The limit and the choice of the vacuum system depend on the choice and the design of vacuum pump components, care, fabrication and cleaning techniques.

Here are some common methods for creating a vacuum:

1. Mechanical Vacuum Pumps: Mechanical vacuum pumps are widely used to create vacuums in various applications. The most common type is the rotary vane pump, which uses rotating vanes to trap and remove gas molecules from a chamber. Other types of mechanical pumps include diaphragm pumps, scroll pumps, and Roots blowers. These pumps work by mechanically compressing and displacing gas molecules to lower the pressure in the system.

2. Turbomolecular Pumps: Turbomolecular pumps are high-speed pumps that achieve high vacuum levels. They use a series of rotating blades or rotors to accelerate gas molecules, creating a pressure gradient and pumping action. Turbomolecular pumps are typically used in conjunction with mechanical pumps to achieve ultra-high vacuum levels.

3. Cryogenic Pumps: Cryogenic pumps utilize low temperatures to condense and trap gases, effectively creating a vacuum. They rely on the cooling effect of cryogenic fluids, such as liquid nitrogen or helium, to freeze and capture gas molecules. Cryopumps and cryogenic traps are examples of cryogenic pumps used to achieve high and ultra-high vacuum levels.

4. Ion Pumps: Ion pumps operate by creating and maintaining an electric field within a vacuum chamber. The electric field ionizes gas molecules, and the resulting ions are attracted to electrodes, effectively removing them from the system. Ion pumps are commonly used in ultra-high vacuum applications.

5. Vacuum Chambers and Valves: Creating a vacuum can also involve using a sealed chamber and a combination of valves and pumps to evacuate the air. The chamber is sealed, and the valves are used to control the flow of gas in and out of the chamber. Vacuum pumps are then employed to remove the air from the chamber until the desired vacuum level is reached.

It’s important to note that creating and maintaining a vacuum requires proper sealing of the system, careful selection of pumps and valves, and appropriate monitoring of pressure levels. The specific method used to create a vacuum depends on factors such as the desired level of vacuum, the nature of the application, and the available resources and equipment.

Throughput

In any vacuum system, it is necessary to define the measure of the rate of flow of gas. The quantity of gas is a measure of molecules in a gas; it is the product of pressure and volume. The rate of gas flow is called through put.

Through-put is thus defined as  the quantity of gas at a specified  time  and temperature  passing  through an open  cross- sectional area  of the vacuum system per  unit area . Thus:

Throughput Q   =   P V  Torr  liters / sec

                                        T

Where   P = pressure (Torr)

             V= volume (volume)

              T = time (sec)