ACOM CIMS real-time data collection   ACOM CIMS installed on aircraft   ACOM CIMS mounted in flight rack

Overview

The ACOM CIMS group, led by Dr. Brett B. Palm, measures reactive trace gases in the atmosphere with a focus on understanding atmospheric oxidation processes. When used with the typical iodide reagent ions (i.e., I-CIMS), the instrument is simultaneously sensitive to potentially hundreds of different species including a broad suite of oxidized organics, halogens, nitrogen-containing species, and sulfur oxidation products. ACOM CIMS measurements are critical for researching topics such as emission sources, oxidant sources and cycles, and the formation and fate of airborne pollutants. Measurements of organic oxidation products provide cutting-edge insights into how atmospheric aging leads to secondary pollutant formation including ozone and aerosols. These measurements also help to understand how atmospheric chemistry feeds back to influence weather and climate.

Instrument Description

The ACOM CIMS instrument couples state-of-the-art chemical ionization techniques with a customized time-of-flight mass spectrometer (TOFWERK). It is typically operated with iodide reagent ions in a VOCUS AIM reactor, but with additional development can be adapted to other state-of-the-art techniques. The instrument uses custom software and hardware, including water vapor, flow rate, pressure, and temperature controls, to provide world class quality and reliability that build upon years of experience in operating and deploying related instruments on aircraft platforms in collaboration with the research community. The time-of-flight detector samples typically at 1 Hz and as fast as 10 Hz, making it an extremely powerful and versatile technique that is particularly suited for airborne measurements where the atmospheric composition can change rapidly in space and time. The ACOM CIMS can be deployed in-cabin on aircraft such as the NSF NCAR C-130, and it also uses a custom one-of-a-kind mass spectrometer with a unique geometry that is under development to be deployed inside a wing pod under the GV aircraft wing. 

Measurement Campaigns

The ACOM CIMS was developed in 2025, in preparation for its first measurements as part of the GOTHAAM campaign.

Lead Contact

Brett Palm, bbpalm@ucar.edu

Citation

When referencing the ACOM CIMS or its data in publications or proposals, please use the identifier 10.xxxx/xxxxxxx -- for example as a citation:

NSF NCAR Atmospheric Chemistry Observations and Modeling Laboratory. (2026). ACOM Chemical Ionization Mass Spectrometer (ACOM CIMS). NSF NCAR Atmospheric Chemistry Observations and Modeling Laboratory. https://doi.org/10.xxxx/xxxxxx