1. Outgassing of Outer Tracker Glue Maarten Buffing (VU) June 5 2009

2. Ageing of the Outer Tracker (OT) Irradiation of OT modules with weak β and γ sources reduces signal response → Ageing Caused by the glue Only at moderate intensity Possible methods against ageing Warming-up the modules to 40°C Flushing HV training

3. -Used glue: Araldite AY 103-1 -Glue combined with the hardener HY 991 -Silica gel is added to enhance viscosity 168 F-modules and 96 S-modules In a single F-module approximately 500 g of glue is used. Glue in the OT

4. 1. Several glues were tested for outgassing 2. Gas composition has been analyzed. Araldite AY 103 was qualified as non-outgassing

5. Outgassing results of Capeans Outgassing method The sample is heated to 125°C by conduction and radiation for 24 hours. Total mass loss (TML) is determined. Low outgassing if TML<1% and CVCM < 0.1% EpoxyOutgasEffect in detector Araldite AY 103 (Hardener HY 991) Trabond 2115 Araldite AW 106 (Hardener HV 935 U) NO YES NO YES Gas analysis results Outgassing of AW 106 contains pollutants as butane, hexane, trimethylpentane and trimethylbutane.

6. Our outgassing setup High vacuum (< 10 -8 mbar)

7. Properties of the setup Both pumps consists of: a three stage diaphragm pump (MD-4 Vario SP) - create a fore vacuum pressure of 1 mbar a turbomolecular pump (TMU 071 P) - creates a high vacuum of <10 -8 mbar Pumping speed:60, 60 l/s Effective pumping speed S eff :39, 35 l/s S eff of the combined pumps: 70 l/s -The pumping speed can be used to calculate the outgassing under known pressure -The entire setup can be heated Lower-, upper pump

8. Quadrupole Mass Spectrometer Electrons ionise gas molecules Electric quadrupole field selects molecules with specific m/z Signal is amplified by a channeltron

9. “Outgassing” of glue under atmospheric conditions

10. Outgassing in vacuum EpoxyDecrease in weight T(°C)Duration (days) Araldite AY 103-1 Araldite AW 106 Trabond 2115 0,35% 0,36% 0,71% 0,90% 40 25 40 14 4 10 Outgassing of Araldite AY 103-1 Under atmospheric conditions weight of glue sample increases. In vacuum weight decreases. Heating the sample accelerates its weight loss. Out of the vacuum weight increases again. Weight increase because of absorption → Water?

11. Araldite AY 103-1 Araldite AW 106 Trabond 2115

12. Outgassing of AY 103-1 Mass spectra of AY 103-1 before (blue) and after (red) heating Water is most abundant component

13. Zero-spectrum can be resolved for the most abundant background components Spectrum contains water, hydrogen, nitrogen, ethane, oxygen, CO 2 and methane Further analysis (1)

14. Further analysis (2) Can (known) components of the glue be identified in the spectra? What is the effect of heating the glue? Complications: - precise composition glue unknown - glue consists of many components - reference spectra can not be used quantitatively - reference spectra of some components are unknown

15. Relation between partial pressure of water and the measured current Backup: partial pressure of water