the experiment condition is :

Magnetic field ( no actual value )

  • control voltage = 3.069V
  • supply current = 15.28A
NMR system
  • frequency = 12.8MHz ( indicated that the B field is 0.3T )
  • pulse width = 5 μs
  • level = 150
  • gain = 35dB
  • LPF = 100kHz
  • phase = 90º
Laser
  • power = 4 W
  • current =31.3A
  • chopper frequency = 3.5kHz
  • pulse width = 55μs
Microwave
  • frequency = 9.05MHz
  • Amplify ratio = change
  • power = change
  • delay time = change
  • pulse frequency (width ) = 31.5kHz (16 μs)
Field Sweep
  • Peak to Peak voltage = 5V
  • phase = 180º
  • voltage supply = ± 40V
  • current supply = 0.6A
  • delay time = microwave delay time + 6μs
  • pulse frequency = 30kHz
Total polarization time = 300s

The first parameter to change is the microwave power. we use microwave pulse width at 15.87μs and delay time is 27μs. the field sweep delay time is 33μs.

we found out that the optimum condition is 3.0W to 3.5W, step 0.5W, with amplify ratio from 4.25 to 4.68.

then we set the microwave power to 3.5W and change the microwave delay time from 17μs to 37μs, step 5μs. we found that 27μs is optimum.

during the experiment, the NMR signal was gone or decreased. we believe that the Magnetic field changed. we turn off the magnetic field for 5 mins, then turn the control voltage to 5V for 10 min, then turn back to 3.069V. by this, we get back the NMR signal with similar strength.

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