summary of target activities on Wed.

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User name jpchen

Log entry time 02:53:57 on October 30, 2008

Entry number 245476

Followups:

245490 10/30/08 04:59 Yi Qiang Update on EPR FM sweep

keyword=summary of target activities on Wed.

Last night, Ye/Jin/Chiranjib measured the vertical laser polarization after the last two mirrors and got number of 95-98% (use peak-peak 95%, use RMS 98%). Today after pumping overnight, the polarization increased by another 20% relative. The absolute polarization is still uncertain (12% ?). NMR at the pumping chamber has strong dependence of the target position (probably due to the RF field change). The NMR at the target location is reasonably stable. Ye tried EPR a few times, not working. Increased EPR RF, still not working. Late in the evening (~11 pm), noticed laser absorption spectrum started fluctuate widely, dropping to very low level then went back up. Checked the fiber monitoring temperature and found the one at the end of 5-to-1 combiner was very hot (> 70 degree C (read-out 100, offset 30)). Checked in the hall. The fiber is still intact. Did clean and installed a fan locally to keep it from overheating. Rechecked alignment. Now, Ye/Jin/Chiranjib are working on check EPR. The likely reason for ERP to not working are: not enough D2 light or not enough RF power. First check the EPR spectrum to see if there are enough D2 light. Will also try direct photo-diode. If still not working, then try RF impendance match to increase RF power.