Hauke,
This morning we removed the skimmer and modified
it from a 3.8 mm hole to a 6.7 mm hole. We have it
back together and cooling as on 9:30 am. Vitaly
has made a plasma already.
The hall will be closes ASAP.
Ernie
Hauke Kolster wrote:
>
> Hello everybody.
>
> We have connected the ABS to the target chamber and I have
> studied the ABS intensity into the target chamber during
> the past three days. I looked into the intensities for
> H and D with
> - BLAST toroid field off and on,
> - sixpoles in and out,
> - MFT transition on (H only).
>
> The framework is the following:
> - I measure the pressure increase in the traget chamber due
> to the ABS injection. The pumping speed of the pumps can be
> derived from the pressures during unpol running: p=4x10^-6
> at Q=1sccm H2 => S = Q/p = 3125 l/s.
> - A injection of Phi=6x10^16 1/s atoms is equal to 3x10^16 1/s
> molecules from the ABS jet. The expected increase in the target
> chamber pressure from this flow is dP = 3.84x10^-7 Torr.
> We can measeure this increase by moving the sixpole systems
> in and out.
>
> We measured for H and D with BLAST toroid off an increase in
> pressure of dP = 0.2x10^-7 Torr eqv. to 0.38x10^16 atoms/s. That
> is about a factor of 20 lower than the value we expect for the
> ABS in normal operation and a factor of 7 lower than what we
> saw in the compression tube measurements.
> If we turn on the BLAST field this number reduces even further
> by a factor of 4 to 0.05x10^-7 Torr eqv. to 0.09x10^16 atoms/s,
> consistent for both gas types H and D.
>
> I think that this is again related to the alignment of the
> ABS components nozzle-skimmer-collimator to the target chamber.
> The present alignment could be worse compared to the setup during
> the compression tube measurements and the misalignment could
> be caused by opening the chambers last week.
> The difference in signal between Blast toroid on and off might
> be caused by a motion of the chambers in the magnetic field. We
> have a big magnet in the chamber but no support of the chamber
> sideways. The chamber support is only designed to fight gravity.
> Even a small bend in the chambers can reduce the already small
> signal even further.
>
> I talked to Ernie tonight and we agreed on pulling out the
> skimmer tomorrow morning and see if we can gain intensity by
> having fewer restrictions. This should be finished within a few
> hours. During the next days we also have to work on a solution
> for a better alignment of the nozzle and work out a way to make
> the nozzle moveable so we be able to adjust the position based
> on a intesity signal.
>
> I don't know if I can reach everybody now (probably not - its
> 9:30pm) who should be part of the decision to interrupt data
> taking. Ernie will talk to people tomorrow morning about the
> access to the
> hall.
>
> Hauke
>
> ---------------------------------------------------------------
> 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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