SQUID Probe Segmentation for Magnetic Property Detection
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Solution Overview
Problem
Current methods for measuring extremely small magnetic fields using SQUID technology are limited by the need for cryogenic conditions, which restricts flexibility and accuracy due to the bulky cryostat required, and introduces noise issues when the material under investigation is not within the cryostat.
Innovation Solution
A probe system that applies an alternating magnetic field to a material, senses the change in magnetic parameters, and conveys the signal to a remote SQUID, using noise-reduction techniques to distinguish the desired signal from noise, allowing for measurements at room temperature and increased flexibility in positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the material under investigation is located outside the cryostat, then flexibility in positioning and ease of operation are improved, but the magnetic signal quality deteriorates because the signal must permeate the cryostat wall
Solution Approach 1:
The system is divided into two separate modules: a portable sensor coil that can be positioned close to the material outside the cryostat, and a stationary SQUID detector inside the cryostat. This segmentation allows the sensor to be flexible while the SQUID remains protected, resolving the contradiction between positioning flexibility and signal quality.
Solution Approach 2:
The sensor coil acts as an intermediary between the material and the SQUID detector. It captures the magnetic signal outside the cryostat and transmits it via cable to the SQUID inside, eliminating the need for the signal to permeate the cryostat wall while maintaining measurement precision.
2Object-affected harmful factors
If the sensor coil and transfer coil are positioned within the cryostat, then noise levels are reduced due to low resistance, but device complexity and bulkiness increase
Solution Approach 1:
The sensor coil is extracted from the cryostat environment and positioned outside with the material under investigation. Only the SQUID detector and transfer coil remain inside the cryostat, simplifying the overall device structure while maintaining low noise performance through the cold transfer coil.
Solution Approach 2:
The sensor coil performs multiple functions: it acts as both the sensing element and the signal source for the transfer coil. By making the sensor coil universal, the system reduces the number of separate components needed within the cryostat, thereby reducing device complexity.
3Reliability
If the sensor coil is separated from the magnetic signal source by a distance of a centimetre or more, then the cryostat vacuum and radiation shields are accommodated, but measurement precision deteriorates
Solution Approach 1:
The sensor coil serves as an intermediary that bridges the gap between the material and the SQUID detector. It can be positioned immediately adjacent to the material outside the cryostat, capturing the magnetic signal at maximum strength, while the cryostat remains intact with its vacuum and radiation shields.
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 high-precision, sensitive measurement of magnetic properties without the need for cryogenic conditions, providing greater freedom in sensing and allowing for applications like depth profiling and distinguishing between magnetic and electric responses, with improved signal-to-noise ratio and flexibility in environment and positioning.
Implementation Method 1
means for sensing a change in a magnetic parameter of the material resulting from the applied alternating magnetic field and for generating a sensor output signal in response thereto
Implementation Method 2
the current induced in the sensor coil is supplied to the transfer coil, and the magnetic field associated with the current in the transfer coil is sensed by the SQUID
Data Source
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AI summary
Apparatus for determining magnetic properties of materials comprises a portable probe 1, an equipment trolley 2 holding cryogenics and electronics and connecting cables 3. The probe 1 comprises a drive coil 4 and a correction coil 5, the drive coil 4 being disposed symmetrically with respect to an inner second-order gradiometer sensor coil 8. Electrical connectors in the form of 2-metre long Belden 1192A microphone cables 3 are used to connect the apparatus on the equipment trolley 2 to the drive coil 4, the correction coil 5 and the sensor coil 8. The drive coil 4 is driven so as to generate a sinusoidally varying magnetic field. The electronics comprise a flux-locked loop 9, a SQUID controller 10, a data acquisition module 11, which captures and processes the signals and a computer 12. A liquid-nitrogen dewar 13 is supported on the equipment trolley 2 and houses a sensitive SQUID detector 14 and a transfer coil 15 made from copper. Possible applications of the apparatus include an intra-operative tool for sentinel lymph node detection in the treatment of breast cancer, and a non-destructive evaluation tool for detecting voids and defects in aluminium and applications in the aeronautics industry.