Paragraf and CERN Partner for New Hall Effect SensorJune 21, 2020 by Nicholas St. John
Paragraf looks to demonstrate how new opportunities for magnetic measurements are opened up through the unique properties of its graphene sensor.
Paragraf and CERN announced the groups have been working on expanding the opportunities of magnetic measurement with the help of its graphene sensor.
“This collaboration with CERN demonstrates the potential of graphene-based Hall effect sensors to improve accuracy in magnetic measurement applications,” said CEO of Paragraf, Simon Thomas. “Our Hall effect sensors address key challenges CERN is facing in mapping magnetic fields, namely: highly accurate measurements of local field distributions in accelerator magnets while eliminating artifacts and reducing uncertainties stemming from the sensors.”
Wire bonding of a Hall-Effect sensor to a chip carrier using a wedge bonder. Image courtesy of Paragraf.
At CERN, the European Organization for Nuclear Research, the precise measurement of magnetic fields is critical, as particle accelerators rely on normal and superconducting magnets to guide the particle beams to their exact collision points.
CERN utilizes Hall Effect sensors for these measurements. Hall Effect sensors are magnetic field sensors that have an output voltage response proportional to the magnetic flux around the sensor, as long as the hall effect sensor is oriented in the correct position, where the magnetic flux lines are perpendicular to the flow of current within the sensor.
Current Hall Effect sensors have an issue based on their physical configuration, specifically its three-dimensional nature. Hall Effect voltage is inversely proportional to the thickness of the sensor material. The sensor is supposed to measure the field perpendicular to its current flow, with a three-dimensional nature, however, it can pick up magnetic fields in different directions than the one looking to be measured, adding a high level of uncertainty to the magnetic field final measurement. This phenomenon is known as the planar Hall Effect, and this value is not able to be changed via signal processing circuitry and is a ceiling preventing higher precision and accuracy of the sensor material.
The graphene Hall sensor (GHS) is loaded into a rotating stage and into the bore of the Magnetic Measurements Section’s reference dipole magnet. Image courtesy of Paragraf.
Paragraf was able to fix this problem, as its Hall Effect sensor has a negligible planar Hall Effect. They were able to attain this by utilizing an atomically thin sheet of graphene as its hall sensor.
According to the head of the magnetic measurement section at CERN, Stephan Russenschuck, these sensors provide a huge opportunity for CERN. This is not only due to their much-improved accuracy but now these flat sensors can be stacked against one another, still keeping their precision due to the fact that the two-dimensional anatomy will prevent current to be generated from the surrounding graphene sensors. This allows a near point-to-point measurement of the magnetic field being measured within the particle accelerators.
One of the key properties of Paragraf’s Hall effect sensor is its wide temperature range from +80°C down to cryogenic temperatures of 1.5 Kelvin. Image courtesy of Paragraf.
On top of the sensor’s high accuracy via a negligible planar Hall Effect, according to the datasheet for these sensors, it also has an exceptional temperature range, operating between 1.8 Kelvin (-271.35OC) to 353 Kelvin (80OC), which will allow these magnets to be used in the liquid helium temperature range (~4 Kelvin), allowing the measurement and monitoring of normal and superconducting magnets. Furthermore, the datasheet shows other impressive characteristics:
- Low power (maximum supply current of 1mA)
- Worst-Case resolution of 7ppm
- High Sensitivity (1100 V/AT (Volts per Amps*Teslas))
- Measurable field range of up to 9 Teslas
- 0.5% Linearity of response
With these sensors, CERN is looking to create novel magnetic field mapping systems via Paragraf’s two-dimensional Hall-Effect sensors. With continued rigorous testing, the partnership between CERN and Paragraf could help change the landscape of magnetic field sensing and measurement.
According to a news release from Paragraf, CERN’s Magnetic Measurement section is looking to perform more in-depth tests on the Hall effect sensors, with the eventual aim of using them to build a novel mapping system for magnetic fields.