Summary of NEW GRAPHENE HALL EFFECT SENSOR TO IMPROVE ACCURACY AND PRECISION IN MAGNETIC MEASUREMENT APPLICATIONS
Paragraf and CERN demonstrated graphene-based Hall effect sensors that eliminate planar Hall effects, enabling true single-axis magnetic field sensing with high precision. Atomically thin graphene provides negligible planar signals, wide temperature operation (from +80°C down to 1.5 K), and suitability for cryogenic liquid helium environments. This enables improved local field mapping, rotating-shaft stacked sensor techniques, and more accurate harmonic measurements along magnet axes. CERN will run further tests toward a novel magnetic field mapping system for superconducting magnets.
Parts used in the Paragraf Hall effect sensor project:
- Atomically thin graphene active sensing element
- Hall effect sensor packaging (sensor stack for mounting on rotating shaft)
- Cryogenic-compatible sensor assembly for operation down to 1.5 Kelvin
- Interconnects and readout electronics for magnetic field measurement
- Calibration and testing setup at CERN Magnetic Measurement section
The Cambridge-based startup, Paragraf has collaborated with the Magnetic Measurement section at CERN to demonstrate the potential of graphene-based Hall effect sensors to improve accuracy in magnetic measurement applications.
Overcoming the shortfalls of existing Hall effect sensors that exhibit planar Hall effects that produce false signals, Hall effect Sensor from Paragraf truly senses magnetic fields along one direction giving a negligible planar Hall effect. This is because the active sensing component of the Hall effect Sensor from Paragraf is made of atomically thin graphene which is two-dimensional. This enables the true perpendicular magnetic field value to be obtained, allowing for higher precision mapping of the local magnetic field.
Opening the door to a new mapping technique by mounting a stack of sensors on a rotating shaft, Hall effect sensors without planar effect indeed will be the preferable option. Measurements of the harmonic content in accelerator magnets almost point-like along the magnet axis would be the added advantage. Wide temperature range from +80°C down to cryogenic temperatures of 1.5 Kelvin is one of the key properties of the Paragraf Hall effect sensor.
With this major step, CERN would be able to measure the fields inside the superconducting magnets with high accuracy. This could be done using sensors operating in liquid helium temperature ranges (below -269 °C, 4 Kelvin, -452 °F) where the calibration of sensors is less than trivial. CERN’s Magnetic Measurement section is planning to perform more in-depth tests on the Hall effect sensors to eventually use them in building a novel mapping system for magnetic fields.
- What advantage does graphene provide in Paragraf Hall effect sensors?
Graphene is atomically thin and two-dimensional, which yields negligible planar Hall effect and enables true single-direction magnetic field sensing. - Can these sensors operate at cryogenic temperatures?
Yes, the sensors operate across a wide temperature range including cryogenic temperatures down to 1.5 Kelvin. - Does the Paragraf sensor reduce false signals from planar Hall effects?
Yes, it truly senses magnetic fields along one direction giving a negligible planar Hall effect, reducing false signals. - How could these sensors improve magnetic field mapping?
They allow higher precision local field mapping and enable a new technique using a stack of sensors mounted on a rotating shaft. - Will CERN use these sensors inside superconducting magnets?
CERN plans further tests with the goal of using them to measure fields inside superconducting magnets with high accuracy. - Are the sensors suitable for measurements in liquid helium environments?
Yes, they are suitable for operation in liquid helium temperature ranges such as around 4 Kelvin. - Do the sensors help with harmonic content measurements in accelerator magnets?
Yes, measurements of harmonic content almost point-like along the magnet axis would be an added advantage.
