swallow tail in the instantaneous anode. The plasmas are in good axisymmetry when [O{sub 2}] ≤ 0.3%, but not for [O{sub 2}] ≥ 1%, and even behave in a stochastic manner when [O{sub 2}] = 3%. The antibacterial agents are charged species and reactive oxygen species, so their wall fluxes represent the “plasma dosage” for the sterilization. Such fluxes mainly act on the inner wall in the hollow electrode rather than that in the electrode gap, and they get to the maximum efficiency when the oxygen concentration is around 0.3%. It is estimated that one can reduce the electrode gap and enlarge the electrode width to achieve more homogenous and efficient antibacterial effect, which have benefits for sterilization applications.

Evaluation of an inductively-coupled plasma with an extended-sleeve torch as an atomization cell for laser-excited fluorescence spectrometry.

Science.gov (United States)

Kosinski, M A; Uchida, H; Winefordner, J D

1983-05-01

An inductively-coupled plasma (ICP) with an extended-sleeve torch has been evaluated as an atomization cell for laser-excited fluorescence spectrometry. Limits of detection for 20 lines are given. The detection power is almost equivalent to that obtained by excitation with a hollow-cathode lamp. Interelement effects and spectral interferences are discussed.

Plasma self-oscillations in the temperature-limited current regime of a hot cathode discharge

International Nuclear Information System (INIS)

Arnas Capeau, C.; Bachet, G.; Doveil, F.

1995-01-01

Experimental observations of self-oscillations occurring in the so-called ''temperature-limited current regime'' of a hot cathode discharge are presented. Their frequency and amplitude are strongly dependent on the discharge parameters. The scaling laws of their variation and an example of a period-doubling route to chaos are reported. A two probe experiment showing that the plasma behavior is closely related to the hot cathode sheath stability is also reported. copyright 1995 American Institute of Physics

Effects of fast monoenergetic electrons on the ion dynamics near the cathode in a pulsed direct current plasma sheath

International Nuclear Information System (INIS)

Sharifian, M.; Shokri, B.

2008-01-01

A detailed one-dimensional simulation of the ion dynamics of the plasma sheath near a substrate (cathode) in the presence of fast monoenergetic electrons has been carried out in this article. The sheath evolution is investigated by using a fluid model assuming that the ions, plasma electrons and monoenergetic, fast electrons act as three fluids (fluid approach). The effect of the density of fast electrons on the ion density, ion velocity, and ion energy near the cathode and the evolution of the sheath boundary in front of the cathode are separately explored. Also, the variation of the ion velocity and ion density at the vicinity of the cathode as a function of time is investigated in the absence and presence of the electron beam. Results indicate that the presence of fast electrons in the sheath causes significant change in the sheath thickness and therefore basically changes the ion velocity, ion density, and ion impact energy on the cathode compared to the absence of the electron beam case

Plasma contactor development for Space Station

Science.gov (United States)

Patterson, Michael J.; Hamley, John A.; Sarmiento, Charles J.; Manzella, David H.; Sarver-Verhey, Timothy; Soulas, George C.; Nelson, Amy

1993-01-01

Plasma contactors have been baselined for the Space Station (SS) to control the electrical potentials of surfaces to eliminate/mitigate damaging interactions with the space environment. The system represents a dual-use technology which is a direct outgrowth of the NASA electric propulsion program and, in particular, the technology development effort on ion thrustor systems. The plasma contactor subsystems include the plasma contactor unit, a power electronics unit, and an expellant management unit. Under this pre-flight development program these will all be brought to breadboard or engineering model status. Development efforts for the plasma contactor include optimizing the design and configuration of the contactor, validating its required lifetime, and characterizing the contactor plume and electromagnetic interference. The plasma contactor unit design selected for the SS is an enclosed keeper, xenon hollow cathode plasma source. This paper discusses the test results and development status of the plasma contactor unit subsystem for the SS.

High-resolution X-ray spectroscopy of hollow atoms created in plasma heated by subpicosecond laser radiation

International Nuclear Information System (INIS)

Faenov, A.Ya.; Magunov, A.I.; Pikuz, T.A.

1997-01-01

The investigations of ultrashort (0.4-0.6 ps) laser pulse radiation interaction with solid targets have been carried out. The Trident subpicosecond laser system was used for plasma creation. The X-ray plasma emission was investigated with the help of high-resolution spectrographs with spherically bent mica crystals. It is shown that when high contrast ultrashort laser pulses were used for plasma heating its emission spectra could not be explained in terms of commonly used theoretical models, and transitions in so called hollow atoms must be taken into account for adequate description of plasma radiation

Beam-plasma interaction in a cold-cathodes penning discharge; Interaction faisceau-plasma dans une decharge penning a cathodes froides

Energy Technology Data Exchange (ETDEWEB)

Bliman, S L [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1966-06-01

The H.F. emissions from a cold-cathode reflex discharge are studied. An experimental law for the frequency variation shows that f{alpha}V{sup 1/2} discharged if B{sub 0} and p are constant. If B{sub 0} is made to increase, the frequencies change such that f{sub ce} - f emitted / f{sub ce} decreases. With each emitted frequency there is associated a stationary wave system making it possible to measure the phase velocity V{phi} of the waves. This phase velocity is always close to that of the fast electrons accelerated by a potential V discharge. A non-quasistatic formalism for the propagation of waves in a beam-plasma system is then established. The Maxwell equations are solved taking into account boundary conditions. Comparison of these experiments with the theory shows a satisfactory agreement. (author) [French] On etudie les emissions H.F. d'une decharge reflex a cathodes froides. Une loi experimentale de variation des frequences montre que f{alpha}V{sup 1/2} decharge, si B{sub 0} et p sont fixes. Si on fait croitre B{sub 0}, les frequences evoluent de sorte que f{sub ce} - f emise / f{sub ce} diminue. A chaque frequence emise est associe un systeme d'ondes stationnaires qui permet la mesure de la vitesse de phase V{phi} des ondes. Cette vitesse de phase est toujours voisine de celle des electrons rapides acceleres sous la tension V decharge. On etablit ensuite un formalisme non quasistatique de propagation d'ondes dans un systeme faisceau plasma. On resoud les equations de MAXWELL avec conditions aux limites. La comparaison des experiences a la theorie aboutit a un accord satisfaisant. (auteur)

Beam-plasma interaction in a cold-cathodes penning discharge; Interaction faisceau-plasma dans une decharge penning a cathodes froides

Energy Technology Data Exchange (ETDEWEB)

Bliman, S.L. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1966-06-01

The H.F. emissions from a cold-cathode reflex discharge are studied. An experimental law for the frequency variation shows that f{alpha}V{sup 1/2} discharged if B{sub 0} and p are constant. If B{sub 0} is made to increase, the frequencies change such that f{sub ce} - f emitted / f{sub ce} decreases. With each emitted frequency there is associated a stationary wave system making it possible to measure the phase velocity V{phi} of the waves. This phase velocity is always close to that of the fast electrons accelerated by a potential V discharge. A non-quasistatic formalism for the propagation of waves in a beam-plasma system is then established. The Maxwell equations are solved taking into account boundary conditions. Comparison of these experiments with the theory shows a satisfactory agreement. (author) [French] On etudie les emissions H.F. d'une decharge reflex a cathodes froides. Une loi experimentale de variation des frequences montre que f{alpha}V{sup 1/2} decharge, si B{sub 0} et p sont fixes. Si on fait croitre B{sub 0}, les frequences evoluent de sorte que f{sub ce} - f emise / f{sub ce} diminue. A chaque frequence emise est associe un systeme d'ondes stationnaires qui permet la mesure de la vitesse de phase V{phi} des ondes. Cette vitesse de phase est toujours voisine de celle des electrons rapides acceleres sous la tension V decharge. On etablit ensuite un formalisme non quasistatique de propagation d'ondes dans un systeme faisceau plasma. On resoud les equations de MAXWELL avec conditions aux limites. La comparaison des experiences a la theorie aboutit a un accord satisfaisant. (auteur)

Enhanced propagation for relativistic laser pulses in inhomogeneous plasmas using hollow channels.

Science.gov (United States)

Fuchs, J; d'Humières, E; Sentoku, Y; Antici, P; Atzeni, S; Bandulet, H; Depierreux, S; Labaune, C; Schiavi, A

2010-11-26

The influence of long (several millimeters) and hollow channels, bored in inhomogeneous ionized plasma by using a long pulse laser beam, on the propagation of short, ultraintense laser pulses has been studied. Compared to the case without a channel, propagation in channels significantly improves beam transmission and maintains a beam quality close to propagation in vacuum. In addition, the growth of the forward-Raman instability is strongly reduced. These results are beneficial for the direct scheme of the fast ignitor concept of inertial confinement fusion as we demonstrate, in fast-ignition-relevant conditions, that with such channels laser energy can be carried through increasingly dense plasmas close to the fuel core with minimal losses.

Effects of cathode pulse at low frequency on the structure and composition of plasma electrolytic oxidation ceramic coatings

International Nuclear Information System (INIS)

Yao Zhongping; Xu Yongjun; Jiang Zhaohua; Wang Fuping

2009-01-01

The aim of this work is to investigate the effects of the cathode pulse under the low working frequency on the structure and the composition of the ceramic coatings on Ti-6Al-4V alloys by plasma electrolytic oxidation (PEO). Ceramic coatings were prepared on Ti alloy by pulsed bi-polar plasma electrolytic oxidation in NaAlO 2 solution. The phase composition, morphology, and element distribution in the coating were investigated by X-ray diffractometry, scanning electron microscopy, and energy distribution spectroscopy. The coating was mainly composed of a large amount of Al 2 TiO 5 and a little α-Al 2 O 3 and rutile TiO 2 . Increasing the cathode pulse, the amount of rutile TiO 2 was increased while the amount of Al 2 O 3 was decreased; and decreasing the cathode pulse, the amount of Al 2 O 3 was increased while the amount of rutile TiO 2 was decreased. The thickness of the coatings was increased and then decreased with the increase of the cathode pulse. The grain sizes of Al 2 TiO 5 were increased with the cathode current densities, but changed little with the cathode pulse width. The grain size of α-Al 2 O 3 was decreased with the decrease of the cathode pulse, while the grain size of TiO 2 was increased with the increase of the cathode pulse. The proper cathode pulse was helpful to reduce the roughness and to increase the density of the coatings.

Development of Polysulfone Hollow Fiber Porous Supports for High Flux Composite Membranes: Air Plasma and Piranha Etching

Directory of Open Access Journals (Sweden)

Ilya Borisov

2017-02-01

Full Text Available For the development of high efficiency porous supports for composite membrane preparation, polysulfone (PSf hollow fiber membranes (outer diameter 1.57 mm, inner diameter 1.12 mm were modified by air plasma using the low temperature plasma treatment pilot plant which is easily scalable to industrial level and the Piranha etch (H2O2 + H2SO4. Chemical and plasma modification affected only surface layers and did not cause PSf chemical structure change. The modifications led to surface roughness decrease, which is of great importance for further thin film composite (TFC membranes fabrication by dense selective layer coating, and also reduced water and ethylene glycol contact angle values for modified hollow fibers surface. Furthermore, the membranes surface energy increased two-fold. The Piranha mixture chemical modification did not change the membranes average pore size and gas permeance values, while air plasma treatment increased pore size 1.5-fold and also 2 order enhanced membranes surface porosity. Since membranes surface porosity increased due to air plasma treatment the modified membranes were used as efficient supports for preparation of high permeance TFC membranes by using poly[1-(trimethylsilyl-1-propyne] as an example for selective layer fabrication.

High-quality electron beam generation in a proton-driven hollow plasma wakefield accelerator

Science.gov (United States)

Li, Y.; Xia, G.; Lotov, K. V.; Sosedkin, A. P.; Hanahoe, K.; Mete-Apsimon, O.

2017-10-01

Simulations of proton-driven plasma wakefield accelerators have demonstrated substantially higher accelerating gradients compared to conventional accelerators and the viability of accelerating electrons to the energy frontier in a single plasma stage. However, due to the strong intrinsic transverse fields varying both radially and in time, the witness beam quality is still far from suitable for practical application in future colliders. Here we demonstrate the efficient acceleration of electrons in proton-driven wakefields in a hollow plasma channel. In this regime, the witness bunch is positioned in the region with a strong accelerating field, free from plasma electrons and ions. We show that the electron beam carrying the charge of about 10% of 1 TeV proton driver charge can be accelerated to 0.6 TeV with a preserved normalized emittance in a single channel of 700 m. This high-quality and high-charge beam may pave the way for the development of future plasma-based energy frontier colliders.

Investigations of the cathode region of an argon arc plasma by degenerate four-wave mixing laser spectroscopy and optical emission spectroscopy

International Nuclear Information System (INIS)

Dzierzega, K; Pokrzywka, B; Pellerin, S

2004-01-01

Degenerate four-wave mixing (DFWM) laser spectroscopy was used in local studies of atmospheric pressure argon plasma generated in a free-burning arc. The results of plasma diagnostics using the DFWM method were compared to the results obtained with optical emission measurements. In the cathode region of the arc the maxima of both the DFWM signal and the emission coefficient for the 696.5 nm Ar I line depend on the distance from the cathode tip. This effect proves the departure of the plasma state from local thermal equilibrium (LTE) as it has been reported by many authors. On the other hand the Stark shifts of the 696.5 nm Ar I line determined by the DFWM method in relation to plasma diagnostic results show no deviations from LTE on the arc axis down to 1.0 mm from the cathode tip

Solvothermal synthesis and electrochemical performance of hollow LiFePO{sub 4} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Zheng, Zhenmiao [School of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Pang, Wei Kong [Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia); Australian Nuclear Science and Technology Organization, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Tang, Xincun, E-mail: tangxincun@163.com [School of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Jia, Dianzeng; Huang, Yudai [Institute of Applied Chemistry, Xinjiang University, Urumqi 840046 (China); Guo, Zaiping [Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia)

2015-08-15

Highlights: • Hollow LiFePO{sub 4} nanoparticles were successfully synthesized via solvothermal method. • The shorter b lattice parameter allows the shorter diffusion path of lithium ion. • Hollow LiFePO{sub 4} nanoparticles show better rate capability than solid LiFePO{sub 4}. - Abstract: Hollow LiFePO{sub 4} nanoparticles were synthesized via a solvothermal technique, using ammonium tartrate as additive and carbon source, and ethylene glycol/water as solvent. The as-prepared samples were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, scanning and transmission electron microscopies, and Brunauer–Emmett–Teller specific surface area measurements. The electrochemical properties of the LiFePO{sub 4} cathode were examined in coin-type cell configuration and the cathode exhibited excellent rate capability (i.e., discharge capacity of 120.9 mA h g{sup −1} at 10 C) and cycling performance (i.e., >98% of capacity retention rate after 50 cycles). It is believed that the enhanced performance is correlated to the hollow structure, small crystallite and particle sizes, and relatively shorter lattice parameter b.

Experimental investigation of a 1 kA/cm² sheet beam plasma cathode electron gun.

Science.gov (United States)

Kumar, Niraj; Pal, Udit Narayan; Pal, Dharmendra Kumar; Prajesh, Rahul; Prakash, Ram

2015-01-01

In this paper, a cold cathode based sheet-beam plasma cathode electron gun is reported with achieved sheet-beam current density ∼1 kA/cm(2) from pseudospark based argon plasma for pulse length of ∼200 ns in a single shot experiment. For the qualitative assessment of the sheet-beam, an arrangement of three isolated metallic-sheets is proposed. The actual shape and size of the sheet-electron-beam are obtained through a non-conventional method by proposing a dielectric charging technique and scanning electron microscope based imaging. As distinct from the earlier developed sheet beam sources, the generated sheet-beam has been propagated more than 190 mm distance in a drift space region maintaining sheet structure without assistance of any external magnetic field.

Plasma Deposition of Oxide-Coated Cathodes

National Research Council Canada - National Science Library

Umstattd, Ryan

1998-01-01

...; such cathodes may also have applicability for lower current density continuous wave devices. This novel approach to manufacturing an oxide cathode eliminates the binders that may subsequently (and unpredictably...

'Quasi-plasma' transport model in deuterium overloaded palladium cathodes

International Nuclear Information System (INIS)

Ninno, A. de; Violante, V.

1993-01-01

The Pd-D system has been described assuming a two-population model. A 'quasi-plasma' delocalized boson gas picture has been used for the deuterons exceeding the stoichiometric ratio in Pd-D compounds. A mathematical model supported by a numerical computer code with distributed parameters has been developed in order to describe the evolution of the deuteron concentration profile inside a Pd cathode under pulsed electrolysis. Several boundary conditions have been taken into account. A strong correlation has been found between the model system evolution and the experimental data. (author)

Hollow-cathode electrode for high-power, high-pressure discharge devices

Science.gov (United States)

Chang, J.J.; Alger, T.W.

1995-08-22

Several different cold cathode configurations are disclosed for a gas discharge device each having a plurality of grooves of selected spacing, depth and width to improve the emission of electrons in a gas discharge device. Each of the cold cathode configurations can be machined from a single piece of a selected material. Several of the configurations can be assembled with individual elements which is easily seen from the various figures. 8 figs.

The effect of cathode surface impurities on gap closure

International Nuclear Information System (INIS)

Hinshelwood, D.D.

1983-01-01

Gap closure due to cathode (or anode) plasma motion is often the principal limitation on the pulse length of intense beam diodes and magnetically insulated transmission lines. Since the plasma expansion velocity is typically on the order of the sound speed, a high atomic number plasma is desirable. In recent experiments performed on a Sandia Nereus accelerator (240kV, 50kA, 3-30kA/cm 2 , 70ns) with a parallel plate diode, the cathode plasma was seen to be composed of both the cathode substrate material and constituents (hydrogen and carbon) of surface contaminants such as pump oils. The plasma expansion velocities, inferred from impedance measurements, were 1.5-2 cm/μs and were the same for carbon, aluminum and stainless steel cathodes. This similarity, combined with the temperature estimates of 2-3eV obtained from spectroscopy, implied that the expansion was due to protons from surface contaminants. Similar results were reported from studies of ablatively driven plasmas. In a continuation of the work, the results of time and spatially resolved spectroscopic studies of plasma formed on aluminum cathodes, yielding measurements of the expansion velocities of different components of the cathode plasma, are presented. We have heated stainless steel cathodes in situ to 700 0 C. The Hα line emission was seen to decrease by more than an order of magnitude (becoming lost in the background) when the cathodes were heated but no change in the impedance behavior was observed. Evidently the heating was insufficient to remove the last monolayer, which should contain more than enough hydrogen to close the gap. Preliminary experiments with gold-plated cathodes (which should be more resistant to chemisorption) yielded similar results. Further measurements of plasma formed on heated cathodes are presented

Control of ordered mesoporous titanium dioxide nanostructures formed using plasma enhanced glancing angle deposition

Energy Technology Data Exchange (ETDEWEB)

Gibson, Des [Institute of Thin Films, Sensors & Imaging, Scottish Universities Physics Alliance, University of West of Scotland, Paisley, PA1 2BE (United Kingdom); Child, David, E-mail: david.child@uws.ac.uk [Institute of Thin Films, Sensors & Imaging, Scottish Universities Physics Alliance, University of West of Scotland, Paisley, PA1 2BE (United Kingdom); Song, Shigeng; Zhao, Chao [Institute of Thin Films, Sensors & Imaging, Scottish Universities Physics Alliance, University of West of Scotland, Paisley, PA1 2BE (United Kingdom); Alajiani, Yahya [Institute of Thin Films, Sensors & Imaging, Scottish Universities Physics Alliance, University of West of Scotland, Paisley, PA1 2BE (United Kingdom); Department of Physics, Faculty of Science, Jazan University, Jazan (Saudi Arabia); Waddell, Ewan [Thin Film Solutions Ltd, West of Scotland Science Park, Glasgow, G20 0TH (United Kingdom)

2015-10-01

Three dimensional nanostructures of mesoporous (pore diameter between 2-50 nm) nanocrystalline titania (TiO{sub 2}) were produced using glancing angle deposition combined with plasma ion assisted deposition, providing plasma enhanced glancing angle deposition eliminating the need for post-annealing to achieve film crystallinity. Electron beam evaporation was chosen to deposit nanostructures at various azimuthal angles, achieving designed variation in three dimensional nanostructure. A thermionic broad beam hollow cathode plasma source was used to enhance electron beam deposition, with ability to vary in real time ion fluxes and energies providing a means to modify and control TiO{sub 2} nanostructure real time with controlled density and porosity along and lateral to film growth direction. Plasma ion assisted deposition was carried out at room temperature using a hollow cathode plasma source, ensuring low heat loading to the substrate during deposition. Plasma enhanced glancing angle TiO{sub 2} structures were deposited onto borosilicate microscope slides and used to characterise the effects of glancing angle and plasma ion energy distribution function on the optical and nanostructural properties. Variation in TiO{sub 2} refractive index from 1.40 to 2.45 (@ 550 nm) using PEGLAD is demonstrated. Results and analysis of the influence of plasma enhanced glancing angle deposition on evaporant path and resultant glancing angle deviation from standard GLAD are described. Control of mesoporous morphology is described, providing a means of optimising light trapping features and film porosity, relevant to applications such as fabrication of dye sensitised solar cells. - Highlights: • Plasma assistance during glancing angle deposition enables control of morphology. • Ion energy variation during glancing angle deposition varies columnar angle • Column thickness of glancing angle deposition dependant on ion current density • Ion current density variation during

The Interaction of C-Band Microwaves with Large Plasma Sheets

International Nuclear Information System (INIS)

Ding Liang; Huo Wenqing; Yang Xinjie; Xu Yuemin

2012-01-01

A large plasma sheet 60 cm×60 cm×2 cm in size was generated using a hollow cathode, and measurements were conducted for interactions including transmission, reflection and absorption. With different discharge parameters, plasma sheets can vary and influence microwave strength. Microwave reflection decreases when the discharge current rises, and the opposite occurs in transmission. The C-band microwave is absorbed when it is propagated through large plasma sheets at higher pressure. When plasma density and collision frequency are fitted with incident microwave frequency, a large amount of microwave energy is consumed. Reflection, transmission and absorption all exist simultaneously. Plasma sheets are an attractive alternative to microwave steering at low pressure, and the microwave reflection used in receiving radar can be altered by changing the discharge parameters.

Real-time imaging, spectroscopy, and structural investigation of cathodic plasma electrolytic oxidation of molybdenum

Energy Technology Data Exchange (ETDEWEB)

Stojadinović, Stevan, E-mail: sstevan@ff.bg.ac.rs; Tadić, Nenad; Šišović, Nikola M.; Vasilić, Rastko [Faculty of Physics, University of Belgrade, Studentski trg 12-16, 11000 Belgrade (Serbia)

2015-06-21

In this paper, the results of the investigation of cathodic plasma electrolytic oxidation (CPEO) of molybdenum at 160 V in a mixed solution of borax, water, and ethylene glycol are presented. Real-time imaging and optical emission spectroscopy were used for the characterization of the CPEO. During the process, vapor envelope is formed around the cathode and strong electric field within the envelope caused the generation of plasma discharges. The spectral line shape analysis of hydrogen Balmer line H{sub β} (486.13 nm) shows that plasma discharges are characterized by the electron number density of about 1.4 × 10{sup 21 }m{sup −3}. The electron temperature of 15 000 K was estimated by measuring molybdenum atomic lines intensity. Surface morphology, chemical, and phase composition of coatings formed by CPEO were characterized by scanning electron microscopy with energy dispersive x-ray spectroscopy and x-ray diffraction. The elemental components of CPEO coatings are Mo and O and the predominant crystalline form is MoO{sub 3}.

Plasma parameters of the cathode spot explosive electron emission cell obtained from the model of liquid-metal jet tearing and electrical explosion

Science.gov (United States)

Tsventoukh, M. M.

2018-05-01

A model has been developed for the explosive electron emission cell pulse of a vacuum discharge cathode spot that describes the ignition and extinction of the explosive pulse. The pulse is initiated due to hydrodynamic tearing of a liquid-metal jet which propagates from the preceding cell crater boundary and draws the ion current from the plasma produced by the preceding explosion. Once the jet neck has been resistively heated to a critical temperature (˜1 eV), the plasma starts expanding and decreasing in density, which corresponds to the extinction phase. Numerical and analytical solutions have been obtained that describe both the time behavior of the pulse plasma parameters and their average values. For the cell plasma, the momentum per transferred charge has been estimated to be some tens of g cm/(s C), which is consistent with the known measurements of ion velocity, ion erosion rate, and specific recoil force. This supports the model of the pressure-gradient-driven plasma acceleration mechanism for the explosive cathode spot cells. The ohmic electric field within the explosive current-carrying plasma has been estimated to be some tens of kV/cm, which is consistent with the known experimental data on cathode potential fall and explosive cell plasma size. This supports the model that assumes the ohmic nature of the cathode potential fall in a vacuum discharge.

Melting experiment on concrete waste using a hollow type plasma torch mounted on furnace

International Nuclear Information System (INIS)

Moon, Y. P.; Kim, T. W.; Kim, H. S.; Shin, S. U.; Lee, M. C.

2000-01-01

A furnace coupled with a hollow type plasma torch was manufactured and installed in order to develop a volume reduction technology for non-combustible radioactive waste using plasma. A melting test with 10kg of concrete waste was carried out for the evaluation of melting characteristics in the non-transferred operation mode for 20 minutes with the melter. Feeded concrete was completely melted. However, the molten bath was not easily discharged because of its high viscosity. It was found that some molten slag spat from the molten bath was coated on the surface of torch which was mounted vertically inside furnace

Application of electron beam equipment based on a plasma cathode gun in additive technology

Science.gov (United States)

Galchenko, N. K.; Kolesnikova, K. A.; Semenov, G. V.; Rau, A. G.; Raskoshniy, S. Y.; Bezzubko, A. V.; Dampilon, B. V.; Sorokova, S. N.

2016-11-01

The paper discusses the application of electron beam equipment based on a plasma cathode gun for three-dimensional surface modification of metals and alloys. The effect of substrate surface preparation on the adhesion strength of gas thermal coatings has been investigated.

Early results of microwave transmission experiments through an overly dense rectangular plasma sheet with microparticle injection

Energy Technology Data Exchange (ETDEWEB)

Gillman, Eric D., E-mail: eric.gillman.ctr@nrl.navy.mil [National Research Council Postdoctoral Associate at the U.S. Naval Research Laboratory, Washington, DC 20375 (United States); Amatucci, W. E. [U.S. Naval Research Laboratory, Washington, DC 20375 (United States)

2014-06-15

These experiments utilize a linear hollow cathode to create a dense, rectangular plasma sheet to simulate the plasma layer surrounding vehicles traveling at hypersonic velocities within the Earth's atmosphere. Injection of fine dielectric microparticles significantly reduces the electron density and therefore lowers the electron plasma frequency by binding a significant portion of the bulk free electrons to the relatively massive microparticles. Measurements show that microwave transmission through this previously overly dense, impenetrable plasma layer increases with the injection of alumina microparticles approximately 60 μm in diameter. This method of electron depletion is a potential means of mitigating the radio communications blackout experienced by hypersonic vehicles.

Study of the use of an electric discharge for hollow cathodes used as optical excitation sources in the spectrographic measurement of fluorine in thorium, uranium and plutonium; Etude de l'utilisation de la decharge electrique en cathode creuse comme source d'excitation optique pour le dosage spectrographique du fluor dans le thorium, l'uranium et le plutonium

Energy Technology Data Exchange (ETDEWEB)

Bufpereau, M; Crehange, G; Poublan, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1964-07-01

Previous works and phenomena concerned with a hollow cathode excitation are reviewed. Experiments aimed specially on the determination of the best conditions for an analysis of fluorine in oxides-metals and solutions. In that purpose, several factors have been pointed out. One started some researches about others elements that fluorine. Carrying fluorine into discharge and excitation have been more specially studied. A quantitative analysis method is given. The analysis limit is 45 ppm about but the detection limit is 5 ppm about. As a conclusion, various ways for optical excitation of fluorine are reviewed as other analytical possibilities a hollow cathode discharge offers. (authors) [French] On rappelle les travaux effectues jusqu'alors ainsi que les phenomenes mis en jeu dans l'excitation cathode creuse. Les experiences effectuees ont eu pour but essentiel la determination des conditions optima du dosage du fluor dans les oxydes, metaux et solutions. Pour cela de nombreux facteurs ont ete mis en evidence. Certaines etudes concernant d'autres elements que le fluor ont ete amorcees. Le passage du fluor dans la decharge et son excitation ont ete plus particulierement etudies. Une methode d'analyse quantitative est degagee, la limite de dosage est de l'ordre de 45 ppm, la limite de detection de 5 ppm. En conclusion, on passe en revue les differentes methodes d'excitation optique du fluor ainsi que les autres possibilites analytiques que peut offrir la cathode creuse. (auteurs)

Experimental research on time-resolved evolution of cathode plasma expansion velocity in a long pulsed magnetically insulated coaxial diode

Science.gov (United States)

Zhu, Danni; Zhang, Jun; Zhong, Huihuang; Ge, Xingjun; Gao, Jingming

2018-02-01

Unlike planar diodes, separate research of the axial and radial plasma expansion velocities is difficult for magnetically insulated coaxial diodes. Time-resolved electrical diagnostic which is based on the voltage-ampere characteristics has been employed to study the temporal evolution of the axial and radial cathode plasma expansion velocities in a long pulsed magnetically insulated coaxial diode. Different from a planar diode with a "U" shaped profile of temporal velocity evolution, the temporal evolution trend of the axial expansion velocity is proved to be a "V" shaped profile. Apart from the suppression on the radial expansion velocity, the strong magnetic field is also conducive to slowing down the axial expansion velocity. Compared with the ordinary graphite cathode, the carbon velvet and graphite composite cathode showed superior characteristics as judged by the low plasma expansion velocity and long-term electrical stability as a promising result for applications where long-pulsed and reliable operation at high power is required.

Determination of plasma spot current and arc discharge plasma current on the system of plasma cathode electron sources using Rogowski coil technique

International Nuclear Information System (INIS)

Wirjoadi; Bambang Siswanto; Lely Susita RM; Agus Purwadi; Sudjatmoko

2015-01-01

It has been done the function test experiments of ignitor electrode system and the plasma generator electrode system to determine the current spot plasma and arc discharge plasma current with Rogowski coil technique. Ignitor electrode system that gets power supply from IDPS system can generate the plasma spot current of 11.68 ampere to the pulse width of about 33 μs, this value is greater than the design probably because of electronic components used in the IDPS system was not as planned. For the plasma generator electrode system that gets power from ADPS system capable of producing an arc discharge plasma current around 103.15 amperes with a pulse width of about 96 μs, and this value as planned. Based on the value of the arc discharge plasma current can be determined plasma electron density, which is about 10.12 10"1"9 electrons/m"3, and with this electron density value, an ignitor electrode system and a plasma generator system is quite good if used as a plasma cathode electron source system. (author)

Development of a Power Electronics Unit for the Space Station Plasma Contactor

Science.gov (United States)

Hamley, John A.; Hill, Gerald M.; Patterson, Michael J.; Saggio, Joseph, Jr.; Terdan, Fred; Mansell, Justin D.

1994-01-01

A hollow cathode plasma contactor has been baselined as a charge control device for the Space Station (SS) to prevent deleterious interactions of coated structural components with the ambient plasma. NASA LeRC Work Package 4 initiated the development of a plasma contactor system comprised of a Power Electronics Unit (PEU), an Expellant Management Unit (EMU), a command and data interface, and a Plasma Contactor Unit (PCU). A breadboard PEU was designed and fabricated. The breadboard PEU contains a cathode heater and discharge power supply, which were required to operate the PCU, a control and auxiliary power converter, an EMU interface, a command and telemetry interface, and a controller. The cathode heater and discharge supplies utilized a push-pull topology with a switching frequency of 20 kHz and pulse-width-modulated (PWM) control. A pulse ignition circuit derived from that used in arcjet power processors was incorporated in the discharge supply for discharge ignition. An 8088 based microcontroller was utilized in the breadboard model to provide a flexible platform for controller development with a simple command/data interface incorporating a direct connection to SS Mulitplexer/Demultiplexer (MDM) analog and digital I/O cards. Incorporating this in the flight model would eliminate the hardware and software overhead associated with a 1553 serial interface. The PEU autonomously operated the plasma contactor based on command inputs and was successfully integrated with a prototype plasma contactor unit demonstrating reliable ignition of the discharge and steady-state operation.

Joule heat generation in thermionic cathodes of high-pressure arc discharges

Energy Technology Data Exchange (ETDEWEB)

Benilov, M. S.; Cunha, M. D. [Departamento de Fisica, CCCEE, Universidade da Madeira, Largo do Municipio, 9000 Funchal (Portugal)

2013-02-14

The nonlinear surface heating model of plasma-cathode interaction in high-pressure arcs is extended to take into account the Joule effect inside the cathode body. Calculation results are given for different modes of current transfer to tungsten cathodes of different configurations in argon plasmas of atmospheric or higher pressures. Special attention is paid to analysis of energy balances of the cathode and the near-cathode plasma layer. In all the cases, the variation of potential inside the cathode is much smaller than the near-cathode voltage drop. However, this variation can be comparable to the volt equivalent of the energy flux from the plasma to the cathode and then the Joule effect is essential. Such is the case of the diffuse and mixed modes on rod cathodes at high currents, where the Joule heating causes a dramatic change of thermal and electrical regimes of the cathode. The Joule heating has virtually no effect over characteristics of spots on rod and infinite planar cathodes.

Erythrocyte-like hollow carbon capsules and their application in proton exchange membrane fuel cells.

Science.gov (United States)

Kim, Jung Ho; Yu, Jong-Sung

2010-12-14

Hierarchical nanostructured erythrocyte-like hollow carbon (EHC) with a hollow hemispherical macroporous core of ca. 230 nm in diameter and 30-40 nm thick mesoporous shell was synthesized and explored as a cathode catalyst support in a proton exchange membrane fuel cell (PEMFC). The morphology control of EHC was successfully achieved using solid core/mesoporous shell (SCMS) silica template and different styrene/furfuryl alcohol mixture compositions by a nanocasting method. The EHC-supported Pt (20 wt%) cathodes prepared have demonstrated markedly enhanced catalytic activity towards oxygen reduction reactions (ORRs) and greatly improved PEMFC polarization performance compared to carbon black Vulcan XC-72 (VC)-supported ones, probably due to the superb structural characteristics of the EHC such as uniform size, well-developed porosity, large specific surface area and pore volume. In particular, Pt/EHC cathodes exhibited ca. 30-60% higher ORR activity than a commercial Johnson Matthey Pt catalyst at a low catalyst loading of 0.2 mg Pt cm(-2).

Pulsed Electron Source with Grid Plasma Cathode and Longitudinal Magnetic Field for Modification of Material and Product Surfaces

Science.gov (United States)

Devyatkov, V. N.; Koval, N. N.

2018-01-01

The description and the main characteristics of the pulsed electron source "SOLO" developed on the basis of the plasma cathode with grid stabilization of the emission plasma boundary are presented. The emission plasma is generated by a low-pressure arc discharge, and that allows to form the dense low-energy electron beam with a wide range of independently adjustable parameters of beam current pulses (pulse duration of 20-250 μs, pulse repetition rate of 1-10 s-1, amplitude of beam current pulses of 20-300 A, and energy of beam electrons of 5-25 keV). The special features of generation of emission plasma by constricted low-pressure arc discharge in the grid plasma cathode partially dipped into a non-uniform magnetic field and of formation and transportation of the electron beam in a longitudinal magnetic field are considered. The application area of the electron source and technologies realized with its help are specified.

Grid system design on the plasma cathode electron source

International Nuclear Information System (INIS)

Agus Purwadi

2014-01-01

It has been designed the grid system on the Plasma Cathode Electron Source (PCES). Grid system with the electron emission hole of (15 x 60) cm 2 , the single aperture grid size of (0,5 x O,5) mm 2 and the grid wire diameter of 0,25 mm, will be used on the plasma generator chamber. If the sum of grid holes known and the value of electron emission current through every the grid hole known too then the total value of electron emission Current which emits from the plasma generator chamber can be determined It has been calculated the value of electron emission current I e as function of the grid radius r e =(0.28, 0.40, 0.49, 0.56, 0.63, 0.69) mm on the electron temperature of T e = 5 eV for varying of the value plasma electron densities n e = (10 15 , 10 16 , 10 17 , 10 18 ) m -3 . Also for the value of electron emission current fe as function of the grid radius r e = (0.28, 0.40, 0.49. 0.56, 0.63,0.69) mm on the electron density n e = 10 17 m -3 for varying of the value of plasma electron temperatures T e = (1, 2, 3, 4, 5) eV. electron emission current will be increase by increasing grid radius, electron temperature as well as plasma electron density. (author)

Difference-frequency laser spectroscopy of molecular ions with a hollow-cathode cell: extended analysis of the ν1 band of H2D+

International Nuclear Information System (INIS)

Amano, T.

1985-01-01

A cooled hollow-cathode cell was used for observation of the infrared spectra of positive ions in the 3-μm region with a difference-frequency laser as a radiation source. About an order-of-magnitude enhancement of the signal intensity was attained, compared with the similar signals obtained with our previous glow-discharge cell. Ten more weaker lines of the ν 1 fundamental band of H 2 D + , which could not be observed in our previous experiment [J. Chem. Phys. 81, 2869 (1984)] were measured. Improved molecular constants were obtained from a least-squares fit including the infrared lines and the two millimeter-and submillimeter-wave lines in the ground state

Investigation and optimisation of a plasma cathode electron beam gun for material processing applications

OpenAIRE

Del Pozo Rodriguez, Sofia

2016-01-01

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University London. This thesis describes design, development and testing work on a plasma cathode electron beam gun as well as plasma diagnosis experiments and Electron Beam (EB) current measurements carried out with the aim of maximising the power of the EB extracted and optimising the electron beam gun system for material processing applications. The elements which influence EB gun design are described...

Effect of cathode and anode plasma motion on current characteristics of pinch diode

International Nuclear Information System (INIS)

Yang Hailiang; Qiu Aici; Sun Jianfeng; Li Jingya; He Xiaoping; Tang Junping; Li Hongyu; Wang Haiyang; Huang Jianjun; Ren Shuqing; Yang Li; Zou Lili

2005-01-01

The preliminary research results for the effect of cathode and anode plasma motion on current characteristics of the pinch ion diode on FLASH II accelerator are reported. The structure and principle of pinch reflex ion beam diode are introduced. The time dependent evolution of electron and ion flow in large aspect-ratio relativistic diodes is studied by analytic models. The equation of Child-langmuir, weak focused-flow, strong focused-flow and parapotential flow are corrected to reduce the diode A-C gap caused by the motion of cathode and anode plasma. The diode current and ion current are calculated with these corrected equations, and the results are consistent with the experimental data. The methods of increasing ion current and efficiency are also presented. The high power ion beam peak current about 160 kA with a peak energy about 500 keV was produced using water-dielectric transmission-line generators with super-pinch reflex ion diodes on FLASH II accelerator at Northwest Institute of Nuclear Technology (NINT). (authors)

Parametric study of x-ray pre-ionizer with plasma cathode

International Nuclear Information System (INIS)

Bollanti, S.; Di Lazzaro, P.; Flora, F.; Giordano, G.; Letardi, T.; Schina, G.; Zheng, C.

1993-01-01

The construction characteristics and the performance of an x-ray diode working at 200 Hz are described. The temporal behavior of both the plasma cathode emission and the diode discharge was studied, including the measurements of vacuum effects on the repetition rate and lifetime capability, pre-ionization versus electrical features, and ionization density versus dosage. This simple and low-cost x-ray diode was used to uniformly pre-ionize a half-liter XeCl laser, delivering an output laser energy of 800 mJ/shot at a 100-Hz repetition rate

Carbon dust formation in a cold plasma from cathode sputtering

International Nuclear Information System (INIS)

Arnas, C.; Mouberi, A.; Hassouni, K.; Michau, A.; Lombardi, G.; Bonnin, X.; Benedic, F.; Pegourie, B.

2009-01-01

Nanoparticles are produced in argon glow plasmas where carbon is introduced by sputtering of a graphite cathode. A scaling law of growth is reported on as a function of the discharge time. Two successive stages of growth of concomitant agglomeration and carbon deposition are observed, followed by a final stage of growth by carbon deposition. A model of formation of molecular precursors by coagulation of neutral clusters on the one hand and of neutral-negative clusters on the other hand is presented, based on formation enthalpy and cluster geometry.

Carbon dust formation in a cold plasma from cathode sputtering

Science.gov (United States)

Arnas, C.; Mouberi, A.; Hassouni, K.; Michau, A.; Lombardi, G.; Bonnin, X.; Bénédic, F.; Pégourié, B.

2009-06-01

Nanoparticles are produced in argon glow plasmas where carbon is introduced by sputtering of a graphite cathode. A scaling law of growth is reported on as a function of the discharge time. Two successive stages of growth of concomitant agglomeration and carbon deposition are observed, followed by a final stage of growth by carbon deposition. A model of formation of molecular precursors by coagulation of neutral clusters on the one hand and of neutral-negative clusters on the other hand is presented, based on formation enthalpy and cluster geometry.

[The comparative assessment of the wound-healing effects of the treatment with the use of Bioptron, Minitag, Orion+ apparatuses and hollow cathode lamps (experimental study)].

Science.gov (United States)

Sharipova, M M; Voronova, S N; Rukin, E M; Vasilenko, A M

2011-01-01

The objective of the present experimental study was the comparative assessment of the wound-healing effects of radiation emitted from Bioptron, Minitag, Orion+ apparatuses and hollow cathode lamps (HCL). The emitters of any type were shown to be equally efficacious in that they accelerated wound epithelization by 30% on the average compared with control. Based on the difference between spectral and power characteristics of different sources of radiation and dynamics of their wound-healing efficacy (including that of two types of HCL), the authors arrived at the conclusion that the further development of the proposed approach to wound healing is a promising line of research in the field of spectral phototherapy.

Expansion of the cathode spot and generation of shock waves in the plasma of a volume discharge in atmospheric-pressure helium

International Nuclear Information System (INIS)

Omarov, O. A.; Kurbanismailov, V. S.; Arslanbekov, M. A.; Gadzhiev, M. Kh.; Ragimkhanov, G. B.; Al-Shatravi, Ali J. G.

2012-01-01

The expansion of the cathode spot and the generation of shock waves during the formation and development of a pulsed volume discharge in atmospheric-pressure helium were studied by analyzing the emission spectra of the cathode plasma and the spatiotemporal behavior of the plasma glow. The transition of a diffuse volume discharge in a centimeter-long gap into a high-current diffuse mode when the gas pressure increased from 1 to 5 atm and the applied voltage rose from the statistical breakdown voltage to a 100% overvoltage was investigated. Analytical expressions for the radius of the cathode spot and its expansion velocity obtained in the framework of a spherically symmetric model agree satisfactorily with the experimental data.

Synthesis and characterization hollow spherical La0.7Sr0.2Ca0.1Co0.9Fe0.1O3–δ (LSCCT for cathode of solid oxide fuel cell (SOFC

Directory of Open Access Journals (Sweden)

H. H. Yu

2016-10-01

Full Text Available Hollow spheres structures of La0.7Sr0.2Ca0.1Co0.9Fe0.1O3–δ (LSCCT have been synthesized via hydrothermal method using carbon spheres as template. The structure and electrical conductivity of obtained samples are characterized by X-ray diffraction (XRD, scanning electron microscope (SEM, transmission electron microscope (TEM and direct current (DC four-probe method respectively. The results show that hollow spheres structures of LSCCT with the mean particle size of 0,9 - 1,2 μm is single perovskite. The electrical conductivity of the samples is higher than 100 S/cm from 600 to 800 ℃ and can meet the demand of the electrical properties for the cathode materials.

Cathode material and pulsed plasma treatment influence on the microstructure and microhardness of high-chromium cast iron surface

Directory of Open Access Journals (Sweden)

Юлія Геннадіївна Чабак

2016-11-01

Full Text Available The article presents an analysis of the cathode material and the pulse plasma treatment mode influence on the surface microstructure and microhardness of high chrome (15% Cr cast iron. The methods of metallographic analysis and microhardness measurements were used. It has been shown that pulsed plasma treatment at 4 kV voltage with the use of the electro-axial thermal accelerator results in surface modification with high microhardness 950-1050 HV50, and in the formation of the coating due to the transfer of the electrodes material. The specific features of using different cathode materials have been systematized. It has been found that graphite electrodes are not recommended to be used due to their low strength and fracture under plasma pulses. In case of using tungsten cathode a coating of small thickness (20-30 microns and having cracks has been formed on the specimen surface. The most expedient is to apply the electrodes with low melting point (such as killed St.3, which provides a high-quality state of treated surface and formation the protective crack-free coating of 80-100 microns thick. It has been found that as a result of the plasma pulsed treatment the enrichment of coating with carbon is likely to occur that results in microhardness increase. The prospects of this technology as well as its shortcomings have been described

Plasma generator

International Nuclear Information System (INIS)

Omichi, Takeo; Yamanaka, Toshiyuki.

1976-01-01

Object: To recycle a coolant in a sealed hollow portion formed interiorly of a plasma limiter itself to thereby to cause direct contact between the coolant and the plasma limiter and increase of contact area therebetween to cool the plasma limiter. Structure: The heat resulting from plasma generated during operation and applied to the body of the plasma limiter is transmitted to the coolant, which recycles through an inlet and outlet pipe, an inlet and outlet nozzle and a hollow portion to hold the plasma limiter at a level less than a predetermined temperature. On the other hand, the heater wire is, at the time of emergency operation, energized to heat the plasma limiter, but this heat is transmitted to the limiter body to increase the temperature thereof. However, the coolant recycling the hollow portion comes into direct contact with the limiter body, and since the plasma limiter surround the hollow portion, the heat amount transmitted from the limiter body to the coolant increases to sufficiently cool the plasma limiter. (Yoshihara, H.)

Direct-current cathodic vacuum arc system with magnetic-field mechanism for plasma stabilization.

Science.gov (United States)

Zhang, H-S; Komvopoulos, K

2008-07-01

Filtered cathodic vacuum arc (FCVA) deposition is characterized by plasma beam directionality, plasma energy adjustment via substrate biasing, macroparticle filtering, and independent substrate temperature control. Between the two modes of FCVA deposition, namely, direct current (dc) and pulsed arc, the dc mode yields higher deposition rates than the pulsed mode. However, maintaining the dc arc discharge is challenging because of its inherent plasma instabilities. A system generating a special configuration of magnetic field that stabilizes the dc arc discharge during film deposition is presented. This magnetic field is also part of the out-of-plane magnetic filter used to focus the plasma beam and prevent macroparticle film contamination. The efficiency of the plasma-stabilizing magnetic-field mechanism is demonstrated by the deposition of amorphous carbon (a-C) films exhibiting significantly high hardness and tetrahedral carbon hybridization (sp3) contents higher than 70%. Such high-quality films cannot be produced by dc arc deposition without the plasma-stabilizing mechanism presented in this study.

Direct-current cathodic vacuum arc system with magnetic-field mechanism for plasma stabilization

International Nuclear Information System (INIS)

Zhang, H.-S.; Komvopoulos, K.

2008-01-01

Filtered cathodic vacuum arc (FCVA) deposition is characterized by plasma beam directionality, plasma energy adjustment via substrate biasing, macroparticle filtering, and independent substrate temperature control. Between the two modes of FCVA deposition, namely, direct current (dc) and pulsed arc, the dc mode yields higher deposition rates than the pulsed mode. However, maintaining the dc arc discharge is challenging because of its inherent plasma instabilities. A system generating a special configuration of magnetic field that stabilizes the dc arc discharge during film deposition is presented. This magnetic field is also part of the out-of-plane magnetic filter used to focus the plasma beam and prevent macroparticle film contamination. The efficiency of the plasma-stabilizing magnetic-field mechanism is demonstrated by the deposition of amorphous carbon (a-C) films exhibiting significantly high hardness and tetrahedral carbon hybridization (sp 3 ) contents higher than 70%. Such high-quality films cannot be produced by dc arc deposition without the plasma-stabilizing mechanism presented in this study

Electrodepositing of Au on hollow PS micro-spheres

International Nuclear Information System (INIS)

Sun Jingyuan; Zhang Yunwang; Du Kai; Wan Xiaobo; Xiao Jiang; Zhang Wei; Zhang Lin; Chen Jing

2010-01-01

Using the self-regulating new micro-sphere electrodepositing device, the techniques of electrodepositing gold on hollow PS micro-spheres were established. The experiment was carried out under the following conditions: voltage was about 0.7 ∼ 0.8 V, current density was 2.0 mA · cm -2 , the temperature was 45 degree C, cathode rotating rate was 250 r · min -1 , flow rate of the solution was 7 mL · min -1 · cm -2 . Hollow gold-plated micro-spheres were prepared with well spherical symmetry, uniform thickness and surface smoothness under 500 nm. The speed of the gold depositing was 6 μm · h -1 . (authors)

Enthalpy probe measurements and three-dimensional modelling on air plasma jets generated by a non-transferred plasma torch with hollow electrodes

International Nuclear Information System (INIS)

Kim, Keun Su; Park, Jin Myung; Choi, Sooseok; Kim, Jongin; Hong, Sang Hee

2008-01-01

Thermal flow characteristics of air plasma jets generated by a non-transferred plasma torch with hollow electrodes are experimentally and numerically investigated in order to provide more reliable scientific and technical information, which has been insufficient for their practical applications to material and environmental industries. In this work, a thermal plasma torch of hollow electrode type is first designed and fabricated, and similarity criteria for predicting operational conditions for the scale-up to high-power torches are derived from the arc voltage characteristics measured with various operating and geometry conditions of the torch. The thermal flow characteristics of air plasma jets ejected from the torch are measured by enthalpy probe diagnostics and turn out to have relatively low temperatures of around 3000-7000 K, but show features of other unique properties, such as high energy flux, broad high temperature region and long plasma jet with moderate axial velocity, which are promising for their applications to material syntheses and hazardous waste treatments. Such high enthalpy at a relatively low temperature of air thermal plasma compared with the argon one is due to the high thermal energy residing in the vibrational and rotational states and oxygen dissociation, besides the translational states in monatomic gases such as argon. It is expected that this high specific enthalpy of the air plasma will enable material and environmental industries to treat a large amount of precursors and waste materials effectively at a lower temperature for a longer residence time by the low plasma velocity. It is also found from the measurements that the turbulence intensity influenced by the size of the electrode diameter has a significant effect on the axial and radial profiles of plasma jet properties and that a longer plasma jet is more readily achievable with a larger electrode diameter reducing the turbulence intensity in the external region of the torch. In

Static gas-liquid interfacial direct current discharge plasmas using ionic liquid cathode

International Nuclear Information System (INIS)

Kaneko, T.; Baba, K.; Hatakeyama, R.

2009-01-01

Due to the unique properties of ionic liquids such as their extremely low vapor pressure and high heat capacity, we have succeeded in creating the static and stable gas (plasmas)-liquid (ionic liquids) interfacial field using a direct current discharge under a low gas pressure condition. It is clarified that the ionic liquid works as a nonmetal liquid electrode, and furthermore, a secondary electron emission coefficient of the ionic liquid is larger than that of conventional metal electrodes. The plasma potential structure of the gas-liquid interfacial region, and resultant interactions between the plasma and the ionic liquid are revealed by changing a polarity of the electrode in the ionic liquid. By utilizing the ionic liquid as a cathode electrode, the positive ions in the plasma region are found to be irradiated to the ionic liquid. This ion irradiation causes physical and chemical reactions at the gas-liquid interfacial region without the vaporization of the ionic liquid.

Synthesis of thick diamond films by direct current hot-cathode plasma chemical vapour deposition

CERN Document Server

Jin Zeng Sun; Bai Yi Zhen; Lu Xian Yi

2002-01-01

The method of direct current hot-cathode plasma chemical vapour deposition has been established. A long-time stable glow discharge at large discharge current and high gas pressure has been achieved by using a hot cathode in the temperature range from 1100 degree C to 1500 degree C and non-symmetrical configuration of the poles, in which the diameter of the cathode is larger than that of anode. High-quality thick diamond films, with a diameter of 40-50 mm and thickness of 0.5-4.2 mm, have been synthesized by this method. Transparent thick diamond films were grown over a range of growth rates between 5-10 mu m/h. Most of the thick diamond films have thermal conductivities of 10-12 W/K centre dot cm. The thick diamond films with high thermal conductivity can be used as a heat sink of semiconducting laser diode array and as a heat spreading and isolation substrate of multichip modules. The performance can be obviously improved

Detailed analysis of hollow ions spectra from dense matter pumped by X-ray emission of relativistic laser plasma

International Nuclear Information System (INIS)

Hansen, S. B.; Colgan, J.; Abdallah, J.; Faenov, A. Ya.; Pikuz, S. A.; Skobelev, I. Yu.; Wagenaars, E.; Culfa, O.; Dance, R. J.; Tallents, G. J.; Rossall, A. K.; Woolsey, N. C.; Booth, N.; Lancaster, K. L.; Evans, R. G.; Gray, R. J.; McKenna, P.; Kaempfer, T.; Schulze, K. S.; Uschmann, I.

2014-01-01

X-ray emission from hollow ions offers new diagnostic opportunities for dense, strongly coupled plasma. We present extended modeling of the x-ray emission spectrum reported by Colgan et al. [Phys. Rev. Lett. 110, 125001 (2013)] based on two collisional-radiative codes: the hybrid-structure Spectroscopic Collisional-Radiative Atomic Model (SCRAM) and the mixed-unresolved transition arrays (MUTA) ATOMIC model. We show that both accuracy and completeness in the modeled energy level structure are critical for reliable diagnostics, investigate how emission changes with different treatments of ionization potential depression, and discuss two approaches to handling the extensive structure required for hollow-ion models with many multiply excited configurations

Origin of microplasma instabilities during DC operation of silicon based microhollow cathode devices

Science.gov (United States)

Felix, Valentin; Lefaucheux, Philippe; Aubry, Olivier; Golda, Judith; Schulz-von der Gathen, Volker; Overzet, Lawrence J.; Dussart, Rémi

2016-04-01

The failure mechanisms of micro hollow cathode discharges (MHCD) in silicon have been investigated using their I-V characteristics, high speed photography and scanning electron microscopy. Experiments were carried out in helium. We observed I-V instabilities in the form of rapid voltage decreases associated with current spikes. The current spikes can reach values more than 100 times greater than the average MHCD current. (The peaks can be more than 1 Ampere for a few 10’s of nanoseconds.) These current spikes are correlated in time with 3-10 μm diameter optical flashes that occur inside the cavities. The SEM characterizations indicated that blister-like structures form on the Si surface during plasma operation. Thin Si layers detach from the surface in localized regions. We theorize that shallow helium implantation occurs and forms the ‘blisters’ whenever the Si is biased as the cathode. These blisters ‘explode’ when the helium pressure inside them becomes too large leading to the transient micro-arcs seen in both the optical emission and the I-V characteristics. We noted that blisters were never found on the metal counter electrode, even when it was biased as the cathode (and the Si as the anode). This observation led to a few suggestions for delaying the failure of Si MHCDs. One may coat the Si cathode (cavities) with blister resistant material; design the MHCD array to operate with the Si as the anode rather than as the cathode; or use a gas additive to prevent surface damage. Regarding the latter, tests using SF6 as the gas additive successfully prevented blister formation through rapid etching. The result was an enhanced MHCD lifetime.

Observation of interference between stark and electric quadrupole transitions in LIF from He atoms in plasmas

International Nuclear Information System (INIS)

Takiyama, K.; Namba, S.; Furukawa, S.; Oda, T.; James, B.W.; Andruczyk, D.

2004-01-01

Interference between Stark-induced dipole and electric quadrupole amplitudes was observed in a He hollow cathode plasma with axial magnetic field perpendicular to the sheath electric field E by laser-induced fluorescence (LIF) method. Circularly polarized LIF signals were observed in the sheath region. Spatial profile of the degree of polarization P c showed characteristic features of the interference. Using theoretically calculated P c -E relationship, E-profile was successfully obtained form the measure P c . (author)

Existence of a virtual cathode close to a strongly electron emissive wall in low density plasmas

Science.gov (United States)

Tierno, S. P.; Donoso, J. M.; Domenech-Garret, J. L.; Conde, L.

2016-01-01

The interaction between an electron emissive wall, electrically biased in a plasma, is revisited through a simple fluid model. We search for realistic conditions of the existence of a non-monotonic plasma potential profile with a virtual cathode as it is observed in several experiments. We mainly focus our attention on thermionic emission related to the operation of emissive probes for plasma diagnostics, although most conclusions also apply to other electron emission processes. An extended Bohm criterion is derived involving the ratio between the two different electron densities at the potential minimum and at the background plasma. The model allows a phase-diagram analysis, which confirms the existence of the non-monotonic potential profiles with a virtual cathode. This analysis shows that the formation of the potential well critically depends on the emitted electron current and on the velocity at the sheath edge of cold ions flowing from the bulk plasma. As a consequence, a threshold value of the governing parameter is required, in accordance to the physical nature of the electron emission process. The latter is a threshold wall temperature in the case of thermionic electrons. Experimental evidence supports our numerical calculations of this threshold temperature. Besides this, the potential well becomes deeper with increasing electron emission, retaining a fraction of the released current which limits the extent of the bulk plasma perturbation. This noninvasive property would explain the reliable measurements of plasma potential by using the floating potential method of emissive probes operating in the so-called strong emission regime.

Existence of a virtual cathode close to a strongly electron emissive wall in low density plasmas

International Nuclear Information System (INIS)

Tierno, S. P.; Donoso, J. M.; Domenech-Garret, J. L.; Conde, L.

2016-01-01

The interaction between an electron emissive wall, electrically biased in a plasma, is revisited through a simple fluid model. We search for realistic conditions of the existence of a non-monotonic plasma potential profile with a virtual cathode as it is observed in several experiments. We mainly focus our attention on thermionic emission related to the operation of emissive probes for plasma diagnostics, although most conclusions also apply to other electron emission processes. An extended Bohm criterion is derived involving the ratio between the two different electron densities at the potential minimum and at the background plasma. The model allows a phase-diagram analysis, which confirms the existence of the non-monotonic potential profiles with a virtual cathode. This analysis shows that the formation of the potential well critically depends on the emitted electron current and on the velocity at the sheath edge of cold ions flowing from the bulk plasma. As a consequence, a threshold value of the governing parameter is required, in accordance to the physical nature of the electron emission process. The latter is a threshold wall temperature in the case of thermionic electrons. Experimental evidence supports our numerical calculations of this threshold temperature. Besides this, the potential well becomes deeper with increasing electron emission, retaining a fraction of the released current which limits the extent of the bulk plasma perturbation. This noninvasive property would explain the reliable measurements of plasma potential by using the floating potential method of emissive probes operating in the so-called strong emission regime

Existence of a virtual cathode close to a strongly electron emissive wall in low density plasmas

Energy Technology Data Exchange (ETDEWEB)

Tierno, S. P., E-mail: sp.tierno@upm.es; Donoso, J. M.; Domenech-Garret, J. L.; Conde, L. [Department of Applied Physics, E.T.S.I. Aeronáutica y del Espacio. Universidad Politécnica de Madrid, 28040 Madrid (Spain)

2016-01-15

The interaction between an electron emissive wall, electrically biased in a plasma, is revisited through a simple fluid model. We search for realistic conditions of the existence of a non-monotonic plasma potential profile with a virtual cathode as it is observed in several experiments. We mainly focus our attention on thermionic emission related to the operation of emissive probes for plasma diagnostics, although most conclusions also apply to other electron emission processes. An extended Bohm criterion is derived involving the ratio between the two different electron densities at the potential minimum and at the background plasma. The model allows a phase-diagram analysis, which confirms the existence of the non-monotonic potential profiles with a virtual cathode. This analysis shows that the formation of the potential well critically depends on the emitted electron current and on the velocity at the sheath edge of cold ions flowing from the bulk plasma. As a consequence, a threshold value of the governing parameter is required, in accordance to the physical nature of the electron emission process. The latter is a threshold wall temperature in the case of thermionic electrons. Experimental evidence supports our numerical calculations of this threshold temperature. Besides this, the potential well becomes deeper with increasing electron emission, retaining a fraction of the released current which limits the extent of the bulk plasma perturbation. This noninvasive property would explain the reliable measurements of plasma potential by using the floating potential method of emissive probes operating in the so-called strong emission regime.

Hollow density profile on electron cyclotron resonance heating JFT-2M plasma

International Nuclear Information System (INIS)

Yamauchi, Toshihiko; Hoshino, Katsumichi; Kawashima, Hisato; Ogawa, Toshihide; Kawakami, Tomohide; Shiina, Tomio; Ishige, Youichi

1998-01-01

The first hollow electron density profile in the central region on the JAERI Fusion Torus-2M (JFT-2M) is measured during electron cyclotron resonance heating (ECRH) with a TV Thomson scattering system (TVTS). The peripheral region is not hollow but is accumulated due to pump-out from the central region. The hollowness increases with time but is saturated at ∼40 ms and maintains a constant hollow ratio. The hollowness is strongly related to the steep temperature gradient of the heated zone. (author)

Impulse electron gun with plasma cathode for realization of large diameter tube-shaped beams

International Nuclear Information System (INIS)

Antipov, V.S.; Karpukhin, V.I.; Kornilov, E.A.

1999-01-01

There are presented the results of investigations of a plasma electron source based on the gas discharge in a coaxial system of electrodes with longitudinal magnetic field. The examination is fulfilled from the viewpoint of applying the source as a plasma cathode for hybrid plasma-waveguide slow-wave structures on the basis of a disk-loaded coaxial. The source is optimized in order to get a powerful (up to 100 kW) nonrelativistic electron beam with the annular cross-section of a large diameter in the regime of relatively long current pulses (up to 0.2 ms) under the gas pressure ∼ 5 centre dot 10 -4 mm Hg in the area of the discharge burning

Investigations Of A Pulsed Cathodic Vacuum Arc

Science.gov (United States)

Oates, T. W. H.; Pigott, J.; Denniss, P.; Mckenzie, D. R.; Bilek, M. M. M.

2003-06-01

Cathodic vacuum arcs are well established as a method for producing thin films for coatings and as a source of metal ions. Research into DC vacuum arcs has been going on for over ten years in the School of Physics at the University of Sydney. Recently a project was undertaken in the school to design and build a pulsed CVA for use in the investigation of plasma sheaths and plasma immersion ion implantation. Pulsed cathodic vacuum arcs generally have a higher current and plasma density and also provide a more stable and reproducible plasma density than their DC counterparts. Additionally it has been shown that if a high repetition frequency can be established the deposition rate of pulsed arcs is equal to or greater than that of DC arcs with a concomitant reduction in the rate of macro-particle formation. We present here results of our investigations into the building of a center-triggered pulsed cathodic vacuum arc. The design of the power supply and trigger mechanism and the geometry of the anode and cathode are examined. Observations of type I and II arc spots using a CCD camera, and cathode spot velocity dependence on arc current will be presented. The role of retrograde motion in a high current pulsed arc is discussed.

Investigations Of A Pulsed Cathodic Vacuum Arc

International Nuclear Information System (INIS)

Oates, T.W.H.; Pigott, J.; Denniss, P.; Mckenzie, D.R.; Bilek, M.M.M.

2003-01-01

Cathodic vacuum arcs are well established as a method for producing thin films for coatings and as a source of metal ions. Research into DC vacuum arcs has been going on for over ten years in the School of Physics at the University of Sydney. Recently a project was undertaken in the school to design and build a pulsed CVA for use in the investigation of plasma sheaths and plasma immersion ion implantation. Pulsed cathodic vacuum arcs generally have a higher current and plasma density and also provide a more stable and reproducible plasma density than their DC counterparts. Additionally it has been shown that if a high repetition frequency can be established the deposition rate of pulsed arcs is equal to or greater than that of DC arcs with a concomitant reduction in the rate of macro-particle formation. We present here results of our investigations into the building of a center-triggered pulsed cathodic vacuum arc. The design of the power supply and trigger mechanism and the geometry of the anode and cathode are examined. Observations of type I and II arc spots using a CCD camera, and cathode spot velocity dependence on arc current will be presented. The role of retrograde motion in a high current pulsed arc is discussed

Heating of refractory cathodes by high-pressure arc plasmas: II

International Nuclear Information System (INIS)

Benilov, M S; Cunha, M D

2003-01-01

Solitary spots on infinite planar cathodes and diffuse and axially symmetric spot modes on finite cathodes of high-pressure arc discharges are studied in a wide range of arc currents. General features are analysed and extensive numerical results on planar and cylindrical tungsten cathodes of atmospheric-pressure argon arcs are given for currents of up to 100 kA. It is shown, in particular, that the temperature of cathode surface inside a solitary spot varies relatively weakly and may be estimated, to the accuracy of about 200-300 K, without actually solving the thermal conduction equation in the cathode body. Asymptotic behaviour of solutions for finite cathodes in the limiting case of high currents is found and confirmed by numerical results. A general pattern of current-voltage characteristics of various modes on finite cathodes suggested previously on the basis of bifurcation analysis is confirmed. A transition from the spot modes on a finite cathode in the limit of large cathode dimensions to the solitary spot mode on an infinite planar cathode is studied. It is found that the solitary spot mode represents a limiting form of the high-voltage spot mode on a finite cathode. A question of distinguishing between diffuse and spot modes on finite cathodes is considered

Nonequilibrium phenomena and determination of plasma parameters in the hot core of the cathode region in free-burning arc discharges

International Nuclear Information System (INIS)

Kuehn, Gerrit; Kock, Manfred

2007-01-01

We present spectroscopic measurements of plasma parameters (electron density n e , electron temperature T e , gas temperature T g , underpopulation factor b) in the hot-core region in front of the cathode of a low-current, free-burning arc discharge in argon under atmospheric pressure. The discharge is operated in the hot-core mode, creating a hot cathode region with plasma parameters similar to high-current arcs in spite of the fact that we use comparatively low currents (less than 20 A). We use continuum emission and (optically thin) line emission to determine n e and T e . We apply relaxation measurements based on a power-interruption technique to investigate deviations from local thermodynamic equilibrium (LTE). These measurements let us determine the gas temperature T g . All measurements are performed side-on with charge-coupled-device cameras as detectors, so that all measured plasma parameters are spatially resolved after an Abel inversion. This yields the first ever spatially resolved observation of the non-LTE phenomena of the hot core in the near-cathode region of free-burning arcs. The results only partly coincide with previously published predictions and measurements in the literature

Synthesis of aluminum nitride films by plasma immersion ion implantation-deposition using hybrid gas-metal cathodic arc gun

International Nuclear Information System (INIS)

Shen Liru; Fu, Ricky K.Y.; Chu, Paul K.

2004-01-01

Aluminum nitride (AlN) is of interest in the industry because of its excellent electronic, optical, acoustic, thermal, and mechanical properties. In this work, aluminum nitride films are deposited on silicon wafers (100) by metal plasma immersion ion implantation and deposition (PIIID) using a modified hybrid gas-metal cathodic arc plasma source and with no intentional heating to the substrate. The mixed metal and gaseous plasma is generated by feeding the gas into the arc discharge region. The deposition rate is found to mainly depend on the Al ion flux from the cathodic arc source and is only slightly affected by the N 2 flow rate. The AlN films fabricated by this method exhibit a cubic crystalline microstructure with stable and low internal stress. The surface of the AlN films is quite smooth with the surface roughness on the order of 1/2 nm as determined by atomic force microscopy, homogeneous, and continuous, and the dense granular microstructures give rise to good adhesion with the substrate. The N to Al ratio increases with the bias voltage applied to the substrates. A fairly large amount of O originating from the residual vacuum is found in the samples with low N:Al ratios, but a high bias reduces the oxygen concentration. The compositions, microstructures and crystal states of the deposited films are quite stable and remain unchanged after annealing at 800 deg. C for 1 h. Our hybrid gas-metal source cathodic arc source delivers better AlN thin films than conventional PIIID employing dual plasmas

Surface modification of polyimide (PI) film using water cathode atmospheric pressure glow discharge plasma

International Nuclear Information System (INIS)

Zheng Peichao; Liu Keming; Wang Jinmei; Dai Yu; Yu Bin; Zhou Xianju; Hao Honggang; Luo Yuan

2012-01-01

Highlights: ► Equipment called water cathode atmospheric pressure glow discharge was used to improve the hydrophilicity of polyimide films. ► The data shows good homogeneity and the variation trends of contact angles are different for polar and non-polar testing liquids. ► The thickness of liquid layer plays an important role in plasma processing and directly affects the treatment effect. ► Surface hydrophilicity after plasma treatment is improved partly due to the increase in the roughness. ► The hydrophilicity of polyimide films is still better than untreated ones after long-term storage. - Abstract: The industrial use of polyimide film is limited because of undesirable properties such as poor wettability. In the present paper, a new kind of equipment called water cathode atmospheric pressure glow discharge was used to improve the surface properties of polyimide films and made them useful to technical applications. The changes in hydrophilicity of modified polyimide film surfaces were investigated by contact angle, surface energy and water content measurements as a function of treatment time. The results obtained show good treatment homogeneity and that the variation trends of contact angles are different for polar and non-polar testing liquids, while surface energy and water content are significantly enhanced with the increase of treatment time until they achieve saturated values after 60 s plasma treatment. Also, the thickness of liquid layer plays an important role in plasma processing and directly affects the treatment effect. Changes in morphology of polyimide films were analyzed by atomic force microscope and the results indicate that surface hydrophilicity after plasma treatment are improved partly due to the increase in the roughness. In addition, polyimide films treated by plasma are subjected to an ageing process to determine the durability of plasma treatment. It is found that the hydrophilicity is still better than untreated ones though the

Impact of cathode evaporation on a free-burning arc

International Nuclear Information System (INIS)

Etemadi, K.

1990-01-01

In the center of a free-burning, high intensity argon arc at atmospheric pressure, a highly ionized vapor beam of copper has been generated by a continuous feeding of a thin (0.5 and 1 mm diameter) copper wire to the hot surface region of the cathode in the vicinity of the plasma attachment. The copper vapor is carried into the plasma column between the electrodes by the self-magnetic induced plasma flow caused by the conical shape of the cathode. In order to study the vapor beam, the arc is modeled at atmospheric pressure, with a current of 150 A, a gap spacing of 1 cm, a cathode tip of 60 degrees and a copper vapor flow of 1 mg/s. The temperature, mass flow, current flow and Cu concentration are calculated for the entire plasma region. The intensity distribution of CuI spectral line at 5218.2 angstrom is also recorded by emission spectroscopy and compared with the calculated values. The copper vapor in the cathode region has velocities of 210 m/s with a mass concentration of above 90% within 0.5 mm from the arc axis. The vapor passes from the cathode toward the anode with a slight diffusion in the argon plasma. Higher temperatures and current densities in the core of the arc, caused by the cathode evaporation, are calculated

A compact new incoherent Thomson scattering diagnostic for low-temperature plasma studies

Science.gov (United States)

Vincent, Benjamin; Tsikata, Sedina; Mazouffre, Stéphane; Minea, Tiberiu; Fils, Jérôme

2018-05-01

Incoherent Thomson scattering (ITS) has a long history of application for the determination of electron density and temperature in dense fusion plasmas, and in recent years, has been increasingly extended to studies in low-temperature plasma environments. In this work, the design and preliminary implementation of a new, sensitive and uniquely compact ITS platform known as Thomson scattering experiments for low temperature ion sources are described. Measurements have been performed on a hollow cathode plasma source, providing access to electron densities as low as 1016 m‑3 and electron temperatures of a few eV and below. This achievement has been made possible by the implementation of a narrow volume Bragg grating notch filter for the attenuation of stray light, a feature which guarantees compactness and reduced transmission losses in comparison to standard ITS platforms.

Influence of thin porous Al2O3 layer on aluminum cathode to the Hα line shape in glow discharge

International Nuclear Information System (INIS)

Steflekova, V.; Sisovic, N. M.; Konjevic, N.

2009-01-01

The results of the Balmer alfa line shape study in a plane cathode-hollow anode Grimm discharge with aluminum (Al) cathode covered with thin layer of porous Al 2 O 3 are presented. The comparison with same line profile recorded with pure Al cathode shows lack of excessive Doppler broadened line wings, which are always detected in glow discharge with metal cathode. The effect is explained by the lack of strong electric field in the cathode sheath region, which is missing in the presence of thin oxide layer in, so called, spray discharge.

Research and Development of a New Field Enhanced Low Temperature Thermionic Cathode that Enables Fluorescent Dimming and Loan Shedding without Auxiliary Cathode Heating

Energy Technology Data Exchange (ETDEWEB)

Feng Jin

2009-01-07

This is the final report for project entitled 'Research and development of a new field enhanced low temperature thermionic cathode that enables fluorescent dimming and load shedding without auxiliary cathode heating', under Agreement Number: DE-FC26-04NT-42329. Under this project, a highly efficient CNT based thermionic cathode was demonstrated. This cathode is capable of emitting electron at a current density two order of magnitude stronger then a typical fluorescent cathode at same temperatures, or capable of emitting at same current density but at temperature about 300 C lower than that of a fluorescent cathode. Detailed fabrication techniques were developed including CVD growth of CNTs and sputter deposition of oxide thin films on CNTs. These are mature technologies that have been widely used in industry for large scale materials processing and device fabrications, thus, with further development work, the techniques developed in this project can be scaled-up in manufacturing environment. The prototype cathodes developed in this project were tested in lighting plasma discharge environment. In many cases, they not only lit and sustain the plasma, but also out perform the fluorescent cathodes in key parameters such like cathode fall voltages. More work will be needed to further evaluate more detailed and longer term performance of the prototype cathode in lighting plasma.

High-energy lithium-ion hybrid supercapacitors composed of hierarchical urchin-like WO3/C anodes and MOF-derived polyhedral hollow carbon cathodes.

Science.gov (United States)

Xu, Juan; Li, Yuanyuan; Wang, Lei; Cai, Qifa; Li, Qingwei; Gao, Biao; Zhang, Xuming; Huo, Kaifu; Chu, Paul K

2016-09-22

A lithium-ion hybrid supercapacitor (Li-HSC) comprising a Li-ion battery type anode and an electrochemical double layer capacitance (EDLC) type cathode has attracted much interest because it accomplishes a large energy density without compromising the power density. In this work, hierarchical carbon coated WO 3 (WO 3 /C) with a unique mesoporous structure and metal-organic framework derived nitrogen-doped carbon hollow polyhedra (MOF-NC) are prepared and adopted as the anode and the cathode for Li-HSCs. The hierarchical mesoporous WO 3 /C microspheres assembled by radially oriented WO 3 /C nanorods along the (001) plane enable effective Li + insertion, thus exhibit high capacity, excellent rate performance and a long cycling life due to their high Li + conductivity, electronic conductivity and structural robustness. The WO 3 /C structure shows a reversible specific capacity of 508 mA h g -1 at a 0.1 C rate (1 C = 696 mA h g -1 ) after 160 discharging-charging cycles with excellent rate capability. The MOF-NC achieved the specific capacity of 269.9 F g -1 at a current density of 0.2 A g -1 . At a high current density of 6 A g -1 , 92.4% of the initial capacity could be retained after 2000 discharging-charging cycles, suggesting excellent cycle stability. The Li-HSC comprising a WO 3 /C anode and a MOF-NC cathode boasts a large energy density of 159.97 W h kg -1 at a power density of 173.6 W kg -1 and 88.3% of the capacity is retained at a current density of 5 A g -1 after 3000 charging-discharging cycles, which are better than those previously reported for Li-HSCs. The high energy and power densities of the Li-HSCs of WO 3 /C//MOF-NC render large potential in energy storage.

Nanosized aluminum nitride hollow spheres formed through a self-templating solid-gas interface reaction

International Nuclear Information System (INIS)

Zheng Jie; Song Xubo; Zhang Yaohua; Li Yan; Li Xingguo; Pu Yikang

2007-01-01

Nanosized aluminum nitride hollow spheres were synthesized by simply heating aluminum nanoparticles in ammonia at 1000 deg. C. The as-synthesized sphere shells are polycrystalline with cavity diameters ranging from 15 to 100 nm and shell thickness from 5 to 15 nm. The formation mechanism can be explained by the nanoscale Kirkendall effect, which results from the difference in diffusion rates between aluminum and nitrogen. The Al nanoparticles served as both reactant and templates for the hollow sphere formation. The effects of precursor particle size and temperature were also investigated in terms of product morphology. Room temperature cathode luminescence spectrum of the nanosized hollow spheres showed a broad emission band centered at 415 nm, which is originated from oxygen related luminescence centers. The hollow structure survived a 4-h heat treatment at 1200 deg. C, exhibiting excellent thermal stability. - Graphical abstract: Nanosized aluminum nitride hollow spheres were synthesized by nitridation of aluminum nanoparticles at 1000 deg. C using ammonia

Verification of high efficient broad beam cold cathode ion source

Energy Technology Data Exchange (ETDEWEB)

Abdel Reheem, A. M., E-mail: amreheem2009@yahoo.com [Accelerators and Ion Sources Department, Nuclear Research Center, Atomic Energy Authority, P.N.13759, Cairo (Egypt); Radiation Physics Department, National Center for Radiation Research and Technology (NCRRT), Atomic Energy Authority (AEA), Cairo (Egypt); Ahmed, M. M. [Physics Department, Faculty of Science, Helwan University, Cairo (Egypt); Abdelhamid, M. M.; Ashour, A. H. [Radiation Physics Department, National Center for Radiation Research and Technology (NCRRT), Atomic Energy Authority (AEA), Cairo (Egypt)

2016-08-15

An improved form of cold cathode ion source has been designed and constructed. It consists of stainless steel hollow cylinder anode and stainless steel cathode disc, which are separated by a Teflon flange. The electrical discharge and output characteristics have been measured at different pressures using argon, nitrogen, and oxygen gases. The ion exit aperture shape and optimum distance between ion collector plate and cathode disc are studied. The stable discharge current and maximum output ion beam current have been obtained using grid exit aperture. It was found that the optimum distance between ion collector plate and ion exit aperture is equal to 6.25 cm. The cold cathode ion source is used to deposit aluminum coating layer on AZ31 magnesium alloy using argon ion beam current which equals 600 μA. Scanning electron microscope and X-ray diffraction techniques used for characterizing samples before and after aluminum deposition.

Facile synthesis of aluminum-doped LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} hollow microspheres and their electrochemical performance for high-voltage Li-ion batteries

Energy Technology Data Exchange (ETDEWEB)

Liu, Xiaolin, E-mail: liu_x_l@sina.cn [College of Material Science and Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, Jiangxi (China); Li, Dan; Mo, Qiaoling; Guo, Xiaoyu; Yang, Xiaoxiao [College of Material Science and Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, Jiangxi (China); Chen, Guoxin, E-mail: gxchen@nimte.ac.cn [Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, Zhejiang (China); Zhong, Shengwen [College of Material Science and Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, Jiangxi (China)

2014-10-01

Graphical abstract: LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} and Al doped LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} hollow microspheres as 5 V cathodes are prepared by templated transformation method using monodisperse MnCO{sub 3} microspheres as precursor. As a cathodic material for high voltage lithium ion batteries, the as-synthesized LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} and Al doped LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} hollow microspheres are investigated by galvanostatic cycling (GC) approach to evaluate their electrochemical properties in the range of 2.7–4.8 V vs. Li/Li{sup +} at the current rate 1 C. - Highlights: • LNMO and LANMO hollow microspheres are synthesized by template method. • The as-synthesized hollow microspheres have particle-size of 2 μm. • The hollow structure is responsible for improved electrochemical performance. - Abstract: This paper presents the preparation of LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} and aluminum (Al) doped LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} hollow microspheres as 5 V cathodes using monodisperse MnCO{sub 3} microspheres as precursor and template, which were synthesized using MnSO{sub 4}·H{sub 2}O, NaHCO{sub 3} and ethanol in water at room temperature. XRD and morphology characterization results indicated that the as-prepared LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} and Al doped LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} were both spinel structure, and have particle sizes of 2–3 μm. The cathode electrochemical properties of LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} and Al doped LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} hollow microspheres (as 5 V cathodes) were evaluated and compared by galvanostatic cycling (GC) vs. Li/Li{sup +} at the current rate 1 C in 2.7–4.8 V. The specific initial capacities of all samples were in the range of 70–120 mA h g{sup −1}. Compared to undoped LiNi{sub 0.5}Mn{sub 1.5}O{sub 4}, Al doped LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} hollow structures can effectively improve discharge capacity (up to 140 (±5) mA h g{sup −1}) and cycling stability (70

Investigation of the effect of Hollow Cathode in a Grimm-type source (Ar) on the excitation processes using Fe samples

International Nuclear Information System (INIS)

Weinstein, V.; Steers, E.B.M.

2009-01-01

Complete text of publication follows. Analytical spectroscopic applications using a Grimm Glow Discharge source sometimes require an increased sensitivity and therefore a higher signal to background ratio, which can be reached by using hollow cathode (HC) instead of plane samples. At the beginning of the 20 th century, intensity enhancements of emission lines using HC were observed and explained by longer residence time of sample atoms and consequently more collisional excitation. Later a HC was used with a Grimm source, to achieve higher sensitivity for lines of minor constituents. Recently the HC effect was further investigated for several metallic samples with a commercial GD-OES instrument (T.Gusarova., J. Anal. At. Spectrom., 2009., DOI: 10.1039/b814977a) for improvement of the signal to background ratio (SBR). The intensities and SBR from HC and plane cathode were compared, but only one or two lines could be observed for each element in the sample. The line intensities using plane and HC samples depend on the excitation processes occurring in the two cases. To make conclusions about the excitation mechanism differences, a large number of lines should be examined. Therefore we have recorded spectra over a wide wavelength range (approx. 200-600 nm) using a Fourier Transform Spectrometer (FTS), which allows simultaneous recording of spectra with a very high resolution. The 15 mm deep Fe HC sample and Fe plane cathode sample were analysed using argon as the carrier gas. The comparison of the data was made by calculating the ratio of intensities obtained from the HC sample to intensities of the plane cathode sample and plotting this against the excitation energy of Fe I, Fe II and Ar I, Ar II emission lines. Such plots link the intensity differences with the upper levels of the transitions and so help to clarify the relative importance of excitation processes. The experiments were also carried out at different currents, therefore the effect of the current on

Origin of microplasma instabilities during DC operation of silicon based microhollow cathode devices

International Nuclear Information System (INIS)

Felix, Valentin; Lefaucheux, Philippe; Aubry, Olivier; Dussart, Rémi; Golda, Judith; Schulz-von der Gathen, Volker; Overzet, Lawrence J

2016-01-01

The failure mechanisms of micro hollow cathode discharges (MHCD) in silicon have been investigated using their I-V characteristics, high speed photography and scanning electron microscopy. Experiments were carried out in helium. We observed I–V instabilities in the form of rapid voltage decreases associated with current spikes. The current spikes can reach values more than 100 times greater than the average MHCD current. (The peaks can be more than 1 Ampere for a few 10’s of nanoseconds.) These current spikes are correlated in time with 3–10 μm diameter optical flashes that occur inside the cavities. The SEM characterizations indicated that blister-like structures form on the Si surface during plasma operation. Thin Si layers detach from the surface in localized regions. We theorize that shallow helium implantation occurs and forms the ‘blisters’ whenever the Si is biased as the cathode. These blisters ‘explode’ when the helium pressure inside them becomes too large leading to the transient micro-arcs seen in both the optical emission and the I–V characteristics. We noted that blisters were never found on the metal counter electrode, even when it was biased as the cathode (and the Si as the anode). This observation led to a few suggestions for delaying the failure of Si MHCDs. One may coat the Si cathode (cavities) with blister resistant material; design the MHCD array to operate with the Si as the anode rather than as the cathode; or use a gas additive to prevent surface damage. Regarding the latter, tests using SF 6 as the gas additive successfully prevented blister formation through rapid etching. The result was an enhanced MHCD lifetime. (paper)

Gyrocenter Shift of Low-Temperature Plasmas and the Retrograde Motion of Cathode Spots in Arc Discharges

International Nuclear Information System (INIS)

Lee, K. C.

2007-01-01

The gyrocenter shift phenomenon explained the mechanism of radial electric field formation at the high confinement mode transition in fusion devices. This Letter reports that the theory of gyrocenter shift is also applicable to low temperature high collisional plasmas such as arc discharges by the generalization of the theory resulting from a short mean free path compared with the gyroradius. The retrograde motion of cathode spots in the arc discharge is investigated through a model with the expanded formula of gyrocenter shift. It is found that a reversed electric field is formed in front of the cathode spots when they are under a magnetic field, and this reversed electric field generates a rotation of cathode spots opposite to the Amperian direction. The ion drift velocity profiles calculated from the model are in agreement with the experimental results as functions of magnetic flux density and gas pressure

Studies on laser-assisted Penning ionization by the optogalvanic effect in Ne/Eu hollow cathode discharge.

Science.gov (United States)

Saini, V K; Kumar, P; Dixit, S K; Nakhe, S V

2015-02-01

Laser-assisted Penning ionization (LAPI) is detected in a Ne/Eu hollow cathode (HC) discharge lamp using the pulsed optogalvanic (OG) method. In the Ne/Eu discharge, doubly ionized europium excited energy levels Eu[4f(7)(P(7/2,5/2)6)] lie within the thermal limit (∼kT) from the laser-excited neon's energy level [2p(5)(P3/202)3p or 2p(8) (in Paschen notation)] lying at 149,848  cm(-1). Therefore, Penning ionization (PI) of europium atoms likely to occur into its highly excited ionic states is investigated. To probe the PI of europium, the temporal profiles of its counterpart neon OG signal are studied as a function of discharge current for the transitions (1s(4)→2p(8)) and (1s(2)→2p(2)), corresponding to 650.65 and 659.89 nm wavelengths, respectively. It is observed that PI of europium alters the overall discharge characteristics significantly and, hence, modifies the temporal profile of the OG signals accordingly. The quasi-resonant ionizing energy transfer collisions between laser-excited Ne 2p(8) atoms and electronically excited europium P(9/2)10 atoms are used to explain the LAPI mechanism. Such LAPI studies carried out in HC discharge could be useful for the discharge of a metal-vapor laser with appropriate Penning mixtures.

Ferroelectric Cathodes in Transverse Magnetic Fields

International Nuclear Information System (INIS)

Alexander Dunaevsky; Yevgeny Raitses; Nathaniel J. Fisch

2002-01-01

Experimental investigations of a planar ferroelectric cathode in a transverse magnetic field up to 3 kGs are presented. It is shown that the transverse magnetic field affects differently the operation of ferroelectric plasma cathodes in ''bright'' and ''dark'' modes in vacuum. In the ''bright'' mode, when the surface plasma is formed, the application of the transverse magnetic field leads to an increase of the surface plasma density. In the ''dark'' mode, the magnetic field inhibits the development of electron avalanches along the surface, as it does similarly in other kinds of surface discharges in the pre-breakdown mode

Advanced plasma flow simulations of cathodic-arc and ferroelectric plasma sources for neutralized drift compression experiments

Directory of Open Access Journals (Sweden)

Adam B. Sefkow

2008-07-01

Full Text Available Large-space-scale and long-time-scale plasma flow simulations are executed in order to study the spatial and temporal evolution of plasma parameters for two types of plasma sources used in the neutralized drift compression experiment (NDCX. The results help assess the charge neutralization conditions for ion beam compression experiments and can be employed in more sophisticated simulations, which previously neglected the dynamical evolution of the plasma. Three-dimensional simulations of a filtered cathodic-arc plasma source show the coupling efficiency of the plasma flow from the source to the drift region depends on geometrical factors. The nonuniform magnetic topology complicates the well-known general analytical considerations for evaluating guiding-center drifts, and particle-in-cell simulations provide a self-consistent evaluation of the physics in an otherwise challenging scenario. Plasma flow profiles of a ferroelectric plasma source demonstrate that the densities required for longitudinal compression experiments involving ion beams are provided over the drift length, and are in good agreement with measurements. Simulations involving azimuthally asymmetric plasma creation conditions show that symmetric profiles are nevertheless achieved at the time of peak on-axis plasma density. Also, the ferroelectric plasma expands upstream on the thermal expansion time scale, and therefore avoids the possibility of penetration into the acceleration gap and transport sections, where partial neutralization would increase the beam emittance. Future experiments on NDCX will investigate the transverse focusing of an axially compressing intense charge bunch to a sub-mm spot size with coincident focal planes using a strong final-focus solenoid. In order to fill a multi-tesla solenoid with the necessary high-density plasma for beam charge neutralization, the simulations predict that supersonically injected plasma from the low-field region will penetrate and

Impedance of an intense plasma-cathode electron source for tokamak startup

Science.gov (United States)

Hinson, E. T.; Barr, J. L.; Bongard, M. W.; Burke, M. G.; Fonck, R. J.; Perry, J. M.

2016-05-01

An impedance model is formulated and tested for the ˜1 kV , 1 kA/cm2 , arc-plasma cathode electron source used for local helicity injection tokamak startup. A double layer sheath is established between the high-density arc plasma ( narc≈1021 m-3 ) within the electron source, and the less dense external tokamak edge plasma ( nedge≈1018 m-3 ) into which current is injected at the applied injector voltage, Vinj . Experiments on the Pegasus spherical tokamak show that the injected current, Iinj , increases with Vinj according to the standard double layer scaling Iinj˜Vinj3 /2 at low current and transitions to Iinj˜Vinj1 /2 at high currents. In this high current regime, sheath expansion and/or space charge neutralization impose limits on the beam density nb˜Iinj/Vinj1 /2 . For low tokamak edge density nedge and high Iinj , the inferred beam density nb is consistent with the requirement nb≤nedge imposed by space-charge neutralization of the beam in the tokamak edge plasma. At sufficient edge density, nb˜narc is observed, consistent with a limit to nb imposed by expansion of the double layer sheath. These results suggest that narc is a viable control actuator for the source impedance.

Electron emission from pseudospark cathodes

International Nuclear Information System (INIS)

Anders, A.; Anders, S.; Gundersen, M.A.

1994-01-01

The pseudospark cathode has the remarkable property of macroscopically homogeneous electron emission at very high current density (>1 kA/cm 2 ) over a large area (some cm 2 ). The model of electron emission presented here is based on the assumption that the pseudospark microscopically utilizes explosive arc processes, as distinct from earlier models of ''anomalous emission in superdense glow discharges.'' Explosive emission similar to vacuum are cathode spots occurs rapidly when the field strength is sufficiently high. The plasma remains macroscopically homogeneous since the virtual plasma anode adapts to the cathode morphology so that the current is carried by a large number of homogeneously distributed cathode spots which are similar to ''type 1'' and ''type 2'' spots of vacuum arc discharges. The net cathode erosion is greatly reduced relative to ''spark gap-type'' emission. At very high current levels, a transition to highly erosive spot types occurs, and this ''arcing'' leads to a significant reduction in device lifetime. Assuming vacuum-arc-like cathode spots, the observed current density and time constants can be easily explained. The observed cathode erosion rate and pattern, recent fast-camera data, laser-induced fluorescence, and spectroscopic measurements support this approach. A new hypothesis is presented explaining current quenching at relatively low currents. From the point of view of electron emission, the ''superdense glow'' or ''superemissive phase'' of pseudosparks represents an arc and not a glow discharge even if no filamentation or ''arcing'' is observed

Beam-plasma interaction in a cold-cathodes penning discharge

International Nuclear Information System (INIS)

Bliman, S.L.

1966-06-01

The H.F. emissions from a cold-cathode reflex discharge are studied. An experimental law for the frequency variation shows that fαV 1/2 discharged if B 0 and p are constant. If B 0 is made to increase, the frequencies change such that f ce - f emitted / f ce decreases. With each emitted frequency there is associated a stationary wave system making it possible to measure the phase velocity Vφ of the waves. This phase velocity is always close to that of the fast electrons accelerated by a potential V discharge. A non-quasistatic formalism for the propagation of waves in a beam-plasma system is then established. The Maxwell equations are solved taking into account boundary conditions. Comparison of these experiments with the theory shows a satisfactory agreement. (author) [fr

Electrostatic/magnetic ion acceleration through a slowly diverging magnetic nozzle between a ring anode and an on-axis hollow cathode

Directory of Open Access Journals (Sweden)

A. Sasoh

2017-06-01

Full Text Available Ion acceleration through a slowly diverging magnetic nozzle between a ring anode and a hollow cathode set on the axis of symmetry has been realized. Xenon was supplied as the propellant gas from an annular slit along the inner surface of the ring anode so that it was ionized near the anode, and the applied electric potential was efficiently transformed to an ion kinetic energy. As an electrostatic thruster, within the examined operation conditions, the thrust, F, almost scaled with the propellant mass flow rate; the discharge current, Jd, increased with the discharge voltage, Vd. An important characteristic was that the thrust also exhibited electromagnetic acceleration performance, i.e., the so-called “swirl acceleration,” in which F≅JdBRa ∕2, where B and Ra were a magnetic field and an anode inner radius, respectively. Such a unique thruster performance combining both electrostatic and electromagnetic accelerations is expected to be useful as another option for in-space electric propulsion in its broad functional diversity.

Deposition of thin film of titanium on ceramic substrate using the discharge for hollow cathode for Al2O3/Al2O3 indirect brazing

Directory of Open Access Journals (Sweden)

Mary Roberta Meira Marinho

2009-01-01

Full Text Available Thin films of titanium were deposited onto Al2O3 substrate by hollow cathode discharge method for the formation of a ceramic-ceramic joint using indirect brazing method. An advantage of using this technique is that a relatively small amount of titanium is required for the metallization of the ceramic surface when compared with other conventional methods. Rapidly solidified brazing filler of Cu49Ag45Ce6 in the form of ribbons was used. The thickness of deposited titanium layer and the brazing temperature/time were varied. The quality of the brazed joint was evaluated through the three point bending flexural tests. The brazed joints presented high flexural resistance values up to 176 MPa showing the efficiency of the technique.

Graphene-coated hollow fiber membrane as the cathode in anaerobic electrochemical membrane bioreactors – Effect of configuration and applied voltage on performance and membrane fouling

KAUST Repository

Werner, Craig M.

2015-12-22

Electrically conductive, graphene-coated hollow-fiber porous membranes were used as cathodes in anaerobic electrochemical membrane bioreactors (AnEMBRs) operated at different applied voltages (0.7 V and 0.9 V) using a new rectangular reactor configuration, compared to a previous tubular design (0.7 V). The onset of biofouling was delayed and minimized in rectangular reactors operated at 0.9 V, compared to those at 0.7 V due to higher rates of hydrogen production. Maximum transmembrane pressures for the rectangular reactor were only 0.10 bar (0.7 V) or 0.05 bar (0.9 V) after 56 days of operation, compared to 0.46 bar (0.7 V) for the tubular reactor after 52 days. The thickness of the membrane biofouling layer was approximately 0.4 µm for rectangular reactors and 4 µm for the tubular reactor. Higher permeate quality (TSS = 0.05 mg/L) was achieved in the rectangular AnEMBR than the tubular AnEMBR (TSS = 17 mg/L), likely due to higher current densities that minimized the accumulation of cells in suspension. These results show that the new rectangular reactor design, which had increased rates of hydrogen production, successfully delayed the onset of cathode biofouling and improved reactor performance.

Graphene-coated hollow fiber membrane as the cathode in anaerobic electrochemical membrane bioreactors – Effect of configuration and applied voltage on performance and membrane fouling

KAUST Repository

Werner, Craig M.; Katuri, Krishna; Rao, Hari Ananda; Chen, Wei; Lai, Zhiping; Logan, Bruce E.; Amy, Gary L.; Saikaly, Pascal

2015-01-01

Electrically conductive, graphene-coated hollow-fiber porous membranes were used as cathodes in anaerobic electrochemical membrane bioreactors (AnEMBRs) operated at different applied voltages (0.7 V and 0.9 V) using a new rectangular reactor configuration, compared to a previous tubular design (0.7 V). The onset of biofouling was delayed and minimized in rectangular reactors operated at 0.9 V, compared to those at 0.7 V due to higher rates of hydrogen production. Maximum transmembrane pressures for the rectangular reactor were only 0.10 bar (0.7 V) or 0.05 bar (0.9 V) after 56 days of operation, compared to 0.46 bar (0.7 V) for the tubular reactor after 52 days. The thickness of the membrane biofouling layer was approximately 0.4 µm for rectangular reactors and 4 µm for the tubular reactor. Higher permeate quality (TSS = 0.05 mg/L) was achieved in the rectangular AnEMBR than the tubular AnEMBR (TSS = 17 mg/L), likely due to higher current densities that minimized the accumulation of cells in suspension. These results show that the new rectangular reactor design, which had increased rates of hydrogen production, successfully delayed the onset of cathode biofouling and improved reactor performance.

Effects of cathode current density on structure and corrosion resistance of plasma electrolytic oxidation coatings formed on ZK60 Mg alloy

International Nuclear Information System (INIS)

Su Peibo; Wu Xiaohong; Guo Yun; Jiang Zhaohua

2009-01-01

Current density is a key factor in plasma electrolytic oxidation (PEO) process. The aim of this paper is to study the effects of cathode current density on the composition, morphology, and corrosion resistance of ceramic coatings on ZK60 magnesium alloy prepared through bi-polar plasma electrolytic oxidation in Na 3 PO 4 solution. The phase composition, morphology, and corrosion resistance were studied by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization in 3.5% NaCl solution. It is found that the as-produced coatings are only composed of MgO. The increase of cathode current density made the coatings less porous and more compact. Analysis of EIS and potentiodynamic polarization technique on the samples shows that the corrosion resistance of the coated samples is better than that of ZK60 magnesium alloy, and that a bigger cathode current density can improve the corrosion resistance of as-prepared coatings.

Efficient Overall Water-Splitting Electrocatalysis Using Lepidocrocite VOOH Hollow Nanospheres

KAUST Repository

Shi, Huanhuan

2016-11-29

Herein we report the control synthesis of lepidocrocite VOOH hollow nanospheres and further their applications in electrocatalytic water splitting for the first time. By tuning the surface area of the nanospheres, the optimal performance can be achieved with low overpotentials of 270 mV for the oxygen evolution reaction (OER) and 164 mV for the hydrogen evolution reaction (HER) at 10 mA cm-2 in 1 m KOH, respectively. Furthermore, when used as both the anode and cathode for overall water splitting, a low cell voltage of 1.62 V is required to reach the current density of 10 mA cm-2 , making the VOOH hollow nanospheres an efficient alternative to water splitting.

Collisional and radiative processes in high-pressure discharge plasmas

Science.gov (United States)

Becker, Kurt H.; Kurunczi, Peter F.; Schoenbach, Karl H.

2002-05-01

Discharge plasmas at high pressures (up to and exceeding atmospheric pressure), where single collision conditions no longer prevail, provide a fertile environment for the experimental study of collisions and radiative processes dominated by (i) step-wise processes, i.e., the excitation of an already excited atomic/molecular state and by (ii) three-body collisions leading, for instance, to the formation of excimers. The dominance of collisional and radiative processes beyond binary collisions involving ground-state atoms and molecules in such environments allows for many interesting applications of high-pressure plasmas such as high power lasers, opening switches, novel plasma processing applications and sputtering, absorbers and reflectors for electromagnetic waves, remediation of pollutants and waste streams, and excimer lamps and other noncoherent vacuum-ultraviolet light sources. Here recent progress is summarized in the use of hollow cathode discharge devices with hole dimensions in the range 0.1-0.5 mm for the generation of vacuum-ultraviolet light.

Electron emission mechanism of carbon fiber cathode

International Nuclear Information System (INIS)

Liu Lie; Li Limin; Wen Jianchun; Wan Hong

2005-01-01

Models of electron emission mechanism are established concerning metal and carbon fiber cathodes. Correctness of the electron emission mechanism was proved according to micro-photos and electron scanning photos of cathodes respectively. The experimental results and analysis show that the surface flashover induces the electron emission of carbon fiber cathode and there are electron emission phenomena from the top of the carbon and also from its side surface. In addition, compared with the case of the stainless steel cathode, the plasma expansion velocity for the carbon fiber cathode is slower and the pulse duration of output microwave can be widened by using the carbon fiber cathode. (authors)

Interfacial Reaction Dependent Performance of Hollow Carbon Nanosphere – Sulfur Composite as a Cathode for Li-S Battery

International Nuclear Information System (INIS)

Zheng, Jianming; Yan, Pengfei; Gu, Meng; Wagner, Michael J.; Hays, Kevin A.; Chen, Junzheng; Li, Xiaohong; Wang, Chongmin; Zhang, Ji-Guang; Liu, Jun; Xiao, Jie

2015-01-01

Lithium-sulfur (Li-S) battery is a promising energy storage system due to its high energy density, cost effectiveness, and environmental friendliness of sulfur. However, there are still a number of technical challenges, such as low Coulombic efficiency and poor long-term cycle life, impeding the commercialization of Li-S battery. The electrochemical performance of Li-S battery is closely related with the interfacial reactions occurring between hosting substrate and active sulfur species, which are poorly conducting at fully oxidized and reduced states. Here, we correlate the relationship between the performance and interfacial reactions in the Li-S battery system, using a hollow carbon nanosphere (HCNS) with highly graphitic character as hosting substrate for sulfur. With an appropriate amount of sulfur loading, HCNS/S composite exhibits excellent electrochemical performance because of the fast interfacial reactions between HCNS and the polysulfides. However, further increase of sulfur loading leads to increased formation of highly resistive insoluble reaction products (Li 2 S 2 /Li 2 S), which limits the reversibility of the interfacial reactions and results in poor electrochemical performances. These findings demonstrate the importance of the interfacial reaction reversibility in the whole electrode system on achieving high capacity and long cycle life of sulfur cathode for Li-S batteries.

Interfacial Reaction Dependent Performance of Hollow Carbon Nanosphere – Sulfur Composite as a Cathode for Li-S Battery

Energy Technology Data Exchange (ETDEWEB)

Zheng, Jianming; Yan, Pengfei; Gu, Meng [Pacific Northwest National Laboratory, Richland, WA (United States); Wagner, Michael J.; Hays, Kevin A. [The George Washington University, Washington, DC (United States); Chen, Junzheng; Li, Xiaohong; Wang, Chongmin; Zhang, Ji-Guang; Liu, Jun; Xiao, Jie, E-mail: jie.xiao@pnnl.gov [Pacific Northwest National Laboratory, Richland, WA (United States)

2015-05-26

Lithium-sulfur (Li-S) battery is a promising energy storage system due to its high energy density, cost effectiveness, and environmental friendliness of sulfur. However, there are still a number of technical challenges, such as low Coulombic efficiency and poor long-term cycle life, impeding the commercialization of Li-S battery. The electrochemical performance of Li-S battery is closely related with the interfacial reactions occurring between hosting substrate and active sulfur species, which are poorly conducting at fully oxidized and reduced states. Here, we correlate the relationship between the performance and interfacial reactions in the Li-S battery system, using a hollow carbon nanosphere (HCNS) with highly graphitic character as hosting substrate for sulfur. With an appropriate amount of sulfur loading, HCNS/S composite exhibits excellent electrochemical performance because of the fast interfacial reactions between HCNS and the polysulfides. However, further increase of sulfur loading leads to increased formation of highly resistive insoluble reaction products (Li{sub 2}S{sub 2}/Li{sub 2}S), which limits the reversibility of the interfacial reactions and results in poor electrochemical performances. These findings demonstrate the importance of the interfacial reaction reversibility in the whole electrode system on achieving high capacity and long cycle life of sulfur cathode for Li-S batteries.

Characterization of atomic oxygen in a Hollow Cathode Radio-Frequency Plasma and study its efficiency

International Nuclear Information System (INIS)

Naddaf, M.; Saloum, S.

2011-01-01

The atomic oxygen (AO) generated in the remote oxygen plasma of the HCD-L300 source, has been fully diagnosed by various conventional techniques. The density of AO was found to vary from (1-10)x10 1 9 m - 3 depending on the operating conditions and parameters. The interaction of the oxygen plasma with silver and gold thin films is investigated by gravimetric analysis, scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) spectroscopy. The effect of AO on surface wetting and energy of polymeric materials is also investigated by using contact angle measurements and analysis technique. From applied point of view, production of super hydrophobic Teflon surface and the significant enhancement in the surface free energy of polyimide and polyamide are considered the most important obtained results in the present work. (author)

Measurement of total energy flux density at a substrate during TiO.sub.x./sub. thin film deposition by using a plasma jet system

Czech Academy of Sciences Publication Activity Database

Čada, Martin; Virostko, Petr; Kment, Štěpán; Hubička, Zdeněk

2009-01-01

Roč. 83, č. 4 (2009), s. 738-744 ISSN 0042-207X R&D Projects: GA AV ČR KJB100100707; GA AV ČR KAN301370701 Institutional research plan: CEZ:AV0Z10100522 Keywords : hollow cathode * plasma jet * sputtering * pulsed DC * energy influx on substrate * TiO 2 Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.975, year: 2009 http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TW4-4SJ2WRT-2&_user=625012&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000031722&_vers

Plasma Nitriding of AISI 304 Stainless Steel in Cathodic and Floating Electric Potential: Influence on Morphology, Chemical Characteristics and Tribological Behavior

Science.gov (United States)

Li, Yang; He, Yongyong; Wang, Wei; Mao, Junyuan; Zhang, Lei; Zhu, Yijie; Ye, Qianwen

2018-03-01

In direct current plasma nitriding (DCPN), the treated components are subjected to a high cathodic potential, which brings several inherent shortcomings, e.g., damage by arcing and the edging effect. In active screen plasma nitriding (ASPN) processes, the cathodic potential is applied to a metal screen that surrounds the workload, and the component to be treated is placed in a floating potential. Such an electrical configuration allows plasma to be formed on the metal screen surface rather than on the component surface; thus, the shortcomings of the DCPN are eliminated. In this work, the nitrided experiments were performed using a plasma nitriding unit. Two groups of samples were placed on the table in the cathodic and the floating potential, corresponding to the DCPN and ASPN, respectively. The floating samples and table were surrounded by a steel screen. The DCPN and ASPN of the AISI 304 stainless steels are investigated as a function of the electric potential. The samples were characterized using scanning electron microscopy with energy-dispersive x-ray spectroscopy, x-ray diffraction, atomic force microscopy and transmission electron microscope. Dry sliding ball-on-disk wear tests were conducted on the untreated substrate, DCPN and ASPN samples. The results reveal that all nitrided samples successfully produced similar nitrogen-supersaturated S phase layers on their surfaces. This finding also shows the strong impact of the electric potential of the nitriding process on the morphology, chemical characteristics, hardness and tribological behavior of the DCPN and ASPN samples.

Understanding anode and cathode behaviour in high-pressure discharge lamps

Science.gov (United States)

Flesch, P.; Neiger, M.

2005-09-01

High-intensity discharge (HID) lamps have widespread and modern areas of application including general lighting, video/movie projection (e.g. UHP lamp), street/industrial lighting, and automotive headlight lamps (D2/xenon lamp). Even though HID lamps have been known for several decades now, the important plasma-electrode interactions are still not well understood. Because HID lamps are usually operated on ac (electrodes switch alternately from anode to cathode phase), time-dependent simulations including realistic and verified anode and cathode models are essential. Therefore, a recently published investigation of external laser heating of an electrode during anode and cathode phase in an operating HID lamp [28] provided the basis for our present paper. These measurements revealed impressive influences of the external laser heating on electrode fall voltage and electrode temperature. Fortunately, the effects are very different during anode and cathode phase. Thus, by comparing the experimental findings with results from our numerical simulations we can learn much about the principles of electrode behaviour and explain in detail the differences between anode and cathode phase. Furthermore, we can verify our model (which includes plasma column, hot plasma spots in front of the electrodes, constriction zones and near-electrode non-local thermal equilibrium-plasma as well as anode and cathode) that accounts for all relevant physical processes concerning plasma, electrodes and interactions between them. Moreover, we investigate the influence of two different notions concerning ionization and recombination in the near electrode plasma on the numerical results. This improves our physical understanding of near-electrode plasma likewise and further increases the confidence in the model under consideration. These results are important for the understanding and the further development of HID lamps which, due to their small dimensions, are often experimentally inaccessible

Explosive-emission cathode fabricated from superconducting cable

International Nuclear Information System (INIS)

Vavra, I.; Korenev, S.A.

1989-01-01

The authors describe on explosive-emission cathode that is based on stock superconducting cable - type NT-50, for example - that is bunched and held in a copper matrix. The copper matrix is partially etched away to create a multipoint structure for the cathode-plasma initiators. With 100-300 kV on the diode and a distance of 1 cm between the anode and cathode, electron currents of 20-80 and 60-300 A are obtained with cathode diameters of 0.5 and 1 cm, respectively

Quality, Stability, and Safety Data of Packed Red Cells and Plasma Processed by Gravity Separation Using a New Fully Integrated Hollow-Fibre Filter Device

Directory of Open Access Journals (Sweden)

T. Brune

2009-01-01

Full Text Available Background. We developed a completely closed system based on gravity separation without centrifugation steps for separation of whole blood. With this new system we compared quality and stability of the processed blood components (PRC and plasma with respect to classical preparation. Furthermore the cost-effectiveness of this hollow fibre system was evaluated. Study Design and Methods. Whole blood collections of 15 regular blood donors were used for component preparation using the U shaped hollow fibre filter device. Results were compared to 15 whole blood preparations using centrifugation. The following parameters were evaluated: total hemoglobin, leukocyte counts, the serum concentration of total protein, lactate dehydrogenase (LDH and potassium. Furthermore ATIII, vWF and F VIII were analyzed at different timepoints. Results. packed red cells: the data directly after separation and after 42 days of storage are in line with the guidelines of the council of Europe. Plasma. all plasma quality data are in line with the guidelines of the council of Europe for quality assurance of plasma, except for a low protein amount (factor 0.75. Conclusion. Separation of whole blood on a clinical scale in this new closed system is feasible, however the plasma protein content must be optimized.

Modelling current transfer to cathodes in metal halide plasmas

International Nuclear Information System (INIS)

Benilov, M S; Cunha, M D; Naidis, G V

2005-01-01

This work is concerned with investigation of the main features of current transfer to cathodes under conditions characteristic of metal halide (MH) lamps. It is found that the presence of MHs in the gas phase results in a small decrease of the cathode surface temperature and of the near-cathode voltage drop in the diffuse mode of current transfer; the range of stability of the diffuse mode expands. Effects caused by a variation of the work function of the cathode surface owing to formation of a monolayer of alkali metal atoms on the surface are studied for particular cases where the monolayer is composed of sodium or caesium. It is found that the formation of the sodium monolayer affects the diffuse mode of current transfer only moderately and in the same direction that the presence of metal atoms in the gas phase affects it. Formation of the caesium monolayer produces a dramatic effect: the cathode surface temperature decreases very strongly, the diffuse-mode current-voltage characteristic becomes N-S-shaped

Atomic fluorescence spectrometry with the inductively coupled plasma

International Nuclear Information System (INIS)

Omenetto, N.; Winefordner, J.D.

1987-01-01

Atomic fluorescence spectrometry (AFS) is based on the radiational activation of atoms and ions produced in a suitable atomizer (ionizer) and the subsequent measurement of the resulting radiational deactivation, called fluorescence. Atomic fluorescence spectrometry has been of considerable interest to researchers in atomic spectrometry because of its use for both analytical and diagnostic purposes. Unfortunately, the analytical applications of AFS have suffered from the lack of commercial instrumentation until the recent marketing of the Baird multiple-element, hollow cathode lamp-excited inductively coupled plasma system. This chapter is concerned strictly with the use of the inductively coupled plasma (ICP) as a cell and as a source for AFS. Many of the major references concerning the ICP in analytical AFS are categorized in Table 9.1, along with several reviews and diagnostical studies. For more detailed discussions of the fundamental aspects of AFS, the reader is referred to previous reviews

A study of emission property and microstructure of rare earth oxide-molybdenum cermet cathode materials made by spark plasma sintering

International Nuclear Information System (INIS)

Wang Jinshu; Li Hongyi; Yang Sa; Cui Ying; Zhou Meiling

2004-01-01

A fast sintering method, spark plasma sintering (SPS) was used for the synthesis of rare earth oxide-molybdenum cathode material. The secondary emission property, microstructure, and phase constitution of materials have been studied in this paper. The experimental results show that the maximum secondary emission coefficient of this material can be high to 3.84, much higher than that of rare earth oxide-molybdenum cathode made by traditional sintering method. The grain size is less than 1 μm and rare earth distributed evenly in the material. After the material was activated at 1600 deg. C, a 4 μm layer of rare earth oxide which leads to the high secondary emission coefficient of the material, is formed on the surface of the cathode

Ion velocities in a micro-cathode arc thruster

International Nuclear Information System (INIS)

Zhuang Taisen; Shashurin, Alexey; Keidar, Michael; Beilis, Isak

2012-01-01

Ion velocities in the plasma jet generated by the micro-cathode arc thruster are studied by means of time-of-flight method using enhanced ion detection system (EIDS). The EIDS triggers perturbations (spikes) on arc current waveform, and the larger current in the spike generates denser plasma bunches propagating along with the mainstream plasma. The EIDS utilizes double electrostatic probes rather than single probes. The average Ti ion velocity is measured to be around 2×10 4 m/s without a magnetic field. It was found that the application of a magnetic field does not change ion velocities in the interelectrode region while leads to ion acceleration in the free expanding plasma plume by a factor of about 2. Ion velocities of about 3.5×10 4 m/s were detected for the magnetic field of about 300 mT at distance of about 100–200 mm from the cathode. It is proposed that plasma is accelerated due to Lorentz force. The average thrust is calculated using the ion velocity measurements and the cathode mass consumption rate, and its increase with the magnetic field is demonstrated.

Effects of cathode pulse at high frequency on structure and composition of Al2TiO5 ceramic coatings on Ti alloy by plasma electrolytic oxidation

International Nuclear Information System (INIS)

Yao Zhongping; Liu Yunfu; Xu Yongjun; Jiang Zhaohua; Wang Fuping

2011-01-01

Research highlights: → Al 2 TiO 5 in the coating on Ti alloy by PEO treatment changes with the increase of the cathode pulse, regardless of the amount and the grain size. → The cathode pulse brings about the decrease of γ-Al 2 O 3 and the increase of rutile TiO 2 in the coating. → The appropriate cathode pulse during PEO process is beneficial to reduce residual discharging channels and improve the density of the coating. - Abstract: The aim of this work is to investigate the effects of cathode pulse under high working frequency on structure and composition of ceramic coatings on Ti-6Al-4V alloys by plasma electrolytic oxidation (PEO). Ceramic coatings were prepared on Ti alloy by pulsed bi-polar plasma electrolytic oxidation in NaAlO 2 solution. The phase composition, morphology and element distribution in the coating were investigated by X-ray diffractometry, scanning electron microscopy and energy distribution spectroscopy, respectively. The coating was mainly composed of a large amount of Al 2 TiO 5 . As the cathode pulse was increased, the amount and grain size of Al 2 TiO 5 were first increased, and then decreased. γ-Al 2 O 3 in the coating was gradually decreased to nothing with the increase in the cathode pulse whereas rutile TiO 2 began to form in the coating. As opposed to the single-polar anode pulse mode, the cathode pulse reduced the thickness of the coatings. However, as the cathode pulse intensity continued to increase, the coating then became thicker regardless of cathode current density or pulse width. In addition, the residual discharging channels were reduced and the density of the coating was increased with the appropriate increase of the cathode pulse.

Fabrication of polymeric hollow nanospheres, hollow nanocubes and hollow plates

Science.gov (United States)

Cheng, Daming; Xia, Haibing; Chan, Hardy Sze On

2006-03-01

A facile strategy for fabricating polypyrrole-chitosan (PPy-CS) hollow nanostructures with different shapes (sphere, cube and plate) and a wide range of sizes (from 35 to 600 nm) is described. These hollow structures have been fabricated using silver bromide as a single template material for polymer nucleation and growth. PPy-CS hollow nanostructures are formed by reaction with an etching agent to remove the core. These hollow nanostructures have been extensively characterized using various techniques such as TEM, FT-IR, UV-vis, and XRD.

High-Rate and Long-Term Cycle Stability of Li-S Batteries Enabled by Li2S/TiO2-Impregnated Hollow Carbon Nanofiber Cathodes.

Science.gov (United States)

Wang, Xinran; Bi, Xuanxuan; Wang, Shaona; Zhang, Yi; Du, Hao; Lu, Jun

2018-05-16

The high theoretical energy density of lithium-sulfur (Li-S) batteries makes them an alternative battery technology to lithium ion batteries. However, Li-S batteries suffer from low sulfur loading, poor charge transport, and dissolution of lithium polysulfide. In our study, we use the lithiated S, Li 2 S, as the cathode material, coupled with electrospun TiO 2 -impregnated hollow carbon nanofibers (TiO 2 -HCFs), which serve as the conductive agent and protective barrier for Li 2 S in Li-S batteries. TiO 2 -HCFs provide much improved electron/ionic conductivity and serve as a physical barrier, which prevents the dissolution of lithium polysulfides. The Li 2 S/TiO 2 -HCF composite delivers a discharge capacity of 851 mA h g Li 2 S -1 at 0.1C and the bilayer TiO 2 -HCFs/Li 2 S/TiO 2 -HCF composite delivers a high specific capacity of 400 mA h g Li 2 S -1 at 5C.

Electrochemically Active Polymeric Hollow Fibers based on Poly(ether- b -amide)/Carbon Nanotubes

KAUST Repository

Cuevas, Carolina

2017-09-18

A simple and effective method to incorporate catalytic activity to a hollow fiber membrane is reported. Polyetherimide hollow fiber membranes were coated with a solution containing carboxyl-functionalized multi-walled carbon nanotubes and poly(ether-b-amide). Electron microscopy images confirmed the presence of a layer of percolating carbon nanotubes on the surface of the membranes. Cyclic voltammetry and linear swept voltammetry experiments showed that these membranes are able to drive the reactions of hydrogen evolution, and oxygen reduction, making them a cheaper, and greener substitute for platinum based cathodes in microbial bioelectrochemical systems. Water flux and molecular weight cut off experiments indicated that the electrochemically active coating layer does not affect the ultrafiltration performance of the membrane.

Electrochemically Active Polymeric Hollow Fibers based on Poly(ether- b -amide)/Carbon Nanotubes

KAUST Repository

Cuevas, Carolina; Kim, Dooli; Katuri, Krishna; Saikaly, Pascal; Nunes, Suzana Pereira

2017-01-01

A simple and effective method to incorporate catalytic activity to a hollow fiber membrane is reported. Polyetherimide hollow fiber membranes were coated with a solution containing carboxyl-functionalized multi-walled carbon nanotubes and poly(ether-b-amide). Electron microscopy images confirmed the presence of a layer of percolating carbon nanotubes on the surface of the membranes. Cyclic voltammetry and linear swept voltammetry experiments showed that these membranes are able to drive the reactions of hydrogen evolution, and oxygen reduction, making them a cheaper, and greener substitute for platinum based cathodes in microbial bioelectrochemical systems. Water flux and molecular weight cut off experiments indicated that the electrochemically active coating layer does not affect the ultrafiltration performance of the membrane.

Synthesis and properties of nanostructured dense LaB6 cathodes by arc plasma and reactive spark plasma sintering

International Nuclear Information System (INIS)

Zhou Shenlin; Zhang Jiuxing; Liu Danmin; Lin Zulun; Huang Qingzhen; Bao Lihong; Ma Ruguang; Wei Yongfeng

2010-01-01

Nanostructured polycrystalline LaB 6 ceramics were prepared by the reactive spark plasma sintering method, using boron nanopowders and LaH 2 powders with a particle size of about 30 nm synthesized by hydrogen dc arc plasma. The reaction mechanism of sintering, crystal structure, microstructure, grain orientations and properties of the materials were investigated using differential scanning calorimetry, X-ray diffraction, Neutron powder diffraction, Raman spectroscopy, transmission electron microscopy and electron backscattered diffraction. It is shown that nanostructured dense LaB 6 with a fibrous texture can be fabricated by SPS at a pressure of 80 MPa and temperature of 1300 deg. C for 5 min. Compared with the coarse polycrystalline LaB 6 prepared by traditional methods, the nanostructured LaB 6 bulk possesses both higher mechanical and higher thermionic emission properties. The Vickers hardness was 22.3 GPa, the flexural strength was 271.2 MPa and the maximum emission current density was 56.81 A cm -2 at a cathode temperature of 1600 deg. C.

Engineering Porous Polymer Hollow Fiber Microfluidic Reactors for Sustainable C-H Functionalization.

Science.gov (United States)

He, Yingxin; Rezaei, Fateme; Kapila, Shubhender; Rownaghi, Ali A

2017-05-17

Highly hydrophilic and solvent-stable porous polyamide-imide (PAI) hollow fibers were created by cross-linking of bare PAI hollow fibers with 3-aminopropyl trimethoxysilane (APS). The APS-grafted PAI hollow fibers were then functionalized with salicylic aldehyde for binding catalytically active Pd(II) ions through a covalent postmodification method. The catalytic activity of the composite hollow fiber microfluidic reactors (Pd(II) immobilized APS-grafted PAI hollow fibers) was tested via heterogeneous Heck coupling reaction of aryl halides under both batch and continuous-flow reactions in polar aprotic solvents at high temperature (120 °C) and low operating pressure. X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma (ICP) analyses of the starting and recycled composite hollow fibers indicated that the fibers contain very similar loadings of Pd(II), implying no degree of catalyst leaching from the hollow fibers during reaction. The composite hollow fiber microfluidic reactors showed long-term stability and strong control over the leaching of Pd species.

Plasma and Ion Sources in Large Area Coatings: A Review

Energy Technology Data Exchange (ETDEWEB)

Anders, Andre

2005-02-28

Efficient deposition of high-quality coatings often requires controlled application of excited or ionized particles. These particles are either condensing (film-forming) or assisting by providing energy and momentum to the film growth process, resulting in densification, sputtering/etching, modification of stress, roughness, texture, etc. In this review, the technical means are surveyed enabling large area application of ions and plasmas, with ion energies ranging from a few eV to a few keV. Both semiconductortype large area (single wafer or batch processing with {approx} 1000 cm{sup 2}) and in-line web and glass-coating-type large area (> 10{sup 7} m{sup 2} annually) are considered. Characteristics and differences between plasma and ion sources are explained. The latter include gridded and gridless sources. Many examples are given, including sources based on DC, RF, and microwave discharges, some with special geometries like hollow cathodes and E x B configurations.

Atomic and ionic density measurement by laser absorption spectroscopy of magnetized or non-magnetized plasmas

International Nuclear Information System (INIS)

Le Gourrierec, P.

1989-11-01

Laser absorption spectroscopy is an appreciated diagnostic in plasma physics to measure atomic and ionic densities. We used it here more specifically on metallic plasmas. Firstly, a uranium plasma was created in a hollow cathode. 17 levels of U.I and U.II (12 for U.I and 5 for U.II) are measured by this method. The results are compared with the calculated levels of two models (collisional-radiative and LTE). Secondly, the theory of absorption in presence of a magnetic field is recalled and checked. Then, low-density magnetized plasma produced on our ERIC experiment (acronym for Experiment of Resonance Ionic Cyclotron), have been diagnosed successfully. The use of this technique on a low density plasma has not yet been published to our knowledge. The transverse temperature and the density of a metastable atomic level of a barium plasma has been derived. The evolution of a metastable ionic level of this element is studied in terms of two source parameters (furnace temperature and injected hyperfrequency power) [fr

Modified Gold Electrode and Hollow Mn3O4 Nanoparticles as Electrode Materials for Microbial Fuel Cell Applications

Science.gov (United States)

Dhungana, Pramod

Microbial fuel cell (MFC) technology has attracted great attention in the scientific community as it offers the possibility of extraction of electricity from wide range of soluble and dissolved organic waste or renewable biomass, including sludge, waste water and cellulosic biomass. Microbial fuel cells are devices that utilize microbial metabolic processes to convert chemical energy via the oxidation of organic substances to produce electric current. MFCs consist of two chambers, an anode and cathode, separated by ion-permeable materials. The efficiency of producing electricity using the MFC depends on several factors such as immobilization of microorganisms on anode, mode of electron transfer, types of substrate/fuel and effectiveness of cathode materials for oxygen reduction reaction (ORR). In this work, in order to immobilize the microorganisms on anode materials, we have investigated the surface modification of gold electrode (anode) using alkyl dithiol and aryl thiol with glucose. The modification processes were characterized by using contact angle measurements and proton nuclear magnetic resonance (NMR). In order to study the effectiveness of cathode materials for ORR, we have synthesized hollow Mn3O 4 nanoparticles which are electrically very poor. Therefore, the hollow nanoparticles were mixed with electrically conductive multi-walled carbon nanotube as support and optimized the mixing process. This composite material shows enhanced ORR activity in all types of pH conditions. In future, we will focus to integrate anode and cathode in MFC to check its efficiency to produce electricity.

Honeycomblike large area LaB6 plasma source for Multi-Purpose Plasma facility

International Nuclear Information System (INIS)

Woo, Hyun-Jong; Chung, Kyu-Sun; You, Hyun-Jong; Lee, Myoung-Jae; Lho, Taihyeop; Choh, Kwon Kook; Yoon, Jung-Sik; Jung, Yong Ho; Lee, Bongju; Yoo, Suk Jae; Kwon, Myeon

2007-01-01

A Multi-Purpose Plasma (MP 2 ) facility has been renovated from Hanbit mirror device [Kwon et al., Nucl. Fusion 43, 686 (2003)] by adopting the same philosophy of diversified plasma simulator (DiPS) [Chung et al., Contrib. Plasma Phys. 46, 354 (2006)] by installing two plasma sources: LaB 6 (dc) and helicon (rf) plasma sources; and making three distinct simulators: divertor plasma simulator, space propulsion simulator, and astrophysics simulator. During the first renovation stage, a honeycomblike large area LaB 6 (HLA-LaB 6 ) cathode was developed for the divertor plasma simulator to improve the resistance against the thermal shock fragility for large and high density plasma generation. A HLA-LaB 6 cathode is composed of the one inner cathode with 4 in. diameter and the six outer cathodes with 2 in. diameter along with separate graphite heaters. The first plasma is generated with Ar gas and its properties are measured by the electric probes with various discharge currents and magnetic field configurations. Plasma density at the middle of central cell reaches up to 2.6x10 12 cm -3 , while the electron temperature remains around 3-3.5 eV at the low discharge current of less than 45 A, and the magnetic field intensity of 870 G. Unique features of electric property of heaters, plasma density profiles, is explained comparing with those of single LaB 6 cathode with 4 in. diameter in DiPS

Coprecipitation-assisted hydrothermal synthesis of PLZT hollow nanospheres

International Nuclear Information System (INIS)

Zhu, Renqiang; Zhu, Kongjun; Qiu, Jinhao; Bai, Lin; Ji, Hongli

2010-01-01

Lanthanum-modified lead zirconate titanate Pb 1-x La x (Zr 1-y Ti y )O 3 (PLZT) hollow nanospheres have been successfully prepared via a template-free hydrothermal method using the well-mixed coprecipitated precursors and the KOH mineralizer. The structure, composition, and morphology of the PLZT hollow nanospheres were characterized by XRD (X-ray diffraction), ICP (inductive coupled plasma emission spectrometer), FTIR (Fourier transform infrared spectra), TG/DTA (thermogravimetric analysis and differential thermal analysis), TEM (transmission electron microscopy) and SEAD (selected area diffraction). The results show that the composition and the morphology control of the PLZT products are determined by the KOH concentration. The PLZT hollow nanospheres with uniform size of about 4 nm were synthesized in the presence of 5 M KOH. The crystalline nanoparticles can be prepared at dilute KOH, in contrast to the amorphous powders prepared at concentrated KOH. Formation mechanisms of the PLZT hollow nanospheres are also discussed.

Experimental investigation of cathode spots and plasma jets behavior subjected to two kinds of axial magnetic field electrodes

International Nuclear Information System (INIS)

Wang, Lijun; Deng, Jie; Zhou, Xin; Jia, Shenli; Qian, Zhonghao; Shi, Zongqian

2016-01-01

In this paper, cathode spot plasma jet (CSPJ) rotation and cathode spots behavior subjected to two kinds of large diameter axial magnetic field (AMF) electrode (cup-shaped and coil-shaped) are studied and analyzed based on experiments. The influence of gap distances on the CSPJ rotational behavior is analyzed. Experimental results show that CSPJ rotational phenomena extensively exist in the vacuum interrupters, and CSPJ rotational direction is along the direction of composite magnetic field (mainly the combination of the axial and azimuthal components). For coil-shaped and cup-shaped AMF electrodes, the rotational or inclination phenomena before the current peak value are much more significant than that after current peak value (for the same arc current), which is related to the larger ratio of azimuthal magnetic field B_t and AMF B_z (B_t/B_z). With the increase of the gap distance, the AMF strength decreases, when the arc current is kept as constant, the azimuthal magnetic field is kept invariable, the ratio between azimuthal magnetic field and AMF is increased, which results in the increase of rotational effect. For cathode spots motion, compared with cup-shaped electrode, coil-shaped electrode has the inverse AMF direction. The Robson drift direction of cathode spots of coil-shaped electrode is opposite to that of cup-shaped electrode. With the increase of gap distance, the Robson angle is decreased, which is associated with the reduced AMF strength. Erosion imprints of anode and cathode are also related to the CSPJ rotational phenomena and cathode spots behavior. The noise of arc voltage in the initial arcing stage is related to the weaker AMF.

Experimental investigation of cathode spots and plasma jets behavior subjected to two kinds of axial magnetic field electrodes

Energy Technology Data Exchange (ETDEWEB)

Wang, Lijun; Deng, Jie; Zhou, Xin; Jia, Shenli; Qian, Zhonghao; Shi, Zongqian [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Xi' an 710049 (China)

2016-04-15

In this paper, cathode spot plasma jet (CSPJ) rotation and cathode spots behavior subjected to two kinds of large diameter axial magnetic field (AMF) electrode (cup-shaped and coil-shaped) are studied and analyzed based on experiments. The influence of gap distances on the CSPJ rotational behavior is analyzed. Experimental results show that CSPJ rotational phenomena extensively exist in the vacuum interrupters, and CSPJ rotational direction is along the direction of composite magnetic field (mainly the combination of the axial and azimuthal components). For coil-shaped and cup-shaped AMF electrodes, the rotational or inclination phenomena before the current peak value are much more significant than that after current peak value (for the same arc current), which is related to the larger ratio of azimuthal magnetic field B{sub t} and AMF B{sub z} (B{sub t}/B{sub z}). With the increase of the gap distance, the AMF strength decreases, when the arc current is kept as constant, the azimuthal magnetic field is kept invariable, the ratio between azimuthal magnetic field and AMF is increased, which results in the increase of rotational effect. For cathode spots motion, compared with cup-shaped electrode, coil-shaped electrode has the inverse AMF direction. The Robson drift direction of cathode spots of coil-shaped electrode is opposite to that of cup-shaped electrode. With the increase of gap distance, the Robson angle is decreased, which is associated with the reduced AMF strength. Erosion imprints of anode and cathode are also related to the CSPJ rotational phenomena and cathode spots behavior. The noise of arc voltage in the initial arcing stage is related to the weaker AMF.

Microfabricated hollow microneedle array using ICP etcher

Science.gov (United States)

Ji, Jing; Tay, Francis E. H.; Miao, Jianmin

2006-04-01

This paper presents a developed process for fabrication of hollow silicon microneedle arrays. The inner hollow hole and the fluidic reservoir are fabricated in deep reactive ion etching. The profile of outside needles is achieved by the developed fabrication process, which combined isotropic etching and anisotropic etching with inductively coupled plasma (ICP) etcher. Using the combination of SF6/O2 isotropic etching chemistry and Bosch process, the high aspect ratio 3D and high density microneedle arrays are fabricated. The generated needle external geometry can be controlled by etching variables in the isotropic and anisotropic cases.

Microfabricated hollow microneedle array using ICP etcher

International Nuclear Information System (INIS)

Ji Jing; Tay, Francis E H; Miao Jianmin

2006-01-01

This paper presents a developed process for fabrication of hollow silicon microneedle arrays. The inner hollow hole and the fluidic reservoir are fabricated in deep reactive ion etching. The profile of outside needles is achieved by the developed fabrication process, which combined isotropic etching and anisotropic etching with inductively coupled plasma (ICP) etcher. Using the combination of SF 6 /O 2 isotropic etching chemistry and Bosch process, the high aspect ratio 3D and high density microneedle arrays are fabricated. The generated needle external geometry can be controlled by etching variables in the isotropic and anisotropic cases

Microfabricated hollow microneedle array using ICP etcher

Energy Technology Data Exchange (ETDEWEB)

Ji Jing [Mechanical Engineering National University of Singapore, 119260, Singapore (Singapore); Tay, Francis E H [Mechanical Engineering National University of Singapore, 119260, Singapore (Singapore); Miao Jianmin [MicroMachines Center, School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore)

2006-04-01

This paper presents a developed process for fabrication of hollow silicon microneedle arrays. The inner hollow hole and the fluidic reservoir are fabricated in deep reactive ion etching. The profile of outside needles is achieved by the developed fabrication process, which combined isotropic etching and anisotropic etching with inductively coupled plasma (ICP) etcher. Using the combination of SF{sub 6}/O{sub 2} isotropic etching chemistry and Bosch process, the high aspect ratio 3D and high density microneedle arrays are fabricated. The generated needle external geometry can be controlled by etching variables in the isotropic and anisotropic cases.

Cold cathode arc model in mercury discharges

International Nuclear Information System (INIS)

Li, Y.M.; Byszewski, W.W.; Budinger, A.B.

1990-01-01

Voltage/current characteristics measured during the starting of metal halide lamps indicate a low voltage discharge when condensates (mainly mercury) are localized on the electrodes. In this case, even with a cold cathode which does not emit electrons, the current is very high and voltage across the lamp drops to about 15 to 20 V. This type of discharge is similar to the cold cathode mercury vapor arc found in mercury pool rectifiers. The cathode sheath in the mercury vapor arc is characterized by very small cathode spot size, on the order of 10 -c cm 2 , very high current density of about 10 6 A/cm 2 and very low cathode fall of approximately 10 volts. The discharge is modified and generalized to describe the cathode phenomena in the cold cathode mercury vapor arc. The sensitivity of calculated discharge parameters with respect to such modifications were examined. Results show that the cathode fall voltage remains fairly constant (7-8 volts) with large fractional variations of metastable mercury atoms bombarding the cathode. This result compares very well with experimental waveforms when anode fall and plasma voltage approximations are incorporated

Direct fabrication of metal-free hollow graphene balls with a self-supporting structure as efficient cathode catalysts of fuel cell

Energy Technology Data Exchange (ETDEWEB)

Lu, Yanqi; Liu, Mingda; Nie, Huagui, E-mail: huaguinie@126.com; Gu, Cancan; Liu, Ming; Yang, Zhi, E-mail: yang201079@126.com; Yang, Keqin; Chen, Xi’an; Huang, Shaoming, E-mail: smhuang@wzu.edu.cn [Wenzhou University, Nanomaterials and Chemistry Key Laboratory (China)

2016-06-15

Despite the good progress in developing carbon catalysts for oxygen reduction reaction (ORR), the current metal-free carbon catalysts are still far from satisfactory for large-scale applications of fuel cell. Developing hollow graphene balls with a self-supporting structure is considered to be an ideal method to inhibit graphene stacking and improve their catalytic performance. Herein, we fabricated metal-free hollow graphene balls with a self-supporting structure, through using a new strategy that involves direct metal-free catalytic growth from assembly of SiO{sub 2} spheres. To our knowledge, although much researches involving the synthesis of graphene balls have been reported, investigations into the direct metal-free catalytic growth of hollow graphene balls are rare. Furthermore, the electrocatalytic performance shows that the resulting hollow graphene balls have significantly high catalytic activity. More importantly, such catalysts also possess much improved stability and better methanol tolerance in alkaline media during the ORR compared with commercial Pt/C catalysts. The outstanding performances coupled with an easy and inexpensive preparing method indicated the great potential of the hollow graphene balls with a self-supporting structure in large-scale applications of fuel cell.Graphical AbstractHollow graphene balls with a self-supporting structure have been successfully fabricated, through using a new strategy that involves direct metal-free catalytic growth from 3D assembly of SiO{sub 2} spheres. The hollow graphene balls can exhibit a high catalytic activity, long-term stability, and an excellent methanol tolerance for the oxygen reduction reaction.

Direct fabrication of metal-free hollow graphene balls with a self-supporting structure as efficient cathode catalysts of fuel cell

International Nuclear Information System (INIS)

Lu, Yanqi; Liu, Mingda; Nie, Huagui; Gu, Cancan; Liu, Ming; Yang, Zhi; Yang, Keqin; Chen, Xi’an; Huang, Shaoming

2016-01-01

Despite the good progress in developing carbon catalysts for oxygen reduction reaction (ORR), the current metal-free carbon catalysts are still far from satisfactory for large-scale applications of fuel cell. Developing hollow graphene balls with a self-supporting structure is considered to be an ideal method to inhibit graphene stacking and improve their catalytic performance. Herein, we fabricated metal-free hollow graphene balls with a self-supporting structure, through using a new strategy that involves direct metal-free catalytic growth from assembly of SiO_2 spheres. To our knowledge, although much researches involving the synthesis of graphene balls have been reported, investigations into the direct metal-free catalytic growth of hollow graphene balls are rare. Furthermore, the electrocatalytic performance shows that the resulting hollow graphene balls have significantly high catalytic activity. More importantly, such catalysts also possess much improved stability and better methanol tolerance in alkaline media during the ORR compared with commercial Pt/C catalysts. The outstanding performances coupled with an easy and inexpensive preparing method indicated the great potential of the hollow graphene balls with a self-supporting structure in large-scale applications of fuel cell.Graphical AbstractHollow graphene balls with a self-supporting structure have been successfully fabricated, through using a new strategy that involves direct metal-free catalytic growth from 3D assembly of SiO_2 spheres. The hollow graphene balls can exhibit a high catalytic activity, long-term stability, and an excellent methanol tolerance for the oxygen reduction reaction

Ignition Features of Plasma-Beam Discharge in Gas-Discharge Electron Gun Operation

Directory of Open Access Journals (Sweden)

Valery A. Tutyk

2013-01-01

Full Text Available The current paper presents the results of experimental researches to determine the mode features of plasma-beam discharge (PBD generation by an electron beam injected by a low-vacuum gasdischarge electron gun (LGEG with the cold cathode and hollow anode on the basis of the high-voltage glow discharge and in the range of helium pressure of P ? 10 ÷ 130 Pa. The PBD boundaries and their dependences on parameters of an electron beam are found. The influence of PBD on parameters of low-vacuum gas-discharge electron gun is revealed. It causes an avalanche increase of electron beam current and burning of plasma-beam discharge in the whole space of the vacuum chamber volume and generation of electromagnetic radiation is revealed. Achieved results will be used for implementation of various vacuum technologies in the medium of reaction gas and generated electromagnetic radiation.

Study of the optical properties of deposited thin films on glass of HMDSO(C6H18Si2O) plasma

International Nuclear Information System (INIS)

Saloum, S.; Naddaf, M.

2007-06-01

Deposition of amorphous silicone like (Si:Ox:Cy:Hz) thin films in a remote RF hollow cathode discharge plasma using HMDSO (C 6 H 1 8Si 2 O) as monomer and Ar as feed gas, has been investigated for films optical constants as a function of RF power (100-300 W) and precursor flow rate (1-10 sccm), using different substrates: Quartz, BK7, and Glass. The optical constants (refractive index, extinction coefficient and dielectric constant) have been obtained by reflection/transmission measurements in the range 300-700 nm. The optical energy-band gap Eg and the optical-absorption tail E have been estimated from optical absorption spectra. The results were interpreted using plasma diagnostic by optical emission spectroscopy.(author)

Time-resolved and doppler-reduced laser spectroscopy on atoms

International Nuclear Information System (INIS)

Bergstroem, H.

1991-10-01

Radiative lifetimes have been studied in neutral boron, carbon, silicon and strontium, in singly ionized gadolinium and tantalum and in molecular carbon monoxide and C 2 . The time-resolved techniques were based either on pulsed lasers or pulse-modulated CW lasers. Several techniques have been utilized for the production of free atoms and ions such as evaporation into an atomic beam, sputtering in hollow cathodes and laser-produced plasmas. Hyperfine interactions in boron, copper and strontium have been examined using quantum beat spectroscopy, saturation spectroscopy and collimated atomic beam spectroscopy. Measurement techniques based on effusive hollow cathodes as well as laser produced plasmas in atomic physics have been developed. Investigations on laser produced plasmas using two colour beam deflection tomography for determination of electron densities have been performed. Finally, new possibilities for view-time-expansion in light-in-flight holography using mode-locked CW lasers have been demonstrated. (au)

Experimental observations of electron-backscatter effects from high-atomic-number anodes in large-aspect-ratio, electron-beam diodes

Energy Technology Data Exchange (ETDEWEB)

Cooperstein, G; Mosher, D; Stephanakis, S J; Weber, B V; Young, F C [Naval Research Laboratory, Washington, DC (United States); Swanekamp, S B [JAYCOR, Vienna, VA (United States)

1997-12-31

Backscattered electrons from anodes with high-atomic-number substrates cause early-time anode-plasma formation from the surface layer leading to faster, more intense electron beam pinching, and lower diode impedance. A simple derivation of Child-Langmuir current from a thin hollow cathode shows the same dependence on the diode aspect ratio as critical current. Using this fact, it is shown that the diode voltage and current follow relativistic Child-Langmuir theory until the anode plasma is formed, and then follows critical current after the beam pinches. With thin hollow cathodes, electron beam pinching can be suppressed at low voltages (< 800 kV) even for high currents and high-atomic-number anodes. Electron beam pinching can also be suppressed at high voltages for low-atomic-number anodes as long as the electron current densities remain below the plasma turn-on threshold. (author). 8 figs., 2 refs.

Synthesis of carbon-coated Na2MnPO4F hollow spheres as a potential cathode material for Na-ion batteries

Science.gov (United States)

Wu, Ling; Hu, Yong; Zhang, Xiaoping; Liu, Jiequn; Zhu, Xing; Zhong, Shengkui

2018-01-01

Hollow sphere structure Na2MnPO4F/C composite is synthesized through spray drying, following in-situ pyrolytic carbon coating process. XRD results indicate that the well crystallized composite can be successfully synthesized, and no other impurity phases are detected. SEM and TEM results reveal that the Na2MnPO4F/C samples show intact hollow spherical architecture, and the hollow spherical shells with an average thickness of 150 nm-250 nm are composed of nanosized primary particles. Furthermore, the amorphous carbon layer is uniformly coated on the surface of the hollow sphere, and the nanosized Na2MnPO4F particles are well embedded in the carbon networks. Consequently, the hollow sphere structure Na2MnPO4F/C shows enhanced electrochemical performance. Especially, it is the first time that the obvious potential platforms (∼3.6 V) are observed during the charge and discharge process at room temperature.

Negative hydrogen ion beam extraction from an AC heated cathode driven Bernas-type ion source

Energy Technology Data Exchange (ETDEWEB)

Okano, Y.; Miyamoto, N.; Kasuya, T.; Wada, M.

2015-04-08

A plasma grid structure was installed to a Bernas-type ion source used for ion implantation equipment. A negative hydrogen (H{sup −}) ion beam was extracted by an AC driven ion source by adjusting the bias to the plasma grid. The extracted electron current was reduced by positively biasing the plasma grid, while an optimum plasma grid bias voltage for negative ion beam extraction was found to be positive 3 V with respect to the arc chamber. Source operations with AC cathode heating show extraction characteristics almost identical to that with DC cathode heating, except a minute increase in H{sup −} current at higher frequency of cathode heating current.

High rate performance of LiMn2O4 cathodes for lithium ion batteries synthesized by low temperature oxygen plasma assisted sol–gel process

International Nuclear Information System (INIS)

Chen, C.-L.; Chiu, K.-F.; Chen, Y.-R.; Chen, C.C.; Lin, H.C.; Chiang, H.Y.

2013-01-01

Nano-crystalline LiMn 2 O 4 thin films have been synthesized by the sol–gel process at low temperature (623 K). The low temperature prepared films are treated by a direct current pulsed oxygen plasma, and tested as cathodes for lithium batteries. The plasma treated films are able to sustain charge–discharge cycles under significant high current density of up to 5.4 A/g corresponding to 45 C for battery operation. The capacity ratio for discharging at 1.2 A/g and 0.024 A/g is over 65%, indicating low internal resistance, which meets the requirement of fast charge and discharge for electric vehicles. The stable high current density performances can be attributed to the formation of a dense surface morphology that is induced by the plasma irradiation. The formation of the surface morphology results in the more uniform current distribution on the film surface, which decreases the interface charge transfer resistances as measured by the electrochemical impedance spectra. - Highlights: • A low temperature process has been used to synthesize LiMn 2 O 4 thin films. • Plasma treatment can reduce the interface charge transfer resistances for LiMn 2 O 4 . • LiMn 2 O 4 cathodes treated by plasma treatment can deliver high rate capability

Cathode and ion-luminescence of Eu:ZnO thin films prepared by reactive magnetron sputtering and plasma decomposition of non-volatile precursors

Energy Technology Data Exchange (ETDEWEB)

Gil-Rostra, Jorge [Instituto de Ciencia de Materiales de Sevilla, CSIC, Univ. Sevilla, C/Américo Vespucio 49, E-41092 Sevilla (Spain); Ferrer, Francisco J. [Centro Nacional de Aceleradores, CSIC, Univ. Sevilla, Av. Thomas A. Edison 7, E-41092 Sevilla (Spain); Martín, Inocencio R. [Departamento de Física Fundamental y Experimental, Electrónica y Sistemas, U. La Laguna, C/Astrofísico Francisco Sánchez s/n, E-38206 La Laguna, Santa Cruz de Tenerife (Spain); González-Elipe, Agustín R.; Yubero, Francisco [Instituto de Ciencia de Materiales de Sevilla, CSIC, Univ. Sevilla, C/Américo Vespucio 49, E-41092 Sevilla (Spain)

2016-10-15

This paper reports the luminescent behavior of Eu:ZnO thin films prepared by an one-step procedure that combines reactive magnetron sputtering deposition of ZnO with the plasma activated decomposition of a non-volatile acetylacetonate precursor of Eu sublimated in an effusion cell. Chemical composition and microstructure of the Eu:ZnO thin films have been characterized by several methods and their photo-, cathode- and ion-luminescent properties studied as a function of Eu concentration. The high transparency and well controlled optical properties of the films have demonstrated to be ideal for the development of cathode- and ion- luminescence sensors.

Explosive emission cathode on the base of carbon plastic fibre

International Nuclear Information System (INIS)

Korenev, S.A.; Baranov, A.M.; Kostyuchenko, S.V.; Chernenko, N.M.

1989-01-01

A fabrication process for explosive emission cathodes on the base of carbon plastic fibre of practically any geometrical shape and dimensions is developed. Experimental studies of electron beam current collection from cathodes, 2cm in diameter, at voltages across the diode of 10 and 150-250kV. It is shown that the ignition voltage for cathode plasma is ∼2kV at the interelectrode diode gap of 5mm and residual gas pressure of ∼5x10 -5 Torr. The carbon-fibre cathode, fabricated in this way, provides more stable current collection of an electron beam (without oscillations) than other cathodes

Magnetic filtered plasma deposition and implantation technique

CERN Document Server

Zhang Hui Xing; Wu Xian Ying

2002-01-01

A high dense metal plasma can be produced by using cathodic vacuum arc discharge technique. The microparticles emitted from the cathode in the metal plasma can be removed when the metal plasma passes through the magnetic filter. It is a new technique for making high quality, fine and close thin films which have very widespread applications. The authors describe the applications of cathodic vacuum arc technique, and then a filtered plasma deposition and ion implantation system as well as its applications

Multiple soliton compression stages in mid-IR gas-filled hollow-core fibers

DEFF Research Database (Denmark)

Habib, Md Selim; Markos, Christos; Bang, Ole

2017-01-01

The light confinement inside hollow-core (HC) fibers filled with noble gases constitutes an efficient route to study interesting soliton-plasma dynamics [1]. More recently, plasma-induced soliton splitting at the self-compression point was observed in a gas-filled fiber in the near-IR [2]. However...

Simulation of electron and ion bipolar flow in high current diode with magnetic insulation

International Nuclear Information System (INIS)

Vrba, P.; Engelko, V.I.

1990-08-01

Numerical simulation of the formation of the collector ion flow in a magnetically insulated ion diode (MID) with a hollow cylindrical and cone-shaped cathode was studied. Such cathodes are often used for the production of tubular high current microsecond electron beams. The ions, emitted by the collector and born as a result of ionization of the residual gas by the electron beam, are focused into the cathode plasma region. This effect can adversely influence the diode operation

The explosive cathode on the base of carbon-fibrous plastic material

International Nuclear Information System (INIS)

Korenev, S.A.; Baranov, A.M.; Kostyuchenko, S.V.; Chernenko, N.M.

1988-01-01

Production process of exploseve cathodes on the base of carbon-fibrous plastic material of any geometric form and size is discussed. Experimental study of current take-off from cathodes with diameter 2 cm of 10 kV and 150-250 kV voltage are given. It is shown that ignition voltage of cathode plasma is 2 kV with 5 mm gap electrode of diode and 5 ·10 -5 Tor pressure of residual gas. It is shown that carbon-fibrous cathode, made by this technology, provides more stable current take-off electron beam (withoud oscillations) in comparison with other cathodes

Study on the emission characteristics of cathodes in an ionized gas flow

International Nuclear Information System (INIS)

Maslennikov, N.M.

1975-01-01

Emission characteristics of molybdenum, tungsten and tantalum cathodes in a flow of argon and argon-potassium plasma with gas pressure of 0.04 atm, 1 atm and 0.25 atm were investigated. Gas was heated in a plasmatron. Measuring electrodes were arranged across the gas flow. Investigations in an argon plasma were carried out with the object of comparing of current-voltage dependences for potassium-activated and nonactivated cathodes. In all cases the current-voltage characteristics were growing. No saturation was observed of a current between accurent electrodes. The increase of a current between the cathodes due to the thermionic emission from the cathode began to effect at the cathode temperature of 2.470 K. The work function was found to be 5 to 5.2 ev. The comparison of the results obtained experimentally in the paper show a qualitative coincidence with calculations by some authors and a discrepancy with theoretical conceptions of other authors

Electromagnetic separator of plasma

International Nuclear Information System (INIS)

Gasilin, V.V.; Nezovibatko, Yu.N.; Poklepach, G.S.; Shvets, O.M.; Taran, V.S.; Tereshin, V.I.

2005-01-01

The progress in the widespread utilization of the PVD methods is determined in many respects by the plasma quality and, therefore, the necessity of an application of plasma separators, in particular magnetic separators. One needs to note that traditional magnetic separators have a number of problems their using, namely their unwieldiness, the presence of the isolated cameras and so on. We have proposed, manufactured and investigated the simple separator of plasma that doesn't require using additional cameras. As a source of metallic plasma the standard cathode vaporizer in the installation 'BULAT 6' was in use. Plasma stream from the cathode flowed through the not protected by isolation spiral solenoid. The solenoid input (from the cathode side) was under floating potential. The solenoid output was connected to the autonomous power supply system. The solenoid was prepared with stride winding and 90 degree turn. The solenoid current was 20-90 A and the solenoid voltage with respect to the vessel (earth) was +15 V. In this case drifting charged particles could freely fly out from the interior solenoid region to its boundary. The glow of the turned flow of plasma was observed during the supplying of the cathode and the solenoid. Plasma flow was separated from the coils and extended along the axis of solenoid. One can assume that this device ensures radial electric with respect to the bulk of plasma (the diameter of the bulk of plasma is comparable with the cathode diameter), the toroidal magnetic field, produced by solenoid, was of an order of 20 Oe. Magnetic field strength was sufficient for the magnetization of electrons, but it was rather small for magnetizing the ions and charged micro-droplets. The experiments carried out with aluminum cathode on the deposition of coatings at the stainless steel substrate have shown the high effectiveness of this separator operation. Coatings without droplets were obtained also on the glass substrate with HF- displacement

Upper Hybrid Resonance of Microwaves with a Large Magnetized Plasma Sheet

International Nuclear Information System (INIS)

Huo Wenqing; Guo Shijie; Ding Liang; Xu Yuemin

2013-01-01

A large magnetized plasma sheet with size of 60 cm × 60 cm × 2 cm was generated by a linear hollow cathode discharge under the confinement of a uniform magnetic field generated by a Helmholtz Coil. The microwave transmission characteristic of the plasma sheet was measured for different incident frequencies, in cases with the electric field polarization of the incident microwave either perpendicular or parallel to the magnetic field. In this measurement, parameters of the plasma sheet were changed by varying the discharge current and magnetic field intensity. In the experiment, upper hybrid resonance phenomena were observed when the electric field polarization of the incident wave was perpendicular to the magnetic field. These resonance phenomena cannot be found in the case of parallel polarization incidence. This result is consistent with theoretical consideration. According to the resonance condition, the electron density values at the resonance points are calculated under various experimental conditions. This kind of resonance phenomena can be used to develop a specific method to diagnose the electron density of this magnetized plasma sheet apparatus. Moreover, it is pointed out that the operating parameters of the large plasma sheet in practical applications should be selected to keep away from the upper hybrid resonance point to prevent signals from polarization distortion

Suspension plasma spraying of La0.6Sr0.4Co0.2Fe0.8O3-δ cathodes: Influence of carbon black pore former on performance and degradation

Science.gov (United States)

Fan, E. S. C.; Kuhn, J.; Kesler, O.

2016-06-01

Suspension plasma spray deposition is utilized to fabricate solid oxide fuel cell cathodes with minimal material decomposition. Adding carbon black as a pore former to the feedstock suspension results in smoother and more porous coatings, but over the range of carbon black concentrations studied, has little impact on the overall symmetrical cell performance. The cathode made with a suspension containing 25 wt% carbon has the highest deposition efficiency and a polarization resistance of 0.062 Ωcm2 at 744 °C. This cathode is tested for 500 h, and it is observed that adding an SDC interlayer between the YSZ electrolyte and the cathode(s) and/or coating the metal substrate with lanthanum chromite decrease the rate of performance degradation.

Charge exchange induced X-ray transitions of hollow ions in laser field ionized plasmas

International Nuclear Information System (INIS)

Rosmej, F.B.; Hoffmann, D.H.H.; Faenov, A. Ya.; Pikuz, T.A.; Magunov, A.I.; Skobelev, I.Yu.; Auguste, T.; D'Oliveira, P.; Hulin, S.; Monot, P.

2000-01-01

Double electron charge exchange is proposed for the formation of hollow He-like ions when laser field ionized nuclei penetrate into the residual gas. Using transitions from different configurations in hollow ions a method for the determination of the electron temperature in the long lasting recombination phase is developed

Optimization of cathodic arc deposition and pulsed plasma melting techniques for growing smooth superconducting Pb photoemissive films for SRF injectors

Science.gov (United States)

Nietubyć, Robert; Lorkiewicz, Jerzy; Sekutowicz, Jacek; Smedley, John; Kosińska, Anna

2018-05-01

Superconducting photoinjectors have a potential to be the optimal solution for moderate and high current cw operating free electron lasers. For this application, a superconducting lead (Pb) cathode has been proposed to simplify the cathode integration into a 1.3 GHz, TESLA-type, 1.6-cell long purely superconducting gun cavity. In the proposed design, a lead film several micrometres thick is deposited onto a niobium plug attached to the cavity back wall. Traditional lead deposition techniques usually produce very non-uniform emission surfaces and often result in a poor adhesion of the layer. A pulsed plasma melting procedure reducing the non-uniformity of the lead photocathodes is presented. In order to determine the parameters optimal for this procedure, heat transfer from plasma to the film was first modelled to evaluate melting front penetration range and liquid state duration. The obtained results were verified by surface inspection of witness samples. The optimal procedure was used to prepare a photocathode plug, which was then tested in an electron gun. The quantum efficiency and the value of cavity quality factor have been found to satisfy the requirements for an injector of the European-XFEL facility.

An explosive-emitter cathode produced using the heavy ion track technique

International Nuclear Information System (INIS)

Akap'ev, G.N.; Korenev, S.A.

1988-01-01

A cathode based on thin metallic foils with a homogeneous needle surface is described. The cathode was manufactured using the heavy ion track technique which permits the production of cathodes with an unlimited area and a needle density ranging from about 10 3 to 10 9 needles per cm 2 . An electron gun using this type of cathode has a current of 200-900 A and an energy of 100-300 keV. The cross section of the electron beam is fairly uniform. It is shown that needle emitters of similar shape and size play the principal role in forming a homogeneous cathode plasma

Effect of high Xe-concentration in a plasma display panel with a SrCaO cold cathode

International Nuclear Information System (INIS)

Uchida, Giichiro; Kajiyama, Hiroshi; Shinoda, Tsutae; Uchida, Satoshi; Akiyama, Toshiyuki

2010-01-01

We present here measurements of high Xe-contents plasma display panel (PDP) with SrCaO cold cathode. Luminous efficacy (η) shows a two-step increase with Xe-concentration in Ne/Xe gas mixture: η drastically increases up to Xe-concentration of 30% (Xe: 30%), and then attains 5 lm/W at the highest Xe-concentration of Xe: 100%. The high performance PDP with Xe: 100% can be operated at low applied voltage between 230 and 377 V due to the high secondary electron emission from the SrCaO cathode. Emission measurements clearly show the change in discharge characteristics at Xe: 30%, where the discharge changes from a Ne/Xe mixture discharge to an almost pure Xe discharge, and the vacuum ultraviolet (VUV) radiation from the combination of resonance and excimer radiations to only excimer radiation. Theoretical analysis solving Boltzmann equation for electron demonstrates that increasing Xe-concentration enhances the collision frequency for electron impact excitation directly from ground state to lower levels concerned with the VUV radiation, resulting in a drastic increase in luminous efficacy up to Xe: 30%. Also, one-dimensional fluid simulation of a Ne/Xe dielectric barrier discharge clearly shows that a combination of high secondary electron emission cathode and high Xe-concentration is quite effective for high VUV radiation efficiency because it induces a drastic increase in electron-heating efficiency.

Heater Validation for the NEXT-C Hollow Cathodes

Science.gov (United States)

Verhey, Timothy R.; Soulas, George C.; Mackey, Jonathan A.

2018-01-01

Swaged cathode heaters whose design was successfully demonstrated under a prior flight project are to be provided by the NASA Glenn Research Center for the NEXT-C ion thruster being fabricated by Aerojet Rocketdyne. Extensive requalification activities were performed to validate process controls that had to be re-established or revised because systemic changes prevented reuse of the past approaches. A development batch of heaters was successfully fabricated based on the new process controls. Acceptance and cyclic life testing of multiple discharge and neutralizer sized heaters extracted from the development batch was initiated in August, 2016, with the last heater completing testing in April, 2017. Cyclic life testing results substantially exceeded the NEXT-C thruster requirement as well as all past experience for GRC-fabricated units. The heaters demonstrated ultimate cyclic life capability of 19050 to 33500 cycles. A qualification batch of heaters is now being fabricated using the finalized process controls. A set of six heaters will be acceptance and cyclic tested to verify conformance to the behavior observed with the development heaters. The heaters for flight use will be then be provided to the contractor from the remainder of the qualification batch. This paper summarizes the fabrication process control activities and the acceptance and life testing of the development heater units.