CN110529728B - Device and method for online detection of service life of infrared focal plane detector Dewar flask - Google Patents
Device and method for online detection of service life of infrared focal plane detector Dewar flask Download PDFInfo
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- CN110529728B CN110529728B CN201910413702.5A CN201910413702A CN110529728B CN 110529728 B CN110529728 B CN 110529728B CN 201910413702 A CN201910413702 A CN 201910413702A CN 110529728 B CN110529728 B CN 110529728B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C13/00—Details of vessels or of the filling or discharging of vessels
- F17C13/005—Details of vessels or of the filling or discharging of vessels for medium-size and small storage vessels not under pressure
- F17C13/006—Details of vessels or of the filling or discharging of vessels for medium-size and small storage vessels not under pressure for Dewar vessels or cryostats
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C13/00—Details of vessels or of the filling or discharging of vessels
- F17C13/02—Special adaptations of indicating, measuring, or monitoring equipment
- F17C13/025—Special adaptations of indicating, measuring, or monitoring equipment having the pressure as the parameter
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C3/00—Vessels not under pressure
- F17C3/02—Vessels not under pressure with provision for thermal insulation
- F17C3/08—Vessels not under pressure with provision for thermal insulation by vacuum spaces, e.g. Dewar flask
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L21/00—Vacuum gauges
- G01L21/30—Vacuum gauges by making use of ionisation effects
- G01L21/32—Vacuum gauges by making use of ionisation effects using electric discharge tubes with thermionic cathodes
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2203/00—Vessel construction, in particular walls or details thereof
- F17C2203/03—Thermal insulations
- F17C2203/0391—Thermal insulations by vacuum
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2250/00—Accessories; Control means; Indicating, measuring or monitoring of parameters
- F17C2250/04—Indicating or measuring of parameters as input values
- F17C2250/0404—Parameters indicated or measured
- F17C2250/043—Pressure
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2270/00—Applications
- F17C2270/05—Applications for industrial use
- F17C2270/0509—"Dewar" vessels
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Abstract
The invention provides a device and a method for online detecting the service life of an infrared focal plane detector Dewar flask, which comprises a vacuum chamber and a plurality of station interfaces connected with the vacuum chamber, and a measuring component connected with one station interface through a measuring exhaust pipe; the other end of the measuring component is provided with a second BA hot cathode gauge which is sequentially connected with a vacuum gauge and a computer. The invention obtains the vacuum degree of a key process parameter by real-time online vacuum detection, and establishes a mathematical model of the useful life of vacuum and the key process parameter by applying the rarefied gas physics and the vacuum technical principle so as to obtain the gas outlet rate of a gas source. The method is beneficial to optimizing the vacuum obtaining process, improving the production efficiency and reducing the production cost, can effectively control the quality parameters of the vacuum obtaining process, and improves the high vacuum heat insulation capability and the reliability of the refrigeration type infrared focal plane detector Dewar component to be detected.
Description
Technical Field
The invention relates to a device and a method for detecting the service life of an infrared focal plane detector Dewar flask on line, in particular to a device and a method for detecting the effectiveness of a high-vacuum heat insulation function in the process of on-line real-time air extraction of a packaging refrigeration type infrared focal plane detector Dewar flask, and belongs to the technical field of infrared and vacuum.
Background
The dewar is a vacuum insulated container with a vacuum sandwich structure which can effectively reduce radiation, convection and conduction heat transfer. The dewar bottle structure is closely related to the infrared detector chip, the refrigeration mode and the system interface, which are essential components of the refrigeration infrared focal plane detector, and provides refrigeration environment and optical-mechanical interface for the detector chip. The de-vacuuming Dewar is a vacuum repairable Dewar, and the vacuum service life of the de-vacuuming Dewar is the service life with repair. The non-vacuum-releasing dewar is a vacuum unrepairable dewar, and has strict requirements on vacuum generation (obtaining vacuum) for ensuring the long vacuum life, such as vacuum integrity and vacuum sanitation of component assembly and manufacture, degassing treatment in the air extraction process and the like. The vacuum life of a non-debulked dewar is the useful life without repair.
The non-vacuum Dewar flask is used for packaging the refrigeration type infrared focal plane detector, provides support, connection and vacuum heat insulation working conditions for a focal plane array, is an important carrier of an optical electromechanical interface, and the refrigeration type infrared focal plane detector is a high-vacuum heat insulation container composed of a window, a connector, an inner tube, an outer tube, a refrigerator interface and the like, and is shown in figure 1. Gas source gradually releases gas in the working or non-working process of the infrared focal plane detector dewar bottle refrigerating machine assembly, the vacuum degree of a non-vacuum-release dewar bottle can be slowly reduced along with time, the high vacuum heat insulation efficiency slowly becomes poor and degrades, and the fault that the cooling time exceeds the set time is generated.
The dewar vacuum degree and vacuum maintenance (vacuum life) of the packaging refrigeration type infrared focal plane detector have the highest requirements, and the realization of long service life (ten years, fifteen years and twenty years) requires the common efforts of design and manufacture. The common stainless steel vacuum cup is a non-vacuum-release metal Dewar bottle manufactured by vacuum sealing at a high temperature of four to five hundred ℃, the glass thermos bottle is a non-vacuum-release glass Dewar bottle manufactured by vacuum sealing at a high temperature of two to three hundred ℃, and the visible high-temperature baking and air-exhausting process is favorable for obtaining a long service life. However, the refrigerated infrared focal plane detector cannot withstand the pump-down process beyond 80 ℃ bake temperature. Its vacuum life is determined by the vacuum gain process quality characteristics, measured by the time from the permanent cold press seal at termination of vacuum evacuation to vacuum failure. The ability to maintain the dewar vacuum at the design minimum allowable vacuum for extended periods of time has been an urgent concern for users and manufacturers of metrology testing and quality and reliability bottlenecks. The dewar cavity must have excellent vacuum integrity and air tightness, and the proper air extraction process and the right use of the getter can effectively ensure that the non-vacuum dewar meets the requirement of a user for customizing a vacuum useful life (maintenance-free life) for ten years to twenty years or more.
Currently, to detect the vacuum degree of the produced refrigeration type infrared focal plane detector assembly, the prior art device of fig. 2 is generally adopted for detection, and the device comprises a vacuum chamber, a plurality of station interfaces connected with the vacuum chamber, and a first BA hot cathode gauge 2 connected with the vacuum chamber through a CF vacuum flange 4. The refrigeration type infrared focal plane detector Dewar component 1 to be detected is connected with the station interface through the exhaust pipe 6, and the refrigeration type infrared focal plane detector Dewar component 1 to be detected can be detected.
FIG. 3 is a schematic vacuum system diagram of the prior art device described above, showing the vacuum level p detected by the first BA hot cathode gauge 2 measuring vacuumbBut the vacuum degree p of each refrigeration type infrared focal plane detector Dewar component 1 to be detected in the workpiece cannot be objectively and accurately reflected, and the difference between the vacuum degrees p and the vacuum degree p is 2-3 orders of magnitude. In the process of the existing non-vacuum-release Dewar vacuum obtaining process, an effective monitoring instrument is not used for detecting the gas source release quantity affecting the vacuum service life in the production process in real time on line, the transient gas source load meeting the vacuum long-service life requirement cannot be reliably confirmed, whether the gas pressure in a Dewar cavity meets the high-vacuum heat insulation requirement or not is not known, and the vacuum obtaining process is blindly established only by experience. Sealing off the vacuum Dewar flask by testingJudging whether the vacuum degree is good or not according to the heat load reflecting the high vacuum heat insulation capacity, collecting and obtaining the truncation failure data and the service life distribution information by using an accelerated service life test method according to the vacuum failure mechanism of the non-vacuum Dewar flask, carrying out statistical analysis to evaluate the service life, and confirming that the process for obtaining the vacuum of the Dewar flask meets the requirement of customizing the useful service life of the vacuum by a user.
It can be seen that, currently, the vacuum obtaining equipment for generating vacuum by using the technical principle of fig. 3 cannot detect that the vacuum of the refrigeration type infrared focal plane detector Dewar component 1 to be detected in a workpiece has key process parameters of vacuum degree, gas source gas outlet rate and useful vacuum service life. The technological process includes the steps of exhausting air for a long time, determining the cold pressing and sealing time by experience, and forming the non-vacuum Dewar flask by sealing according to the user requirement index through blindly thinking. Then, an accelerated life test is carried out by applying a reliability engineering technology, and the useful life of the vacuum is obtained through statistical analysis.
However, tests to verify the useful life of a non-debulked dewar vacuum are expensive and time consuming. The effective accelerated life test generally needs 30-60 samples (to-be-tested refrigeration type infrared focal plane detector Dewar component 1), and requires at least 5 failure numbers. The length of the test time depends on how many faults are allowed in the test, and the minimum test time is a function of the required level of reliability, the applied stress and the acceleration of the test, and can often take months or tens of months. Secondly, the vacuum degree in the cavity of the Dewar bottle cannot be known, the liquid nitrogen evaporation capacity in unit time can be detected only through a balance or a flowmeter, the heat load is calculated by utilizing the specific enthalpy difference between two phases of the phase change under the same temperature and pressure, and the high vacuum heat insulation capacity of the Dewar bottle is indirectly inferred. The vacuum obtaining process which is blindly established by experience can be confirmed by repeating the steps for a plurality of times, and the vacuum obtaining process is an effective vacuum obtaining process which meets the service life requirement of a user. No matter the service life or the vacuum degree is the quality parameter test which is carried out after the air exhaust is stopped and the vacuum is sealed off, therefore, a device and a method which can realize the online real-time detection of the transient vacuum degree and the service life in the air exhaust production process need to be researched and developed.
Disclosure of Invention
In order to solve the problems, the invention provides a device and a method for online detecting the service life of an infrared focal plane detector Dewar flask. The bottleneck problem that users and manufacturers are difficult to clearly predict the useful service life of the vacuum for a long time is solved, and the purposes of improving the quality and the reliability of products are achieved.
The invention is realized by the following technical scheme: a device for on-line detecting the service life of a Dewar flask of an infrared focal plane detector comprises a vacuum chamber, a plurality of station interfaces connected with the vacuum chamber, and a measuring component 1 'connected with one station interface through a measuring exhaust pipe 6'; the other end of the measuring component 1 ' is provided with a second BA hot cathode gauge 2 ', and the second BA hot cathode gauge 2 ' is sequentially connected with a vacuum gauge 11 and a computer 13.
The station interfaces are a plurality of and are respectively connected with a plurality of refrigeration type infrared focal plane detector Dewar assemblies 1 to be tested through exhaust pipes 6. The refrigeration type infrared focal plane detector Dewar component 1 to be detected is a refrigeration type infrared focal plane detector Dewar component which is in the process of obtaining vacuum on a production line and is just waiting for air extraction production.
The refrigeration type infrared focal plane detector Dewar component 1 to be tested comprises a window, a connector, an inner pipe, an outer pipe and a refrigerator interface 3.
The measuring assembly 1 'comprises a window, a connector, an inner pipe and an outer pipe, the inner pipe is supported by an inner pipe fixing part 5, and the second BA hot cathode gauge pipe 2' is welded with the measuring assembly shell by laser. The structure composition of the measurement component 1' and the refrigeration type infrared focal plane detector Dewar component 1 to be measured is unchanged, and only the interface 3 of the refrigerator is removed.
The exhaust pipe 6 and the measuring exhaust pipe 6' are respectively connected with a station interface through an interface flange 15.
And stop valves 16 are arranged on the station interfaces.
The second BA hot cathode gauge 2' is connected to a vacuum gauge 11 via a signal transmission cable 10.
The vacuum gauge 11 is connected to a computer 13 via an RS232 transmission cable 12.
The vacuum chamber is also connected to a first BA hot cathode gauge 2 by a CF vacuum flange 4. The first BA hot cathode gauge 2 and the second BA hot cathode gauge 2' can be started simultaneously to play a role of subsection detection together.
The invention can detect the transient vacuum degree, the gas outlet rate of a gas source and the service life of a non-vacuum Dewar flask in a Dewar flask cavity of a packaging refrigeration type infrared focal plane detector in real time in the process of air extraction on a production line, and a figure 5 is a schematic vacuum system diagram of the invention, and a measured value p' of a vacuum-measuring assembly is slightly larger than an actual value p of a refrigeration type infrared focal plane detector Dewar component 1 to be measured in a workpiece. The overall technical scheme is that the structural composition of a measuring component 1' of an assembly and a cooling type infrared focal plane detector Dewar component 1 to be measured of a workpiece is kept unchanged to the maximum extent, only a component refrigerator interface 3 is removed, and an inner tube and all loaded objects including a focal plane array, a readout integrated circuit, a bonding lead, a cold screen and the like are reformed and reserved. Second, the introduction of second BA hot cathode gauge 2' cavity volume and surface gas generated measurement error is minimal. The assembly III must ensure the maximum similarity with the Dewar component 1 of the refrigeration infrared focal plane detector to be detected, and the cavity volume, the surface area and the structural shape characteristics of the assembly III are similar and comparable.
As shown in fig. 4 and 5, the measuring component 1' of the assembly (c) is formed by transforming a refrigeration type infrared focal plane detector Dewar component 1 to be measured, only the refrigerator interface 3 is removed, and the inner pipe fixing piece 5 is added. The measuring component 1 ' with the refrigerator interface 3 removed and the second BA hot cathode gauge 2 ' form a combined body III, the measuring component 1 ' and the second BA hot cathode gauge 2 ' are connected into a whole through laser welding, and the vacuum space comprises a cavity 9 of the second BA hot cathode gauge 2 ', a cavity 8 of the measuring component 1 ' and a cavity 7 of the measuring exhaust pipe 6 '. The assembly III is connected with an interface flange 15 of a station interface through a measuring exhaust pipe 6'. The measuring signal of the second BA hot cathode gauge 2' is connected to a vacuum gauge 11 through a transmission cable 10, the measured vacuum degree can be displayed locally on the vacuum gauge 11, and also can be connected to a computer 13 through an RS232 transmission cable 12, the computer 13 reads the instantaneous vacuum degree data measured by the vacuum gauge 11, analyzes, calculates and processes the data and outputs the vacuum degree, the air outlet rate and the service life data, wherein the vacuum degree and the air outlet rate (micro-flow of gas) are basic physical quantities of vacuum physics and technology. The vacuum degree is the ion current received by the direct measurement collector, the gas pressure is indirectly measured by the conversion of the gauge constant, and the value of the vacuum degree can be traced back to the national standard of pressure, so that the accuracy and the consistency are ensured. The indirectly measured outgassing rate and lifetime are calculated from a mathematical model by directly measuring the vacuum level.
The assembly (1) and the plurality of refrigeration type infrared focal plane detector Dewar assemblies (1) to be tested are connected with a plurality of station interfaces of the vacuum acquisition equipment (I) in parallel, and the assembly (III) is installed and connected on the station interface at the farthest end. The volume and the surface area of the cavity of the assembly (c) are larger than those of the refrigeration type infrared focal plane detector Dewar component 1 to be tested, and the gas source load of the assembly (c) is larger than that of the refrigeration type infrared focal plane detector Dewar component 1 to be tested; when the assembly (c) detects the vacuum degree, the air outlet rate and the service life which meet the requirements of vacuum quality characteristic parameters of a user, the vacuum degree, the air outlet rate and the service life of the refrigeration type infrared focal plane detector Dewar component 1 to be detected in the workpiece (c) are superior to the values required by the user. The transient vacuum degree, the air outlet rate and the service life of the refrigerating infrared focal plane detector Dewar component 1 to be detected in the air exhaust process are obtained by measuring the gas pressure by using the second BA hot cathode gauge 2' of the combination III through a comparison method and processing mathematical models and data. The measured value of the assembly III is regarded as the measured value of the Dewar component 1 of the refrigeration type infrared focal plane detector to be measured.
Another object of the present invention is to provide a method for online detecting the lifetime of a dewar of an infrared focal plane detector, which adopts the above-mentioned device for online detecting the lifetime of a dewar of an infrared focal plane detector, and specifically comprises the following steps:
1) starting vacuum obtaining equipment to connectThe stop valve 16 of the station interface performs air extraction when the pressure of the combined body (c) is less than 1 multiplied by 10-1When Pa, operating the vacuum gauge 11, switching on a cathode filament of the second BA hot cathode gauge 2', and displaying and acquiring the transient vacuum degree p (t) in the cavity of the combination body measured by the vacuum gauge 11 by the computer 13;
2) by using the lean gas physics and the vacuum technical principle, the mathematical model for establishing the useful life of vacuum and the key process parameters is as follows:
in the formula:
tls(t) is the useful life of the vacuum over the pump down time t, s; pmaxIs designed to allow maximum gas pressure, Pa; p (t) is the transient vacuum, Pa, at time t; is the gas outlet rate of the gas source at the time t, Pa.m3/s；qG(t) is the gas flow through the exhaust pipe at time t, Pa · m3/s；tiIs a given measurement time interval, s; v is the volume occupied by the ideal gas in equilibrium, m3；
3) Calculating according to the mathematical model of the step 2), and obtaining the real-time gas outlet rate and the vacuum useful life.
The working principle is as follows: the assembly (1) is connected with the interface flange (15) of the vacuum obtaining equipment (1) in parallel by the same detachable interface, so that the assembly (1) and the air exhaust channel of the refrigeration type infrared focal plane detector Dewar assembly (1) to be detected in the workpiece (II) can be ensured to have the same conductance.
Electrons emitted by the cathode of the second BA hot cathode gauge are accelerated by the grid, the electrons collide with gas molecules in the gas phase to ionize the gas molecules, the generated positive ions are received by the negatively biased collector to form an ion flow, and the ion flow IcWith electron current I emitted from the cathodeeAnd the gas pressure p is described by:
in the formula: p (t) is the transient vacuum at time t; i isc(t) is the ion current at time t; t is the pumping time; s is the sensitivity of the gauge; i isrIs a residual current independent of pressure. The measured transient vacuum degree p (t) is processed and converted by the vacuum gauge 11 according to the mathematical model of the formula and then is directly read.
The gas source for sealing off vacuum failure of the vacuum Dewar flask mainly comprises gas, pressure difference and gas pumping from atmosphere entering a cavity through a tiny leak hole to assemble clearance gas and vacuum cavity material internal overflow and surface desorption gas, wherein the load of the gas source enables the vacuum degree of the Dewar flask cavity to be reduced, so that the high vacuum heat insulation function fails, and the refrigeration overtime fault occurs to the Dewar component of the refrigeration type infrared focal plane detector. Therefore, by using the lean gas physics and the vacuum technical principle, a mathematical model of the useful life of the vacuum and the key process parameters is established as an expression (2).
According to the formula (2), the vacuum degree of the refrigeration type infrared focal plane detector Dewar component 1 to be tested after being sealed off from vacuum needs to meet the high vacuum heat insulation requirement, and the vacuum useful life required by a user needs to be met. The space requiring heat insulation is generally drawn to 10-4～10-5Pa vacuum degree. Gas pressure less than 1 x 10-3When Pa, the high vacuum insulation reaches the maximum efficiency; gas pressure greater than 1X 10-2At Pa, the high vacuum insulation capability becomes poor, and the thermal load increases the vacuum failure. The requirement that the air outlet rate of the gas source can be met only by fully exhausting for a long time if the high-vacuum heat insulation efficiency is maximized without exhausting for a long time and the vacuum long service life is maintained. When the vacuum service life of the component which is not allowed to be maintained is 20 years in the working or non-working process under the random stress of the natural environment temperature of the use region required by the user, the gas outlet rate of the gas source for exhausting and sealing the front component Dewar flask cavity is required to be less than 5 multiplied by 10-16Pa·m3S, when the gas pressure in the Dewar flask cavity is less than 10-5Pa。
The gas pressure p (t) is measured through the second BA hot cathode gauge 2' of the assembly III in the air exhaust process, the measured vacuum degree can be locally displayed on the vacuum gauge 11, the time sequence instantaneous vacuum degree data measured by the vacuum gauge 11 can also be read through the detection control software of the computer 13, and the minimum data sampling time is 1 second. And visualizing the time series instantaneous vacuum degree data to obtain an actually measured air extraction curve of the representation assembly and the air extraction differential equation. And calculating and processing data according to a mathematical model formula (2), and displaying the output vacuum degree, the gas outlet rate and the useful life of the vacuum in real time.
The error transfer equation for a useful life measurement chain is:
synthesizing P, Q, V error components to obtain the vacuum useful life time error:
when the user requires the useful life of vacuum for 20 years, the gas pressure of vacuum failure is 1 multiplied by 10-2Pa, gas pressure of Dewar flask cavity at vacuum sealing-off time 1 × 10-5Pa, volume 3.24X 10-5m3The Dewar component of infrared focal plane detector requires the gas source load gas outlet rate before vacuum sealing off to be less than 5 x 10-16Pa·m3And s. If the vacuum level P, the gas source gas outlet rate Q and the measured value of the volume V have 10 percent of measurement errors. Then 20 years vacuum useful life tlsThe measurement error of (2) was 3.56year (17.8%).
The gas source gas outlet rate error transfer equation is as follows:
and synthesizing dt, dp and V error components to obtain a gas velocity error:
wherein, the error of the gas pressure difference between the t moment and the t-1 moment is represented by dp ═ pt-pt-1Obtaining:
synthesis of pt、pt-1The error component is the error in the gas pressure difference:
p in this caset、pt-1Is a direct measurement, Q, dp is an indirect measurement; in the formula (7)
The error component is the measurement error allowed by the gas pressure.
If the vacuum degree measurement error is 10-30%, the volume measurement error is 10%, the time measurement error is 1%, and the measurement error of the outgassing rate is required to be less than 5 multiplied by 10-17Pa·m3And s. The measurement time is more than 2h, and the vacuum useful life t of 20 years can be metlsThe measurement error of (a) is less than 3.56year (17.8%).
The invention has the advantages and effects that:
the device provided by the invention can be obtained only by using the existing refrigeration type infrared focal plane detector Dewar component to be tested to be transformed, and can ensure that the assembly has the gas source load and the air extraction resistance of the refrigeration type infrared focal plane detector Dewar component 1 to be tested in the workpiece II to the maximum extent; and the assembly (c) and the refrigeration type infrared focal plane detector Dewar component 1 to be detected have the same gas source load and conductance, the vacuum of the assembly (c) can be detected to obtain the key process parameter vacuum degree, the actually measured air extraction curve of the air extraction differential equation can be obtained, and the air outlet rate and the useful vacuum life can be indirectly measured according to the life mathematical model formula (2) obtained by derivation.
The invention establishes a mathematical model of useful life of vacuum and key process parameters, and monitors the vacuum in the manufacturing process of products to obtain the process quality which meets the requirement of long life of users. The method has the advantages of improving the vacuum reliability of the refrigeration type infrared focal plane detector dewar assembly to be detected, reducing the production cost, solving the bottleneck problem and the common problem which puzzle users and manufacturers for a long time and are difficult to clearly predict the useful service life of vacuum, and achieving the purpose of improving the quality and the reliability of products. From the beginning, a method and a way for detecting the vacuum degree of the refrigeration type infrared focal plane detector dewar component to be detected to obtain key process parameters, namely the vacuum degree, the gas outlet rate of a gas source and the useful life of the vacuum on line in real time are provided. The method has the advantages that the optimal air extraction time meeting the service life customized by a user can be conveniently identified, the vacuum obtaining process is favorably optimized, the time and resources consumed by excessive air extraction are avoided, the production efficiency is improved, the production cost is reduced, the quality parameters of the vacuum obtaining process can be effectively controlled, and the high vacuum heat insulation capacity and reliability of the refrigeration type infrared focal plane detector Dewar assembly to be detected are improved. Without the need to perform expensive and time consuming accelerated life tests, the life of the product is reliably predicted while vacuum is being obtained on the product assembly line.
The device and the method provided by the invention have the following measurement technical indexes:
1) the vacuum degree measuring range is 6.6Pa to 6.6 multiplied by 10-8Pa, expansion uncertainty 10% -30%;
2) gas outlet rate measuring lower limit of 5 x 10 of gas source-16Pa·m3(s), extended uncertainty 10%;
3) the upper limit of the useful life of the vacuum is 20 years, and the uncertainty is expanded by 18 percent.
Drawings
FIG. 1 is a schematic structural diagram of a refrigeration-type infrared focal plane detector;
FIG. 2 is a schematic diagram of a prior art device;
FIG. 3 is a schematic vacuum system diagram of a prior art device;
FIG. 4 is a schematic structural diagram of the apparatus of the present invention;
FIG. 5 is a schematic vacuum system diagram of the present invention;
FIG. 6 is a measured pump-down curve for an example.
Detailed Description
The invention is further illustrated by the following examples and figures.
As shown in fig. 4 and 5, the device for online detecting the service life of the infrared focal plane detector dewar comprises a vacuum chamber, a plurality of station interfaces connected with the vacuum chamber, and a measuring component 1 'connected with one station interface through a measuring exhaust pipe 6'; the other end of the measuring component 1 ' is provided with a second BA hot cathode gauge 2 ', and the second BA hot cathode gauge 2 ' is sequentially connected with a vacuum gauge 11 and a computer 13.
The station interfaces are a plurality of and are respectively connected with a plurality of refrigeration type infrared focal plane detector Dewar assemblies 1 to be tested through exhaust pipes 6. The refrigeration type infrared focal plane detector Dewar component 1 to be detected is a refrigeration type infrared focal plane detector Dewar component which is in the process of obtaining vacuum on a production line and is just waiting for air extraction production. The refrigeration type infrared focal plane detector Dewar component 1 to be tested comprises a window, a connector, an inner pipe, an outer pipe and a refrigerator interface 3. The measuring assembly 1 'comprises a window, a connector, an inner pipe and an outer pipe, the inner pipe is supported by an inner pipe fixing part 5, and the second BA hot cathode gauge pipe 2' is welded with the measuring assembly shell by laser. The structure composition of the measurement component 1' and the refrigeration type infrared focal plane detector Dewar component 1 to be measured is unchanged, and only the interface 3 of the refrigerator is removed. The exhaust pipe 6 and the measuring exhaust pipe 6' are respectively connected with a station interface through an interface flange 15. And stop valves 16 are arranged on the station interfaces. The second BA hot cathode gauge 2' is connected to a vacuum gauge 11 via a signal transmission cable 10. The vacuum gauge 11 is connected to a computer 13 via an RS232 transmission cable 12. The vacuum chamber is also connected to a first BA hot cathode gauge 2 by a CF vacuum flange 4. The first BA hot cathode gauge 2 and the second BA hot cathode gauge 2' can be started simultaneously to play a role of subsection detection together.
When in use, the utility model is used,
1) start trueThe air obtaining equipment is connected to the stop valves 16 of the interfaces of the stations for air extraction, and when the pressure of the cavity of the combined body is less than 1 multiplied by 10-1When Pa, operating the vacuum gauge 11, switching on a cathode filament of the second BA hot cathode gauge 2', and displaying and acquiring the transient vacuum degree p (t) in the cavity of the combination body measured by the vacuum gauge 11 by the computer 13;
2) by using the lean gas physics and the vacuum technical principle, the mathematical model for establishing the useful life of vacuum and the key process parameters is as follows:
in the formula:
tls(t) is the useful life of the vacuum over the pump down time t, s; pmaxIs designed to allow maximum gas pressure, Pa; p (t) is the transient vacuum, Pa, at time t; is the gas outlet rate of the gas source at the time t, Pa.m3/s；qG(t) is the gas flow through the exhaust pipe at time t, Pa · m3/s；tiIs a given measurement time interval, s; v is the volume occupied by the ideal gas in equilibrium, m3；
In order to visually reflect the change rule among the vacuum degree, the air outlet rate and the useful vacuum service life in the air extraction process, the time series instantaneous vacuum degree data is visualized to obtain an actually measured air extraction curve representing the combination and an air extraction differential equation, as shown in FIG. 6.
3) Calculating according to the mathematical model of the step 2), and obtaining the real-time gas outlet rate and the vacuum useful life.
The figure shows a chamber volume of 2.3X 10-5m3The air extraction example of the refrigeration type infrared focal plane detector Dewar component is that the sampling time of p (t) is 1 second, and the curve p (t) -t is a visual curve of measured values without data filtering and fitting. The 6 upward significant ascending and descending changes in the p (t) -t curve are caused by that the heating air-out treatment is carried out at the 6 time points, and other small and insignificant abnormal fluctuations should occurDue to the measuring instrument or vacuum acquisition equipment. Outgassing rate Q (t), vacuum useful life tls(t) is calculated according to the mathematical model of the formula (2) and the measured values of p (t), and the visualized curve without the filter wave fitting process is shown in fig. 6, wherein the large-amplitude change interval corresponds to the heated gas-out time point and the abnormal value region. It can be seen that the Dewar cavity pressure of 1.2X 10 is 1.5 days of vacuum pumping-3Pa, gas outlet rate of 3.8X 10-14Pa·m3(s) predicted lifetime of 1.5 year; dewar cavity pressure 1.6X 10 after vacuum pumping for 15 days-5Pa, gas outlet rate 4.1X 10-16Pa·m3And/s, estimated lifetime of 16.5 year.
Claims (10)
1. The utility model provides a device of on-line measuring infrared focal plane detector dewar bottle life-span, includes vacuum chamber and a plurality of station interfaces that link to each other with vacuum chamber, its characterized in that: the device also comprises a measuring component (1 ') connected with a station interface through a measuring exhaust pipe (6'); the other end of the measuring component (1 ') is provided with a second BA hot cathode gauge (2 '), and the second BA hot cathode gauge (2 ') is sequentially connected with a vacuum gauge (11) and a computer (13);
the infrared focal plane detector dewar bottle life was measured as follows:
1) starting the vacuum obtaining equipment, connecting the stop valves (16) of the interfaces of all the stations for air extraction, and when the pressure of the cavity of the assembly is less than 1 multiplied by 10-1When Pa, operating the vacuum gauge (11), switching on a cathode filament of the second BA hot cathode gauge (2'), and displaying and acquiring the transient vacuum degree p (t) in the cavity of the assembly measured by the vacuum gauge (11) by a computer (13);
2) the mathematical model for establishing the useful life of the vacuum and the key process parameters is as follows:
in the formula:
tls(t) is the vacuum over the pumping time tService life, s; pmaxIs designed to allow maximum gas pressure, Pa; p (t) is the transient vacuum, Pa, at time t; q (t) is the gas outlet rate of the gas source at time t, Pa.m3/s；qG(t) is the gas flow through the exhaust pipe at time t, Pa · m3/s；tiIs a given measurement time interval, s; v is the volume occupied by the ideal gas in equilibrium, m3；
3) Calculating according to the mathematical model of the step 2), and obtaining the real-time gas outlet rate and the vacuum useful life.
2. The apparatus for on-line detection of infrared focal plane detector dewar bottle life span according to claim 1, wherein: the station interfaces are a plurality of and are respectively connected with a plurality of refrigeration type infrared focal plane detector Dewar assemblies (1) to be tested through exhaust pipes (6).
3. The device for on-line detecting the service life of the infrared focal plane detector dewar flask according to claim 2, wherein: the refrigeration type infrared focal plane detector Dewar component (1) to be tested comprises a window, a connector, an inner tube, an outer tube and a refrigerator interface (3).
4. The apparatus for on-line detection of infrared focal plane detector dewar bottle life span according to claim 1, wherein: the measuring assembly (1') comprises a window, a connector, an inner tube and an outer tube, and supports the inner tube by an inner tube fixing member (5).
5. The apparatus for on-line detection of infrared focal plane detector dewar bottle life span according to claim 1, wherein: the exhaust pipe (6) and the measuring exhaust pipe (6') are respectively connected with a station interface through an interface flange (15).
6. The apparatus for on-line detection of infrared focal plane detector dewar bottle life span according to claim 1, wherein: and stop valves (16) are arranged on the station interfaces.
7. The apparatus for on-line detection of infrared focal plane detector dewar bottle life span according to claim 1, wherein: the second BA hot cathode gauge (2') is connected with a vacuum gauge (11) through a signal transmission cable (10).
8. The apparatus for on-line detection of infrared focal plane detector dewar bottle life span according to claim 1, wherein: the vacuum gauge (11) is connected with a computer (13) through an RS232 transmission cable (12).
9. The apparatus for on-line detection of infrared focal plane detector dewar bottle life span according to claim 1, wherein: the vacuum chamber is also connected with a first BA hot cathode gauge pipe (2) through a CF vacuum flange (4).
10. A method for on-line detecting the service life of a Dewar flask of an infrared focal plane detector is characterized in that: the device for detecting the service life of the infrared focal plane detector dewar flask on line according to any one of claims 1 to 9 is as follows:
1) starting the vacuum obtaining equipment, connecting the stop valves (16) of the interfaces of all the stations for air extraction, and when the pressure of the cavity of the assembly is less than 1 multiplied by 10-1When Pa, operating the vacuum gauge (11), switching on a cathode filament of the second BA hot cathode gauge (2'), and displaying and acquiring the transient vacuum degree p (t) in the cavity of the assembly measured by the vacuum gauge (11) by a computer (13);
2) by using the lean gas physics and the vacuum technical principle, the mathematical model for establishing the useful life of vacuum and the key process parameters is as follows:
in the formula:
tls(t) is the useful life of the vacuum over the pump down time t, s; pmaxIs designed to allow maximum gasBody pressure, Pa; p (t) is the transient vacuum, Pa, at time t; q (t) is the gas outlet rate of the gas source at time t, Pa.m3/s；qG(t) is the gas flow through the exhaust pipe at time t, Pa · m3/s；tiIs a given measurement time interval, s; v is the volume occupied by the ideal gas in equilibrium, m3；
3) Calculating according to the mathematical model of the step 2), and obtaining the real-time gas outlet rate and the vacuum useful life.
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