The Positioning of Magnetometer Pickup Coil in Dewar by Artificial Signal Source

IEEE Trans. Appl. Supercond.

Shimozu

Kawabata

et al. 2005

We have fabricated and characterized nine Superconducting Quantum Interference Device (SQUID) magnetometers, which were integrated on a single chip. The magnetometers are based on a directly-coupled multiloop SQUID with Nb Al AlO x Nb junctions, and are arranged in a 3 3 matrix in the area of 10 mm 10 mm. The diameter of the circular pick-up loop of each magnetometer is 2.5 mm and the distance between neighboring magnetometers is 2.75 mm. In the operation with a flux locked loop (FLL) with direct voltage readout, typical flux-locked noise level of less than 3 10 6 8 0 Hz in the white region were obtained with the magnetometer in a superconductive shield. From the calibration of the sensitivity, typicalfield noise was measured to be 7 fT Hz. In combination with a small cryostat, we expect that this magnetometer will be useful for multi-channel measurement of magnetic fields requiring highly spatial resolution in various applications.

Section: Discussionmentioning

confidence: 97%

“…All SQUIDs in the chip were calibrated in a glass fiber reinforced plastic (GFRP) cryostat by using several three-dimensional coils to which 80-Hz sine current was applied [10]. The field sensitivity of each SQUID was calibrated to be ranging from 2.14 to 2.20 .…”

Section: A Squid Parametersmentioning

confidence: 99%

Fabrication and Characterization of an Integrated 9-Channel Superconducting Quantum Interference Device Magnetometer Array

IEEE Trans. Appl. Supercond.

Shimozu

Kawabata

et al. 2005

“…Calibration of a SQUID chip Figure 6a shows the experimental setup, including a Circular Current Array System (Higuchi et al 1989;Yoshida et al 1994;Adachi et al 2014), for the calibration of a SQUID sensor. The measurements were made in a magnetically shielded room of two-layered PC permalloy with a shielding factor of 1/100 at 1 Hz.…”

Section: Calibration and Evaluationmentioning

confidence: 99%

“…The current control unit switched the current from one coil to another in sequence, and the SQUID sensor voltage was measured and stored for further analysis. Figure 6b presents the known parameters (normal vectors n c i , position vectors r c i , radius a, and current j of the magnetic field-generating coils) and the unknown parameters (normal vector n g , position vector r g , and sensitivity S of the SQUID magnetometer pickup coil) used to estimate the sensitivity of the SQUID sensor (see Higuchi et al 1989). The best estimate of the sensitivity was 722.6 nT/V (Kawai et al 2016).…”

Section: Calibration and Evaluationmentioning

confidence: 99%

Scanning SQUID microscope system for geological samples: system integration and initial evaluation

Oda

Miyamoto

et al. 2016

Earth Planets Space

We have developed a high-resolution scanning superconducting quantum interference device (SQUID) microscope for imaging the magnetic field of geological samples at room temperature. In this paper, we provide details about the scanning SQUID microscope system, including the magnetically shielded box (MSB), the XYZ stage, data acquisition by the system, and initial evaluation of the system. The background noise in a two-layered PC permalloy MSB is approximately 40-50 pT. The long-term drift of the system is approximately ≥1 nT, which can be reduced by drift correction for each measurement line. The stroke of the XYZ stage is 100 mm × 100 mm with an accuracy of ~10 µm, which was confirmed by laser interferometry. A SQUID chip has a pick-up area of 200 μm × 200 μm with an inner hole of 30 μm × 30 μm. The sensitivity is 722.6 nT/V. The flux-locked loop has four gains, i.e., ×1, ×10, ×100, and ×500. An analog-to-digital converter allows analog voltage input in the range of about ±7.5 V in 0.6-mV steps. The maximum dynamic range is approximately ±5400 nT, and the minimum digitizable magnetic field is ~0.9 pT. The sensor-to-sample distance is measured with a precision line current, which gives the minimum of ~200 µm. Considering the size of pick-up coil, sensor-to-sample distance, and the accuracy of XYZ stage, spacial resolution of the system is ~200 µm. We developed the software used to measure the sensor-to-sample distance with line scan data, and the software to acquire data and control the XYZ stage for scanning. We also demonstrate the registration of the magnetic image relative to the optical image by using a pair of point sources placed on the corners of a sample holder outside of a thin section placed in the middle of the sample holder. Considering the minimum noise estimate of the current system, the theoretical detection limit of a single magnetic dipole is ~1 × 10 −14 Am 2 . The new instrument is a powerful tool that could be used in various applications in paleomagnetism such as ultrafine-scale magnetostratigraphy and single-crystal paleomagnetism.

“…The positions and directions of the coils are already known. Therefore, every sensor is positioned and calibrated by analysis of the detected signals [12].…”

Section: Calibration Of Sensorsmentioning

confidence: 99%

Measurement of spinal cord evoked magnetic fields by vector SQUID biomagnetometer

Adachi

Miyamoto

Electrical Engineering Japan

et al. 2006

SUMMARYBiomagnetometry is a powerful method for the investigation of neural activity. We developed a multichannel superconducting quantum interference device (SQUID) biomagnetometer system for measurement of the evoked magnetic field from stimulated spinal cords. The system is equipped with three dimensionally configured SQUID vector gradiometers, which can detect not only the radial components of the magnetic field applied to the subject but also the tangential components. With the system, we could successfully observe the distribution of the evoked magnetic field corresponding to neuronal signals propagating in the spinal cords of small animals in the form of momentarily changing vector maps.