Medical Linac RF Vacuum Circulator With Pressurized Nitrogen Waveguides
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Solution Overview
Problem
Current medical linear accelerators rely on sulfur hexafluoride (SF6) gas to prevent arcing in radio frequency waveguide structures, which is environmentally damaging and has leakage issues, necessitating costly recovery systems.
Innovation Solution
A vacuum-based RF system for medical linear accelerators, utilizing a circulator operating in a vacuum state and non-reactive gases like nitrogen (N2) at varying pressures to reduce or prevent arcing, with regulators maintaining specific pressure differentials across components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sulfur hexafluoride (SF6) gas is used to prevent arcing in RF waveguide structures, then arcing prevention is improved, but environmental damage and gas leakage issues worsen
Solution Approach 1:
The patent replaces SF6 gas with nitrogen gas to create an inert atmosphere that prevents arcing in RF waveguide structures. Nitrogen is used at elevated pressures (e.g., 2-5 atm) to provide dielectric strength comparable to SF6 while being environmentally benign and non-toxic, thus eliminating the harmful environmental effects associated with SF6 leakage.
Solution Approach 2:
The patent changes the pressure parameter of the nitrogen gas from atmospheric pressure to elevated pressures (2-5 atm) to achieve the necessary dielectric strength for arcing prevention. This parameter change allows nitrogen to replace SF6 effectively by compensating for its lower dielectric strength at atmospheric pressure through increased pressure.
2Reliability
If sulfur hexafluoride (SF6) gas is used to prevent arcing, then arcing prevention is improved, but gas leakage and recovery system costs worsen
Solution Approach 1:
The patent employs nitrogen gas, which is abundant, inexpensive, and does not require recovery systems. Unlike SF6 which requires complex recovery and recycling infrastructure, nitrogen can be continuously supplied from standard gas cylinders or generation systems, eliminating the need for costly recovery equipment and simplifying the overall system architecture.
3Reliability
If vacuum state is used in circulator to prevent arcing, then arcing prevention is improved, but system complexity increases
Solution Approach 1:
The patent segments the RF system into distinct pressure zones: the circulator operates under vacuum to prevent internal arcing, while the waveguides operate at elevated nitrogen pressure to prevent external arcing. This segmentation allows each component to operate in its optimal environment, with vacuum pumps only needed for the circulator rather than the entire system.
Solution Approach 2:
The patent uses nitrogen gas as an intermediary medium in the waveguides to transfer RF energy while preventing arcing. The nitrogen at elevated pressure acts as a dielectric barrier, allowing the system to avoid vacuum conditions in the waveguides while still preventing arcing, thus reducing the need for vacuum pumps in those sections.
4Object-affected harmful factors
If non-reactive gas like nitrogen is used instead of SF6, then environmental impact is reduced, but dielectric strength may be insufficient at atmospheric pressure
Solution Approach 1:
The patent changes the pressure parameter of nitrogen gas from 1 atm to elevated pressures (2-5 atm) to achieve the necessary dielectric strength. This parameter change compensates for nitrogen's lower dielectric strength at atmospheric pressure, enabling it to replace SF6 effectively while maintaining arcing prevention capabilities.
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 approach effectively reduces arcing without SF6, minimizing environmental impact and production costs by using existing components with added vacuum pumps, maintaining a vacuum state in critical areas.
Implementation Method 1
a vacuum pump configured to generate a vacuum state inside the component
Implementation Method 2
The vacuum pump may be configured to generate the vacuum state to act as an insulator to reduce arcs within the radio frequency system
Data Source
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AI summary
A radio frequency system (900) for a radiation therapy machine includes a first portion containing a first gas (906a) at a first pressure, a second portion containing a second gas (906b) at a second pressure, the second gas being different from the first gas, and a component (904) between the first portion and the second portion, the component containing the first gas at the first pressure.