LTS-HTS Persistent Current Switch for Faster Magnet Ramping
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Solution Overview
Problem
Existing superconducting magnet persistent current switches (MPCS) require long ramp-up and ramp-down times due to high heat dissipation during current transitions, which is inefficient and can lead to helium boil-off in sealed magnets.
Innovation Solution
Incorporating a length of superconducting wire made of both low-temperature (LTS) and high-temperature (HTS) materials in series, with HTS segments having high resistance in the normal state, allowing for higher ramp voltages and reduced heat dissipation, and using a heater to control the switch's resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a conventional superconducting switch is used for the magnet persistent current switch, then the magnet can operate in persistent mode, but the ramp-up and ramp-down times are long due to high heat dissipation
Solution Approach 1:
The patent applies composite materials by combining LTS and HTS superconducting materials in a single wire structure. The HTS segment provides high resistance in normal state to reduce heat dissipation during ramping, while the LTS segment ensures reliable superconducting transition. This composite structure resolves the contradiction by enabling faster ramping (reducing time loss) while maintaining low heat dissipation through the HTS material's high normal-state resistance.
Solution Approach 2:
The patent utilizes parameter changes by exploiting the temperature-dependent resistance characteristics of HTS material. Above its critical temperature, HTS exhibits very high electrical resistance which dramatically reduces heat dissipation (I²R losses) during current ramping. This parameter change enables the system to achieve fast ramping speeds without proportionally increasing heat dissipation, directly resolving the time-loss versus energy-loss contradiction.
2Speed
If higher ramp voltage is applied to reduce ramp-up time, then the ramping speed increases, but heat dissipation in the switch increases proportionally
Solution Approach 1:
The composite LTS-HTS wire structure enables higher ramping speeds with controlled heat dissipation. The HTS segment's high normal-state resistance acts as an inherent current limiter that prevents excessive heat generation even when higher voltages are applied to accelerate ramping. This allows the system to achieve faster ramping speeds without the heat dissipation penalty that would normally accompany increased voltage application.
Solution Approach 2:
The HTS segment serves as an intermediary element that mediates between the applied voltage and the LTS segment. During ramping, the HTS segment's high resistance characteristics control the current flow and heat generation, allowing higher voltages to be applied safely without causing excessive heat dissipation. This intermediary function enables the system to achieve fast ramping while maintaining acceptable thermal conditions.
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
Enables faster ramp-up and ramp-down of superconducting magnets with reduced heat load, minimizing helium loss and enabling high-speed operations using conventional power supplies.
Implementation Method 1
a heater to supply heat to at least a portion of the length of superconducting wire
Implementation Method 2
the hts-segment of the length of wire is formed with a high-temperature superconductor material that has a very high electrical resistance in its normal state
Implementation Method 3
the magnet windings are cooled below the critical temperature for superconductivity of the material of the magnet windings, the electrical current persistently flows through the windings
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A persistent current switch (10) for a superconducting magnet comprises a length of superconducting wire having electrical connection ports (16) at its ends, and a heater (13) for supplying heat to the superconducting wire. The length of superconducting wire includes an LTS-segment (11) of low-temperature superconducting material and an HTS-segment (12) of high-temperature superconducting material. Preferably, two LTS-subsegments (11) and one HTS-segment (12) are alternatingly electrically connected in series.