New Type Of Discharge Research Articles

Mechanism of low-temperature helical streamer discharge driven by pulsed electromagnetic field

Under the condition of specific pulsed discharge parameters, the discharge mode conversion of the low-temperature plasma jet discharge channel that originally propagates along a straight line will occur, forming a three-dimensional helical plasma channel. Unlike the traditional helical wave discharge, there are no factors such as an external constant magnetic field that destroys the poloidal symmetry of the dielectric tube, and the chiral direction of the helical streamer will change with the discharge parameters. In order to understand in depth the electromagnetic mechanism of the helical structure in the plasma jet, and the source and influencing factors of the poloidal electric field that leads to the helical shape and determines the chirality in this new type of discharge, we analyze the complex characteristics and electromagnetic mechanism of the helical streamer, such as the chiral direction, pitch, branching, by establishing a self-consistent plasma theoretical model. It is found that the phase of the poloidal wave mode has an effect on the chiral selection of the helical streamer, that the electron density has an influence on the pitch of the streamer, and that the repetition frequency has an effect on the bifurcation point. The above discharge characteristics and their influencing factors are of scientific significance in exploring the interaction mechanism of electromagnetic wave and plasma, and also in providing experimental and theoretical support for the chiral application of low-temperature plasma.

Study on n-hexadecane cracking with introducing water by pulsed discharge in liquid

A hollow needle-plate pulsed plasma reactor was designed to figure out a suitable discharge type for heavy oil model compound (n-hexadecane) cracking. The characteristics of n-hexadecane under the action of pulsed discharge in liquid after the injection of water were explored. The results show that three types of discharge can be obtained through U-I waveform and discharge images: corona discharge, spark-like discharge, and spark discharge. Based on these discharge types, the influence of applied voltage and electrode distance on the liquid conversion rate and selectivity is further explored. Considering these two indicators, the electrode distance of 5.5 mm and spark-like discharge of 9–14 kV are the most suitable conditions. The conversion and the selectivity of treated liquid hydrocarbons are 5.27% and 75.42% when the duration time of plasma treatment is 7 min, respectively. According to the distribution of hydrocarbons in the liquid product, it is found that the formation of dodecane and pentadecane can be used as one of the signals of upgrading. This research provides a new method for heavy hydrocarbon cracking and discovers a new type of discharge between corona and spark discharge.

Evolution of the radial structure of a negative corona during its transformation into a glow discharge and a spark

With the proper stabilization of a negative corona, it is possible to increase the threshold current at which the corona discharge in the point-plane gap in air transforms into a spark. Then, in the current range corresponding to the transition region between the corona discharge and the spark, a new type of discharge arises—an atmospheric-pressure diffuse glow discharge. The transformation of the negative corona into a glow discharge and then into a spark is accompanied by the rearrangement of the discharge structure. The experiments show that, as the corona current increases, the radial current profile at the anode shrinks and the glow diameter near the anode increases. The radial profiles of the current and the corona glow during the transition to a glow discharge are measured. The longitudinal structure of the corona is computed using a 1.5-dimensional model that, unlike the other available models, includes gas ionization in the drift region of the corona. The experimental data are used to determine the effective cross section of the current channel at the anode. The radial glow profile near the anode is calculated using the measured current profile and assuming that the field profile is parabolic.

Low voltage-high current discharge of Ti vapour in high vacuum

A new type of discharge for ion plating has been investigated. A titanium vapour discharge is ignited on the electron beam evaporation source by applying a 22 V d.c. voltage to the anode which is located near the source. A dome-shaped plasma core is formed on the source and a strong blue light is emitted from the core. Changes in anode current (discharge current) ranging from ~ 2 A to over 100 A can be controlled by changing the anode voltage, electron beam gun power and electron-beam-scanning condition. Since the anode current immediately follows these changes, it is easy to control the discharge at will. Also, the ion collector current and ionization efficiency of titanium increase to ~ 20 A and over 100% respectively in keeping with the increase in anode current. This discharge is thus considered suitable for ion plating. This low voltage-high current discharge is closer to a vacuum arc discharge than to a glow discharge and this distributed discharge with no oscillation of the anode voltage and current is similar to the hot cathode arc but not the cold cathode arc. However, being a non-self-sustained discharge, it is not classified as a typical arc discharge.

Discharge mechanism of the Kyoto University-type microwave plasma cathode or microwave ion source

In this paper the discharge mechanism of the Kyoto University-type microwave plasma cathode is studied. The relationship between the electron-absorbed power pe and electron impact frequency γc is obtained. When B=875 G, pe decreases with the increment of γc. At the same time when γc→0 or γc≪ω, electron cyclotron resonance (ECR) discharge will be set up. When B≳875 G and γc =107–108 s−1, the off-resonance discharge exists. With γc increased up to a certain limit, it follows that when ωz‖γ=ω=(2×3−1/2)1/2ω, a new type of discharge, the so-called double resonance (DR) discharge, occurs. For the Kyoto University-type MPC or MIS, the off-resonance discharge and DR discharge can be satisfied and it is verified by experiment.

Photographic investigations of electric discharges in Sandy media

A complementary work to the accompanying paper of discharges properties in sand is presented here by means of photographing techniques. Photographic records of electric discharges in sand of three types are displayed. A few pictures were recorded under DC voltages. Most of the investigation was for lightning impulses. Streamer paths were recorded for very dry sand (large resistivities) and wet sand (low resistivities). Under DC voltages photographic cameras were mainly used. When applying lightning impulses the recording was made by placing X-ray sensitive films along the paths of the discharges. The observed features of the streamers are briefly described. A rare and new type of discharge has been observed. Positive streamers initiated at a certain radial distance (low field region) from the conductor and propagated towards the central conductor (high field region). This mechanism took place only for larger sand particles and application of negative lightning impulses under high resistivities of sand. Clear differences between the streamers were found, specially for high resistivitis. The discharging shapes were mainly dependent on the particle size and the impulse polarity.

Cu and Zn films produced with an anodic vacuum arc

A steady vacuum arc discharge with a consumable anode, the anodic vacuum arc, was used to produce thin Cu and Zn films. This new type of discharge is ignited in vacuum (⩽ 10 −2 Pa) and is sustained by metal vapor produced at the anode. In contrast to the well-known vacuum arcs with consumable cathodes no micro-particles are ejected from the evaporating anode. Deposition rates range from 23 to 65 nm s −1. The thin metallic films are homogeneous and show bulk density. The purity of the deposited metallic films is up to 99.9% and the electric conductivity is close that of the respective bulk material.

Possible High Power Laser Construction Using a New Discharge Type‐Heated Cathode Discharge in the Copper Vapours Continuously Evaporated from the Anode

AbstractThe possibility to build a high power copper laser using a new type of discharge – heated cathode discharge in the copper vapours continuously evaporated from a melted spot on the anode surface is analysed.From the experimental data on this new discharge type, the equivalent pressure of the copper atoms in the discharge space has been obtained. This pressure can be as high as 1 torr. The density of the power in the discharge volume is evaluated to be more than 1 kW/cm3.

Some characteristics of the hollow anode glow

A new type of discharge realized in a diode consisting of a cathode and a special type of hollow anode is presented. The distinctive arrangement of dark and luminous regions between the cathode and anode with a characteristic hollow anode glow has been observed in the discharge. The optical spectrum strongly depends on the discharge current, and can be practically a spark or arc spectrum without any lines of anode or cathode material.

Optical characteristics of the hollow anode discharge

A new type of discharge realized in a diode consisting of a concave cathode and a special type of a hollow anode is presented. The concave cathode focuses electrons toward the hollow anode increasing the density of high-energy electrons and the efficiency of excitation and ionization in the hollow anode. The distinctive arrangement of dark and luminous regions between the cathode and anode has been observed in the discharge.

Electrical and Spectral Characteristics of a Heated Cathode Discharge in Metal Vapors

AbstractA new type of discharge in pure metal vapors like copper or titanium is described. A stable discharge is produced between a heated cathode and the anode which has a melted spot on its surface due to the electron bombardment. The spectral characteristics prove that the discharge take place in the vapors of the anode material continuously evaporated from the melted spot on the anode. The discharge has a similar behaviour as the low voltage arc.

Cylindrical hollow-anode discharge

Hollow-anode discharge represents a new type of discharge which is realized in a diode consisting of a cylindrical cathode and special type of hollow anode whose inner surface only is conductive. The cylindrical cathode focuses electrons toward the hollow anode placed in the center of curvature, increasing the density of high-energy electrons and efficiency of excitation and ionization in the hollow aperture of the anode. Optical spectrum consists of intense ion lines of the operating gas without anode or cathode material lines.

Spectroscopy of hollow anode discharge

Hollow anode discharge represents a new type of discharge which is realized in a diode consisting of a concave cathode and a special type of hollow anode whose inner surface only is conductive. The concave cathode focuses electrons toward the hollow anode, increasing the density of high energy electrons and the efficiency of excitation and ionization in the hollow anode. The optical spectrum, which consists of ion lines only, indicates that in the hollow anode a highly ionized plasma is obtained. The spectrum does not consist of cathode (or anode) material lines.

Electrode surface process in gaseous plasma

The effect of dense oxygen plasma on the electrode surface was studied by means of an electron microscope. Copper and aluminum films of several hundred ångströms thick obtained by evaporation under vacuum were used as anode in the Self Sustaining Dipole Discharge (S.S.D.D.). The interesting feature of this new type of discharge is to provide a local intense electric field at the electrode surface which enhances the outward migration of metal ions and, therefore, produces a strong surface corrosion. This phenomenon is similar to the anodic oxidation in the electrolytic cell. The only difference would be that in electrolysis a liquid plasma is created at low applied voltage and high electric current, while in the S.S.D.D. a gaseous plasma is produced at relatively low discharge current and high applied voltage. The electrical breakdown over the newly formed oxide layer is, therefore, dominant in the latter case while the thermal breakdown seems to be more important in the electrolysis case. The thick oxide film formed in the present experiment was torn into fissures by both electrical and thermal breakdowns over the entire surface. At some places matter was even completely evaporated, leaving holes on the metal film. Diffraction patterns of selected areas revealed the existence of δAl 2O 3 with aluminum film and Cu 2O and CuO with copper film. Nucleation and growth of oxide is expected in the depth of the metal as a result of oxygen ion bombardment from the plasma.

The modification of cerebral electrical activity by intracarotid and topically applied diodrast

The effects of intra-carotid injection and topical application of Diodrast on the electrical activity of the brain in humans, cats and monkeys are described. These effects are complex and have been classified as: 1. 1. Augmentation of activity when an increase of previously present discharges or an altogether new type of discharge occurs. 2. 2. Decreased activity when diminution of previously present discharges occurs. 3. 3. If abnormal discharges such as spikes or slow waves are present in the resting record the drug may have a profound effect on them in either an augmenting or a decreasing sense. Slow activity is most often increased whereas the effect on a spike discharge may be augmenting or decreasing, depending on many variables. 4. 4. The most commonly encountered effect would seem to be irritative or convulsive in nature as instanced by the precipitation of electrical seizure discharges in cortical epileptic foci and the prolongation of high-frequency bursts in single-unit responses evoked by peripheral stimulation. The augmentation of evoked responses as recorded on the pial surface over (in) primary sensory receiving areas followed by the subsequent appearance of responses in association areas could well be due to a similar irritative effect, as could also the desynchronization effect when rhythmic burst activity is abolished. 5. 5. It would seem likely that the augmentation of delta foci in the neighborhood of destructive lesions and some instances of flattening of rhythmic burst activity is due to a depression or disruption of neuronal activity which has little in common with the irritative effects.

New Terms in the Spectra of N III, N IV, N V, O III, O IV, and O V

Certain spectrum plates from a new type of discharge have been analyzed. The source was a condensed discharge through air at a pressure of a few microns to a few hundred microns taking place in a quartz tube of about 2 mm bore and 9 cm long. From fifty to five hundred discharges of a large high-tension condenser sufficed for good exposures between $\ensuremath{\lambda}105$ and 796A, and showed known lines of carbon, nitrogen, oxygen and silicon. New lines have been identified, which establish new levels in N V, O IV and O V, and which join for the first time isolated groups of known levels in N III, N IV and O III.

New Type of Discharge in Neon Tubes

THE new type of discharge described in NATURE of May 19, p. 794, is evidently the same as that which I have produced when using a neon lamp as a safety device (Proc. Leeds Phil. Soc., 1, 185; Nov. 1927). The method, although different, is similar in principle.

New Type of Discharge in Neon Tubes

IT was found some years ago by one of us (J. W. R.) that if a condenser of the order of a microfarad capacity was discharged through a tube containing neon at a pressure of about 10 mm. with an adjustable resistance in series, then when the resistance was reduced below a certain value there was a marked change in the character of the discharge, distinguishing clearly the new type of discharge from others obtainable in such tubes.