Superconductor Bulk Magnet Field Homogenization Without Temperature Sensors
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Solution Overview
Problem
Existing superconductor magnet systems face challenges in achieving high magnetic field homogeneity due to limitations in current distribution, which is often restricted by hardware design and requires complex temperature control systems with additional sensors, increasing costs and complexity.
Innovation Solution
A method that adjusts the heating and cooling powers of axially stacked bulk sub-magnets without temperature measurements, bringing some sub-magnets to magnetic saturation while keeping others away, to redistribute currents and homogenize the magnetic field profile, using a feedback loop from repeated magnetic field profile measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If temperature sensors are installed at each bulk sub-magnet for precise temperature control, then magnetic field homogeneity can be improved, but device complexity and cost increase
Solution Approach 1:
The patent removes temperature sensors from the system entirely. Instead of measuring temperature at each bulk sub-magnet, the method uses magnetic field measurements to infer the necessary temperature adjustments. This extraction of unnecessary components directly reduces device complexity while maintaining magnetic field homogeneity through feedback control based on magnetic field profiles.
Solution Approach 2:
The patent introduces magnetic field measurements as an intermediary parameter to control temperature. Rather than directly measuring and controlling temperature, the system measures magnetic field strength and uses this information to adjust heating/cooling powers. This intermediary approach allows indirect temperature control without requiring temperature sensors.
2Ease of operation
If multiple temperature sensors are installed for independent temperature control of each bulk sub-magnet, then current distribution control can be improved, but cost increases
Solution Approach 1:
The patent extracts and removes all temperature sensors from the system. Current distribution control is achieved not through direct temperature measurement but through magnetic field measurement and subsequent heating power adjustment. This eliminates the need for multiple temperature sensors while maintaining precise control over current distribution in the bulk sub-magnets.
Solution Approach 2:
The magnetic field measurement system serves multiple functions: it characterizes the initial magnetic field profile, monitors temperature-induced changes, and provides feedback for heating power control. This single measurement system replaces what would otherwise require multiple temperature sensors, achieving universal functionality with fewer components.
3Manufacturing precision
If heating powers are adjusted based on temperature measurements, then magnetic field homogeneity can be maintained, but system complexity increases
Solution Approach 1:
The patent implements feedback control using magnetic field measurements instead of temperature measurements. The magnetic field profile is measured, compared to a target profile, and the heating powers are adjusted accordingly. This feedback loop maintains magnetic field homogeneity while simplifying the control system by eliminating temperature sensors and their associated complexity.
Solution Approach 2:
The patent changes the control parameter from temperature to magnetic field strength. Instead of measuring and controlling temperature, the system measures magnetic field strength and uses this parameter to control heating powers. This parameter change simplifies the system by removing temperature measurement requirements while maintaining precise control over magnetic field homogeneity.
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 simplifies the system design, reduces costs by eliminating temperature sensors, and achieves a highly homogeneous magnetic field with precise control over current distribution, enhancing the homogeneity of the magnetic field generated by the superconductor magnet system.
Implementation Method 1
the superconductor bulk magnet is cooled below T crit and becomes superconducting. Subsequently, with T bulk kept below T crit, 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.
Implementation Method 2
Superconductors are materials that may carry an electrical current at practically no ohmic losses. Superconductors have to be exposed to cryogenic temperatures, though, since superconductivity is only assumed below a critical temperature T crit
Implementation Method 3
the cryogenic cooling system is adapted for independently controlling the temperature of each bulk sub-magnet
Implementation Method 4
temperatures of at least a part of the bulk sub-magnets are chosen at least temporarily different from each other, such that for a first part of the bulk sub-magnets, the bulk sub-magnets of this first part are at least almost magnetically saturated
Data Source
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AI summary
A method for homogenizing a magnetic field profile of a superconductor magnet system (2), wherein the superconductor magnet system (2) comprises - a cryostat (4) having a room temperature bore (7a), - a superconductor bulk magnet (5), contained in the cryostat (4) and arranged coaxially with the room temperature bore (7a), and - a cryogenic cooling system (13) adapted for cooling the superconductor bulk magnet (5), wherein the superconductor bulk magnet (5) comprises at least N axially stacked bulk sub-magnets (6a-6c), with N≥3, wherein in an initial state, the bulk sub-magnets (6a-6c) carry respective initial currents with relative proportions according to an initial distribution scheme, and the method comprises a posterior correction step (50) which changes the initial currents into final currents with relative proportions according to a final distribution scheme which is different from the initial distribution scheme, wherein a magnetic field profile of the superconductor bulk magnet (5) based on the final currents is more homogenous than a magnetic field profile based on the initial currents, wherein the cryogenic cooling system (13) is adapted for independently controlling the temperature of each bulk sub-magnet (6a-6c), and wherein for changing the initial currents into the final currents, temperatures of at least a part of the bulk sub-magnets (6a-6c) are chosen at least temporarily different from each other, such that - for a first part of the bulk sub-magnets (6a-6c), the bulk sub-magnets (6a-6c) of this first part are at least almost magnetically saturated, and - for a second part of the bulk sub-magnets (6a-6c), the bulk sub-magnets (6a-6c) of this second part are significantly away from magnetic saturation, is characterized in that for changing the initial currents into the final currents, the temperatures of the bulk sub-magnets (6a-6c) are chosen by controlling a heating power and/or a cooling power at the bulk sub-magnets without measuring the temperatures of the bulk sub-magnets, wherein for at least the part of the bulk sub-magnets (6a-6c), the heating powers are set at least temporarily different from each other and/or the cooling powers are set at least temporarily different from each other. The invention provides a method with which a magnetic field profile of a superconductor magnet system may be homogenized in a simple and inexpensive way.