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Abstract:
In this paper, we present the design, development,
and characteristics of the novel aerosol mass spectrome-
ter ERICA (ERC Instrument for Chemical composition of
Aerosols; ERC – European Research Council) and selected
results from the first airborne field deployment. The instru-
ment combines two well-established methods of real-time
in situ measurements of fine particle chemical composition.
The first method is the laser desorption and ionization tech-
nique, or laser ablation technique, for single-particle mass
spectrometry (here with a frequency-quadrupled Nd:YAG
laser at λ = 266 nm). The second method is a combination
of thermal particle desorption, also called flash vaporization,
and electron impact ionization (like the Aerodyne aerosol
mass spectrometer). The same aerosol sample flow is ana-
lyzed using both methods simultaneously, each using time-
of-flight mass spectrometry. By means of the laser ablation,
single particles are qualitatively analyzed (including the re-
fractory components), while the flash vaporization and elec-
tron impact ionization technique provides quantitative infor-
mation 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. 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 and 3170 nm
(d50 cutoff). The chemical characterization of single parti-
cles is achieved by recording cations and anions with a bipo-
lar time-of-flight mass spectrometer. For the measurement of
non-refractory components, the particle size range extends
from approximately 120 to 3500 nm (d50 cutoff; dva), and
the cations are detected with a time-of-flight mass spectrom-
eter. The compact dimensions of the instrument are such that
the ERICA can be deployed on aircraft, at ground stations, or
in mobile laboratories. To characterize the focused detection
lasers, the ablation laser, and the particle beam, comprehen-
sive laboratory experiments were conducted. During its first
deployments the instrument was fully automated and oper-
ated during 11 research flights on the Russian high-altitude
research aircraft M-55 Geophysica from ground pressure and
temperature to 20 km altitude at 55 hPa and ambient temper-
atures as low as −86 ◦C. In this paper, we show that the ER-
ICA is capable of measuring reliably under such conditions.
