Waveguide Dielectric Gas Replacement for Breakdown-Resistant Radiotherapy

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Solution Overview

Problem

High-power microwave systems in radiation therapy machines face electrical breakdown issues due to high electric fields within waveguides, which sulfur hexafluoride (SF6) gas, used as a dielectric, is not environmentally friendly and has a high global warming potential.

Innovation Solution

The use of alternative dielectric gases such as 2,3,3,3-tetrafluoro-2-(trifluoromethyl) propanenitrile (NOVEC™ 4710) and 1,1,1,3,4,4,4-heptafluoro-3-(trifluoromethyl)-2-butanone (NOVEC™ 5110) in waveguides, which have lower environmental impact and can operate at high pressures, reducing the likelihood of electrical breakdown.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If sulfur hexafluoride (SF6) gas is used as a dielectric gas in waveguides, then electrical breakdown is reduced, but environmental harm increases due to high global warming potential

Engineering Contradiction:

Improveelectrical breakdown resistanceVSAvoidenvironmental harm

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical composition parameter of the dielectric gas from SF6 to alternative gases such as NOVEC 4710 and NOVEC 5110. These alternative gases maintain the necessary dielectric properties to prevent electrical breakdown while having significantly lower global warming potential, thus resolving the contradiction between reliability and environmental harm

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs alternative dielectric gases that can be easily replenished and replaced compared to SF6. While the individual gas molecules have shorter atmospheric lifetimes, the system uses readily available alternative gases that can be quickly replenished, maintaining operational reliability while reducing environmental accumulation

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Object-affected harmful factors

If alternative dielectric gases (NOVEC 4710/5110) are used instead of SF6, then environmental harm is reduced, but the ability to prevent electrical breakdown may be compromised

Engineering Contradiction:

Improveenvironmental harmVSAvoidelectrical breakdown resistance

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent carefully selects alternative gases with specific physical and chemical parameters that match or exceed SF6 performance. NOVEC 4710 and 5110 were chosen because their dielectric strength, electronegativity, and other relevant parameters are optimized to prevent electrical breakdown while reducing environmental harm

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent may use composite gas mixtures containing alternative dielectric gases combined with carrier gases. This composite approach allows optimization of both protective performance (electrical breakdown resistance) and environmental properties by balancing the characteristics of different gas components

Inventive Principle:

Principle #40Composite materials

3Reliability

If waveguides operate at high pressures with alternative dielectric gases, then electrical breakdown is reduced, but device complexity increases due to pressure management requirements

Engineering Contradiction:

Improveelectrical breakdown resistanceVSAvoidpressure management system

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies high pressure selectively in specific waveguide sections where electrical breakdown risk is highest, rather than uniformly across the entire microwave network. This partial application of high pressure reduces the need for complex pressure management systems throughout the entire device

Inventive Principle:

Principle #16Partial or excessive action

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

These gases effectively reduce the risk of electrical breakdown in high-power microwave systems while offering a lower environmental footprint compared to SF6, enabling the operation of radiation therapy machines with reduced greenhouse gas emissions.

Implementation Method 1

The dielectric gas may be used to reduce and/or prevent the likelihood of and/or impact from electrical breakdown in the waveguides

Methodology Applied

Scientific EffectDielectric: Dielectric

Implementation Method 2

Electric fields inside the hollow waveguides such as those mentioned above may be relatively high. The dielectric gas may be used to reduce and/or prevent the likelihood of and/or impact from electrical breakdown in the waveguides

Methodology Applied

Scientific EffectElectrical breakdown: Avalanche Breakdown

Data Source

PatentUS20240325992A1Microwave networks, waveguides, mixing carts, methods of supplying gas, and gas management systems for radiation therapy machines

Publication Date: 2024.10.03 VARIAN MEDICAL SYSTEMS INC

AI summary

A microwave network for a radiation therapy machine having a microwave source and a linear accelerator, includes a waveguide configured to connect between the microwave source and the linear accelerator. The waveguide contains at least one of a first gas or a second gas, the first gas being 2,3,3,3-tetrafluoro-2-(trifluoromethyl) propanenitrile and the second gas being 1,1,1,3,4,4,4-heptafluoro-3-(trifluoromethyl)-2-butanone.