According to the supply method of the medium, cryopumps are divided into the following types:
Storage tank cryogenic pump: low temperature medium (liquid helium) is directly injected into the storage tank in the pump to condense the gas to achieve the purpose of pumping.
The advantages of the storage tank cryopump are that the pump is small in size, no vibration, no noise, and easy to operate.
The disadvantage of the storage tank cryogenic pump is that the operating cost is high, the use time of each filling of the low-temperature medium is short, and the vacuum system that needs to operate continuously for a long time needs to periodically replenish the working medium, and is limited by the supply conditions of the low-temperature medium.
Process cryopump: The cryopanel cooling pipe in the pump is connected to the refrigeration expander, and the cryogenic medium (gas helium) is supplied to the cryopump through the outer pipeline, absorbs the heat of the cryopanel, and then returns to the refrigeration compressor to form a closed cycle. The volume of the pump is huge, the pipeline is complicated, and the cooling loss of the pipeline is large.
The advantage of the process cryopump is that it has a large cooling power and is most suitable for removing atmospheric volume or a large vacuum chamber.
Small refrigerator cryopump: The closed-cycle small refrigerator cryopump is composed of a low temperature pump body, an air extraction cryopanel, a radiation shielding plate, a refrigerator and a compressor.
The biggest difference between the cryogenic pump of the small refrigerator and the cryogenic pump of the process is that the first and second cold heads of the refrigerator are directly connected to the radiation screen and the cold plate, and the flow in the connecting pipeline between the refrigerator and the compressor is normal temperature, high (or low) temperature. ) pressurized gas medium, there is no transportation problem of low temperature medium, and it has the advantages of process cryopump and storage tank cryopump. It is an ideal clean ultra-high vacuum pump at present.
Small refrigerator cryopumps are widely used in thin film preparation, microelectronics technology, high energy physics, small ring die equipment and other industrial fields.