Collision Ionization Source Duct Geometry for Gas Pressure

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Solution Overview

Problem

Existing collision ionization ion sources, such as Nano-Aperture Ionization Sources (NAIS), suffer from lower-than-expected source brightness due to gas leakage through tiny input/output apertures, resulting in a gas pressure in the ionization region that is one or more orders of magnitude lower than anticipated.

Innovation Solution

The supply duct is modified to increase gas supply rate to the ionization region by altering the duct geometry, with a transition region between the entrance and emergence orifices, where the inner height decreases from a first value to a second value, enhancing flow conductance and reducing flow resistance, thereby increasing gas pressure in the ionization region.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If tiny input/output apertures are used in NAIS, then device miniaturization is achieved, but gas leakage occurs resulting in lower gas pressure in ionization region

Engineering Contradiction:

Improveion source sizeVSAvoidgas pressure in ionization region

Core Design Contradiction:

Volume of moving objectVSQuantity of substance

Solution Approach 1:

The duct geometry transitions from a two-dimensional constant cross-section to a three-dimensional varying cross-section, with the inner height changing along the flow direction. This dimensional change allows the duct to maintain compact footprint while increasing flow conductance through strategic height variation, resolving the contradiction between miniaturization and gas pressure maintenance.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The duct's inner height parameter is varied along its length, transitioning from a first height value near the entrance to a second height value near the emergence. This parameter change optimizes the balance between maintaining small aperture sizes for miniaturization and providing sufficient flow conductance to achieve adequate gas pressure in the ionization region.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If higher gas pressure is achieved in ionization region, then source brightness increases, but higher input pressure is required

Engineering Contradiction:

Improvegas pressure in ionization regionVSAvoidinput pressure

Core Design Contradiction:

Quantity of substanceVSStress or pressure

Solution Approach 1:

The modified duct acts as an intermediary flow path that amplifies the effect of input pressure on ionization region pressure. By optimizing the duct geometry with varying inner height, the system achieves higher gas pressure in the ionization region without proportionally increasing the input pressure, effectively decoupling these two pressure parameters.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Quantity of substance

If duct length is increased to improve gas supply, then flow conductance increases, but device size increases

Engineering Contradiction:

Improvegas supply rateVSAvoidduct length

Core Design Contradiction:

Quantity of substanceVSLength of stationary object

Solution Approach 1:

Instead of uniformly increasing duct length, the invention applies local quality changes by varying the inner height at specific locations along the duct. The duct maintains a compact overall length but achieves enhanced flow conductance through localized height increases in critical regions, optimizing gas supply without increasing device footprint.

Inventive Principle:

Principle #3Local quality

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 modification results in a significant increase in source brightness, allowing for higher ionization efficiency and easier compliance with safety regulations by achieving higher gas pressure in the ionization region with lower input pressure.

Implementation Method 1

altering the duct geometry, with a transition region between the entrance and emergence orifices, where the inner height decreases from a first value to a second value, enhancing flow conductance and reducing flow resistance

Methodology Applied

Scientific EffectFlow conductance:

Implementation Method 2

Methodology Applied

Scientific EffectFlow resistance:

Implementation Method 3

achieving higher gas pressure in the ionization region with lower input pressure

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Data Source

PatentUS10325750B2Collision ionization source

Publication Date: 2019.06.18 FEI CO

AI summary

A collision ionization source is disclosed herein. An example source includes an ionization region arranged to receive a gas and a charged particle beam, the charged particle beam to ionize at least some of the gas, and a supply duct arranged to provide the gas to the ionization region, the supply duct having a non-uniform height decreasing from an input orifice to an output orifice, the output orifice arranged adjacent to the ionization region.