We designed and tested an HTS SQUID magnetometer using resonant coupling of a copper pickup coil cooled at T = 77 K. The pickup coil was made of a twisted multi-filamentary wire, the so-called Litz wire, to prevent the increase in coil resistance at high frequencies. First, we measured the coil characteristics in the frequency range from DC to 100 kHz when the diameter df of the elementary filament of the Litz wire was varied between 0.04 and 0.2 mm. We showed that the coil characteristics at high frequencies can be improved when the diameter df is reduced. Next, we constructed a magnetometer using a pickup coil with an average diameter D = 45 mm and number of turns N = 150. The measured magnetic field noise of the magnetometer was 3.3 fT/Hz 1/2 at a resonant frequency of fr = 10.15 kHz. The Q value of the resonant circuit was Q = 153. The experimental results agreed well with the designed value. The obtained high sensitivity of the magnetometer is expected to be useful for its application to low-field NMR.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering