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| Titel |
Performance of diethylene glycol-based particle counters in the sub-3 nm size range |
| VerfasserIn |
D. Wimmer, K. Lehtipalo, A. Franchin, J. Kangasluoma, F. Kreissl, A. Kürten, A. Kupc, A. Metzger, J. Mikkilä, T. Petäjä, F. Riccobono, J. Vanhanen, M. Kulmala  , J. Curtius |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 6, no. 7 ; Nr. 6, no. 7 (2013-07-29), S.1793-1804 |
| Datensatznummer |
250017927
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| Publikation (Nr.) |
 copernicus.org/amt-6-1793-2013.pdf |
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| Zusammenfassung |
When studying new particle formation, the uncertainty in determining
the "true" nucleation rate is considerably reduced when using
condensation particle counters (CPCs) capable of measuring
concentrations of aerosol particles at sizes close to or even at the
critical cluster size (1–2 nm). Recently, CPCs able to
reliably detect particles below 2 nm in size and even close to
1 nm became available. Using these instruments, the corrections
needed for calculating nucleation rates are substantially reduced compared to scaling the
observed formation rate to the nucleation rate at the critical cluster
size. However, this improved instrumentation requires a careful
characterization of their cut-off size and the shape of the detection
efficiency curve because relatively small shifts in the cut-off size
can translate into larger relative errors when measuring particles
close to the cut-off size.
Here we describe the development of two continuous-flow CPCs using
diethylene glycol (DEG) as the working fluid. The design is based on
two TSI 3776 counters. Several sets of measurements to characterize
their performance at different temperature settings were carried
out. Furthermore, two mixing-type particle size magnifiers (PSM) A09
from Airmodus were characterized in parallel. One PSM was operated at
the highest mixing ratio (1 L min−1 saturator flow), and the
other was operated in a scanning mode, where the mixing ratios are
changed periodically, resulting in a range of cut-off sizes. The mixing
ratios are determined by varying the saturator flow, where the aerosol flow
stays constant at 2.5 L min−1. Different test aerosols were generated
using a nano-differential mobility analyser (nano-DMA) or a high-resolution DMA,
to obtain detection efficiency curves for all four CPCs. One calibration setup included
a high-resolution mass spectrometer (APi-TOF) for the determination of
the chemical composition of the generated clusters. The lowest cut-off
sizes were achieved with negatively charged ammonium sulfate
clusters, resulting in cut-offs of 1.4 nm for the laminar flow
CPCs and 1.2 and 1.1 nm for the PSMs. A comparison of one of
the laminar-flow CPCs and one of the PSMs measuring ambient and
laboratory air showed good agreement between the instruments. |
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