RU2274923C2 - Method for producing beams of fast electrons, ions, atoms, as well as ultraviolet and roentgen rays, ozone, and/or other chemically active molecules in dense gases - Google Patents

Abstract

FIELD: semiconductor engineering.

SUBSTANCE: new gaseous-discharge conditions are proposed, as follow: E_n/N = U/Δ·N, where E_n is characteristic value of electric field intensity in near-electrode area of gas with slow electrons; N is concentration of gas mixture neutral particles in electric field area under discussion; U is potential of high-voltage electrode relative to ground or to other nearest electrode; Δ is size along direction of intermediate electric field of high-voltage potential space-time localizing area. Runaway electrons whose energy amounts to hundreds of keV and currents, to hundreds of kA in corona and space discharges, as well as discharges over dielectric surface and their combination are more efficiently generated under such conditions. Fast electrons can be generated in single-electrode corona discharge and fast electron beams are efficiently generated in dense-gas space discharges combined with surface discharge or discharges in dielectric tubes; power density of X-ray, ultraviolet, and violet radiation from discharge is effectively controlled, ozone and/or other chemically active or excited molecules in dense gases can be obtained in discharge with runaway electrons.

EFFECT: enlarged functional capabilities, enhanced amplitude of beam current both in electrode-to-electrode gap and in past-anode space.

16 cl, 15 dwg

Description

The invention relates to the field of generation of charged particle beams with energies up to hundreds of keV with concomitant short-wave radiation and can be used for radiation processing and sterilization of objects, excitation of active media and chemical reactions, for spectroscopic and diagnostic measurements, etc. in quantum electronics, plasma chemistry, medical, food and other industries, for pre-sale preparation or preparation for long-term storage of food, as well as for the decontamination of microorganisms in everyday life, in medical institutions, in consumer services, in military units and in emergency situations .

Known methods for producing electron beams accelerated to energies from units to hundreds of keV in volume nanosecond gas discharges with a pressure of 10 Pa to atmospheric [1-35]. In all cases, the generation of fast (runaway) electrons (with energies above the maximum ionization loss in a given gas — usually above 150 eV) occurs in a gas-filled gap between electrodes located at a distance d from each other in the high-voltage mode (discharge voltage U in the gap usually 5 ÷ 12 times the static breakdown voltage Us). Moreover, in the gap there is one region of a strong field where the condition for runaway electrons is fulfilled, that is, where the reduced electric field strength exceeds a certain threshold threshold value (E / N) _cr (constant for each gas) (see [1]). At sufficiently low gas pressures (usually up to hundreds of Pa), such a region is a rather short interelectrode gap in which the acceleration of electrons can occur even when the pulse duration of the applied voltage is tens, hundreds of ns or more. This is due to the fact that the discharge mode is determined by a set of electronic avalanches that do not reach a critical size in a short interelectrode gap and the discharge does not go into the channel (streamer) stage even with long pulses of applied voltage. With a further increase in gas pressure, the average electric field in the interelectrode gap becomes sharply inhomogeneous and has the greatest value near the cathode, where the field strength can exceed the critical value for runaway electrons and where then the transition of low-energy electrons from the discharge plasma to the runaway mode occurs. In volume discharges and discharges in long shielded tubes [18], an increase in gas pressure leads to a sharp decrease in the current of the fast-electron beam, and with a further increase in voltage, the discharge passes to the stage of a conventional streamer (spark) without generating a significant amount of runaway electrons and X-ray radiation. Using nanosecond voltage pulses with an amplitude of up to hundreds of kV, a number of authors managed to obtain runaway electron beams in dense gases [5, 7, 19, 26-29] from single cathodes of small area and with significantly lower currents (up to 400 A) than at low pressures.

The disadvantages of the known methods for producing runaway electron beams are:

1. Low efficiency (the ratio of the energy of fast electrons in a pulse to the total energy of a discharge pulse) for generating a beam of fast electrons in such a discharge that manifests itself either in a low average electron energy in the beam compared to the applied voltage (5 ÷ 8 keV at applied 140 kV) or in a low beam current of fast electrons relative to the discharge current (1 ÷ 100 A versus 1 ÷ 10 kA).

2. The operating modes of discharges with voltages of hundreds of kV that are used practically do not allow controlling the main parameters of the fast electron beam, since attempts to increase the voltage or increase the duration of the voltage pulse (or use standard relatively cheap high-voltage pulse generators with a front of 3-10 ns to generate the beam) to the transition of the discharge into spark form without generating a significant amount of fast electrons in the beam.

This is due to the laws of the development of discharges in strongly overstressed spaces. Meanwhile, many applications require setting the energy or current of electrons in the beam, changing them without completely changing the system parameters, setting different shapes and sizes of the discharge region, as well as setting and changing the type and pressure of the gas mixture in which the generation of the electron (ionic, atomic ) beam.

3. It is not possible to obtain the generation of electrons of subrelativistic energies in single-electrode high-voltage discharges (such as a unipolar corona), the use of which in a number of applications is preferable to the use of two- or multi-electrode systems.

4. Using the well-known operating modes of nanosecond discharges in dense gases to generate X-ray radiation with quantum energies of 50–150 keV (used in medicine, flaw detection, and X-ray cargo control), pulses with an energy of nJ were obtained [4], which is many orders of magnitude lower obtained in vacuum x-ray tubes. To date, a sufficiently general description of the discharge regime has not been formulated, which would determine the necessary relations between the parameters of the power source, the electrode system, and the gas mixture, which ensure the generation of runaway electrons in dense gases in volume and surface discharges at various gas pressures and various applied voltages.

Closest to the claimed method is the method [25, 26], in which a beam of electrons of subrelativistic energies is generated in air and other gases with a pressure up to atmospheric in a system of electrodes, a metal convex hemispherical cathode with a grid on its surface - a grid anode (optimal distance between electrodes d = (1 ÷ 1.5) cm) when the gap is overstressed by at least 10 ÷ 12 times and two dacron barriers are used, one of which is located close to the anode and the other at a distance of 0.2d from the cathode.

The disadvantages of the prototype method are as follows.

1. In the method according to the prototype, to obtain a beam of fast electrons in dense gases, the optimal overvoltages are not lower than 10 (even higher recommended), therefore, for gaps of a few cm, power supply voltages of 500 ÷ 1000 kV with a front of 3 ÷ 5 ns are required, which it seems technically quite a difficult task, especially for a pulse-periodic mode of operation of a discharge with a frequency of more than 100 Hz (the most optimal for a wide range of applications), and such power sources are not commercially available.

2. The use of a power source with a voltage rise rate of more than 10 ¹⁴ V / s and the parameters of the electrodes recommended by the prototype method leads to the generation of runaway electrons in dense gases only at the very initial stage of the discharge, which then passes to the channel stage (in which there is no generation electron beam), so that the runaway electron generation efficiency does not exceed a few percent.

3. The position of the dielectric barrier relative to the cathode at a distance of 0.2d has nothing to do with the parameters of the power source, the composition and pressure of the gas, which, when these parameters are changed, often leads to breakdown of the dielectric barrier by a spark discharge following the stage of runaway electron generation in gases with a pressure of the order of atmospheric .

The technical result to which this invention is directed is the generation of fast electrons in a single-electrode corona discharge, an increase in the efficiency of generation of a beam of fast electrons in dense gases in volume discharges combined with a surface discharge or discharge in dielectric tubes (channels), and an increase in the beam current amplitude both in the interelectrode gap and in the anode space, increasing and controlling the power density of X-ray, UV, and violet radiation from the discharge and as well as ozone and / or other reactive or excited molecules in dense gases in the discharge electrons from escaping.

The indicated technical result is achieved in that, in comparison with the known method for producing a fast electron beam in a dense gas, which consists in supplying a voltage 10 or more times higher than the static breakdown voltage with a rather steep rise front, to the interelectrode gap of the cathode – anode, in contrast from the known method in the proposed method, the slew rate of the pulse of the high voltage potential V _U = (d / U ₀ ) · (dU / dt) ≈2U / τ _U supplied to the high voltage electrode is chosen so that the condition

or, which is essentially the same

meaning that near the high-voltage electrode (in a region of size Δ ~ τ _U · V _n ) in a time of the order of τ _U a primary zone of runaway electron generation will have time to form, from which the latter escape to the outer zone with a lower electric potential, even if any other There are no electrodes near the high voltage electrode.

Here τ _U is the pulse duration of the high voltage potential U, which is either known and then it is necessary to determine the maximum value E = U / d, or E is known and then it is necessary to determine τ _U at which runaway electrons will be generated in the discharge, etc .;

τ _d is the time of development of the streamer discharge under given conditions, τ _d = d / V _n ,

U ₀ is the amplitude of the pulse of the high voltage potential;

V _n is the velocity of the front of the gas ionization wave by slow (plasma) electrons, calculated according to the equations of the theory of streamer breakdown of gas;

E _cr is the electric field strength at which the electrons in a given gas can acquire energy sufficient to “run away” —a constant from the literature for each gas;

E is the average electric field strength on the scale of a potential change of order d;

d is the characteristic size of the interelectrode gap or the characteristic radius of curvature of the field near a single high-voltage electrode.

Thus, we described the condition for the existence of a discharge with runaway electrons in dense gases with a pressure up to atmospheric and higher, which is new and significant. The essence of this phenomenon is that for the generation of electrons in a gas (not only in a corona discharge, but also in a volume discharge, and in a discharge moving across the surface), it is important not so much the amplitude of the pulse supplied to the high-voltage electrode as the degree of excess of its rise rate V _U (which determines the increase in the electron concentration in the near-electrode region Δ) with respect to the velocity of the ionization front V _n (which determines the decrease in the concentration of charged particles due to the "spreading" of this region), as well as the pulse U, since the average field in the gap must have time to decrease before the cathode streamer has time to develop and the discharge passes into the channel stage. It turns out that if a high voltage potential U with a sufficiently high slew rate V _{U is} applied to the electrode (s), which ensures the autowave nature of the ionization wavefront movement by fast electrons along the outer zone (single-electrode discharge) or along the interelectrode gap (multi-electrode discharge), then at a sufficiently low value of E (a sufficiently large d, which determines a sufficiently small value of V _n ~ E (in a longitudinal field) and a sufficiently large value of τ _d ~ d / V _n ) for a time τ _U ≈d / V _U (less than τ _d ) in some prielek native region (runaway electron generation region) having a size Δ (in the direction of the average electric field) of the order of the size of the ionization zone (for a corona discharge) and significantly shorter than the length of the interelectrode gap d (for volumetric and moving discharges on the dielectric surface, as well as for discharges in shielded and unshielded dielectric tube or in a discharge, which is a combination of the above), spatially-temporal front localization is carried out near one or more electrodes gas ionization waves.

The double layer of charged particles of this front provides

firstly, acceleration (in the direction of the cathode or dielectric along which the discharge propagates) of ions and fast atoms (obtained mainly by resonant charge exchange of ions in dense gases) with the formation of a beam of fast ions and atoms in the ionization zone near the cathode or dielectric ( knocking out enough of them to start the discharge, the number of electrons) and penetrating it into the region behind the cathode or behind the dielectric if the cathode or dielectric has holes.

Secondly, an ionization zone (size Δ) formed near the cathode can accelerate in the form of an autowave along the surface of the dielectric to its boundary with the anode or with the gas volume in which the anode is located. In the latter case, the discharge, which began as sliding on the surface of the dielectric or as a discharge in the dielectric tube, continues to the anode in the form of a volume discharge or corona bipolar discharge with runaway electrons, the current density and energy of which in such a discharge can be increased compared to a volume discharge without dielectric surfaces.

Thirdly, in a region of size Δ for a time of the order of τ _U , the electric field increases above the critical value for runaway electrons, after which an ionization wave (and, under certain conditions, a “counter” ionization wave from another electrode passes through the main discharge volume, compensating the spatial positive charge formed by the first wave), accelerating and / or avalanche propagating the runaway electrons and the electrons of the ionization cascade in an average field distorted by the space charge of positive ions, and a beam (s) of fast electrons is formed (flying, in particular, behind the anode from a metal mesh or a sufficiently thin foil).

When the generated beam of fast electrons is decelerated by an electric field of positive ions, neutral gas particles, structural elements of the discharge region (including, for example, a heavy metal anticathode) and / or an additional external electric field, bremsstrahlung and characteristic x-rays are generated, as well as short-wavelength optical (usually UV and violet) radiation (due mainly to the excitation of heavy gas particles by electrons of the ionization cascade accelerated by the average electric field level) and various reactive compounds (such as ozone or nitrogen oxides in the air) by reacting the cascade ionization of electrons with molecules (atoms) gas.

In the most general form, the above-mentioned new regime of operation of a high-voltage discharge in dense gases can be described by a condition like

where E _n is the characteristic value of the electric field in the region of the front of the ionization wave;

N is the concentration of neutral particles of the gas mixture in the considered region of the electric field (according to the Clapeyron-Mendeleev law N = p / (kT), p is the gas pressure, k is the Boltzmann constant, T is the absolute temperature of the gas);

(E / N) _cr = E _cr / N is the critical value of the electric field strength, reduced to a unit gas concentration.

Condition (1), therefore, describes the discharge mode, in which another new and significant difference from the known discharge modes is the possibility of creating not only the near-cathode region of runaway electron generation, but also the anode region, and, generally speaking, any number of near-electrode regions ( including for electrodes under a floating potential), in which runaway electron generation can occur, caused by a rather rapid increase in the potential difference between this electrode and a positive volume a bulk charge formed in the gas by a primary runaway electron beam generated in the cathode region. The indicated potential differences exist for a short enough time so that the discharge does not have time to go to the channel stage and the main energy of such a discharge mode is used to generate fast electrons, multiply them in the outer zone or accelerate them in the interelectrode gap in the middle field, distorted by the influence of the field of positive ions formed in a gas following the passage of a beam of primary runaway electrons. In this case, the condition for acceleration of primary electrons or electrons of the ionization cascade with energy ε is the inequality

where e is the electron charge;

F (ε) = d∈ / dx — known specific energy losses of electrons with energy ε in a gas. For primary electrons of the beam, usually ε≈0.7 eU ₀ .

Consequently, in discharge mode (1), the mean field strength is ЕЕЕ _cr , which all known methods of generating runaway electrons in a gas strive to achieve.

Thus, the third significant difference of the proposed method from the known ones follows, namely, that the average field in the volume type of discharge can be many times smaller than in known modes and, therefore, either lower discharge voltages can be used or a discharge can be obtained in gaps with significantly larger sizes at the same voltage of the power source. In particular, pushing the anode far enough away from the cathode, we obtain a corona discharge with runaway electrons.

Let us estimate the maximum amplitude of a voltage pulse with a duration of 1 ns, which can be applied to the gap to generate fast runaway electrons in a dense gas without the transition of the discharge to the spark stage.

Knowing the type of working gas, its pressure and temperature (that is, knowing N from the Clapeyron-Mendeleev law), the constant (E / N) _cr (the most consistent and accurate calculation of this constant for various gases is described in the monograph [40] or in the link [1 ]), as well as the speed V _n (the most sequential and exact task of calculating the velocity of the front of the ionization wave during streamer breakdown of a gas is described in monograph [4] or in reference [18]) from the inequality

one can determine either the maximum duration τ _U of the voltage pulse at a given voltage amplitude U, or the maximum voltage amplitude at a given τ _U at which fast electrons, ions, atoms, etc. will be generated in the dense gas under consideration. without transition of the discharge to the spark stage.

The above references to public sources are quite sufficient to calculate V _n and N on a computer or graphically from experimental data, which can be used to determine U and τ _U that satisfy conditions (1).

However, for greater credibility, we present the simplest version of calculating the maximum U for a given τ _U , which does not require graphing or computer calculation.

The simplest formulas for V _n can be taken, for example, from such publicly available sources as [42], where a formula is given for the velocity of secondary breakdown waves, which also describes the speed of propagation of the ionization wave V _n under conditions of gas preionization by runaway electrons

where α is the first Townsend coefficient, μ _e is the electron mobility in the field of the applied potential U, K is the numerical coefficient determined by the structure of the ionization wave, which for the estimates of interest to us can be set to 1. In formula (1B), the quantities α and μ _e can be taken from textbooks and reference books on the physics of low-temperature plasma, for example, from [43]. To calculate these quantities, one can use both the experimental data given in [7] and analytical semi-empirical or empirical dependences, in particular, the formula

where p is the gas pressure.

For the most important case in practical terms - air under normal conditions (atmospheric pressure and room temperature) - as follows from the above public sources, А · р = 11400 cm ^-1 , В · р = 2.774 · 10 ⁵ V / cm, and μ _e (U) for E> 0.1 · E _{cr of} interest to us can be approximately considered constant and equal to 370 cm ² / V s). Then, rewriting inequality (1) in the form

and performing elementary transformations, we obtain (for τ _U = 1 ns, d = 2 cm)

which agrees very well with the region of the onset of exponential growth (80 kV / 1 ns = 8 · 10 ¹³ V / s) of the experimental curve of the dependence of the amplitude of the current of fast electrons on the rate of increase of voltage across the gap with the same parameter values obtained in our work [28] . Moreover, the found value of E = 78.7 / 2 kV / cm = 39.35 kV / cm is 6.94 times (!) Less than E _cr = 273 kV / cm. Which fully confirms the statements made in claim 1 of the claims.

The principles of operation of the discharge mode, satisfying the condition (1), are illustrated in Fig.1-6, where 1 is a high-voltage input; 2 - the working part of the high voltage electrode; 3, 8 - near-cathode and anode zones of runaway electron generation, respectively; 4, 5 - the direction of the resulting average electric field strength, taking into account the distorting effect of the space charge of positive ions generated in the gas during the passage of the primary beam of runaway electrons; 6 is an exemplary profile of the potential distribution of positively charged ions in a gas after passing through a primary runaway electron beam; 7 - region of maximum concentration of positive spatial charge of ions formed after the passage of the primary beam of runaway electrons; 9 - the working part of the low voltage electrode; 10 - ground circuit of a low voltage electrode, which may not be grounded; 11 - output to the oscilloscope signal from a calibrated inductance of the current collector of a beam of fast electrons; 12 - electron beam current collector (usually graphite); 13 - dielectric screen for complete interruption of the beam current to the collector; 14 - the main direction of motion of the primary beam of fast electrons in the discharge; 15 - the main direction of motion of the electron beam, compensating for the space charge in region 7; 16 - x-ray radiation of the discharge; 17 — UV and violet discharge radiation; 18 - fast ions; 19 - fast atoms; 20 - ozone or other chemically active molecules; 21 - branched high-voltage input; 22 - dielectric walls of a discharge tube or channel in a dielectric; 23 - anti-cathode with a small area of the working part to create a point source of inhibitory x-ray radiation; 24, 25 - dielectric barriers; 26 - sealed area for a chemical reaction; 27 - walls of the sealed area; 28 - gas pumping device; 29 - the region of generation of chemically active molecules; 30 - dielectric walls or windows.

Figure 1 schematically shows the main elements of the discharge occurring in mode (1). One of the main options of the proposed method is as follows. Through a high-voltage input 1, a voltage pulse (for example, negative) is supplied to the high-voltage electrode 2 with parameters satisfying condition (1). In the near-electrode zone 3, a spatio-temporal localization of the potential occurs, the field strength in zone 3 increases very rapidly, accelerating ions and generating fast atoms when they are recharged, both of them knock out new electrons from the cathode surface, and also fly into the cathode region and can be used for various kinds of applications. An increase in the concentration gradients of charged particles at the front of this slowly expanding cathode region 3 causes a further increase in the electric field strength in it, reaching “supercritical” values for runaway electrons, the plasma electrons are put into runaway mode, and the primary ionization front of the gas is formed by runaway electrons - an electron beam 14 which can be used for various applications. In this case, generally speaking, the anode 9 may not exist at all. In this case, a high-voltage corona discharge with runaway electrons is observed.

If the anode 9 is present, then the electron beam 14 can accelerate in a stronger average field of the cathode-anode and penetrate into the anode space when the anode 9 is a grid or a sufficiently thin foil. Moreover, generally speaking, the anode can be grounded or not grounded (unlike the known methods), be composite, have different sizes and shapes, but in any case, when a primary beam of runaway electrons passes from the cathode to the anode in fractions of a nanosecond (at atmospheric pressure gas) a space charge of positively charged ions is formed. This charge is a potential having a spatial distribution such as curve 6, which, generally speaking, can briefly turn the anode 9 into a cathode, for which it itself will act as an anode. In this case, the same processes occur near electrode 9 that we described above for electrode 2, only the electron beam generated in region 8 is inhibited mainly from the other side of region 7 (field 4), neutralizing the space charge of ions and thus completing , the discharge process in that mode, which is described by condition (1). As we have already described above, in dense gases, runaway electron beams automatically generate rather powerful x-ray bremsstrahlung 16, UV and violet radiation 17, as well as a high concentration of ozone or other chemically active molecules 20.

Generally speaking, any electrode system such as that shown in FIG. 1 (called, in this case, a gas diode) has an equivalent circuit in the form of a series LC circuit in which there is an external voltage source U. Therefore, in the case of a short duration τ _U the voltage pulse U of the high-voltage power supply, however, it is possible to obtain the generation of ionizing radiation beams in mode (1) if the voltage is sharpened (the voltage pulse front is shortened) in the gap between the high-voltage electrode and the ground a given electrode (voltage at the electrodes of a gas diode), for example, about K times due to the choice of inductance L and capacitance C of the diode (measured between the connection point of the high voltage output of the power source with the high voltage diode electrode and the common point of the grounded diode electrode and the ground of the power source) in accordance with the relation (L · C) ≈ (2τ _U / (πК)) ² , if necessary, then shortening the duration of the sharpened voltage pulse to the required value with a cutting spark gap or the like

To obtain higher currents of ionizing radiation beams and chemically active molecules, as well as to generate them at a sufficiently small τ _U limited by the characteristics of the used high-voltage power supply, for the delay in the development of a volume streamer discharge necessary in the latter case in accordance with the condition τ _U ≤τ _d / (E _cr / E) use a combination of a volume discharge with a discharge on the surface of the dielectric, or with a discharge in a dielectric tube (shielded or not shielded) or in a dielectric channel, the length of the dielectric part L in which is chosen so that the surface discharge substantially increases the electron concentration in region 3 as it moves along the dielectric surface from the cathode to the boundary with the gas gap - in this case, usually L ~ (2 ÷ 3) d or also sharpened the front ionization waves arriving at the boundary of the insulator with the gas volume (which is equivalent in this case to a shortening of τ _U ), in this case usually L ~ (3 ÷ 4) d. A corresponding illustration is shown in FIG. 2 a, b, c. A high voltage pulse is fed through input 1 to a high-voltage electrode 2 (23 in Fig. 2c) located on the surface of the dielectric 22, which, generally speaking, can have an arbitrary shape, for example, cylindrical (Fig. 2 a) or conical (Fig. 2 b , c), and may also have more than one outlet. At the metal-insulator-gas contact point, a sharp nonuniformity of the potential gradient occurs, which then, in a mode close to the autowave, moves towards the boundary of the dielectric with the gas volume — region 3 in FIG. 2. In this case, as usual, the ionization wave front velocity (plasma electron energy) and the concentration gradient of charged particles at the front increase, which improves the conditions for the generation of runaway electrons 14 in the gas gap. The general nature of the subsequent processes is generally the same as in Figure 1. To increase the cathode area at the same output diameter of the dielectric channel, the conical shape of the surface of the dielectric 22 is used, as shown in FIG. 2b. In this case, for example, a solid metal (usually tungsten) cone with a radius of apex of about 1-2 mm, which in this case generates a dense beam of bremsstrahlung and characteristic x-ray radiation 16, if the output inner diameter of the dielectric channel is sufficiently small, can serve as the anode. Figure 2c shows a variant of the point source of an x-ray emitter (for medicine, flaw detection, baggage control systems, etc.), in which the cathode 2 is grounded and the positively charged anode 23 is at the same time a target (with a small area of the working part) for braking the beam electrons 14 and generation of X-ray radiation 16 diverging from a “point”, having quantum energy (generally speaking, from units of keV to hundreds of keV), regulated not so much by the voltage amplitude at electrode 23 as by the distance between electrodes 2 and 23, and also, how we will show below, by the ratio of the sizes of the cross sections of the electrodes 2 and 23.

Thus, the fourth new significant difference of the proposed method is its operation in mode (1) in combination with a volume (corona) discharge with a discharge on the surface of the dielectric (or discharge in dielectric tubes), which improves the parameters of the runaway electron beam generated by the discharge.

Here, we can separately note the fifth significant difference of the proposed method, namely, that with the combined discharge described above, the maximum current densities of the primary runaway electron beam can be realized, which in the braking field of the positive ion space charge (field 5 in FIG. 1) without any either brake metal targets generate a powerful x-ray flux with a quantum energy of up to hundreds of keV from a region with a sufficiently small size, which in many cases can be easily considered The current source currently used for a wide range of applications in the form of vacuum X-ray tubes.

To increase the total number of fast electrons, ions, atoms and, in the corresponding gas mixture, chemically active particles, as well as to increase the power of X-ray and optical radiation generated by a gas discharge with runaway electrons, the discharge mode (1) is simultaneously provided for many generating fast electrons the electrode regions 3, as shown in FIG. 3. To do this, at least one discharge electrode 2 is made in the form of a metal surface of the required area, having a set of inhomogeneities with dimensions tending to the same and substantially smaller d with a height and thickness ratio of inhomogeneity tending to 10. Moreover, to obtain ionizing beams that are as uniform as possible in cross section of radiation, the ratio of the average distances between the maxima of the inhomogeneities at different electrodes makes, as far as possible, close to the ratio of the transverse dimensions of these electrodes the wallpaper. In this case, the average distance between the inhomogeneities on the smaller electrode 9 makes at least the transverse size of the near-electrode region generating runaway electrons, otherwise the smaller electrode may have a metal surface that is smooth at a level accessible for ordinary mechanical grinding. For example, as a multi-tip electrode, a metal wire mesh with a mesh size from fractions of a mm to several mm having a wire thickness closest to 1/10 of the mesh size can be used, or a set of metal hacksaw blades, etc. can be used. with the corresponding sizes of heterogeneities and the distances between them. Figure 3 shows the one-dimensional branching 21 of the high-voltage input (which may, if necessary, be two-dimensional for perpendicular rotation of at least one of the generation of branches) with the same length of branches and the same number of branches to all points of contact with the high-voltage electrode. In this case, the high-voltage potential is supplied to all inhomogeneities of one electrode simultaneously with an accuracy of time on the order of τ _U.

Thus, the sixth significant difference of the proposed method is the possibility of obtaining a multi-channel and homogeneous diffuse discharge with electrodes of a large area associated with the autowave nature of the movement of the ionization front, which is a serious problem for dense gases for known methods.

Including the discharge mode (1), it is easily ensured simultaneously for a plurality of metal cathodes inserted inside cylindrical or cone-shaped dielectric tubes or channels in the dielectric 22 (shielded or not shielded, usually having a length L of the order of (2 ÷ 3) d and the diameter of the outlet opening of order (0.1 ÷ 0.2) d) located along the direction of the applied external electric field (or at an acute angle to it) and having from the opposite side of the tubes (channels) from the cathodes (output) one common anode or a set of anodes, laid in the same gas on the order of a characteristic distance d from the outlet end of the tubes (channels), as shown in Figure 4. Moreover, to obtain the most homogeneous in the cross section of ionizing radiation beams, the distance between the axes of the dielectric tubes (channels) is made as small as possible, and to obtain the maximum power density of ionizing radiation in the region of the anode, the latter is made of the smallest possible area and usually hemispherical, and the direction of the tubes (channels) are chosen so that the outlet openings of the tubes (channels) are directed (concentrated) to the center of the anode and are approximately the same distance from the negative o, and the high-voltage potential is supplied to all tubes (channels) simultaneously up to a time of the order of τ _U , for which, for example, one-dimensional or two-dimensional branches of the high-voltage input 21 are used with the same branch length and the same number of branches to all cathodes.

All of the above particular cases of the implementation of the proposed method for generating beams of ionizing radiation and chemically active gases can be successfully used for a wide range of applications in which runaway electrons are used mainly within the interelectrode gap, for example, to initiate a discharge in a dense gas laser or excitation its active medium or for sterilizing air and other gas mixtures by a discharge with runaway electrons. However, the amplitude of the current of the electron beam in the anode space, where it is usually measured using any current collectors, can even be almost zero, since the electrons of the primary beam are decelerated in field 5 of the space charge 6. If it is necessary to increase the current of runaway electrons in the anode space , you can try just to bring the anode 9 closer to the cathode 2. In this case, however, the discharge region will decrease (which is not always acceptable), the energy of the runaway electrons will change, and the discharge will lose controllability, because condition (1) may be violated and the discharge will go into an ineffective channel form. An increase in the current density of runaway electrons in the interelectrode gap and behind the anode space is more expediently carried out in a different, non-trivial manner, shown in FIG. 2. This particular case of the implementation of the proposed method is based on compensation for a possible decrease in the space charge of positive ions 6 (formed in the trace of the passage of the primary beam of runaway electrons 14 through the gas and leading to a reverse current of electrons 15 in the gas in the case when the cathode area is less than or the same as the anode area ) by choosing the geometry of the electrodes 2 and 9 such that, in the direction from the cathode 2 to the anode 9, the total cross section of the beams of fast electrons is constantly and sufficiently substantially reduced, for which Example, select the appropriate ratio of the size and / or shape of the anode and cathode (for example, as shown in Figure 2, or, for example, when using the geometry of electrodes of spherical, cylindrical, etc. types), as well as the distance d between them, or use for the gradual narrowing of the beam of fast electrons the corresponding configuration of the external longitudinal magnetic field with increasing intensity towards the anode.

Thus, the seventh new and significant difference of the proposed method is the ability to control the current density and energy of fast electrons in the interelectrode gap and in the anode space by using the concentration (gradual narrowing) of the electron beam towards the anode, which completely compensates for the influence of the decay of the potential distribution of 6 positive ions in the gas.

If τ _{U is} not small enough, limited by the characteristics of the high-voltage power source used, for the delay in the development of the streamer volume discharge necessary in this case, τ _{d is} increased in accordance with the condition τ _U ≤ τ _d / (Е _cr / E), set in the interelectrode gap (as shown 5) or two dielectric barriers 24 and 25 (passing rather high-energy runaway electrons and absorbing almost completely slow electrons almost without absorption) - one close to the anode 25, and the second - 24 a state of order (1 ÷ 2) · Δ from the cathode, or one thicker barrier 25 at a distance d of more than 2 · Δ from the cathode, on the reverse side of which an anode grid is deposited or attached. The barrier 25, located close to the anode, prevents the appearance of zone 8 and the growth of the streamer from the anode to the cathode through a channel ionized by a primary beam of fast electrons. The barrier 24 delays the expansion of zone 3 towards the anode, increasing the time to increase the field strength in zone 3 to “supercritical” values.

Thus, the eighth significant difference of the proposed method is to indicate the location of the dielectric barriers 24 and 25, associated with the value Δ ~ τ _U · V _n , determined both by the kind and pressure of the gas, and by the type of discharge, as well as the values of τ _U , d and U ₀ . Moreover, the value of τ _{U is} given by the power source, and V _n can be easily estimated using well-known formulas [36].

If the duration τ _{U is} not short enough to fulfill condition (1), a special case of the proposed method can also be used, characterized in that the grounded electrode (located at a distance d from the high voltage) is disconnected from the ground, leaving it at a floating potential, and at a distance D from they have an additional electrode that is grounded, and the distance D and the shape of the additional electrode (sometimes also the shape of the electrode under the floating potential and the corresponding insulators) are chosen so that when when voltage U was applied to the high-voltage electrode, a discharge first occurred between the grounded additional electrode and the electrode with a floating potential, in contrast to [37] sharpening and shortening the potential between the high-voltage electrode and the electrode under the floating potential to the required value of τ _U , at which this potential then allows to carry out a discharge satisfying condition (1).

In a number of applications, it may be useful to special case of the proposed method, characterized in that to control the beam (s) of fast electrons in the discharge gap, an additional several grounded or floating potential electrodes and dielectric barriers are installed that provide sequential acceleration and / or rotation of fast electron beams generated initially in one of the electrode regions of the discharge.

The ninth significant difference (including from the method [31]) of the proposed method may be a particular case, characterized in that in order to increase the duration and current density of the electron beam, additional electrodes are made using gas-tight films and / or foils and placed so so that it is possible to maintain different gas pressures in different sections of the interelectrode space, thereby ensuring optimal conditions for the generation of fast electrons in one of these spaces and the amplification of the current of the fast beam electrons due to the avalanche multiplication of electrons in a gas in the next (next) interval (s).

In a number of applications, it may be useful for a particular case of the implementation of the proposed method, similar to the above, but characterized in that the energy spectrum and current density of the electrons generated (propagated) in the gas-filled interelectrode gap can be changed continuously or periodically, if necessary, by changing the composition and pressure of the gas mixture enclosed in a hermetically sealed section of said interelectrode gap, thereby optimizing the above beam parameters for more efficient about this or that application. This particular case is based on experimental data [19], which demonstrate the dependence of the energy spectrum of runaway electrons in a volume discharge on the type and pressure of the gas for the same parameters of the power source.

The same technical result — the regulation of the energy spectrum of fast electrons obtained in the interelectrode gap or in the anode region of the discharge — can also be obtained by using the dielectric barriers mentioned above (at least partially transparent for runaway electrons with a sufficiently high energy), but with different absorption capacity and installed in those areas of the discharge gap in which it is necessary to regulate the energy spectrum of runaway electrons.

To increase the instantaneous power of x-ray radiation that extends beyond the discharge zone as isotropically as possible (point source of x-ray radiation), a special case of the implementation of the proposed method can be applied, characterized in that a beam of fast electrons is generated from the maximum possible cathode area and sent to a smaller metal anticathode (usually with the size of the working part 1 ÷ 2 mm, approximately as shown in Fig.2b), and to change the energy of quanta (wavelength) of X-ray radiation from anticat Yes, along with a change in the amplitude of the applied voltage (which is possible, obviously, within a region limited by the existence of this discharge, taking into account the nonlinear effect of the voltage on the electron beam current, and therefore on the X-ray power), a change in the cathode-anticathode distance or the degree of concentration of the fast electron beam at this distance (which, as a rule, is much simpler than changing the voltage in the discharge gap), as well as placing transparent in the interelectrode gap for sufficient but high-energy runaway electrons of dielectric barriers that change the energy of fast electrons in the beam, and, accordingly, the energy distribution of quanta of bremsstrahlung at the anticathode.

Another special case of the proposed method, used to increase the instantaneous power of x-ray radiation outside the discharge zone, is the case illustrated by Fig. 2a, characterized in that two or more opposing fast electron beams 14 and 15 are generated, one of which 14 has a start on the cathode with an area of one order of magnitude or less than the area of the anodes from which other beams 15 begin, and all the beams converge in the region of positive space charge, which is generated by the first beam 14 in the interele in the electrode gap, and for changing the energy of quanta (wavelength) of X-ray radiation (generated during the deceleration of electron beams in an electric field in the region of decay of the spatial distribution of 6 positive ions in the interelectrode gap) along with a change in the amplitude of the applied voltage (which is possible, obviously, within limited by the region of existence of this discharge, taking into account the nonlinear effect of voltage on the electron beam current, and therefore, on the x-ray power), we used cause a change in the cathode – anode distance or the degree of concentration of a fast electron beam at this distance (which is usually much simpler than a change in voltage in the discharge gap), as well as the placement of dielectric barriers transparent to sufficiently high energy runaway electrons in the interelectrode gap, which change the energy of fast electrons in the beam, and, accordingly, the energy distribution of quanta of bremsstrahlung in the interelectrode gap.

To create a high concentration of ozone, nitrogen oxides, or other chemically active or excited atoms or molecules in any closed gas volume 26 shown in Fig. 6 (for example, to excite lasers on aggressive excimer media, or to obtain a high and controlled concentration chemically active gases in closed volumes of the corresponding chemical reactions, having, in the general case, in this closed volume the composition of gases different from the gas composition in the rest of the interelectrode gap), at least part 29 of the decree The enclosed closed volume, having walls (windows) 30 of a dielectric film partially transparent for sufficiently high-energy electrons, is placed in the interelectrode interval of a 2–9 discharge that satisfies condition (1), using fast discharge electrons, corresponding chemically active particles are generated inside this part of the gas volume or excited molecules 20 to create the necessary concentrations in a pulse-periodic mode and, if necessary, pumped using a pumping system 28 a gas mixture from region 29, located within the interelectrode gap in the remaining area 26 of the closed gas volume, with all the structural elements of high-voltage generator 1, 2, 9, 10 are out of range of reactive or corrosive gases.

Thus, the tenth new and significant difference of the proposed method is the ability to efficiently generate using a discharge with a mode of operation determined by condition (1) chemically active or excited atoms or molecules in chemically aggressive gases without direct contact of the structural elements of the discharge with these gases.

A private variant of the proposed method, effective for generating chemically active or excited atoms or molecules in a gas volume with access through a small (compared to the size of the anode) inlet or located outside the window of a dielectric film (metal foil), at least partially transparent to electrons with sufficiently high energy is a discharge with a regime of type (1), the high-voltage (in the case of a single-electrode corona discharge) or low-voltage electrode of which is placed in air at maximum awns from the inlet of said window or above the gas discharge volume and produce a series of pulses to create and maintain a desired concentration of reactive or excited atoms and molecules in the gas volume due to runaway electrons, UV and X-rays penetrating through the inlet opening or window.

Implementation of the proposed method was carried out using pulsed high-voltage voltage sources on the basis of three main pulse generation circuits with voltages of the order of 100 ÷ 300 kV, namely, on the basis of a) a capacitive storage device according to the Marx generator circuit with an sharpening capacitor, a gas spark gap and a forming line [25, 26] (U ₀ up to 300 kV, the duration of the leading edge of the voltage pulse at the active load τ _FU = 3 ns, the duration τ _{U of the} pulse U at half maximum is 6 ns); b) a pulse transformer with a serial gas discharger P-49 and a forming line (U ₀ = 130 kV, τ _FU = 1.2 ns, τ _U = 2.5 ns, pulse repetition rate f = 5 Hz); c) an inductive energy storage device with current isolators based on SOS diodes, peaking and cutting off semiconductor arresters [38] (U ₀ = 150 kV, τ _FU = 0.3 ns, τ _U = 2 ns, f = 3 kHz). For example, Fig. 7 shows a circuit diagram of the high-voltage part of the power source according to option "b", to which a constant voltage of +7 kV is supplied from a standard network thyristor converter. Here 31 is a set of parallel switching arresters, 32 is a pulse transformer for an output voltage of up to 150 kV, 33 is a R-49 spark gap, 34 is a gas diode, L ₁ is a shunt inductance, C ₁ , C ₂ are storage and sharpening capacitors, D ₁ - diode.

The fact of the presence of a beam of fast electrons (ions) and UV radiation was detected by three different methods: by glowing cathodoluminescent screens or sapphire crystals with titanium (for detecting electrons located behind black paper, cardboard or aluminum foil with different thicknesses), as well as by a luminescent signal from quartz optical fiber for detecting fast electrons covered by black paper or aluminum foil entering through a light filter (or MDR-12 monochromator) to a PMT, and then to an oscilloscope.

To measure the shape of the current pulse of fast electrons, we used both standard type Faraday cylinders and a specially designed inductive current collector, shown in Fig. 1 and consisting of a graphite collector 12 with a receiving end face with a diameter of 7.5 mm (forming a small collector-cathode capacitance) and calibrated inductance 11 value L _s = 2.7 nH (3 nH for collector No. 2). The collector resistance is almost zero. Such a collector from the ground side was connected in a non-inductive manner to anode 9, and the signal U _Sθ = L _s · d (i _D + θ · i _B ) / dt taken from a calibrated inductance 11 was fed to a Tektronix 3052 oscilloscope with an analog band of 500 MHz and a digitizing speed single signal in real time 5 MS / s. Here, i _D is the bias current in the collector circuit, i _B is the current of fast electrons to the collector end face, θ is the transmittance of fast electrons by a screen or foil 13 installed behind the anode 9, as shown in FIG. 1. The process of measuring the current of fast electrons took place in two stages. First, the signal U _s1 = L _s · d (i _D + i _B ) / dt was measured at θ = 1, that is, without a screen or foil 13. Then, under the same experimental conditions, a dielectric screen or calibrated metal foil 13 was installed immediately after the anode 9 thickness and the signal was measured U _s0 = L _s · di _D / dt at θ = 0 (a sufficiently thick screen, for example, 1 mm of polyethylene). Subtracting U _s0 from U _s, we obtain ΔU _s = L _s · di _B / dt, integrating which over time numerically, dividing by L _s , we obtain the current of fast electrons to the collector i _B (t). Examples of corresponding waveforms are shown in Fig. 8, where 35 is the signal U _s1 , 36 is the signal U _s0 . The calculated fast electron current i _B (t) is shown in FIG. 9. At θ values between 0 and 1 (calibrated thin metal foils), the electron energy in the beam behind the anode was measured in the same way using the calibrated foul method.

Since the duration of the fast electron current front is about 1 ns, we compared the measured signals with a Tektronix 3052 oscilloscope and a Tektronix TDS-820 oscilloscope with an analog 6 GHz bandwidth. Comparisons showed that the signals from the Tektronix 3052 oscilloscope have extended edges, but the signal distortion does not exceed 10-15%, which falls within the experimental data repeatability range, therefore, our measurements on this oscilloscope can be completely trusted.

Since apart from the active component, the standard Faraday cylinders have large inductive and capacitive components in the resulting measured voltage drop when the front of the measured signal is about 1 ns long, interpreting the signals measured by them is a difficult task related to solving the integro-differential equation by the regularization method. Therefore, the main meter of fast electron current was the inductive collector described above, for which the processing of the measured signal is much simpler.

Figure 10 shows a photograph of a discharge with an operating mode satisfying condition (1) obtained in air under normal conditions with the power source shown in Figure 7. Here 37 is the bushing of the high voltage input. The cathode 2 is made of copper in the form of a cone with a rounded vertex with a radius of 2 mm. Anode 9 is a brass grid with a mesh size of 0.7 mm. d = 1.7 cm. 38 - black paper that does not transmit UV and visible discharge radiation to the cathodoluminescent screen 39. 40 - discharge with runaway electrons (UE) of mixed corona and volume types, 41 - discharge with UE of pure corona type, 42 - discharge with RE on the surface of the dielectric. Figure 10 shows the glow (almost white) of region 3; luminescence (violet) of air molecules excited by electrons of the ionization cascade, accelerated in the interelectrode gap 40; the luminescence (blue) of the cathodoluminescent screen 39 caused by fast electrons passing into the anode region through the black paper 38. The cathodoluminescent screen placed in the region of the gas glow from the corona discharge 41, covered by the black paper or aluminum foil (10 μm) placed in front of it, also glows and under the influence of runaway electrons from this type of discharge. A similar glow of such a screen 39 is also observed when approaching from the side 42 to the outer circumference of the bushing 37, which confirms the fact that fast electrons are generated in the discharge along the surface of the dielectric (plexiglass) under condition (1). The uniqueness of the picture depicted in Fig. 10 also lies in the fact that three different forms of discharge simultaneously operate stably from one power source - corona 41, volume 40 and along the surface of the dielectric 42. This can serve as an indirect confirmation of the autowave nature of the movement of the ionization fronts in given discharge mode.

A discharge with parameters satisfying condition (1) was also obtained by us with the “a” and “b” power sources described above. In particular, with a power source on a Marx generator with a flat electrode area of more than 1000 cm ^{2, the} discharge was transferred from the channel form to mode (1) by both shortening τ _{U with a} cutting spark gap from 7 ns to 4 ns, and by reducing V _n , which was achieved by increasing d from the recommended value in [25, 26] 1.0 cm to 6 cm. The discharge mode satisfying condition (1) was implemented by us on the same power source with a Marx generator using a 5 mm diameter dielectric tube dielectric part 12 cm at d = 5 cm, as well as when using two dacron barriers 100 μm thick, one of which was installed close to the anode, and the second at a distance of 3 mm from the cathode (at d = 5.5 cm, in which, in accordance with [25, 26] distance cathode barrier 24 should be 1.1 cm).

Figure 11 shows a photograph of the same discharge as in Figure 10, but with d = 55 mm and the location of the anode 9 on the side of the axis of the high-voltage electrode 2. The picture is similar to a bipolar corona discharge, but with registration of fast electrons emanating from the interelectrode gap to screen 39.

Figure 12 shows a photograph of the corona discharge under the same conditions, but with three electrodes at d = 45 mm from the cathode 2 to each of the anodes 9. The photographs in Figures 11 and 12 are irrefutable evidence of the correctness of the physical discharge model that satisfies the condition ( 1), which we use to describe the basic physical processes in it.

Figure 13 shows a photograph of a discharge from two wire (2 mm diameter) cathodes to a grounded electrode 43 and to an electrode with a floating potential 44, as well as between these electrodes. In this case, the cathodoluminescent screen behind the black paper luminesces, which confirms the generation of fast electrons penetrating the screen in the discharge. This experiment confirms the possibility of independent generation of fast electrons simultaneously from several near-electrode zones of type 3, as well as the possibility of a discharge working with ungrounded electrodes and from them to grounded electrodes ..

On Fig shows a photograph of a typical volume discharge with a flat brass cathode of circular cross section with a diameter of 1 cm with d = 1.7 cm. A cathodoluminescent screen detects the presence of electrons behind black paper in the anode region. A system of cathode zones 3 is observed at the cathode. The region of positive charge 7 is located near the anode 9.

The results of measuring the current of fast electrons in the anode region of the experiment of Fig. 14 (power supply "b") using the inductive collector described above, shown in Figs. 8 and 9, show that the current density in this discharge configuration reaches 50 A / cm ² , and the amplitude of the total electron beam current in the anode region reaches 180 A.

At the concentration of the runaway electron beam (RE) due to the selection of the hemispherical shape of the grid electrodes, as shown in Fig. 3, with a cathode diameter of 5 cm and an anode of 0.8 cm at d = 5 cm with the same power source in air under normal conditions, the amplitude was obtained the current density of the RE behind the anode, exceeding 150 A / cm ² , and the amplitude of the total current of RE in the anode region is estimated to be more than 500 A.

It was possible to realize even higher amplitude values of the current density of the RE in an experiment performed according to the scheme of Fig. 2a, i.e., in a discharge that is a combination of a discharge in a cylindrical dielectric unshielded quartz tube with a diameter of 9 mm, the length of the dielectric discharge part L = 2d, with d = 4 cm. A hemisphere of brass mesh with a diameter of 5 mm with a mesh size of 0.7 mm and a wire diameter of 0.2 mm was used as the anode. The amplitude of the current density of REs in the anode region near the discharge axis in this case reached 300 A / cm ² .

Thus, the feasibility of the discharge mode described by condition (1) and the generation efficiency of RE beams in it have been experimentally confirmed. At discharge voltages from 100 kV to 300 kV, the energy of the majority of REs in the ananode region, measured using an inductive collector and calibrated foils (according to the standard method of calibrated foils), ranged from 70 keV to 250 keV.

The possibility of generating UE beams with a large aperture has also been experimentally confirmed. For example, we obtained a RE beam in air under normal conditions with an output aperture (anode area of a brass mesh with a mesh size of 0.7 mm) 4 cm × 30 cm for a discharge with the operating mode (1), U ₀ = 300 kV, τ _FU = 3 ns, τ _U = 4 ns, d = 1 cm, the cathode — 19 hacksaw blades, the cross-sectional area of the cathode was 6 cm × 31 cm. Under these conditions, the amplitude of the beam current density in the anode region was more than 20 A / cm ² , and the amplitude the total current of the RE beam exceeded 3 kA, which is many times higher than the current of the fast electron beam observed by known methods in a volume discharge in zduhe under normal conditions.

The possibility of generating x-ray radiation at atmospheric pressure with energies in the pulse of not nJ, as in the known methods, but at least μJ, which at a pulse repetition rate of 3 ÷ 5 kHz (power supplies using semiconductor current breakers) provides the standard for medical X-ray machines, the dose of 0.5 R in 0.2 s. We measured the dose rate of the X-ray radiation of the discharge with the operating mode (1) using the DRGZ-1 dosimeter. At a pulse repetition rate of 4 Hz, dose rates from 50 μR / s (in the experimental design corresponding to FIG. 1) to 2 mR / s (in the experimental design corresponding to FIG. 2a) were obtained. To record high X-ray dose rates, a diaphragm was used in the lead screen in front of the receiving aperture of the dosimeter, followed by summing up the measurements with different positions of the diaphragm relative to the axis of the receiving aperture (since the upper limit of the dosimeter was lower than necessary).

Direct evidence of obtaining x-ray radiation in the discharge according to the claimed method is to obtain an x-ray image (Fig. 15) of sample 45 in the form of a letter Z made of 300 μm thick copper foil (close to the absorption capacity of human chest bones), placed in a black paper bag located at a distance of 10 cm from the discharge axis between two flat electrodes with a grid cathode diameter of 4 cm and a solid brass anode diameter of 2 cm. To obtain the image of Fig. 15, radiation from 70 pulses was used. but.

When the discharge operates in the mode determined by condition (1), a high concentration of ozone molecules is generated in atmospheric pressure air, which is easily detected by its characteristic odor. Estimates of the ozone concentration were carried out by us based on the change (after the discharge was turned on) of the absorption of violet radiation passing through a hermetically sealed package of a 50 μm thick polyethylene film partially placed between the electrodes, similar to the experimental design of Fig. 6. The obtained estimates of ozone concentration of the order of 50 mg / m ³ show that discharge from REs is a very efficient ozone generator, quite comparable in efficiency with electron beams from vacuum diodes [39].

Thus, in several versions we experimentally implemented the inventive method with the achievement of the main technical results that it is aimed at, that is, with the generation of a beam of fast electrons, ions, atoms, X-ray, UV and violet radiation, as well as ozone, etc. chemically active molecules.

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Claims (16)

1. A method of producing beams of fast electrons, ions, atoms, as well as X-ray and UV radiation, ozone and / or other chemically active molecules, which consists in the fact that a high voltage pulse is applied to the electrode system in a gas with a pressure above several hundred Pa (above 500 Pa in most gases), characterized in that fast electrons (ions, atoms), as well as UV and X-rays, (in some gases, also chemically active molecules) generate (both in volumetric and in moving gas discharges, and also in gas discharge shielded or unshielded dielectric tube) with an anode-cathode electrode system or in the presence of several anodes or cathodes and even in the presence of only a solitary high-voltage electrode (unipolar corona discharge with runaway electrons) at an average electric field in the interelectrode gap (or near a solitary high-voltage electrode outside the ionization zone) is significantly lower than the critical value for runaway electron generation, for which the operating mode of a pulse-periodic gas new discharge is selected in accordance with the following condition

E _n is the characteristic value of the electric field in the near-electrode region of the front of the ionization wave; N is the concentration of neutral particles of the gas mixture in the considered region of the electric field; U is the potential of the high voltage electrode relative to earth or another nearby electrode; Δ ~ τ _U · V _n is the size along the direction of the average electric field of the space-time localization of the high-voltage potential; τ _U ~ d / V _U is the pulse duration of the potential U; V _n is the velocity of the front of the gas ionization wave by slow (plasma) electrons; E = U / d is the average field on a scale of size d, V _U = (d / U ₀ ) · (dU / dt) is the slew rate applied to the potential applied to the high-voltage electrode; d is the characteristic size of the interelectrode gap or the characteristic radius of curvature of the field near a single high-voltage electrode; U ₀ is the amplitude of the potential pulse; (E / N) _cr is the electric field strength E _cr reduced to a unit gas concentration at which the electrons in a given gas can acquire enough energy to “run away”, in other words, they apply a high voltage potential U to the electrode (s) at a sufficiently high speed increase

with a sufficiently short pulse duration

at a sufficiently low value of E and a sufficiently large d, which determines a sufficiently small value of V _n ~ E (in a longitudinal field) and a sufficiently large amount of time for the development of a streamer discharge under given conditions, τ _d ~ d / V _n and for a time τ _U ~ d / V _U in a region near the electrode (region runaway electron generation) having a size Δ order ionization zone size (for corona discharge) and a length substantially smaller interelectrode gap d (for surround and slide along the surface of the dielectric discharge and for discharges in shielded and n a shielded dielectric tube or in a discharge, which is a combination of the above), spatially-temporal localization of the gas ionization wave front is carried out near one or several electrodes, the double layer of charged particles of which provides, firstly, the acceleration of ions and fast atoms (obtained mainly during resonant charge exchange of ions in dense gases) in the direction of the cathode or dielectric, along which the discharge propagates, forming a beam of fast ions and atoms in the ionization zone near the cathode a dielectric, knocking out enough electrons to start the discharge, and if the cathode or dielectric has holes penetrating into the region behind the cathode or dielectric, secondly, the accelerated movement of a region of size Δ along the surface of the dielectric to its boundary with the anode or the gas volume through which the discharge continues to the anode (creeping discharge, discharge in dielectric tubes and their combination with volume discharge) with increasing concentration and energy of electrons in this region, and thirdly, increasing tension and the electric field is higher than the critical value for runaway electrons in a region of size Δ for a time of the order of τ _U , after which an ionization wave (and, in some conditions, a “counter” ionization wave from another electrode, compensating for the positive spatial charge), accelerating and / or avalanche propagating runaway electrons and electrons of the ionization cascade in an average field distorted by the space charge of positive ions, and a beam (s) of fast electrons are formed in (flying, in particular, behind an anode of a metal mesh or a sufficiently thin foil), when braking by an electric field of positive ions, neutral gas particles, structural elements of the discharge region (including, for example, an anticathode made of heavy metal) and / or an additional external electric The field generates bremsstrahlung and characteristic x-ray radiation, as well as short-wavelength optical (usually UV and violet) radiation (due mainly to the excitation of heavy gas particles by ionization electrons th stage accelerated average electric field discharge) and various reactive compounds (such as ozone or nitrogen oxides in the air) by reacting the cascade ionization of electrons with molecules (atoms) gas. 2. The method according to claim 1, characterized in that to increase the power of the generated radiation or to obtain beams of fast electrons, ions, atoms and chemically active molecules with a sufficiently small τ _U limited by the characteristics of the used high-voltage power supply (for the delay required in the latter case the development of a volume streamer discharge in accordance with condition (3)), use a combination of volume discharge with a discharge on the surface of the dielectric, or with a discharge in a dielectric tube (shielded or not shielded) anirovannoy having one or more outlet apertures) or in the dielectric channel length L of the dielectric part which is in the range (2 ÷ 4) d. 3. The method according to claim 1, characterized in that for a short duration τ _{U they} use the opportunity to exacerbate the voltage (shorten the front of the voltage pulse) in the gap between the high-voltage electrode and the grounded electrode (on the electrodes of the gas diode) by approximately K times by choosing the inductance L and capacitance C of the diode (measured between the connection point of the high-voltage output of the power source with the high-voltage electrode of the diode and the common point of the grounded electrode of the diode and the grounding of the power source) in accordance with the ratio

if necessary, then shortening the duration of the sharpened voltage pulse to the required value (3) with a cutting arrestor or the like. 4. The method according to any one of claims 1 to 3, characterized in that to increase the total number of fast electrons, ions, atoms and, in the corresponding gas mixture, chemically active particles, as well as to increase the power of x-ray and optical radiation generated by a gas discharge with by runaway electrons, the discharge mode (1) provides simultaneously for many near-electrode regions generating fast electrons, for which at least one discharge electrode is made in the form of a metal surface of the required area having a set of neo heterogeneities with dimensions tending to the same and substantially smaller d, with the ratio of the height and thickness of the inhomogeneity tending to 10, and to obtain the most homogeneous in the cross section of ionizing radiation beams, the ratio of the average distances between the maxima of the inhomogeneities at different electrodes is made as close as possible to the ratio of the transverse dimensions of these electrodes to each other, and the average distance between the inhomogeneities on the smaller electrode makes at least the transverse size of the near-electrode region tee that generates runaway electrons, otherwise the smaller electrode may have a metal surface that is smooth at a level that is accessible for conventional mechanical grinding (for example, as a multi-tip electrode, a mesh of metal wire with a mesh size from fractions of a mm to several mm having a wire thickness of closest to 1/10 of the cell size, or use a set of metal hacksaw blades, etc. with the corresponding dimensions of the inhomogeneities and the distances between them), the high-voltage potential being brought to all the inhomogeneities of one electrode simultaneously with an accuracy of about three, for which purpose, for example, one-dimensional or two-dimensional branches of the high-voltage input with the same branch length and the same number of branches to all points are used contact with a high voltage electrode. 5. The method according to any one of claims 1 to 3, characterized in that to increase the total number of fast electrons, ions, atoms and - in the corresponding gas mixture - chemically active particles, as well as to increase the power of x-ray and optical radiation generated by a gas discharge with runaway electrons, the discharge mode (1) is provided simultaneously for many metal cathodes inserted inside cylindrical or cone-shaped dielectric tubes or channels in the dielectric (shielded or not shielded, usually having a length L of the order of (2 ÷ 3) d and an outlet diameter of the order (0.1 ÷ 0.2) d) located along the direction of the applied external electric field (or at an acute angle to it) and having the opposite from the cathodes (output ) the sides of the tubes (channels) one common anode or a set of anodes located in the same gas at a characteristic distance of the order of d from the output end of the tubes (channels), moreover, to obtain the most homogeneous in the cross section of ionizing radiation beams, the distance between the axes of the dielectric tubes (channels) do n -the possibilities are minimal, and to obtain the maximum power density of ionizing radiation in the region of the anode, the latter is made of the smallest possible area and, usually, hemispherical, and the direction of the tubes (channels) is chosen so that the outlet openings of the tubes (channels) are directed (concentrated) to the center of the anode and were approximately at the same distance from it, and the high-voltage potential is supplied to all tubes (channels) simultaneously with an accuracy of time on the order of τ _U , for which, for example, one-dimensional or two-dimensional branching of a high-voltage input with the same branch length and the same number of branches to all cathodes. 6. The method according to any one of claims 1 to 5, characterized in that to increase the current density of the beam of fast electrons (as well as the concentration of ozone and / or other chemically active molecules) in the interelectrode and anode regions of the discharge by compensating for the possible decrease in the positive space charge ions (formed in the wake of the passage of fast electrons through the gas), leading to a reverse current in the gas, the geometry of the electrodes is chosen so that in the direction from the cathode to the anode the total cross section of the fast electron beams is constant and sufficient decreased significantly, for which, for example, they choose the appropriate ratio of the sizes and / or shapes of the anode and cathode (including the geometry of electrodes of spherical, cylindrical, etc. types), as well as the distance between them, or use the corresponding configuration for gradual narrowing of the fast electron beam external longitudinal magnetic field with increasing intensity towards the anode. 7. The method according to any one of claims 1, 3, 4, 6, characterized in that, for a sufficiently small τ _U limited by the characteristics of the high-voltage power supply used, for the delay in the development of the streamer volume discharge necessary in this case, increase τ _d in accordance with the condition (3), for which either two dielectric barriers are installed in the interelectrode gap (passing rather high-energy runaway electrons with practically no absorption, and absorbing almost completely slow electrons) - one close to the ano du, and the second at a distance of the order of (1 ÷ 2) · Δ from the cathode, or one thicker barrier at a distance of more than 2 · Δ from the cathode, on the reverse side of which an anode grid is deposited or attached. 8. The method according to any one of claims 4 to 6, characterized in that to increase the instantaneous power of the x-ray radiation that extends beyond the discharge zone as isotropically (a point source of x-ray radiation), a beam of fast electrons is generated from the maximum possible cathode area and sent to a metal a smaller anticathode (usually with a working part size of 1-2 mm), and to change the energy of quanta (wavelength) of X-ray radiation from the anticathode along with a change in the amplitude of the applied voltage (which is possible but, obviously, within the limits of the region of existence of this discharge, taking into account the nonlinear effect of voltage on the electron beam current, and therefore on the X-ray power), a change in the cathode – anticathode distance or the degree of concentration of the fast electron beam at this distance is used (which, as a rule , is much simpler than changing the voltage in the discharge gap), and also - placing in the interelectrode gap transparent dielectric barriers for sufficiently high-energy runaway electrons That transforms the energy of fast electrons in the beam and accordingly, - the distribution of energy bremsstrahlung radiation anticathode. 9. The method according to any one of claims 1 to 7, characterized in that, for a duration not sufficiently short τ _U to fulfill condition (1), a grounded electrode (located at a distance d from the high voltage) is disconnected from the ground, leaving it at a floating potential, and distance D from it is placed an additional electrode that is earthed, and the distance D and the shape of the additional electrode (sometimes also the shape of the electrode under the floating potential and the corresponding insulators) are chosen such that when voltage U is applied to the high voltage mu electrode first occurred discharge between the auxiliary electrode and the electrode to a floating potential, sharpening and Shortening the potential difference between the high voltage electrode and the electrode at a floating potential to the required value of τ _U, then at this potential difference occurred discharge under conditions satisfying the relationship (1). 10. The method according to any one of claims 1 to 8, characterized in that in order to increase the instantaneous power of the x-ray radiation outside the discharge zone, two or more opposing fast electron beams are generated, one of which has a start on the cathode with an area of the same order or smaller than the area of the anodes from which other beams begin, and all the beams converge in the region of positive space charge, which is generated by the first beam in the interelectrode gap, and for changing the quantum energy (wavelength) X-ray radiation (generated during the braking of electron beams in an electric field in the region of decrease in the spatial distribution of positive ions in the interelectrode gap) along with a change in the amplitude of the applied voltage (which is possible, obviously, within the limits limited by the region of existence of this discharge taking into account the nonlinear effect of voltage on the current electron beam, therefore, on the power of x-ray radiation) use a change in the distance of the cathode - anode or the degree of concentration of the beam of fast electrons at this distance (which, as a rule, is much simpler than changing the voltage in the discharge gap), as well as placing in the interelectrode gap dielectric barriers transparent to sufficiently high-energy runaway electrons, changing the energy of fast electrons in the beam, and, accordingly, the distribution of quantum energy bremsstrahlung in the interelectrode gap. 11. The method according to any one of claims 1 to 9, characterized in that to create a high concentration of ozone and nitrogen oxides (or other chemically active or excited atoms or molecules) in any closed air (gas) volume (for example, for excitation lasers based on chemically aggressive excimer media, or to obtain a high and controlled concentration of chemically active gases in confined volumes of the corresponding chemical reactions, having, in the general case, in this confined volume the gas composition that is different from the gas composition remains interelectrode gap), at least a part of the latter, having walls (windows) of a dielectric film partially transparent for sufficiently high-energy electrons, is placed in the interelectrode interval of the discharge satisfying condition (1), using fast electrons they generate chemically corresponding active or excited molecules to create the necessary concentrations in a pulse-periodic mode and, if necessary, pump the gas mixture from the area located inside the electrode gap into the remaining region of the closed gas volume, and all structural elements of the high-voltage generator are outside the range of chemically active and aggressive gases. 12. The method according to any one of claims 1 to 9, characterized in that for creating a high concentration of ozone and nitrogen oxides (or other chemically active or excited atoms or molecules) in any gas volume with access through a small (compared to the size electrodes) an inlet or located outside the window of a dielectric film (metal foil), at least partially transparent to electrons with a sufficiently high energy, a high-voltage (in the case of a single-electrode corona discharge) or a low-voltage discharge electrode with an operating mode You of type (1) are located in air as close as possible to the inlet or window of the aforementioned gas volume and produce a series of discharge pulses to create and maintain the necessary concentration of chemically active or excited atoms and molecules in this gas volume due to runaway electrons, UV and X-ray radiation penetrating into the specified gas volume through the inlet or window. 13. The method according to claim 9, characterized in that to control the beam (s) of fast electrons in the discharge gap, an additional several grounded or floating potential electrodes and dielectric barriers are installed that provide sequential acceleration and / or rotation of fast electron beams generated initially in one of the electrode regions of the discharge. 14. The method according to item 13, wherein in order to increase the duration and current density of the electron beam, additional electrodes are made using gas-tight films and / or foils and placed so that different gas pressure can be maintained in different sections of the interelectrode space, thereby providing optimal conditions for the generation of fast electrons in one of these gaps and the amplification of the current of the fast electron beam due to the avalanche multiplication of electrons in a gas in the following (next) duck (intervals). 15. The method according to 14, characterized in that the current density, as well as the energy spectrum of the electrons generated (propagated) in the gas-filled interelectrode gap, is changed, if necessary, continuously or periodically by changing the composition and pressure of the gas mixture enclosed in a hermetically separated section of the specified interelectrode gap, thus optimizing the above parameters of the beam for more effective one or another of its applications. 16. The method according to p. 15, characterized in that to regulate the energy spectrum of fast electrons obtained in the interelectrode gap or in the anode region of the discharge, dielectric barriers (at least partially transparent for runaway electrons with a sufficiently high energy) of various absorbing capacities are used, installed in various areas of the discharge gap in which it is necessary to regulate the energy spectrum of runaway electrons.

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