Abstract
The paper deals with magnetic field mapping outside a finite length solenoid electromagnet, by an in-house designed and calibrated inductive pick-up or search coil. The search coil is calibrated in a unique methodology based on the azimuthal magnetic field component generated by a straight wire. This unique calibration technique helps us to avoid additional circuitry to integrate the signal obtained from search coil. The methodology proves advantageous in diffusion, implosion studies where the signal frequency changes with dimension and material of experimental job-piece (hollow metal tube). Remedial measures have been taken to avoid electrostatic capacitive pick-up (which eventually exacerbates with integration) keeping measurement simple and accurate. The experimentally measured field values have also been compared with electromagnetic field results obtained from mathematical calculations and finite element based simulations. Two different mathematical approaches have been demonstrated for field computation based on Biot-Savart Law. Both the methods have taken into account the exact geometry of the solenoid, including the inter-turn gaps. The methods use appropriate combination of closed-form mathematical expression and numerical integration techniques and are capable of determining all the vector components of magnetic field anywhere around the finite length solenoid. The mathematical computations are equally significant contributions in the paper especially because exact determination of magnetic fields outside finite length solenoids has not been discussed in sufficient specific details in already existing literature. The mathematical computations, finite element simulations and experimental verification together provide a holistic solution to magnetic field determination problems in pulse power applications that have not been discussed in available literature or books in specific details.
Highlights
The magnetic field studies of a finite length solenoid, outside the solenoid, in spite of its importance in many spheres of research and development, are very scarcely researched into
The mathematical computations are significant contributions in the paper especially because exact determination of magnetic fields outside finite length solenoids has not been discussed in sufficient specific details in already existing literature
The mathematical computations, finite element simulations and experimental verification together provide a holistic solution to magnetic field determination problems in pulse power applications that have not been discussed in available literature or books in specific details
Summary
The magnetic field studies of a finite length solenoid, outside the solenoid, in spite of its importance in many spheres of research and development, are very scarcely researched into. Computation of magnetic field around finite solenoid as discussed in [5,6,7,8] involves determination of the same by evaluating magnetic vector potential. The present work elucidates two separate computational methodologies involving direct determination of the magnetic field from Biot-Savart law. Pulse magnetic field measurements have been physically carried out and the results obtained have been compared with the computed values. Pulsed magnetic field measurement is generally performed by inductive principle (i.e. by the help of a search coil [4,9,10,11,12]). Novickij [11] has compared the results of the search coil with La0.67Ca0.33MnO3 sensor (employing colossal magneto-resistance principle). Electrostatic pick-up signal, which on consequent integration worsens measurement, would not be a cause of JEMAA
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