Magnetic (B-dot) Probe
If the magnetic field in the plasma is not stationary, either because the plasma as a whole is transient or because the fields are periodic (radio-frequency heating), the rate of change of the magnetic field with time (, read "B-dot") can be measured locally with a loop or coil of wire. Such coils exploit Faraday's Law, whereby a changing magnetic field induces an electric field. The induced voltage can be measured and recorded with common instruments.
Also, by Ampere's Law, the magnetic field is proportional to the currents that produce it, so the measured magnetic field gives information about the currents flowing in the plasma. Both currents and magnetic fields are important in understanding fundamental plasma physics.
Read more about this topic: Plasma Diagnostics
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