Module 6: Gas Sources

Description: Identifies sources of gases that must be removed in a vacuum system.

Length of Time: 2 hours

Topics:

1. Volume gas

2. Surface gas

3. Leaks

a. Real leaks

b. Virtual leaks

c. Rate-of-rise

4. Contaminants

5. Bulk gases

6. Permeation

7. Outgassing and contaminants

8. Materials in a vacuum system

 

Student Objectives:

Student will be able to:

1. Define: volume gas.

2. Define: surface gas.

3. Define: monolayers.

4. Give examples of where volume gases, surface gases, and monolayers occur in a vacuum system.

5. Relate surface gas composition variations to pumping time.

6. Define the terms: real leaks and virtual leaks.

7. Identify common sources of virtual leaks in vacuum systems and describe appropriate preventative measures.

8. Define the term: rate-of-rise.

9. Given pressure versus time data, construct a log-log graph describing rate-of-rise.

10. Define "outgassing."

11. Identify materials that are the major sources of outgassing in vacuum systems.

12. Describe the effects of outgassing and contamination on vacuum system performance.

13. Define "bulk gases" and describe the effect of bulk gases on vacuum system performance.

14. Describe the process of gas permeation and its effect on ultrahigh vacuum systems.

 

References:

O’Hanlon: Chapter 4 "Gas Release from Solids"