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Plasma Diagnostics

B-dot Probe

A series of loops placed within a time-varying magnetic field that produce a voltage which is directly proportional to dB/dt (or ,"B-dot").


Above: Schematic of a B-dot probe within a time-varying magnetic field.

Above: An ExB calibration device used to calibrate B-dot probes. Electrically biased parallel plates establish a steady electric field while a broadband power amplifier supplies an oscillation drive current to the pair of Helmholtz coils that estabilsh an oscillating magnetic field.

The B-dot probe is a diagnostic used to measuring a time-varying magnetic field. Typical plasma discharges that make use of the B-dot probe techniques include pulsed and inductive plasmas. The basic principle behind the B-dot probe is the idea that a time varying field induces a current in a conducting coil. The output voltage from the coil is proportional to the cross-sectional area, number of turns in the coil and time characteristic of the magnetic field. Integration of the B-dot probe output voltage electronically or numerically (either in the time or frequency3 domain) can yield instaneous magnetic field values, B(t).


Above-left: Closeup photograph of internal 3-axis magnetic field B-dot probe. Above-center: series of B-dot probes and physical scale. Above-right: Series of B-dot probes installed in the XOCOT device. (From ref. 4)

 

Selected Relevant Publications

  1. Peterson, P. Y., Gallimore, A. D., Haas, J. M., "Experimental Investigation of Hall Thruster Internal Magnetic Field Topography," AIAA-2001-3890, 37th Joint Propulsion Conference, Salt Lake City, UT, July 8-11, 2001.
  2. Peterson, P. Y., Gallimore, A. D., Haas, J. M., "Experimental Investigation of a Hall Thruster Internal Magnetic Field Topography," IEPC-01-030, 27th International Electric Propulsion Conference, Pasadena, CA, October 15-19, 2001.
  3. Lobbia, R., and Gallimore, A.D., "Dynamic Electromagnetic Field Measurements of Clustered Hall Thrusters," AIAA-2006-4996, 42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, Sacramento, California, July 9-12, 2006.
  4. Kirtley, D. E., "Study of the Synchronous Operation of an Annular Field Reversed Configuration Plasma Device," Ph.D. Dissertation, University of Michigan, 2008.
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