RU2722228C1 - High-frequency pulses generator based on hollow cathode discharge - Google Patents

Abstract

FIELD: physics.SUBSTANCE: invention relates to high-frequency equipment. Generator of high-frequency pulses based on discharge with hollow cathode includes gas-discharge chamber, in which two gas-discharge gaps are provided, each gap is formed by hollow cathode and anode, at that corresponding geometrical parameters of both gas-discharge gaps are equal. Electrodes of both gas-discharge gaps are connected to power supply unit and load unit, power supply unit provides synchronous supply of high-voltage pulses to electrodes of both gas-discharge gaps, wherein in the generator there is a mode of mutual phase adjustment of high-frequency voltage pulses, simultaneously formed on both gas-discharge gaps. Inner surfaces of cavities of hollow cathodes related to different gas-discharge gaps are approximated to each other, which provides arrangement of mode of mutual phase adjustment by direct mutual electromagnetic influence of cathode layers of discharges initiated simultaneously in both gas-discharge gaps. In a particular embodiment, the generator is characterized by that both hollow cathodes are made in the form of hollow cylinders with open ends, at each cathode one of the ends faces the corresponding anode, and the second end face towards the other hollow cathode, wherein proximity of inner surfaces of cavities of hollow cathodes is provided by the fact that facing each other hollow cathode ends are maximally approximated.EFFECT: technical result is increase in efficiency of phase adjustment of HF pulses of generator of high-frequency pulses simultaneously generated on gas-discharge gaps on the basis of discharge with hollow cathode.1 cl, 1 dwg

Description

The invention relates to the field of high-frequency technology and can be used to create generators of high-frequency (HF) radiation.

A discharge with a hollow cathode [Moskalev BI, A discharge with a hollow cathode, M .: Energia, 1969] has the following peculiarity: under certain conditions (under certain geometric parameters of the cathode cavity, with discharge gas pressures lying in a certain range, and when a certain threshold of the discharge current density is exceeded) during its development, RF modulation of the discharge voltage occurs [Arbel D., Bar-Lev Z., Felsteiner J., Rosenberg A., Slutsker Ya. Z. "Collisionless Instability of the Cathode Sheath in a Hollow-Cathode Discharge", Physical Review Letters. 1993. V. 71. No. 18. P. 2919], while the amplitude of the RF modulations of the discharge voltage can reach 100% of the value of the discharge voltage.

Known RF generators based on a hollow cathode discharge, similar to this generator [Bulychev SV, Vyalykh DV, Dubinov A.E. et al. "Results of studies of high-frequency RF pulses generators based on a hollow cathode discharge" , Plasma Physics. 2009, t. 35, No. 11, p. 1019]. A generator of this type contains a gas discharge chamber formed by a hollow cathode and an anode isolated from it, the electrodes of the chamber are connected to a power source, and an electrical load is connected in parallel with the gas discharge circuit. In the chamber, the pressure level of the working gas is required for igniting the discharge and implementing RF modulations of the discharge voltage. When a voltage pulse is applied to the electrodes in the gas-discharge gap formed by the cathode and the anode, a gas discharge with a hollow cathode is initiated. The RF component of the fluctuations in the discharge voltage is the cause of the RF oscillations of the voltage at the electric load, which, in turn, are the source of electromagnetic RF energy.

The disadvantages of RF generators of this type include the limited power of the generated RF pulses. The limitation is due to the fact that RF modulations of the discharge voltage occur only at a relatively low power of high-voltage power pulses supplied to the electrodes of the gas discharge chamber and initiating a hollow cathode discharge in the gas discharge chamber, and the discharge initiated in this case has a diffuse shape. An increase in the power of high-voltage pulses leads to ignition in a gas-discharge chamber of a contracted shape, in which RF modulation of the discharge voltage is impossible [Bulychev SV, Vyalykh DV, Dubinov A.E. et al., “Results of studies of high-frequency RF pulse generators based on a hollow cathode discharge”, Plasma Physics. 2009, t. 35, No. 11, p. 1019].

It is possible to increase the power of RF generation by implementing a device in which the output RF pulse is the result of adding the RF pulses generated simultaneously by two or more gas discharge chambers or gaps. However, this path has its own difficulties - for the effective addition of harmonic signals it is required that the phases of these signals are the same. And for signals generated by RF generators based on a hollow cathode discharge, the initial phase is a random variable, therefore, the probability of equality of phases of the RF signals simultaneously generated by gas-discharge chambers or gaps that are part of the RF generator is practically zero. For the effective operation of an RF device based on a hollow cathode discharge, which includes more than one gas discharge chamber or more than one gas discharge gap, it is necessary to implement a phase adjustment mode for RF pulses generated simultaneously at different gas discharge gaps or chambers.

A RF generator based on a hollow cathode discharge is known [RF Patent 2657240, priority January 24, 2017], in which the phase adjustment mode of the RF signals generated simultaneously in different gas discharge chambers is implemented by implementing electromagnetic coupling between resistance transformers connected to chambers matching internal impedances of gas discharge chambers with impedance of the load unit. However, this type of phase adjustment is associated with distortion and a decrease in the amplitude of the generated signals due to the segments of the long impedance mismatch lines arising at the connection points, and its efficiency may be insufficient.

Known RF generator based on a discharge with a hollow cathode [RF Patent 2462783, priority 04/21/2011], which is a prototype of the inventive device containing a gas discharge chamber in which two or more gas discharge gaps are provided, each gap is formed by a hollow cathode and anode, corresponding geometric parameters all discharge gaps are equal. The electrodes of the discharge gaps are connected to the power supply and the load unit. The power supply provides a synchronous supply of high voltage pulses to gas discharge gaps. In the generator, a phase adjustment mode for high-frequency voltage pulses generated at different gas-discharge gaps is organized. In the chamber, the pressure level of the working gas is required for igniting the discharge and implementing RF modulations of the discharge voltage. When all the discharge gaps of the voltage pulses are synchronously supplied to the electrodes from the power supply in the discharge gaps, gas discharges with a hollow cathode are simultaneously triggered, in which RF modulations of the discharge voltage occur, and thus RF voltage pulses transmitted to the load block are formed on the gas discharge gaps. Due to the equality of the corresponding geometric parameters of the gas-discharge gaps, the frequencies of the RF modulations at all the gaps are also equal [Bulychev SV, Vyalykh DV, Dubinov A.E. et al., “Results of studies of high-frequency RF pulse generators based on a hollow cathode discharge”, Plasma Physics. 2009, t. 35, No. 11, p. 1019]. Initially, the phases of the RF pulses generated at the gas-discharge gaps can be different, but some time after the initiation of the discharges, they are aligned by means of a phase adjustment mode organized in the device. As a result, RF pulses with the same frequency and phase are simultaneously delivered to the load block from all gas-discharge gaps. Thus, the resulting RF pulse is formed in the load block, the amplitude of which is significantly higher than the amplitude of the RF pulse generated in a single gas-discharge gap.

In the prototype device, the regime of mutual phase adjustment of high-frequency voltage pulses simultaneously generated on gas-discharge gaps is organized by connecting gas-discharge gaps with vacuum channels, which enable the transportation of plasma formations that are elements of a gas discharge and perform high-frequency oscillations under the influence of discharge voltage modulations. In a particular embodiment, the gas discharge spaces are adjacent. Perturbations of electromagnetic fields in gas-discharge gaps caused by high-frequency oscillations of plasma formations propagating through vacuum channels from neighboring gaps are superimposed on “intrinsic” field oscillations in the gaps. As a result of the mutual influence of oscillations on each other in different gas-discharge gaps, the phases of the oscillations in all gaps are aligned.

However, the mutual phase adjustment mode used in the prototype device cannot be considered as efficient as possible. The electromagnetic coupling between the gas-discharge gaps, which is organized under a similar phase adjustment mode, may not be strong enough, and the phase adjustment process between RF signals can take too long, almost equal to the duration of the RF pulse. This phase adjustment mode involves the impact on each other of processes that cause high-frequency modulation of the discharge voltage in different gas-discharge gaps, through plasma formations. The phase adjustment mode, in which the direct mutual influence of modulating processes would be realized, seems more effective.

The disadvantage of the prototype device should be considered the lack of efficiency organized in the generator phase adjustment mode of high-frequency voltage pulses generated at different gas-discharge gaps.

The technical problem is the creation of a high-frequency pulse generator based on a hollow-cathode discharge, in which a gas-discharge chamber with two gas-discharge gaps is used, and the generator implements an effective phase adjustment mode for RF pulses simultaneously generated at gas-discharge gaps.

The technical result is to increase the efficiency of the phase adjustment mode of the RF pulses simultaneously generated on the gas discharge gaps of the gas discharge chamber of the high-frequency pulse generator based on the hollow cathode discharge.

This technical result is achievable due to the fact that, compared with a high-frequency pulse generator based on a hollow cathode discharge containing a gas discharge chamber, in which two gas discharge gaps are provided, each gap is formed by a hollow cathode and an anode, and the corresponding geometric parameters of both gas discharge gaps are equal, the electrodes of both gas-discharge gaps are connected to the power supply and the load unit, the power supply provides a synchronous supply of high voltage pulses to the electrodes of both gas-discharge gaps, while in the generator the regime of mutual phase adjustment of high-frequency voltage pulses simultaneously generated on both gas-discharge gaps is organized, in the proposed generator internal the surfaces of the cavities of the hollow cathodes, belonging to different gas-discharge gaps, are close to each other, which ensures the organization of the regime of mutual phase adjustment by direct mutual electromagnetic the influence of the near-cathode layers of the discharges, initiated simultaneously in both gas-discharge gaps.

In particular, both hollow cathodes are made in the form of hollow cylinders with open ends, at each cathode one of the ends faces the corresponding anode, and the second end faces the other hollow cathode, and the proximity of the inner surfaces of the hollow cathode cavities is ensured by facing each other to each other the ends of the hollow cathodes are as close as possible.

A glow discharge, a variant of which is a hollow cathode discharge realized in RF generators of the claimed type, is characterized by the presence of a relatively thin cathode layer near the working surface of the cathode with a large gradient of electric field and electric potential [Granovsky V.L. Electric current in a gas. - M .: "Science", 1971; Reiser Yu.P., Gas discharge physics. - Dolgoprudny: Intellect Publishing House, 2009]. According to the studies of the authors of the patented technical solution, the reason for the RF modulations of the discharge voltage arising in a gas discharge with a hollow cathode is a specific oscillatory instability that occurs in the near-cathode layer of the discharge [Bulychev SV, Vyalykh DV, Dubinov A.E. et al., “Results of studies of high-frequency RF pulse generators based on a hollow cathode discharge”, Plasma Physics. 2009, t. 35, No. 11, p. 1019].

Since the RF modulation of the discharge voltage in the discharge with the hollow cathode is caused by the instability of the cathode layer of the discharge, the effective phase adjustment of the RF signals generated simultaneously on both gas discharge gaps of the discharge chamber of the RF generator based on the discharge with the hollow cathode can be achieved by providing an effective electromagnetic interaction between the cathode layers of discharges initiated in these gaps.

High-frequency oscillations of the electric potential in the near-cathode layer cause a corresponding vibrational disturbance of the electromagnetic field in space near the region occupied by the near-cathode layer. The idea of a patented technical solution is that when two working surfaces of hollow cathodes are close to each other (i.e., surfaces of cathodes coated with a discharge), an effective mutual electromagnetic interaction of the cathode layers of two gas-discharge gaps will be realized. The degree of interaction efficiency is determined by the magnitudes of the acting fields, which are greater the closer to each other the cathode layers emitting these fields. As a result, in each of the cathode layers, their own high-frequency oscillations of the electric field and forcing oscillations of the electric field from the other layer will be superimposed on each other, and the frequencies of these oscillations are equal. As a result of the addition of these oscillations, uniform resonant oscillations will be established in each of the cathode layers, and the phases of the oscillations in both layers will be equal. Thus, a phase adjustment mode for high-frequency voltage pulses generated at various gas-discharge gaps will be organized.

When initiating a hollow cathode discharge, the cathode surface is the surface of the cathode cavity. Therefore, to organize an effective regime of phase adjustment of the surface of the cathode cavities of the hollow cathodes, it is necessary to place them in close proximity to each other.

The design of the prototype device (even in the particular embodiment when the gas-discharge gaps are adjacent) does not imply a mandatory close relative position of the surfaces of the cathode cavities of the hollow cathodes belonging to different gaps, i.e., a close relative position of the cathode layers. The design of the claimed device implies the obligatory close proximity to each other of the surfaces of the cathode cavities of the hollow cathodes belonging to different gaps - that is, it implies the close proximity to each other of the regions of two gas-discharge gaps in which processes leading to high-frequency voltage modulations occur. Due to the close location of the two near-cathode layers to each other, the connection between them, which is the organizing factor of the mutual phase adjustment of the RF pulses generated simultaneously at two gas-discharge gaps, is stronger than when using the prototype device. Therefore, when using the design of the gas discharge chamber, made in accordance with the claimed technical solution, the efficiency of the phase adjustment between the RF pulses generated at different gas discharge gaps will be higher than when using the prototype device.

In the particular case when the hollow cathodes are made in the form of hollow cylinders with open ends, at each cathode one of the ends faces the corresponding anode, and the second end faces the other hollow cathode, the proximity of the surfaces of the hollow cathodes covered by the discharge is ensured by the fact that the ends of the hollow cathodes are as close as possible to each other.

An example of the design of a hollow-cathode discharge RF generator is shown in FIG. The gas discharge chamber contains two gas discharge gaps, each gas discharge gap is formed by its corresponding hollow cathode 1 and anode 2 separated by insulator 3, the hollow cathodes 1 are made in the form of hollow cylinders with open ends, at each cathode one of the ends faces towards the corresponding anode, and the second the end face towards the other hollow cathode, and the proximity of the inner surfaces of the hollow cathode cavities is ensured by the fact that the geometric characteristics of both gas-discharge gaps (i.e., the dimensions of the cathode and anode cavities, the distances from the hollow cathodes to the anodes) are respectively equal. The surfaces of the cathode cavities of the hollow cathodes 1 (the working surfaces of the cathodes near which the discharge is ignited) are close to each other due to the fact that the ends of the hollow cathodes facing each other are as close as possible. The ends of the hollow cathodes are separated by a membrane 4, the presence of which prevents the development of a discharge between the electrodes of different gas-discharge gaps. A power supply unit and an electric load unit 6 are connected to the hollow cathode 1 and anode 2 of each gas-discharge gap. The power supply unit 5 includes two power sources, simultaneously triggered by a single control pulse, and provides the possibility of synchronously supplying voltage pulses to the hollow cathode and anode of each gas discharge gaps.

The RF generator operates as follows. In the gas discharge chamber, the working gas pressure level required to ignite the gas discharge between the electrodes of this configuration is maintained. When the power supply unit 5 is started, high voltage voltage pulses are simultaneously supplied to both gas discharge gaps. In each gap between the hollow cathode 1 and the anode 2, gas discharges with a hollow cathode are simultaneously initiated, the voltage of the discharges is modulated by the RF frequency. The HF oscillations of the discharge voltage from each discharge gap are transmitted to the electric load unit 5 (a radiation system or resistive resistance can be used as a load). Due to the mutual electromagnetic influence of the oscillations of the electric potential of the cathode layers 7, the phases of the oscillations mutually adjust and become equal.

The device in a specific implementation has the following parameters:

- hollow cathodes and anodes are made of stainless steel, insulators are made of vacuum ceramics or fluoroplastic;

- the length of each cathode cavity is 50 mm, the diameter is 25 mm;

- membrane thickness - 2 mm;

- gas-discharge gaps are filled with electronegative or inert gas at a pressure of the order of 10 ^-1 Torr .;

- the power source provides voltage pulses with an amplitude of 2 ÷ 5 kV at the output.

With this design of the RF generator, a direct mutual electromagnetic effect of the regions of gas-discharge gaps will occur, in which there are processes that cause high-frequency modulations of the gas-discharge voltage. Due to the proximity to each other of the near-cathode layers of the discharges formed simultaneously in both gas-discharge gaps, their mutual influence will be stronger and more effective than using the prototype device, therefore, the method of organizing the mutual phase adjustment of high-frequency voltage pulses simultaneously generated on both gas-discharge at intervals, will be more effective. Thus, the required technical result will be achieved when performing the device according to the proposed technical solution.

Claims (2)

1. A high-frequency pulse generator based on a hollow cathode discharge, comprising a gas discharge chamber in which two gas-discharge gaps are provided, each gap is formed by a hollow cathode and an anode, the corresponding geometrical parameters of both gas-discharge gaps being equal, the electrodes of both gas-discharge gaps being connected to the power supply and the block load, the power supply provides a synchronous supply of high voltage pulses to the electrodes of both gas discharge gaps, while the oscillator is equipped with a regime of mutual phase adjustment of high frequency voltage pulses simultaneously generated on both gas discharge gaps, characterized in that the internal surfaces of the hollow cathode cavities belonging to different gas discharge the gaps are close to each other, which ensures the organization of the mutual phase adjustment mode by direct mutual electromagnetic influence of the near-cathode layers of the discharges, initiated simultaneously in the wallpaper x gas discharge gaps. 2. The generator according to claim 1, characterized in that both hollow cathodes are made in the form of hollow cylinders with open ends, at each cathode one of the ends faces the corresponding anode, and the second end faces the other hollow cathode, and the proximity of the internal surfaces of the cavities hollow cathodes is ensured by the fact that the ends of the hollow cathodes facing each other are as close as possible.

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