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User name M. Liang
Log entry time 11:00:03 on January 27,1999
Entry number 10756
This entry is a followup to: 10510
keyword=other ideas about low target polarization
The fact that the target polarization went down to ~27% 6 hours after the EPR/NMR measurements and never come back indicates that it's unlikely due to EPR system, but rather the problem in the main system. This is because if EPR had caused any any loss of polarization, one should see it immediately after the measurement, and should be optically pumped back/recovered after several hours. I suggest to check two things in the main system, if one is really concerned and wants to find out the course :
1. cell lifetime. By measuring the cell lifetime one can determine whether the cell has deteriorated during the experiment. Remember the first cell we had during GDH experiment also had problem of getting higher polarization and which later found out due to short cell life time (~10 hrs).
2. the pumping laser. One probably should check both the laser wavelength and laser alignment, including how well the laser is still circularly polarized. The fact that the target polarization didn't go up nor down, if it's not due to the cell itself, could only be explained by inefficient optical pumping.