A partial story of an aircraft-based laminar gas sampling inlet

Da Yang,
Volkamer group

"Aircraft-based measurements allow for large spatial-scale characterization of atmospheric aerosol and gas, but these measurements, under high-speed flow conditions, complicate efforts to maintain sample integrity through the inlet transport process. Of particular concern is the role of turbulence in driving loss of gas-phase species and aerosol particles. While a significant amount of research has gone into understanding aerosol sampling efficiency for aircraft inlets, a similar research investment has not been made for gas sampling. To study the gas sampling loss, computational simulations and wind tunnel experiments were used to analyze the gas sampling performance of a laminar gas inlet developed and used in the Ti³GER project. The measurements of was conducted in a high-speed wind tunnel. The gas transmission efficiency of through different sampling lines was measured using CIMS, and the experimental results are being compared to simulations of flow and mass diffusion modelling in the sampling line. Both experimental data and simulation results show the gas transmission efficiency increases with an increased sampling flow rate, including turbulent flow. In this presentation, I will give a short introduction to my work on studying aircraft-based sampling systems and focus on sharing the information I learned from gas-phase measurement results."

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Characterisation of Br-CIMS response under different humidity level and its application in CLOUD 16

Yandong Tong,
Volkamer group

"Chemical ionisation mass spectrometry (CIMS) exhibits high sensitivity and versatility in gaseous species, therefore, it has been widely used in atmospheric chemistry studies, especially in new particle formation and secondary organic aerosol formation studies. Among the different ionisation methods, CIMS using bromide (Br-) as reagent ion has been recently developed, optimised, and characterised, which is suitable to detect various organic and inorganic species, e.g., iodine and its oxidation products. However, Br-CIMS shows humidity dependence in many studies. In this study, we developed a new water regulation system for our CIMS and implemented it in laboratory experiments and in the CLOUD 16 campaign at CERN in Geneva, Switzerland. By taking advantage of the water regulation system and CLOUD chamber facility, we explored the Br- CIMS sensitivity to different species in a wide range of humidity levels. For strongly bonded species, e.g., iodine (I 2 ), Br-CIMS sensitivity to these species increases as the humidity level increases, whereas Br-CIMS sensitivity to weakly bonded species, e.g., glyoxal (CHOCHO), exhibits the opposite trend. A decent understanding of Br-CIMS response to different species under various humidity conditions allows us to provide valuable measurements in CLOUD 16, especially helping us understand the role of CHOCHO in nucleation events."