An ultra-sensitive and wideband magnetometer based on a superconducting quantum interference device

Abstract

The magnetic field noise in superconducting quantum interference devices (SQUIDs) used for biomagnetic research such as magnetoencephalography or ultra-low-field nuclear magnetic resonance is usually limited by instrumental dewar noise. We constructed a wideband, ultra-low noise system with a 45 mm diameter superconducting pick-up coil inductively coupled to a current sensor SQUID. Thermal noise in the liquid helium dewar is minimized by using aluminized polyester fabric as superinsulation and aluminum oxide strips as heat shields, respectively. With a magnetometer pick-up coil in the center of the Berlin magneti- cally shielded room 2 (BMSR2) a noise level of around 150 aT Hz${}^{-1/2}$ is achieved in the white noise regime between about 20 kHz and the system bandwidth of about 2.5 MHz. At lower frequencies, the resolution is limited by magnetic field noise arising from the walls of the shielded room. Modeling the BMSR2 as a closed cube with continuous μ-metal walls we can quantitatively reproduce its measured field noise.

4 pages, 3 figures

References in corpus (4)

• Calculation of Magnetic Field Noise from High-Permeability Magnetic Shields and Conducting Objects with Simple Geometry
• SQUID-based instrumentation for ultra-low-field MRI
• A modular, extendible and field-tolerant multichannel vector magnetometer based on current sensor SQUIDs
• Nearly quantum limited nanoSQUIDs based on cross-type Nb/AlOx/Nb junctions

Cited by in corpus (5)

• Precision Magnetometers for Aerospace Applications
• High-Tc superconducting detector for highly-sensitive microwave magnetometry
• Demonstration of full tensor current density imaging using ultra-low field MRI
• Ultra-sensitive SQUID systems for pulsed fields - Degaussing superconducting pick-up coils
• SQUID current sensors with an integrated thermally actuated input current limiter