RU2306551C1 - Method for measuring changes of partial gas pressures in a powerful electro-vacuum device - Google Patents

Abstract

FIELD: electronic engineering, in particular, methods for manufacturing powerful electro-vacuum devices.

SUBSTANCE: method includes excitation of gases being analyzed due to impulse energetic influence on electrodes. Duration of impulse energetic influence is selected to be less than time of flight of any one of gases being analyzed towards manometer transformer, but more than minimal excitation time of any one of gases being analyzed. As manometer transformer, magnetic electro-discharge pump built into electro-vacuum device is used. In process of measurement, stepped curve of pump current growth is measured, number of steps k on the curve is determined. Using features of current growth, ascending series of all values t_n is determined - for time which passed since the moment of impulse energetic influence up to the middle of growth front of n step, where n=1,...,k. On basis of this information, mass number is determined for gases which escape into the volume of electro-vacuum device, as well as alternation of their partial pressures.

EFFECT: simplified method for measuring partial pressures of gases in a powerful electro-vacuum device, possible examination of processes, occurring in its vacuum space.

2 cl, 2 dwg, 1 tbl

Description

The invention relates to electronic equipment, and specifically to a technology for the manufacture of high-power electro-vacuum devices (EEC) and control of partial pressure changes in them. Such devices are expensive, and the problems of recording changes in the partial pressures of gases at different stages of their manufacture and operation are relevant, as they optimize the manufacturing process based on the measurements of gas pressures. This task is especially relevant for high-power EEC with a high probability of electrical breakdown, often leading to the failure of devices. The measurement of the change in partial pressures is necessary to determine the released gases in high-pressure EEC and analyze them by the following parameters: mass number, pressure change, and therefore, determination of the surface gas content.

A known method of measuring the change in partial pressure in a sealed EEC, where an omegatron is used as a mass spectrometric converter. This method is widely used to analyze phenomena that occur during the operation of an EEC, for example, an experimental diode [1], a kinescope [2], and a traveling wave lamp [3]. This method includes: attaching a mass spectrometric analyzer to the volume of the EEC before it is evacuated and taking partial pressure measurements at the stages of evacuation and training, if they are allowed to conduct electric and magnetic fields of the EEC itself or the equipment in which the EEC is placed. Partial pressure changes are measured by comparing these pressures before the moment of a pulsed energy effect on the EEC and after this action (for example, before and after a high-voltage electric breakdown).

The disadvantages of this method are the following:

- it is required to install a mass spectrometric gas analyzer in each EVP, which has large dimensions, often commensurate with the dimensions of the device. Basically, the presence of a gas analyzer is permissible only in experimental, but not commercially available, EVPs. The use of gas analyzers, as a rule, is limited to the stage of manufacture of EEC;

- powerful EECs, by their principle of operation, have their own strong electric and magnetic fields, which affect the operating mode of the gas analyzer, which complicates the process of measuring changes in gas pressures or can make these measurements impossible, for example, due to deviation of the electron and ion beams of the gas analyzer by magnetic fields EEC.

Closest to the proposed method (prototype) is a method for measuring changes in the partial pressures of gases by a time-of-flight mass spectrometer [4]. In this method, the proposed excitation of the analyzed gases to the state of the plasma created by the vacuum spark. Plasma ions reach the mass spectrometer in the sequence corresponding to their mass numbers, starting with the lowest (hydrogen), and then ions with large mass numbers (O ₂ ⁺ , Ni ⁺ , W ⁺ ) are recorded. The mass spectrometer shows the current value corresponding to the number of ions of the recorded mass. The magnitude of the change in current determines the change in the partial pressures of this gas in the test volume.

The disadvantages of the prototype are the following:

- this method can be used to solve research problems only at the stages of the technological process, allowing to carry out such measurements,

- the method cannot be applied during the operation of the EEC in the equipment due to restrictions on the overall performance of the EEC and the equipment,

- the requirement to use a specially installed transducer as part of the device makes the process of measuring changes in partial pressures more expensive.

An object of the present invention is to simplify the method of measuring partial pressures in a powerful electrovacuum device, as well as to enable the study of processes occurring in the vacuum volume of an EEC not only at the production stages, but also during its operation in the apparatus. These processes can be judged by the gas release in the device and the corresponding changes in pressure without the use of specially installed partial pressure gas analyzers that complicate the design of equipment and instruments.

A method is proposed for measuring changes in the partial pressures of gases in a powerful electrovacuum device, including the excitation of the analyzed gases by pulsed energy exposure to its electrodes, the sequential supply of gases to the gauge converter, the duration of the pulsed energy exposure is less than the time of flight of any of the analyzed gases to the gauge converter, but longer than the minimum excitation time of any of the analyzed gases, as the manometric converter uses a magnetic electric discharge pump built into the electric vacuum device, during the measurement process, take the stepwise curve of the pump current rise to its maximum value from the moment of pulsed energy exposure, determine the number of steps k on the pump current rise curve, determine the increasing sequence of all time values from the current rise curve t _n , where n = 1, ..., k from the initial moment of time of the pulsed energy exposure to the middle of the front nthania of the nth stage, then they compose the matrix of relations m _s / m _i , where m _s are the mass numbers of the list of all gases, the release of which is possible in the vacuum volume of the device under pulsed energy exposure in their increasing sequence along the vertical of the matrix, where s = 1, ..., j, and j is the amount of all gases, the evolution of which is possible in the vacuum volume of the device, am _i are the mass numbers of this list of gases in their ascending order along the horizontal of the matrix, where i = 1, ..., j, then along the measured values of t _n calculate a sequence of values n _n = (t _n / t _i ) ² , where n = 1, ..., k and compare it in turn with the sequence of values in each of the columns of the matrix, determine the column of the matrix, which with the smallest error coincides with the sequence of values of n _n , from it determine the list of gases released in the device, assign on the current rise curve the belonging of each stage n to one of these gases, then the changes in the partial pressures ΔP _{n of} each gas are calculated by the formula:

где

Where

K - pump sensitivity [A / Pa],

R _n - the relative sensitivity of the pump to gas assigned to the n-th stage of the curve of the rise of the pump current,

ΔI _n is the change in the saturation current from its average value at the n-th stage of the current rise curve to its average value at the n-1st stage of this curve [A].

A method is proposed for measuring changes in the partial pressures of gases in a powerful electrovacuum device, including the excitation of the analyzed gases by means of a pulsed energy effect on its electrodes, the sequential delivery of gases to a gauge converter, in which the duration of the pulsed energy effect is chosen less than the time of flight of any of the analyzed gases to the gauge transducer, but longer than the minimum excitation time of any of the analyzed gases, as a manometric converter, a magnetic electric discharge pump built into the electric vacuum device is used; during the measurement process, take the stepwise curve of the pump current rising to its maximum value from the moment of pulsed energy exposure, determine the number of steps k on the pump current rising curve, using the current rising curve determine the increasing sequence of all values t _n time, where n = 1, ..., k from the initial time of pulse exposure energy to mid Rhondda rise n-th stage, then in a matrix relationship m _s / m _i, where m _s - mass numbers list all gases, the allocation of which may in vacuum device at pulse energy impact of their increasing horizontal sequence matrix, where s = 1 , ..., j, and j is the amount of all gases that can be released in the vacuum volume of the device, am _i are the mass numbers of this list of gases in their increasing sequence along the vertical of the matrix, where i = 1, ..., j, then from the measured values t _n is calculated posledovatelnos v variables _{n n = (t n / t} i) ² where n = 1, ..., k, and compare it in turn with sequence values in each of the rows of m _s / m _i, define the matrix row, which with the smallest error coincides with the sequence of values of n _n , from it determine the list of gases released in the device, assign the membership of each stage n to one of these gases on the current rise curve, then change the partial pressure ΔP _{n of} each gas by the formula:

где

Where

K - pump sensitivity [A / Pa],

R _n - the relative sensitivity of the pump to gas assigned to the n-th stage of the curve of the rise of the pump current,

ΔI _n is the change in the saturation current from its average value at the n-th stage of the current rise curve to its average value at the n-1st stage of this curve [A].

The technical result is achieved by recording the peculiarities of the increase in the current front of the MEN after pulsed energy exposure to the surface of the sealed instrument, which is carried out, in particular, by the development of electric breakdown in the EEC. The technical result becomes possible due to the factor of separation of gas ions by mass numbers in the drift space and the dependence of gas velocities on the mass number.

The proposed method includes the excitation of the analyzed gases on the surfaces of the electrodes by pulsed energy exposure, for example, when an electrical breakdown occurs between the electrodes, as well as the sequential flow of gases into the magnetic electric discharge pump. The sequential flow of gases into the pump provides the opportunity at the time of their arrival to measure changes in their partial pressures.

An essential point in the proposed method are the conditions of pulsed energy exposure. This effect ensures the release of all gases from the surface of the electrodes at the same time.

The duration of the energy exposure should be longer than the time of excitation of the analyzed gases on the surfaces of the electrodes of the EEC, since otherwise the energy of the impact is transmitted only partially, which may not be enough to release gases into the vacuum volume of the device. It is known that this time is 10 ^-9 -10 ^-10 sec [5].

The exposure time should be less than the time of flight of the analyzed gases to the pump in order to ensure optimal conditions for the flow of gases into the pump and reduce errors. Calculations carried out in accordance with the kinetic theory of gases show that the time of flight of gases is 10 ^-4 -10 ^-5 sec. Therefore, the time of pulsed energy exposure should be from 10 ^-8 to 10 ^-6 seconds, taking into account the safety factor for the upper and lower boundary of the time of flight of gases.

Mass separation is carried out after the development of electrical breakdown in the process of plasma propagation to the pump. During the development of breakdown, ions of different masses acquire the same energy E, but different speeds in accordance with the equation:

m is the mass of the ion,

v is the ion velocity.

Subject to the above conditions, the gases are sequentially supplied to the pump after deionization in the form of atoms and molecules, taking into account the fact that all of them, as a result of pulsed energy exposure, acquire the same amount of energy.

Since a sequential flow of gases into the pump is ensured, the measured pressure changes can be carried out by a pump designed to measure the total pressure. As such, a magnetic electric discharge pump was chosen, which is an integral part of a high-voltage high-voltage electric circuit, which allows measurements of the pump current, and therefore the gas pressure in the electric circuit, at almost any stage of the technological process or during the operation of the electric circuit.

Since gases acquire different speeds after pulsed energy exposure in accordance with their mass numbers, then after they move towards the pump, they will not come into it at the same time. Consequently, the change in the pump current with the arrival of gases will not be linear, but stepwise. The lighter gases will be the first in the pump, and the heaviest gases will be the last to reach the pump. Therefore, a stepwise curve of the pump current rise is taken.

The number of steps k of the increase in the pump current as the gases arrive will correspond to the number of gases having different mass numbers, and the steps will be arranged in increasing mass numbers of the corresponding gases. The later the step appears, the greater the mass number and molecular weight of the gas that has come to the pump.

To determine the flight time of each specific gas t _n , where n = 1, ..., k from the moment of pulsed energy exposure to its arrival in the pump, it is necessary to measure the time corresponding to the middle of the front of the rise of the step on the current rise curve. The choice of the middle of the front is due to transients at the beginning and end of the front.

If we compare the conditions for the passage of various gases to the pump, then according to formula (1), a relation is obtained that relates the mass numbers of gases corresponding to different steps of the curve of the rise of the pump current and their transit times to the pump:

where m _n is the mass number of the n-th gas,

m _i is the mass number of the i-th gas,

n = 1, ..., k, i = 1, ..., k, t _n and t _i are the corresponding times when these gases entered the pump.

This ratio is taken as the basis for determining the affiliation of each stage to a specific mass number of the analyzed gas. Therefore, a sequence of increasing quantities n _n = (tn / t _i ) ^{2 is} calculated.

Since the mass numbers of gases entering the pump are unknown, but their ratios for the time of flight to the pump from formula (2) are known, a list of all possible gases that could appear in the pump after an impulse energy exposure is compiled.

According to formula (2), an increasing sequence of relations of times of gas passage to a pump can be compared with an increasing sequence of relations of mass numbers of these gases. Therefore, a matrix of ratios m _s / m _{i of} mass numbers m _{s of a} compiled list of all gases that may appear in the device in their ascending order to mass numbers m _{i of} this list of gases also in their ascending sequence is compiled.

The sequence n _{n is} compared in turn with the sequence of values in each of the columns of the matrix. There will always be a column in the matrix in which sequence matches are most likely. Therefore, by the coincidence of the sequences of values in the column and in the matrix with the smallest error, the matrix column is determined in which the relation m _s / m _i = (t _n / t _i ) ² is observed, where the mass numbers of gases in the theoretical column of the matrix correspond to the mass numbers of gases, in reality stand out in the device. The found mass numbers of gases are assigned on the curve of the pump current rise the belonging of each stage of this curve to a specific gas in accordance with their values in the matrix. If you change the columns with rows in the matrix and respectively compare the matrix data with the ratios of measured times by rows rather than columns, then the essence of the calculations and measurements will not undergo changes that affect the final result.

Since the pump current is directly proportional to the pressure, to calculate the partial pressure of any gas, we find the change in the current value at each stage of the curve of the pump current rise, and therefore the change in the pressure value of this gas. In this case, the change in the partial pressure of the nth gas is calculated by the formula:

K - pump sensitivity [A / Pa], which is its individual characteristic, which is given in the technical specifications for the pump;

R _n is the relative sensitivity of the pump to the nth gas, which is determined from the information source [6],

ΔI _n is the change in the saturation current from its average value at the n-th stage of the current rise curve to its average value at the n-1st stage of this curve [A].

The measurement of the change in current between the midpoints of the stages is selected based on the condition of the minimum error of this measurement, and the coefficient R _n is an individual quantity for each specific gas with respect to air or another gas, according to which the pump was calibrated, it takes into account the coefficient K and the individual characteristics of the pump as pressure gauge for measuring pressure.

The invention is illustrated by drawings, where Fig. 1 shows the dependence of the increase in pump current I (μA) on time t (taken in relative units to the time of the first stage), while the time t = 0 corresponds to the time moment of the pulsed energy effect. Figure 2 shows the matrix of the ratio m _s / m _i in the form of a table, in the cells of which the relations m _s / m _i are presented, and the masses are presented in relative units.

The achievement of the technical result is based on the noticed and investigated stepwise nature of the change in the leading edge of the current pulse of the MEN directly after the development of the breakdown in the EEC. Analysis of the leading edge of the current led to the conclusion that the nature of the pump current pulse correlates with the mass numbers of gases released into the volume of the EEC.

An example of the method is the measurement of partial pressure changes in a powerful sealed EVP. This method was used to measure changes in partial pressures in a sealed off powerful klystron at the stage of high-voltage training of the device. Usually powerful devices of this type incorporate a built-in magnetic electric discharge pump. The measurements were carried out in the process of high-voltage training using a pump type NEM-2-1 with a nominal pumping speed of 1 l / s. The pressure of the residual gases in the device before the start of the measurements was 5 · 10 ^-6 Pa.

The development time of electrical breakdown between the electrodes of the device is 10 ^-7 sec. The movement time of the front of the first of the gases released during the breakdown is 10 ^-4 seconds. The average transportation time of any of the gases released during the breakdown should be, as calculations show, 10 ^-3 -10 ^-5 seconds in a device about 0.5 meters long. This is confirmed by special measurements of the velocity of gases released as a result of breakdown [7]. Therefore, in order to reliably record the fact of changing the pump current, a shorter period of time is required, at least less than 10 ^-5 seconds, which ensures a satisfactory separation of gases by their masses.

In the process of taking the stepwise curve of the pump current rise, five steps were found (see Fig. 1), k = 5. On the graph (figure 1) t ₁ ÷ t ₅ - time points corresponding to the midpoints of the fronts of steps, counting from the first to the fifth, from left to right the abscissa axis. For clarity, the times are shown in relative units.

On the curve of the increase in the pump current, all values of time t _{n are} determined, of which an increasing sequence is composed [1; 2.85; 2.99; 2.73; 4.68] and then composed sequence n _n = (t _n / t _i ) ² equal to [1; 8.1; 8.95; 13.9; 21.9].

Figure 2 presents the matrix in the form of relations m _s / m _i and gives the corresponding mass numbers m _s and m _i . The sequence n _{n was} compared with each column of the matrix in the form of a table of Figure 2 and the first column was selected. As a result of the comparison, the deviations from the matrix values were minimal for this column.

In the selected column, in order of increasing mass numbers, the following gases are contained: hydrogen, methane, water, nitrogen / carbon monoxide, carbon dioxide [H ₂ ; CH ₄ ; H ₂ O; N ₂ / CO; CO ₂ ].

. Значения R_n из [7]. Величина К выбрана из технических условий на этот насос и составляет 190000 мкА/Па.From the curve of current rise, we determine the magnitude of the change in currents at each stage and the change in partial pressures according to the formula

. The values of R _n from [7]. The value of K is selected from the technical conditions for this pump and is 190,000 μA / Pa.

For convenience, the resulting and calculated data are tabulated

Gas formula H ₂ CH ₄ H ₂ O N ₂ / CO CO ₂ ΔI _k , μA 13 24 16 12.5 95.5 R _n , rel. 0.43 1,5 1.15 1,0 1.3 K · R _n , μA / Pa 8.12510 ⁴ 28.2 · 10 ^-4 21.6210 ⁴ 18.67 · 10 ^-4 24.710 ⁴ ΔP _k , Pa 1.6 · 10 ^-4 0.85 · 10 ^-4 0.74 · 10 ^-4 0.67 · 10 ^-4 3.87 · 10 ^-4

As can be seen from the table, the maximum gas evolution into the device during the breakdown is given by carbon dioxide and hydrogen, and on the basis of these data it is possible to decide on the refinement of the technological process of manufacturing this EVP.

Thus, the technical result of the present invention is to obtain additional information about the processes of gas evolution and measuring changes in the partial pressures of gases released in the operation modes of high-power electronic components without using any special devices that complicate the design of the devices.

Information sources

1. Walk, Watson, Wallace. "The study of the composition of the residual gases in laboratory diodes with oxide cathodes using an omegatron", Sat. "Technique of electronic lamps", trans. from English / Ed. B.P. Nikonova. - M .: IL., 1963, p.303-312.

2. J. Van der Waal. "Residual gases in picture tubes", sb. "Residual gases in electron tubes", trans. from English / Ed. G.D. Glebova, Moscow: Energy, 1967, p. 237-243.

3. Hake R.A. and Needle, J. C. "Residual Gases in Traveling Wave Lamps," collection of articles. "Residual gases in electron tubes", trans. from English / Ed. G.D. Glebova, Moscow: Energy, 1967, p. 255-259.

4. Slivkov I.N., Mikhailov V.I., Sidorov N.I., Nastyukha A.I. "Electrical breakdown and discharge in a vacuum", M., Atomizdat, 1966, p.207 [prototype].

5. Kaganov I.L. "Ionic devices", Moscow: Energy, 1972, p.19.

6. Rozanov L.N. "Vacuum Technology", Moscow: Higher School, 1990, p.145-151.

7. Latham R. "Vacuum insulation of high voltage installations", trans. from English, Moscow: Energoatomizdat, 1985, p. 81, 101.

Claims (4)

1. The method of measuring changes in the partial pressures of gases in a powerful electrovacuum device, including the excitation of the analyzed gases by pulsed energy exposure to its electrodes, the sequential flow of gases to the pressure gauge, characterized in that the duration of the pulsed energy exposure is chosen less than the flight time of any of the analyzed gases to the pressure gauge, but longer than the minimum excitation time of any of the analyzed gas s, a magnetic electric discharge pump built into the electric vacuum device is used as a manometric converter; during the measurement process, a stepwise curve of the pump current rise to its maximum value from the moment of pulse energy exposure is taken, the number of steps k on the pump current rise curve and an increasing sequence of all values of t _n - time elapsed from the moment of pulsed energy exposure to the middle of the rise front of the n-th stage, where n = 1, ..., k, then vlyayut matrix relationship m _s / m _i, where m _s - mass numbers list all gases, allocation is possible in unit volume of a vacuum during pulsed energy impact in their ascending sequence vertically matrix, where s = 1, ..., j, wherein j is the amount of all gases whose evolution is possible in the vacuum volume of the device, am _i are the mass numbers of this list of gases in their ascending order along the horizontal of the matrix, where i = 1, ..., j, then the sequence of quantities n _n = (t _n / t _i ) ² , where n = 1, ..., k and compare it with the sequence of the values in each of the columns of the matrix, determine the column of the matrix, which with the smallest error coincides with the sequence of values of n _n , from it determine the list of gases released in the device, assign the belonging of each stage n to one of these gases on the curve of the current rise, then calculate the changes partial pressures ΔP _{n of} each gas according to the formula ΔP _n = ΔI _n / (K · R _n ), where K is the sensitivity of the pump, A / Pa; R _n is the relative sensitivity of the pump to the gas assigned to the n-th stage of the curve of the rise of the pump current; ΔI _n is the change in the saturation current from its average value at the n-th stage of the current rise curve to its average value at the n-1st stage of this curve, A. 2. The method according to claim 1, characterized in that the pulsed energy effect is carried out by electrical breakdown between the surfaces of the device. 3. A method of measuring changes in the partial pressures of gases in a powerful electrovacuum device, including the excitation of the analyzed gases by pulsed energy exposure to its electrodes, the sequential flow of gases to a pressure gauge, characterized in that the duration of the pulsed energy exposure is less than the flight time of any of the analyzed gases to the pressure gauge, but longer than the minimum excitation time of any of the analyzed gas s, a magnetic electric discharge pump built into the electric vacuum device is used as a manometric converter; during the measurement process, a stepwise curve of the pump current rise to its maximum value from the moment of pulse energy exposure is taken, the number of steps k on the pump current rise curve and an increasing sequence of all values of t _n - time elapsed from the moment of pulsed energy exposure to the middle of the rise front of the n-th stage, where n = 1, ..., k, then vlyayut matrix relationship m _s / m _i, where m _s - mass numbers list all gases, which selection is possible in vacuum device with pulsed energy in the impact of their increasing horizontal sequence of the matrix, where s = 1, ..., j, wherein j is the amount of all gases whose evolution is possible in the vacuum volume of the device, am _i are the mass numbers of this list of gases in their increasing sequence along the vertical of the matrix, where i = 1, ..., j, then the sequence of quantities n _n = (t _n / t _i ) ² , where n = 1, ..., k and compare it with the sequence by the values in each of the rows of the matrix, determine the row of the matrix, which with the smallest error coincides with the sequence of values of n _n , from it determine the list of gases released in the device, assign the belonging of each stage n to one of these gases on the current rise curve, then calculate the changes partial pressures ΔP _{n of} each gas according to the formula ΔP _n = ΔI _n / (K · R _n ), where K is the sensitivity of the pump, A / Pa; R _n is the relative sensitivity of the pump to the gas assigned to the n-th stage of the curve of the rise of the pump current; ΔI _n is the change in the saturation current from its average value at the n-th stage of the current rise curve to its average value at the n-1st stage of this curve, A. 4. The method according to claim 2, characterized in that the pulsed energy effect is carried out by electrical breakdown between the surfaces of the device.

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