Two Methods About C-field Evaluation in Beam Clock

SummaryTwo new methods related to the evaluation of thermal beam clock's C-field are presented and experiments are shown. The first method measures the stability of C-field locking by using 1-1 line to lock the microwave frequency and 0-0 line to lock the C-field. As the 1-1 line is more sensitive to the magnetic field, such locking makes it easily to see the magnetic field fluctuations after locking. The second method uses a large modulation depth of the microwave frequency locking, so that the frequency points are in the left and right of the Rabi resonance curve instead of the Ramsey fringes. Using this method, we measure the deviation of the center of the Rabi and Ramsey resonance curve, which can evaluate the inhomogeneity of the C-field.