Of course one possibility is that something in the ABS moves
when the BLAST field is on. Vz is particularly keen on this(!)
This could be the sxpoles or maybe even the MFT, creating an obstruction.
We checked w/ ernie, who believes this is not happening. It could be
in principle checked through the glass port.
-- tancredi
________________________________________________________________________________
Tancredi Botto, phone: +1-617-253-9204 mobile: +1-978-490-4124
research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
On Sun, 15 Dec 2002, Tancredi Botto wrote:
>
> It becomes clear that we lose about 40-50 % of the ABS
> flow by running at full current. We monitored dissociator
> operation with a pion-diode mounted after a filter for the
> first balmer line.
>
> The pion diode show some response to different RF power at dissociator. We
> monitored the dissociator operaation as a function of current in the blast
> coils. The pin diode measuraments are consistent with a minimal change of
> the power in the discharge, could be 20W at maximum. However the ABS
> flow decreases. Note sextupoles are on, the atomic signal would be too
> weak with out them.
>
> We agree that there are 3 possibilities left, all other things being
> constant:
>
> _ The dissociation changes with the BLAST field. The pin diode
> measuraments are consistent with no change. But they would become
> hard proof only if they do see a change. However we really have no
> other way to check dissociation since the QMS is also not good.
> (note, the QMS is a long shot, 7-8 mt below the nozzle)
>
> _ Since the sxpoles are in, we lose atomic focussing with blast field
> on.
>
> _ LIGIT is fooling us and the flow is actually not changing.. But this has
> never been observed before, although ligit is affected by the target
> holding field. Ligit baseline pressure does not change. We are going to
> check it anyways
>
>
> We confirmed our flow estimates of yesterday with blast data (normalized
> elastic yield), lifetime and again with ligit. The atomic flow can
> be at most 1.0-1.2 E16 At/s. This is a factor of 6 below maximum ABS
> flow.
> This is for 70 SCCM input gas, 300 W on the dissociator. By subtracting
> a baseline pressure for when the dissoc RF is off we get the following
> differential flows
>
> dissoc. delta-p
>
> 30 SCCM, 300 W 5.2E-8
>
> 70 SCCM, 300 W 6.4E-8
>
> 90 SCCM, 300 W 5.9E-8
> 90 SCCM, 400 W 6.4E-8
>
>
> note, the delta-p signal is x10 times that of last week.
> We decide to leave things at 70 SCCM, 300 W.
>
> Tomorrow we should finally adjust the nozzle position, which is our
> last handle on the intensity optimization. (note, today we were not
> fully ready to do this).
>
> -- VZ, TB
>
> ________________________________________________________________________________
> Tancredi Botto, phone: +1-617-253-9204 mobile: +1-978-490-4124
> research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
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