Gary Poon // Prather Laboratory // UCSD
Aircraft
ATOFMS Development Project //
We recently finished construction of the Aircraft ATOFMS and
collected our first spectrum. The
version shown in the pictures is a laboratory test mule and has not been
optimized for duty on an aircraft.
See below for a description of the project.
Picture 1. Roomy lab
based rack. The instrument itself
will easily fit into a single standard 19” rack with electronics occupying a
second rack.
Picture 2. The sampling interface is a domed ball joint design with
spherical alignment and variable aerodynamic lens parameters such as
lens-skimmer distance, number of turbomolecular pumps, and lens stages. The mass spectrometer (box with red
wires) is a dual polarity zaxon design with 490 mm overall length.
Project overview //
The
goal of this project is not only to extend the aerosol time-of-flight mass
spectrometry (ATOFMS) technique to free troposphere real-time measurements but
also to significantly improve the sensitivity and mass spectral resolution of
the current instrument. By
coupling aerodynamic size and mass spectral information, the chemical
composition of individual atmospheric particles as a function of size can be
determined. The aircraft
instrument is capable of making the same measurements as the traditional
instrument, but with higher sensitivity and a broader mass range which will
allow us to probe higher molecular weight species and thus further investigate
microorganisms and such air-sea exchange processes. The new aircraft ATOFMS will be used in future studies in
developing nations including India, Mexico City, and China to continue to
understand the variability of aerosol chemistry on a global scale. Ultimately, we will map out how the
size resolved mixing state changes on a global scale, comparing and contrasting
marine, urban, and rural environments.
We are currently working with modelers to develop key scientific
questions to explore in future field and laboratory campaigns.
The
instrument is nearing completion and will be field tested on the ground at the
SOAR 2005 Riverside campaign which involves 9 PI’s and numerous on-line
techniques. The current prototype
features a dual polarity zaxon-configuration mass spectrometer that is only 490
mm X 290 mm X 105 mm but can detect 100% of the ions up to m/z 2000, has twice
the resolution of the original ATOFMS, extended mass range, and will be able
the acquire spectra at up to 50 Hz. This will provide a tremendous amount of
data and allow rapid temporal snapshots to be acquired while flying through
clouds. Subsequently, the
instrument will be optimized for aircraft duty and be flight tested in February
2006 pending funding. Further
developments include an integrated aerodynamic lens inlet and light scattering
region further reducing the size and weight of these components by 80%. The overall instrument will be
1⁄4 the weight and 1⁄2 the volume of the original instrument
enabling duty on small aircraft.
By coupling the developed instrument with a cloud condensation nuclei
(CCN) instrument, the Prather group will directly measure the composition of
particles that activate cloud foramtion versus those that do not. This will directly yield insight into
the more poorly understood area of climate change referred to as the indirect
effect which relates to how effectively a particle can form a cloud
droplet.
Aircraft ATOFMS Development Team //
UCSD //
Principal
Investigator: Professor Kim Prather
Design Engineer:
Joseph Mayer
Postdoctoral
Researcher: Gary Poon
Graduate Students:
John Holecek, Ryan Moffet, Kerri Denkenberger
Undergraduates:
Rene Sanchez, Jessie Charrier
Project Scientist:
Thomas Rebotier
TOFWERK AG //
Marc Gonin
Katrin Fuhrer