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  • Data Analysis of Advantages of Turbomolecular Pumps
    May 21, 2018

    As turbomolecular pumps perform better than cryogenic pumps, ion pumps, and diffusion pumps in some aspects. It is used under most normal circumstances.

    (1) Clean without oil vapor reflux

    The turbomolecular pump can be operated in accordance with the operating procedures without using any trap, and it can provide an extremely clean vacuum environment that contains any hydrocarbons for the pumped container. Modern turbomolecular pumps rarely use oil to lubricate except for large pumps, most small pumps use grease-lubricated bearings, some small pumps also use air bearings, but magnetic bearings are used more often. In recent years, there have been many dry-type backing pumps, so that the turbomolecular pump system does not exist oil vapor reflux, which makes it a truly clean dry-type high vacuum pump (Figure 4).


                                           Ultimate Pressure: 2×10-7 Pa

    Figure 4 Typical Spectrogram of Residual Gas of the Turbomolecular Pump

    Figure 4 shows that the there is no hydrocarbons in turbomolecular pump system, 17 and 18 on the curve refers to OH+ and H2O+.

    (2) Easy to use

    In many applications, turbomolecular pumps do not need high vacuum valves or rough vacuum valves. It can run just by simply pressing the push button and reduce to the ultimate pressure from atmospheric pressure. This system can be rough pumped by a turbomolecular pump and the pump can be accelerated to the operating speed directly, which eliminates the need for vacuum components such as valves, pipes, traps, and valve controllers, as well as the failure of these components. Therefore, the turbomolecular pump system occupies a small space, and the installation direction of it is not limited. So the pump can be installed in any direction (Excluding oil-lubricated pump which can only work within a vertical range of ±5°). With this feature, the turbomolecular pump can be used where the installation location is limited.

    (3) Strong gas transmission capability

    Most turbomolecular pumps have good capability of delivering light gases such as hydrogen and helium, so it is very suitable for process operations under ultra-high vacuum, such as those rich-hydrogen processes, helium mass spectrometer leak detectors and other applications. There are some turbo molecular pumps specifically designed for pump corrosive gases, they are suitable for etching, reactive ion etching, ion beam processing, low pressure chemical vapor deposition, epitaxy, ion implantation and other processes. And in these processes, the pumped gas can corrode cryogenic pumps, ion pumps, and diffusion pump oils. It even destroys the standard but unprotected turbomolecular pump. Since the turbo molecular pump is a kind of transmission pump, the pumped gas can pass through it without accumulation in pump. It is therefore suitable for high gas load processes, such as sputtering, etching and so on.

     (4) Suitable for ultra-high vacuum applications

    A good sealed and degassed turbomolecular pump with a well-performing two-stage rotary vane pump (or a dry pre-stage pump with the same performance) can have an ultimate vacuum of typically 10-9 to 10-10 Torr (ie, Between 133.3 and 13.33 nPa). If a turbo molecular pump is connected with another good sealed and degassed turbo molecular pump in series, the ultimate pressure of it is generally between 1×10 −10 and 1×10 −11 Torr (ie, between 13.33 and 1.333 nPa). Unlike cryogenic pumps or ion pumps, turbomolecular pumps can operate at full pump speeds under ultra-high vacuum conditions. These properties as well as its good cleanliness (no hydrocarbon), clearly the user will choose turbomolecular pumps for high-resolution mass spectrometers, molecular beam epitaxy devices, ultra-high vacuum analytical instruments and other equipments.

     (5) Good performance under high pressure

    Inlet pressures of some turbomolecular pump can operate between 10-1 and 10-3 Torr (ie, 13.33 Pa and 133.3 mPa). The ion pump cannot be used in this pressure range, for diffusion pump, the operation is becomes unstable.

     (6) Short cycling time

    Most turbomolecular pumps, especially those smaller ones, typically take 1~3 minutes to reach normal operating speeds. And there are small difference between different types and models of pumps. The turbomolecular pump can be immediately turn off and exposed to the atmosphere. This fast cycling feature is useful in sample input systems, especially for hand-held leak detectors.

    (7) Long service time

    In some applications, the turbomolecular pump has a longer service life than other pumps. Because the heavy gas load and valve leakage leads to the occasional regeneration or repair of the cryogenic pump. Besides,the turbo molecular pump can also eliminate the contamination of the vacuum chamber due to the pump oil.