Design, characterization, and first field deployment of a novel aircraft-based aerosol mass spectrometer combining the laser ablation and flash vaporization techniques

Abstract

Abstract. In this paper, we present the design, development, and characteristics of the novel aerosol mass spectrometer ERICA (ERC Instrument for Chemical composition of Aerosols) and selected results from the first aircraft-borne field deployment. The instrument combines two well-established methods of real-time in-situ measurements of fine particle chemical composition. The first method is the single particle laser ablation technique (here with a frequency-quadrupled Nd:YAG laser at λ = 266 nm). The other method is a combination of flash vaporization and electron impact ionization (like the Aerodyne aerosol mass spectrometer). The aerosol sample can be analyzed with both methods, each using time-of-flight mass spectrometry. By means of the laser ablation, single particles are qualitatively analyzed (including the refractory components) while the flash vaporization and electron impact ionization technique provides quantitative information on the non-refractory components (i.e., particulate sulfate, nitrate, ammonia, organics, and chloride) of small particle ensembles. These techniques are implemented in two consecutive instrument stages within a common sample inlet and a common vacuum chamber. At its front end, the sample air containing the aerosol particles is continuously injected via an aerodynamic lens (ADL). All particles which are not ablated by the Nd:YAG laser in the first instrument stage continue their flight until they reach the second instrument stage and impact on the vaporizer surface (operated at 600 °C). The ERICA is capable of detecting single particles with vacuum aerodynamic diameters (dva) between ~ 180 nm and 3170 nm (d50 cut-off). The chemical characterization of single particles is achieved by recording cations and anions with a bipolar time-of-flight mass spectrometer (B-ToF-MS). For the measurement of non-refractory components, the particle size range extends from approximately 120 nm to 3.5 µm (d50 cut-off; dva), and the cations are detected with a C-ToF-MS (compact time-of-flight mass spectrometer). The compact dimensions of the instrument are such that the ERICA can be deployed on aircraft, ground stations, or mobile laboratories . During its first deployments the instrument operated fully automated during 11 research flights on the Russian high-altitude research aircraft M-55 Geophysica from ground pressure and temperature up to 20 km altitude at 55 hPa and ambient temperatures as low as −86 °C.

Chemical analysis of the Asian Tropopause Aerosol Layer (ATAL) with emphasis on secondary aerosol particles using aircraft based in situ aerosol mass spectrometry

“…The particle size range detectable by the ERICA-AMS is given by the transmission efficiency of the aerodynamic lens (vacuum aerodynamic diameter of the particles between 110 nm and 3.5 µm, Xu et al (2017)). Although Hünig et al (2021) indicates an even lower cutoff of less than 90 nm, the smallest particles will not significantly contribute to the mass concentrations measured by the ERICA-AMS during StratoClim. The lower cutoff diameter of the LDI unit is limited by the optical particle detection efficiency to 180 nm.…”

“…CC BY 4.0 License. (Hünig et al, 2021;Dragoneas et al, 2022). The two commonly adopted methods for in situ real-time mass spectrometric analysis of aerosol particles are (1) laser desorption ionization (LDI) of particles followed by time-of-flight mass spectrometry (Suess and Prather, 1999), and (2) thermal desorption with subsequent electron impact ionization (TDI) as implemented in the Aerodyne AMS (Drewnick et al, 2005;Canagaratna et al, 2007).…”

“…The ERICA combines these two techniques in a single, fully automatically operating apparatus. The instrument has been described in detail by Hünig et al (2021) and Dragoneas et al (2022) and is only briefly reviewed here: Ambient sample air is supplied to the ERICA by a specially designed shrouded inlet (Dragoneas et al, 2022), which consists of a two-staged diffusor that reduces the required sampling line velocity for isokinetic sampling by a total factor of 39. The principal design is based on the aerosol inlet used in the IAGOS-CARIBIC project (Brenninkmeijer et al, 2007) and for the ERICA the inlet design and its performance has been simulated by computational flow dynamics.…”

“…The ERICA-LAMS (ERICA laser ablation mass spectrometer) unit implements the LDI technique. Two continuous wave lasers detect and classify the individual particles by size and are used to trigger a pulsed UV desorption/ionization laser (Hünig et al, 2021), similar to, e.g. the ALABAMA (Brands et al, 2011) or the PALMS (Murphy, 2007) instruments.…”

“…the ALABAMA (Brands et al, 2011) or the PALMS (Murphy, 2007) instruments. The vacuum aerodynamic diameter of the particles (d va ) is derived from the particle velocity by applying a calibration with particles of known diameter, density, and shape (here, monodisperse polystyrene latex particles in a diameter range between 80 nm and 5.1 µm (Hünig et al, 2021)). The ions generated by the UV laser pulse (~4 mJ at a wavelength of 266 nm) are extracted by switched electrical fields to generate positive and negative ion mass spectra for each desorbed aerosol particle.…”