Charged Particle Beam Evacuation Structure
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Solution Overview
Problem
In charged particle beam devices, non-evaporable getter pumps can scatter fine particles into the vacuum chamber when opened to the atmosphere, potentially damaging the electron source due to electrical discharges.
Innovation Solution
A structured evacuation system is implemented, including a non-evaporable getter pump positioned between the vacuum chamber and the main vacuum pump, with a coarse evacuation port and air introducing guide to direct air flow towards the main vacuum pump, preventing fine particles from entering the vacuum chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a non-evaporable getter pump is disposed in the vacuum piping between the vacuum chamber and the main vacuum pump, then the vacuum degree in the vacuum chamber can be improved, but fine particles of the getter material may be scattered into the vacuum chamber when the vacuum chamber is opened to the atmosphere
Solution Approach 1:
A coarse evacuation port is introduced as an intermediary component between the vacuum chamber and the non-evaporable getter pump. This port includes a coarse evacuation valve that can be opened to allow air to enter the vacuum chamber during evacuation, creating a controlled intermediate evacuation path that prevents direct air flow through the getter pump, thereby preventing fine particle scattering while maintaining vacuum functionality
Solution Approach 2:
The evacuation system is segmented into multiple independent paths: a main evacuation path through the non-evaporable getter pump for achieving high vacuum, and a separate coarse evacuation path through the coarse evacuation port for initial evacuation and opening to atmosphere. This segmentation allows each path to serve its specific function without interfering with the other, preventing fine particle scattering while maintaining vacuum capability
2Ease of operation
If the vacuum chamber is opened to the atmosphere, then maintenance and sample replacement can be performed, but air flow may scatter fine particles from the non-evaporable getter pump into the vacuum chamber
Solution Approach 1:
The coarse evacuation port acts as an intermediary that allows controlled air entry during chamber opening for maintenance. By opening the coarse evacuation valve, air enters through this dedicated path rather than flowing directly through the getter pump, enabling maintenance accessibility while preventing fine particle scattering into the vacuum chamber
3Reliability
If fine particles adhere to the electron source electrode, then electrical discharge occurs during electron emission, but the electron source can be protected by proper evacuation system design
Solution Approach 1:
The coarse evacuation port and valve are designed to preemptively prevent fine particle scattering before it can occur. By providing an alternative air entry path during evacuation and chamber opening operations, the system proactively eliminates the condition that would lead to fine particle adhesion on the electron source, thereby preventing electrical discharge and protecting electron source stability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively captures fine particles at the main vacuum pump, reducing the likelihood of them re-entering the vacuum chamber during evacuation, thus protecting the electron source and maintaining a stable vacuum environment.
Implementation Method 1
Active gas remaining in vacuum is decomposed on a surface of the getter material, and oxide, nitride, and carbide are formed with the getter material and chemically adsorbed.
Implementation Method 2
a main vacuum pump which is connected via the vacuum piping and evacuates the inside of the vacuum chamber
Implementation Method 3
a coarse evacuation port which is connected to at a position between the vacuum chamber and the non-evaporable getter pump in the vacuum piping
Data Source
AI summary
An evacuation structure of a charged particle beam device includes: a vacuum chamber provided with a charged particle source; vacuum piping connected to the vacuum chamber; a main vacuum pump which is connected via the vacuum piping and evacuates the inside of the vacuum chamber; a non-evaporable getter pump disposed at a position between the vacuum chamber and the main vacuum pump in the vacuum piping; and a coarse evacuation port connected at a position between the vacuum chamber and the non-evaporable getter pump in the vacuum piping The coarse evacuation port includes: a coarse evacuation valve that opens and closes the coarse evacuation port; and a leak valve to open the vacuum chamber to the atmosphere.