Abstract.We have designed and characterized a new inlet and aerodynamic lens for the Aerodyne aerosol mass spectrometer (AMS) that transmits particles between 80 nm and more than 3 µm in vacuum aerodynamic diameter. The design of the inlet and lens was optimized with computational fluid dynamics (CFD) modeling of particle trajectories. Major changes include a redesigned critical orifice holder and valve assembly, addition of a relaxation chamber behind the critical orifice, and a higher lens operating pressure. The transmission efficiency of the new inlet and lens was characterized experimentally with size-selected particles. Experimental measurements are in good agreement with the calculated transmission efficiency.

The aerodynamic lens system of the Aerodyne Aerosol Mass Spectrometer (AMS) was analyzed using the Aerodynamic Lens Calculator. Using this tool, key loss mechanisms were identified, and a new lens design that can extend the transmission of particulate matter up to 2.5 mm in diameter (PM2.5) was proposed. The new lens was fabricated and experimentally characterized. Test results indicate that this modification to the AMS lens can significantly improve the transmission of large sized particles, successfully achieving a high transmission efficiency up to PM2.5 range. EDITORPaul Ziemann

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We report an experimental comparison of the rotational temperature and the gas kinetic temperature of and in a positive column discharge. The discharge is operated in an oven. The oven temperature, determined with a thermocouple, provides a lower bound for the gas kinetic temperature. An upper bound on the temperature is obtained by adding to the oven temperature a calculated increase in the gas temperature due to the discharge. The contribution of the discharge to the gas temperature is calculated under the assumption of complete conversion of input power into gas heating so that the estimate provides an upper bound. The rotational temperature of is determined directly with a Boltzmann plot of the first negative system. For , the ratio of the first minimum to the secondary maximum for the band profile of the second positive system is used to obtain the rotational temperature. We compare experimental spectra with simulated spectra generated under the assumption that the rotational temperature is equal to the minimum and maximum gas kinetic temperatures. The reliability of the rotational temperature as a gas temperature diagnostic under our experimental conditions is discussed for all bands investigated.

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