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A prototype mass spectrometer for in situ analysis of cave atmospheres
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10.1063/1.4761927
/content/aip/journal/rsi/83/10/10.1063/1.4761927
http://aip.metastore.ingenta.com/content/aip/journal/rsi/83/10/10.1063/1.4761927

Figures

Image of FIG. 1.
FIG. 1.

Diagram illustrating the basic assembly of the prototype cave mass spectrometer (CMS).

Image of FIG. 2.
FIG. 2.

Photo of the CMS in the laboratory after removal of cables and post-cave cleaning and decontamination. At far left is the isolation valve connected to the turbopump exhaust port. The inlet filter is visible as a small red dot to the left of the leak valve near the center of the photo. The RGA QMS is to the right in the photo, with the laptop and Ethernet cable used to communicate with the RGA in the background.

Image of FIG. 3.
FIG. 3.

Average instrument background signal in amperes (A) (black line), with error bars to represent the standard deviation as a function of mass. The maximum background signal measured when the pressure was below 1 × 10−7 Torr is illustrated as the gray line and the laboratory air signal with pressure of 1 × 10−5 Torr is represented by the dots. Mass channels where the laboratory air signal is within the range of the background signal are identified as channels in which the air sample cannot be differentiated from the background signal.

Image of FIG. 4.
FIG. 4.

Signal in amperes (A) in mass 28 as a function of the pressure measured by the ion gauge during calibration of the CMS using N2 gas. This allows us to determine the partial pressure of N2 in our field measurements.

Image of FIG. 5.
FIG. 5.

Signal in amperes (A) in mass 28 and the surrounding mass channels at an operational pressure of 5 × 10−5 Torr (black circles) compared to an operational pressure of 1 × 10−7 Torr (gray circles). Note that the mass 27 and 28 peaks are combined in the high pressure scan. This effect requires that we limit the operational pressure to less than 2 × 10−5 Torr.

Image of FIG. 6.
FIG. 6.

Signal in amperes (A) in mass 28 (solid circles) and 40 (solid squares) as a function of the pressure measured by the ion gauge during calibration of the CMS using N2 and Ar gas. The cracking product of N2 in mass 14 (open circles) and of Ar in mass 20 (open squares) is also illustrated. The pressure range is limited to ≤ 1 × 10−5 Torr.

Image of FIG. 7.
FIG. 7.

Mass spectrum of the ambient air outside of the NBC entrance (black line) compared to the mass spectrum measured inside the cave (blue and green circles). The green circles represent the signal due to CO2.

Image of FIG. 8.
FIG. 8.

Mass spectrum of the ambient air outside of the BBC entrance (black line) compared to the mass spectrum measured inside the cave (blue, green circles). The green circles represent the signal due to CO2. The red circles represent the signals that indicate detection of increased O2 and nitric oxide within the cave.

Image of FIG. 9.
FIG. 9.

Mass spectrum of the ambient air beside the well (lines) compared to the mass spectrum measured inside the narrower well (dots).

Tables

Generic image for table
Table I.

Cracking patterns, or the ratio of secondary signals to the main signal, of the major constituents of air observed during instrument calibration and at selected field locations. All values are determined as an average and standard deviation of a select number (N) of samples.

Generic image for table
Table II.

Relative signal of major atmospheric constituents measured during calibration and at selected field locations.

Generic image for table
Table III.

Isotope signals relative to the lighter isotope as suggested by the CMS. The signals for the isotopologues are low and the reliability of these measurements is not ideal for isotopic studies which typically require exceptionally high precision measurements.

Generic image for table
Table IV.

Mass channels identified as dominated by background signal during the laboratory calibration. Some possible minor constituents that would appear in these masses and the percentage of the main peak for cracking products for these are listed. These constituents were not evaluated in the laboratory calibration so the true cracking patterns are not known. Mass signals above the background signal are highlighted in red suggesting possible detection of the constituents.

Generic image for table
Table V.

Organic composition of the atmosphere inside Bracken Bat Cave. Relative abundance is abundance relative to the sum of the total area of all chromatographic peaks passing through the column. The confidence level is a numerical measure of fit of the target compound to the NIST library mass spectrum.

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/content/aip/journal/rsi/83/10/10.1063/1.4761927
2012-10-29
2014-04-16
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: A prototype mass spectrometer for in situ analysis of cave atmospheres
http://aip.metastore.ingenta.com/content/aip/journal/rsi/83/10/10.1063/1.4761927
10.1063/1.4761927
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