High-Gain Wide-Bandwidth Ultra-Low-Noise SQUIDs (Superconducting Quantum Interference Devices) for NDE (Non-Destructive Evaluation)

Magnetic fields can be measured with induction coils and fluxgate magnetometers. However, in certain cases, the magnet field signals are so weak that more sensitive magnetometers are needed to properly measure magnetic field from biological samples. In addition, there are no established techniques or systems, which can measure both intrinsic and induced magnetic signals from biological samples. This SBIR project addresses the development of a prototype MR/MS Imaging system for biological applications. While we will focus on the imaging applications, the system can also be utilized for NMR (Nuclear Magnetic resonance) spectroscopy. The proposed system uses digital SQUIDs (Superconducting QUantum Interference Devices) as its imaging sensors. SQUIDs are extremely sensitive detectors of magnetic flux and have been used extensively to detect weak biomagnetic signals in MSI. The minimum energy sensitivity for SQUIDs is close to the quantum limit h (Planck’s constant; 6.6262 x 10-34 J/Hz). All recent measurements of weak magnetic fields utilize SQUID magnetometers. Inductive coils measure the rate of change of flux with time, and therefore, have vanishing sensitivity as the frequency goes to zero. By contrast, SQUIDs measure flux directly and can detect changes in flux at any rate including extremely low frequencies. The response of SQUIDs is constant over its entire bandwidth, which extends down to and includes DC (or static fields). Recent research has shown that these SQUID-based sensors may also be used to measure the very weak magnetic signals in MRI systems. These two imaging technologies (MSI and MRI) will be combined to produce an unparalleled functional imagery for biological systems. An MSI requires an extremely low magnetic field ambient with superconducting pick-up coils. To accommodate these requirements, we design, manufacture, and replace the pick-up coil of a conventional MRI system with a novel cryogenic nano-pickup coil, which is superconducting at low magnetic field for MSI and highly conductive for MRI at high magnetic field. The system will be optimized for imaging of magnetic fields at the scale of 50 m. For MR imaging, a cryogen-free current-driven high-field superconducting magnet will be procured, which can be instantaneously demagnetized to accommodate MS imaging in a magnetic field-free environment. Peripheral electronics, such as gradient coils and imaging software for our imaging system, will be provided by MR Solutions under an on-going collaborative agreement for current projects at Hypres. The receiver for the proposed imaging system will be based on an integrated array of digital SQUID sensors, which include superconducting analog-to-digital converters (ADCs) with much higher dynamic range (numbers of bits) than conventional ADCs. The magnetic imaging system with the new advanced nano-SQUID allows Hypres to extend its capabilities and establish the instrumentation techniques required for a rapid-cycle commercial capability to develop low-noise, integrated thin film SQUIDmagnetometers and gradiometers for biomedical instrumentation, which will lead to new insights into cellular biology.