Reusable Linac CF Choke Joint for UHV Sealing and Arc Resistance
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Solution Overview
Problem
Existing radiotherapy devices, such as linacs, face issues with arcing and damage due to imperfections in RF waveguides, leading to the need for replacing entire systems rather than just damaged components, and existing joints are not suitable for ultra-high vacuum regions or high-power instabilities.
Innovation Solution
A reusable joint design using a CF choke flange and cover flange with a gasket, shielded from high electric and magnetic fields by a choke groove and recess, allowing for attachment without brazing or welding, enabling flexible and efficient servicing and upgrading of linacs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brazed or welded connections are used to join waveguide sections, then arcing is limited and continuous smooth surfaces are achieved, but the connections become permanent and components cannot be separated for replacement or repair
Solution Approach 1:
The waveguide system is divided into separate modular sections that can be independently replaced. The reusable joint allows disconnection and reconnection of waveguide sections without damaging the components, enabling targeted replacement of damaged sections while maintaining the overall system integrity and arcing prevention characteristics.
Solution Approach 2:
A reusable joint acts as an intermediary connection between waveguide sections. This joint incorporates features to maintain surface continuity and minimize arcing while allowing for easy disconnection and reconnection, serving as a mediator that enables both reliable electrical contact and component replaceability.
2Stress or pressure
If O-ring seals are used in RF chokes, then pressurisation of the waveguide is enabled, but arcing occurs in UHV regions when VSWR varies significantly
Solution Approach 1:
Different sealing approaches are used in different regions of the waveguide system. O-ring seals are employed in regions where pressurisation is required and arcing risk is low, while alternative sealing methods or designs are used in UHV regions where arcing resistance is critical, allowing each region to have the quality needed for its specific operating conditions.
3Reliability
If CF joints are used for UHV sealing, then UHV compatibility is achieved, but the joints may be damaged or destroyed due to resonant RF frequency nodes and large surface currents in high-power environments
Solution Approach 1:
The design acknowledges the presence of high surface currents and RF fields in the operating environment rather than trying to completely eliminate them. The joint geometry and material selection are optimized to withstand these conditions, converting the potentially harmful RF environment into a manageable operating parameter that the joint is designed to tolerate.
4Object-affected harmful factors
If traditional choke mode cavities with damping dielectric material are used, then harmful RF modes are damped, but the Q factor and stored energy are much lower requiring longer accelerating structures
Solution Approach 1:
The harmful RF modes are extracted or removed from the system through carefully designed choke structures that prevent mode propagation without requiring damping dielectric material. This extraction approach maintains the Q factor and stored energy levels needed for efficient acceleration while still eliminating the harmful modes that would cause breakdown or beam breakup.
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 design allows for the reuse and repair of linac components onsite, enhancing versatility and efficiency in manufacturing and servicing, while preventing arcing and damage in high-power environments.
Implementation Method 1
A gasket is disposed between the first CF groove and the second CF groove
Implementation Method 2
The CF joint comprises a gasket held in place between two knife-edges to provide a UHV seal
Implementation Method 3
shielded from high electric and magnetic fields by a choke groove and recess, allowing for attachment without brazing or welding
Data Source
Figure 1
Figure 2~3a
Figure 3b
AI summary
A reusable joint for a medical linac, a reusable CF choke flange for a medical linac, a linac and a method for forming a reusable joint for a medical linac are disclosed. The reusable joint comprises a CF choke flange, a CF cover flange and a gasket. The CF choke flange comprises a first waveguide aperture, a choke groove and a first CF groove comprising a first knife-edge, wherein the choke groove is disposed radially inwards from the first CF groove on the CF choke flange. The CF cover flange comprises a second waveguide aperture aligned with the first waveguide aperture and a second CF groove comprising a second knife-edge and aligned with the first CF groove. The gasket is disposed between and in contact with the first CF groove and the second CF groove.