Superconducting Magnet Charging with Shielding Current Suppression
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Solution Overview
Problem
Superconducting magnet arrangements with combined high-temperature superconductor (HTS) and low-temperature superconductor (LTS) windings face challenges in eliminating shielding currents, which lead to field instability and inhomogeneities, as existing methods are not applicable when the magnet includes LTS due to the risk of quenching.
Innovation Solution
A method involving a second magnet winding made of a superconductor with a transition temperature above the operating temperature, allowing for excitation of an operating current after cooling to generate a magnetic field that suppresses shielding currents in the LTS material, thereby preventing them during the charging and cooling process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If temperature is increased to eliminate shielding currents in HTS windings, then shielding currents are reduced, but LTS windings may be heated above transition temperature causing quench
Solution Approach 1:
The magnet arrangement is divided into separate HTS and LTS winding sections with independent current control. This allows selective heating and current adjustment of the HTS section without affecting the LTS section, enabling shielding current elimination in HTS while maintaining LTS below its transition temperature.
Solution Approach 2:
The invention changes the temperature parameter dynamically during the charging process. The HTS winding is heated to a temperature between its transition temperature and the LTS transition temperature, allowing shielding current elimination in HTS while keeping LTS cold enough to remain superconducting. This parameter change enables selective control of different superconductor sections.
2Strength
If combined HTS and LTS windings are used to achieve high field strength, then magnetic field performance is improved, but shielding current elimination becomes more complex
Solution Approach 1:
The invention performs preliminary heating of the HTS winding to a specific temperature range before charging the LTS winding. This preliminary action eliminates shielding currents in the HTS section in advance, so that when the LTS is charged, it does not induce additional shielding currents in the already-prepared HTS section, simplifying the overall charging process.
Solution Approach 2:
The invention uses parameter changes by controlling the temperature of different winding sections independently. The HTS section is maintained at an elevated temperature (above its transition temperature but below LTS transition temperature) during LTS charging, which prevents shielding current formation. This parameter control simplifies the multi-winding charging process.
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 prevents shielding currents during the cooling and charging of magnet arrangements with HTS and LTS windings, reducing equipment and technical risks, and allows for more stable and homogeneous magnetic fields, essential for high-field applications like NMR methods.
Implementation Method 1
partially persistent shielding currents can flow in the ribbon, which reduce the field strength of the magnet array or lead to field inhomogeneities and field instability
Implementation Method 2
superconducting magnet arrays are generally used to generate these fields
Implementation Method 3
superconducting magnet arrangement arranged in a cryostat device for cooling to a cryogenic operating temperature
Data Source
Figure 1a
Figure 1b
Figure 2
AI summary
A method for charging a magnet arrangement comprising a superconducting tape conductor with a first transition temperature in a cryostat device, comprises: (a) temperature control to a first pre-temperature between the first transition temperature and the operating temperature, (b) excitation of a first pre-current, (c) cooling to operating temperature, (d) excitation of a first operating current, and is characterized in that the magnet arrangement comprises a second magnet winding made of a second superconducting material with a second transition temperature above the operating temperature and at least 15 K below the first transition temperature, wherein a second operating current is excited in the second magnet winding at the latest after the magnet arrangement has cooled to the operating temperature, and the second magnet winding with the second operating current generates a second operating magnetic field in the volume of the first magnet winding.This achieves, when charging magnetic arrangements with combined magnetic windings made of superconducting materials with different transition temperatures, the elimination of shielding currents in the superconducting tape conductor through temperature control and the freezing of the state with reduced shielding currents upon cooling to operating temperature, without eliminating the currents in the magnetic windings with the material of lower transition temperature.