A new method to measure the local magnetic field strength internal to a plasma is described using cross correlation of ordinary (O) and extraordinary (X) mode reflectomter signals originating from the naturally occurring turbulence present in all plasma. This method relies on determination of the peak cross correlation between O- and X-mode signals, which are then assumed to originate from the same spatial location. Since the density at cutoff is known from the incident O-mode frequency, the magnetic field may be determined from the X-mode frequency. This method is expected to be widely applicable to many magnetic confinement devices, including those with magnetic fields <=0.2-0.3 T, where application of other diagnostics may be difficult.
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