Small Deflection Energy Analyzer for Energy and Angular Distributions
The development of the Small
Deflection Energy Analyzer (SDEA)
charged-particle spectrometer for energy
and angle distributions responds to a longstanding
need to measure the wind velocity
vector in Earth’s thermosphere, and to
obtain the ion-drift vector in the ionosphere.
The air and ions above 120 km are
endowed with bulk velocities and temperatures
just like air near the ground, but
with separate spatial and temporal variations.
It is important to understand these
not only for study of the physics and chemistry
of the Sun-Earth connection, but also
for spacecraft orbit predictions, and communications
through the ionosphere. The SDEA consists of a pair of parallel
conducting plates separated by a small
distance, with an entrance slit on one
end, and an exit slit on the other. A voltage
applied to these plates develops an electric field between the plates, and this
field deflects ions passing through it. If
an ion has too little energy, it will strike
one of the plates. If it has too much, it
will strike the back wall. An ion with the
amount of energy being searched for
will have its trajectory bent just enough
to exit the back slit.
The SDEA units are compact, rectangular,
and operate with low voltages. The
units can be built up into small arrays.
These arrays could be used either to
widen the field of view or to sharpen an
existing one. This approach can also be
used to obtain angular distributions in
two planes simultaneously, thus cutting
down the ion source power requirements
in half. This geometry has
enabled a new mass-spectrometer concept
that can provide miniaturized mass
spectrometers for use in industrial
plants, air-pollution monitoring, and
This work was done by Federico A. Herrero
of Goddard Space Flight Center. For further
information, contact the Goddard Innovative
Partnerships Office at (301) 286-5810. GSC-15610-1
This week’s Question: The Department of Energy (DOE) has set a goal of building a battery that stores energy for less than $100 per kilowatt-hour, making stored wind and solar energy competitive with energy produced from traditional power plants....
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