A method for raising and maintaining the vacuum degree of a vacuum chamber

Abstract

The invention relates to a method for increasing and maintaining a vacuum degree of a vacuum chamber by refrigerating a molecular sieve by the aid of a TEC (thermoelectric cooler). The vacuum chamber is vacuumized to a reachable final vacuum degree at least more than 10 E-3 mbar; the TEC is energized, and a TEC cold end can refrigerate the molecular sieve to a reachable limit low temperature; the gas adsorption capacity is increased exponentially, and residual air in the vacuum chamber and gases volatilized by vacuum parts can be strongly absorbed after the molecular sieve is deeply refrigerated; and the vacuum degree can be maintained in a level of 10 E-6 mbar and can be maintained for a long time after a pump port valve of the vacuum chamber is closed. According to the method, the molecular sieve is taken as a gas adsorbent, and the lower the molecular sieve temperature is, the stronger the adsorption capacity is, so that the TEC can refrigerate the molecular sieve deeply, the adsorption capacity of the molecular sieve is increased exponentially, the vacuum degree of the vacuum chamber can be effectively increased and maintained, use requirements of devices with higher vacuum degrees can be met, the size is small, the cost is low, the efficiency is high, the use is simple and convenient, and repeated use can be realized.

Description

technical field [0001] The invention is applied in the technical field of vacuum and CCD refrigeration, and in particular relates to a method for improving and maintaining the vacuum degree of a vacuum chamber by using a TEC refrigerator to refrigerate molecular sieves. Background technique [0002] In order to improve the signal-to-noise ratio of imaging signals and suppress thermal noise and dark current generated by CCD circuits, astronomical CCDs are usually cooled to below -50°C during operation, and some models of CCDs even require operating temperatures below -80°C. When designing a CCD system, according to the temperature characteristics of the CCD, the CCD is usually placed in a vacuum dewar, and deep cooling is performed using liquid nitrogen, a TEC refrigerator or a refrigerator. In order to improve refrigeration efficiency and prevent heat exchange caused by gas convection, the CCD Dewar should maintain a relatively high vacuum degree, generally above 10E-3mbar. ...

AI Technical Summary

Problems solved by technology

However, the use of ion pumps has great limitations. First of all, the requirements for vacuum Dewar are high, and the internal air release volume cannot be large. The ion pump cannot be started in the state of large air release volume. If the ion pump is forced to start, it will be scrapped quickly and irreversibly. It is very expensive and is a one-time device. After the adsorption saturation of the ion pump reaches its service life, it needs to be replaced with a new ion pump. If there is a misuse of the ion pump, it may cause damage to the ion pump. Secondly, the ion pump cannot be powered off after it is started. When the electric ion pump stops working, the ion pump will lose its adsorption effect. At this time, the wires and other components inside the Dewar will continue to volatilize and accumulate gas in a vacuum state. It has been proved by the laboratory that it only takes about 1-2 hours to detoxify. The vacuum degree of the tile will quickly drop below 10E-1mbar, reaching the state where the ion pump cannot be started. If you want to restart the ion pump to restore the Dewar working state, you need to use a vacuum pump to re-evacuate the Dewar to above 10E-6mbar to start the ion pump. Pump

This shows that the use of ion pump technology requires very harsh conditions, and the operation and maintenance costs are relatively high

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