VT-203 Residual Gas Analyzers and Analysis
This day-long short course is intended for those who wish to understand the operation and use of residual gas analyzers and helium-based leak detectors. The class will be divided into several sections, beginning with background concepts needed to understand their operation; that will be followed by a description of the rga instrument; analyzing its spectra; how materials, components, and gauge location affect its results; a description of leak detectors; instrument sampling techniques, and some suggestions for their use in problem solving.Topical Outline:
- Materials in vacuum
- Seals, joints, and valves
- Rough pumping large systems
- System performance
- Multichamber systems
Attendees in this tutorial receive the text, A User’s Guide to Vacuum Technology, 3rd edition, John O’Hanlon (John Wiley & Sons, 2003).
1. Background Concepts
This section reviews the basic gas laws and gas flow concepts that are needed to understand the behavior of residual gas analyzers and leak detectors. Common terms, components, and system concepts that all participants should understand are defined and explained.
- Gas Laws
- Gas Flow Rules
- Distinguishing Mass Spectrometers and Residual Gas Analyzers (RGA)
- Helium Leak Detectors and Residual Gas Analyzers
2. Residual Gas Analyzer: Instrument and Component Parts
The two main types of mass filters: magnetic and radio frequency separation are described along with common types of ionizers and ion counters.
- Instrument Description
- Ionization Methods
- Magnetic Sector Mass Analyzer
- Quadrupole Mass Analyzer
- Detection Methods
3. Analyzing Mass Spectra
When energetic electrons bombard gases, numerous ion fragments are created. These fragments can confuse examination of the initial spectra. This section describes the ways in which fragments are created and explains the advantages and limits of using an RGA to understand an environment. Ion fragment patterns (cracking patterns) of typical materials used in a vacuum environment are described.
- Dissociative, Multiple, and Isotopic Ion Fragments
- Qualitative versus Quantitative Analysis
- Cracking Patterns of Commonly Used Gasses, Fluids, and Solids
- Practical Examples
4. Effect of Materials, Components and Gauge Location
Nearby materials can outgas fragments that may adversely affect the analysis of a system. As well, the location of the sensor and the direction in which impinging molecules arrive will affect the measured partial pressure. We examine some of these issues here.
- Permeation and Outgassing of Materials
- O-Ring Permeation and Probe Gas Time Constants
- Closed versus Open Ionization Sources
- RGA Materials of Construction
- Location of Analyzer and Local System Pumping Speeds
- Outgassing from Hot Ionizer Filaments
- Carbon Monoxide Generation from Ionizer Filaments
5. Leak Detectors
A leak detector is a portable self-contained residual gas analyzer that is optimized for use with helium sampling gas. Leak detectors can be configured to find leaks in one of several ways that best depend on the system being tested. Methods for detecting leaks will be described followed by a detailed discussion of instrument types, connection methods, and response limits.
- Need For Leak Detection
- Leak Detection Methods
- Classical versus Counter-flow Leak Detectors
- Leak Sensing Response Time and Sensitivity
- System Connection Methods
6. Sampling Techniques for RGA’s and Leak Detectors
Background gas pressure and contamination limits determine where a helium-sensitive detector is located and how it is configured. Here we examine methods and instruments for sampling at high vacuum, medium vacuum, atmospheric pressure, and pressurized components.
- Positioning an Analyzer to Sample Background Gases
- Positioning an Analyzer to Sample Process Environments
- Measuring Small Parts
- Bypass Sampling Techniques
- Detecting Leaks in Internally Pressurized Systems
- Using an RGA for Leak Detection
- Atmospheric Pressure Ionization: A Specialized Technique
7. Leak Detection Forensics
Systems are never free of problems, and as a result, systems will occasionally stop operating or produce unusable product. Having a repair strategy in place can minimize the time a system is not productive. Some ideas and examples are presented here that are intended as food for thought toward a goal of developing a local problem solving strategy.
- Diagnostic Ideas and Suggestions
- Case study I: Incorrect System Installation
- Case study II: System Maintenance Error
- Case study III: Improper System Operation
is Professor Emeritus of Electrical and Computer Engineering, the University of Arizona. He retired from IBM Research Division in 1987, where he was involved in thin-film deposition, vacuum processing, and display technology. He retired from UA in 2002, where he directed the NSF Ind./Univ. Center for Microcontamination Control. His research focused on particles in plasmas, cleanrooms, and ultrapure water contamination. He is the author of A User’s Guide to Vacuum Technology, 3rd edition. (John Wiley & Sons, 2003).
This course is currently available via:
On Location Education Program