Cryogenic Pellet Magnetic Screening for Fusion Disruption Mitigation
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Solution Overview
Problem
Magnetic confinement fusion devices, such as tokamaks, face plasma instabilities leading to rapid plasma current quench and runaway electrons, causing plasma disruption and potential damage to device components, due to the inability of injected pellets to penetrate deeply into the plasma before vaporizing.
Innovation Solution
Cryogenically cooled pellets with metallic exteriors and hollow shells encapsulating payloads like lithium or beryllium are injected into the plasma, utilizing magnetic screening to reduce ablation rates and enhance penetration, allowing deeper penetration and controlled energy radiation to mitigate plasma disruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pellets are injected into plasma to mitigate disruption, then plasma disruption is reduced, but pellets vaporize before reaching central core due to high ablation rates
Solution Approach 1:
The pellet is pre-cooled to cryogenic temperatures (e.g., liquid helium temperature of 4.2K or liquid nitrogen temperature of 77K) before injection. This preliminary cooling action reduces the temperature gradient between the pellet and plasma, significantly lowering the ablation rate and enabling the pellet to penetrate deeper into the plasma core before vaporizing, thus achieving disruption mitigation.
Solution Approach 2:
The temperature parameter of the pellet is changed from ambient temperature to cryogenic temperature. This parameter change fundamentally alters the thermal dynamics between the pellet and plasma, reducing heat transfer from plasma to pellet and thereby reducing ablation. The cooled pellet maintains structural integrity longer during penetration, allowing it to reach the plasma core for effective disruption mitigation.
2Stability of the object's composition
If solid pellets are injected to mitigate disruption, then plasma stability is improved, but intense heat from runaway electrons damages device components
Solution Approach 1:
The cryogenically cooled pellet acts as an intermediary substance injected into the plasma. As it penetrates and vaporizes, it introduces cold material that radiates thermal energy and reduces plasma temperature, thereby stabilizing the plasma and suppressing runaway electron generation. This intermediary action protects device components from damage by preventing the formation of high-energy runaway electrons that would otherwise strike the far wall.
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
The pellets effectively reduce plasma disruption by radiating thermal energy over a wide area, minimizing damage to device components and achieving deeper penetration, thereby stabilizing the plasma confinement.
Implementation Method 1
The cryostat storage device is configured to cool the plurality of pellets to less than or equal to 40 kelvin (K)
Implementation Method 2
utilizing magnetic screening to reduce ablation rates and enhance penetration
Implementation Method 3
The pellets effectively reduce plasma disruption by radiating thermal energy over a wide area
Data Source
AI summary
Exemplary pellets can be used for magnetic fusion devices for mitigating plasma disruption. In some embodiments, the pellets may be cryogenically cooled that may cause a rise in the electrical conductivity of the pellets. A high conductivity of the pellet can screen out the plasma's magnetic field from the interior of the pellet. The screening out of the plasma's magnetic field can slow the ablation rate of the pellet which may allow for deeper pellet penetration and a better suited spatial profile of deposited material for proper mitigation of the plasma disruption. In some other embodiments, the pellets may not be cryogenically cooled.