Dynamic RF Voltage Control for Synchrotron Beam Stop Time
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Solution Overview
Problem
The existing charged particle beam irradiation systems face challenges in shortening the stop time of the extracted beam while minimizing momentum dispersion, which can lead to dose deviations due to increased synchrotron oscillation frequency caused by elevated acceleration radio frequency voltage.
Innovation Solution
A charged particle beam irradiation system with a controller that adjusts the acceleration radio frequency voltage amplitude during beam extraction and deactivation, increasing it to shorten the stop time and reducing it to suppress momentum dispersion, thereby maintaining precise dose delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the acceleration radio frequency voltage amplitude is increased to shorten the stop time of the extracted beam, then the stop time is reduced, but the momentum dispersion increases causing dose deviations
Solution Approach 1:
The acceleration radio frequency voltage amplitude is made dynamic rather than static. The controller adjusts the voltage amplitude in real-time based on the operational state: using a first amplitude value during beam extraction and a second amplitude value (higher than the first) during beam deactivation. This dynamic adjustment allows the system to optimize for different functional requirements at different times, resolving the contradiction between stopping speed and dose precision.
Solution Approach 2:
The system changes the parameter of acceleration radio frequency voltage amplitude based on operational conditions. By switching between two distinct amplitude values (first amplitude value for extraction, second higher amplitude value for deactivation), the system can control synchrotron oscillation frequency appropriately for each phase, thereby achieving both short stop time and maintained dose precision.
2Loss of time
If the synchrotron oscillation frequency is increased to shorten the stop time, then the stop time is reduced, but the momentum dispersion of the beam increases
Solution Approach 1:
The synchrotron oscillation frequency is controlled dynamically through adjustment of the acceleration radio frequency voltage amplitude. During deactivation, the higher amplitude value increases the oscillation frequency to rapidly stop the beam. During extraction, the lower amplitude value maintains appropriate oscillation frequency for stable beam composition. This dynamic control resolves the contradiction between stopping speed and momentum stability.
Solution Approach 2:
The system changes the acceleration radio frequency voltage amplitude parameter to control synchrotron oscillation frequency. By using a second amplitude value (higher than the first) during deactivation, the system increases oscillation frequency to shorten stop time. By switching to the first amplitude value during extraction, the system maintains lower oscillation frequency to preserve beam momentum stability.
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 shortens the charged particle beam stop time while minimizing momentum dispersion, ensuring accurate and targeted irradiation by controlling the acceleration radio frequency voltage amplitude, reducing extra irradiation and maintaining dose precision.
Implementation Method 1
an accelerating cavity for accelerating the charged particle beam with a radio frequency acceleration voltage up to a predetermined energy level
Implementation Method 2
increasing the amplitude of betatron vibrations of an orbiting charged particle beam by application of an extraction radio frequency voltage for extraction starting with particles having amplitudes exceeding a stability limit condition
Implementation Method 3
from the time the extraction radio frequency voltage is turned off until the extracted charged particle beam is actually cut off, there elapses a time period corresponding to the synchrotron oscillation period of the orbiting charged particle beam
Data Source
AI summary
At the start of beam extraction, the amplitude value of an acceleration radio frequency voltage is held at a first amplitude value. When the irradiation dose stemming from beam extraction reaches a prescribed dose, the amplitude value of the acceleration radio frequency voltage applied to an accelerating cavity starts to be increased from the first amplitude value to a second amplitude value. When the irradiation dose reaches a target dose, the amplitude value is raised to and held at the second amplitude value. By the time the irradiation is restarted, the amplitude value of the acceleration radio frequency voltage applied to the accelerating cavity is reduced from the second amplitude value to the first amplitude value. At the start of beam extraction, the amplitude value is held at the first amplitude value.