Transient ElectroMagnetics are widely used by geophysical exploration companies. This active method uses an air coil of some 1000 or 10000m2 to produce magnetic transients. This leads to a major demand for a SQUID sensor: high slew rate. IPHT has developed Low Temperature (LTS) and High Temperature (HTS) SQUID systems for this application. To use the SQUIDs in the production mode of a geophysical workday, the system (cryostat, electronics, power supply) are designed to be robust and allow easy handling in the field.

The LTS SQUD systems for TEM supplied by SUPRACON AG are  used on a routine basis, mainly in South Africa and Australia. They have been proven to be reliable and deliver outstanding results. The directly coupled electronics achieves a slew rate of about 10MΦ₀/s, which corresponds to about 20mT/s, the noise limited resolution corresponds to 20fT/√Hz.

Field trials of different systems with geophysical partners and companies in Germany, Spain, South Africa, Japan, Australia, Portugal and China have been performed successfully and demonstrated the advantages of SQUID systems over conventional coil receivers which are mostly used in geophysics.

The following picture shows a comparison of the SQUID system with a conventional TEM coil. The data were taken in rural environment in northern Germany.