抄録
A new combination system for paleomagnetic measurement incorporates the following four instruments: a ring-core-type flux-gate spinner magnetometer, an alternating field (AF) demagnetizer, an anhysteretic remanent magnetization (ARM) superimposer, and a magnetic susceptibility anisotropy meter.
The system is composed of the following mechanisms and circuits:
(1) a specially designed ring-core sensor and its driving circuits,
(2) a sensor holder incorporating three sets of coils, which are utilized for AF demagnetization, ARM overprinting, and susceptibility anisotropy measurement, respectively,
(3) a mechanism for sample rotation and resetting for 6-spin measurement, using a pair of non-magnetic ultrasonic motors and motor drivers,
(4) a u-metal magnetic shield case,
(5) a dernaguetizing current generator and power amplifier,
(6) a regulated current source for ARM overprinting and maguetic susceptibility aniso-tropy measurement,
(7) a central controller (notebook-personal computer), digital voltmeter, GP-IB Interface, I/O board, and relay board.
In this system, the whole measurement process is controlled by the central computer, which executes the sample rotation and reset during 6-spin magnetization measurement, the ON/OFF and wave-form control of the demagnetizing current during stepwise AF demagnetization, and the ON/ OFF control of the DC magnetic field during ARM overprinting or susceptibility anisotropy measurement.
The noise level of the magnetometer corresponds to 3 × 10−8 kA/m (= emu/cc) for 30 cc samples, using 10 replications of stacking measurement. The maximum field intensity of the AF demagnetizer is 45 mT. The measured results are presented by computer graphics on the screen of a computer immediately after each measurement. The total weight of the system is only about 35 kg, which is light enough for field use.
