High Current Ion Accelerator Vacuum Segmentation
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Solution Overview
Problem
High-current DC linear particle accelerators face limitations in beam current capability due to the release of neutral gas from ion sources, which increases vacuum pressure and leads to undesirable effects such as ionization, scattering, and reduced voltage holding capability, hindering the development of high-intensity ion beams.
Innovation Solution
A high-current accelerator system with a vacuum enclosure in the high-voltage terminal that includes a mass-analyzer and a separate pumping tube to efficiently remove neutral gas before it enters the acceleration tube, maintaining low vacuum pressure and preventing gas entry, while using a Dynamitron-type power supply to generate MeV ion beams exceeding 5 mA.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the primary beam current from the ion source is increased, then the beam intensity is improved, but the vacuum pressure inside the acceleration tube increases due to release of neutral gas
Solution Approach 1:
The system is divided into two separate vacuum chambers: a first vacuum chamber housing the ion source and a second vacuum chamber housing the acceleration tube. This segmentation allows independent vacuum management, enabling high beam current in the ion source while maintaining low vacuum pressure in the acceleration tube through separate pumping systems.
Solution Approach 2:
A vacuum restriction element acts as an intermediary between the first and second vacuum chambers. This element creates a conductance bottleneck that prevents neutral gas from the high-current ion source region from flowing into the acceleration tube, thereby decoupling the vacuum pressure in both chambers.
2Quantity of substance
If neutral gas is present in the acceleration tube, then the beam current can be higher, but the voltage holding capability is reduced due to ionization and scattering effects
Solution Approach 1:
The acceleration tube is isolated in a separate second vacuum chamber with independent vacuum pumping. This allows the acceleration tube to maintain low vacuum pressure necessary for high voltage holding capability, while the ion source in the first chamber can operate at higher pressure to generate high beam current.
Solution Approach 2:
The vacuum restriction element serves as a protective barrier that selectively limits the flow of neutral gas into the acceleration tube, preserving the vacuum quality and voltage holding capability in the acceleration region while allowing high current operation in the ion source region.
3Stress or pressure
If a vacuum pump is placed inside the high-voltage terminal, then the vacuum pressure can be reduced, but the system downtime increases due to periodic regeneration requirements
Solution Approach 1:
The vacuum pumping system is segmented into two independent parts: a first vacuum pump for the ion source chamber and a second vacuum pump for the acceleration tube chamber. This allows the second pump serving the acceleration tube to operate continuously without periodic shutdowns for regeneration, as it handles much less gas load.
Solution Approach 2:
The vacuum restriction element acts as a protective barrier that shields the second vacuum pump (serving the acceleration tube) from the high gas load in the ion source chamber. This allows the second pump to maintain vacuum with minimal gas throughput, avoiding the need for periodic regeneration and reducing system downtime.
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 configuration enables the acceleration of high-current beams with reduced system downtime by minimizing vacuum pressure and preventing gas entry into the acceleration tube, thereby enhancing beam stability and voltage holding capability, and allowing for applications like cancer therapy and semiconductor processing.
Implementation Method 1
the high-voltage terminal further comprises a vacuum enclosure in which the high-current ion beam from the ion source is transported towards the accelerating tube and which houses a mass-analyzer to remove unwanted contaminants from the primary ion beam
Implementation Method 2
Connected in between the vacuum enclosure in the high voltage terminal and the vacuum pump at ground potential is a separate pumping tube that can withstand the full accelerator high voltage. The neutral gas from the ion source can flow via the vacuum enclosure through the pumping tube towards ground potential where it is further removed from the system by a vacuum pump.
Implementation Method 3
A DC single-ended linear accelerator that may be powered from a Dynamitron-type power supply capable of producing MeV ion beams
Data Source
AI summary
A single-ended DC linear accelerator for the generation of high-current, high-energy ion beams of H, D or He includes an ion source located in a high-voltage terminal for the creation of the ion beam, an analyzing magnet to purify the ion beam, an accelerating tube and DC high-voltage power supply for accelerating the ions of interest to high energies and a separate pumping tube that transports the vast majority of the neutral gas from the ion source at high-voltage towards a vacuum pump at ground potential, thereby preventing the adverse influence of increased vacuum pressure inside the accelerating tube to facilitate stable acceleration of high-current beams to high energies in single-ended DC linear accelerators. The resulting high-current accelerator for H, D or He has diverse applications, including ion beam cancer therapy, cyclotron injection, silicon cleaving, ion implantation in semiconductor devices and NRA.