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Model 2000
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(Flight Unit)
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VODKA
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VACUUM
OUTGASSING/DEPOSITION
KINETICS APPARATUS
VODKATM
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Predicts:
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Outgassing and
Deposition Kinetics at selected source temperatures and selected
surface temperatures.
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Certifies:
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Source materials
(samples) have acceptable TMLs and CVCMs. (ASTM E595).
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Measures:
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TML, CVCM and
QTGA.
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Every Space
Materials Engineer, Surface Physicist, Spacecraft Contamination
Engineer and Spacecraft Contamination Effects Analyst looking at outgas
testing as a means of meeting the new enhancement to the ASTM E-595
standard test method, known as the ASTM E-1559 test, will undoubtedly
be interested to hear about the Vacuum Outgassing/Deposition Kinetics
Apparatus, with the acronym "VODKA", designed to meet the new
standard in it's entirety.
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The essential
components of the VODKA are QCM sensors and an effusion cell, in which
you can heat any material (eg. adhesives and sealants, cable insulation
and shrink tubing, conformal coatings, electrical components,
electrical shields, films and sheet materials, foams, grease,
lubricants, liquids, lacing tape and cord cable ties, laminates and
circuit boards, paint, ink, lacquers and varnishes, potting compounds,
pre-molded rubbers, elastomers, molding compounds and tapes), and
measure its outgassing constituents and rate in a high-vacuum
chamber.
The VODKA Chamber itself features oil-free pumping with
turbopumps and is shielded with LN2 cooled plates. Through
the use of a host computer, operation of the chamber is made almost
completely programmable. Prepared materials are subjected to
environmental temperatures ranging from 293° to 425°K in an effusion
cell. Three (or more) CQCMs, set at various distinct temperatures
(ranging from 90° to 400°K, for collecting the mass evolved), are
placed at 150 mm distance from the cell. Interlock chamber loading of
the effusion cell makes the process of changing the source material
possible without having to bring the main chamber up to atmospheric
pressure (and temperature). The chamber and its various components
operate by means of pneumatics. The QCMs and the effusion cell are
under the control of a Model 2000 Controller. A mass spectrometer
(1-1000 AMU, for RGA) and UV lamps (Krypton, for polemerization of
outgassed products) are available as options.
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Materials
Outgassing
- Prepared materials are
subjected to environmental temperatures in the effusion cell
- Effusion cell
temperatures range from 293°K to 425°K.
The VODKA makes use of a very small CQCM model. With the
case held at 293°K and using the internal heater, the crystals may be
raised to 400°K with a heat dissipation of only 0.75 watts. The
advantage to this is that you can now do QCM Thermogravimetric Analysis
(QTGA) to get condensation information. This unit has a Silicon Diode
for sensing the crystal temperature and a hybrid chip residing inside.
It has a dynamic range of greater than 8.39 x 10-4 grams.
Either 10 or 15 MHz versions are available. The resolution is ~4x10-2
ng/cm2-s.
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TML Measurements
Typical Total Mass Loss
and Outgassing Rate measurement QCM at 90°K and at a given material
source temperature.
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Total Mass Loss
(TML):
The prepared material total mass loss at a set source
temperature is deposited by known molecular flux onto the coldest
(90°K) QCM. The QCM responds to the collecting mass as a frequency
shift with test time. This shift can be related to the mass loss
percentage and by differentiation, the evaporation rate.
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CVCM Measurements
Typical Collected
Volatile Mass Loss given by QCM at various temperatures.
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Collected
Volatile Condensable Materials (CVCM):
Setting the temperature of the collecting QCMs
individually, the volatile materials portion that is condensable at
each receiver temperature can be measured by the QCMs.
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You can
determine, with various parameters, the TLM (Total Mass Loss), and CVCM
(Collected Volatile Condensable Materials) of a subject material with
known source temperatures that are equivalent to the temperatures that
exist on the spacecraft and various receiver temperatures equivalent to
the temperatures existing on a solar panel or some part of a radiator
on the spacecraft. You can even include the more subtle manipulations
of the spacecraft as it turns into or away from the sun and receives
solar thermal radiation on its panels and you can measure the
transmission or the reevaporation of the subject gasses. If your
interest involves the polymerization of outgassed products or the
effects of UV on subject surfaces, you will be interested in the
optional Krypton lamps.
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QTGA Measurements
The QCM Model 2000
Controller enables the heating rate to be set.
QCM frequency can be read to 0.01 Hz.
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QCM
Thermogravimetric Analysis (QTGA):
QCMs can be used to identify the molecular species with the
VODKA. Use of an in-situ heater in each QCM allows the reevaporation of
the deposited mass sequentially with the temperature, and thus the
identification from vapor-pressure characteristics.
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One of the most
important attributes of the VODKA is the ability to do QTGA, that is,
QCM Thermal Gravimetric Analysis. Collecting the emitted gasses on
quartz crystal microbalances (QCMs) at various temperatures gives a
real-time picture of the nature of the constituents. After receiving
all of the collected mass on the QCM from the subject material, you can
then analyze the deposit by two methods; either with a mass
spectrometer accompanied by heating the QCM at a known rate, or by
heating the QCM (at a specific rate) and at the same time measuring the
frequency change resulting from the removal or re-evaporation of the
deposited layer. Then integrating the frequency gives the rate of
change, resulting in spikes at specific partial fractionalization
points. From these results you can determine the outgassing rate of the
molecular constituents of the subject material with temperature, which
is a great thing to have knowledge about on a subject material that may
outgas for years in an environment virtually impossible to get to.
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Further
identification of the evaporating molecular species can be attained by
using the Mass Spectrometer and measuring the evolving mass spectrum over
a selected m/e scan range (1-1000 amu) and the ion count for each m/e
value in this range.
The mass spectrometer controller will provide full scan and
time programmed selected ion monitoring modes, variable dwell times,
total and selected ion chromatograms, mass spectra and spectrum
averaging, background subtraction, mass/intensity lists, X?Y axis scale
expansion, library search, and much more. This is a complete mass
spectrometer interface and communications controller package.
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The basic VODKA
Unit (Part Number 81-1562-01) includes the chamber and all necessary
support equipment and controllers, an effusion cell, three Mark 18
CQCMs, a Model 2000 Controller and Software. A mass spectrometer
(1-1000 AMU, for RGA) and UV lamps (Krypton, for polymerization of
outgassed products) are available as options.
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QCM Research
42232
Rio Nedo, Suite A
Temecula,
California 92590
Phone:
951.694.9539
FAX: 951.694.9538
E-Mail:
information@qcmresearch.com
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