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Update on HBD Gas Transmittance HBD Group meeting 6/9/09

B.Azmoun, S.Stoll BNL. Update on HBD Gas Transmittance HBD Group meeting 6/9/09. Most Recent Scan. Anlz: H=0.0ppm, O=0.3ppm Trans: H=0.0ppm, O=0.0ppm %Int. Trans (Fit: 112-186nm)=100.0% %Int.Trans. (Data: 134-168nm)=102.2%. Anlz: H=6.8ppm, O=3.3ppm Trans: H=31.6ppm, O=4.1ppm

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Update on HBD Gas Transmittance HBD Group meeting 6/9/09

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  1. B.Azmoun, S.Stoll BNL Update on HBD Gas TransmittanceHBD Group meeting 6/9/09

  2. Most Recent Scan Anlz: H=0.0ppm, O=0.3ppm Trans: H=0.0ppm, O=0.0ppm %Int. Trans (Fit: 112-186nm)=100.0% %Int.Trans. (Data: 134-168nm)=102.2% Anlz: H=6.8ppm, O=3.3ppm Trans: H=31.6ppm, O=4.1ppm %Int. Trans (Fit: 112-186nm)=88.4% %Int.Trans. (Data: 134-168nm)=92.6% Anlz: H=4.1ppm, O=1.3ppm Trans: H=27.6ppm, O=4.5ppm %Int. Trans (Fit: 112-186nm)=89.3% %Int.Trans. (Data: 134-168nm)=95.3% Ever since the flow rate was increased to ~4lpm just before the start of the run, the ppm values in both arms have remained more or less stable.

  3. Transmittance History

  4. Losing Wavelength Range! • Lamp could use polishing, which may fix the fact that the HBD-In Trans. value on slide 2 • goes a bit over 100% near 160nm. • However, polishing the lamp will not fix the shrinking WL range of the instrument. • During run 7 a reasonable trans. spectrum could be obtained in the WL range: 125 - 180nm. • Now this range has been reduced to about 140-170nm. • The loss in range is due to the fact that there is simply very, very little signal at • the tails of the lamp spectrum, as highlighted above in green. Polishing the lamp does not • improve the signal in this region. • Perhaps the additional mechanical components in this particular spectrometer (incl. the moveable • mirror) have lubricants which outgass over time and deposit on the optics • We’re looking into getting a new lamp to see if this helps (maybe there is a growing • deposit within the inner surface of the lamp window)

  5. Elevated Temp. Study Anlz: H=20.9+ppm, O=5.0+ppm Trans: H=27.8ppm, O=5.2ppm %Int. Trans (Fit: 112-186nm)=88.9% %Int.Trans. (Data: 134-168nm)=88.2% Anlz: H=15.0+ppm, O=3.0+ppm Trans: H=22.3ppm, O=3.5ppm %Int. Trans (Fit: 112-186nm)=91.3% %Int.Trans. (Data: 134-168nm)=89.3% Anlz: H=2.2+ppm, O=1.1+ppm Trans: H=1.2ppm, O=1.8ppm %Int. Trans (Fit: 112-186nm)=98.6% %Int.Trans. (Data: 134-168nm)=96.5% • Temp of entire hutch (doors closed) was raised such that the temp of the trans. gas cells increased from ~ 20 to 25 C • The analyzer water levels shot up to 20ppm on the West and 15ppm on East in just a few hours. • (Keep in mind that the analyzers are located at a high location within the hutch, which got quite warm • during this test and may have exceeded 25C, but not by much) • The Trans. values, however, remained stable (ie equal to the values obtained at 20C) • These observations appear to contradict the hypothesis that water vapor is condensing on the gas cell windows and is responsible for the discrepancy observed between the trans. ppm values and the analyzer ppm values. It’s still plausible, however that an unknown absorbent substance is responsible for this discrepancy. • Apparently a lot more water outgasses from the plumbing near the analyzers, than from the gas cells. This at least confirms for us that the levels of water observed in the trans. scans is not coming from the cells themselves, but rather from the gas that flows through the cells, ie from the HBD.

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