Thin-film Probe Research Articles

A directionally insensitive thin-film shear-stress gauge

The design and manufacture of a thin-film probe suitable for measuring the magnitude of wall shear stress in three-dimensional flow are described in detail. The probe has been calibrated in a closed rectangular channel using water as the medium. The calibration is linear and repeatable over the wide range of shear stress covered by experiment, and the variation in the probe output is no greater than 0.25% over the 360 degrees rotation of the probe. It is suitable for instantaneous measurements at frequencies of up to at least 10 Hz. Measurements of wall shear stress made in a semi-cylindrical hollow mounted transverse to the main flow are described. These correlate extremely well with similar measurements of shear stress using an electrochemical technique and with the results of a numerical study, thus indicating the suitability of this probe for such measurements.

Application of a network method for nondispersive electron probe x ray analysis of thin films

The network scheme of pulse-height analysis proposed by Mitra and Hall in 1971 can be used in a modified form for the nondispersive analysis of thin films in accord with the electron probe method introduced by Marshall in 1967. The general scheme for n-element analysis and the calibration procedure for the network are presented in this paper. The advantages of the network method for the nondispersive analysis of thick specimens exist equally for the analysis of thin films and the proposed scheme is therefore widely applicable in the field of electron microscopy.A three-channel network apparatus described by Mitra has been used to analyse a Permalloy thin film in order to demonstrate the validity of the new analytical procedure.

Magnetic Field Distribution in a Type II Superconductor

Direct measurements of the magnetic field distribution in the gap between half-ellipsoids of niobium in plastically deformed and annealed states were made using a bismuth thin-film magnetoresistance probe. An empirical equation of the form r−r0=C0B+C1 (eC2B−1) for the field distribution in the deformed sample was found. For the annealed sample, a surface discontinuity of the field was observed, which is a boundary condition for the equilibrium magnetization. Flux jumping was observed when the field was not increased slowly. The distribution in the annealed specimen had reproducible irregularities.