HOM Coupler Beam Steering in Linear Accelerators
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Solution Overview
Problem
Higher-order resonances (HOMs) in linear particle accelerators can cause beam deflection and spreading, leading to operational inefficiencies, as existing technologies primarily focus on eliminating these modes rather than utilizing them for diagnostic and steering purposes.
Innovation Solution
Introducing asymmetric conductive probes, or HOM couplers, into the accelerating cavities to intentionally excite specific higher-order modes for beam diagnostics, alignment, and steering, allowing for on-line measurement and control of RF harmonics and beam position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If higher-order modes are inhibited to prevent beam deflection and spreading, then beam stability is improved, but the ability to perform beam diagnostics and steering is reduced
Solution Approach 1:
The patent converts the harmful effect of higher-order modes (which cause beam deflection and spreading) into a beneficial diagnostic and steering tool. By intentionally exciting specific higher-order modes through asymmetric conductive probes, the system uses these modes to obtain beam position information and perform steering functions, thereby transforming a previously problematic phenomenon into a useful resource for beam control and diagnostics.
Solution Approach 2:
The patent introduces asymmetric conductive probes as intermediary elements that couple to the higher-order modes in the accelerating cavities. These probes serve as mediators between the electromagnetic fields and the beam, enabling non-invasive measurement of beam position and control of beam steering by detecting and exciting higher-order modes without directly interacting with the main beam.
2Manufacturing precision
If conventional steering magnets are used to correct beam deflection, then beam alignment is improved, but device complexity and cost increase
Solution Approach 1:
The patent enables the accelerating cavities themselves to perform beam steering and alignment functions by utilizing higher-order modes excited through asymmetric probes. This self-service approach eliminates the need for separate external steering magnets, as the cavities' own electromagnetic fields are used to correct beam deflection and maintain alignment, thereby reducing overall system complexity.
Solution Approach 2:
The patent makes the accelerating cavities multi-functional by enabling them to perform both their primary acceleration function and secondary beam steering/diagnostics functions. By exciting higher-order modes within the same cavities used for acceleration, the system eliminates the need for separate dedicated steering devices, achieving multiple functions with a single component.
3Adaptability or versatility
If asymmetric conductive probes are introduced to excite higher-order modes, then beam diagnostics and steering capability are improved, but device complexity increases
Solution Approach 1:
The patent merges the beam diagnostics and steering functions with the existing accelerating cavity structure by introducing asymmetric conductive probes that couple to higher-order modes. Rather than adding completely separate diagnostic and steering systems, the probes are integrated into the cavity structure, combining multiple functions into a unified system that reduces overall complexity.
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
Enables non-invasive, real-time monitoring and control of beam dynamics, improving the accuracy of beam alignment and steering within the accelerator, reducing the need for external steering magnets and enhancing the overall efficiency of the accelerator system.
Implementation Method 1
the conduit uses a tuned-cavity waveguide in which a radio-frequency (rf) standing wave is established in order to accelerate the electrons
Implementation Method 2
The electrons thus always see an electrical field of the same polarity and are accelerated along the length of the accelerator
Implementation Method 3
In-situ measurement of beam-induce fields in the S-band accelerating structures of the diamond light source linac
Data Source
Figure 1a~1d
Figure 2~4
Figure 5
AI summary
A linear accelerator is disclosed, having a series of interconnected cavities through at least some of which an rf signal and an electron beam are sent, comprising at least one variable coupler projecting into a cavity of the series, a control apparatus adapted to interpret an electrical signal from the coupler and derive diagnostic information as to the electron beam therefrom, wherein the control apparatus is further adapted to vary the interaction of the at least one coupler with the rf signal in dependence on the diagnostic information. Thus, the accelerator properties can be adjusted by encouraging or inciting an Higher-Order Mode ("HOM") having a desired effect such as bunching and/or deflecting. The coupler could be rotateable, and partially or fully retractable, to allow its influence to be adjusted and/or for it to be removed from service when not needed. Several such probes could be available, approaching the cavity from different directions or at different locations, or approaching different cavities. The coupler can be asymmetric, in order to exert an appropriate influence on the cavity and provoke a useful HOM. For example, it can be elongate with at least one directional deviation, such as a hockey stick. Generally, however, the appropriate shape for the coupler will be dependent on the shape of the cavity with which it is working and the specific HOMs that are to be excited.