the microwave system was fixed and calibrated so that it resonance with the microwave cavity. the step for turn off the trigger signal is, switch off the RF amp then turn off the trigger. and turn on the trigger voltage then turn the RF amp on. if turn the RF amp first, then the microwave has some noise and unstable.
the phase of trigger voltage also important.
the position of the sample and the NMR coil is unstable, cannot have a reliable placing and make many measurements fail.
suggest after every signal recorded, measure the BG.
- find the crystal angle to the microwave.
- polarized the target
- measure the laser polarization dependency.