An Automatic Spinner Magnetometer with Thermal Demagnetization Equipment.

Abstract

We have developed a fully automated spinner magnetometer which can operate, under the control of a personal computer, the measurement of remanence as well as thermal demagnetization of paleomagnetic samples. A fluxgate sensor and an electric furnace is housed within a three-layer magnetic shield equipped with a solenoid coil. The measurement of the three components of magnetization is made possible by sampling the magnetic field generated by the sample which is both rotating around and moving along an axis parallel to the axis of the magnetic shield. Thermal demagnetization is carried out in an electric furnace placed further away along the axis of translation but still inside the magnetic shield. The rotation and translation of the sample, the measurement of the magnetic field by a ring-core fluxgate sensor, heating and cooling of the electric furnace, and switching on and off of the solenoid magnetic field are all controlled by a personal computer. This instrument is ideally suited for performing paleointensity experiments by the Thellier method because a series of measurements after heating cycles with or without an applied field can be programmed and carried out automatically by computer control.