Performance of HTS SQUID coupled to cooled-Cu/superconductor pickup coil

We studied the performance of a magnetometer composed of a high Tc SQUID and a large pickup coil. For the pickup coil, we consider the coil made of a cooled Cu wire or an HTS superconductor tape. A magnetometer was designed for geophysical measurement using transient electromagnetic method. The theoretical field noise of the magnetometer was 0.2-1 pT/Hz1/2 at f = 10 Hz, and 55 fT/Hz1/2 for f > 200 Hz when the pickup coil of 100 mm in diameter and of N = 50 turns was used. Preliminary experimental results using the pickup coil made of the HTS Bi-tape reasonably agreed with the theoretical prediction.