Emily A Kaplan edited By_changing_the_strength_of__.tex  over 8 years ago

Commit id: 3fe2e62e8c369e4f8f8758e73425e313addc8dd1

deletions | additions      

       

By changing the strength of the polarization field or the polarization time, we could study the effects on precession frequency and magnetization. Keeping the polarization time constant at 4s and varying the current from 0.5A to 3.0A (corresponding to varying polarization field from 7.5 mT to 45 mT), we can determine dependence of precession frequency upon polarization field. We found the precession frequency to be $1.852 kHz \pm 0.018 kHz$ (Eq. \ref{eq:precession}) . We then kept the polarization time constant at 5s since this time produced a large enough amplitude and was in a relatively short time. We also varied the field, measuring the amplitude of the precession data using the method described above. We then fit the data to a linear fit, so we can determine the relationship between polarization time and magnetization. We then kept the polarization field constant at 45 mT and varied polarization time, measuring amplitude and therefore magnetization. We fit the data to Eqn.~\ref{eq:growthrate} to find the rate of polarization of the water molecules. We again kept field constant at 45 mT and varied the polarization time, measuring the amplitude to find the time at which saturation occurs. We could then record the amplitude seen when keeping the polarization at the saturation time (\sim{10}s, see Figure~\ref{fig:measurepolarizationtime}) and varying the current. In this way, we can find the dependence of magnetization on magnetic field. field, as expressed in Eq. \ref{eq:tanh}.