Highlights of ABS meeting for Dec 3, 2003
- ABS intensity:
The Flux of ABS is not affected after installation of the target cell,
see my response to BLAST meeting minutes this morning:
"... the ABS intensity was probably
not reduced after we put the cell in. Instead the calibration of the
unpol gas feed system that was carried out without the cell cannot
be applied to measurements of the ABS intensity with the cell in
place. The reason is that the cell directs about 1/3 of the gas back
into the ABS leading to a lower pressure in the target chamber.
Without cell only a small fraction streams back and we have a higher
reading on the target pressure."
The Target chamber was used as compression tube for ABS flux
calibration. A pressure of 2.5e-7 torr in target chamber was measured
without the cell installed. With the target cell installed in the
chamber we measured today 1.8e-7 torr. The background is typically
in the order 0.1e-7 torr.
A comparison of the two measurements (background subtracted) shows a
consistent picture: 2.4e-7 * 2/3 = 1.6e-7 torr compared to 1.7e-7 torr.
A pressure of 2.4e-7 torr corresponds to an injected flux of about
5.5e16 atoms/s. Background corrections such as H2 ballistic flow and
leakage from the ABS into the cell are included in these pressures and
the ABS flux must be corrected for these contributions.
- Target polarization
Vitaly reported about the total target polarization determined from
recent runs:
P_t = 0.64+/-0.10, cell within +- 20cm
P_t = 0.75+/-0.12, cell within +- 10cm
- RF transitions
The rf transitions operate reliable. No problems were observed after
the
redesign. Some SFT signals still need to be hooked up to EPICS.
Hauke
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