Fiber-Coupled Magneto-Optical Sensing for Pulsed Current Measurement
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Solution Overview
Problem
Conventional metallic-based magnetic field sensors and fiber optical sensors face challenges in accurately measuring large-amplitude, pulsed currents and magnetic fields in high energy environments due to electromagnetic noise, ionizing radiation, and physical damage, while existing magneto-optical sensors suffer from high uncertainty and low signal-to-noise ratios.
Innovation Solution
A fiber-coupled laser beam with a rare-earth element crystal sensor, such as terbium gallium garnet (TGG), is used to measure magnetic fields generated by high electrical currents in pulsed power accelerators, providing a direct linear relationship between optical signal and magnetic field without requiring external calibration or integration, and is resistant to electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional metallic-based magnetic field sensors are used, then magnetic field measurement is achieved, but electromagnetic noise and signal reflections degrade measurement precision
Solution Approach 1:
The patent replaces metallic-based magnetic field sensors with a magneto-optical sensor that uses optical fields instead of electrical fields. The sensor employs a dielectric crystal (such as TGG) through which light propagates, and the magnetic field measurement is achieved by detecting changes in the optical signal's polarization state via the Faraday effect, thereby eliminating electromagnetic noise and signal reflections inherent in metallic sensors
Solution Approach 2:
The patent introduces an optical fiber as an intermediary to transmit the optical signal from the magneto-optical crystal to the detection system. The optical fiber serves as a galvanically isolated transmission medium that carries the modulated light signal without being affected by electromagnetic interference, thus preserving measurement precision in high electromagnetic noise environments
2Reliability
If fiber optical sensors based on the Faraday effect are used, then galvanic isolation is achieved, but the optical fiber is highly susceptible to physical damage and ionizing radiation induced optical noise
Solution Approach 1:
The patent extracts the active sensing function from the optical fiber itself and relocates it to a bulk dielectric crystal (such as TGG). The optical fiber is used only for light transmission to and from the crystal, not as the primary sensing element. This separation allows the sensing function to be performed in a radiation-hardened crystal while the fiber serves merely as a robust transmission medium
Solution Approach 2:
The patent changes the sensing medium from optical fiber material to a bulk dielectric crystal material with superior radiation hardness. The crystal's physical and optical properties are selected to be resistant to ionizing radiation, maintaining stable Faraday rotation characteristics even in high radiation environments, thereby reducing radiation-induced optical noise
3Measurement precision
If conventional sensors requiring calibration and integration are used, then measurement capability is achieved, but device complexity and measurement time increase
Solution Approach 1:
The magneto-optical sensor provides direct linear output where the optical signal intensity is proportional to the magnetic field strength through the Faraday effect. The sensor inherently provides calibrated measurements without requiring external calibration procedures or complex post-processing integration, as the relationship between the measured optical signal and magnetic field is directly proportional and predetermined by the crystal's Verdet constant
Solution Approach 2:
The patent extracts and eliminates the need for calibration and integration processing from the measurement system. By using the Faraday effect in a bulk dielectric crystal, the sensor provides direct linear output that inherently contains the calibration information, removing the complexity of external calibration procedures and signal integration algorithms required by conventional sensors
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
The sensor accurately measures magnetic fields and electrical currents with high sensitivity and robustness in high energy environments, demonstrating consistent performance and minimal interference, with a signal-to-noise ratio improvement potential by using higher power lasers.
Implementation Method 1
A non-metallic based method for sensing magnetic fields and electrical current can be developed by utilizing the Faraday effect
Data Source
AI summary
A magneto-optical sensor can be used to measure electrical current with a very narrow pulse width as sensed by the magnetic field in the transmission line region of a pulsed power accelerator. Pulsed power accelerator experimental results agreed remarkably well with the Faraday effect theory, device physical model, and reference electrical current shunt data.