After the PT well cleaned samples, which do not outgas at room
temperature, show a different behavior at increased temperature.
Already at 40 ◦ C these samples start to outgas strongly. This effect
continues with a further increase of the temperature. Nevertheless,
after 3–4 h of bake-out at 150 ◦ C the pollutions have disappeared,
even at samples with normally unacceptable PT indications like at
the sample nos. 7 and 8. Even so the temperature of the samples did
not reach 150 ◦ C applied to the chamber wall, the cleaning process
was sufficient. Fig. 6 shows the mass spectra of the sample no. 7 at
a temperature of the vacuum chamber of 150 ◦ C immediately after
the achievement of this temperature and after 4 h baking-out at
150 ◦ C.