cathode spot movements and chopping current of

2016 27th International Symposium on Discharges and Electrical Insulation

056-B2-P-04.pdf Experimental Investigation on the Current of Cathode Spot of Vacuum Arc in Axial Magnetic Fields 220-222 B. Z. Wu, Z. Q. Shi, C. Wang, S. L. Jia, L. J. Wang 057-B2-P-05.pdf Influence of Magnetic Fields on Inrush Current Prestrike

Methods for Estimation of the Vacuum Status in Vacuum Circuit

The behavior of the arc voltage (Kx) of a low current dc arc (10 A). The basic idea is that the low current arc generates only one cathode spot [13,14] and has to be re-ignited whenever a new cathode spot has to formed. This produces a sudden increase in

conferenceseries.iop materials science and engineering open access proceedings IOP Conferences Series: Materials Science and Engineering

2020/4/15The cathode spot is theoretically analyzed here for a 10A current and a silver contact in vacuum. The main equations leading to the values of physical characteristics are detailed and resolved according to the radius r in the domain 0.5-1.5m. The choice of this

The origin of current chopping in vacuum arcs

A semiempirical model is presented which relates the phenomenon of current chopping of vacuum arcs to rapid microscopic processes on the cathode surface. First, for a resistive circuit the approximate chopping current as a function of power-current amplitude was calculated using two DC arc lifetime parameters which were obtained experimentally. Secondly, it is shown that spontaneous arc

Split Process of Low‐Pressure Arc Cathode Spots on

2010/11/1A remarkable characteristic of a cathode spot of a low‐pressure arc is that the cathode spot moves around on the metal surface. A cathode spot can remove an oxide layer. Cathode spots of low‐pressure arcs have been used for cleaning metal oxide surfaces. However, the influence of an oxide layer on the cathode spot movement remains unclear. As described herein, the cathode spot movements

Final Report for NASA Contract NASA/NAG3

The laser beam cross section is 40 mm2. This is very suitable for the cathode spot observation, usually the cathode spot size of a refractory cathode is around 1-2 mm at a current range of 100 A to 400 A [3]. The laser wavelength is 337 nm. The pulse energy of

Simulation of cathode spot crater formation and

2018/4/11B. Juttner, " Erosion craters and arc cathode spots in vacuum," Contrib. Plasma Phys. 19(1), 25– 48 (1979). Google Scholar 4. V. F. Puchkarev and A. M. Murzakaev, " Current density and the cathode spot lifetime in a vacuum arc at threshold currents," J. Phys

What is Current Chopping?

2009/12/6As the arc current decrease toward current zero, the arc plasma again becomes diffuse, with the electron current being emitted from a declining numbers of discrete cathodes. As the current in the final cathode spot approaches the AC zero, the arc may become ustable and extinguish spotantly.

Final Report for NASA Contract NASA/NAG3

The laser beam cross section is 40 mm2. This is very suitable for the cathode spot observation, usually the cathode spot size of a refractory cathode is around 1-2 mm at a current range of 100 A to 400 A [3]. The laser wavelength is 337 nm. The pulse energy of

Methods for Estimation of the Vacuum Status in Vacuum Circuit

The behavior of the arc voltage (Kx) of a low current dc arc (10 A). The basic idea is that the low current arc generates only one cathode spot [13,14] and has to be re-ignited whenever a new cathode spot has to formed. This produces a sudden increase in

Investigations of the Current Density in the Cathode Spot

A short review is given on the problem of the current density in the cathode spot of a vacuum arc, theoretical models and experimental results are discussed. A new measuring method is presented which is directly related to the current carrying area of the spot. It

Electric Discharge in Vacuum

For low currents a highly mobile cathode spot is formed and for large currents a multiple number of cathode spots are formed. These spots constitute the main source of vapour in the arc. The processes involved in drawing the discharge will be due to high electric field between the contacts or resistive heating produced at the point of operation or a combination of the two.

Oscilloscope

An oscilloscope, previously called an oscillograph, and informally known as a scope or o-scope, CRO (for cathode-ray oscilloscope), or DSO (for the more modern digital storage oscilloscope), is a type of electronic test instrument that graphically displays varying signal voltages, usually as a calibrated two-dimensional plot of one or more signals as a function of time.

What is Current Chopping?

2009/12/6As the arc current decrease toward current zero, the arc plasma again becomes diffuse, with the electron current being emitted from a declining numbers of discrete cathodes. As the current in the final cathode spot approaches the AC zero, the arc may become ustable and extinguish spotantly.

An Analysis of the Instability Phenomena of a Low

In order to clarify the instability phenomena of a low current vacuum arc, characterized by noise on the current trace prior to the actual current chopping, an analysis of silver cathode spot has been made. For the analysis, cathode spot region is recognized as the collisionless space charge sheath connected with singly ionized collisional plasmas.It is proposed that a current level below that

Final Report for NASA Contract NASA/NAG3

The laser beam cross section is 40 mm2. This is very suitable for the cathode spot observation, usually the cathode spot size of a refractory cathode is around 1-2 mm at a current range of 100 A to 400 A [3]. The laser wavelength is 337 nm. The pulse energy of

Processes in the cathode region of a low

the cathode spot to the anode) are several centimeters. On the one hand, for low gas pressures and for pre-initiation of the cathode spot, such a system can be called a plasma- filled vacuum diode, since we assume that after ignition of the auxiliary discharge between electrodes 1 and 3, the vacuum gap

What is Current Chopping?

2009/12/6As the arc current decrease toward current zero, the arc plasma again becomes diffuse, with the electron current being emitted from a declining numbers of discrete cathodes. As the current in the final cathode spot approaches the AC zero, the arc may become ustable and extinguish spotantly.

INVESTIGATIONS OF CURRENT INSTABILITIES BEFORE CURRENT

influence the chopping-current, investigations with different contact-materials and test circuit parame-ters have been performed. In order to achieve a deeper understanding of the transient currents near the current zero, simula-tions have been performed. For this

Effect of magnetic field on the behavior and sustaining

2007/10/1Effects of magnetic field on duration and dynamics of low‐current DC vacuum arcs, less than 20 A, were examined. Without a magnetic field, the cathode spot moves at random on the cathode surface and the arc voltage is constant for increasing gap length up to 30 mm. In the axial magnetic field, the arc plasma was constricted and the arc voltage rose with increasing gap length. When a magnet

Vacuum tube

A vacuum tube, an electron tube, valve (British usage) or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.The type known as a thermionic tube or thermionic valve uses the phenomenon of thermionic emission of electrons from a hot cathode and is used for a number of fundamental

(PDF) Structure and time behavior of vacuum arc cathode

Structure and time behavior of vacuum arc cathode spots IEEE Transactions on Plasma Science, 2003 Sergey A. Barengolts G. Mesyats Sergey A. Barengolts G. Mesyats Download PDF Download Full PDF Package This paper A short summary of this paper

What is CRT (Cathode Ray Tube)?

2020/6/4CRT (Cathode Ray Tube) are glass vacuum tubes in which an electron gun radiates an electron current directed by an electric field towards In the cathode ray tube, an electronic ball produces and limits an electron beam that it sends towards a screen covered with

Hollow Cathode DUV Lasers

This technology is similar to hollow cathode lamps wherein a basic lifetime limit is related to sputter erosion of the hollow metal cathode. As metal from the inside diameter of the cathode is sputtered away, several ageing processes occur: physical change in the shape of the hollow cathode, trapping of buffer gas under the sputter deposits, and contamination of laser mirror surfaces.

What is Cathode Ray Tube (C R T) Diagram and Working

2018/5/20An indirectly heated cathode requires current and voltage value 600 mA at 6.3 V. In case of a highly efficient system the value is 300 mA at 6.3 V . The emitted electrons further pass through a small hole present in the control grid.

An Analysis of the Instability Mechanism of a Low

trace prior to the actual current chopping, the chopping and instability current for the major commercial switching cathode material such as pure silver and compound silver with palladium were performed in this study. A single cathode spot of

Electric Discharge in Vacuum

For low currents a highly mobile cathode spot is formed and for large currents a multiple number of cathode spots are formed. These spots constitute the main source of vapour in the arc. The processes involved in drawing the discharge will be due to high electric field between the contacts or resistive heating produced at the point of operation or a combination of the two.

Titanium and Titanium Alloys as Biomaterials

2013/5/22However if the cathode spot stays at one of these evaporative points for too long it can eject a large amount of macro-particles or droplets as seen above. These droplets are detrimental to the performance of the coating as they are poorly adhered and can extend through the coating.

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