Thermal Vacuum Test II

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Sublimation and redeposition under vacuum : Thermal Vacuum Test II

Test II is used in extension to ECSS-Q-70-02A (SeeThermal Vacuum Test I)

The Thermal Vacuum Test II, with high sensitivity, is used for a detailed investigation of the mass transport of materials (mass-loss due to sublimation, evaporation, outgassing as well as redeposition of evaporated particles) under thermal vacuum. Since a vacuum microbalance records mass changes on-line, this test is used in extension to the screening test ECSS-Q-70-02A (mass change by weighing in air before and after vacuum exposure).

Mass loss by sublimation, outgassing, evaporation and the mass gained by redeposition are measured by weighing (ESTEC-standard) in an apparatus built according to the ESTEC-design.

Smallest mass changes can be determined and accelerated tests can be carried out. By on-line mass spectroscopy the species of the outgassing or evaporated particles can be analysed. For surface conditioning a sputter-ion-gun can be used. For evaporation a Knudsen-cell is built in, recondensation on any susbtrates can be measured using the microbalance. Calibration of impingement rate is done using a quarz crystal microbalance. If necessary associated examinations (e.g. LO and Scanning-Electron Microscopy, IR-Spectroscopy, Auger-Spectroscopy) can be made.

"Sublimation Test Facility": microbalance (top), thermal vacuum chamber, mass spectrometer (left)

Thermal Vacuum Test II characteristics

On-line Measurement of:

• Mass-loss as a function of time and temperature
• Mass-gain as a function of substrate, time and temperature
• Mass spectroscopy of outgassing and evaporating particles