Measurement of Coil Deformation in Pulsed High Magnetic Field Using a Fiber Optic Interferometer

Measurement of coil deformation in pulsed high magnetic field is an important problem in high power electrical engineering. Small deformations (in the micrometer region) need to be measured with high accuracy using a small footprint (about 1 cm or less) sensor. Unfortunately, high coil current (from several tens of kA and more) and corresponding electromagnetic field create strong interference that makes it nearly impossible to use many types of electronic sensors. Fiber optic deformation sensors are sensitive and not affected by electromagnetic fields and thus are a very attractive solution. Various measurement techniques and their benefits and limitations are discussed. An interferometer using a 3x3 coupler was built, calibrated and used in experiments. The results of experiments with a fiber optic interferometer and a copper coil with currents up to 25 kA are presented.