Accelerated test of plasma engine cathodes and device to this end

FIELD: engines and pumps.

SUBSTANCE: invention can be used for tests of plasma source cathodes or those for high-current plasma engines. Proposed method comprises cathode independent fire tests. Here, cathode is switched on many times. Cathode basic degradation parameters are measured and tests are conducted at forced operating conditions. Tests are divided into steps. At every step, one of cathode degradation factors is augmented and cathode is simultaneously subjected to all other degradation factors under operating conditions. Every degradation factor is augmented at least one time.

EFFECT: accelerated test procedure, possibility to analyse the effects of every degradation factor to cathode life.

7 cl, 4 dwg

 

The group of inventions relates to the field of electrical propulsion engines (ERE), namely tungsten-bereavem the cathodes, which are widely used in various plasma thrusters (hall, ion). If necessary, it can also be used in various fields of technology, including related areas, for example, when testing cathodes for plasma sources or cathodes for high current plasma thrusters.

The problem of ensuring that the resource is relevant for a variety of devices used in various fields of technology. For cathodes, which is one of the main structural elements of most families, this problem becomes especially acute.

Required resource of modern families and their cathodes are tens of thousands of hours [A.I. Morozov, "Introduction to plasmadynamic", M: "FIZMATLIT", 2006; O.A. Gorshkov, V.A. Muravlev, A.A., shagaida "Hall and ion plasma engines for spacecraft" / Ed. by A.S. korotyeyeva "engineering", 2008]. From modern ERD requires not only a long working life in create mode of traction, but also providing multiple inclusions. So from their cathodes also requires a large number of inclusions, often calculated by the tens of thousands. In order to make the resource test is of at least one instance of the cathode with such resource characteristics on the ground, will need more than one year. This will involve expensive vacuum unit will be spent significant resources will require considerable labor costs of qualified personnel. It should also be noted that as to confirm the reliability of the produced cathode, and to study their resource characteristics necessary testing multiple instances of the cathode.

This raises the need to find other ways to confirm the resource characteristics of the cathodes. One such way is the use of methods of accelerated testing. Reducing the time life test avoids the huge costs when conducting full-scale fatigue tests. It should be noted that abroad until recently was dominated by the following approach when assessing resource characteristics of cathodes ERD [Baranov. VP, A. I. Vasin, V.A. Petrosov "Problems of accelerated tests of electric propulsion thrusters", proceedings of CT, issue 3 (131), 1991; Timoti R. Sarver-Verhey "Destructive evaluation of a xenon hollow cathode after a 28,000 hour life test" AJAA-98-3482]. Conducted single ground demonstration test one or the other of the cathode in the nominal operating mode, the resource of which exceeded the required resource. Positive results of such tests gave hope that a similar cathodes will have the same character what sticks. However, such tests are not able to confirm the reliability specifications issued by the manufacturer of the cathodes.

It is no coincidence that in practice many of the hall and ion engine accelerator the engine compartment is equipped with not one, but two cathodes, the first of which is the working cathode, the second backup [Arhipov Century, A. Bober, Gnizdor R., K. Kozubsky, N. Maslennikov, Pridannikov S. "Results of 7000-hour SPT-100 life test" the 24-th International Electric Propulsion Conference, IEPC-95-39, Moskow (Russia), 1995; Akimov V.N., O.A.Gorshkov, A.I.Vasin, V.N.Shutov et al. "Development of KM-5 hall effect thruster and it flight testing onboard a GEO spacecraft "Express-A4", Progress in Propulsion Physics, EUCASS book series, Ed. Wu L.De Luca, Torus Press, vol.1, 2009, p.411-424].

Thus, the problem of developing efficient methods for accelerated testing of the cathodes is very important.

However, to solve the problem quite difficult. Primarily, this is due to the fact that to date has not yet developed a full physical-mathematical model of changes of basic parameters of degradation depending on the time of the cathodes. It is not possible to create predictive models of the resource on the basis of which it would be for a limited time testing to make a reliable conclusion about the resource of one or the other of the cathode ["HOWTO. Reliability in engineering. Accelerated testing. General provisions", RD 50-424-83, M.: Publishing house of standards, 1984]. Getting the same item is leannah experimental data on resource characteristics of certain cathodes requires a very long test. The methods of non-destructive testing applied to the tungsten-bereavem the cathodes are weak, due to the complexity of the inspection the main working area of the cathode and its emitter is in the process of testing. Access to the emitter in the tungsten-barium chloride diafragmirovanija cathodes (i.e. cathodes are usually used in the composition of the ion and hall of engines) is virtually absent. Typically, the emitter may be subjected to a detailed analysis only after disassembly of the cathode on the constituent elements without the possibility of its subsequent recovery.

Thus, the creation of an effective method of accelerated testing tungsten-barium chloride cathodes is not only relevant, but also challenging. If to speak about a reduction time of the accelerated test cathodes compared to the time full-scale testing (about 10 times), then the basic principle of acceleration should recognize the principle of forcing test mode and not sealing principle working cycles, reduce downtime, eliminate downtime, etc. ["HOWTO. Reliability in engineering. Accelerated testing. General provisions", RD 50-424-83, M.: standards Publishing house, 1984], that is, the principle of acceleration tests due to the intensification of the processes that are causing degradati the cathodes. In the result there is a need for a comprehensive account of the fundamental physical phenomena, leading to degradation of the cathode when it is extended operation, i.e. when conducting accelerated tests should take into account the simultaneous effect of all the underlying factors of degradation, which is especially important for tungsten-barium chloride cathodes having not one, but a few basic factors of degradation (see below).

There is a method of accelerated life tests of the cathode-compensator hall motors [Grishin S.D., Kashenkov V., Klimenko, G., Kovalev V., Lyapin A., M. Chursin "endurance testing of cathode-compensator on the start-up mode and the ways of their acceleration", proceedings of CT, issue 3 (131), 1991], in which as a basic factor of degradation were taken into account only starting erosion emitter side of the cathode. The main idea of this method lies not in the direct forcing mode preheat mode the start of heating or heater operation of the arc discharge, and reduce the time of cooling of the cathode after ignition while maintaining a fixed time of the arc discharge, the time of operation of the cathode, during which there is a stabilization of the temperature of the cathode. In this way also is some crossing of the mode of operation of the cathode due to the fact that there is the full cooling and each of the new duty cycle of the cathode starts from the start of heating at elevated temperature, the emitter side of the cathode.

The above method allows to reduce the time and resource tests cathode significant when the required number of runs. However, the acceleration factor when using this method is small, as the full cycle starting cathode while conducting his life tests on the number of inclusions is comparable to the time it start warming up and by the time the arc discharge. At least the magnitude of the acceleration factor when using this method, significantly less than 10. In addition, it takes into account only the influence of one factor degradation, namely the factor of erosion of the emitter part of the cathode.

It should be noted that in the practice of conducting life tests of the cathodes on the number of inclusions in this way it is implemented. The time of cooling the emitter side of the cathodes tested in vacuum, to the initial (room) temperature is in the order of hours. Therefore, when conducting fatigue tests cathodes on the number of inclusions are not getting the cathode to cool down, otherwise the total time the resource test cathodes will become excessively large.

The closest technical solution to the claimed combination of features is the way for accelerated life test of cathode plasma engines and device for its implementation [Kashenkov VI, Kovalev Century, the., Lyapin A.A., Pekhterev SV, Chursin MM "Theoretical background of accelerated life tests of the cathode-compensator in forced mode", Proc. CT, issue 3 (131), 1991], which consists in the fact that when conducting Autonomous fire tests cathode exercise forcing wear the emitter side of the cathode by increasing the discharge current and the replacement of the original plasma-forming gas (usually gas Xe) model that has a higher ionization potential. During the tests provide measurements of the basic parameters of the degradation of the cathode.

When using this method increases the temperature of the emitter, the flux and energy of ions bombarding the emitter, resulting in speed increases as thermal evaporation and cathode sputtering. This causes the intensification of wear on the emitter side of the cathode.

The increase in emitter temperature and the flux density of the energy of ions bombarding the emitter, is achieved at the same time as increasing the discharge current, and using a model gas with a higher ionization potential, i.e. in this case is a complex crossing of two main factors of degradation - material vaporization at high temperature and erosion when exposed to the ion bombardment.

However, this method is not without disadvantages. This method is primarily applicable to the hexaboride-lanthanum to the cathodes, in which basic physical phenomena, leading to degradation of the cathode in the process of resource, i.e. the basic degradation factors are the ablation of material from the emitter side of the cathode (or more precisely, the erosion of the outlet aperture of the emitter and the output part of emitir), as well as the diffusion of the material of the body, covering the outer surface of the emitter to the emitter through a protective "barrier" layer, leading to chemical interaction of the emitter with products diffusion [V.I. Baranov, A. I. Vasin, V.A. Petrosov "Model erosion hollow cathode emitter for projecting resource on accelerated testing", Proc. of CT, issue 3 (131), 1991]. Such attention to the hexaboride-lanthanum to the cathodes is not accidental, it is because until recently in domestic practice, the most widely used hexaboride-lanthanum cathodes design Bureau "Fakel" [5], while abroad intensively developed and continue to evolve tungsten-barium cathodes [Timoti R. Sarver-Verhey "Destructive evaluation of a xenon hollow cathode after a 28,000 hour life test" AJAA-98-3482; Akimov V.N., O.A.Gorshkov, A.I.Vasin, V.N.Shutov et al. "Development of KM-5 hall effect thruster and it flight testing onboard a GEO spacecraft "Express-A4", Progress in Propulsion Physics, EUCASS book series, Ed. Wu L.De Luca, Torus Press, vol.1, 2009, p.411-424].

The analysis shows that based on the results of long term testing of tungsten-barium chloride cathodes (see, for example, [Tmoti R. Sarver-Verhey "Destructive evaluation of a xenon hollow cathode after a 28,000 hour life test" AJAA-98-3482]) these cathodes have a different list of basic factors of degradation, in which the ablation of material from the emitter side of the cathode is not the only factor degradation. It includes the following factors:

ash barium from the scope of the emitter, accompanied by its depletion on the working surface of the emitter, which leads to deterioration of its emission properties,

- poisoning the emitter of different substances, coming to him from the environment, including in the form of impurities from the working fluid during operation of the cathode (the main toxic substance is oxygen [Timoti R. Sarver-Verhey "Destructive evaluation of a xenon hollow cathode after a 28,000 hour life test" AJAA-98-3482]),

ash material aperture of the emitter due to erosion, which leads to changes in the geometry of the flow part, and deterioration of the conditions of arcing and ignition of the discharge cathode.

Basic parameters of the degradation of the tungsten-barium chloride cathodes, i.e. the parameters measured during fatigue tests of cathodes and indicative of their resource characteristics are as follows:

the discharge voltage between the cathode and the anode, which is determined when firing tests of the cathode in a nominal mode (current discharge and flow rate of the working fluid),

- the temperature of the emitter during operation of the cathode,

- temperature emit the EPA when starting the ignition of the discharge,

the time of the start of heating of the cathode.

The method of accelerated testing in accordance with [Kashenkov I., Kovalev, VN, Lyapin A.A., Pekhterev SV, Chursin MM "Theoretical background of accelerated life tests of the cathode-compensator in forced mode", Proc. CT, issue 3 (131), 1991] does not take into account all factors of the degradation characteristic of the tungsten-barium chloride cathodes, so it may not be fully applicable to these cathodes.

In addition, as mentioned in [Kashenkov I., Kovalev, VN, Lyapin A.A., Pekhterev SV, Chursin MM "Theoretical background of accelerated life tests of the cathode-compensator in forced mode", Proc. CT, issue 3 (131), 1991], the development of this method has not been completed and a final conclusion about its use when conducting accelerated tests even hexaboride-lanthanum cathodes require further experimental studies. In addition, this method has not found wide use in resource testing cathodes.

You should also add that this method does not allow to investigate in detail the effect of each factor degradation to the resource of the cathode, since it is simultaneously forcing all major degradation factors. Increasing the discharge current and the use of the model of the working fluid in the hexaboride-lanthanum is attach leads simultaneously to the intensification of erosion and increase the temperature of the emitter, which in turn causes an increase in the rate of evaporation of the emitter and its diaphragm and intensifies the diffusion of the material of the body towards the emitter through a protective "barrier" layer. In this case, when the failure of the cathode will be very difficult to identify the factor that led to the failure.

If we apply this method to the tungsten-bereavem the cathodes, it will be carried out simultaneously forcing two factors (the ablation of the material of the diaphragm of the emitter due to erosion and acceleration of the release of barium from the scope of the emitter by increasing temperature). This can cause significant distortion of the physical processes that lead to distinct processes during the operational mode of the cathode, from processes in the forced mode of life test. For example, an increase in the discharge current can not only result in higher operating temperature of the emitter, but also increase the depth of penetration of the bit in its internal cavity, and also to increase the voltage of the discharge at the cathode, which is not typical for the operational mode of the cathode. Replacement of the working fluid on the model gas can not only change the depth of penetration of the discharge into the internal cavity of the emitter, but also due to changes in the conditions of the ion bombardment can lead to such changes in the surface properties of the emitter of the aperture of the emitter, which is not peculiar to changes in the operational mode of the cathode. That is, the use of this method may result in significant distortion of the physical processes in the operational mode of the cathode. The result can be pereformyrovanye cathode. If you apply a small increase in the discharge current in comparison with the nominal and use gas with parameters close to the main working body of such cathodes (xenon gas), it will lead to low acceleration.

The technical challenge which sent a group of inventions is the implementation of a comprehensive consideration of the impact of all the underlying factors of degradation of the cathode when conducting accelerated life tests, a significant reduction of time and resource tests cathode and enabling study of the impact of each factor on resource degradation characteristics of the cathode.

This object is achieved in that conduct Autonomous fire tests cathode, perform multiple listing it, measure the basic parameters of the degradation test in the forced mode of operation of the cathode, while the test is divided into stages, with each stage producing forcing one of the factors of degradation while at the same time is exposed to the cathode of all other factors of degradation in operational mode, and forcing each of the factors of degradation carried out at least once.

However, tests can be carried out in such a way that the stages are grouped in several parts, the number of stages being equal to the number of the main factors of degradation, and in each of these stages produce a forcing factor degradation, different from all the others.

Tests can be carried out in such a way that after completion of each phase of testing produce at least one inclusion and the work of the cathode on the primary operating mode without forcing any degradation factor. The tests can be carried out also in such a way that the crossing of the degradation factor, implying the poisoning of the emitter, is produced by adding to a working body used in the operation tungsten-barium cathode poisoning the cathode impurities.

The tests can be carried out also in such a way that the crossing of the degradation factor, consisting in the release of barium from the tungsten - barium cathode, produced by overheating its emitter through the inclusion of starting the heater in the mode of lower power than the power start heating the tungsten-barium cathode.

The tests can be carried out also in such a way that the crossing of the degradation factor, comprising the I in erosion emitter node tungsten-barium cathode, produced by the exceptions to the timeline resource test tungsten-barium cathode cycle cooling its emitter node below the temperature at which is provided an ignition discharge tungsten-barium cathode.

Device for conducting accelerated testing of cathode plasma engines includes a vacuum chamber with a pump, the delivery system of the working fluid, the power system including a source start heating the cathode Assembly is installed in front of the cathode, the anode, a system for measuring the basic parameters of degradation. The device is equipped with an additional supply system, which is the working body with the addition of him poisoning the cathode impurities, and the output of the additional system flow through the valve is connected to the output of the main supply system and the power source starter heater is equipped with a switch mode continuous operation with less power than the power of starting heating of the cathode.

The invention is illustrated the accompanying drawings. Figure 1 presents the sequence diagram for carrying out part of the accelerated life test, the tungsten-barium cathode that includes several stages of testing, figure 2 - General program of accelerated life tests of the cathode. Figure 3 presents the procedure of stage resource is spitoni cathode during the crossing of the factor of erosion of its emitter node. Figure 4 shows the experimental setup for conducting Autonomous fire tests tungsten-barium cathode.

The method of accelerated testing of cathode plasma engines is that conduct Autonomous fire tests cathode, which provide measurements of the basic parameters of degradation, as well as produce the forcing factors of degradation. The test is divided into stages, which are produced alternately forcing one of the factors of degradation under the simultaneous effect on the cathode of all other factors of degradation in operational mode.

That is the main idea of the method is that the comprehensive performance impact of all the major degradation factors acting on the cathode in the course of its long use in operational mode, replace the crossing of one of the degradation factors at the same time without forcing all other degradation factors and consistently implement forcing first one degradation factor, then another and so on until the last.

Phasing under the simultaneous influence of all factors of degradation of the characteristic of the cathode, makes it possible to consider all these factors in the process of conducting resource IP is itani cathode. While forcing only one of the factors of degradation at each stage allows the accelerated life test on this factor and at the same time allows a separate detailed study of the impact of this factor on the resource characteristics of the cathode. Because forcing each of the factors of degradation carried out at least once, then provide the forcing of all degradation factors, which allows for a consistent acceleration tests on all the factors of degradation of the cathode.

You can group stages in several parts, the number of stages being equal to the number of the main factors of degradation. In each stage one should be made part of the crossing of the degradation factor, different from all the others (see Fig. 1). Thus, each part will contain a single step of forcing each factor degradation and these parts will be several that will provide forcing each degradation factor a few times in the process of accelerated life tests. This will allow for a full accounting of the impact of all factors of degradation on the basic parameters of degradation and, accordingly, the life characteristics of the cathode. In addition, split testing allows more detail to conduct research on the impact of each the actor degradation on the resource characteristics of the cathode.

The more the number of such parts in the total program of accelerated life tests tungsten-barium chloride cathodes (see figure 2), the better to simulate the actual process of degradation of such cathodes in their field of operation. On the other hand, the total number of these parts should not be too large, it should also be determined on the basis of stand conditions for accelerated testing. If the increase in the number of these parts leads to a noticeable increase in the total time of testing that may be associated including with the necessary pauses between stages, then their number should be limited.

After the completion of each phase of testing can be performed, at least one switching-on and operation tungsten-barium cathode on the primary operating mode without forcing any degradation factor to assess the degree of change in the underlying parameters of the degradation that characterizes the efficiency of the tungsten-barium cathode in operational mode (see figure 1). This will allow to assess the degree of degradation of the tungsten-barium cathode at each stage of testing, to identify the main factor of its degradation in the test period, to take timely measures to improve the tungsten-barium cathode.

The forcing factor of poisoning emitter can be produced which contain the by adding to a working body, used in the operation tungsten-barium cathode poisoning the cathode impurities. Typically, during normal operation the tungsten-barium chloride cathodes used xenon high purity (GOST 10219-77, the content of the xenon 99,9997%). Estimates show that for every atom impurities, can have a toxic effect on the emitter cathode (first of all, these atoms are oxygen atoms, the composition of impurities are also the atoms of inert gases and a different connection), you have a lot of xenon atoms ~100000. When such a small proportion of impurities, the probability that all chemically active atoms in the contact area of the emitter will participate in chemical reactions on its surface during operation tungsten-barium cathode, will be great.

This is because the emitter in the tungsten-barium chloride cathodes has, as a rule, the length far greater than its diameter (typically 5...10), and also with the fact that in the area of the arc discharge, the impurity atoms can be ionized and to be involved in the process of recycling together with particles of xenon before the formation of stable compounds on the surface of the emitter is heated to a high temperature. This is indicated by the results of the analysis of long-term resource tests tungsten-barium cathode described in [Timoti R. Sarver-Verhey "Destructive evaluation of a xenon hllow cathode after a 28,000 hour life test" AJAA-98-3482]. In these conditions, the low probability of passing atoms such active impurities around the gas path tungsten-barium cathode without chemical interaction with the materials of the emitter part of the tungsten-barium cathode.

In this regard, we can assume that the increase in the proportion of impurities in the composition of the working fluid, can have a toxic effect on the emitter tungsten-barium cathode, even on the order (in this case, each atom impurities will be also a lot of xenon atoms is ~10,000) will be accompanied by the almost complete participation of all supplied to the tungsten-barium cathode in such proportions toxic substances materials emitter parts of the cathode. Thus, the acceleration factor in this degradation factor can be increased to a significant level of ~10.

The forcing factor of ablation of barium tungsten-barium cathode can be produced by overheating its emitter through the inclusion of starter heater mode, power is reduced compared to the power start heating the tungsten-barium cathode.

The drift rate of the barium is determined primarily by the temperature of the emitter. When the temperature increases not only the rate of evaporation of barium from the surface of the emitter, but the rate of decomposition of barium oxide in the volume of the emitter, and the speed of diffuse the barium to the surface from the depth of the volume of the emitter. Increasing the temperature of the emitter, it is possible to increase the speed of ablation of barium. The magnitude of the acceleration factor by factor of ash barium can be significant, as the drift rate of the barium nonlinear increases with increasing temperature.

Way of forcing ash barium, the least distorting physics processes at an operational mode of the tungsten-barium cathode (in contrast to the technical solutions proposed in [Kashenkov I., Kovalev, VN, Lyapin A.A., Pekhterev SV, Chursin MM "Theoretical background of accelerated life tests of the cathode-compensator in forced mode", Proc. CT, issue 3 (131), 1991]), it is necessary to recognize the increase in the temperature of the emitter by additional heating of the emitter due to the inclusion of his starting of the heater. Because the additional power of this warming will be significantly less power start heating the emitter before ignition of the discharge cathode, it will not lead to the limitation of resource characteristics of the cathode by reducing health starting of the heater.

Forcing factor erosion emitter node tungsten-barium cathode can be produced by the exceptions to the timeline resource test cathode cycle cooling its emitter node below the temperature which provides the ignition of the discharge cathode.

p> As the results of fatigue tests of tungsten-barium chloride cathodes changing the geometric characteristics emitting site with continuous testing, as a rule, does not occur [Timoti R. Sarver-Verhey "Destructive evaluation of a xenon hollow cathode after a 28,000 hour life test" AJAA-98-3482]. Geometric characteristics change mainly in the process of igniting the discharge. At the time of ignition, i.e. at the time of formation of the arc discharge, the emitter portion of the tungsten-barium cathode is subjected to the most intense heat and erosive effects.

This is because when the operational mode of the tungsten-barium chloride cathode when an electrical arc is formed near-cathode drop potential is at the level of ~10V, which is below the threshold of sputtering of many structural materials. The plasma potential inside the cavity of the emitter and the area of the diaphragm, is not much different from this value due to the relatively low ohmic cost of current flow discharge in dense enough ionized plasma, typical for this tungsten-barium chloride cathodes. The temperature of the plasma in these tungsten-barium chloride cathodes is too small, it is at the level of ~2 eV. Therefore, in the internal cavity of the emitter part of the tungsten-barium chloride cathodes practically not appear ions with high energy, able is rivetti to a noticeable dispersion of the details of this part, only in the output part of the emitter zone may receive a certain quantity of such ions produced in the region Pocognoli electrode or cut tungsten-barium cathode.

When the ignition discharge tungsten-barium cathode, the situation is quite different, the voltage of the ignition discharge for its reliable ionization is usually at the level of 100...300V. In this case, at the moment of ignition of the discharge occur ions with high energy bombarding the emitter portion of the tungsten-barium cathode and the first aperture of the emitter located on the shortest distance from Pocognoli electrode.

Thus, the main negative erosive effect on the emitter part of the tungsten-barium cathode will occur at the moment of ignition, and not during the preparation of ignition (start heating, the supply of the working fluid), to stabilize the arc discharge, then removing or cooling the tungsten-barium cathode.

This allows forcing factor erosion emitter node tungsten-barium cathode by the exceptions to the timeline resource test tungsten-barium cathode cycle cooling its emitter node below the temperature at which is provided an ignition discharge tungsten-barium cathode. Figure 3 in its lower part presents the procedure of the step test of tungsten bar is avago cathode during the crossing of the factor of erosion of its emitter node (Express sequence diagram). On the same figure 3 in its upper part for comparison presents the most commonly used procedure for Autonomous test of tungsten-barium cathodes on the number of inclusions (typical sequence diagram).

When using a typical timeline of Autonomous life test tungsten-barium chloride cathodes on the number of starts each cycle start and run a tungsten-barium cathode starts from the start of heating of the emitter, which is held in the normal rated operation. Then, the tungsten-barium cathode served the working medium between the anode and tungsten-bereavem cathode voltage discharge, after which the process start heating the tungsten-barium cathode is the supply voltage of the ignition between the emitter and podignem electrode.

Supply voltage ignition is carried out when the temperature of the emitter part of the tungsten-barium cathode, including aperture emitter, a few will exceed the minimum ignition temperature of the discharge - TPOG min(see figure 3), which increases the reliability of the starting tungsten-barium cathode. When the electrostatic discharge ignition is initiated by an electrical arc between the tungsten-bereavem cathode and anode. In this period of time the temperature of the emitter part of the tungsten-barium cathode reaches a maximum value of Tmaxon the Kolka starting to warm up and the ignition is not already dismounted and advanced in the area of the emitter of the heat from the arc discharge. After the appearance of the discharge current power source ignition of the discharge and the start of warm-up is disabled.

Then some time is supported by an electrical arc between the tungsten-bereavem cathode and anode to stabilize the temperature of the emitter part of the tungsten-barium cathode, which, as a rule, for the tungsten-barium chloride cathodes below the temperature of ignition of the discharge. After this cutoff arc discharge and tungsten-barium cathode goes into a stage of cooling. Then the next cycle start repeat all the above-described procedures. Full implementation cycle τcycle 1as can be seen from figure 3, significant.

During the crossing of the factor of erosion of the emitter node of the first cycle of start-up and operation tungsten-barium cathode begin from the start of heating of the emitter. Then, the tungsten-barium cathode serves the working body, and between the anode and tungsten-bereavem cathode serves discharge voltage and the voltage of the ignition. When the electrostatic discharge ignition is initiated by an electrical arc between the tungsten-bereavem cathode and anode, after which the power source of the ignition of the discharge and the glow off. After a brief time of ignition of the discharge, accompanied by intense trigger erosion, the temperature of the emitter and its diaphragm will start to fall and further work the tungsten-barium cathode stationary in the arc mode will not lead to negative consequences, affecting the resource of a tungsten-barium cathode, equivalent to those that occur at the moment of starting the tungsten-barium cathode.

This allows, not including more heater tungsten-barium cathode, wait lowering the temperature of the diaphragm emitters TDSto the value of TDS= TPOG min+ ΔTDSwhere δ tDS- supply temperature to improve the reliability of ignition (see figure 3). Next should be off the arc discharge, and then, without shutting down the flow of the working fluid, to produce the following ignition of the discharge with simultaneous initiation of the arc discharge between the anode and tungsten-bereavem cathode by including a source of ignition of the discharge and source of discharge, the cathode-anode". Each subsequent act include tungsten-barium cathode should be conducted in a similar manner until the completion of the testing phase. The time cycle τcycle 2in this case, will be determined by the time of the maximum temperature of the emitter part of the tungsten-barium cathode and then a quick drop to a value of TPOG min+ ΔTDS.

From the above description it follows that the use of this method allows for a comprehensive account of the impact of all the basic factors of degradation when performing accelerated life tests tungsten-BA is avago cathode, that gives the possibility to obtain high acceleration and gives the possibility to investigate the impact of each factor on resource degradation characteristics of the cathode.

Device for conducting accelerated testing tungsten-barium cathode (see figure 4) contains the vacuum chamber 1 with the pumps 2 and 3, high and low pressure respectively. In the vacuum chamber is mounting unit 4 is installed on the tungsten-barium cathode 5, and in front of it posted by the anode 6. The power supply system includes a source of ignition 7, the power source of order 8, the power source starter heater 9 and a switch 10 for switching mode continuous operation with less power than the power start heating the tungsten-barium cathode 5. The system includes measuring means 11 with the measuring line 12, it is used for measuring the parameters of the experimental setup, including to measure the basic parameters of the degradation of the tungsten-barium cathode.

Supply of the working fluid in the tungsten-barium cathode consists of two parts. First, the main part consists of tank 13, regulator and flow meter 14, valve 15, it is used to feed the tungsten-barium cathode of the working fluid that is used during normal operation of the cathode (see above). The second part, consisting of tank 16, the regulator and the flow meter 17, valve 18 is an additional supply system, which serves to supply the tungsten-barium cathode of the working fluid with the addition to it of toxic tungsten-barium cathode impurities. For this purpose, the tank 16 may be added a certain amount of toxic substances. The output of the additional supply system through the valve 18 is connected with the output of the main part of the supply system, i.e. with the valve outlet 15.

The device operates as follows. In accordance with the General program of accelerated life tests tungsten-barium cathode (see figure 2) launch the first part of the accelerated life test, consisting of several stages (see figure 1). First we start with the first phase of testing, but before that produce at least one inclusion and the work of the tungsten-barium cathode on the primary operating mode without forcing any degradation factor (see figure 1) to determine the initial values of the parameters of the degradation of the cathode. To do this, the tungsten-barium cathode serves the working body of the main part of the supply system (the valve is open 15, and the valve 18 is closed), serves a discharge voltage between the tungsten-bereavem cathode and anode through the inclusion of a power source of order 8 and include the power source starter heater 9 operating mode heating wolf who am barium cathode (see Fig 4). When the switch 10 must be in the position that provides the nominal operation mode start heating.

After reaching the required time start heating serves the voltage tungsten-barium from the cathode source of ignition 7, to produce the ignition of the discharge tungsten-barium cathode, which triggers the occurrence of an electric arc between tungsten-bereavem cathode 5 and anode 6. Then turn off the source of ignition 7, the power source starter heater 9 and maintain the arc discharge to achieve steady-state operation, the tungsten-barium cathode. Then make measurements of parameters of the experimental setup, including the measurement of basic parameters of the degradation of the tungsten-barium cathode. After this cutoff tungsten-barium cathode and cooling. Then, if necessary, to Refine the obtained values of the underlying parameters of the degradation can be similarly carried out several re-starts the tungsten-barium cathode.

Then proceeding directly to the first stage of the first part of the test (see figure 1), thus implementing the forcing factor of poisoning emitter through the tungsten-barium cathode with an additional supply system performing submission in tungsten-barium cathode rabochaia with a high content of toxic tungsten-barium cathode impurities. To this end, the valve 15 of the output of the main supply system is closed and the valve 18 additional filing system open. Next, perform a certain number of cycles of operation of the cathode using the above procedures.

Then again produce at least one on and carry out the work of the tungsten-barium cathode mainly operational mode without forcing any degradation factor (see figure 1) to determine the new values of the parameters of the degradation of the cathode to assess the degree of degradation of the tungsten-barium cathode. The valve 15 of the output of the main supply system is opened, and the valve 18 for more supply system is closed.

After that, proceed to the second stage of the first part of the test (see figure 1) and provide the forcing factor of ablation of barium tungsten-barium cathode by some overheating its emitter by enabling the starting of the heater on the mode of lower power than the power of starting heating of the cathode. For this purpose, the switch 10 source starter heater 9 is switched to the position for operation starting the heater for the mode of lower power than the power start heating the tungsten-barium cathode, which increases the temperature of the emitter cathode, resulting in increased speed of ablation barium./p>

Then again produce at least one inclusion and the work of the tungsten-barium cathode on the primary operating mode without forcing any degradation factor (see figure 1) to determine the new values of the parameters of the degradation of the cathode to assess the degree of degradation of the cathode.

Then proceed to the completion of the third stage of the first part of the test (see figure 1) and thus provide a forcing factor erosion emitter node by the exceptions to the timeline resource test tungsten-barium cathode cycle cooling its emitter node below the temperature at which is provided an ignition discharge tungsten-barium cathode (see figure 3). This increases the frequency of filing and off voltages of the ignition, the frequency of filing and the off voltage of discharge between the tungsten-bereavem cathode and anode on the tungsten-barium cathode and starter heater tungsten-barium cathode after the primary discharge ignition off (you can translate the power source starting the heater in the mode of lower power, if the minimum ignition temperature of the discharge TPOG minclose to the maximum temperature Tmaxand it interferes with the normal organization of test cycles).

Then again produce at least one inclusion and the work of the tungsten-barium cathode mainly service the ohms mode, without forcing any degradation factor (see 1) to determine the new values of the parameters of the degradation of the tungsten-barium cathode to assess the degree of degradation of the tungsten-barium cathode.

The first part of the accelerated life test, the tungsten-barium cathode end and proceed to the next part of the test, and so on until the final part of the test in accordance with the General program of accelerated life tests tungsten-barium cathode (see figure 2). When this is repeated all the above operations, including the measurement of basic parameters of the degradation in the pauses between each phase of testing.

Thus, the proposed technical solutions allow to produce a comprehensive account of the impact of all the basic factors of degradation when performing accelerated life tests tungsten-barium cathode with the maximum possible approximation to the full-scale tests of tungsten-barium cathode due to the alternate forcing first one, then second, then third factor degradation during testing, and not all at once. At the same time achieving high acceleration tests, as well as the opportunity to explore the impact of each factor on resource degradation characteristics of tungsten-barium cathode and promptly identify the negative impact of the factor, the cat is who in the greatest degree lowers the resource characteristics of tungsten-barium cathode.

Sources of information

1. A.I. Morozov, "Introduction to plasmadynamic", M: "FIZMATLIT", 2006

2. O.A. Gorshkov, V.A. Muravlev, A.A., shagaida "Hall and ion plasma engines for spacecraft" / Ed. by A.S. korotyeyeva "engineering", 2008

3. Rams VP, A. I. Vasin, V.A. Petrosov "Problems of accelerated tests of electric propulsion thrusters", proceedings of CT, issue 3 (131), 1991

4. Timoti R. Sarver-Verhey "Destructive evaluation of a xenon hollow cathode after a 28,000 hour life test" AJAA-98-3482.

5. Arhipov Century, A. Bober, Gnizdor R., K. Kozubsky, N. Maslennikov, Pridannikov S. "Results of 7000-hour SPT-100 life test" the 24-th International Electric Propulsion Conference, IEPC-95-39, Moscow, (Russia), 1995.

6. Akimov V.N., O.A.Gorshkov, A.I.Vasin, V.N.Shutov et al. "Development of KM-5 hall effect thruster and it flight testing onboard a GEO spacecraft "Express-A4", Progress in Propulsion Physics, EUCASS book series, Ed. Wu L.De Luca, Torus Press, vol. 1, 2009, p.411-424.

7. "Guidelines. Reliability in engineering. Accelerated testing. General provisions", RD 50-424-83, M.: Publishing house of standards, 1984

8. Grishin S.D., Kashenkov V., Klimenko, G., Kovalev V., Lyapin A., M. Chursin "endurance testing of cathode-compensator on the start-up mode and the ways of their acceleration", proceedings of CT, issue 3 (131), 1991

9. The kashenkov I., Kovalev, VN, Lyapin A.A., Pekhterev SV, Chursin MM "Theoretical background of accelerated life tests of the cathode-compensator in forced mode", Proc. CT, issue 3 (131), 1991

10. Baranov, V.I., A. I. Vasin, V.A. Petrosov "Model erosion emitter of the I cathode to predict resource on accelerated testing", Coll. of CT, issue 3 (131), 1991

1. The method of accelerated testing of cathode plasma engines, including Autonomous fire tests cathode, the implementation of multiple inclusions of the cathode, the measurement of its basic parameters of degradation, testing in a forced mode of operation of the cathode, characterized in that the test is divided into stages, with each stage producing forcing one of the factors of degradation of the cathode under the simultaneous effect on the cathode of all other factors of degradation in the operational mode, and forcing each of the factors of degradation carried out at least once.

2. The method according to claim 1, characterized in that the stages are grouped in several parts, the number of stages being equal to the number of the main factors of degradation, and in each of these stages produce a forcing factor degradation, different from all the others.

3. The method according to claim 2, characterized in that after the completion of each phase of testing produce at least one inclusion and cathode mainly operational mode without forcing any degradation factor.

4. The method according to claim 1, characterized in that the speed up factor of degradation involves poisoning the emitter, is produced by adding to a working body used in exploits and tungsten-barium cathode, toxic tungsten-barium cathode impurities.

5. The method according to claim 1, characterized in that the crossing of the degradation factor, consisting in the release of barium from the tungsten-barium cathode, produced by overheating its emitter through the inclusion of starter heater mode power less than the power start heating the tungsten-barium cathode.

6. The method according to claim 1, characterized in that the speed up factor of degradation lies in the erosion of the emitter node tungsten-barium cathode produced by the exceptions to the timeline resource test tungsten-barium cathode cycle cooling its emitter node below the temperature which provides the ignition of the discharge cathode.

7. Device for conducting accelerated testing of cathode plasma engines, containing a vacuum chamber with a pump, the delivery system of the working fluid, the power system including a source start heating the cathode Assembly is installed in front of the cathode, the anode, a system for measuring the basic parameters of degradation, characterized in that the device is provided with an additional supply system, which is the working body with the addition of him poisoning the cathode impurities, and the output of the additional system flow through the valve is connected to the output of the main supply system, Istochnik power starter heater is equipped with a switch mode continuous operation with less power than the power of starting heating of the cathode.



 

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