- Calibrating NMR system with water
- by changing NMR level
- after found the peak on level = 150, measure the FID area in successively.
- the pulse may not be optimized. the 1st pulse gave FID area = 25, and 2nd pulse gave FID area = 7, 3rd pulse gave 5.
- Observed the Coil Relaxation signal depends on the coil impedance. there is a characteristic peak to indicate the change in impedance. it can be used to measure the impedance.
- the Coil was wrapped by Teflon tape and fastened the copper wire. Adhesive was used to fix the join of the coil and cable. the insertion mechanism was fixed by optics mounting.
- the characteristic peak does not change so much. thus, we have confidence that the variation on NMR signal is NOT by the coil.
- the microwave delay time was measured. since it is not easy to have trigger on -10 us after the laser pulse end. we use 0us instead.
- the microwave power is optimized at 1.0W
- Laser pulse duty and chopper frequency.
- Laser polarization angle
- the change is smaller then signal fluctuation.
Wakui San comments
- Laser mode
- the laser is running at multiline mode, but the power detector is at 514.5nm
- Crystal expired
- the crystal we use is about 5 years ago
- have to measure the statistics of the data, due to a improvement of the coil.
- Crystal orientation
- laser pulse duty
- NMR pulse calibration by water
- T1 and T2 measurement
- Q-factor of the coil
- more detail measurement on each parameters
- thermal polarization
- the coil is being fixed, we are able to have a more reliable data. we have to find out the statistics. we can compare with a previous data @ Puw = 1.0 on June 3rd, we had collected 15 data for same setting and the s.d. is 30 unit.
- To have the absolute polarization measurement
- we have to lower the variation of signal
- we have to lower the noise level
- we have to get same setting for the NMR system
- pulse time
- Forward and Backward power
- the change of FID area due to change of external H-field
- the data shown the angular frequency is pi per 30us, about 0.1 rad per 1us.
- the angular frequency for proton is 267.5 rad per Tesla
- if the field change for 1%
- the change of the angular frequency will be 2.67 rad per us
- or to say, the fluctuation of the field should be less then 0.05%
- In order to preform Fourier transform, or the Finite time Fourier Transform, we can use wavelet analysis.
- Before polarization transfer to 13C, we have to optimize the system.
- the sample NMR signal is not flowing sine and cosine function
- it it due to crystal field