Superconducting Magnet System with Inductive Compensation Coil
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Solution Overview
Problem
Current magnet systems for NMR applications face challenges in generating highly stable magnetic fields due to noise and instabilities introduced by power supplies, especially when using HTS conductors, which are necessary for higher proton frequencies, as there are no reliable superconducting joints with low ohmic losses for LTS conductors, leading to field drifts that cannot be adequately compensated by existing drift compensation measures.
Innovation Solution
An external power supply is used to drive the first magnet coil, and a second magnet coil is inductively coupled to compensate magnetic field fluctuations, with a superconducting compensation coil that is short-circuited during operation, allowing for the generation of a highly stable magnetic field by inducing compensation currents in the second coil to counteract fluctuations from the power supply noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an external power supply is used to drive the first magnet coil, then the magnetic field strength can be increased to reach higher proton frequencies (e.g., around 1200 MHz), but the power supply introduces noise and instabilities that cause magnetic field fluctuations
Solution Approach 1:
A second compensation coil is introduced as an intermediary element between the power supply noise and the sample location. This compensation coil is inductively coupled to the first magnet coil and generates a counteracting magnetic field that cancels out the fluctuations caused by the power supply, thereby mediating the conflict between achieving high field strength and maintaining field stability
Solution Approach 2:
The compensation coil operates with feedback from the first magnet coil through inductive coupling. When the power supply causes fluctuations in the first coil's magnetic field, these fluctuations are inductively coupled to the second coil, which then generates a compensating field that feeds back to cancel the original fluctuations, creating a stable magnetic field at the sample location
2Power
If HTS conductors are used in the innermost sections of the magnet coil, then higher magnetic fields can be generated, but the lack of reliable superconducting joints with low ohmic losses leads to field drift
Solution Approach 1:
The compensation coil acts as an intermediary that compensates for the field drift caused by imperfect HTS joints. By being inductively coupled to the first magnet coil, it can counteract the drift effects without requiring perfect joints in the HTS conductor connections
Solution Approach 2:
The invention converts the harmful effect of HTS joint imperfections and ohmic losses into a manageable parameter. The compensation coil is specifically designed to counteract the drift caused by these joint imperfections, thereby converting what would be a system failure into a controllable and compensatable effect
3Reliability
If a superconducting compensation coil is used to compensate for magnetic field fluctuations, then field stability is improved, but the system complexity increases due to the need for inductive coupling and additional coil structures
Solution Approach 1:
The second compensation coil serves multiple functions: it compensates for power supply noise, compensates for HTS joint drift, and can be adjusted to optimize performance for different operating conditions. This multi-functionality justifies the additional system complexity by providing comprehensive stabilization
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 achieves a significantly more stable magnetic field at the sample location, with fluctuations reduced by several orders of magnitude compared to commercial power supply noise, enabling the use of drifting superconductors and joints while maintaining low ohmic losses, thus supporting high-resolution NMR spectroscopy.
Implementation Method 1
the second magnet coil which during operation of the magnet system is superconductively short-circuited by a superconducting switch and which inductively couples to the first magnet coil
Implementation Method 2
a superconducting compensation coil which compensation coil, during operation, is superconductively short-circuited by the switch
Data Source
AI summary
A magnet system generates a highly stable magnetic field at a sample location. The magnet system has a magnet cryostat housing a first superconducting magnet coil and a second magnet coil co-axial to the first magnet coil. The second magnet coil is short-circuited in a superconducting persistent mode during operation of the magnet system. An external power supply during operation supplies current to the first magnet coil via a current lead thereby generating a first magnetic field at the sample location that fluctuates according to the current noise of the power supply, wherein the second magnet coil is positioned and dimensioned in a way that it inductively couples to the first magnet coil such that it generates at the sample location a second magnetic field that compensates the fluctuations of the first magnetic field.