Hi,
evaluation of the target polarizations from all D2-ABS runs 13475-13479
13481-13488 (2 shifts) gives the following results:
Q=2.03 kC,
A_ed_V Point Asymmetries vs Q2 Sector L: 0.164121 +- 0.0534603
A_ed_V Point Asymmetries vs Q2 Sector R: 0.210649 +- 0.0373942
Pzz Fitted from L/R difference 0.061237+-0.121475
Concluding, Pzz is consistent with zero, hPz is really much smaller than
claimed yesterday.
About the target density:
Running show_deep_asym_all.C on new runs 13475-13479 13481-13488:
Total charge in all files : 2032.37 C
Rate of events passing d(e,e'p)n cuts : 45.9419 events/C
Rate of events passing QE d(e,e'p)n cuts : 10.535 events/C
Running show_deep_asym_all.C on October runs 12115-12120:
Total charge in all files : 2750.76 C
Rate of events passing d(e,e'p)n cuts : 10.7443 events/C
Rate of events passing QE d(e,e'p)n cuts : 3.54702 events/C
Concluding, the target density has increased by a factor 3!
The fact that Genya gets a lower elastic-ed yield may be due to
miscalibration of the timing for ed event selection, while the d(e,e'p)
analysis does not depend on this.
So, the FOM is still lower than in 2004, however now it is due to a low
polarization (have we cooked the cell already?) and not because of a low
density. The question is if the polarization can be improved before we
rush and replace the cell again. Maybe running with 70% of the present
flow would help (which still provides the aimed factor of 2 in density)?
I suggest to try to tune the beam with empty target until a lifetime of
>30 min is achieved. Then check how much flow can be used such that the
lifetime would not drop below 20 minutes. Then measure the polarization
again.
Regards,
Michael
--+-------------------------------------+--------------------------+ | Office: | Home: | |-------------------------------------|--------------------------| | Dr. Michael Kohl | Michael Kohl | | Laboratory for Nuclear Science | 5 Ibbetson Street | | MIT-Bates Linear Accelerator Center | Somerville, MA 02143 | | Middleton, MA 01949 | U.S.A. | | U.S.A. | | | - - - - - - - - - - - - | - - - - - - - - -| | Email: kohlm@mit.edu | K.Michael.Kohl@gmx.de | | Work: +1-617-253-9207 | Home: +1-617-629-3147 | | Fax: +1-617-253-9599 | Mobile: +1-978-580-4190 | | http://blast.lns.mit.edu | | +-------------------------------------+--------------------------+
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