What will happen if EPR goes wrong?
Good question. During an EPR measurement, once the 3He spin is reversed, Rb resonance frequency will jump by about 50 KHz. If the electronics is not optimized and lose the lockin, the spectrum shown on LabView screen will look really wierd. However, if one keeps calm and let the program to finish, then we only lose about 2% polarization (relative) due to the AFP spin flip. But, if the program is stopped in the wrong state, which means, 3He spins are reversed to the opposite direction, but are not flipped back, then they will stay in the reversed state, and will depolarize dramatically. For example, the polarization will drop from 40% to 20% in a few hours. For an experienced EPR operator, it is possible to find the resonance again, re-start the Labview program and flip 3He’s back, but it is difficult and 3He’s are very unstable. A small change of the electronics – for example, disconnect RF capacitor (which is the next step of EPR operation procedure) – could push 3He’s to the wrong st
