Three-axis optically pumped magnetometer gradiometric measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing magnetic gradiometry methods, such as those using SQUID sensors, are limited by fixed measurement bases and directions, require cryogenic cooling, and cannot measure all components of the magnetic field tensor, while optically pumped magnetometers can only measure a subset of the magnetic field gradients due to their architecture.
Innovation Solution
A three-axis vector optically pumped magnetometer with a photodetector array and processing unit capable of measuring all components of the magnetic field tensor, allowing for the calculation of six independent components of the magnetic field gradient tensor by differential measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If SQUID sensors are used for gradiometric measurement, then measurement sensitivity is improved, but the device requires cryogenic cooling and magnetic shielding enclosures which increase device complexity and cost
Solution Approach 1:
The patent replaces SQUID sensors with optically pumped magnetometers, substituting a cryogenic superconducting system with an optical-atomic system. The optically pumped magnetometer uses laser pumping of atomic vapor (e.g., alkali metals) to achieve magnetic field sensing without requiring cryogenic cooling or complex magnetic shielding, thereby reducing device complexity while maintaining measurement capability
Solution Approach 2:
The patent changes the operating temperature parameter from cryogenic (SQUID) to room temperature (optically pumped magnetometer). This parameter change eliminates the need for cryogenic cooling systems and reduces the complexity of the overall measurement system while preserving gradiometric measurement functionality
2Measurement precision
If SQUID sensors are used for gradiometric measurement, then magnetic field gradient measurement is enabled, but the measurement base and direction are fixed which reduces adaptability
Solution Approach 1:
The patent implements a reconfigurable measurement system using multiple optically pumped magnetometers that can be dynamically arranged and oriented. The system allows changing the measurement base distance and orientation angles between sensors, enabling adaptation to different measurement configurations and targets, unlike fixed SQUID gradiometer geometries
Solution Approach 2:
The patent creates a universal gradiometric measurement system using optically pumped magnetometers that can measure magnetic field gradients in multiple directions and configurations. The system can be reconfigured for different base lengths, orientations, and measurement geometries, providing multi-functional capability that exceeds the specialized fixed-geometry SQUID gradiometers
3Device complexity
If optically pumped magnetometers are used for gradiometric measurement, then device complexity is reduced, but only a subset of magnetic field gradient components can be measured which limits measurement completeness
Solution Approach 1:
The patent divides the measurement system into multiple optically pumped magnetometer units arranged in specific geometries (e.g., vertical pairs, horizontal pairs, or tetrahedral configurations). Each sensor measures local magnetic field vectors, and by combining measurements from multiple segmented positions, the system reconstructs complete gradient tensor information including all three spatial derivatives
Solution Approach 2:
The patent transitions from single-component SQUID measurements to three-component vector measurements using optically pumped magnetometers. By adding spatial dimensionality through multiple sensor arrangements and utilizing the full vector nature of atomic magnetometer measurements, the system captures complete gradient tensor information (∂Bx/∂x, ∂Bx/∂y, ∂Bx/∂z, ∂By/∂x, ∂By/∂y, ∂By/∂z, etc.) that exceeds the limited capability of conventional gradiometers
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 the measurement of all components of the magnetic field tensor, providing comprehensive spatial distribution and gradient analysis without the need for cryogenic cooling, and allows for reconfigurable bases and directions, enhancing sensitivity and applicability in various fields.
Implementation Method 1
The use of polarised light sources, typically lasers, allows the preparation of atomic states characterised by some orientation or alignment of their spins. This process is called 'optical pumping' in this field.
Implementation Method 2
These atomic states change under the effect of the magnetic field, especially under the Zeeman effect, which corresponds to shifts in the energy levels as a function of the magnetic field to which the atoms are subjected.
Implementation Method 3
The optical properties of the atomic medium then undergo modifications that depend on the state of the atoms. An optical measurement, for example an optical absorption measurement, can be used to deduce the Zeeman shift undergone and to derive a measurement of the magnetic field in which the cell is immersed.
Data Source
AI summary
A three-axis vector optically pumped magnetometer includes a cell filled with an atomic gas subjected to an ambient magnetic field the projection of which on three rectangular coordinate axes defines three components thereof, and a photodetector arranged to receive a probe beam that passed through the cell. The photodetector includes a plurality of measurement units arranged in a plane transverse to a direction of propagation of the probe beam, the measurement units each providing a photodetection signal. The magnetometer further comprises a processing unit configured to determine, for each measurement unit and from the photodetection signal, a measurement associated with the measurement unit of each of the three components of the ambient magnetic field; calculate at least one difference between the measurements, associated with different measurement units, of a component of the magnetic field; and deliver a gradiometric measurement signal including the at least one difference calculated.