VGAM: Compact and Low Power Mass Spectrometer-based Instrumentation for Volcanic Gas Monitoring

Compact mass spectrometers can provide simultaneous multi-species analysis with high sensitivity and precision.<br> For volcanic gas monitoring in situ, instrumental mass spectrometry requires reliability and ruggedness combined<br> with low power usage and portability. The Volcanic Gas Analytical Monitor (VGAM) is capable of quantitative<br> molecular analysis of a variety of atmospheric and volcanic gases in a single sensor by ion trap mass<br> spectrometry. These gases include: H 2 , He, H 2 O, N 2 , O 2 , Ar, NO, N 2 O, CO, CO 2 , H 2 S, SO, SO 2 , and CH 4 . Unlike<br> previous field instruments using magnetic sector and quadrupole mass spectrometers (MS) with vacuums backed<br> by compact turbomolecular pumps, the VGAM uses a low-power autoresonant ion trap MS and NEG-Ion vacuum<br> that operate at only 25 W total power, which is often the power requirement for just the mass spectrometer. Ratio-<br> metric mass spectral response is combined with total pressure measurements to report absolute partial<br> pressures. Data are generated in real time and are recorded to internal flash memory. Relatively low power (&amp;lt;1<br> Watt) data telemetry to remote sites is possible. Analysis of volcanic plumes, fumaroles, and solfatara fields is<br> accomplished by direct inlet of gases, after trapping as much excess water vapor in both the external and internal<br> foreline as possible. We report herein on the VGAM auto-run and post-processing procedures, initial calibration<br> results for CO 2 , and the results of a brief field deployment at Sulphur Banks solfatara field, Kilauea Volcano,<br> Hawaii.