No abstract

Barkhausen noise ͑BN͒ is measured in an amorphous ribbon in an open magnetic circuit. The experiment is set up in such a way as to obtain the BN signal with a high frequency range and low apparatus noise. The driving field is produced by a pair of Helmholtz coils and the pick-up coil is a low capacity radio coil. The signal is amplified by a custom designed two-stage, battery operated amplifier, which together with the coils and the ferromagnetic ribbon is screened by three coats of soft iron. The data acquisition is done by a 12-bit analog-digital card allowing one to obtain up to 1ϫ10 6 data points with a sampling frequency up to 1 MHz. The correlation dimension of the BN signal is calculated using the Grassberger-Procaccia algorithm and the surrogate data method is used to exclude artifacts. The choice of the measurement conditions and the calculation parameters is discussed. The results show a low dimensionality of the Barkhausen noise that leads to the conclusion that the effect may contain or is caused by a deterministic mechanism. The experimental method allows one to obtain the BN signal over many magnetic reversals so that the repeatability of the results is shown and statistics on the correlation dimension values are performed. ͓S1063-651X͑98͒06106-6͔

The paper presents the recent progress made in the accuracy improvement of the manganin pressure sensors at the Warsaw University of Technology (WUT) and at the Institute of Nuclear Energy. The efforts of the authors were concentrated on three problems: (1) The improvement of the temperature characteristics by the design of a manganin sensor with the temperature compensation achieved by the application of two manganin coils with two different temperature characteristics; (2) The improvement of the calibration process by - (a) using a high pressure deadweight piston gauge (with the correction of effective area versus pressure dependence, built at WUT), - (b) measurements of the manganin resistance as a function of the temperature and of the pressure using a precise multimeter and - (c) application of statistical methods for long series of measurements. (3) The modification of the thermal characteristic by implantation of bismuth and krypton ions.

No abstract