RF Ion Source Electron Dump for Window Protection

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Solution Overview

Problem

Radio Frequency (RF) driven ion sources experience localized heating and stress on the dielectric window due to back-streaming electron bombardment, leading to potential cracking or breaking, which reduces the lifetime of the window.

Innovation Solution

Incorporating a back-streaming electron dump, typically a dielectric tube affixed to a metal plug, positioned at the center of the ion source chamber window to capture and redirect back-streaming electrons, preventing them from striking the window.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If an external planar antenna is used to drive the ion source, then the antenna lifetime is improved compared to internal antennas, but the dielectric window is subjected to back-streaming electron bombardment causing localized heating and stress that leads to cracking or breaking

Engineering Contradiction:

Improveantenna lifetimeVSAvoidwindow reliability

Core Design Contradiction:

Duration of action of stationary objectVSReliability

Solution Approach 1:

A beam dump component is introduced as an intermediary element between the plasma chamber and the dielectric window. This beam dump intercepts back-streaming electrons before they reach the window, acting as a protective mediator that absorbs the harmful electron bombardment and prevents localized heating and stress accumulation on the window surface.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The harmful back-streaming electrons that would otherwise damage the dielectric window are redirected onto a dedicated beam dump structure. By converting the harmful electron flux into a controlled deposition on a sacrificial component, the window is protected from damage while the electrons continue to serve their plasma interaction function.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Productivity

If the dielectric window is exposed to back-streaming electron bombardment, then plasma generation is maintained, but localized non uniform heating occurs inducing localized stresses that lead to cracking or breaking

Engineering Contradiction:

Improveplasma generationVSAvoidlocalized heating

Core Design Contradiction:

ProductivityVSTemperature

Solution Approach 1:

The beam dump serves as an intermediary heat sink that intercepts back-streaming electrons before they deposit energy onto the dielectric window. This mediator component absorbs the thermal energy from electron bombardment, preventing localized temperature rise and thermal stress on the window while allowing plasma generation to continue uninterrupted.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If the dielectric window is exposed to back-streaming electron bombardment, then plasma generation is maintained, but localized stresses accumulate over time leading to cracking or breaking

Engineering Contradiction:

Improveplasma generationVSAvoidwindow strength

Core Design Contradiction:

ProductivityVSStrength

Solution Approach 1:

The beam dump acts as a protective intermediary that absorbs back-streaming electrons and prevents them from impacting the dielectric window. By intercepting the electron flux, the beam dump eliminates the accumulation of localized stresses on the window, maintaining window strength and structural integrity over extended operational periods while plasma generation continues.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The electron dump effectively prevents localized heating on the window, enhancing the ion source's operational lifetime without interfering with plasma formation or ion beam extraction.

Implementation Method 1

the inner surface of the quartz window is subject exposure to back-streaming electron bombardment

Methodology Applied

Scientific EffectElectron bombardment: Electron Beam

Implementation Method 2

RF energy is coupled to the gas using an RF antenna

Methodology Applied

Scientific EffectRadio Frequency energy coupling: Electromagnetic Induction

Implementation Method 3

RF energy applied to the gas to form a plasma

Methodology Applied

Scientific EffectPlasma formation: Plasma

Implementation Method 4

coupled to the plasma through a dielectric window, such as a quartz window

Methodology Applied

Scientific EffectDielectric properties: Dielectric

Data Source

PatentUS8729806B2RF-driven ion source with a back-streaming electron dump

Publication Date: 2014.05.20 RGT UNIV OF CALIFORNIA

AI summary

A novel ion source is described having an improved lifetime. The ion source, in one embodiment, is a proton source, including an external RF antenna mounted to an RF window. To prevent backstreaming electrons formed in the beam column from striking the RF window, a back streaming electron dump is provided, which in one embodiment is formed of a cylindrical tube, open at one end to the ion source chamber and capped at its other end by a metal plug. The plug, maintained at the same electrical potential as the source, captures these backstreaming electrons, and thus prevents localized heating of the window, which due to said heating, might otherwise cause window damage.