I am hoping someone (Genya?) will pickup the effort on
installing/instrumenting/understanding the ion clearers downstream of
the target when I am in Germany. A couple of comments. The yield (ion
current) from these devices is completely dominated by the target
thickness. The current 10's of nA seems consistent with ionization cross
sections and earlier yields in the ion polarimeter. The behavior is
very different for polarized and unpolarized operation of the target.
While electronic pickup (error in the instrumentation) is still a
possibility, the yield seems to show a striking strucure at the five
minute interval corresponding to the target flipping frequency. Further
the yield seems to exhibit a behavior with a time constant of a few
minutes. (Thermal in the ABS?) Maybe the recombination rate would affect
the ion current yield....?
We are working on the timing circuit that will identify the mass state,
but this will be a very challenging effort.
TZ
Hauke Kolster wrote:
>
> Hi,
> I had a look at Genya's plot of asymmetry vs. z for the
> hydrogen target that he sent several days ago and tried
> to fit the distribution to calculated values of the
> product of atomic polarization and atomic fraction vs. z.
> I assumed that polarization does not survive in the
> molecules, that the value of 0.08 for the fraction of
> initially unpolarized nucleons in the deuterium target
> can be applied to the hydrogen target. I included the
> distribution of wall collisions for a uniform surface,
> assumed only transitions 1-4 and 2-3 for the wall
> relaxation, included the field dependence of the
> polarization in the individual hyperfine levels and
> also sextupole rejection inefficiencies.
>
> The attached plots show polarization and atomic fraction
> in the left picture and their product compared to Genya's
> data in the right. The plot cellpol_3a.jpg fit was produced
> using the following values:
> - recombination prob. gamma_r = 3.4e-3 +- 0.3e-3,
> - spin flip prob. gamma_p = 1.0e-4 +- 2.0e-3,
> - avg. atomic fract. alpha = 0.45
> - avg atomic pol. P_a = 0.80
>
> and cellpol_3b.jpg was produced using
> - recombination prob. gamma_r = 1.5e-3 +- 0.3e-3,
> - spin flip prob. gamma_p = 5.0e-2 +- 2.0e-3.
> - avg atomic fract. alpha = 0.60
> - avg atomic pol. P_a = 0.57
>
> The main depolarizing effect is clearly caused by recombination
> in the target. The scenario with little wall relaxation and
> high atom polarization fits better to the data and suggests
> strong recombination in the target but weaker wall relaxation
> and high atom polarization.
>
> The situation at the deuterium target might be similar and
> one expects a significant rate of recombination. But the
> target polarization will not be affected if the polarization
> is conserved in the molecules.
>
> Hauke
>
>
>
> -------------------------------------------------------------
> Hauke Kolster MIT * Bldg 26-551 * Cambridge, MA 02139
> kolster@mit.edu Tel (617) 253-2693 Fax (617) 253-9599
> -------------------------------------------------------------
>
> ------------------------------------------------------------------------
>
>
> ------------------------------------------------------------------------
>
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