Low Energy Electron Cooling System Space Charge Limit
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Solution Overview
Problem
Conventional electron cooling techniques face limitations in generating high-intensity electron beams due to self-space charge, particularly for low-energy situations, which restricts the intensity and quality of ion beams used in applications like fusion energy, medical imaging, and contraband detection.
Innovation Solution
The system employs an electron cathode source with electrodes biased to create an electric field that traps neutralizing-background-ions, combined with solenoidal and torroidal magnetic fields to guide and collect the electron beam, allowing for higher electron currents by offsetting the self-space charge, and an electron injector and collector to maintain beam stability and quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional electron cooling techniques are used with direct acceleration from cathode, then electron beam can be generated, but the beam intensity is limited by self-space charge effects
Solution Approach 1:
The patent applies preliminary action by pre-accelerating electrons to high energy before injection into the cooling region, then using decelerating electric fields to reduce them to the required low energy. This preliminary high-energy acceleration allows the electrons to overcome space-charge effects during the critical cooling interaction, while final deceleration achieves the desired low energy for ion cooling.
Solution Approach 2:
The system dynamically adjusts electron beam energy through time-varying electric fields. Electrons are accelerated to high energy, then decelerated to match the ion beam energy for optimal cooling. The dynamic control of electric field potentials allows precise energy matching while maintaining high beam intensity throughout the process.
2Speed
If electron beam energy is reduced for low energy ion cooling, then cooling effectiveness improves, but beam current is severely limited by space charge
Solution Approach 1:
The patent performs preliminary high-energy acceleration of electrons before they enter the cooling region. By accelerating electrons to high energy first, the system can then decelerate them to the required low velocity for ion cooling without being limited by space-charge effects that would constrain low-energy beam generation.
Solution Approach 2:
The system changes the energy parameter of electrons dynamically: first accelerating to high energy to overcome space-charge limitations, then decelerating to match the ion beam energy. This parameter transformation allows the electron beam to maintain high current while achieving the low velocity required for effective ion cooling.
3Manufacturing precision
If high intensity electron beams are used for cooling, then ion beam quality improves, but electron beam stability deteriorates due to space charge effects
Solution Approach 1:
The patent applies preliminary high-energy acceleration to electrons before injection, which allows high current to be achieved without the destabilizing space-charge effects that plague low-energy electron beams. The high initial energy provides stability during transport and injection, while subsequent deceleration achieves the required low energy for cooling.
Solution Approach 2:
The system replaces direct low-energy electron generation with a two-stage process involving high-energy acceleration followed by electromagnetic deceleration. This substitution of the electron generation mechanism allows high current operation with improved stability, as the electrons spend minimal time at high space-charge-prone energies.
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 significantly enhances the intensity and quality of low-energy particle beams, leading to improved yields in photon, neutron, and fusion energy production, while minimizing instabilities and scattering effects.
Implementation Method 1
Electron cooling is a central technology to the invention proposed herein. Electron cooling was originally proposed by Budker in 1966. The basis for his proposal came from work done by Spitzer (1956) who showed that warm ions come to equilibrium with cooler electrons in a plasma.
Implementation Method 2
Typically, solenoidal and torroidal magnetic fields are used to guide the electron beam onto the ion beam, and then into the collection device.
Implementation Method 3
Conventional techniques involve a direct acceleration of the electron beam from its source at a cathode, using electrodes biased positively with respect to the cathode and arranged so as to accelerate the electrons so that they have the same velocity as the ions.
Implementation Method 4
Conventional electron beams have an intensity that is limited by the electron beam's self space charge, and this limit is severe for low energy electron beams.
Data Source
AI summary
A low energy electron cooling system and method for increasing the phase space intensity and overall intensity of low energy ion beams, including a vacuum chamber to allow electron beam and ion beam merging and separation, a cathode to generate the electron beam, a collector to collect the electron beam, magnetic field generation devices to guide the electrons on their desired trajectories, and electrodes to accelerate and decelerate the electron beam. By overlapping the electron and ion beams, thermal energy is transferred from the ion beam to the electron beam, which allows an increase in the phase space density and overall density of the ion beams. Advantageously, the low energy electron cooling system uses electrodes to set up electrostatic potentials that trap non-beam neutralizing-background-ions longitudinally within the electron cooling region and solenoidal fields that trap the non-beam neutralizing-background-ions radially within the electron cooling region. The trapped non-beam neutralizing-background-ions allow electron cooling currents that are vastly larger than the space charge limit of previous electron cooling devices, which leads to vastly improved functioning of the electron cooling device over previous electron cooling devices.