A proposed magnetometer for use in a cryogenic environment would be sensitive enough to measure a magnetic-flux density as small as a picogauss (10-16 Tesla). In contrast, a typical conventional flux-gate magnetometer cannot measure a magnetic-flux density smaller that about 1 microgauss (10-10 Tesla).
One version of this device, for operation near the low end of the cryogenic temperature range, would include a piece of a paramagnetic material on a platform, the temperature of which would be controlled with a periodic variation. The variation in temperature would be measured by use of a conventional germanium resistance thermometer. A superconducting coil would be wound around the paramagnetic material and coupled to a superconducting quantum interference device (SQUID) magnetometer.
The SQUID magnetometer would be used to measure the change in current in the coil as a result of the change in temperature measured by the germanium resistance thermometer. The ratio between the current change and the temperature change would be computed, then used to infer the ambient magnetic field. This inference would be drawn from a lookup table established by prior calibration measurements performed at the same mean operating temperature.
In an alternative version of this magnetometer, for operation at a temperature near the high end of the cryogenic range, the coil and the SQUID magnetometer would be made from a high-temperature superconductor and the coil would be in the form of a thin film deposited on the same substrate as that of the SQUID. The paramagnetic material would be inserted in a hole at the center of the coil. The temperature of the whole substrate would then be modulated during measurements of the type described above.
Because of the oscillatory temperature excitation, this magnetometer would exhibit very little drift. The highest sensitivity and the lowest noise would be achieved by careful selection of the paramagnetic material and operating near the Curie temperature of that material.
Although the SQUID magnetometer and the superconducting coil must be kept cold, it would be possible to measure the magnetic field of a warm environment. For this purpose, the magnetometer could be kept at the required low temperature in a nonmagnetic Dewar flask, which could be brought to the warm measurement location.
While conventional SQUID magnetometers are routinely used to measure the change in magnetic flux density with similar sensitivity, the proposed implementation allows the full sensitivity of SQUID to be used to measure a small static magnetic flux density. Another implementation method involves flipping the pickup coil of a SQUID to measure the ambient static field. Although such a method had been used before, it involves cumbersome mechanical actuators to flip the coil at cryogenic temperatures and the wire of the coil can work harden and break after repeated flipping. Because of the absence of moving parts in the proposed magnetometer, reliability is improved.
This work was done by Peter Day, Talso Chui, and David Goodstein of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Physical Sciences category. NPO-40748
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Cryogenic High-Sensitivity Magnetometer
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Overview
The document outlines a novel cryogenic high-resolution magnetometer developed by the Jet Propulsion Laboratory (JPL) at the California Institute of Technology. This technology aims to measure absolute magnetic fields with high sensitivity, particularly in cryogenic environments, which is essential for various scientific investigations in microgravity and future interplanetary missions.
The magnetometer addresses the limitations of existing technologies, such as fluxgate magnetometers, which are less sensitive and accurate. The new device can measure magnetic fields down to approximately 1 Pico-Gauss, significantly improving upon the capabilities of traditional methods. The innovation is particularly relevant for experiments conducted in low magnetic field conditions, where precise measurements are crucial.
The document details the motivation behind the development of this technology, highlighting the need for accurate magnetic field monitoring in space exploration and scientific research. The contributors to the project include Peter K. Day and Talso C. Chui, who played significant roles in the design and implementation of the device. David Goodstein is credited with the original idea for the magnetometer.
The technology has been tested in a proof-of-principle device, demonstrating its potential for high-resolution measurements without drift and moving parts, which enhances its reliability for long-term use in space. The document also discusses the commercialization potential of the magnetometer, identifying applications in geologic exploration, mineral and oil search, and biomedical research and development.
Furthermore, the document emphasizes the ongoing need for further development, including the creation of a low-field apparatus to test the device's sensitivity at higher levels. It notes that while the technology has not yet been used outside of JPL, there are plans for future disclosures to the public.
In summary, this document presents a significant advancement in magnetometer technology, with implications for both scientific research and commercial applications. The development of this cryogenic high-sensitivity magnetometer represents a crucial step forward in the ability to measure magnetic fields in challenging environments, paving the way for enhanced exploration and understanding of both terrestrial and extraterrestrial phenomena.
