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
| Parameters | |
| Temperature | Between -150 °C and + 800 °C, also thermal cycles |
| Vacuum | < 10-4 Pa |
| Specimens | Max. 30 g, various geometry |
| Temperature control | By irradiation exchange |
| Accuracy of weighing | Vacuum balance drift: <5.10-7 g/h |
walter.costin@ait.ac.at