Expanding the capabilities of new magnetometers of ponderomotive and magnetic-rheological types with hemispherical poles

Objectives . The work sets out to explain the expanded capabilities of new magnetometers by conducting appropriate studies. In order to determine the magnetic susceptibility of small-volume objects, ponderomotive and magnetic-rheological magnetometers with hemispherical pole pieces are used to create the magnetic field required for a limited working zone. Methods . The research is carried out using an original method, which includes finding the coordinate characteristic of the induction of the field B through direct step-by-step measurements by the Hall sensor in the interpolar space along the line of action of the ponderomotive force to provide a basis for obtaining the coordinate characteristic of the gradient. Results . In magnetometers using hemispherical poles of increased diameter D: 157 and 184 mm, mutually disconnected from one or another by the distance b, the desired key dependencies of magnetic induction B were experimentally obtained (with a step-by-step distance x from the center of symmetry of the interpolar space along the line of action ofthe ponderomotive force) to provide the dependence ofthe gradient grad B= dB/dx . The characteristic inflection of each of the curves B from x and corresponding individual extremum of the following curves dB/dx from x, in the vicinity of which the values of dB/dx are practically stable, meets the requirement of determining the dislocation of the executive (working) zone such that the inhomogeneity of the field is almost constant. Conclusions . Coordinates of executive zone dislocation are obtained from established and generalized dependencies B from x and dB/dx from x . To calculate these coordinates, which depend on D and b but do not depend on the magnetizing force of the winding, the corresponding analytical (phenomenological) expressions of power and logarithmic form are obtained. The possibility of using these expressions to identify the executive zone of magnetometers without resorting to additional series of experiments is shown. The expediency of using hemispherical pole pieces of increased diameter is also demonstrated. On this basis, the length of the executive zone can be increased to conduct studies with samples of a wider range of sizes.