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Joshua E. Thompson.



Design and construction of magnetic coils for in-situ Kerr Measurements in an Instron Materials Tester.



Josh Thompson

Joshua Thompson


Texas State University at San Marcos, Department of Physics, RFM 3228, 601 University Drive, San Marcos, TX78666.


Joshua E. Thompson


Although a significant amount of research has been done to understand magneto-plastic properties of bulk materials applied in transformers, relative little work has been published on the magneto-plastic properties of thin films.  Magnetic thin films are currently being considered for non-destructive testing of oil pipelines, as well as failure detection of sensitive equipment. In previous research magneto-plastic properties of thin films of iron and permalloy coated on top of nitinol sheet metal were investigated [1].  These films have been stressed and tested, but never at the same time. The goal of this research project is to construct an electro-magnet to allow an Instron Material Tester and Kerr tracer to operate concurrently in a way never done before. A basic Helmholtz coil design was initially used, but it soon became apparent the geometry of the tester would limit the ability to maintain the Helmholtz ratios.  Biot-Savart’s Law was used to derive a formula for the magnetic field at the center of two side by side conducting coils of finite dimensions.  A first prototype electromagnet wound from 22 gauge copper wire showed a maximum field of 68 Gauss at 1.7 ampere. Fields over 100 Gauss were obtained after inserting ferrite cores in the coils.  A new electromagnet based on thinner wires that should be able to create fields over 160 Gauss is currently under construction. Replacement vices made of nonmagnetic material and cylindrical ferrite cores are also being fabricated.

Publications and Presentations:

[1] Joshua Thompson, Jonathan Preiss, Wilhelmus J. Geerts, Madhavrao Govindaraju, Design and construction of magnetic coils for in-situ Kerr measurements in an Instron Materials Tester, Undergraduate Research Conference and Honors Thesis Forum, Texas State University April 24, 2015.