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Radio frequency magnetometry

The precise measurement of atomic spin states in an alkali metal vapour underpins many quantum technologies, ranging from atomic clocks and quantum memory storage to sensing applications, like magnetometry, an area that has experienced significant progress in the last decade.  

Radio Frequency (RF) atomic magnetometers outperform their counterparts; Superconducting Quantum Interference Devices (SQUIDS) and engineered pick up coils, owing to several factors: 

  • Extreme femtotesla sensitivity to both static (DC) and oscillating (RF) magnetic fields. 
  • Operation at ambient temperatures – SQUIDs require expensive liquid helium or nitrogen to operate. 
  • Low power requirements. 
  • Miniaturisation – RF magnetometers can be scaled down to a few cubic centimetres. 

These advantages are being exploited by NPL to prototype a portable RF sensor with potential to permeate across applications such as defect and object detection via non-destructive testing, geophysics and magnetic field-based navigation, with a wide interest in biomedical sensing. NPL is working with industry to prototype a sensor, with a specific interest in defect detection via non-destructive testing, a high impact and volume market. 

Non-destructive testing 

Within non-destructive testing (NDT) an existing technique, typically eddy current testing using pick-up coils, measures the inductive coupling between an RF magnetic field and electrically conductive/magnetically permeable objects (e.g., metalwork). Radio frequency fields can freely penetrate non-conductive materials like plastic or the ground, making them useful for detecting hidden or buried objects. Low-frequency fields can even propagate deep into metallic structures to detect sub-surface features such as cracks and cavities. The superior sensitivity of RF atomic sensors compared to pick-up coils at low frequencies and sensing volume presents an opportunity in measuring previously undetectable features or at remote distances. 

How can NPL help? 

The National Physical Laboratory (NPL) has over 20 years of experience in developing RF atomic sensors, as well as demonstrating novel and highly practical applications. Our commercial collaborations have already co-developed components of the atomic magnetometer across a UK-based supply chain including:  

  • VSCEL diodes  
  • Silicon wafer-based atomic vapour cells.  
  • Integrated control electronics.  

In addition to work on subcomponents, NPL can work with companies in the biomedical, navigation, NDT and geophysics sectors to adapt highly sensitive portable atomic sensors to their needs. 

Find out more about RF atomic magnetometers in our Quantum Test and Evaluation Short Course describing the fundamental operation of the RF atomic magnetometer and its application to non-destructive testing.  

Contact a member of our quantum team today to schedule a consultation. We can discuss your specific needs and how our quantum technologies can help you achieve your goals.  

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