Ion Beam Extraction Modulation for Stable Tandem Acceleration
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Solution Overview
Problem
Conventional methods for generating epithermal neutrons for boron neutron capture therapy (BNCT) face challenges in safely managing high power proton beams, which can cause equipment damage due to excessive power density and self-space charge effects.
Innovation Solution
The system modulates a negative ion beam at the ion source by adjusting the ion extraction voltage, limiting the pulse duration to reduce average beam power and prevent equipment damage, while maintaining steady state ion beam delivery to the tandem accelerator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high beam current is used to achieve required flux density for BNCT treatment, then treatment efficacy is improved, but power density exceeds safety limits and causes equipment damage
Solution Approach 1:
The patent applies periodic pulsed operation of the ion beam, delivering high current in short bursts rather than continuous operation. The beam is modulated with pulse widths of 0.1-10 milliseconds and duty cycles of 0.1-10%, allowing the beam current to reach therapeutic levels during pulses while the average power density remains below equipment damage thresholds between pulses.
Solution Approach 2:
The patent implements dynamic control of beam parameters through rapid switching between on and off states. The beam current, pulse width, and duty cycle are dynamically adjusted based on treatment requirements and equipment thermal capacity, enabling the system to adapt between delivering maximum therapeutic flux and protecting equipment from overheating.
2Object-affected harmful factors
If beam current is reduced to protect equipment, then power density is reduced to safe levels, but flux density falls below treatment threshold
Solution Approach 1:
By using pulsed operation with high peak currents and low duty cycles, the system achieves high instantaneous flux density during pulses to meet treatment requirements, while the low average power during off-periods protects equipment from damage.
Solution Approach 2:
The system performs preliminary cooling during the off-periods between pulses, allowing equipment to dissipate heat and return to safe operating temperatures before the next high-power pulse, preventing cumulative thermal damage.
3Object-affected harmful factors
If beam alignment is performed at reduced current, then equipment safety is improved, but beam shape and position become unstable due to self-space charge effects
Solution Approach 1:
The system dynamically switches between alignment mode at reduced current and treatment mode at high current. Fast beam position monitors and steering elements continuously adjust the beam during transitions, maintaining stable beam shape and position despite changes in space charge effects between different current levels.
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 the average beam power to safe levels, protects equipment from damage, and maintains treatment efficacy by providing a proton beam with the required energy and current for BNCT.
Implementation Method 1
An ion source is configured to provide a negative ion beam to a tandem accelerator system downstream of the ion source. A modulator system connected to an extraction electrode of the ion source is configured to bias the extraction electrode for a duration sufficient to maintain acceleration voltage stability of the tandem accelerator system.
Implementation Method 2
The high voltage is used to form, e.g., an increasingly positive gradient that is applied to the incoming negative beam to accelerate it, at which point the tandem accelerator converts the negative beam to a positive beam, and then the high voltage is used again to form a reversed decreasingly positive gradient that accelerates (e.g., pushes) the positive beam from the tandem accelerator.
Data Source
AI summary
Embodiments of systems, devices, and methods relate to an ion beam source system. An ion source is configured to provide a negative ion beam to a tandem accelerator system downstream of the ion source, and a modulator system connected to an extraction electrode of the ion source is configured to bias the extraction electrode for a duration sufficient to maintain acceleration voltage stability of the tandem accelerator system.