Robust, highly-sensitive, and extremely selective trace gas sensors are required by the Department of Defense for clean air compliance, environmental impact assessments, chemical weapons detection, biological weapons, identification, security screening, counterproliferation, and force protection applications. Previous laboratory instrumentation was not designed for real-time field use and could not meet these stringent operational requirements.
The objective of this project has been to develop versatile trace gas sensors based on Chemical Ionization Mass Spectrometry (CIMS) and to demonstrate that the instruments meet or exceed the operational requirements.
CIMS is a novel, in-situ technique for detecting trace gases in the atmosphere. It has several unique aspects that provide significant advantages over other point or remote sensing detectors. It is extremely sensitive, giving detection limits as low as 1 part-per-trillion with integration times less than one second. It is highly selective and has excellent immunity to false positive responses or interferences. It is rugged and versatile with an excellent history of performance in a wide variety of field applications. The CIMS technique mixes carefully chosen ions with the gas to be analyzed. These ions react chemically with the target neutrals, converting them to unique tracer ions that are detected with a quadrupole mass spectrometer.
The researchers have used CIMS instrumentation to measure trace gas composition and concentrations in the exhaust plumes of jet aircraft operating at cruise altitudes; the exhaust of jet engines in altitude simulation test cells; the stratospheric exhaust of the Space Shuttle and Air Force Titan and Delta space launch vehicles; laboratory studies of flame quenching by novel fire suppressants; and studies of upper tropospheric/lower stratospheric chemistry. Similar instrumentation has been used to detect volatile organic compounds in ambient air and to perform breath analysis in medical applications. The part-per-trillion sensitivity and consistent and effective rejection of interfering species has given CIMS significant advantages over competing technologies.
The Air Force Research Laboratory (AFRL) has succeeded in developing CIMS into a mature technology that is now ready for transfer to the user community. In addition to environmental monitoring, operational applications for the CIMS instruments include battlefield chemical weapon detection on remotely powered vehicles, piloted aircraft, or ground vehicles; covert intelligence gathering using mobile ground or air instrumentation; site inspection for treaty verification; fenceline monitoring for chemical cloud approach; security screening for explosive devices; air toxics emissions measurements; drug detection and interdiction; buried mine detection; and various medical applications.