V25: A 1 rumors that the spacecraft will be strongly influenced by a variety of space and environmental factors during its service in orbit. There are various factors in space environment. The main characteristics are solar electromagnetic radiation, charged particle irradiation, high vacuum, cold black environment, atomic oxygen erosion, and the impact of micro meteors and space debris. They have different effects on spacecraft and their structural components. When the total solar radiation energy is 1.4X103WVm2, the vacuum ultraviolet irradiation energy in the wavelength range of 5~200nm is 2.5X102WVm221. Although the vacuum ultraviolet irradiation energy accounts for a small proportion of the total solar radiation energy, its role is Very important 31. Photons have high energy (7.3 ~ 248eV) can make the Earth's upper atmosphere strongly ionized to form the ionosphere. After the surface of spacecraft is affected by them, photoelectric effect will occur, which will cause static electricity on the surface of spacecraft, which will affect the normal operation of electronic systems and magnetic devices in spacecraft. The action of photons on the material will cause the photoionization and photodecomposition effects of the molecules in the material, especially the chemical bonds of the polymer materials on the spacecraft, which will cause the material to lose quality, cause the surface to have gas evolution, and deteriorate the mechanical properties. Volatile condensates also affect the normal operation of optical devices and electronic devices on the spacecraft, and even cause them to malfunction. 141. At present, the developed countries of the aerospace industry pay more and more attention to vacuum ultraviolet irradiation for spacecraft and its structural components. Damage effect. Space loading test is the most effective way to research, but it is expensive and complicated to operate. Therefore, conducting space environment simulation tests on the ground is the main method adopted by most countries. Compared with the world's advanced technology, China's research on UV irradiation simulation started relatively late, especially the simulation of vacuum ultraviolet irradiation, but due to rapid development, it has now formed a technical field.
Ultraviolet irradiation can be divided into near-ultraviolet radiation (A-band, 400-320 nm), medium-ultraviolet radiation (B-band, 320-280 nm), and far-ultraviolet radiation (C-band, 280-200 nm) depending on wavelength. Extreme ultraviolet radiation (D-band or vacuum ultraviolet radiation, 200~5nm) 1 5 four bands. The simulation of vacuum ultraviolet irradiation mainly uses low-pressure helium, neon-helium mixed gas discharge lamps (wavelength 123.6 nm), oxygen lamps (wavelength 170-220 nm) and xenon lamps (wavelengths 30.4 nm and 584 nm). Their common disadvantages are: short working life, single wavelength simulation, and poor continuous adjustment of operating power. They can not simultaneously reflect the low temperature and vacuum environment in space and environmental factors, and are not suitable for research on space environment simulation on the ground. The jet vacuum vacuum ultraviolet simulation equipment described in this article overcomes the above shortcomings. It can simulate the continuous energy spectrum in the wavelength range of 5 to 200 nm, has a long working life, can be continuously adjusted in power, and can also simulate high vacuum and low temperature environments simultaneously. Some of the researches conducted by this equipment have also achieved satisfactory results. The ray simulation equipment in the wavelength range of 5~200nm has not been reported at present.
2 Jet vacuum ultraviolet irradiation simulation equipment 2.1 Basic requirements for vacuum ultraviolet irradiation simulation The simulation of vacuum ultraviolet irradiation should be performed in the wavelength range of 5~200nm, as close as possible to the distribution of solar energy; vacuum ultraviolet rays should be three-dimensional Irradiation pattern intensity and beam wavelength / nm type, the irradiated sample should be in a high vacuum environment. In addition to vacuum ultraviolet radiation, no other particles should be irradiated on the surface of the sample in the irradiation chamber; the energy generated by the vacuum ultraviolet irradiation simulation device should be higher than the actual space irradiation energy in order to accelerate the test; the simulation device should also Has long-term continuous performance.
22 Working principle and structure of jet-type vacuum ultraviolet irradiation simulator The structure of the jet-type vacuum ultraviolet irradiation simulator is as shown.
The basic principle is to make use of the different pressures to make the working gas pass through the ultrasonic nozzle to form the ultrasonic airflow into the vacuum chamber. The electron beam emitted by the electron gun is perpendicular to the jet and directed to the axis, and the vacuum ultraviolet rays generated by the excitation pass through the opening to enter the vacuum irradiation chamber. Keep the vacuum in the vacuum chamber at a temperature of 105Pa with the vacuum cooling system and the vacuum pumping system. The temperature is lower than that in 2011. The capacitance tube is installed at the opening to deflect the other charged particles generated by the jet and the electron beam to avoid the irradiation on the sample surface. . The radiation spectrum and intensity of the simulator are determined by the gas pressure at the nozzle, the temperature, and the energy and current intensity of the electron beam.
1—vacuum chamber; 2—801 cold screen; 3—ultrasonic nozzle; 4—201 cold screen; 5 connection tube; 6—rotary pump exhaust system; 7—cold head; 8—electron gun; 9 horizontal observation window; ―Capacitors; 11―Vertical viewing windows; 12―Electronic collectors.
At present, there are mainly three structural forms of jet vacuum ultraviolet irradiation simulation equipment. The difference between them is mainly due to the difference in pumping modes. The first is a low-temperature pumping simulator. As shown, this was an early design. Due to the limitations of the technology at the time, only a low-temperature condensate pump was used to maintain working pressure (103 Pa) and temperature (20 to 251), and Its continuous working time is not long. The second is a non-cryogenic pumping simulator. As shown, the pumping is performed using a rotary vane pump and a molecular pump. The simulator is installed in the low-vacuum chamber 1 and the main air flow is extracted by a high-power rotary vane pump. The sputtered air is pumped through a low-power rotary vane pump and a molecular pump. The generated ultraviolet light enters the high-vacuum chamber 2 and a capacitor is installed in the passage 8 To filter other charged particles, the working temperature obtained by this method is high, the working pressure does not exceed 2.6X103Pa. The third type is a combination of suction simulator, as shown, that is, the equipment used in this article, which uses two Extraction passage, main gas flow (97%) through connecting pipe 5 with rotary vane pumping air extraction pipe 6 with gas sparging gas flow (3%) condensing through cold condenser pump and cooling screen 4 and discharging with vacuum system, using cold head 7 guarantee that the working temperature in the vacuum chamber is always lower than 201 (in order to reduce the thermal load of the cryogenic condensate pump, the design of the cold screen 2 guarantees the temperature is 80K. The multi-stage cooling system ensures that the working temperature in the vacuum chamber is always lower than the 2011 two pumping The gas passage and good low-temperature environment effectively eliminated the working gas to obtain excellent working pressure in the vacuum chamber (15Pa), and installed an electron gun 8 at a fixed position from the air flow axis. The electron beam emitting energy of 1 keV is perpendicularly directed to the ultrasonic air flow emitted by the ultrasonic nozzle 3, and the electron collector 12 measures the electron beam current. The capacitor 10 is installed at an angle on the irradiation path of the ultraviolet ray, so that the jet and the electron beam excite. The other charged particles are deflected to avoid irradiating the surface of the sample. In order to monitor the working status of the simulator, two observation windows are designed on the vacuum chamber 1. The observation window 11 can observe the brightness of the jet vertically and the observation window 9 can be horizontal. Observe the stability of the jet, using this method to obtain the ideal working temperature and working pressure, and to enable the device to maintain long-term continuous operation.
2.3 Characteristics and technical parameters of jet-type vacuum ultraviolet irradiation simulation equipment The device can simulate continuous energy spectrum in the wavelength range of 5 to 2 (1) nm, as shown. Curve 1 agrees.
Polyimide Light Absorbing Coatings Stress and Strain Curves 3.2 Vacuum Ultraviolet Irradiation of Polyimide Light Absorbing Coatings Polyimide has heat resistance, low temperature resistance, radiation resistance, low thermal expansion, good mechanical properties and dielectric properties A series of excellent properties such as performance have been widely used in the aerospace field. The author used a simulator to simulate the VUV irradiation in real space. The VUV+ solar irradiation (wavelength 200~2500nm) was used to irradiate the polyimide light-absorbing coating, and its mechanical properties were observed. The irradiating conditions used were: vacuum ultraviolet irradiation was a one-year dose, and the vacuum ultraviolet ten sun irradiation time was 1 hour. The mechanical properties were tested on a low temperature tensile tester, and the working temperature was 300 Pa and the vacuum degree of 77K. The test results show (see) that vacuum ultraviolet irradiation has a certain influence on the mechanical properties of the coating. When the temperature changes from 300 to 77K, the yield strength and breaking strength of the material increase sharply, indicating that vacuum ultraviolet irradiation and temperature alternation have a significant effect on the tensile properties of the material. This must be considered when designing and manufacturing spacecraft light absorbing coatings.
In addition, the author also used the equipment to study the effects of vacuum ultraviolet radiation damage on various spacecraft materials such as MoS2 lubricity coatings, quartz glass, solar cells, silicone rubber, polyethylene films, and rubber films. The results of the experimental studies show that the effect of vacuum ultraviolet irradiation on various space materials, especially polymer materials, cannot be ignored. In order to understand the damage effect of vacuum ultraviolet radiation on space materials, we must further study its damage mechanism and propose effective measures to provide basis for the design, manufacture and selection of space materials.
Designed specifically for pMDI use where the crimp Height is measured from the valve shoulder to the point in which the diameter of the crimped valve = 19.0 mm.
· Crimp height reading +/- 0.01mm
· Digital Readout
· RS232 Interface optional
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