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Atmos. Meas. Tech., 13, 5993–6006, 2020
https://doi.org/10.5194/amt-13-5993-2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
Characterization of a non-thermal plasma source for use as a mass
specrometric calibration tool and non-radioactive aerosol charger
Christian Tauber1, David Schmoll1, Johannes Gruenwald2, Sophia Brilke1, Peter Josef Wlasits1,
Paul Martin Winkler1, and Daniela Wimmer1
1Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria
2Gruenwald Laboratories GmbH, Taxberg 50, 5660 Taxenbach, Austria
Correspondence: Christian Tauber (christian.tauber@univie.ac.at)
Received: 21 February 2020 – Discussion started: 8 April 2020
Revised: 3 September 2020 – Accepted: 16 September 2020 – Published: 11 November 2020
Abstract. In this study the charging efficiency of a radioac-
tive and a non-radioactive plasma bipolar diffusion charger
(Gilbert Mark I plasma charger) for sub-12 nm particles has
been investigated at various aerosol flow rates. The results
were compared to classic theoretical approaches. In addi-
tion, the chemical composition and electrical mobilities of
the charger ions have been examined using an atmospheric
pressure interface time-of-flight mass spectrometer (APi-
TOF MS). A comparison of the different neutralization meth-
ods revealed an increased charging efficiency for negatively
charged particles using the non-radioactive plasma charger
with nitrogen as the working gas compared to a radioac-
tive americium bipolar diffusion charger. The mobility and
mass spectrometric measurements show that the generated
bipolar diffusion charger ions are of the same mobilities
and composition independent of the examined bipolar dif-
fusion charger. It was the first time that the Gilbert Mark I
plasma charger was characterized in comparison to a com-
mercial TSI X-Ray (TSI Inc, Model 3088) and a radioactive
americium bipolar diffusion charger. We observed that the
plasma charger with nitrogen as the working gas can enhance
the charging probability for sub-10 nm particles compared to
a radioactive americium bipolar diffusion charger. As a re-
sult, the widely used classical charging theory disagrees for
the plasma charger and for the radioactive chargers with in-
creased aerosol flow rates. Consequently, in-depth measure-
ments of the charging distribution are necessary for accurate
measurements with differential or scanning particle sizers for
laboratory and field applications.
1 Introduction
Particle properties are influenced by the presence of elec-
trostatic charges, e.g. the deposition of particles in human
airways, their collection in a filter and the characterization
of size distributions based on the mobility equivalent diam-
eter (Johnson et al., 2020). Consequently, any uncertainty in
the charge distribution of aerosol particles propagates into
the total measurement uncertainty of electrostatic classifiers
(Leppä et al., 2017). The probability that a particle carries
one or more charges varies widely over the 1nm to 1µm size
domain; hence, it is crucial to know this probability in or-
der to infer the particle size distribution from the numbers
of charged particles that are transmitted through the mobility
classifier (Leppä et al., 2017).
Bipolar diffusion charging and neutralization is typically
done by ionizing radiation, which exposes aerosol particles
to high concentrations of positive and negative ions in the
carrier gas (Jiang et al., 2014). Subsequent diffusion of the
ions brings the aerosol to a stationary-state charge distri-
bution independent of their initial charge state (Cooper and
Reist, 1973; Liu and Pui, 1974; Adachi et al., 1985; Reischl
et al., 1996). If a high ion concentration and residence time
are reached, a charge equilibrium inside the charger leads
to a well-known size-dependent charging probability (Fuchs
et al., 1965). This stationary-state charge distribution is of
importance for the use of differential or scanning mobility
particle spectrometers, which rely on accurate knowledge of
the size-dependent charge fractions (Wang and Flagan, 1990;
Jiang et al., 2014).
Published by Copernicus Publications on behalf of the European Geosciences Union.
5994 C. Tauber et al.: Characterization of a non-thermal plasma charger
Aerosol particles below 10 nm in diameter are typically
difficult to charge and carry only one electrical charge at
maximum (Wiedensohler, 1988). Quantitative particle detec-
tion in this size range is extremely challenging due to high
diffusional losses, which results in low number concentra-
tions. Therefore, a higher charging efficiency is of impor-
tance to increase the detectable number concentration in the
sub-10 nm regime.
The charging of small particles has also become a field
of major interest in plasma physics. A vast number of stud-
ies about accumulating an electrical charge on dust particles
have been published over the last years. Usually grain sizes
ranging from some nanometres (nm) to several micrometres
(µm) are considered in the experiments and theoretical mod-
els. Most of these works were focused on generating plas-
mas for industrial or space applications (Michau et al., 2016;
Deka et al., 2017; Kopnin et al., 2018; Yaroshenko et al.,
2018; Intra and Yawootti, 2019). However, one of the most
recent developments is the application of plasma in aerosol-
related topics, such as plasma treatment of aerosol particles
(Uner and Thimsen, 2017), and, as a novel topic, charging
of aerosol particles or ionization of trace gas compounds
(Spencer et al., 2015; Yang et al., 2016; Intra and Yawootti,
2019). Usually, corona-type discharges are used for charging
purposes in aerosol physics due to their capability of creating
high charge densities even at atmospheric pressure. Further-
more, their reproducibility is very high, and they are easy
to construct and maintain. Low-temperature plasma ioniza-
tion is known to cause little fragmentation and exhibits a
low temperature increase to the surroundings (Harper et al.,
2008). The non-thermal plasma in this work is produced by
a high-frequency generator which is separated by a dielectric
barrier to the ground potential (Gruenwald et al., 2015). The
term “non-thermal plasma” is usually used to describe a dis-
charge in which the electrons are in thermal non-equilibrium
with the ions. This means that the average temperature of the
gas in such a discharge is far lower than the temperature of
a thermal plasma (i.e. some hundred kelvin (K) compared
to several thousand kelvin in the latter case). The discharge
characteristics can be varied by changing the working gas
of the Gilbert Mark I plasma charger (Gruenwald Labora-
tories GmbH). Plasma discharges in general are on–off de-
vices that combine the simple handling of an X-ray charger
with the achievable high ion density of a radioactive ameri-
cium charger and even higher. Thus, an atmospheric plasma
source is a well-suited device for the ionization process prior
to particle number size distribution measurements and mass
spectrometric measurements.
In the past, various studies have characterized the charg-
ing probabilities and mobility spectra of the ions gener-
ated by AC-corona-, X-Ray- or alpha-radiation-based charg-
ers (Wiedensohler et al., 1986; Steiner and Reischl, 2012;
Kallinger et al., 2012; Kallinger and Szymanski, 2015).
These works revealed deviations in the charge distribution to
classical theory, which result in an increased total measure-
ment error (Johnson et al., 2020).
In this work, we investigated the charging distribution for
three different aerosol neutralizer types to reduce the uncer-
tainty under various flow conditions and working gases in
the case of the Gilbert Mark I plasma charger. In addition,
the chemical composition of charger ions of both polarities
has been investigated and compared. Furthermore, the opti-
cal emission spectra and ozone concentration were measured
for the Gilbert Mark I plasma charger.
2 Experimental setup
Here we report on size-dependent charging probability mea-
surements of a non-thermal plasma source (Gilbert Mark I
plasma charger, Gruenwald Laboratories GmbH, Austria), of
an americium 241 (241Am) aerosol neutralizer and of a TSI
Advanced Aerosol Neutralizer 3088 by means of a tandem
DMA (Differential Mobility Analyzer) setup as depicted in
Fig. 1. Thereby, the charging efficiency of a standard TSI X-
Ray neutralizer and an 241Am aerosol neutralizer could be
compared to the plasma source. The atmospheric pressure
plasma charger consists of a gas flow that is shielded by an-
other gas flow from the surrounding atmosphere. The plasma
is ignited inside the inner flow while the aerosol is adminis-
tered through the outer gas stream. The main source of the
plasma is a high-frequency copper electrode that is situated
on the central axis of those two gas streams.
According to Kallinger et al. (2012), the radioactive
241Am charger used has a cylindrical geometry with an axial
flow direction. The radioactive source is mounted on the in-
ner wall. The chamber has an inner diameter of about 30 mm
and a length of 120 mm. Furthermore, the soft X-ray charger
is composed of a stainless-steel tube and a photo ionizer. The
aerosol particles are directed along the tube towards the soft
X-ray source and leave the charger via an outlet, that is ori-
ented perpendicularly to the axis of the tube. The tube has an
inner diameter of 30 mm and a length of 200 mm.
The charging efficiency measurements were performed
with sodium chloride and silver nanoparticles at various par-
ticle sizes and aerosol flow rates. The nanoparticles were
generated with a tube furnace (Carbolite Gero GmbH & Co.
KG, Germany) while synthetic air as well as dried and fil-
tered compressed air were used as the carrier gas. An ad-
ditional dilution flow allowed for controlling the particle
concentration of the generated aerosol flow. Downstream of
the aerosol generator the nanoparticles were charged with
a TSI Advanced Aerosol Neutralizer 3088 and led to an
nDMA which was operated as a classifier. A second TSI Ad-
vanced Aerosol Neutralizer 3088 neutralized the monodis-
perse aerosol particles after the nDMA. The geometric stan-
dard deviation of the particle size for the nDMAs used was
evaluated by Winkler et al. (2008) for a sheath flow of
25 L/Min and an aerosol flow of 4.6 L/Min and is below
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C. Tauber et al.: Characterization of a non-thermal plasma charger 5995
Table 1. Flow rates for the aerosol and sheath flow for the nDMAs
used with the calculated sheath flow ratio.
Aerosol Sheath
nDMA flow (L/Min) flow (L/Min) Ratio
1 3.0 19.5 6.5
2 2.5 19.5 7.8
2 5.0 33.0 6.6
2 8.0 41.0 5.1
1.05 for particles with a mobility diameter down to 2 nm.
The resulting flow ratio (sheath/aerosol =5.4) is close to our
measurement with 8 L/Min aerosol flow, and the signal-to-
noise ratio was comparable to the measurements with lower
aerosol flow rates. The different flow settings for the nDMAs
are listed in Table 1.
To ensure that no charged particles remain in the aerosol
flow, an ion trap was installed after the bipolar diffusion
charger (Brilke et al., 2020). After the ion trap the aerosol
flow was split in a way that 1.5 L/Min was led to a CPC (TSI
3776 UCPC) which recorded the particle concentration at
this point, while the remaining aerosol flow was fed into the
bipolar diffusion charger under investigation. A dilution flow
of synthetic air as well as compressed air allows for vary-
ing the flow rate before the aerosol flow gets to the bipolar
diffusion charger. The investigated bipolar diffusion charg-
ers were switched in intervals of 10 min during the measure-
ments to ensure that the different devices were operated at
comparable conditions. Afterwards the charged aerosol flow
was led to a second nDMA, which was operated in scanning
mode. A second CPC (TSI 3776 UCPC) recorded the par-
ticle concentration at this point of the setup. In addition to
the switching of the different bipolar diffusion chargers, the
working gas as well as the working gas flow of the atmo-
spheric pressure plasma source were varied.
Complementary to the charging efficiency, the chemical
composition of the charger ions was investigated by cou-
pling the plasma torch with an APi-TOF MS (atmospheric
pressure interface time-of-flight mass spectrometer; Junni-
nen et al. (2010); Leiminger et al. (2019); see upper panel in
Fig. 2) to analyze the chemical composition of the ions gener-
ated in positive and negative ion mode. Mobility spectra were
recorded with a custom-built Faraday cup electrometer (FCE;
Winklmayr et al., 1991) with an improved response time of
0.1 s. By recording the ion spectrum with a Vienna-type high-
resolution mobility analyzer (UDMA-1; Steiner et al., 2010),
the mobility equivalent diameter of the generated clusters
could be analyzed (see lower panel in Fig. 2). Compressed
filtered and dry air was used as the carrier gas, and the rel-
ative humidity (RH) was monitored using SHT75 RH sen-
sors with an accuracy of ±1.8% and was kept below 2 %.
However, we cannot exclude the possibility that in the closed
loop sheath flow system of the UDMA-1 small amounts of
water vapour remain. The calibration of the ioniAPi-TOF
mass axis was performed using a bipolar electrospray source
for the generation of tetraheptyl ammonium bromide clusters
(Fernández de la Mora and Barrios-Collado, 2017; Brilke
et al., 2020). The UDMA-1 resolution power is 15 at the
size of the THABr monomer, i.e. 1.45 nm mobility equiva-
lent diameter (Flagan, 1999; Steiner et al., 2010). Due to the
high ion concentration of a non-thermal plasma source, a vast
number of reactive species are created, especially when the
plasma is ignited in air (Kurake et al., 2016). Most of these
species will be ozone or nitrogen oxides because of the air’s
chemical composition. Hence, the optical emission spectra
of the non-thermal plasma source were recorded, which is a
non-invasive diagnostic technique that allows insights to be
gained into the composition of the plasma and the production
of harmful gases like ozone and nitrogen oxides. The opti-
cal emission spectrometer was located at the nozzle of the
plasma charger and used to record spatially averaged optical
data along the axis of the plasma source.
3 Results and discussion
3.1 Optical emission spectroscopy
Optical emission spectroscopy (OES) was used to determine
the ionization stages of the ions or molecules in the plasma.
The measurements were performed with the HR2000+ES
spectrometer from Ocean Optics. The light emission from
the atmospheric pressure plasma source was collected with
a 440 µm fibre with a length of 2 m. The wavelength range
of the spectrometer was between 200 and 1100 nm. Prior
to the data acquisition, the torch was switched on for about
30 s until no fluctuations in the spectra were visible. Each
spectrum is the result of averaging over 50 scans to re-
move fluctuations. The plasma source itself was driven with
a high frequent alternate current of 15 kHz with 825 V peak-
to-peak voltage. The plasma was ignited in helium of high
purity (ALPHAGAZ 1 HELIUM, >=99.999 % (5.0), Air
Liquide), which was fed into the plasma jet with a flow
rate of 180 mL/min. The plasma is ignited inside the inner
flow, while the aerosol is administered through the outer gas
stream. The main source of the plasma is a high-frequency
copper antenna or electrode that is situated on the central axis
of those two gas streams. The results for a typical OES spec-
trum for the described experimental conditions are depicted
in Fig. 3.
The most prominent emission lines were identified to be
excited neutral helium (He I) and singly ionized copper
(Cu II). The central wavelengths of the identified lines are
listed in Table 2.
It can be concluded from the OES spectra that there is no
ionization of aerosol particles facilitated by the carrier gas,
since only neutral helium emission lines have been recorded.
On the other hand, atoms from the copper high-frequency
https://doi.org/10.5194/amt-13-5993-2020 Atmos. Meas. Tech., 13, 5993–6006, 2020
5996 C. Tauber et al.: Characterization of a non-thermal plasma charger
Figure 1. Schematic of the experimental setup for the charging probability and particle size conservation measurements. The additional
working gas flow is only needed for the plasma charger. See text for explanation.
Figure 2. Schematic of the calibration setup for the plasma torch using an UDMA. The black rhombus marks the working gas supply. Mass
spectra of negative and positive ions were measured simultaneously using the ioniAPi-TOF in negative and positive ion mode at a flow rate of
10 L/min through the plasma torch (upper panel) for the three working gases and operational settings. The mobility spectra of the generated
positive and negative ions were measured using the UDMA-1 (Steiner et al., 2010) coupled to a fast-response FCE at a 5 L/min flow rate.
antenna enter the plasma zone and are then ionized through
electron impacts. The charged particles created from these
processes (i.e. ions and secondary electrons), in turn, charge
the aerosol particles in the gas stream. This can be explained
by the large difference in ionization energies between copper
(7.7 eV) and helium (24.6 eV). Since the electrons in non-
thermal atmospheric pressure discharges have normally en-
ergies of just a few eV, the ionization of copper atoms is far
more likely than of helium particles.
3.2 Charger ion chemical composition
The ion properties of ionic molecular clusters produced in the
plasma torch were investigated by means of electrical mobil-
ity and mass spectrometry. Mobility spectra and mass spectra
were recorded for positive and negative ions and compared
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C. Tauber et al.: Characterization of a non-thermal plasma charger 5997
Figure 3. Typical OES spectrum in a helium plasma averaged over
50 scans. Experimental conditions: 15 kHz driving frequency, 825 V
peak-to-peak voltage and a 180 mL/Min He flow.
Table 2. Measured central wavelengths compared to data from
Kramida et al. (2013) and the associated particle species for the
most prominent emission lines in Fig. 3.
Wavelength from
Measured central Kramida et Particle
wavelength (nm) al. (2013) (nm) species
334.38 334.4 Cu II
354.86 354.9 Cu II
388.86 388.9 He I
425.67 425.6 Cu II
706.05 706.5 He I
755.56 775.4 Cu II
to the resulting spectra from ions produced in the 241Am
charger. Figure 4 shows the mass spectra for negative (left)
and positive (right) ions generated by the 241Am charger (first
panel) and the plasma torch for the three different working
gases (second to fourth panel) using the setups shown in
Fig. 2 at the working gas flow settings presented in Tables S1
and S2 in the Supplement. The negative mass spectra were
normalized to the nitrate ion (NO−
3) peak at an integer mass
of 62 Th and the positive mass spectra to the (H2O)2·H3O+
water cluster at an integer mass of 55 Th. The negative mass
spectra are dominated by the nitrate ion, NO−
3, and its dimer,
trimer and water cluster (see labels in second panel in Fig. 4).
The three spectra for charger ions produced from the torch
exhibit the same major peaks, with the nitrate ion trimer peak
being highest when He is used as the working gas (see fourth
panel). This observation may be a result of the different op-
erational settings of the plasma torch when He is used as the
working gas (see Tables S1 and S2). The negative ion spec-
trum of the 241Am charger reveals the same major peaks as
the plasma torch negative mass spectra. Similar results have
been found by a study investigating the chemical composi-
tion of ions produced by a corona discharge (Manninen et al.,
2011). The identified major peaks of the positive mass spec-
tra are listed in Table 3. In the lower mass range between
40 and 80 Th, protonated water, H3O+, and water clusters
thereof dominate the spectrum for the 241Am charger and the
three spectra of the plasma torch. The elemental composition
of four major peaks in the positive spectra of the plasma torch
at integer masses of 88, 175, 187 and 201 Th was identified
as that of carbonaceous compounds. In the higher mass range
between 600 and 1000 Th, a set of major peaks was identi-
fied as silicone compounds. The same peaks were identified
in the positive mass spectra of ions produced from the 241Am
charger (solid black box in Fig. 4). This observation was also
made by Manninen et al. (2011), who explained these peaks
as being a result of contamination from silicone tubing. Sili-
cone tubing is oftentimes used in aerosol measurements and
can cause artifacts because of degassing of siloxanes (As-
bach et al., 2016). However, a range of peaks in the mass
window from approximately 200 to 500 Th remains uniden-
tified (dashed black box). These carbonaceous compounds
have a positive mass defect and likely arise from ionization
of constituents in the pressurized air that was used as the car-
rier gas.
The chemical composition of the plasma-generated ions
was found to be independent of the choice of the working
gas as shown in Fig. 4. Also, the averaged electrical mobility
measurements (averaged over 10 scans) conducted with the
experimental setup depicted in Fig. 2 (lower panel) revealed
identical peaks. The mobility spectra for the plasma torch us-
ing N2, He and air as the working gas and the 241Am charger
are presented in Fig. 5. Similar results for different bipolar
charging devices have been found by Kallinger et al. (2012)
and Steiner and Reischl (2012). The latter analyzed the ef-
fects of carrier gas contaminants on the charging probability
which influences the electrical mobility spectrum. One of the
analyzed TSI X-Ray chargers showed a different mobility
spectrum compared to the other analyzed bipolar diffusion
chargers. According to our mass spectrometric analysis, this
is due to ammonium sulfate contaminations from previous
experiments.
3.3 Charging probability
The bipolar diffusion chargers were tested in the setup shown
in Fig. 1, in order to characterize the charging performance
of the plasma torch (Gilbert Mark I plasma charger) and the
241Am as well as the soft X-Ray charger. The tandem DMA
setup enabled us to charge a monodisperse aerosol and ro-
tate the different bipolar diffusion chargers, which permits
a direct comparison of the charging performance of the dif-
ferent devices. Two butanol-based CPCs (TSI 3776 UCPC)
with reduced temperature settings (condenser 1.1 ◦C, satura-
tor 30.1 ◦C, optics 31.1◦C) compared to factory settings to
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5998 C. Tauber et al.: Characterization of a non-thermal plasma charger
Figure 4. Negative (left) and positive (right) mass spectra of ions generated by the 241Am charger (first panel) and the plasma source for
three different working gases, synthetic air (second panel), N2(third panel) and He (fourth panel) were measured using the setup in the upper
panel of Figure 2. The mass spectra were averaged over 1h each. The identified compounds are labelled in the second panel and are presented
in Table 3. The negative mass spectrum was normalized to the NO−
3ion (integer mass 62 Th); the positive mass spectrum was normalized to
the (H2O)2·H3O+cluster (integer mass 55 Th). The H3O+ion is not displayed here since it was not covered by the set mass range of the
ioniAPi-TOF. The dashed square box marks unidentified masses in the positive 241Am mass spectrum, and the solid square box shows the
silicone compounds that are listed in Table 3.
increase the particle counting efficiency were used (Barm-
pounis et al., 2018; Tauber et al., 2019a). The particle num-
ber concentration was recorded before (CPC1; see Fig. 1)
and after charging (CPC2) by the tested charger (charger 2).
The charging efficiency was inferred from the ratio of the
two CPCs (CPC2 / CPC1) under consideration of the trans-
mission and diffusional particle losses in the lines and DMA.
In Tauber et al. (2019b) the particle counting efficiency of
the CPCs used here was determined, and the results obtained
were used to correct for the CPC detection efficiency. The
different bipolar diffusion chargers were tested with posi-
tively and negatively charged Ag and NaCl particles of dif-
ferent particle sizes in the sub-12 nm regime. In addition, the
plasma torch was operated with different working gases. The
additional flow rate from the working gas was at max 1/9 of
the aerosol flow. According to Thomas et al. (2018) a cut-
off drift to lower sizes for helium mole fractions below 0.67
was found for butanol-based CPCs. However, the CPC used
in this study was operated with reduced temperature settings,
and thereby a lower detection efficiency was established. As
a result, the recorded cut-off drift would therefore only in-
fluence the charging efficiency measurements conducted at
<3 nm. The resulting error is already covered for these par-
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C. Tauber et al.: Characterization of a non-thermal plasma charger 5999
Figure 5. Mobility distributions of the charger ions generated by the plasma torch using N2, He and air as the working gas and the 241Am
charger. The upper panel shows the mobility diameter distribution of the positive charger ions; the lower panel presents the mobility diameter
distribution of the negative charger ions.
Table 3. Overview of major negative and positive compounds in the mass spectra recorded using the ioniAPi-TOF in positive and negative
ion mode.
Negative ions Positive ions
Integer Molecular Integer Molecular
m/z (Th) formula m/z (Th) formula
46 NO−
232 O2+
62 NO−
337 H2O·H3O+
80 H2O·NO−
355 (H2O)2·H3O+
124 – 73 (H2O)3·H3O+
125 HNO3·NO−
388 C4H10NO+
187 – 175 C4H9NO ·C4H10NO+
188 (HNO3)2·NO−
3187 C10H21 NO+
2
201 C11H23 NO+
2
610 (SiOC2H6)8OH+
2
684 (SiOC2H6)9OH+
2
758 (SiOC2H6)10OH+
2
832 (SiOC2H6)11OH+
2
906 (SiOC2H6)12OH+
2
ticle sizes by the measurement uncertainties of the nDMA
and CPC.
The results of the charging efficiency when using the three
different working gases are displayed in Fig. 6. Theoretical
charging probabilities from Tigges et al. (2015) and Wieden-
sohler (1988) were added here.
Concerning negatively charged particles with a diameter
between 4 and 12 nm, the 241Am and the soft X-Ray charger
are in agreement with the theoretical curves, especially with
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6000 C. Tauber et al.: Characterization of a non-thermal plasma charger
Figure 6. Measured charging efficiencies for the different aerosol chargers for negatively and positively charged Ag particles (dots) and
negatively charged NaCl particles (squares) with mobility diameters less than 12nm.
Wiedensohler (1988). The plasma torch on the other hand
achieves higher charging efficiencies in this regime, with big
differences between the working gases used. With helium the
charging efficiencies were higher than the theoretical values;
especially for particle sizes bigger than 8 nm, a 25 % higher
charging efficiency was recorded. Ambient air yields even
higher charging probabilities but displays a significant de-
pendency on the particle type as the values for NaCl parti-
cles are about 25 % higher than for Ag particles. The highest
charging efficiencies for negatively charged particles were
achieved with nitrogen as the working gas. With nitrogen the
plasma torch achieved charging efficiencies that were up to
50 % higher than the common devices and showed no depen-
dency on the particle type. As the particle concentrations for
very small diameters between 2 and 4 nm are below 10 000
particles/ccm, the charging efficiencies of the different de-
vices vary strongly at these particle sizes. The nDMA in this
size range has a low transmission efficiency ranging from
20 % to 55 %, and therefore the signal at the CPC 2 is very
low. In addition, small temperature fluctuations in the tube
furnace lead to bigger uncertainties for the low total num-
ber concentration of the selected particle size. Especially for
NaCl particles, a big variation in the charging efficiencies of
the different charging devices was observed. These variations
almost certainly are caused by the low number concentra-
tions of NaCl particles at these sizes compared to Ag parti-
cles. However, except for NaCl particles at particle diameters
between 2 and 4 nm, the associated data points for the 241Am
bipolar diffusion charger agree well with the approximations
by Tigges et al. (2015) and Wiedensohler (1988).
The charging efficiencies of the plasma torch for posi-
tively charged particles strongly differ from those of nega-
tively charged particles. Again, the measured charging effi-
ciencies of the soft X-Ray charger match almost perfectly
with the theory for diameters between 4 and 12 nm. The
241Am charger also agrees with the theoretically predicted
values for diameters between 6 and 8 nm but shows asymme-
tries for larger particle sizes. The charging efficiency for pos-
itively charged particles decreases at larger sizes and results
in lower values compared to theory for the 241Am charger.
The charging efficiencies of the plasma torch strongly de-
pend on the type of working gas for positively charged par-
ticles. Evidently, the data using helium agree well with theo-
retical approximations from Tigges et al. (2015) and Wieden-
sohler (1988) in the size regime between 4 and 10 nm. For di-
ameters between 10 and 12 nm the charging efficiencies even
exceed the predicted values by about 50 %. The data suggest
no dependency of the charging efficiency on the charger ion
polarity when helium is used as the working gas in the plasma
torch. The data for compressed air match with the theoretical
curves for the whole size range and therefore behave simi-
larly to the soft X-Ray charger. As Fig. 6 clearly shows, this
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C. Tauber et al.: Characterization of a non-thermal plasma charger 6001
Table 4. Comparison of ion cluster properties: polarity, mobility diameter Dpcalculated from mean ion mobility Z, mean ion mass Mand
ion mobility ratio Z−/Z+.
Polarity Dp(nm) Z(cm2/Vs) M(Da) Z−/Z+
Reischl et al. (1996) +1.32 1.15 290 1.0 0.80
Reischl et al. (1996) −1.19 1.43 140 1.0 0.80
Measured +1.07 1.76 356 1.0 0.66
Measured −0.87 2.66 116 1.0 0.66
Figure 7. Measured charging efficiencies for the different aerosol chargers for negatively and positively charged Ag particles (dots) and
negatively charged NaCl particles (squares) with mobility diameters less than 12nm. The lines represent the charge distribution according to
Fuchs theory; the parameters for the ion mobilities, ion masses and ion mobility ratio are listed in Table 4. The collision probability of ions
was calculated following Hoppel and Frick (1986).
will change drastically if nitrogen is used as the working gas.
The charging efficiencies in positive polarity with nitrogen
are significantly lower (about 50 % compared to theory) than
with other chargers and other working gases in the whole size
regime.
Wiedensohler and Fissan (1991) have shown that the
predicted charging probabilities of NaCl and Ag particles
strongly depend on the carrier gas used and the ion mass
and mobility. During the ionization process positive ions and
free electrons are formed from molecules in the carrier gas
and ionized copper atoms. These primary ions attach to other
molecules, as for example H2O, CO2, oxygen and halogens,
and form bigger ion clusters that afterwards stick to the in-
vestigated particles. Wiedensohler and Fissan (1991) have
shown that the variation of the ion masses leads to differ-
ent theoretically predicted charging probabilities. For nitro-
gen as the carrier gas, they discovered a large dependency
of the charging probability on the ion masses. Similar asym-
metries are observed in our data when comparing the mea-
sured charging efficiencies of the plasma torch with nitrogen
as the working gas to the N2results of Wiedensohler and Fis-
san (1991). As Fig. 3 shows, the plasma torch forms copper
ions and free electrons which charge aerosol particles in the
carrier gas. The significantly different masses of these ions
may account for the differing charging efficiencies that are
accomplished with nitrogen for the negatively as well as for
the positively charged particles according to Wiedensohler
(1988).
As the working gas flow is exposed to a high-frequency
electrical field before it mixes with the aerosol flow, the
ions can form in a pure nitrogen environment. Hence the
charger ions form in a nitrogen atmosphere like in the case of
https://doi.org/10.5194/amt-13-5993-2020 Atmos. Meas. Tech., 13, 5993–6006, 2020
6002 C. Tauber et al.: Characterization of a non-thermal plasma charger
Wiedensohler and Fissan (1991), whereby silver and sodium
chloride particles were charged with a 85Kr source in a pure
nitrogen atmosphere. A similar but smaller effect was ob-
served in atmospheric air as the carrier gas. This mechanism
would also explain the better charging efficiencies with am-
bient air as the working gas.
In Table 4 the measured and calculated mean ion charger
mobilities, mobility equivalent diameters, masses and ion
mobility ratios are listed. For comparison, the values found
by Reischl et al. (1996) are also listed. The results were
used to calculate the charge distribution with Fuchs theory
as shown in Fig. 7. Negatively charged particles in the size
range from 4 to 12 nm by 241Am or X-Ray bipolar diffusion
chargers agree well with the parameters derived by Reischl
et al. (1996) and an ion mobility ratio of 1. For positively
charged particles, the charging efficiency is below the mea-
surement results for particles between 4 and 10 nm. By cor-
recting the charge distribution with the parameters derived
by Reischl et al. (1996), with an ion mobility ratio of 0.8,
the negatively charged particles with a size below 4 nm fit
the theory perfectly. The measurement results of this work
reveal an increased charging efficiency for both polarities, as
shown in Fig. 7. For mobility equivalent diameters between
4 and 12 nm and positive polarity, the charging efficiency fits
the theory for 241Am, X-Ray and the plasma torch, with air
as the working gas. This is in contrast to negatively charged
particles for which the results of the plasma torch with ni-
trogen or air as the working gas above 7 nm are higher and
below 7 nm are lower than expected by the theory. Also, for
241Am, X-Ray and the plasma charger with helium the the-
ory exceeds the measured charging efficiency. By correcting
the theory with the acquired ion mobility ratio, a good agree-
ment between theory and measurements can be found for
negatively charged particles above 7 nm and for positively
charged particles for the plasma torch with nitrogen as the
working gas. Although the effect for diameters >7 nm can
be explained, there is still a deviation for the smaller diame-
ters from theory. The reported discrepancy can therefore not
solely be attributed to the ion mobilities. There are other ef-
fects which should by investigated in further studies, espe-
cially the charging effects below 5nm which cause devia-
tions from the charging model.
Figure 8 depicts the recorded negatively charged particle
number size distribution averaged over numerous measure-
ments. The inversion of the size distribution data was per-
formed according to Petters (2018). These diagrams permit
a qualitative descriptive comparison of the different charging
devices. The plot reveals a shift of about 1.3nm in the maxi-
mum of the recorded size distribution between the X-Ray and
the plasma charger. In this study we assume the resulting de-
viation in size distribution is two-fold. Firstly, contamination
of the X-Ray charger from previous experiments with ammo-
nium sulfate leads to an increase of about 0.7 nm in particle
diameter for the observed bipolar diffusion charger (Steiner
and Reischl, 2012). Secondly, the application of a unsuitable
Figure 8. The plot represents the same recorded negative Ag parti-
cle number size distribution with a UCPC, depending on the mobil-
ity diameter for the plasma torch (N2), X-Ray and americium bipo-
lar diffusion chargers. Furthermore, the shift of the size distribution
caused by the application of a unsuitable charging efficiency (Torch
(N2)) for the plasma torch and the measured charging efficiency
(Torch (N2)*) and due to contamination of the X-Ray charger are
shown.
charge distribution for the plasma charger leads to a decrease
of the measured particle diameter of about 0.5 nm. By ap-
plying the measured charge distribution for the plasma torch
with N2as the working gas prior to data inversion, the devia-
tion in size vanishes and it is comparable in particle diameter
with the measured size distribution of the 241Am bipolar dif-
fusion charger (see Fig. 8 (Torch (N2)*)).
In addition, a significantly higher peak (about 50 %) with
the plasma torch was recorded which is most likely due to the
higher charging efficiency. Since the bipolar diffusion charg-
ers were rotated periodically in multiple cycles, the possibil-
ity of systematic uncertainties in the actual size distribution
was minimized. Therefore, the raised signal of the plasma
torch can be attributed to a generally higher charging effi-
ciency. The X-Ray charger is slightly less efficient than the
radioactive 241Am charger but still within the uncertainty
range. This decrease can be attributed to the performance re-
duction during continuous operation which typically occurs
during long measurement cycles. Compared to conventional
chargers the plasma torch proves to charge slightly better
with air as the working gas and less efficient with helium.
With nitrogen as the working gas, the plasma torch charges
up to 50 % more than with air and helium and more than the
other tested bipolar diffusion chargers. According to Maißer
et al. (2015), nitric acid has an anomalously high gas-phase
acidity for its mass and can persist in the gas phase in higher
concentrations than other low mass species. By using helium
as the working gas the concentration of nitrate ions in the gas
phase is lower than in air or N2, and therefore charge trans-
port decreases. This is in contrast to using N2as the working
Atmos. Meas. Tech., 13, 5993–6006, 2020 https://doi.org/10.5194/amt-13-5993-2020
C. Tauber et al.: Characterization of a non-thermal plasma charger 6003
Figure 9. Measured charging efficiencies for the different aerosol chargers and aerosol flow rates for negatively charged Ag particles with
mobility diameters of 12, 6.9 and 4.1 nm. The dotted black line represents the theoretical charging efficiency according to Wiedensohler
(1988) for the three different mobility diameters.
gas, for which an increased charging efficiency up to 50%
was measured.
Figure 9 shows the dependence of the charging efficiency
for different aerosol flow rates and particle sizes. The charg-
ing efficiencies for particles in the sub-50 nm regime show a
significant dependence on the aerosol flow rate. The different
bipolar diffusion chargers have proven to be more sensitive
to varying flow rates and a reduced residence time in the ion-
izing atmosphere (He and Dhaniyala, 2014; Kallinger et al.,
2012; Kallinger and Szymanski, 2015).
Figure 9 reveals that the aerosol charging is most effi-
cient for a flow rate of 2.5 L/Min, and the charging effi-
ciency decreases for higher flow rates. Kallinger and Szy-
manski (2015) and Jiang et al. (2014) also measured the
flow rate dependence of different chargers. In the study by
Kallinger and Szymanski (2015) an increased charging ef-
ficiency for the americium bipolar diffusion charger for a
flow rate of 5.0 L/Min was found. In addition, contrary to
our findings, a reduced charging performance for the X-Ray
bipolar diffusion charger was not observed by Kallinger and
Szymanski (2015) and Jiang et al. (2014). A reason for that
could be a reduced charging due to the low power output
of the X-Ray tube. Since the last repair and calibration of
the analyzed TSI 3088 neutralizer, the operating runtime was
about 371 h. Furthermore, in this work, we used a different
aerosol generation method compared to the above-mentioned
studies, which could lead to different charging mechanisms.
Especially in the sub-10 nm size range different chemical–
physical interactions might lead to unforeseen results which
should be investigated in future studies. The plasma torch
also achieves the highest charging efficiencies for lower flow
rates but seems to be not as sensitive to the aerosol flow com-
pared to the other devices. Especially air and nitrogen have
proven to be the most robust options as working gases.
In addition to the flow-dependent charging efficiency mea-
surements, the ozone concentration was recorded with an
O3monitor (Thermo Scientific Fischer, Model 49i). Elevated
ozone concentration was observed at lower flow rates and for
air as well as helium as the working gas. In the case of air, a
high amount of oxygen is present in the working gas of the
plasma torch, which supports ozone production. For helium
the afterglow of the plasma torch and the corresponding UV
light emission could be responsible for the increased amount
of ozone. In addition, the electromagnetic field applied can
cause a split of O2molecules, especially when the residence
time is increased at low working gas flow rates. All recorded
measurements can be found in the Supplement (Table S1).
4 Conclusions
The presented measurements conducted with a non-thermal
plasma source have shown that helium, nitrogen and air as
working gases lead to the same ion species. According to the
mobility and mass spectrometric measurements, the compar-
ison of the plasma charger with the americium bipolar diffu-
https://doi.org/10.5194/amt-13-5993-2020 Atmos. Meas. Tech., 13, 5993–6006, 2020
6004 C. Tauber et al.: Characterization of a non-thermal plasma charger
sion charger indicates the same negative ion species, whereas
for the positive ions, the measurements reveal a slight devia-
tion. At this point it should be noted that the chemical com-
position of the charger ions is affected by the tubing mate-
rial and contaminations as discussed by Steiner and Reischl
(2012).
The analyzed chemical composition of the bipolar diffu-
sion charger ions did not lead to changes in chemical compo-
sition, even with increased ozone concentration caused by
the plasma torch. By switching the working gas to nitro-
gen an increased charging efficiency could be recorded for
negatively charged particles compared to the 241Am bipolar
diffusion charger. In accordance with Mathon et al. (2017),
the ozone concentration can be reduced to ambient condi-
tions with nitrogen which is beneficial for commercial use.
For future studies, the influence of the variation of the oper-
ational settings and the resulting ozone concentrations of the
plasma torch remains to be investigated. The option of setting
high and low ozone concentrations is of interest when analyz-
ing the chemistry of different particles, for example proteins
(Kotiaho et al., 2000). In addition, the results would also be
useful for the application of corona dischargers, which pro-
duce ozone as well.
The higher charging probabilities for negatively charged
particles in the size range from 7 to 12 nm can be attributed
to differences in the electrical mobility. According to our
measurements, the ratio of ion mobilities, given by the ion
mobility of positively charged particles divided by the ion
mobilities of negatively charged particles, yields a constant
value of 0.66. Consequently, the ion mobilities for nega-
tively charged particles are higher on average. This increased
charging efficiency for negatively charged particles and a de-
creased charging efficiency for positively charged particles
were also measured by Wiedensohler and Fissan (1991) for a
85Kr bipolar diffusion charger in nitrogen. According to our
measurements, similar results could be found for the plasma
torch with nitrogen as the working gas. However, our results
reveal a strong deviation to classical charging theory in the
observed size range which has to be considered prior to data
inversion in future laboratory or field applications.
The charging efficiency of the non-thermal atmospheric
plasma source indicated a weak aerosol flow dependence
when operated with nitrogen or compressed air in compar-
ison to the americium and X-Ray bipolar diffusion charg-
ers. As a result, the application of the plasma charger for in-
creased flow rates in laboratory applications is promising.
In summary, with different experimental approaches we
were able to quantitatively characterize the Gilbert Mark I
plasma source with nitrogen, helium and air as working
gases. In addition, a commonly used X-Ray bipolar diffu-
sion charger and a radioactive americium bipolar diffusion
charger were analyzed for comparison. The highest charg-
ing efficiencies for negatively charged particles were found
for the Gilbert Mark I plasma charger with nitrogen as the
working gas. Our results also reveal the importance of well
characterized and clean bipolar diffusion chargers to avoid
any misinterpretation of experimental data, especially in the
sub-12 nm size range. In addition, contrary to ozone suppres-
sion, the plasma source revealed great potential to act as an
ozone generator by changing the working gas, for example,
to argon.
Data availability. Supplementary data associated with this article
can be found in the Supplement.
Supplement. The supplement related to this article is available on-
line at: https://doi.org/10.5194/amt-13-5993-2020-supplement.
Author contributions. CT designed the setup, CT and DS per-
formed the charging efficiency experiments, JG and DS performed
the OES measurements, CT and SB performed the mobility distri-
bution measurements, SB and DW performed the chemical compo-
sition measurements, CT, DS, JG, SB, PJW, DW and PMW were
involved in the scientific interpretation and discussion, and CT, DS,
JG, SB, PJW, DW and PMW wrote the manuscript.
Competing interests. The authors declare that they have no conflict
of interest.
Acknowledgements. The authors want to thank Peter Kallinger,
Gruenwald Laboratories GmbH and Grimm Aerosol Technik Ain-
ring GmbH & Co Kg for their support.
Financial support. This research has been supported by the Aus-
trian Research Promotion Agency (FFG) (grant no. 870121) and
the Austrian Science Fund (FWF) (grant no. J3951-N36).
Review statement. This paper was edited by Alfred Wiedensohler
and reviewed by two anonymous referees.
References
Adachi, M., Kousaka, Y., and Okuyama, K.: Unipolar and bipo-
lar diffusion charging of ultrafine aerosol particles, J. Aerosol
Sci., 16, 109–123, https://doi.org/10.1016/0021-8502(85)90079-
5, 1985.
Asbach, C., Kaminski, H., Lamboy, Y., Schneiderwind, U., Fierz,
M., and Todea, A. M.: Silicone sampling tubes can cause dras-
tic artifacts in measurements with aerosol instrumentation based
on unipolar diffusion charging, Aerosol Sci. Technol., 50, 1375–
1384, 2016.
Barmpounis, K., Ranjithkumar, A., Schmidt-Ott, A., Attoui, M., and
Biskos, G.: Enhancing the detection efficiency of condensation
Atmos. Meas. Tech., 13, 5993–6006, 2020 https://doi.org/10.5194/amt-13-5993-2020
C. Tauber et al.: Characterization of a non-thermal plasma charger 6005
particle counters for sub-2nm particles, J. Aerosol Sci., 117, 44–
53, https://doi.org/10.1016/j.jaerosci.2017.12.005, 2018.
Brilke, S., Resch, J., Leiminger, M., Steiner, G., Tauber, C., Wla-
sits, P. J., and Winkler, P. M.: Precision characterization of three
ultrafine condensation particle counters using singly charged
salt clusters in the 1–4 nm size range generated by a bipo-
lar electrospray source, Aerosol Sci. Technol., 54, 396–409,
https://doi.org/10.1080/02786826.2019.1708260, 2020.
Cooper, D. W. and Reist, P. C.: Neutralizing charged aerosols
with radioactive sources, J. Colloid Interf. Sci., 45, 17–26,
https://doi.org/10.1016/0021-9797(73)90239-7, 1973.
Deka, T., Boruah, A., Sharma, S. K., and Bailung, H.: Ob-
servation of self-excited dust acoustic wave in dusty plasma
with nanometer size dust grains, Phys. Plasmas, 24, 093706,
https://doi.org/10.1063/1.5001721, 2017.
Fernández de la Mora, J., and Barrios-Collado, C.: A bipolar
electrospray source of singly charged salt clusters of precisely
controlled composition, Aerosol Sci. Technol., 51, 778–786,
https://doi.org/10.1080/02786826.2017.1302070, 2017.
Flagan, R. C.: On Differential Mobility Analyzer
Resolution, Aerosol Sci. Technol., 30, 556–570,
https://doi.org/10.1080/027868299304417, 1999.
Fuchs, N. A., Daisley, R. E., Fuchs, M., Davies, C. N., and Strauma-
nis, M. E.: The Mechanics of Aerosols, Phys. Today, 18, 73 pp.,
https://doi.org/10.1063/1.3047354, 1965.
Gruenwald, J., Reynvaan, J., Eisenberg, T., and Geistlinger,
P.: Characterisation of a Simple Non-Thermal Atmo-
spheric Pressure Plasma Source for Biomedical Re-
search Applications, Contrib. Plasma Phys., 55, 337–346,
https://doi.org/10.1002/ctpp.201400059, 2015.
Harper, J. D., Charipar, N. A., Mulligan, C. C., Zhang, X., Cooks,
R. G., and Ouyang, Z.: Low-Temperature Plasma Probe for
Ambient Desorption Ionization, Anal. Chem., 80, 9097–9104,
https://doi.org/10.1021/ac801641a,. 2008.
He, M. and Dhaniyala, S.: Experimental characterization of
flowrate-dependent bipolar diffusion charging efficien-
cies of sub-50nm particles, J. Aerosol Sci., 76, 175–187,
https://doi.org/10.1016/j.jaerosci.2014.06.009, 2014.
Hoppel, W. A. and Frick, G. M.: Ion-Aerosol Attachment Coef-
ficients and the Steady-State Charge Distribution on Aerosols
in a Bipolar Ion Environment, Aerosol Sci. Technol., 5, 1–21,
https://doi.org/10.1080/02786828608959073, 1986.
Intra, P. and Yawootti, A.: An Experimental Investigation of
A Non-Mixing Type Corona-Needle Charger for Submi-
cron Aerosol Particles, J. Elect. Eng. Technol., 14, 1–8,
https://doi.org/10.1007/s42835-018-00011-x, 2019.
Jiang, J., Kim, C., Wang, X., Stolzenburg, M. R., Kaufman,
S. L., Qi, C., Sem, G. J., Sakurai, H., Hama, N., and
McMurry, P. H.: Aerosol Charge Fractions Downstream of
Six Bipolar Chargers: Effects of Ion Source, Source Ac-
tivity, and Flowrate, Aerosol Sci. Technol., 48, 1207–1216,
https://doi.org/10.1080/02786826.2014.976333, 2014.
Johnson, T. J., Nishida, R. T., Irwin, M., Symonds, J. P., Olfert,
J. S., and Boies, A. M.: Measuring the bipolar charge distribu-
tion of nanoparticles: Review of methodologies and development
using the Aerodynamic Aerosol Classifier, J. Aerosol Sci., 143,
105526, https://doi.org/10.1016/j.jaerosci.2020.105526, 2020.
Junninen, H., Ehn, M., Petäjä, T., Luosujärvi, L., Kotiaho, T., Kos-
tiainen, R., Rohner, U., Gonin, M., Fuhrer, K., Kulmala, M., and
Worsnop, D. R.: A high-resolution mass spectrometer to mea-
sure atmospheric ion composition, Atmos. Meas. Tech., 3, 1039–
1053, https://doi.org/10.5194/amt-3-1039-2010, 2010.
Kallinger, P. and Szymanski, W.: Experimental determination of
the steady-state charging probabilities and particle size conser-
vation in non-radioactive and radioactive bipolar aerosol charg-
ers in the size range of 5–40 nm, J. Nanopart. Res., 17, 171,
https://doi.org/10.1007/s11051-015-2981-x, 2015.
Kallinger, P., Steiner, G., and Szymanski, W.: Characteriza-
tion of four different bipolar charging devices for nanopar-
ticle charge conditioning, J. Nanopart. Res., 14, 944,
https://doi.org/10.1007/s11051-012-0944-z, 2012.
Kopnin, S. I., Morozova, T. I., and Popel, S. I.: Electron Beam Ac-
tion and High Charging of Dust Particles, IEEE Trans. Plasma
Sci., 46, 701–703, https://doi.org/10.1109/TPS.2017.2748378,
2018.
Kotiaho, T., Eberlin, M. N., Vainiotalo, P., and Kostiainen,
R.: Electrospray mass and tandem mass spectrometry iden-
tification of ozone oxidation products of amino acids and
small peptides, J. Am. Soc. Mass Spectr., 11, 526–535,
https://doi.org/10.1016/S1044-0305(00)00116-1, 2000.
Kramida, A., Ralchenko, Y., Reader, J., and NIST, N. A. T.: Atomic
spectra and ionization energies of the elements, available at:
https://physics.nist.gov/PhysRefData/ASD/ (last access: 15 Jan-
uary 2020), 2013.
Kurake, N., Tanaka, H., Ishikawa, K., Kondo, T., Sekine, M.,
Nakamura, K., Kajiyama, H., Kikkawa, F., Mizuno, M., and
Hori, M.: Cell survival of glioblastoma grown in medium
containing hydrogen peroxide and/or nitrite, or in plasma-
activated medium, Arch. Biochem. Biophys., special Issue: Low-
temperature plasma in biology and medicine, 605, 102–108,
https://doi.org/10.1016/j.abb.2016.01.011, 2016.
Leiminger, M., Feil, S., Mutschlechner, P., Ylisirniö, A., Gun-
sch, D., Fischer, L., Jordan, A., Schobesberger, S., Hansel, A.,
and Steiner, G.: Characterisation of the transfer of cluster ions
through an atmospheric pressure interface time-of-flight mass
spectrometer with hexapole ion guides, Atmos. Meas. Tech., 12,
5231–5246, https://doi.org/10.5194/amt-12-5231-2019, 2019.
Leppä, J., Mui, W., Grantz, A. M., and Flagan, R. C.:
Charge distribution uncertainty in differential mobility anal-
ysis of aerosols, Aerosol Sci. Technol., 51, 1168–1189,
https://doi.org/10.1080/02786826.2017.1341039, 2017.
Liu, B. Y. and Pui, D. Y.: Electrical neutralization of aerosols,
J. Aerosol Sci., 5, 465–472, https://doi.org/10.1016/0021-
8502(74)90086-X, 1974.
Maißer, A., Thomas, J. M., Larriba-Andaluz, C., He, S., and
Hogan, C. J.: The mass–mobility distributions of ions pro-
duced by a Po-210 source in air, J. Aerosol Sci., 90, 36–50,
https://doi.org/10.1016/j.jaerosci.2015.08.004, 2015.
Manninen, H. E., Franchin, A., Schobesberger, S., Hirsikko, A.,
Hakala, J., Skromulis, A., Kangasluoma, J., Ehn, M., Junninen,
H., Mirme, A., Mirme, S., Sipilä, M., Petäjä, T., Worsnop, D. R.,
and Kulmala, M.: Characterisation of corona-generated ions used
in a Neutral cluster and Air Ion Spectrometer (NAIS), Atmos.
Meas. Tech., 4, 2767–2776, https://doi.org/10.5194/amt-4-2767-
2011, 2011.
Mathon, R., Jidenko, N., and Borra, J.-P.: Ozone-free post-DBD
aerosol bipolar diffusion charger: Evaluation as neutralizer for
SMPS size distribution measurements, Aerosol Sci. Technol.,
https://doi.org/10.5194/amt-13-5993-2020 Atmos. Meas. Tech., 13, 5993–6006, 2020
6006 C. Tauber et al.: Characterization of a non-thermal plasma charger
51, 282–291, https://doi.org/10.1080/02786826.2016.1265082,
2017.
Michau, A., Arnas, C., Lombardi, G., Bonnin, X., and Hassouni, K.:
Nanoparticle formation and dusty plasma effects in DC sputter-
ing discharge with graphite cathode, Plasma Sources Sci. T., 25,
015019, https://doi.org/10.1088/0963-0252/25/1/015019, 2016.
Petters, M. D.: A language to simplify computation of differential
mobility analyzer response functions, Aerosol Sci. Technol., 52,
1437–1451, https://doi.org/10.1080/02786826.2018.1530724,
2018.
Reischl, G., Mäkelä, J., Karch, R., and Necid, J.: Bipolar
charging of ultrafine particles in the size range below 10
nm, J. Aerosol Sci., fuchs Memorial Issue, 27, 931–949,
https://doi.org/10.1016/0021-8502(96)00026-2, 1996.
Spencer, S. E., Tyler, C. A., Tolocka, M. P., and Glish, G. L.: Low-
Temperature Plasma Ionization-Mass Spectrometry for the Anal-
ysis of Compounds in Organic Aerosol Particles, Anal. Chem.,
87, 2249–2254, https://doi.org/10.1021/ac5038889, 2015.
Steiner, G. and Reischl, G. P.: The effect of carrier gas
contaminants on the charging probability of aerosols un-
der bipolar charging conditions, J. Aerosol Sci., 54, 21–31,
https://doi.org/10.1016/j.jaerosci.2012.07.008, 2012.
Steiner, G., Attoui, M., Wimmer, D., and Reischl, G. P.: A
Medium Flow, High-Resolution Vienna DMA Running in
Recirculating Mode, Aerosol Sci. Technol., 44, 308–315,
https://doi.org/10.1080/02786821003636763, 2010.
Tauber, C., Brilke, S., Wlasits, P. J., Bauer, P. S., Köberl, G., Steiner,
G., and Winkler, P. M.: Humidity effects on the detection of
soluble and insoluble nanoparticles in butanol operated conden-
sation particle counters, Atmos. Meas. Tech., 12, 3659–3671,
https://doi.org/10.5194/amt-12-3659-2019, 2019a.
Tauber, C., Steiner, G., and Winkler, P. M.: Counting effi-
ciency determination from quantitative intercomparison
between expansion and laminar flow type condensa-
tion particle counter, Aerosol Sci. Technol., 53, 344–354,
https://doi.org/10.1080/02786826.2019.1568382, 2019b.
Thomas, J. M., Chen, X., Maißer, A., and Hogan, C. J.:
Differential heat and mass transfer rate influences on the
activation efficiency of laminar flow condensation parti-
cle counters, Int. J. Heat Mass Transf., 127, 740–750,
https://doi.org/10.1016/j.ijheatmasstransfer.2018.07.002, 2018.
Tigges, L., Wiedensohler, A., Weinhold, K., Gandhi, J.,
and Schmid, H.-J.: Bipolar charge distribution of a soft
X-ray diffusion charger, J. Aerosol Sci., 90, 77–86,
https://doi.org/10.1016/j.jaerosci.2015.07.002, 2015.
Uner, N. B. and Thimsen, E.: In-Flight Size Focusing of Aerosols by
a Low Temperature Plasma, The J. Phys. Chem. C, 121, 12936–
12944, https://doi.org/10.1021/acs.jpcc.7b03572, 2017.
Wang, S. C. and Flagan, R. C.: Scanning Electrical Mo-
bility Spectrometer, Aerosol Sci. Technol., 13, 230–240,
https://doi.org/10.1080/02786829008959441, 1990.
Wiedensohler, A.: An approximation of the bipolar charge distribu-
tion for particles in the submicron size range, J. Aerosol Sci., 19,
387–389, https://doi.org/10.1016/0021-8502(88)90278-9, 1988.
Wiedensohler, A. and Fissan, H. J.: Bipolar Charge Dis-
tributions of Aerosol Particles in High-Purity Argon
and Nitrogen, Aerosol Sci. Technol., 14, 358–364,
https://doi.org/10.1080/02786829108959498, 1991.
Wiedensohler, A., Lütkemeier, E., Feldpausch, M., and
Helsper, C.: Investigation of the bipolar charge distribution
at various gas conditions, J. Aerosol Sci., 17, 413–416,
https://doi.org/10.1016/0021-8502(86)90118-7, 1986.
Winkler, P. M., Steiner, G., Vrtala, A., Vehkamäki, H., Noppel, M.,
Lehtinen, K. E. J., Reischl, G. P., Wagner, P. E., and Kulmala, M.:
Heterogeneous Nucleation Experiments Bridging the Scale from
Molecular Ion Clusters to Nanoparticles, Science, 319, 1374–
1377, https://doi.org/10.1126/science.1149034, 2008.
Winklmayr, W., Reischl, G. P., Lindner, A., and Berner, A.: A new
electromobility spectrometer for the measurement of aerosol size
distributions in the size range from 1 to 1000 nm, J. Aerosol Sci.,
22, 289–296, https://doi.org/10.1016/S0021-8502(05)80007-2,
1991.
Yang, W., Zhu, R., and Ma, B.: Repetitively Pulsed Dis-
charges Ignited in Microchannels Between Two Nonequally
Broad Planar Electrodes and Their Charging for Nanoscale
Aerosol Particles, IEEE Trans. Plasma Sci., 44, 944–949,
https://doi.org/10.1109/TPS.2016.2560223, 2016.
Yaroshenko, V., Meier, P., Lühr, H., and Motschmann, U.:
Physical Processes in the Dusty Plasma of the Enceladus
Plume, 241–262, Springer International Publishing, Cham,
https://doi.org/10.1007/978-3-319-64292-5_9, 2018.
Atmos. Meas. Tech., 13, 5993–6006, 2020 https://doi.org/10.5194/amt-13-5993-2020
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