Temperature affects gas behavior in vacuum systems by influencing the kinetic energy and movement of gas molecules. The behavior of gas molecules in a vacuum is described by the kinetic theory of gases, which states that gas molecules are in constant motion and their behavior is influenced by factors such as temperature, pressure, and volume.

When the temperature of a gas in a vacuum system increases, the average kinetic energy of the gas molecules also increases. This increase in kinetic energy leads to an increase in the speed and movement of the gas molecules. As a result, the gas molecules collide more frequently and with greater force, exerting a higher pressure on the walls of the vacuum chamber.

Conversely, when the temperature decreases, the average kinetic energy of the gas molecules decreases. This decrease in kinetic energy causes the gas molecules to move more slowly and collide less frequently. As a result, the pressure exerted by the gas on the walls of the vacuum chamber decreases.

The relationship between temperature and gas behavior in a vacuum system is described by the ideal gas law, which states that the pressure of a gas is directly proportional to its temperature when the volume and the number of gas molecules are constant.

It is important to note that in a vacuum system, the behavior of gas molecules is also influenced by other factors such as pressure and volume. Changes in temperature can affect the pressure and volume of the gas, which in turn can impact the behavior of the gas molecules.

Overall, temperature plays a crucial role in determining the behavior of gas molecules in vacuum systems, influencing their speed, frequency of collisions, and pressure exerted on the system walls.

Sources: HyperPhysics: Ideal Gas Law](http://hyperphysics.phy-astr.gsu.edu/hbase/Kinetic/idegas.html

https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Physical_Properties_of_Matter/States_of_Matter/Gases/Kinetic_Theory_of_Gases

Back migration in vacuum systems can be caused by several factors:

1. Leaks: One of the main causes of back migration is leaks in the vacuum system. Even small leaks can allow gas molecules from the external environment to enter the vacuum chamber, leading to an increase in pressure and reduced vacuum effectiveness. Leaks can occur at various points in the system, including seals, gaskets, valves, and connections.
2. Temperature changes: Changes in temperature can also cause back migration. When the temperature inside the vacuum chamber increases, the gas molecules inside gain energy and can escape back into the external environment. Similarly, when the temperature decreases, gas molecules from the external environment can enter the chamber.
3. Outgassing: Outgassing refers to the release of gases from materials used in the vacuum system. Some materials, especially those with high vapor pressure, can release gas molecules over time. These gas molecules can migrate back into the chamber, increasing the pressure.
4. Residual gases: Even after thorough evacuation, there are often residual gases present in the vacuum system. These gases can be difficult to remove completely and can contribute to back migration.

To prevent back migration, it is important to design vacuum systems with proper seals, gaskets, and valves to minimize leaks. Regular maintenance and monitoring of the system are also crucial to identify and address any potential sources of back migration. Techniques such as bake-out and degassing can be used to remove trapped gases from the system.

Source: https://www.lesker.com/newweb/vacuum_technology/vacuum_technology_handbook/vacuum_system_design.asp