Field Strength Characteristics in Single-layer and Multi-layer Solenoids: Basic and Adaptive. The Zone of Uniformity

The problem of identifying the executive zone of the solenoid, i. e. that of its median part with a length of [ L ], where the field strength H is almost constant, is solved in order to conduct research in it. According to the results of the diagnostics of the multilayer solenoids used (four, differing in length L ), the acceptability of solving this problem is shown by adapting the well-known fundamental expression for H in a single-layer solenoid to a multilayer one: by means of a coefficient slightly greater than unity. It was found that, based on the requirement that the H value in the center of the solenoid be very close (with an underestimation of no more than 1-2%) to the potential value (in an infinitely long solenoid), the length-to-diameter ratio should be L/D ≥ 5-7. To determine [ L ], the current value of H on its coordinate characteristic is estimated, which indicates a noticeable (within acceptable limits, in particular, 3%) decrease in H compared to the potential one. The distance x = [ x ] from the end of the solenoid is determined, where, upon the requirement of field uniformity, such a decrease in H , for example, by more than ε = 5%, is hardly acceptable. It is shown that, regardless of the length L of the solenoids, the length values [ x ] of their lateral parts, where the field strength is significantly underestimated, are close, and the relative values [ x ]/ L are subject to feedback from L/D . The dependences for [ L ] and [ L ]/ L on L and L/D are obtained graphically and analytically.