Plasma electron source

 

The invention relates to the field of plasma technology and can be applied in the development of electron-beam devices and used in electron beam technology, experimental physics, plasma-chemical technology. Electron source for generating a continuous electron beam includes a hollow cathode, anode, accelerating electrode with a hole in the center for the formation of the electron beam, insulators placed on the flange, and the emission hole in the anode blocked by a fine metal mesh. Between the anode and accelerating electrode is placed a disc of heat-resistant inorganic insulator with a hole in its Central part. The diameter of the hole in the dielectric disk is larger than the diameter of the emission holes in the anode and smaller than the diameter of the hole in accelerating electrode. The technical result is the ability to increase the operating pressure while maintaining the electric strength of the accelerating gap. 1 Il.

The invention relates to the field of plasma technology and can be applied in the development of electron-beam devices and used in electron beam technology, experimental physics, plasma-chemical ones is these electrons from the gas discharge plasma.with. The USSR 1455928, 835264). In these devices, the plasma is generated by initiating a discharge in the gas. Discharge, i.e., the current in Gaza, supported by the voltage applied between the electrodes of the discharge system. Plasma emission boundary is generated within the hole, performed in one of the electrodes of the discharge system. In the electron source with a plasma cathode.with. The USSR 1455928), comprising a hollow cathode, a cylindrical anode, a flat cathode-reflector located opposite the hollow cathode, the emission hole is arranged in the center of the flat cathode-reflector. The discharge is ignited in the gas jet in the cathode cavity. Accelerating voltage is applied between the cathode-reflector and the accelerating electrode. Specified electron gun allows you to receive the electron beam with an energy of 20-40 Kev when the gas pressure in the accelerating gap of 1.310-3PA-1,310-2PA. With increasing pressure cannon loses efficiency because accelerating gap ignites the discharge, which leads to a sharp drop in voltage up to several hundred or even tens of volts. Increasing the operating pressure can be achieved by placing near the emission electrode to zazelenchuk eliminates the long path, which usually develops discharge. The use of the screen allows you to increase the operating pressure to 2.6 PA. A further increase in pressure, however, causes a discharge in the accelerating gap, and despite the fact that, in accordance with the Paschen curve, the discharge should not occur. The reason lies primarily in the fact that the electron beam causes in accelerating gap ions, which are accelerating to get on the emission electrode, causing secondary electron emission, which ultimately leads to the emergence of discharge and loss of efficiency of the source.

The closest in technical essence of the present invention is an electron source of continuous action (PTE, 1998, 2, 95-98 C.) containing coaxial hollow cathode, the anode and the emission hole, covered with fine mesh, and the accelerating electrode with an aperture for passing the electron beam. In the specified source electrodes of the accelerating gap, i.e. the anode and accelerating electrode is planar and parallel to each other at extremely close range, the minimum value of which is determined by the ability of the vacuum breakdown. This decision allows to increase the late accelerating voltages up to 8 kV. It is clear that this technical solution has no fundamental differences from the solutions described in (ZH, 1980, T. 50, Vol.1, S. 203-205). Increasing the operating pressure is achieved by reducing the current density of the electron beam, which, in turn, is caused by the increase in the diameter of the emission opening.

The technical result of the present invention is to further increase the operating pressure of the source of electrons while maintaining the electric strength of the accelerating gap and density of the emission current.

This result is achieved in that in the known electron source containing coaxial hollow cathode, the anode and the emission hole is overlapped with the emission grid and an accelerating electrode between the anode and accelerating electrode is placed a disc of heat-resistant inorganic insulator with a hole in the center. Moreover, the diameter of the hole in the disk is larger than the diameter of the emission holes in the anode and fewer holes in accelerating electrode.

The proposed scheme of the electron source shown in the drawing. The hollow cathode 1, anode 2 and the accelerating electrode 3 is placed coaxially on ceramic insulators 4, one of which is mounted on the flange 5. Emission opening 6 in the anode blocked the IC 7 with an opening 8, placed between the anode and the extractor.

The source operates as follows. The vacuum chamber, the flange is installed on the source, pumped to a pressure of 1.3 to 13 PA. If necessary, the specified pressure range is achieved by a gas inlet in the vacuum chamber. Then to the cathode 1 and the anode 2 source applied voltage from the power supply discharge, a gradual increase which achieve ignition of the discharge. After that submit the voltage between the anode 2 and the accelerating electrode 3 from block accelerating voltage, a gradual increase sought by the formation of electron beam energy. Placing ceramic disc 7 allows you to increase the operating pressure to 13.3 PA at an accelerating voltage of 10 kV, the current issue of up to 1 a and the diameter of the emission holes in the anode 10 mm disc allows you to avoid emitted electron accelerating electrode. This explains why the hole in the disk must be smaller than the holes in the accelerating electrode. On the other hand, the hole in the disk must be greater than the emission holes in the anode, for during the reverse ratio cannot avoid the intense heating of the edge of the disc by the electron beam, which inevitably entails the giving mechanical strength of the disk and the appearance of cracks. All these events ultimately lead to the reduction of the electric strength of the accelerating period and the occurrence of discharge in it. The possibility of heating the edges of the dielectric disk explains why it is necessary that the disk was made of heat-resistant inorganic dielectric (ceramic, quartz).

This electron source allows to obtain an electron beam at pressures up to 13.3 PA at an accelerating voltage and the density of the emission current is not smaller than the closest analogue that increases the possible applications of electron beams. In particular, the proposed source can be used in chemical plants to initiate beam discharge in the gas.

Claims

Plasma electron source of continuous action, including coaxial hollow cathode, the anode and the emission hole, covered by a fine-grained grid, an accelerating electrode, characterized in that between the anode and accelerating electrode placed the disk, made of heat-resistant inorganic insulator with a hole in the center, and the hole in the disk is larger than the emission holes in the anode and fewer holes in accelerating e is

 

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1 cl, 1 dwg

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