And another thought:
The present cells #1 and #2 have a common problem: The injection
tube was modified in a way that a bare aluminum surface was
exposed and target gas close to the center of the target could
recombine and potentially depolarize on this surface. During the
last installation there has been an attempt to cover this aluminum
surface with teflon but a few hot spots might still be present
affecting the polarization of the atoms as well as increasing the
recombination.
We have to wait for the results on cell #3, and hopefully fix
the problem for this one, before we can conclude that the injected
polarization from the ABS is down by a factor of 5.
Hauke
Tancredi Botto wrote:
> Just one more thought:
> I take our number Pzz ca (15 +- 5) % and I get from genya an atomic
> fraction of ca. 50-60% (of target nuclei). Both numbers have been
> measured in different ways or at different times.
>
> If I am right in my simple arithmetics - even in the scenario that D2
> molecules are *completely* unpolarized (50% dilution) - we arrive at an
> estimated value of the polarization of incoming ABS atoms of only 30 %.
> If BLAST molecules retain 80% of the atomic polarization as at NIKHEF,
> then we would get only 17%.
>
> Measuring the target polarization was the point of the analysis of low-Q2
> data. It still comes up low with the expected 70% which points to the fact
> that there is a problem at the source, before any depolarization in the
> cell. Maybe one of the two states is partly (or not) polarized, maybe
> both are down by an unknown "efficiency" factor.
>
> regards,
> -- tancredi
> ________________________________________________________________________________
> Tancredi Botto, phone: +1-617-253-9204 mobile: +1-978-490-4124
> research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-- --------------------------------------------------------------- Hauke Kolster MIT * Bldg 26-551 * Cambridge, MA 02139 hauke@lns.mit.edu Tel (617) 253-2693 Fax (617) 253-9599 ---------------------------------------------------------------
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