Dual RF Source Proton Linac for Rapid Energy Settling
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Solution Overview
Problem
Existing proton linear accelerator systems for cancer therapy face challenges in rapid beam energy control and stability, leading to prolonged treatment times and increased risk of patient movement during treatment due to the need for extensive settling times after energy adjustments, which can be exacerbated by unreliable actuation systems and frequent foil replacements.
Innovation Solution
A proton linear accelerator system utilizing two distinct RF energy sources, one for acceleration and another for temperature compensation, allows for higher RF pulse rates and reduced settling times by providing RF energy during both the on-time and off-time of the proton beam operating cycle, enabling more precise control over beam energy and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a single RF energy source is used for proton beam acceleration, then the system is simpler and less expensive, but the settling time after energy adjustments is prolonged and treatment efficiency is reduced
Solution Approach 1:
The single RF energy source is divided into two separate RF energy sources: a first RF energy source for providing RF energy during the on-time of the proton beam operating cycle for acceleration, and a second RF energy source for providing RF energy during the off-time for temperature compensation. This segmentation allows independent optimization of each source's function, reducing settling time while managing system complexity.
Solution Approach 2:
The system implements periodic RF energy provision with distinct on-time and off-time phases. During on-time, the first RF source provides acceleration energy; during off-time, the second RF source provides temperature compensation energy. This periodic action enables rapid energy adjustments and reduces settling time by pre-warming the cavity and compensating for temperature fluctuations between pulses.
2Productivity
If RF pulse rate is increased to reduce treatment time, then productivity improves, but beam stability deteriorates due to insufficient temperature compensation
Solution Approach 1:
The system maintains continuous useful action by providing RF energy during both on-time and off-time of the proton beam operating cycle. The first RF source provides continuous acceleration during on-time, while the second RF source provides continuous temperature compensation during off-time. This continuous action ensures beam stability even at high pulse rates, as the cavity temperature is constantly managed and ready for the next pulse.
Solution Approach 2:
The system implements feedback control where the second RF energy source compensates for temperature changes in the cavity based on the thermal effects from the first RF source. This feedback mechanism maintains constant cavity temperature and beam energy stability, enabling higher RF pulse rates without sacrificing beam quality or treatment precision.
3Measurement precision
If degrading absorbers (foils) are used for fine energy adjustment, then beam energy control precision improves, but system reliability deteriorates due to foil replacement requirements
Solution Approach 1:
The system replaces the mechanical foil insertion system with an electromagnetic field-based energy control mechanism. Instead of physically inserting degrading absorbers to adjust beam energy, the system uses RF energy sources to precisely control the electromagnetic field in the cavity, which in turn controls the proton beam energy. This substitution eliminates mechanical wear and replacement requirements while maintaining or improving energy control precision through electronic regulation.
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 reduces treatment time, enhances beam stability, and minimizes the risk of patient movement by allowing for faster energy adjustments and more accurate control of the Bragg peak, while also reducing the cost and complexity of the RF source requirements.
Implementation Method 1
a first RF energy source for providing RF energy during operation... to provide RF energy from the first RF energy source during the on-time of the proton beam operating cycle for changing the energy of the proton beam
Implementation Method 2
to provide RF energy from the second RF energy source during the off-time of the proton beam operating cycle for increasing or maintaining the temperature of the cavity
Implementation Method 3
at least one cavity extending from the proton beam input to the proton beam output, for receiving RF energy from the first and/or second energy source, and for coupling the RF energy to the proton beam as it passes from the beam input to the beam output
Data Source
AI summary
Proton beams are a promising alternative to X-rays for therapeutic purposes because they may also destroy cancer cells, but with a greatly reduced damage to healthy tissue. The energy dose in tissue may be concentrated at the tumor site by configuring the beam to position the Bragg Peak proximate the tumor. The longitudinal range of a proton beam in tissue is generally dependent upon the energy of the beam. However, after switching energies, the proton-beam system requires some time for the beam energy to stabilize before it may be used for therapy. A proton linear accelerator system is provided for irradiating tissue with an improved beam energy control, configured to provide RF energy from a first RF energy source during the on-time of the proton beam operating cycle for changing the energy of the proton beam, and to provide RF energy from a second distinct RF energy source during the off-time of the proton beam operating cycle for increasing or maintaining the temperature of the cavity. Each RF source is operated independently, allowing higher RF pulse rates to reach the cavity, supporting a smaller time between proton beam energy pulses. In addition, the peak power requirements for the second RF energy source may, in general, be less than for the second RF energy source, allowing a less costly type to be used for the second source. The use of a first and second RF source may reduce the cavity settling time from minutes to less than 10 seconds.