Technique for Measuring Megagauss Magnetic Fields Using Zeeman Effect

Rapidly varying magnetic fields with peak values in the range from 1 to 5 MG are measured by use of a sweeping image spectrographic method. Atomic spectral lines from an exploding wire light source situated in the experimental region are recorded as the magnetic field varies in a few microseconds from a moderate initial value of a few tens of kilogauss to the peak values. Field measurements are generally accurate to within 2–3% as determined by the consistency of measurements made from several different spectral lines. The sodium D lines and the indium I 4102 Å line have proven to be exceptionally useful for field determinations. The highest field determined to date by this method is 5.1 MG, corresponding to a measured separation of 164 Å between the centers of the shorter and longer wavelength doublets which the NaD lines assume in very high fields. The doublets, of approximately 4 Å separation, are not themselves resolved.