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
---------------------------------------------------------------
This archive was generated by hypermail 2.1.2 : Mon Feb 24 2014 - 14:07:29 EST