Superconductor Bulk Magnet Charging via Segmented Field Cooling
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Solution Overview
Problem
Existing methods for charging superconductor bulk magnet systems struggle to easily set a desired target persistent current pattern, especially for a larger number of bulk sub-magnets, leading to difficulties in achieving high magnetic field homogeneity.
Innovation Solution
A method that adapts the cooling system to individually set temperatures of each superconductor bulk sub-magnet, using a temporal sequence of cooling steps and a charger current step pattern to induce the target persistent current pattern, calculated through an advance calculation process considering the geometry and response of the superconductor magnet system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If field cooling process is used to charge superconductor bulk magnet, then magnetic field is trapped in the superconductor bulk magnet, but the magnetic field has relatively low homogeneity
Solution Approach 1:
The superconductor bulk magnet is divided into multiple independently temperature-controllable sub-magnets (first sub-magnet, second sub-magnet, etc.), each capable of being cooled to different temperatures. This segmentation allows independent control of persistent currents in each sub-magnet, enabling precise adjustment of the overall magnetic field homogeneity while maintaining the field trapping capability of the entire system.
2Manufacturing precision
If shim coils are used to correct inhomogeneous magnetic field, then magnetic field homogeneity is improved, but valuable space within the superconductor bore is occupied and significant heat is generated
Solution Approach 1:
The invention extracts the field correction function from external shim coils and integrates it directly into the superconductor bulk magnet structure by using multiple sub-magnets with independently controllable persistent currents. This eliminates the need for separate shim coils, freeing up bore space for sample materials while still achieving magnetic field homogeneity correction.
Solution Approach 2:
The superconductor bulk magnet system performs its own field correction function through the coordinated persistent currents of its multiple sub-magnets, eliminating the need for external correction devices. The system is self-sufficient in both field generation and field homogeneity maintenance, without requiring additional space-consuming components.
3Adaptability or versatility
If individually temperature-controllable sub-magnets are used to establish target persistent current pattern, then arbitrary current patterns can be achieved for field correction, but the cooling system and control process become more complex
Solution Approach 1:
The invention performs preliminary temperature distribution control during the field cooling process, where each sub-magnet is cooled to a specifically predetermined temperature before the main field cooling occurs. This preliminary action establishes the desired persistent current pattern in advance, allowing the system to achieve complex field corrections without requiring complex real-time control mechanisms during operation.
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 method allows for the easy establishment of arbitrary target persistent current patterns, effectively compensating for complex inhomogeneities in the magnetic field, even with a large number of bulk sub-magnets, resulting in highly homogeneous magnetic fields without the need for additional correction coils.
Implementation Method 1
Superconductors have to be exposed to cryogenic temperatures, though, since superconductivity is only assumed below a critical temperature Tc
Implementation Method 2
the superconductor bulk magnet is disposed inside the charger bore of an electrical charger magnet, and then the charger magnet is turned on and generates a magnetic field while the superconductor bulk magnet's temperature T is still above the critical temperature Tc. Then the superconductor bulk magnet is cooled below Tc and becomes superconducting.
Implementation Method 3
the charger magnet is turned on and generates a magnetic field while the superconductor bulk magnet's temperature T is still above the critical temperature Tc
Implementation Method 4
with T kept below Tc, the charger magnet is turned off; by this means, a current is induced in the superconductor bulk magnet, such that the magnetic flux within the superconductor bulk magnet is maintained. In other words, the superconductor bulk magnet traps the magnetic field in its inside.
Data Source
Figure 1a~1b
Figure 2
Figure 3
AI summary
A method for charging a superconductor magnet system (2) comprising N superconductor bulk sub-magnets (6a-6j), wherein the N superconductor bulk sub-magnets (6a-6j) are charged by a field cooling process, wherein at least temporarily the temperatures T=(Tn: n=1...N) of the N superconductor bulk sub-magnets (6a-6j) are chosen different from each other, with n: superconductor bulk sub-magnet index, is characterized in that N ≥ 4, that in an advance calculation, the following steps are applied: a) a temporal sequence of cooling steps csk is chosen, in each of which one more superconductor bulk sub-magnet (6a-6j) is cooled below its critical temperature Tc, with k: sequence index, with k=1...N; b) for each state stk of the superconductor bulk magnet (5) obtained after a respective cooling step csk, a distribution of temperatures I(k) of the superconductor bulk sub-magnets (6a-6j) is determined, with T(k)=(Tn(k): n=1...N), c) for each state stk of the superconductor bulk magnet (5) obtained after a respective cooling step csk, a response of the superconductor bulk sub-magnets (6a-6j) to a change of the charger current Ich is calculated, d) a charger current step pattern c=(ck: k=1...N) is calculated, with current step increment ck: =[Ich(after current step in state stk) - Ich(before current step in state stk)]*(-1), such that a target persistent current pattern itarget=(intarget: n=1...N) in the superconductor bulk sub-magnets (6a-6j) would result, based on the responses calculated in step c), and that the superconductor magnet system (2) is subjected to the field cooling process, applying the temporal sequence of cooling steps csk the charger current step pattern c. Thus setting a desired target persistent current pattern can be accomplished easily, in particular for a larger number of bulk sub-magnets.