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.
For volcanic gas monitoring in situ, instrumental mass spectrometry requires reliability and ruggedness combined
with low power usage and portability. The Volcanic Gas Analytical Monitor (VGAM) is capable of quantitative
molecular analysis of a variety of atmospheric and volcanic gases in a single sensor by ion trap mass
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
previous field instruments using magnetic sector and quadrupole mass spectrometers (MS) with vacuums backed
by compact turbomolecular pumps, the VGAM uses a low-power autoresonant ion trap MS and NEG-Ion vacuum
that operate at only 25 W total power, which is often the power requirement for just the mass spectrometer. Ratio-
metric mass spectral response is combined with total pressure measurements to report absolute partial
pressures. Data are generated in real time and are recorded to internal flash memory. Relatively low power (<1
Watt) data telemetry to remote sites is possible. Analysis of volcanic plumes, fumaroles, and solfatara fields is
accomplished by direct inlet of gases, after trapping as much excess water vapor in both the external and internal
foreline as possible. We report herein on the VGAM auto-run and post-processing procedures, initial calibration
results for CO 2 , and the results of a brief field deployment at Sulphur Banks solfatara field, Kilauea Volcano,
Hawaii.