3.1.2. Comparison before and after bake-out
Fig. 5 shows the sample no. 5, which was cleaned with the procedure B (cp. 2.4). The mass spectra before and after a bake-out sequence (3.5 h at 150 ◦C) are shown. Clearly the improved residual spectrum and cleaning effect is visible.
3.1.3. Comparison of different cleaning procedures
A comparison of the outgassing of samples with applied different cleaning procedures after the PT mentioned in Section 2.4 has shown no essential influence of the cleaning procedures. All surfaces could sufficiently be cleaned with cleaner and cloth. The cryo blasting can improve the results, but the surfaces may become wet
due to condensation of humidity after extensive surface cooling by the cryo blasting. The samples have to be dried afterwards.
3.2. Mass spectra at higher temperatures
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 ofthe 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.